Morphological Characters Analysis, the Intergroup Phylogenetic Relationships and Possible Outgroups of the Family Sphaeriidae (Mollusca, Bivalvia)

Morphological Characters Analysis, the Intergroup Phylogenetic Relationships and Possible Outgroups of the Family Sphaeriidae (Mollusca, Bivalvia)

Scenaria of the morphological characters transformations in freshwater molluscs traditionally included in the family Sphaeriidae are studied; they are based on the phylogenetic analysis of 69 characters in 57 taxa.

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Дата:2002
Автор: Korniushin, A.V.
Формат: Стаття
Мова:English
Опубліковано: Інститут зоології ім. І.І. Шмальгаузена НАН України 2002
Назва видання:Вестник зоологии
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Цитувати:Morphological Characters Analysis, the Intergroup Phylogenetic Relationships and Possible Outgroups of the Family Sphaeriidae (Mollusca, Bivalvia) / A.V. Korniushin // Вестник зоологии. — 2002. — Т. 36, № 4. — С. 3–22. — Бібліогр.: 36 назв. — англ.

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Digital Library of Periodicals of National Academy of Sciences of Ukraine
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spelling irk-123456789-648872014-06-22T03:02:07Z Morphological Characters Analysis, the Intergroup Phylogenetic Relationships and Possible Outgroups of the Family Sphaeriidae (Mollusca, Bivalvia) Korniushin, A.V. Scenaria of the morphological characters transformations in freshwater molluscs traditionally included in the family Sphaeriidae are studied; they are based on the phylogenetic analysis of 69 characters in 57 taxa. Рассмотрены сценарии эволюционных преобразований морфологических признаков пресноводных моллюсков, традиционно включаемых в семейство Sphaeriidae, основанные на результатах филогенетического анализа 69 признаков в 57 таксонах. 2002 Article Morphological Characters Analysis, the Intergroup Phylogenetic Relationships and Possible Outgroups of the Family Sphaeriidae (Mollusca, Bivalvia) / A.V. Korniushin // Вестник зоологии. — 2002. — Т. 36, № 4. — С. 3–22. — Бібліогр.: 36 назв. — англ. 0084-5604 http://dspace.nbuv.gov.ua/handle/123456789/64887 594.1:591.4 en Вестник зоологии Інститут зоології ім. І.І. Шмальгаузена НАН України
institution Digital Library of Periodicals of National Academy of Sciences of Ukraine
collection DSpace DC
language English
description Scenaria of the morphological characters transformations in freshwater molluscs traditionally included in the family Sphaeriidae are studied; they are based on the phylogenetic analysis of 69 characters in 57 taxa.
format Article
author Korniushin, A.V.
spellingShingle Korniushin, A.V.
Morphological Characters Analysis, the Intergroup Phylogenetic Relationships and Possible Outgroups of the Family Sphaeriidae (Mollusca, Bivalvia)
Вестник зоологии
author_facet Korniushin, A.V.
author_sort Korniushin, A.V.
title Morphological Characters Analysis, the Intergroup Phylogenetic Relationships and Possible Outgroups of the Family Sphaeriidae (Mollusca, Bivalvia)
title_short Morphological Characters Analysis, the Intergroup Phylogenetic Relationships and Possible Outgroups of the Family Sphaeriidae (Mollusca, Bivalvia)
title_full Morphological Characters Analysis, the Intergroup Phylogenetic Relationships and Possible Outgroups of the Family Sphaeriidae (Mollusca, Bivalvia)
title_fullStr Morphological Characters Analysis, the Intergroup Phylogenetic Relationships and Possible Outgroups of the Family Sphaeriidae (Mollusca, Bivalvia)
title_full_unstemmed Morphological Characters Analysis, the Intergroup Phylogenetic Relationships and Possible Outgroups of the Family Sphaeriidae (Mollusca, Bivalvia)
title_sort morphological characters analysis, the intergroup phylogenetic relationships and possible outgroups of the family sphaeriidae (mollusca, bivalvia)
publisher Інститут зоології ім. І.І. Шмальгаузена НАН України
publishDate 2002
url http://dspace.nbuv.gov.ua/handle/123456789/64887
citation_txt Morphological Characters Analysis, the Intergroup Phylogenetic Relationships and Possible Outgroups of the Family Sphaeriidae (Mollusca, Bivalvia) / A.V. Korniushin // Вестник зоологии. — 2002. — Т. 36, № 4. — С. 3–22. — Бібліогр.: 36 назв. — англ.
series Вестник зоологии
work_keys_str_mv AT korniushinav morphologicalcharactersanalysistheintergroupphylogeneticrelationshipsandpossibleoutgroupsofthefamilysphaeriidaemolluscabivalvia
first_indexed 2025-07-05T15:27:10Z
last_indexed 2025-07-05T15:27:10Z
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fulltext Vestnik zoologii, 36(4): 3—22, 2002 © A. V. Korniushin, 2002 Ôàóíà è ñèòåìàòèêà UDC 594.1:591.4 MORPHOLOGICAL CHARACTERS ANALYSIS, THE INTERGROUP PHYLOGENETIC RELATIONSHIPS AND POSSIBLE OUTGROUPS OF THE FAMILY SPHAERIIDAE (MOLLUSCA, BIVALVIA) A. V. Korniushin Schmalhausen Institute of Zoology, vul. B. Khmelnits’kogo, 15, Kyiv-30, MSP, 01601 Ukraine Accepted 5 February 2002 Morphological Characters Analysis, the Intergroup Phylogenetic Relationships and Possible Outgroups of the Family Sphaeriidae (Mollusca, Bivalvia). Korniushin A. V. – Scenaria of the morphological charac- ters transformations in freshwater molluscs traditionally included in the family Sphaeriidae are studied; they are based on the phylogenetic analysis of 69 characters in 57 taxa. It is shown, that the whole group is distinguished by synapomorphies in mantle musculature, as well as by presence of complicated nephridia with many apomorphic features. At the same time, many organs and structures (hinge, liga- ment, siphons, gills and stomach) demostrate signs of reduction. Two traditionally recognized subfami- lies (Euperinae and Sphaeriinae), sometimes treated as families, differ in their reproductive strate- gies (ovoviviparity and viviparity); monophyletic status of the groups characterized by sequencial and synchronous brooding (Sphaerium s. l. and Pisidium s. l.) is also very probable. Some terminal clades correspond to the earlier suggested genera and subgenera, and relationships between them are briefly discussed. Apomorphies of mantle musculature characterizing Sphaeriidae were found also in Poly- mesoda (Geloina) – a taxon traditionally placed in Corbiculidae (one of the outgroups), suggested as a possible ancestor of the studied freshwater bivalves. Key wo r d s: Bivalvia, Sphaeriidae, Corbiculidae, Geloina, morphological characters, phylogenetic analysis. Àíàëèç ìîðôîëîãè÷åñêèõ ïðèçíàêîâ, âíóòðèãðóïïîâûå ôèëîãåíåòè÷åñêèå îòíîøåíèÿ è âîçìîæíûå âíåøíèå ãðóïïû ñåìåéñòâà Sphaeriidae (Mollusca, Bivalvia). Êîðíþøèí À. Â. – Ðàññìîòðåíû ñöå- íàðèè ýâîëþöèîííûõ ïðåîáðàçîâàíèé ìîðôîëîãè÷åñêèõ ïðèçíàêîâ ïðåñíîâîäíûõ ìîëëþñêîâ, òðàäèöèîííî âêëþ÷àåìûõ â ñåìåéñòâî Sphaeriidae, îñíîâàííûå íà ðåçóëüòàòàõ ôèëîãåíåòè÷å- ñêîãî àíàëèçà 69 ïðèçíàêîâ â 57 òàêñîíàõ. Ïîêàçàíî, ÷òî ãðóïïà â öåëîì õàðàêòåðèçóåòñÿ ñè- íàïîìîðôèÿìè â ñòðîåíèè ìàíòèéíîé ìóñêóëàòóðû, à òàêæå íàëè÷èåì ñëîæíî óñòðîåííûõ íåôðèäèåâ.  òî æå âðåìÿ ìíîãèå îðãàíû è ñòðóêòóðû (çàìîê, ëèãàìåíò, ñèôîíû, æàáðû è æå- ëóäîê) äåìîíñòðèðóþò ÷åðòû ðåäóêöèè. Äâà òðàäèöèîííî âûäåëÿåìûõ ïîäñåìåéñòâà (Euperinae è Sphaeriinae), èíîãäà ðàññìàòðèâàåìûõ â ðàíãå ñåìåéñòâ, õàðàêòåðèçóþòñÿ ðàçëè÷íûìè ðåïðî- äóêòèâíûìè ñòðàòåãèÿìè (ÿéöåæèâîðîæäåíèå è æèâîðîæäåíèå); ìîíîôèëèÿ ãðóïï, õàðàêòåðè- çóþùèõñÿ ïîñëåäîâàòåëüíîé èëè îäíîâðåìåííîé èíêóáàöèåé ìîëîäè (Sphaerium s. l. è Pisidium s. l.), òàêæå âåñüìà âåðîÿòíà. Ðÿä òåðìèíàëüíûõ êëàä ñîîòâåòñòâóþò ðàíåå ïðåäëîæåííûì ðî- äàì è ïîäðîäàì, êðàòêî îáñóæäàþòñÿ èõ ôèëîãåíåòè÷åñêèå îòíîøåíèÿ. Àïîìîðôíûå ÷åðòû ìàíòèéíîé ìóñêóëàòóðû, õàðàêòåðèçóþùèå Sphaeriidae, âûÿâëåíû òàêæå ó Polymesoda (Ge- loina) – òàêñîíà, òðàäèöèîííî îòíîñèìîãî ê ñåìåéñòâó Corbiculidae (îäíà èç âíåøíèõ ãðóïï), êîòîðûé, òàêèì îáðàçîì, ìîæåò áûòü ïðåäêîì àíàëèçèðóåìîé ãðóïïû. Êëþ÷åâûå ñ ëîâà: Bivalvia, Sphaeriidae, Corbiculidae, Geloina, ìîðôîëîãè÷åñêèå ïðèçíàêè, ôèëîãåíåòè÷åñêèé àíàëèç. Introduction The family Sphaeriidae is one of the major freshwater bivalve groups represented on all continents (Cox et al., 1969; Kuiper, 1983). Its total species diversity cannot be defined at this state of knowledge, because of descrepancies between taxonomic approaches accepted in different countries (see Korniushin, 1998a for re- view), ongoing revisions (Ituarte, 1996, 1999, 2000) and absence of modern reviews for many regions (e. g. Southeast Asia, New Guinea, Central and tropical South America, etc). However, according to our pre- liminary estimations based on the species-level taxonomy accepted by the majority of specialists worldwide, the total number of valid species is about 150 (tabl. 1). Most of the known sphaeriids are strictly freshwater and only several species tolerate slightly brackish water conditions in estuaries (Kuiper, Wolf, 1970). A. V. Korniushin 4 Because of the worldwide distribution, considerable diversity and deep specialization to the freshwater environment, the group is rather interesting for evolutionary studies. However its origin, relationships with other bivalve families and internal phylogenetic relationships are still poorly understood. Most of the modern reviewers (Burch, 1975; Kuiper, 1983; Mansur, Meier-Brook, 2000; Cooley, Ó Foighil, 2000 et al.) arrange Sphaeriidae in five genera: Eupera, Byssanodonta, Sphaerium, Musculium and Pisidium, but disagree about the number and names of subgenera. Some authors of the former USSR (Ali- mov, Starobogatov, 1968; Pirogov, Starobogatov, 1974; Stadnichenko, 1984; Starobogatov, Korniushin, 1986; Korniushin, 1996 a) divided Sphaerium and Pisidium into several genera. Accordingly, Sphaeriidae in its traditional understanding was divided into four families (Korniushin, 1992, 1996 a). However, such a splitting was criticized by the West European reviewers (Meier-Brook, 1993). Later on, Korniushin (1999, 2001) suggested a compromizing approach recognizing only those new taxa, which were supported by sets of reliable anatomical characters. There are also discrepancies between phylogenetic reconstructions based on different sets of characters. While the recent morphological studies confirmed monophyly of Pisidium s. l. (Korniushin, 1998 b) and sug- gested its sister relationship to Musculium (Mansur, Meier-Brook, 2000), molecular works (Park, Ó Foighil 2000; Cooley, Ó Foighil, 2000) showed more close affinity between Musculium and Sphaerium, and paraphyly of Pisidium. Traditionally, Sphaeriidae are considered closely related to the fresh- and brackish-water family Cor- biculidae, but Starobogatov (1992) suggested its direct origin from the primitive marine Astartidae. Neither of these hypotheses was confirmed by molecular study (Park, Ó Foighil, 2000) which showed Sphaeriidae to be an independent lineage without close relationship to any other studied marine or brackish water group. Notewor- thy, some of the rather diverse generic/ subgeneric taxa currently included in Corbiculidae (Cox et al., 1969) were not included in any molecular or morphological phylogenetic study, thus polyphyletic status of the latter family and affinity of some its subgroupings to Sphaeriidae cannot be excluded. Discrepancy between the phylogenetic reconstructions based on morphological and molecular charac- ters can be at least partly explained by the restricted number of characters and taxa available for a phyloge- netic analysis. In order to enlarge the morphological data set, Korniushin and Glaubrecht (in press) carried out an extensive search for the phylogenetically informative anatomical characters based on the data from published descriptions and original observations. As a result, the matrix including 69 characters and 57 taxa (54 species of Sphaeriidae, two corbiculids and a venerid) was compiled. This data set was tested then by PAUP (Swofford, 1998) under different assumptions. It appeared, that the consensus trees obtained without any constraints and by enforcement monophyly of the Sphaerium + Musculium (= Sphaerium s. l.) clade, as suggested by molecular works (Park, Ó Foighil, 2000; Cooley, Ó Foighil, 2000), differed in one step only; some taxonomic and biogeographic implications derived from the both analyses (with and without con- straints) were discussed (Korniushin, Glubrecht, in press). The aim of this paper is studying scenaria of the morphological characters transformations in Sphaerii- dae derived from the above mentioned analyses and comparing them to the existing classifications. We fo- cused on the key features of the groups well supported by the parsimony analysis (the whole family, its two basic partitions corresponding to the subfamilies Euperinae and Sphaeriinae, and the genus Pisidium in its traditional understanding), but transformations supporting some smaller terminal clades, viz. Amesoda, Sphaerinova, Neopisidium and some other are also discussed. We checked also some more outgroups for presence of advanced states characterizing Sphaeriidae, and a relationship between this family and Poly- mesoda (Geloina) – a taxon traditionally placed in Corbiculidae, is hypothesized. Material and methods This work is based on the morphological data matrix compiled by Korniushin & Glaubrecht (in press); the list of characters and states is provided in the Attachment 1. Additional material on Corbiculidae ob- tained from the Museum für Naturkunde (Berlin) included Polymesoda (Geloina) erosa (Solander, 1786) (ZMB 49532, Indian Ocean, no locality given, leg. M. Weber, undated, original identification – Cyrena Tab l e 1. Species diversity of Sphaeriidae in different regions Òàáëèöà 1. Âèäîâîå ðàçíîîáðàçèå ñôåðèèä â ðàçëè÷íûõ ðåãèîíàõ Region Number of species/endemics Sources Europe and Palearctic Asia 39/31 Korniushin, 1999, 2001 North America (native) 33/23 Burch, 1975 Africa (South of Sachara) and Madagascar 30/30 Kuiper, 1966 a; Mandahl-Barth, 1988, Korniushin, 1995 India and Nepal 11/10 Subba Rao, 1989; Nesemann et al., 2001 SE Asia and New Guinea 19/18 Odhner, 1940; Kuiper, 1983 Australia 16/15 Kuiper, 1983; Korniushin, 2000 New Zealand 3/3 Kuiper, 1966 b; Korniushin, Glushchenko, 1999 South America (Euperinae) 29/28 Mansur, Meier-Brook, 2000 South America (Sphaeriinae) 20/19 Kuiper, Hinz, 1984; Ituarte, 1996, 1999 Morphological Characters Analysis, the Intergroup Phylogenetic Relationships ... 5 suborbicularis) and Batissa violacea (Lamarck, 1797) (ZMB 103031, Angkona River, Sulawesi, Indonesia, leg. M. Glaubrecht, T. van Rhinthelen and F. Koehler 1999). Here we use traditional nomenclature of hinge teeth (Cox et al., 1969); anatomical therminology is based on our previous works (Korniushin, 2000, 2001). As already specified, there is no generally accepted system of Sphaeriidae. The taxa included in this phylogenetic analysis (see Attachment 2) were preliminarily arranged according to the latest versions of our system (Korniushin, 1999—2001), with some additions and modifications commented below. The genus Amesoda was restored by Alimov and Starobogatov (1968); Korniushin (2001) conservatively treated is as a subgenus of Sphaerium restricted to North America, but tentatively suggested close relationship of the Euro- pean species Sphaerium rivicola to this group; here we follow a compromizing view, recognizing Amesoda as a genus with two subgenera – North American Amesoda s. str. and European Rivicoliana. Subgenera of Sphaerium in its present (strict) understanding (Alimov, Starobogatov, 1968; Falkner et al., 2001) are not observed here. Herringtonium is traditionally included in Sphaerium as a monotypic subgenus (Burch, 1975), but Heard (1977) showed its intermediate position between Sphaerium and Musculium, while Starobogatov and Korniushin (1986) treated is as a separate genus. Sphaerinova and Paramusculium are tentatively assigned in this work to Musculium, as suggested by Korniushin (1998 c, 2000), but their generic rank may be also questioned (Korniushin, 1996). The status of Afromusculium is defined according to Korniushin (1998 c). The group comprizing all larger sphaeriids included by earlier authors into the genus Sphaerium (e. g. Amesoda, Sphaerium, Herringtonium and Musculium in the present understanding) is defined below as Sphaerium s. l., while the traditional genus Pisidium – as Pisidium s. l. Present division of the latter group into four genera is based on suggestions of Korniushin (1998 a, 1999). Taxonomic status of Euglesa was recently fixed by selecting a neotype for its type species Euglesa henslowiana Jenyns, 1832, the taxon is treated in some works as a subgenus of Pisidium (Korniushin, 2000; Falkner et al., 2001) and corresponds to the subgenus Cyclocalyx in the sense of modern North American reviewers (Burch, 1975). Most of the sub- generic groups assigned here to the genus Euglesa are treated as separate subgenera of Pisidium by Falkner et al. (2001). The genus Neopisidium in the broad understanding suggested by Korniushin (1999) cannot be accepted because of confusion about the type species (G. Falkner, pers. comm.), terefore the name is re- stricted here to “Pisidium conventus” species group (=Conventus auct.); all three groups of the so called “neotenic pisidia” (e. g. distinguished by reductions in many organs) are treated as separate genera, while the taxon traditionally defined as Pisidium moitessierianum is tentatively included in Odhneripisidium. Several species included until now in Pisidium (Burch, 1975; Korniushin, 1998 d, 2000; Nesemann et al., 2001), are assigned here to Euglesa on the base of their anatomical characters, but their subgeneric belonging is not defined. The status of Eupera and Byssanodonta is defined according to Mansur and Meier-Brook (2000). Maximum parsimony trees were obtained by PAUP* 4.0b4a (Swofford, 1998) on Macintosh Performa using the procedure of heuristic search with stepwise addition and tree-bisection-reconnection (TBR) algo- rithms. A venerid and two representatives of Corbiculidae were treated as outgroups. All characters were unordered and had equal weight; the delayed transformation option (DELTRAN) giving preference to paral- lelisms over reversions (Swofford, 1998) was used. The multi-state taxa were treated as polymorphic (option “mstaxa=polymorph”). Searching under topological constraints derived from the molecular studies (Park, Ó Foighil, 2000; Cooley, Ó Foighil, 2000) was also performed. Support values were obtained by a bootstrap analysis with 500 replicates (Swofford, 1998). The further study was focused on the clades with bootstrap support more than 50%. Noteworthy, some of these clades did not appear on the strict consensus trees. Reconstruction of character transformations given below is based on the apomorphy lists obtained in PAUP* (Swofford, 1998). Abbreviations, used in the figures: af – anterior fold of stomach; as – anal (exhalant) siphon; bo – branchial opening; bs – branchial (inhalant) siphon; c1, c3 – inner and outer cardinal teeth of right valve; c2, c4 – inner and outer cardinal teeth of left valve; co – coecum; id – inner demibranch; irm – inner radial mantle muscles; l – ligament; mg – midgut; od – outer demibranch; odd – descending lamella of outer demibranch; oe – oesophagus; ps – pedal slit; sr – integrated siphonal muscles; sr1 – retractors of anal siphon; sr2, sr3 – upper and lower retractors of branchial siphon; t1 – major typhlosole; t2 – minor typhlosole. Results Character transformations The most probable phylogenetic relationships on generic and subgeneric level de- rived from the results of the phylogenetic analysis carried out by Korniushin, Glau- brecht (in press) are provided in the figs 1, 2; synapomorphies supporting the most disputable clades are listed in the table 2. Below we observe the trends in evolution of different organs and structures, as suggested by these results. A. V. Korniushin 6 Shel l form. While both observed consensus trees (fig. 1, 2) showed that Eu- perinae retained the ancestral (anterior) position of umbo, the direction of evolution in the other subfamily remained unclear. In the tree obtained without constraints (fig. 1), the central position of umbo was supposed to be initial state in Sphaeriinae, while its posterior shift – a synapomorphy for Pisidium s. l. and the most advanced Musculium species (Sphaerinova, Afromusculium and several Musculium species with uncertain placement). However, inforcing monophyly of the Sphaerium + Musculium clade made the mentioned subgrouping of Musculium also monophyletic, by this condition it occu- pied basal position in Sphaerium s. l. ckade. Sculpture. Only the well recognizable patterns of sculpture were included in the data matrix; both analyses showed that the presence of prominent periostracum folds was a synapomorphy for Euperinae, while peculiar periumbonal striae distinguished the group bearing the name Cingulipisidium. Fig. 1. Phylogenetic relationships within Sphaeriidae on generic and subgeneric levels; cladogram based on the majority rule consensus of 752 mpt (length 154) obtained in the phylogenetic analysis without constraints (Korniushin, Glaubrecht, in press). Ðèñ. 1. Ôèëîãåíåòè÷åñêèå îòíîøåíèÿ â ñåìåéñòâå Sphaeriidae íà óðîâíå ðîäîâ è ïîäðîäîâ; êëàäîãðàì- ìà îñíîâàíà íà êîíñåíñóñå (ïðàâèëî áîëüøèíñòâà) 752 íàèáîëåå ýêîíîìíûõ äåðåâüåâ (äëèíà 154), ïîëó÷åííûõ â ôèëîãåíåòè÷åñêîì àíàëèçå áåç îãðàíè÷åíèé (Korniushin, Glaubrecht, in press). Morphological Characters Analysis, the Intergroup Phylogenetic Relationships ... 7 Hinge tee th (fig. 3). Results of our study show, that the common ancestor of sphaeriids had a hinge without the tooth c1, with a single bent or dome-like c2, single c3 (occasionally divided in c3a and c3b in Amesoda rivicola) and c4. This condition could derive from the typical veneroid hinge (c1, c3a and c3b in the right valve; c2a, c2b and c4 in the left one) by means of reduction. Hinge apparently suffered a further reduction – the lost of c4 – in Euperinae. The straight form of c2 (as in S. corneum, M. lacustre and E. subtruncata) is apparently an advanced state, which evolved inde- pendently in several clades within Sphaerium, Musculium and Euglesa. L igament . The outgroups selected for this analysis, as well as the majority of heterodont bivalves, are characterized by a parivincular ligament, which is supported by a peculiar projection of hinge plate – nympha. This condition is also shared by Tab l e 2. Synapomorphies, supporting the most important clades distinguished by the phylogenetic analysis in Sphaeriidae Òàáëèöà 2. Ñèíàïîìîðôèè, ïîääåðæèâàþùèå âàæíåéøèå êëàäû, âûäåëåííûå â õîäå ôèëîãåíåòè÷åñêîãî àíàëèçà ñåìåéñòâà Sphaeriidae Clade Synapomorphies Sphaeriidae 5.1; 6.1; 7.1; 17.1; 20.1**; 29.1; 37.1*; 41.1; 42.1; 47.1; 49.1; 51.1; 57.1 Euperinae (Eupera and Byssanodonta) 8.1; 11.1; 15.1; 16.1; 20.1*; 21.1; 23.1; 41.1**; 44.1; 66.1 Sphaeriinae (Sphaerium s. l and Pisidium s. l.) 1.1; 4.1**; 10.1**; 20.2*; 21.2; 24.1; 34.1; 35.2*; 36.1; 38.1**; 39.1; 40.1; 45.1**; 48.1**; 52.1; 54.1*; 55.1; 59.1; 60.2; 61.1*; 62.1; 67.1; 68.1* Musculium+Herringtonium+ Pisi- dium s. l. 48.1*; 69.0* Sphaerium s. l.** 35.2**; 61.1**; 68.1** Sphaerium+Amesoda** 48.0**; 69.1** Amesoda 4.0 (reversion)**; 28.0**; 38.0 (reversion)**; 45.0 (reversion)**; 56.1; 65.0** Sphaerium s. str. 41.0; 58.0 Musculium s. str.: M. lacustre and M. securis 2.1; 6.2 Sphaerinova s. l. **: M. incomitatum, M. argentinum, M. indicum, M. tas- manicum and M. novaezelandiae 19.1** Pisidium s. l. 14.1; 18.1; 32.1; 35.1**; 46.1; 50.1; 61.0 (reversion)*; 63.1; 68.0 (reversion)* Pisidium s. str.: P. amnicum and P. dubium 35.1*; 63.2; 64.1 Euglesa (Henslowiana): E. lilljeborgi, E. henslowana and E. supina 35.1; 54.1 Henslowiana + E. cara 26.1 E. (Casertiana): E. casertana, E. com- presa, E. keniana, E. viridaria, E. etheridgei, E. atkinsoniana 32.2 E. (Cingulipisidium): E. hibernica, E. langleyana, E. nitida, E. pseudo- sphaerium 12.1 (secondarily lost in E. pseudosphaerium); 26.1 E. (Cyclocalyx): E. obtusalis, E. ova- mpicum, E. milium, E. pulchella and E. subtruncata 27.1 E. pulchella and E. subtruncata (Pseudeupera) 27.2 „Neotenic“ pisidia (Neopisidium, Odhneripisidium and Afropisidium) 13.1; 31.1 “Neotenic pisidia” except Neopisidium conventus 6.1; 22.1; 56.2; 63.2; 64.2 (traditional subgenus Odhneripisidium supported by 3.1) No t e s . * – shown only in the trees obtained without constraints; ** – shown only in the trees obtained under condition of monophyly of Sphaerium s. l. clade; clades with bootstrap support more than 50% and unambiguous synapomorphies (in bold); characters and states numbers correspond to those in the Attach- ment 1. A. V. Korniushin 8 Euperinae and some taxa of Spheriinae, viz. Amesoda and M. hartmanni (fig. 4, A, B), but it is still not clear, whether the mentioned groups inherited this state from the common ancestor of the subfamily, or it was first lost and then restored (as sug- gests the analysis under constraints). In the majority of sphaeriids the nympha was re- duced, and a highly modified (introverted) ligament was developed in Odhneripisi- dium (fig. 4, C). Mant le edge and i t s muscula ture. While the outgroups have integrated si- phonal muscles (fig. 5, A), sphaeriids are distinguished in having separate retractors of exhalant and inhalant siphons (fig. 5, B—E). Both analyses show this feature as a syn- apomorphy of the family. Two subfamilies are characterized by different arrangements of lower muscles of the inhalant siphon: in Euperinae they are organized in several bundles, while in Sphaeriinae – in a single pair of retractors. Such characters as sepa- Fig. 2. Phylogenetic relationships within Sphaeriidae on generic and subgeneric levels; cladogram based on the majority rule consensus of 126 mpt (length 155) obtained in the phylogenetic analysis with enforced monophyly of the clade characterized by sequencial brooding (Sphaerium s. l.) (Korniushin, Glaubrecht, in press). Ðèñ. 2. Ôèëîãåíåòè÷åñêèå îòíîøåíèÿ â ñåìåéñòâå Sphaeriidae íà óðîâíå ðîäîâ è ïîäðîäîâ; êëàäîãðàì- ìà îñíîâàíà íà êîíñåíñóñå (ïðàâèëî áîëüøèíñòâà) 126 íàèáîëåå ýêîíîìíûõ äåðåâüåâ (äëèíà 155), ïîëó÷åííûõ â ôèëîãåíåòè÷åñêîì àíàëèçå ïðè óñëîâèè ìîíîôèëèè êëàäû, õàðàêòåðèçóþùåéñÿ ïîñëå- äîâàòåëüíîé èíêóáàöèåé ìîëîäè (Sphaerium s. l.) (Korniushin, Glaubrecht, in press). Morphological Characters Analysis, the Intergroup Phylogenetic Relationships ... 9 ration of siphons and peculiar mode of their contraction – with apical parts turning inside (Mansur, Meier-Brook, 2000) are also interpreted here as synapomorphies of Euperinae. Upper retractors of the inhalant siphon suffer some reduction in Sphaeri- nova (tabl. 2). Their complete reduction in Pisidium s. l. might be a consequence of the inhalant siphon reduction (species of this group may have only a simple branchial opening). Noteworthy, lower retractors of the inhalant siphon or their rudiments are distinguishable also in the species, wich have no branchial opening (fig. 5, E). Sphaeriids are also characterized by relatively short outer radial mantle muscles. Furthermore, arrangement of the inner radial muscles in bundles is shown to be a syn- apomorphy of Sphaeriinae (fig. 6). Orientation of these bundles is an important char- acter in Euglesa, since its advanced states support the clade Cyclocalyx including at least five species (tabl. 2). Elongation of the mantle fusion is shown to be an advanced feature which devel- oped independently in Euperinae and several clades within Pisidum s. l. Gi l l s. The main evolutionary trend in the studied group is the gradual reduction of the outer demibranch, indicated by its reduced size, shift in posterior direction, transition from two-lamellar to one-lamellar structure and delay in the ontogenetic development. According to our analyses, one-lamellar outer demibranch is an apomor- phy supporting the clade which includes all genera of Pisidium s. l. group except Lacustrina, and complete reduction of the outer demibranch took place once, defining a clade of “neotenic pisidia” (Neopisidium, Odhneripisidium and Afropisidium in the present understanding). In comparison with the outgroups, Sphaeriidae are character- ized by relatively short ascending lamella of the inner demibranch. Concerning development of the interlamellar septae, results of our analyses are controversial. Depending on the applied constraints, development of septae on each filament is shown as an initial state for all Sphaeriinae, or only for the Sphaerium s. l. clade. Consequently, peculiar arrangement of septae (on each second filament) characterizing some species of Pisidium s. l. can be iterpreted as an apomorphy supporting some its subgroupings (in the former case) or an ancestral state for the whole group. Al imentary sys tem. In comparison with the outgroups, labial palps of sphaeriids are characterized by somewhat reduced ridged area. Sphaeriinae are distin- guished by the angulate anterior edge of these palps (in the outgroups and Euperinae it is straight). Concluding from the earlier ivestigations (Mansur, Meier-Brook, 2000) and re- sults of this study, we assume that sphaeriid stomach is a reduced venerid one. The Fig. 3. Arrangement of cardinal teeth (diagrammatic): A – Veneridae and Corbiculidae, right valve; B – Ven- eridae and Corbiculidae, left valve; C – typical hinge of Sphaeriinae, right valve; D – typical hinge of Sphaeri- inae, left valve; E – Sphaeriinae with straight cardinal teeth (left valve); F – Euperinae (left valve). Ðèñ. 3. Ðàñïîëîæåíèå êàðäèíàëüíûõ çóáîâ (ñõåìàòèçèðîâàíî): A – Veneridae è Corbiculidae, ïðàâàÿ ñòâîðêà; B – Veneridae è Corbiculidae, ëåâàÿ ñòâîðêà; C – òèïè÷íûé çàìîê Sphaeriinae, ïðàâàÿ ñòâîðêà; D – òèïè÷íûé çàìîê Sphaeriinae, ëåâàÿ ñòâîðêà; E – Sphaeriinae ñ ïðÿìûìè êàðäèíàëüíûìè çóáàìè (ëåâàÿ ñòâîðêà); F – Euperinae (ëåâàÿ ñòâîðêà). A. V. Korniushin 10 most remarkable advanced feature is ab- sence of caeca containing winds of the major typhlosole, which are well seen in the outgroups. Two loops of the major typhlosole seen in larger sphaeriids can be treated as the rudiments of these caeca (fig. 7). Sphaeriinae are distinguished by the posterior extension of the stomach (its length exceeds height). Distribution of the other stomach characters (stomach separation, elevation of anterior fold, and course of the minor typhlosole) is controversial: each scenario include cases of reversion from advanced to primitive character states (tabl. 1). It concerns especially the group Amesoda, which is most similar in the stomach characters to Euperinae and the out- groups; these similarities can be inter- preted either as symplesiomorphies or reversions. Simplification of the midgut coil is shown in all our analyses as a synapo- morphy for Pisidium s. l. Nephr id ia. In contrast to the or- gans observed above, sphaeriid nephridia do not shw any trend for reduction. Moreover, they demonstrate progressive development within the family. Presence of such structures as long funnel, pericar- dial tube, dorsal lobe and excretory sac are apparently synapomorphies for the family. These complications may intensify osmoregulatory function which is very important in the freshwater environment. Anterior extension of the excretory sac is shown here as a synapomorphy of Sphaerium and narrow funnel – as a ten- tative synapomorphy for the Musculium + Herringtonium + Pisidium s. l. clade (in the analysis without constraints). Transformations of the type of nephridium (open/closed) apparently occured many times within the group. In all probability, the common an- cestor of Pisidium s. l. had closed nephridia – with pericardial portion not visible be- tween the branches of dorsal lobe (tabl. 2), but the ancestral state in the subfamily Sphaeriinae cannot be defined with certainty. Reproduct ive sys tem . All sphaeriids are brooders, but Euperinae produce large eggs with much yolk developing directly between gill lamellae (ovoviviparity), while Sphaeriinae develop small eggs nourished from the mother in brood pouches formed by inner demibranch filaments (transition to the true viviparity). These two modes evidently demonstrate different reproductive strategies of the two major sphaeriid subgroupings, which may be identified as ovoviviparity and transition to the true viviparity. Furthermore, the latter subfamily is characterized by a small gonad placed at the base of the foot and not extended dorsally. Fig. 4. Ligament: A – Amesoda rivicola (ligament with nympha); B – Musculium? hartmanni (ligament with nympha); C – Odhneripisidium tenuilineatum (introverted ligament). Ðèñ. 4. Ëèãàìåíò: A – Amesoda rivicola (ëèãàìåíò ñ íèìôîé); B – Musculium? hartmanni (ëèãàìåíò ñ íèìôîé); C – Odhneripisidium tenuilineatum (èí- òðîâåðòèðîâàííûé ëèãàìåíò). Morphological Characters Analysis, the Intergroup Phylogenetic Relationships ... 11 Fig. 5. Siphons and siphonal musculature (diagrammatic): A – Neocorbicula; B – Eupera; C – Sphaerium, Musculium and Herringtonium; D – Lacustrina, Pisidium s. str. and Euglesa; E – Odhneripisidium and Afropis- idium. Ðèñ. 5. Ñèôîíû è ñèôîíàëüíàÿ ìóñêóëàòóðà (ñõåìàòèçèðîâàíî): A – Neocorbicula; B – Eupera; C – Sphaerium, Musculium è Herringtonium; D – Lacustrina, Pisidium s. str. è Euglesa; E – Odhneripisidium è Afropisidium. Fig. 6. Musculature of mantle edge (diagrammatic): A – Corbicula; B – Eupera; C – Amesoda; D – majority of Sphaeriinae. Scale bar 1 mm. Ðèñ. 6. Ìóñêóëàòóðà ìàíòèéíîãî êðàÿ (ñõåìàòèçèðîâàíî): A – Corbicula; B – Eupera; C – Amesoda; D – áîëüøèíñòâî Sphaeriinae. Ìàñøòàáíàÿ ëèíåéêà 1 ìì. A. V. Korniushin 12 From this study we still cannot decide, whether sequential or asynchronous brooding (when many broods on different stages of development are found in one animal) is a synapomorphy for Sphaerium s. l. clade, or a plesiomorphic feature in Sphaeriinae, since the evidence for the latter scenario is still very tentative (difference in one step only). Sequential brooding in Neocorbicula reported by Ituarte (1994) is apparently a result of parallel evolution. Position of the brood pouch proved to be an informative character within Pisidium s. l.: peculiar states of this character found in Pisidium s. str. (brood pouch occupies major part of the inner demibranch even on initial stages of its development), and Od- neripisidium + Afropisidium clade (brood pouch placed near the dorsal edge of the gill) are interpreted here as apomorphies. The whole group is also characterized by enlarged number of filaments involved in formation of the brood pouch. Larva l deve lopment. Different taxa of sphaeriids may release their larvae on different stages of development defined by the structure of their gills. The longest incu- Fig. 7. Stomach characters (diagrammatic): A – Chamelea gallina; B – Corbicula fluminea; C – Eupera plat- ensis; D – Amesoda striatina; E – Amesoda similis; F – Sphaerium corneum; G – Pisidium amnicum; H – Euglesa supina (A—D, F—G – view from right side; E, H – internal view of dissectted stomach). Ðèñ. 7. Ñòðîåíèå æåäóäêà (ñõåìàòèçèðîâàíî): A – Chamelea gallina; B – Corbicula fluminea; C – Eupera platensis; D – Amesoda striatina; E – Amesoda similis; F – Sphaerium corneum; G – Pisidium amnicum; H – Euglesa supina (A—D, F—G – âèä ñïðàâà; E, H – âñêðûòûé æåëóäîê èçíóòðè). Morphological Characters Analysis, the Intergroup Phylogenetic Relationships ... 13 bation takes place in Sphaerium s. str. and Amesoda, which newborn are released on the most advanced stages characterized by presence of the 2nd lamella in outer demibranchs (fig. 8). This condition may be in- terpreted as an ititial state in Sphaeriinae, or advanced character supporting its terminal clade, depending on our assumptions concerning relationships of Sphaerium, Musculium and Pisidium. Released larvae of Musculium and Herringtonium have only one outer demibranch lamella. The young of Eupera is released before ap- pearance of the outer demibranch as such, repetition of this feature in Pisidium s. l. may be iterpreted as a symplesiomorphy or a reversion. This review of characters transformations in the family Sphaeriidae shows, that the data of different analyses are controversial and many aspects of evolu- tion within this group are still not clear. However, evo- lutionary trends characterizing the whole family and its two basic partitions (subfamilies) could be defined with more certainty. Among these trends, reductions involv- ing many organs and structures (hinge, ligament, si- phons, gills and stomach) are the most remarkable. In general, such reductions are consistent with the dimi- nution of size, but it could not be the only cause of reduction. For example, Pisidium s. str. is quite com- parable in size to many species of Sphaerium and Mus- culium, but has many common features with much smaller species of Euglesa: reduced exhalant siphon with simplified musculature, one lamellar outer demibranch, shortened coil of midgut and pericardial tube of nephridium; it is even more advanced in its profound reduction of the outer demibranch indicated by its great posterior shift (tabl. 2). On the other hand, such organs as siphonal and mantle edge musculature, nephridia and brood pouches were subject of progressive development and became more complicated and specialized in the course of evolution. Apparently, some of these transformations, namely development of the coiled nephridium and brood pouches for incubation of young were crucial for the group, determining its success in freshwater environments whith their hypoosmotic conditions and strong water currents. Factors which triggered transformation of the siphonal musculature are still not clear. The subfamily Euperinae is in many characters (e. g. ligament, labial palps and stom- ach) more primitive than Sphaeriinae. At the same time, two subfamilies show quite different adaptations in such structures as siphons, mantle edge and nephridium, as well as in the reproductive characters. Taxonomic implications The above analysis shows that the whole family Sphaeriidae and its two traditional subfamilies (Euperinae and Sphaeriinae) are well supported clades. Monophyly of some preliminarily defined taxa of Sphaeriinae, such as Amesoda, Sphaerium s. str., Musculium s. str., Sphaerinova, Pisidium s. str., Henslowiana, Cingulipisidium, Pseudeu- pera and Odhneripisidium (excluding O. moitessierianum) is also confirmed, but not all of these taxa have good bootstrap support. On the other hand, Musculium s. l., Euglesa and Afropisidium were shown to be paraphyletic or polyphyletic. Outstdanding position of Herringtonium is also shown, and its closer relationship to Musculium than to Sphaerium is noteworthy. Sphaerinova and Paramusculium proved to be separate line- Fig. 8. Gills in released larvae: A – Musculium; B – Sphaerium s. str. Scale bar 1 mm. Ðèñ. 8. Æàáðû ó ìîëîäè: A – Musculium; B – Sphaerium s. str. Ìàñøòàáíàÿ ëèíåéêà 1 ìì. A. V. Korniushin 14 ages with uncertain relationships. Furthermore, close relationship of several Musculium species from tropical and southern temperate regions (M. incomitatum, M. argentinum and M. indicum) to Sphaerinova is shown by the search under constraint; if this rela- tionship is confirmed, the mentioned species may be included in Sphaerinova. Phylogenetic relationships of several species are tentatively defined by this study: E. cara is probably related to the group Henslowiana (shown only in the majority rule consensus), E. hibernica and E. langleyana – to Cingulipisidium, while E. obtusalis, E. ovampicum and E. milium – to Pseudeupera (the whole clade may bear the name Cyclocalyx). A group of species from different continents showed close affinity to E. casertana (tabl. 2; fig. 1, 2), the name Casertiana being available for this group. Re- lationships of E. globularis and E. personata are still not defined. All “neotenic” pisidia belonged to a single terminal clade in both our reconstruc- tions, with Neopisidium conventus in the basal position. Phylogenetic affinities and taxonomic status of Odhneripisidium? moitessierianum remain uncertain. Possible sister groups of Sphaeriidae Synapomorphies of the family Sphaeriidae, especially those which presume pro- gressive development of organs, can be used as key characters in a search for possible outgroups of Sphaeriidae. Brackish-water bivalves living in conditions of transition be- Fig. 9. Mantle musculature in Polymesoda (Geloina) erosa: A – siphonal muscles from inside; B – siphons, lateral view; C – mantle line near posterior adductor scar; D, E – mantle edge from outside (ruler in D 1 mm). Ðèñ. 9. Ìàíòèéíàÿ ìóñêóëàòóðà Polymesoda (Geloina) erosa: A – ñèôîíàëüíûå ìûøöû èçíóòðè; B – ñèôîíû ñáîêó; C – ìàíòèéíàÿ ëèíèÿ âáëèçè îòïå÷àòêà çàäíåãî àääóêòîðà; D, E – ìàíòèéíûé êðàé èçíóòðè (D: öåíà äåëåíèÿ 1 ìì). Morphological Characters Analysis, the Intergroup Phylogenetic Relationships ... 15 tween marine and freshwater habitats seem to be the most perspective in this aspect. As a first stage of this search, we checked some brackish water taxa traditionally as- signed to Corbiculidae but not included in any previous phylogenetic analysis, namely Polymesoda (Geloina) and Batissa. Since characters of the mantle musculature impor- tant, as shown above, for understanding phylogeny of the Sphaeriidae were not de- scribed by previous morphological studies of corbiculids (Morton, 1976, 1989), we fo- cused our examinations on these characters. According to our observations, P. (G.) erosa is characterized by a very peculiar ar- rangement of siphonal muscles: the muscles of branchial siphons are separated from those of the anal siphon, forming a pair of strong retractors (fig. 9, A—B). This ar- rangement can be interpreted as a first step in formation of the retractors system, char- acteristic to Sphaeriidae. Mutiplied lower siphonal muscles can be seen as well, and they are very similar to those of Eupera. Unusual arrangement of siphonal muscles is reflected also in the mantle line, which has no mantle sinus, but a narrow projection in postrior part (fig. 9, C). Musculature of the mantle edge of Geloina is also demonstrative, since the outer radial muscles are relatively short and the bundles of the inner radial muscles are prominent and attached well above the mantle line (fig. 9, D—E). This condition is rather similar to that observed in Sphaeriinae, but not in Euperinae. Organization of the mantle musculature in Batissa is similar to that observed in Corbicula: siphonal muscles are rather short and musculature of the inhalant siphon are not clearly distinguished from that of the exhalant siphon, lower muscles of the inha- lant siphon are not seen, outer radial mantle muscles are as long as the inner ones, the latter are organized in a band, not in separate bundles (fig. 10). Fig. 10. Mantle musculature in Batissa violacea: A – siphons and their muscles from inside; B – mantle edge from outside. Ðèñ. 10. Ìàíòèéíàÿ ìóñêóëàòóðà Batissa violacea: A – ñèôîíû è èõ ìóñêóëàòóðà èçíóòðè; B – ìàíòèé- íûé êðàé ñíàðóæè. A. V. Korniushin 16 Fixed material of the North American Polymesoda s. str. was not available for this study, however the course of the mantle line shows that its musculature is organised in the same way as in Neocorbicula, and differs from that of Corbicula and Batissa only in having deep mantle sinus. Thus, the family Corbiculidae appears to be rather heterogeneic in respect of its mantle musculature, with Polymesoda (Geloina) falling apart from the other taxa and demonstrating some similarity to the family Sphaeriidae. Noteworthy, Geloina is not distinguished from other corbiculids or venerids in the principal characters of hinge, ligament siphons and stomach (Morton, 1976, this study). Discussion Monophyletic status of the family Sphaeriidae and its two major subgroupings is in a good agreement with the previous morphological (Mansur, Meier-Brook, 2000) and molecular (Park, Ó Foighil, 2000) studies. However, the rank of these subgroup- ings is still disputable. Taking into account that synapomorphies of Euperinae and Sphaeriinae concern many organs and their reproductive systems demonstrate different strategies of adaptation to the freshwater environments (e. g. ovoviviparity and vivipar- ity), we cannot reject also those classifications, which recognize Euperinae and Sphaeriinae as separate families (Starobogatov, 1992). Reconstructions of relationships between the major partitions in Sphaeriinae (or Sphaeriidae in the strict sense suggested above) are still controversial. Since Pisidium s. l. clade is well supported by each morphological analysis (fig. 1,2), and the clade Sphaerium s. l. (Sphaerium + Musculium) well supported by molecular data (Park, Ó Foighil, 2000; Cooley, Ó Foighil, 2000) requires only one additional step in our analysis (fig. 2), monophyly of both clades seems very probable. Noteworthy, all char- acters supporting Pisidium s. l. are reductions, but synchronous repetition of reductions in several organs (mantle, gills, alimentary system and nephridium) seems to be im- probable. If the basic dichotomy of viviparous clams is confirmed by the further study (e. g. total evidence analysis), each of the partitions may obtain the rank of subfamily (Sphaeriinae and Pisidiinae respectively). The other major discrepancy between morphological and molecular reconstruc- tions need to be explained, namely position of Afropisidium, which is shown to be a sister clade to all remaining Sphaeriidae in the trees, based on 18S and 16S ribosomal DNA data (Park, Ó Foighil, 2000; Cooley, Ó Foighil, 2000). Probably, this taxon or the whole group Neopisidium s. l. (including Neopisidium s. str., Afropisidium and Odhneripisidium) is a basal clade for Pisidium, not a terminal one as shown by this study. Such a topology apparently needs fewer additional steps than assuming para- phyly of Pisidium s. l. (Korniushin, Glaubrecht, in press). Two circumstances should be mentioned in this respect. First of all, Afropisidium is distinguished from other Pis- idium s. l. by the external type of ligament. This type could not be coded unequivocally because of numerous transitions to the other types, but may indicate plesiomorphic condition and thus ancient origin of the group. Detailed examination of the ligament pit for presence of rudimentary nympha seems necessary. Furthermore, Afropisidium (as well as Odhneripisidium) demonstrate similarity to Eupera in configuration of nephridium. According to Mansur and Meier-Brook (2000), the lateral section of nephridium in Eupera is a part of the dorsal lobe, while similarly looking structure in observed in the above mentioned taxa and, partly, in Amesoda and Neopisidium conven- tus – as the lateral loop. Consequently, these structures were coded as different char- acters. However, characters of nephridium apparently need further investigation. Probably, the coding accepted here is not adequate to the homologies between differ- ent parts of this organ. Noteworthy, Euglesa is monophyletic either in the published molecular trees (Cooley, Ó Foighil, 2000), or in the recostructions obtained under constraint, fixing Neopisidium as a basal lineage of Pisidium s. l. Morphological Characters Analysis, the Intergroup Phylogenetic Relationships ... 17 In showing the trend for gill reduction, this study is in agreement with earlier re- views on gill development and evolution in sphaeriids (Korniushin, 1996 b). At the same time, monophyletic status of the group characterized by complete reduction of the outer demibranch (Neopisidium s. l.) contradicts to some earlier views (Kuiper, 1962; Korniushin, 1992, 1998 a). Spontaneous reduction of the outer demibranch was also reported for some species belonging to Euglesa, e. g. E. keniana (Kuiper, 1966 a; Piechocki, Korniushin, 1994), but later investigations have shown that some popula- tions of these species may have small rudiments of the outer demibranch (Korniushin, 1998 d), which never happens in Neopisidium species. Similar length of the trees with rather different topologies, obtained by our analy- ses can be explained by controversial distribution of character states. In particular, sev- eral taxa have peculiar combinations of primitive and advanced states, e. g. Amesoda is characterized by the primitive features of ligament (presense of nympha) and stomach (clear separation from the midgut), alongside specialized or advanced features of si- phonal musculture (long and strong retractors) and brood pouches (absense of com- partmentation). Since position of these groups on the phylogenetic tree is still not de- fined, they deserve a closer study. The cases of character reversions suggested by our analyses (e. g. concerning nympha, stomach and nephridia) also need a careful investi- gation. Probably, involving more characters and taxa may help to find more definite solutions of these puzzles. Resolving uncertainty about the nearest sister group of Sphaeriidae is also very important in a search for such solutions. Until more data for phylogenetic analyses are available, we consider premature any extensive taxonomic rearrangements. Discrepancies in characters of the mantle muscles found between different taxa of Corbiculidae make phylogenetic analysis of this group (either morphological or mo- lecular) rather urgent. Polymesoda (Geloina) should be included in such analyses and its subgeneric vs generic status, as well as monophyly of the whole family need to be tested. Despite rather simplified composition of hinge and structure of stomach charac- terizing Sphaeriidae, we consider improbable their direct origin from a primitve het- erodont group like Astartidae or Astartoidea, as suggested by Starobogatov (1992). Also molecular analysis shows, that Sphaeriidae belong to the clade of more advanced Ven- eroida including superfamilies Veneroidea, Mactroidea, and Tellinoidea, as well as freshwater families Corbiculidae and Dreissenidae (Park, Ó Foighil, 2000). However, Geloina may not be the only potential sister group of Sphaeriidae, therefore a broader phylogenetic analysis involving the characters defined here and including a selection of taxa from different heterodont superfamilies seem to meaningful. This study was supported by the research fellowship of the A. von Humboldt Foundation (1999—2000) and the DFG travel grant (2000). The major part of the work was done at the Museum für Naturkunde, Berlin, and the author is grateful to the Curator of Mollusca and Tentaculata of this museum Matthias Glaubrecht for providing materials and facilities, as well as for the permission to use some unpublished re- sults of the cooperative project. At t a chmen t 1. List of characters and states. For detailed description of characters see À. Korniushin, Ì. Glaubrecht (in press). Ïðèëîæåíèå 1. Ñïèñîê ïðèçíàêîâ è èõ ñîñòîÿíèé. Äåòàëüíîå îïèñàíèå ïðèçíàêîâ äàíî À. Êîðíþ- øèíûì, Ì. Ãëàóáðåõòîì (â ïå÷àòè). Shell 1. Position of umbo: 0 – anterior; 1 – central; 2 – posterior. 2. Caps (calyculi): 0 – absent; 1 – present. 3. Position of ligament: 0 – not introverted; 1 – introverted. 4. Nympha: 0 – present; 1 – absent. 5. Inner cardinal tooth of the right valve (c1): 0 – present; 1 – absent. 6. Inner cardinal tooth of the left valve (c2): 0 – divided into 2 parts; 1 – bent (arched); 2 – straight; 3 – absent. A. V. Korniushin 18 7. Outer cardinal of the right valve (c3): 0 – divided into 2 parts; 1 – not divided; 2 – absent. 8. Outer cardinal tooth of the left valve (c4): 0 – present; 1 – absent. 9. Lateral teeth: 0 – absent; 1 – present. 10. Folds of periostracum: 0 – present; 1 – absent. 11. Size of periostracum folds: 0 – not pronounced; 1 – pronounced. 12. Periumbonal striae: 0 – absent; 1 – present Mantle 13. Branchial mantle opening: 0 – present; 1 – absent. 14. Siphons: 0 – two siphons; 1 – only anal siphon. 15. Fusion of siphons: 0 – fused; 1 – free. 16. Contraction of siphons: 0 – without apical part turning inside; 1 – with apical part turning inside. 17. Retractors of the exhalant siphons: 0 – integrated with muscles of inhalant siphon; 1 – separated. 18. Upper muscles of the branchial siphon: 0 – present; 1 – absent. 19. Strength of the upper retractors of the branchial siphon: 0 – strong; 1 – weak. 20. Attachment of upper the muscles of branchial siphon: 0 – along the mantle line; 1 – tightly adjoining ad- ductor muscles (the scars are not separated); 2 – apart from posterior adductors (the scars are sepa- rated). 21. Arrangement of lower muscles of the branchial siphon: 0 – organised in broad muscle bands; 1 – form several paired bundles; 2 – form one pair of bundles. 22. Perisiphonal mantle fusion (suture): 0 – present; 1 – absent. 23. Length of perisiphonal suture: 0 – short; 1 – slightly elongate (about 1/5 the length of the pedal slit); 2 – markedly elongate (1/4 to 1/2 the length of the pedal slit). 24. Inner radial mantle muscles: 0 – dispersed; 1 – organised in bundles. 25. Bundles of inner radial muscles: 0 – strong; 1 – weak. 26. Differentiation of the mantle muscle bundles: 0 – bundles uniform; 1 – anterior bundles markedly bigger. 27. Orientation of mantle muscle bundles: 0 – perpendicular to the mantle margin; 1 – converging anteriorly; 2 – converging medially. 28. Number of muscle bundles: 0 – ten to fourteen; 1 – seven to nine; 2 – four to six. 29. Outer radial muscles: 0 – long; 1 – short. 30. Inner mantle fold: 0 – normally developed; 1 – poorly developed. Gills 31. Outer demibranch: 0 – present; 1 – absent. 32. Position of outer demibranch: 0 – before 6th filament; 1- at 7th to 10th filament; 2 – behind 11th filament. 33. Outer demibranch descending lamella: 0 – present; 1 – absent. 34. Inner demibranch ascending lamella: 0 – high; 1 – relatively low. 35. Interlamellar septae in the inner demibranch: 0 – developed on each 5th-7th filament; 1 – developed on each 2nd filament; 2 – developed on all filaments. Alimentary system 36. Anterior edge of the outer palps: 0 – straight; 1 – with a projecting angle. 37. Ridged area on palps: 0 – broad (covers the whole inner surface); 1 – narrow (covers about ½ of the inner surface). 38. Separation between the stomach and the midgut: 0 – present; 1 – absent. 39. Form of the stomach. States: 0 – stretched dorso-ventrally; 1 – stretched in posterior direction. 40. Sorting area on the stomach roof (SA3): 0 – broad; 1 – narrow. 41. Anterior fold: 0 – not elevated; 1 – elevated. 42. Caeca: 0 – present; 1 – absent. 43. Anteriorly directed branch of the right digestive gland duct: 0 – present; 1 – absent. 44. Course of the major typhlosole: 0 – with two loops; 1 – simple, without any loops. 45. Course of the minor typhlosole in the stomach: 0 – runs parallel to the major typhlosole; 1 – turns poste- riorly. 46. Coil of the intestine: 0 – complicated, with several loops; 1 – simple, with one loop. 47. Funnel: 0 – short; 1 – long. Nephridia 48. Form of the funnel: 0 – broad; 1 – narrow. 49. Pericardial tube: 0 – absent; 1 – present. 50. Course of the pericardial tube: 0 – with at least 3 loops; 1 – with only 2 loops. 51. Dorsal lobe: 0 – absent; 1 – present. 52. Splitting of the dorsal lobe: 0 – in three sections (branches); 1 – in two sections. 53. Form of the dorsal lobe: 0 – elongated (length more than width); 1 – square (length equal to width); 3 – broad (length less than width). 54. Position of the pericardial tube in relation to the dorsal lobe: 0 – covered by the dorsal lobe (closed nephridium); 1 – visible dorsally (open nephridium). 55. Anterior extension of the lateral loop: 0 – absent; 1 – present. Morphological Characters Analysis, the Intergroup Phylogenetic Relationships ... 19 56. Position of the anterior extension: 0 – completely covered by the dorsal lobe; 1 – partly covered by the dorsal lobe; 2 – open from the dorsal side. 57. Excretory sac: 0 – absent; 1 – present. 58. Form of excretory sac: 0 – not extended; 1 – extended anteriorly Reproductive system 59. Gonad: 0 – extending dorsally; 1 – not extending dorsally. 60. Nutrition of embryos: 0 – planktotrophic; 1 – lecithotrophic (ovo-viviparity); 2 – nutrition provided by the parental animal (eu-viviparity). 61. Simultaneous development of several broods (asynchronous brooding): 0 – absent; 1 – present. 62. Brood pouches: 0 – absent; 1 – present. 63. Number of filaments in the pouch: 0 – two to three; 1 – five to nine; 2 – more than ten. 64. Position of pouch: 0 – upper position; 1 – lower position; 2 – not localised. 65. Compartmentalisation of brood pouches: 0 – absent; 1 – present. 66. Byssus in adults: 0 – present; 1 – absent. Development 67. Velum: 0 – present, 1 – absent. 68. Outer demibranch in the released young: 0 – absent, 1 – present. 69. Second lamella of outer demibranch in the incubated larvae: 0 – absent, 1 – present. At t a chmen t 2. Preliminary classification of the studied taxa, with characteristics of their distribution (taxa with indefinite status marked with “?”, type species of genera and subgenera in bold). Ïðèëîæåíèå 2. Ïðåäâàðèòåëüíàÿ êëàññèôèêàöèÿèçó÷åííûõ òàêñîíîâ è õàðàêòåðèñòèêà èõ ðàñïðî- ñòðàíåíèÿ (òàêñîíû ñ íåîïðåäåëåííûì ñòàòóñîì îáîçíà÷åíû “?”, òèïîâûå âèäû ðîäîâ è ïîäðîäîâ âûäåëåíû øðèôòîì) Family Veneridae Chamelea gallina (Linne, 1758) – Atlantic and Mediterranean Family Corbiculidae Corbicula fluminea (Müller, 1774) – Oriental Neocorbicula limosa (Maton, 1809) – South American Family Sphaeriidae Subfamily Euperinae Genus Eupera Bourguignat, 1854 E. platensis Doello-Jurado, 1921 – South American Genus Byssanodonta Orbigny, 1846 B. paranensis Orbigny, 1835 – South American Subfamily Sphaeriinae Genus Amesoda Rafinesque, 1820 Subgenus Amesoda s. str. A. similis (Say, 1816) – North American A. striatina (Lamarck, 1818) – North American Subgenus Rivicoliana Servain, 1888 A. rivicola (Lamarck, 1818) – European Genus Sphaerium Scopoly, 1777 S. corneum (Linnaeus, 1758) – Palaearctic S. nucleus (Studer, 1820) – Palaearctic S. rhomboideum (Say, 1822) – North American S. nitidum Clessin in Westerlund, 1876 – Circum-boreal S. solidum (Normand, 1844) – European Genus? Herringtonium Clarke, 1973 H. occidentale (Prime, 1860) – North American Genus Musculium Link, 1807 Subgenus Musculium s. str. M. lacustre (Müller, 1774) – Holarctic M. securis (Prime, 1851) – North American Subgenus Paramusculium Alimov et Starobogatov, 1968 M. transversum (Say, 1829) – North American Subgenus Sphaerinova Iredale, 1843 M. tasmanicum (Tenison Woods, 1870) – Australian M. novaezelandiae (Deshayes, 1854 – New Zealand Subgenus Afromusculium Korniushin, 1998 M. incomitatum (Kuiper, 1966) – South African A. V. Korniushin 20 Species with uncertain subgeneric placement M. hartmanni (Jickeli, 1874) – African M. argentinum (Orbigny, 1835) – South American M. indicum (Deshayes, 1854) – Oriental (Indian) Genus Pisidium C. Pfeiffer, 1821 P. amnicum (Müller, 1774) – Palaearctic P. dubium (Say, 1816) – North American Genus Lacustrina Sterki, 1816 P. subtilestriatum Lindholm, 1909 – Euro-Siberian (Arctic) Genus Euglesa Jenyns, 1832 Subgenus Euglesa s. str. E. personata (Malm, 1855) – European E. casertana (Poli, 1791) – Holarctic? E. globularis Clessin in Westerlund, 1873 – Palearctic Subgenus Cyclocalyx Dall, 1903 E. obtusalis (Lamarck, 1818) – Palaearctic Subgenus Hiberneuglesa Starobogatov in Dolgin, 1983 E. hibernica (Westerlund, 1897) – European Subgenus Pseudeupera Germain, 1913 E. subtruncata (Malm, 1855) – Holarctic E. pulchella (Jenyns, 1832) – Palearctic Subgenus Henslowiana Fagot, 1792 E. henslowana (Sheppard, 1823) – Palearctic E. lilljeborgi (Clessin, 1886) – Holarctic (Boreal) E. supina A. Schmidt, 1851 – Euro-Siberian Subgenus Cingulipisidium Pirogov & Starobogatov, 1974 E. nitida (Jenyns, 1832) – Holarctic E. pseudosphaerium (Favre, 1927) – European Subgenus Tetragonocyclas Pirogov & Starobogatov, 1974 E. milium (Held, 1836) – Holarctic Species with uncertain subgeneric placement Euglesa langleyana (Melvill & Ponsonby, 1891) – South African E. ovampicum (Ancey, 1890) – South African E. viridaria (Kuiper, 1956) – African E. etheridgei (Smith, 1883) – Australian E. atkinsoniana (Theobald, 1876) – Oriental (Indian) E. compressa (Prime, 1851) – North American E. cara (Cotton, 1953) – Australian E. keniana (Preston, 1911) – African Genus? Neopisidium Odhner, 1821 N. conventus (Clessin, 1877) – Holarctic (Boreo-Alpine) Genus? Afropisidium Kuiper, 1962 A. pirothi (Jickeli, 1880) – African A. sterkianum (Pilsbry, 1897) – South American A. clarckeanum (G. & H. Nevill, 1871) – Oriental A. aslini (Kuiper, 1983) – Australian A. hodgkini (Suter, 1905) – New Zeland Genus? 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