A study of the anatomy ofPupaandMaxacteon(Acteonidae, Opisthobranchia), with an account of the breeding cycle ofPupa kirki

Morphological (including ultrastructural) and developmental characters utilized in recent literature are critically reviewed as the basis to reassess the phylogenetic relationships of gastropods. The purpose of this paper is to provide a framework of characters for future studies and a testable phylogenetic hypothesis. This is one of the fvst attempts to use such characters to assess the relationships of all major clades using parsimony methods. The analysis uses 1 17 characters and includes 40 taxa, predominantly 'prosobranchs'. Five outgroup taxa are included, representing four conchiferan groups and Polyplacophora. Of the 1 17 characters reviewed and included in the analyses, nine are shell characters (four of these are shell structure), two opercular, two muscular, four ctenidial, 12 renopericardial and 24 reproductive (including 17 based on sperm and spermatogenesis), 27 of the digestive system, 32 of the nervous system and sense organs; the remainder are developmental (3) and of the foot and hypobranchial gland. In the initial analysis the data set included a mixture of binary and multistate characters with all characters unordered. These data were also analysed after scaling so that each character had equal weight. A third data set was constructed in which all characters were coded as binary characters. These analyses resulted in some implausible character transformations, mainly involving the regaining of lost pallial structures. Additional analyses were run on all three sets of data after removing five characters showing the most unlikely transformations. These analyses resulted in generally similar topologies. The robustness of the clades was tested using clade decay. The adaptive radiation of gastropods and their life history traits are briefly described and discussed and the terminology for simultaneous heririaphroditism refined. A scenario for the evolution of torsion equated with the fossil record is proposed and the effects of torsion and coiling on gastropods are discussed along with asymmetry imposed by limpet-shaped body forms. It is suggested that the first gastropods were ultradextral. The idea that heterochrony has played a major part in gastropod evolution is developed and discussed, particularly the paedomorphic stamp imposed on thc apogastropods. The veliger larvae of caenogastropods and heterobranchs are contrasted and found to differ in many respects. The evolution of planktotrophy within gastropods is discussed. Recent phylogenetic hypotheses for gastropods based on molecular data are generally in broad agreement with the present results. On the basis of our analyses we discuss the major monophyletic groups within gastropods. Gastropods appear to be a nionophyletic clade, and divide into two primary groups, the Eogastropoda (incorporating the patellogastropods and their (probably sinistrally coiled) ancestors and the Orthogastropoda ~ the Correspondence to W.F. Ponder. GASTROPOD PHYLOGENE'remainder of the gastropods. Orthogastropoda comprises several well defined clades. The vetigastrop...

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“…Rudman, 197213;Brace, 1977b). The basommatophoran Chilina (Brace, 1983) has an extra ganglion in addition to the usual five.…”

Section: Parietal Gangliamentioning

confidence: 97%

Towards a phylogeny of gastropod molluscs: an analysis using morphological characters

Ponder

Lindberg

1997

Zoological Journal of the Linnean Society

526

301

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“…Architectonicoidea, Pyramidelloidea, Architectibranchia, cf. Haszprunar,198%) lacks longitudinal folds and oesophageal glands (Fretter & Graham, 1949, 1954, 1962Fretter, 1960;Rudman, 1972;Brown, 1979;Haszprunar, 1985d, e). It must be emphasized that this configuration is identical to that in Valvata (Cleland, 1954: 177-178, 199 and pers.…”

Section: The Oesophagusmentioning

confidence: 99%

The Vetigastropoda and the systematics of streptoneurous Gastropoda (Mollusca)

Salvini‐Plawen

Haszprunar

1987

Journal of Zoology

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The status of the Vetigastropoda, created 1980 to unite zeugobranch and trochoid archaeo‐gastropods, is reconsidered and confirmed in the light of recent investigations. The most important synapomorphic characters of the Vetigastropoda are the ctenidial sense organs (so‐called bursicles), the epipodial sense organs, and the special structure of the oesophagus. The conditions of the archaeogastropod oesophagus are comparatively described. An examination of the relationships of the Vetigastropoda establishes the archaeogastropod nature of the Architaenioglossa. It also demonstrates the monophyletic origin of all higher gastropods, including the Caenogastropoda (s.str.) as well as the Pentaganglionata (= Euthy‐neura). The Campanilidae, Valvatidae, Rissoellidae, Omalogyridae, and the Allogastropoda (= Architectonicoidea and Pyramidelloidea) share characteristics with both of the above‐mentioned groups, but cannot be classified within any of them. These groups are regarded as subsequent offshoots between the caenogastropod and the pentaganglionate level of organization. The level of Archaeogastropoda is redefined by the hypoathroid/dystenoid nervous system and simple tentacle nerves; the remaining Streptoneura are classified as Apogastropoda with epiathroid nervous system, parapedal commissure, and bifurcated tentacle nerves.

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“…Detailed studies of primitive pulmonates are largely limited to those of the Ellobiidae (Morton, 19551, Chilina (Harry, 1964) and Amphibola (Farnie,19 19). Several investigations have been conducted elucidating the anatomy of Acteon tornutilis (Pelseneer, 1893;Guiart, 1901; Fretter & Graham, 1954; Johannson, 1954) and other acteonids (Rudman, 1972a;Bouchet, 1975). Few other primitive opisthobranchs have been studied.…”

Section: Common Ancesty Of the Opisthobranchia And Pulmonatamentioning

confidence: 99%

“…The question of the ancestry of the opisthobranchs and their relationship to the pulmonates is directly related to determination of character states in the least derived, extant opisthobranchs. Studies of this nature have focused largely upon the Acteonidae and, in particular, the genus Acteon (Guiart, 1901;Fretter, 1943;Rudman, 1972a, b).…”

Section: The Search For An Archetypal Opisthobranchmentioning

confidence: 99%

“…Specimens of Acteon hebes and Rictaxis punctocaelatw examined in this study verify this claim. Rudman (1972a) depicted the reproductive system of Pupa kirki as containing a proximal receptaculum and a distal bursa. This configuration has also been described for the closely allied Bullina lineata and Hydatinaphysis (Rudman, 1972b).…”

Section: Relative Primitiveness O F Acteon and Other Acteonidaementioning

confidence: 99%

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Origins and relationships of primitive members of the Opisthobranchia (Mollusca: Gastropoda)

Gosliner

1981

Biological Journal of the Linnean Society

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An examination of possible prosobranch precursors of opisthobranchs and pulmonates suggests that archaeogastropods are poor candidates, as they lack the complex female glands which characterize all higher gastropods. Similarities between members of the Rissoacea and Cerithiacea with the Opisthobranchia and Pulmonata are here considered to be a result of parallel evolution. Much of the basis tor suggesting phylogenetic aRinities between members of these taxa hinges on the supposition that pyramidellids are opisthobranchs. This contention is questioned, as the euthyneurous nervous system and hermaphroditic reproductive system share weak structural and positional homologies with opisthobranchs. The range of morphological variation within the Pyramidellidae should be more thoroughly investigated, as this taxon is poorly known. The reproductive system of members of the Littorinacea is largely homologous with that found in the least derived opisthobranchs and pulmonates. This, when considered in conjunction with other morphological and palaeontological evidence, suggests that the least derived mesogastropods, the Littorinacea, provide a more precise model of the opisthobranch-pulmonate ancestor among living prosobranchs. The specialization of the digestive system in littorinaceans suggests that morphological divergence has taken place following the cladogenesis of these taxa, and that a direct ancestoddescendent relationship cannot be implied from extant littorinaceans.The status of Acteon and other acteonids as archetypal opisthobranchs is questioned. Moditication 01 all morphological systems, with the exception of the shell and mantle complex, diminish the position of the Acteonidae as ancestral opisthobranchs. Members of the Ringiculidae more closely approach the ancestral form, but have undergone modification, as well. No extant opisthobranch retains all plesiomorphic character states. For this reason, in addition to the fact that contusion exists as to the plesiomorphic conditions of some characters within the Opisthobranchia, a hypothetical ancestral opisthobranch is characterized. I t appears that parallel evolution, which confounds the relationships of certain prosobranchs and opisthobranchs, is also evident within the Opisthobranchia. Much of the confusion that has surrounded the determination of phylogenetic relationships within the Opisthobranchia relates directly to the high incidence of parallelism throughout the subclass.

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A study of the anatomy ofPupaandMaxacteon(Acteonidae, Opisthobranchia), with an account of the breeding cycle ofPupa kirki

Cited by 23 publications

References 15 publications

Towards a phylogeny of gastropod molluscs: an analysis using morphological characters

Towards a phylogeny of gastropod molluscs: an analysis using morphological characters

The Vetigastropoda and the systematics of streptoneurous Gastropoda (Mollusca)

Origins and relationships of primitive members of the Opisthobranchia (Mollusca: Gastropoda)

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