Spermatozoa of the Anomalodesmata (Bivalvia, Mollusca) with special reference to relationships within the group |
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Authors: | John M Healy Rüdiger Bieler Paula M Mikkelsen |
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Institution: | Biodiversity Program, Queensland Museum, PO Box 3300 South Bank, Queensland, Australia, 4101;;Department of Zoology (Invertebrates), Field Museum of Natural History, 1400 South Lake Shore Drive, Chicago, IL 60605, USA;;Paleontological Research Institution, 1259 Trumansburg Road, Ithaca, NY 14850, USA |
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Abstract: | Sperm ultrastructure in the marine bivalve order Anomalodesmata is considered in the light of new information for Australian Myochama anomioides and Cuspidaria latesulcata . In M. anomioides , the acrosomal complex lies posterior to the nucleus, in contact with the asymmetrical midpiece mitochondria – an unusual configuration reported from most of the studied Anomalodesmata. Spermatozoa of M. anomioides resemble those of Myadora brevis (both in family Myochamidae). Myochamid spermatozoa are considerably less modified than those of the Lyonsiidae or Laternulidae, and may prove a basal type within the non-septibranch anomalodesmatans. In contrast, C. latesulcata differs from other examined anomalodesmatans in having an anterior acrosomal complex and radial midpiece mitochondria (classic aquasperm features). Sperm data for the Anomalodesmata are limited but congruent with the most recent phylogenetic analyses that recognize distinct 'thraciid' and 'lyonsiid' clades. Results for C. latesulcata suggest septibranch origins before the development of a posteriorly positioned acrosomal complex and mitochondrial asymmetry. |
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Keywords: | bivalves classification Cuspidaria Myochama phylogeny sperm ultrastructure |
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