Reproduction and rapid growth in a deep-sea aplacophoran
mollusc, Prochaetoderma yongei.
a neomenioid) aplacophoran
mollusc Proneomenia custodiens, unhatched juveniles were used.
html) "A Silurian armoured aplacophoran
and implications for molluscan phylogeny.
Only one-third of the collected species of Aplacophoran
molluscs have been named and described even though they are an important component of the deep-sea fauna and often appear among the ten most abundant species.
Indeed, the great malacologist Johannes Thiele, with far less information than is now available, and who published over 20 aplacophoran
species descriptions, concluded that aplacophorans
were not molluscs as such, but phylogenetically between annelids and molluscs and ancestral to the latter (Thiele, 1913c; Glaubrecht et al.
The observed variance to mean ratios of 10-100 for live oyster density estimates in the James River are comparable to those reported for hard clam (Mercenaria mercenaria, Fegley 2001) and aplacophoran
(Scheltema 1985) populations.
ABSTRACT Species of the neomenioid aplacophoran
genus Helicoradomenia Scheltema & Kuzirian are found only in areas of hydrothermal vents, oceanic ridges, and back-arc basins and have been collected widely in the East Pacific, Southwest Pacific, and the Triple Junction in the Indian Ocean, but not in the Atlantic.
It may very well be, however, that the ciliated cells in question are derived from the trochoblast cell lineage, as has been suggested for pericalymma larvae of protobranch bivalve and neomenioid aplacophoran
molluscs (Thompson, 1960; Zardus and Morse, 1998), and shown to be the case in the palaeonemertean Carcinoma tremaphoros (Maslakova et ah, 2004).
Most strikingly, this is exemplified in the Mollusca, where the most basal forms, the aplacophoran
taxa Neomeniomorpha and Chaetodermomorpha, constitute a vermiform appearance, while all other molluscan subgroups derive from benthic or pelagic shell-bearing taxa (Ponder and Lindberg, 2008).
Larval descriptions are based on five neomenioid aplacophoran
species: Epimenia babai Salvini-Plawen, 1997 (as E.
Because siboglinids are not closely related to molluscs and because of rate heterogeneity problems within the Mollusca, only a single representative (the aplacophoran
Scutopus) was used.
Recent accounts of aplacophoran
anatomy are given in Salvini-Plawen (1985) and Scheltema et al.