World Congress of Malacology Antwerp ... - Unitas Malacologica

accessible tidal flats. This assemblage can be found on the under-surface of deeply embedded stones
and decaying wood, sometimes with filamentous bacterial mat. Species exclusive to the assemblage
belong to Phenacolepadidae, Iravadiidae, Elachisinidae, Vitrinellidae and Cornirostridae. Their close
relatives often inhabit vents, seeps and/or sunken wood, suggesting ties between these shallow- and
deep-water biotopes.
Phenacolepadidae is a group of limpets and snails adapted to various dysoxic environments in
shallow and deep seas including vents, seeps and sunken wood. They bear a huge gill, and their blood
is crimson as they have red-blood cells or erythrocytes to increase capacity to transport oxygen.
Taxonomic diversity of the family is much higher than previously expected. Dozens of undescribed
species have been found from such intertidal habitats as the underside of deep-embedded stones and
driftwood and the inside of shrimp burrows. Mitochondrial (COI, 12S & 16S) and nuclear (28S) gene
phylogenies reveal two robust clades in Phenacolepadidae: one with shallow-water and sunken-wood
species and the other with vent and seep taxa. Each shallow-water, sunken-wood and vent group is
polyphyletic or paraphyletic, indicating repeated habitat shifts since the late Cretaceous or early
Cenozoic. These recent habitat shifts are well explained by their high dispersal capability. Evidences
from laboratory culture, geographic distribution, population genetics, protoconch and opercular
morphology suggest extended larval period in the open ocean for all phenacolepadids. Re-evolution
of shell coiling and functional operculum is plausible for the methane-seep snail Bathynerita, a
descendant of the vent limpet Shinkailepas.
What is supporting the Neogastropoda monophyly? New evidences for the paraphyly
Kantor, Yuri I.; Fedosov, Alexander
A.N.Severtzov Institute of Ecology & Evolution, Russian Academy of Sciences, 33 Leninski
prospect, Moscow 119071, Russia,
Email: kantor@malaco-sevin.msk.ru; fedosov_zool@mail.ru
Neogastropoda are generally considered monophyletic, although this usually is contradicted in
molecular analyses. The latter requires serious reconsideration of the syn- ant autapomorphies
defining the group. One of the uncontroversial monophyletic groupings within the Neogastropods is
the superfamily Buccinoidea. This very taxonomically rich clade lacks 2 out of three characters,
which are considered as key autapomorphies, namely accessory salivary glands and the rectal gland.
The only other autapomorphy of the Neogastropoda uniting Buccinoidea with the rest of the group is
the so-called valve of Leiblein.
The study of the morphology of the valve of Leiblein of different Neogastropods (2 species of
Raphitominae, Conidae, one of Muricidae, one of Nassariidae, one of Buccinidae, one of
Cancellariidae, one of Volutomitridae) revealed its strong morphological heterogeneity. E.g. in
Muricidae, Volutomitridae and Cancellariidae the dorsal folds (and corresponding groove) of the
anterior oesophagus can be traced within the valve, while in Buccinacea the lumen of the valve is
uninterrupted. In Cancellariidae the cone of cilia is absent, while the valve itself is very long, spiral
forming nearly three volutions.
Published and original data on the embryonic development of the valve in Buccinidae and Muricidae
demonstrated that it originates from different sections of the anterior foregut.
The preliminary data indicate that the homology of the valve of Leiblein within Neogastropoda is at
best questionable. This is casting doubts in the monophyly of the Neogastropoda in general, which
probably include at least two stems.
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