POSTER (abstract)

Elena Chaban
cem@AM3963.spb.edu
Laboratory of Marine Researches, Zoological Institute Russian Academy of Sciences,
St.Petersburg, 199034, Russia

" NEW DATA FOR MORPHOLOGY AND TAXONOMY OF THE LITTLE KNOWN GENUS Eoscaphander HABE, 1952 (CEPHALASPIDEA : CYLICHNIDAE) "

The description of the genus and species Eoscaphander fragilis Habe, 1952 includes the shell only and notes that its radula and gizzard plates resembling Meloscaphander sibogae Schepman, 1913. The cylichnid specimen collected near South Kurile Ils. from 535 m was identified as E.fragilis and studied. Lengths of the shell is 24 mm. The specimen has broad cephalic shield folded at the posterior end, foot is short and extends laterally into a pair of small parapodia. Formula radula is 16x2:1:1:1:2, the median plate with two oval denticulated extentions like Cylichna. The lateral teeth have form like C.occulta and C.magna on form and number, but the first lateral teeth are large and brown and the marginal teeth are so small, that is visible with strong magnification only.
Gizzard is large, flat. It has the two band of longitudinal muscles on the each lateral flat sides. The ring of transversal muscles envelops borders of the plates. There are two plates only in the gizzard. They are large (9,0x5,5 mm), flat, oval shape, brown with effaced inside surfaces. The plates of E.fragilis E.fragilis distinguish from the plates of M.sibogae (the later has 3 different ones) but has some similarities with C.magna.
Male copulatory system look like the small muscular sack don’t elevated from the body wall to the body cavity. It consists of two parts: atrium with ciliated duct enveloped muscular folds and prostate.
C.magna has similarity with E.fragilis on radula, gizzard plates, shape and sculpture of the shell, and at last, morphology of the male copulatory system (we studied the specimen from Greenland sea). We consider C.magna belongs to the genus Eoscaphander -- E.magna (Lemche, 1941) comb.n.
The gizzard plates of the both species have similarity more with the gizzard plates of the genus Cylichna than ones of the genus Scaphander. We studied abnormality on number of the gizzard plates inside of the genus Cylichna. (the specimen of C.occulta from Barents sea with one big plate and one specimen of C.alba from Kara sea with the four small plates irregular form) and may be the plates of Eoscaphander aren’t the result of further reduction of the unpaired plates of Scaphander but are the result of reduction of one of the gizzard plates of Cylichna. As we said both genus, Eoscaphander and Cylichna (mostly C.occulta) have similarity in radula. On our view Eoscaphander more closer to the genus Cylichna than to the genus Scaphander.

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