Pseudovermis paradoxus, Pereyaslavtzeva, 1891

Flammensbeck, Christina K., Haszprunar, Gerhard, Korshunova, Tatiana, Martynov, Alexander V., Neusser, Timea P. & Jörger, Katharina M., 2019, Pseudovermis paradoxus 2.0 - 3 D microanatomy and ultrastructure of a vermiform, meiofaunal nudibranch (Gastropoda, Heterobranchia), Organisms Diversity & Evolution (New York, N. Y.) 19 (1), pp. 41-62 : 51

Redescription of P. paradoxus

The lack of original type material of P. paradoxus hinders reinvestigation of ambiguous characters in Kowalevsky’ s description (1901a) and required the recollection of new and adequately fixed material. The specimens of Pseudovermis described in the present study were collected near the type locality of P. paradoxus , which is so far the only pseudovermid species reported from the Black Sea. We identified P. paradoxus because the external morphology of the examined specimen corresponds to the original description by Pereyaslavtzeva (1891) and redescription in Kowalevsky (1901a) with the exception of a different number of cerata (seven pairs in the redescription ( Kowalevsky 1901a) vs. 11 pairs herein). However, most of Kowalevsky’ s specimens were immature ( Kowalevsky 1901a) and the number of cerata in Pseudovermis is known to depend on the maturity and increases during ontogenesis ( Fize 1961). Furthermore, the external visibility of the inconspicuous cerata of P. paradoxus highly depends on the stage of contraction of the animal; thus, individual cerata might have been easily overlooked in previous examinations. The present redescription of P. paradoxus corrects and widens the redescription by Kowalevsky (1901a) benefiting from advanced 3D microanatomy and supplements new data especially on the CNS, the jaw morphology, and the reproductive system.