REDESCRIPTION OF THREE SPECIES AND A SUBSPECIES OF THE MYSID GENUS PARAMYSIS (MYSIDA, MYSIDAE) FROM THE PONTO-CASPIAN BASIN

BY

MIKHAIL DANELIYA1,3) and VICTOR PETRYASHOV2) 1) Finnish Museum of Natural History, P.O. Box 17, FI-00014, University of Helsinki, Finland 2) Zoological Institute of the Russian Academy of Sciences, Universitetskaya naberezhnaya, 1, 199034, St.-Petersburg, Russia

ABSTRACT

Paramysis Czerniavsky, 1882, the most diverse genus of mysid crustaceans (Mysida, Mysidae) in the Caspian Sea and Black Sea region, includes a number of species with unstable and confusing nomenclature. Three species and one subspecies are redescribed here based on characters from recent taxonomic and phylogenetic studies as well as on new diagnostic features. Neotypes are designated for P. (Mesomysis) intermedia (Czerniavsky, 1882) and for P. (Paramysis) kessleri sarsi (Derzhavin, 1925), and a lectotype and paralectotypes for P. (P. ) eurylepis (G. O. Sars, 1907) and P. (P. ) kessleri kessleri (Grimm in MS) G. O. Sars, 1895. Paramysis armata Czerniavsky, 1882, is excluded from the synonymy of P. kessleri and declared nomen dubium. The diagnosis of the subgenus Mesomysis Czerniavsky, 1882, is updated with the addition of new characters.

RÉSUMÉ

Paramysis Czerniavsky, 1882, le genre le plus diversifié de crustacés Mysidacés (Mysida, Mysidae) en Mer Caspienne et dans la région de la Mer Noire, inclut un certain nombre d’espèces ayant une nomenclature instable et peu claire. Trois espèces et une sous-espèce sont redécrites ici à partir d’études récentes, taxonomiques et phylogénétiques ainsi que de nouveaux traits diagnostiques. Des néotypes ont été désignés pour P. (Mesomysis) intermedia (Czerniavsky, 1882) et pour P. (Paramysis) kessleri sarsi (Derzhavin, 1925), et un lectotype ainsi que des paralectotypes pour P. (P. ) eurylepis (G. O. Sars, 1907) et P. (P. ) kessleri kessleri (Grimm in MS) G. O. Sars, 1895. Paramysis armata Czerniavsky, 1882, est exclue de la synonymie de P. kessleri et déclarée nomen dubium. La diagnose du sous-genre Mesomysis Czerniavsky, 1882, est actualisée avec l’addition de nouveaux caractères.

3) Author for correspondence; e-mail: mikhail.daneliya@helsinki.fi © Koninklijke Brill NV, Leiden, 2011 Crustaceana 84 (7): 797-829 Also available online: www.brill.nl/cr DOI:10.1163/001121611X577954 798 MIKHAIL DANELIYA & VICTOR PETRYASHOV

INTRODUCTION The mysid genus Paramysis Czerniavsky, 1882 consists of 21 currently recog- nized species and is distributed in the Caspian Sea and Black Sea basins, the coastal waters of the Mediterranean Sea, and in the subtropical to low-boreal East Atlantic, with its major diversity in the brackish and fresh waters of the Ponto-Caspian re- gion. The taxonomy and phylogeny of Paramysis were intensively studied, espe- cially in recent decades (Daneliya, 2002a, 2004; Audzijonyte˙ et al., 2006, 2008; Daneliya et al., 2007), and new morphological and molecular characters were in- troduced to clarify the relationships within the genus. Among morphological char- acters, the detailed composition and fine structure of setae were found to be useful in the diagnostics and classification. The genus was subdivided into 8 subgenera (Daneliya, 2004): Paramysis s. str., Longidentia Daneliya, 2004, Mesomysis Cz- erniavsky, 1882, Metamysis Czerniavsky, 1882, Nanoparamysis Daneliya, 2004, Occiparamysis Daneliya, 2004, Serrapalpisis Daneliya, 2004, and Pseudoparam- ysis Bacescu,˘ 1940. The discovery of new important characters also demanded redescription of the species. Meanwhile, a number of Paramysis taxa, described by the end of the 19th and the beginning of the 20th century, have nomenclatural problems: confusing synonymy and unclear status of the type material. The pur- pose of this paper is to clarify the nomenclature and to redescribe four problematic taxa, which represent two subgenera, Paramysis s. str. and Mesomysis Czerniavsky, 1882.

Taxonomic history Paramysis (Paramysis) kessleri (Grimm in MS) G. O. Sars, 1895, was first found at several localities around the South Caspian Sea by Grimm (1874, 1875, 1876, 1877). He characterized it only as a “very big” mysid, which is truly the largest mysid in the Caspian Sea, and gave a name Mysis kessleri (Grimm, 1877). While Grimm even prepared a description of the species, he never published it himself (Sars, 1895). The manuscript, as well as the specimens, finally fell into the hands of Sars, who then described the species on the basis of Grimm’s series and with the name initially suggested by Grimm, but put it into the genus Paramysis. Meanwhile, after Grimm’s finding of the species, but before its formal description, Czerniavsky (1882) described the taxon Paramysis armata Czerniavsky, 1882, from the North Caspian Sea. Sars (1893) inspected the remains of a single type specimen of P. a r m a t a and concluded that it was closely related to P. baeri Czerniavsky, 1882 (= P. (P. ) baeri). Although the original description, based on a single immature female, was rather poor, and the type specimen has finally been lost, Derzhavin (1939) concluded from Czerniavsky’s figures that P. kessleri was probably a synonym of P. a r m a t a . He did not, however, restore the priority of