#mysid

First report of the order Mysida (Crustacea) in Antarctic marine ice caves, with description of a new species of Pseudomma and investigations on the taxonomy, morphology and life habits of Mysidetes species

Karl J. Wittmann, Pierre Chevaldonné

SCUBA diving explorations of three islands off Dumont d’Urville Station at the coast of Adélie Land, East Antarctica, enabled the observation of marine ice caves. Sampling in this unusual habitat yielded a total of three species of Mysidae, altogether previously poorly known or unknown to science. Pseudomma kryotroglodytum sp. nov. is described, based on the structure of the antennal scale, telson and on cornea-like lateral portions set off against the main body of eyeplates. 

Mysidetes illigi is re-established at species level after almost a century in synonymy. Re-descriptions are provided for M. illigi and M. hanseni, based on types and ice cave materials. Keys to the Southern Ocean species of Pseudomma and to the world-wide species of Mysidetes are given.

Phylogenetic trees are provided for the genera Pseudomma and Mysidetes. 18S rDNA sequences of P. kryotroglodytum differ from GenBank sequences of other Pseudomma species. First sequence data are given for species of the genus Mysidetes: 18S differs between the two examined species and COI is quite diverse between and within species.

We found previously unknown, probably sensorial structures in these ice cave species: in P. kryotroglodytum, the basal segment of the antennula shows a pit-like depression with striated pad on the bottom and a median cyst, connected with the bottom of the eyeplate cleft. M. illigi shows a female homologue of the appendix masculina bearing a field of modified setae. Subsequent investigations demonstrated these structures also in species from other habitats...

Mysis relicta

...is a species of mysid (an order of "shrimp-like" crustaceans) which is native to the lakes of Northern Europe and the brackish Baltic Sea. Mysis relicta was previously treated as a circumpolar taxon which was also present in North America and the Eurasian Arctic, a revision of the species in 2005 divided these populations into four distinct species (Mysis diluviana in the Great Lakes, M. segerstralei in the circumpolar Arctic, and M. salemaai in the Baltic and some European Lakes.   

Classification

Animalia-Arthropoda-Crustacea-Malacostraca-Mysida-Mysidae-Mysis-M. relicta