A cytogenetical study of Ischyroceridae (Amphipoda) allows the identification of a new species, Jassa cadetta sp. n., in the Lagoon of Venice

Jassa cadetta sp. n. (Amphipoda: Ischyroceridae) is described from the Venice Lagoon, northern Adriatic Sea, and a key to Mediterranean members of the genus Jassa Leach is provided. The new species is separated from J. marmorata Holmes primarily by cytogenetics, differing in chromosome number (2n=10 in J. cadetta vs. 2n=12 in J. marmorata), karyotype morphology (FN=20 vs. FN=22), and chromosome location of 18S-5.8S-28S ribosomal cistrons. Cytogenetic analysis of Ischyrocerus anguipes Krøyer (2n=10, FN=18) gives a first insight into karyological diversity among Ischyroceridae. Analysis of random amplified polymorphic DNA markers confirms the distinction between J. cadetta sp. n. and J. marmorata.