Revision of the crustacean amphipod genus Jassa Leach (Corophioidea: Ischyroceridae)

Abstract

The crustacean amphipod genus Jassa is revised to encompass the type species J. falcata (Montagu, 1808), the previously recognized species J. ingens (Pfeffer, 1888), J. herdmani (Walker, 1893), J. pusilla (G. O. Sars, 1894), and J. marmorata Holmes, 1903, and the new species J. alonsoae, J. borowskyae, J. carltoni, J. fenwicki, J. gruneri, J. hartmannae, J. justi, J. morinoi, J. myersi, J. oclairi, J. shawi, J. slatteryi, J. staudei, and J. thurstoni. Jassa odontonyx (G. O. Sars, 1894) is synonymized with J. pusilla, and J. pulchella Leach, 1814 is confirmed as synonymous with J. falcata. Jassa wandeli Chevreux, 1906, J. multidentata Schellenberg, 1931, J. goniamera Walker, 1903, J. barnardi Stephensen, 1949, J. lilipuna J. L. Barnard, 1970, and J. ocia (Bate, 1862) will be assigned to other genera. The nomenclatural disposition of other species that were at one time assigned to the genus Jassa is also given. The genus Jassa can be distinguished from its closest relatives by the following key characters: the outer rami of the third uropods are tipped by a pair of cusps and a basally immersed, dorsally recurved spine; the palms of the first and second gnathopods are defined by a cluster of three spines; at the last molt the male produces a thumb-like protuberance on the propodus of the second gnathopods by incision of the palm anterior to the palm-defining spines; and thumbed males have dimorphic second gnathopods.

Long-distance dispersal, low connectivity and molecular evidence of a new cryptic species in the obligate rafter Caprella andreae Mayer, 1890 (Crustacea: Amphipoda: Caprellidae)

“…The most commonly occurring epibionts were the caprellid species C. andreae, the isopod Idotea metallica and the gammarid J. cadetta. The taxonomy of the genus Jassa has been traditionally confusing (Conlan 1990). Although our specimens resemble the recently described species J. cadetta (Krapp-Schickel et al 2008), they also share some characteristics with Jassa slatteryi Conlan, 1990.…”

“…The taxonomy of the genus Jassa has been traditionally confusing (Conlan 1990). Although our specimens resemble the recently described species J. cadetta (Krapp-Schickel et al 2008), they also share some characteristics with Jassa slatteryi Conlan, 1990. As a result, further taxonomical revision of the material, including a molecular approach, would be useful in clarifying the taxonomical status of our specimens.…”

A supplement to the amphipod (Crustacea) species inventory of Helgoland (German Bight, North Sea): indication of rapid recent change

“…Because of high intraspecific morphological variation in the genus Jassa, especially in male reproductive forms (Borowsky, 1985;Conlan, 1989Conlan, , 1990, keys in older literature are often misleading. For instance, J. herdmani is not included in Lincoln's work (1979) on the Gammaridea of the British Isles.…”

“…For instance, J. herdmani is not included in Lincoln's work (1979) on the Gammaridea of the British Isles. Fortunately, Conlan (1990) in her revision of the genus Jassa provided a reliable tool to distinguish North Atlantic Jassa-species by using characteristics not related to gender and morph. At Helgoland the two species J. herdmani and J. falcata differ from the sympatric J. marmorata Holmes, 1905 in the complete absence of setae on the anterolateral margin of the basis of gnathopod 2.…”

“…Unfortunately, all these distinguishing features are size-and not age-related, so safe morphological determination of small specimens (although already mature) is almost impossible (Conlan, 1990, personal observation). A fourth species, J. pusilla (Sars, 1894), is also reported from change in amphipod species inventory of helgolandthe North Sea (Schellenberg, 1942;Conlan, 1990) but could not be confirmed for Helgoland, yet. Jassa pusilla is much smaller and slender than the other three species mentioned above.…”