биота российских вод японского моря - Materials of Alexey Shipunov

CLASS MALACOSTRACA Latreille, 1802Order LEPTOSTRACA Claus, 1880Viktor V. PetryashovGeneral characteristicsThe leptostracans (order Leptostraca) are higher crustaceans belonging to thesubclass Phyllocarida of the class Malacostraca. The body of a leptostracan is dividedinto two tagmata: the cephalothorax and the pleon. The body consists of five cephalic,eight thoracic, seven pleon segments, and a telson, ending with a furca, formed by twoflat rami (pl. I, figs. 1, 2). The eyes are stalked, faceted, but in some deep-water speciesthe eyes lack pigment and not faceted. The cephalon, thorax, and sometimes mostpart of the pleon are covered dorsally, laterally, and in some cases ventrally with acephalothoracic shield, or carapace, fused to the dorsum of the protocephalon. Thecarapace is composed of two valves, fastened together by a muscle-retractor. The frontalmargin of the carapace is provided in the middle with a plate-like movable rostrum.The leptostracans have a pair of antennules, a pair of antennas, eight pairs of thoracicappendages (thoracopods), and six pairs of abdominal appendages (pleopods). Theantennule (antenna I) consists of a four-articulate peduncle (protopod) and a multiarticulateflagellum; the outer side of the antennule is provided with a flat antennularscale. The antenna (antenna II) is uniramous; it consists of a three-, rarer fourarticulatepeduncle and a multiarticulate flagellum-like endopod; an exopod is lacking.The thoracopods are leaf-shaped; each one is composed of a protopod, epipod, exopod,and an endopod, the latter may be one- or many-segmented. The articulations ofthe thoracopod parts may be fused. The first four pairs of the pleopods are well developed;each first to fourth pleopod consists of a two-segmented protopod, flat onesegmentedexopod, and a flat two-segmented endopod. The fifth and sixth pairs of thepleopods are rudimentary small uniramous plates. The seventh pleonal segment iswithout any appendages.The leptostracans are marine crustaceans; they occur in depths from the high sublittoralto the bathypelagial zone. There are twenty-five species of them known presently.They are found in all the world oceans, except for the arctic waters. The leptostracansare deposit-feeders, and pelagic species are apparently filter-feeders.In the females of the families Nebaliidae and Paranebaliidae setae of the thoracopodsform a brood chamber, in which full maturation of embryos takes place. In Nebaliopsidaeeggs are probably laid directly into the water, and organisms developthrough metamorphosis.The leptostracans can be collected using epibenthic sledges, horizontal and verticalplankton nets, as well as trawls and scoop nets. Fixation should be made in 75%ethanol and in 4% formaldehyde.The order is composed of three families, one of which, Nebaliidae, was recordedin the Sea of Japan.Main references: Dahl, 1985, 1996; Martin et al., 1996.37