THE STUDY OF THE SIDE-LINE ORGANS IN AMPHIPODS (CRUSTACEA, AMPHIPODA).2. COMPARATIVE, MORPHOLOGICAL ANALYSIS OF THE SIDE-LINE ORGANS IN DIFFERENT SPECIES OF AMPHIPODS

The interspecific variation of the side-line organs in 34 species of B aikal amphipods from 21 genera belonging to different phylogenetic lin es, ecological groups and life forms, in the freshwater palaearctic Ga mmarus lacustris Sars and marine Stegocephalus inflatus kroyer was stu died. The size of clavi in Baikal amphipods varies from 2.4 to 24.6 mc m. Long and slender microtrichs are characteristic for nectobenthic sp ecies and planktonic M. branickii short and thick ones were observed i n burrowing species, parasitic species (Pachyschesis) and necrophages (Ommatogammarus). Clavi are arranged in rows or fields of irregular co ntours, which are highly variable. The asymmetry (sometimes very signi ficant) in the shape and arrangement of the right and left groups of c lavi was revealed. Their number in Baikal amphipods usually was no mor e than 10-15 per group. The maximum number was observed in necrophage O. albinus (Dyb.) up to 85 clavi in a group). Probably, the side-line in amphipods is a multifunctional system (seismosensitive, hydrodynami cal and chemosensitive). The side-line organs in amphipods represent a further interesting example of the parallel and independent developme nt of similar systems in vertebrates and Arthropoda.