New records of Amphipoda Hyperiidea in associations with gelatinous zooplankton

Associations between Amphipoda Hyperiidea specimens and gelatinous zooplankton such as cnidarians, ctenophores or salps are known in the literature. It is well established that many hyperiids are intimately associated with gelatinous zooplankton during part or all of their life-cycles, and that the associations could be of commensal or of parasitic nature, sometimes very highly species-specific. Although conventional net sampling usually does not preserve evidence of these associations, 12 instances of association (I.A.) were found in nine of the 49 samples collected during the 'FINEP XI Cruise', carried out on the Southeast coast of Brazil (23–28 °S), in January 1980. Lestrigonus bengalensisGiles, 1887 (11 specimens) and Simorhynchotus antennarius(Claus, 1871) (one specimen) were found inside salps and siphonophores. The study of the nature of these associations is essential to the understanding of the evolution of the group.     

Comparative analysis of the circulatory system in Amphipoda (Malacostraca, Crustacea)

We present data on the haemolymph vascular system (HVS) in four representatives of the major amphipod lineages Gammaridea, Hyperiidea and Caprellidea based on corrosion casting and three‐dimensional reconstructions of histological semi‐thin sections. In all these species the HVS comprises a dorsal pulsatile heart, which is continued in the body axis by the anterior and posterior aortae. The heart is equipped with three pairs of incurrent ostia. The number of cardiac arteries that lead off the heart varies among species: in the studied Gammaridea four pairs occur, in Hyperia galba only the three posterior pairs of cardiac arteries occur, while in Caprella mutica cardiac arteries are absent. In all the studied species the posterior aorta leads as a simple tube into the pleon attached to the dorsal diaphragm. The anterior aorta runs from its origin in the anterior part of the second thoracic segment into the cephalothorax. Both pairs of antennae have an arterial supply off the anterior aorta. An overview of previously studied species including our present findings shows the amphipod HVS to be relatively uniform and the gammarid form is discussed as being closest to the ground pattern of Amphipoda.