CRUSTACEAN HYPERGLYCEMIC HORMONE IN THE NERVOUS-SYSTEM OF THE PRIMITIVE CRUSTACEAN SPECIES DAPHNIA-MAGNA AND ARTEMIA-SALINA (CRUSTACEA, BRANCHIOPODA)

Crustacean hyperglycaemic hormone-immunoreactive neuronal systems are detected in the central and peripheral nervous systems of two entomost racan crustaceans, Daphnia magna and Artemia salina, by immunocytochem istry using specific antisera against crustacean hyperglycaemic hormon es of the decapod crustaceans Orconectes limosus and Carcinus maenas. In D. magna, four small putative interneurones are detected in the bra in. In the thorax, ten bipolar peripheral neurones are stained by both antisera. They are obviously segmental homologues with centrally proj ecting axons that form interdigitating varicose fibres and terminals i n putative neurohaemal areas next to the surface of the anterior part of the thoracic ganglia. Similar immunopositive neurones occur both in the central and peripheral nervous systems of A. salina. A total of f ive groups of neurones occur in the protocerebrum, the deutocerebrum a nd the mandibular ganglion. Some of the protocerebral neurones are bip olar and project to the dorsal frontal organ. A single pair of periphe ral multipolar neurones in the maxillary segment projects centrally in to the ventral nerve cord and innervates unidentified somatic muscles and tissues in the maxillary and the first appendage segments. None of the brain neurones in both species show similarities to decapod X-org an sinus gland neurosecretory neurones. Chromatography of brain extrac ts of D. magna combined with immunodot blotting revealed two strongly immunoreactive fractions at retention times close to that of the crust acean hyperglycaemic hormone of crayfish. Moreover, preabsorption cont rols suggest that the cross-reacting peptides of D. magna and A. salin a are structurally closely related to those of decapods.