Studies on osmoregulation by neurosecretory system in crustaceans

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To investigate osmoregulation by the central nerve system in crustaceans, topological mass spectrometry analysis was available for the identification of neuropeptides. In the crayfish (Procambarus clarkii), "anal respiration" has been described in the book "The Crayfish : An Introduction to the Study of Zoology" published in 1880. The observation has been noted that water is alternately taken into and expelled from the anus fifteen to seventeen times in a minute and it seemed to be regulated by the sixth abdominal ganglion. Direct matrix-assisted laser desorption/ionization with time-of-flight mass spectrometry analysis with slice of the sixth abdominal ganglion was resulted in the presence of orcokinin and its gene-related peptides, crustacean-SIFamide, decapod tachykinin-related peptide, crustacean cardioactive peptide, myosupressin-like peptide. These peptides were examined in vivo on bioassays for rhythmic anal contraction and anal water flux. The activity of the peptides on the is … More olated intestine was also examined in vitro. Rhythmic anal contraction was caused by orcokinins, decapod tachykinin-related peptide, when each sample of 100 pmol was injected into the crayfish. Crustacean cardioactive peptide had most potent activity of anal opening. Water flux through the anus was observed by injection of crustacean cardioactive peptide or decapod tachykinin-related peptide. Interestingly, the action of the neuropeptides on the isolated intestine was diversified. The contraction of hindgut was activated by orcokinins, but not by crustacean cardioactive peptide or myosupressin-like peptide. Decapod tachykinin-related peptide showed repetitive action alternating between contraction and relaxation on the rectum. Crustacean-SIFamide caused complex movements of the hindgut, and induced most potent activity of defecation. We concluded that the crayfish can take water from the anus, but each function of neuropeptides identified in sixth abdominal ganglion remains unclear. We also think that "anal respiration" might not be a normal phenomenon, since the action was able to be reproduced by the overdose of a combination with crustacean-SIFamide and decapod tachykinin-related peptide. Less