IMMUNOCYTOCHEMICAL STUDY OF THE RED PIGMENT CONCENTRATING MATERIAL IN THE EYESTALK OF THE PRAWN PALAEMON SERRATUS PENNANT USING RABBIT ANTISERA AGAINST THE INSECT ADIPOKINETIC HORMONE.

Using antisera produced against different parts of the insect adipokinetic hormone (AKH), it was possible to detect adipokinetic hormone-reactive peptides in the eyestalk of the prawn Palaemon serratus. Immunopositive staining was obtained in some neurosecretory cells of the medulla externa X organ (MEX), of the medulla terminalis X organ 2 (MTGX-2), in the lower part of the sinus gland, and in the nerve joining the medulla terminalis X organs to this neurohemal gland. The biological activity of synthetic AKH and RPCH (red pigment concentrating hormone) was tested on the movement of the red pigment in the chromatophores of the prawn and compared to the activity of extracts derived from immunoreactive tissue regions. The inhibiting effect of the AKH antibodies on the biological activity was ascertained by immuno-adsorption experiments. The results are discussed in relation to the molecular resemblance of AKH and RPCH. It is postulated that RPCH-material in the eyestalk of Palaemon serratus can be identified by using antisera against AKH-peptide. However, more than one type of immunoreactive RPCH/AKH-like peptide appears to be present in different groups of neurosecretory cells.