Quarterly Journal of Microscopical Science, Vol s3-95, 183-190, Copyright © 1954 by Company of Biologists

Properties of the Minerals in the Exuvia of Crustacea

¹ Department of Zoology and Comparative Anatomy, University Museum, Oxford

An unusual reaction between material in the exuviae of Crustacea and pure cold mercuric chloride, resulting in the deposition of a bright red compound, led to the discovery that, contrary to expectation, the inner surface of the fresh moult, and even of the inter-moult exoskeleton, is strongly alkaline (_pH = 9.1). This is near the optimum for both alkaline phosphatase and carbonic anhydratase, which both may be active in resorption of mineral preparatory to ecdysis. Correlations between the distributions of the red Hg-compound, phosphate, carbonate, alkaline phosphatase, and pigmentary pattern have been found in various Crustacea. The reaction with cold HgCl₂ is given also by the millipede exoskeleton, the molluscan shell, the calciferous gland-material of earthworms (_pH 9.2-9.4) and by calcareous sponges, but not by echinoderm or vertebrate skeletons, and not by the exoskeleton of insects, spiders, and centipedes, which lack mineral. The compound(s) with mercuric chloride are probably chiefly oxychlorides. A steady, if slight, solution of the skeletal carbonate and phosphate is necessary to maintain the observed high pH, and to permit the formation of these mercury-compounds.