. The biology of marine animals. Marine animals; Physiology, Comparative. SKELETONS, SHELTERS AND SPECIAL DEFENCES 643 hormonal stimulus releases the activity of tyrosinase, and blood tyrosine is converted into hydroxyphenol. The polyphenols diffuse outwards to the epicuticle, where they are oxidized to orthoquinones; the latter harden the epicuticle and outer layers of the endocuticle. The tegumental glands appear to be the source of polyphenol oxidase (10, 11, 27, 68, 69). Another important, and sometimes dominant, factor in hardening is the deposition of lime salts. After moult, calcificati
. The biology of marine animals. Marine animals; Physiology, Comparative. SKELETONS, SHELTERS AND SPECIAL DEFENCES 643 hormonal stimulus releases the activity of tyrosinase, and blood tyrosine is converted into hydroxyphenol. The polyphenols diffuse outwards to the epicuticle, where they are oxidized to orthoquinones; the latter harden the epicuticle and outer layers of the endocuticle. The tegumental glands appear to be the source of polyphenol oxidase (10, 11, 27, 68, 69). Another important, and sometimes dominant, factor in hardening is the deposition of lime salts. After moult, calcification of the cuticle takes place rapidly. In Cancer and Carcinus the outer layer of the cuticle becomes calcified in 1-2 days, followed by deeper lamellae. The degree of calcifica- tion stands in inverse relationship to the amount of protein present in the cuticle. In newly formed cuticle prior to calcification, and in species with 4- 2- /- 0J l ^ 7^ Epidermis / V / A. _9 so -5 CQ -4 .^\° ~ 3 ^ - 2 - ; - 0 Q CO i—i—r A-*- B Moult Feeding D Formation of new Cuticle Fig. Variations in Amount of Glycogen Contained in the Hypodermts and Hepatopancreas of Cancer pagums during Course of an Intermoult - non-feeding period; feeding period. Moult at A. A-B, period of absorption of water immediately after moult and of calcification. B-C, water absorption and calci- fication complete; period of hardening of integument. C-D, completion of integument, feeding and tissue growth. D-A, premoult, new integument forming. (From Renaud (107).) non-calcified cuticle, there are roughly equivalent quantities of chitin and protein. With the progress of calcification the quantity of protein added to the cuticle decreases. Calcification thus replaces a large proportion of protein that would otherwise be needed for hardening the cuticle, and is an economical process in an environment rich in calcium. Prior to the moult, calcium is resorbed from the cuticle. The fate of this calci
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