Nature of the Cuticle of Pycnogonida

Abstract

RECENT work has tended to show that, in spite of differences in structural features, the cuticle of insects conforms to a basic pattern in consisting of an inner protein-chitin endocuticle and an outer non-chitinous lipoprotein layer bounded externally by a very thin lipid membrane¹. Although the cuticle of other groups of Arthropoda are not known in such detail as in insects, previous work indicates that in general the pattern in them may not be unlike that in insects. However, in the mode of hardening of the cuticle marked differences have been noted. While in insects the hardening is by phenolic tanning, in crustaceans, though the cuticle is initially hardened to some extent by phenolic tanning, the prime cause of hardening is by calcification². In arachnids such as Limulus ³ and Palamneus ⁴ there is evidence of the occurrence of hardening by sulphur linkages. Although the significance of such a mode of hardening in the above-mentioned types is not clear, it appears that it may be more common than has hitherto been suspected. It is therefore of interest to find in the cuticle of Propallene kempi, a common pycnogonid of Madras, evidence to suggest the occurrence of disulphide linkages which are probably involved in the hardening of the cuticle.