Platycampus larvae are highly cryptic leaf feeders characterised by a dorso-ventrally flattened body, the dorsal integument resembling a shield. Dorsal and ventral cuticles from Platycampus luridiventris were compared by histology and gel electrophoresis. By Azan-staining, a red and a blue layer were distinguished in the dorsal cuticle, while the ventral cuticle showed one, almost uniform blue layer, as in both cuticles of control species. The two cuticles from P. luridiventris had similar amounts and sodium dodecyl sulphate-polyacrylamide gel electrophoresis profiles of soluble proteins, but not insoluble proteins. One insoluble protein (MW approximately 41 kDa) was visible as a large band in the ventral cuticle only. It is likely that this protein renders the cuticle elastic, and that the dorsal, red layer is the exocuticle, mainly composed of insoluble proteins. We discuss eco-physiological implications of the exocuticle in insects. Further, data from the literature indicate that the defence strategy in P. luridiventris larvae relies on being visually cryptic towards avian predators and tactically cryptic towards arthropod predators and parasitoids. Crypsis in both senses is favoured by the shield effect, itself based on an abnormally thick dorsal exocuticle. Although the larvae are external feeders, they may be considered as hidden from an ecological perspective.
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The growth increments were investigated of late medieval, post-medieval and modern otoliths of plaice, cod and haddock from the North Sea. Thin-sectioned otoliths were used to age all the analysed individuals and to reconstruct their growth patterns. In addition, fish lengths of the archaeological specimens were calculated after the relation between otolith width and fish length was established using modern material. The age and fish length distribution, and the growth patterns obtained on the archaeological material allow inferences about fish trade, market strategies and consumption behaviour on producer sites (coastal sites) and consumer sites. Differences in growth patterns were observed between the archaeological and recent populations of the three demersal species analysed which may be related to a change in fishing pressure through time. However, diachronic changes in species distribution, temperature, food availability and selection of catch in function of market strategies may have played a role as well. Age and body size data allow some inferences about the exploited fishing grounds, but the growth patterns are of limited use in this respect.
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