CUTICULAR STRENGTH AND PIGMENTATION OF 5 STRAINS OF ADULT BLATTELLA-GERMANICA (L) DURING SCLEROTIZATION - CORRELATIONS WITH CATECHOLAMINES, BETA-ALANINE AND FOOD-DEPRIVATION

Five German cockroach Blattella germanica strains, wild-type (VPI), yellow (y), orange (or), black (Bl), and pale body (Pb) which differ in cuticular colouration, were used to investigate possible correlations of catecholamine and β-alanine concentrations with cuticular strength as measured by puncture resistance of adult pronotal cuticle. The cuticular strength of all strains was the same at ecdysis, but that of VPI, or and y increased more rapidly than Bl and Pb during sclerotization. Cuticle of VPI, y and or reached maximal levels of puncture resistance by day 4, whereas Bl and Pb cuticles failed to achieve this strength by day 14. Extractable N-β-alanyldopamine (NBAD) and N-β-alanylnorepinephrine (NBANE) accumulated rapidly in VPI, y and or cuticles during the first 12 h after ecdysis, but their accumulation was delayed in Bl cuticle until 24 h. Pb cuticle had the least strength and also the lowest NBAD and NBANE levels. β-Alanine concentrations were also lowest in Bl cuticle during melanization. Conversely, dopamine was highest in Bl and or cuticles during melanization but was very low in y and Pb cuticles, which lack black pigmentation. Therefore, N-β-alanyl catecholamine and β-alanine concentrations in cuticle are positively correlated with increasing cuticular strength during stabilization of the exoskeleton, whereas dopamine is correlated with melanization. When dopamine is apparently shunted into the melanization pathway in Bl cuticle or when lower concentrations of the N-β-alanyl catecholamines occur in Pb cuticle, cuticular strength is reduced. Cuticular strength and weight were substantially reduced in cockroaches deprived of food after ecdysis and even later after feeding was resumed. However, cuticular thickness and catecholamine content in starved insects did not differ from those in fed insects. Deficiencies in the protein and chitin content of the procuticle as indicated by reduced weight and density likely result from starvation. Therefore, fewer sites for macromolecular cross-linking or other sclerotization reactions would be available and consequently a weaker cuticle would result. © 1990.