Morphogenesis and Variability of Cuticular Structures in the Genus lbla (Crustacea, Cirripedia)

The cuticular structures of adult Ibla cumingi Darwin, I. quadrivalvis (Cuvier) and of the nauplius stages I-IV of I. cumingi have been examined, mainly by scanning but also by transmission electron microscopy. The various kinds of cuticular structures present have been listed and their morphogenetic differentiation is elucidated. The effect of size on the structures has been investigated. Irrespective of the cause of the size difference (sexual dimorphism, stage of growth, stage of ontogenetical development), the cuticular structures in the smaller individuals are simpler (lower level of complexity), they are arranged less regularly and they show a more primitive type of distribution than in the larger individuals. In the deviated males, the cuticular structures vary, but not in the fully developed females and hermaphrodites. It is, therefore, suggested that the males may be a young phylogenetic stage. The function of the cuticular structures has also been discussed.