A new endocrine gland in the antennal segment of the crayfishes Orconectes limosus and Astacus astacus

Crustacean hematopoiesis

Crustacean hemocytes are important mediators of immune reactions, and the regulation of hemocyte homeostasis is of utmost importance for the health of these animals. This review discusses the current knowledge on the lineages, synthesis and differentiation of hemocytes in crustaceans. Hematopoietic tissues, their origins, and the regulation of hematopoiesis during molting, seasonal variation and infection are discussed. Furthermore, studies concerning the molecular regulation of hemocyte formation in crustaceans are also described, and the different lineages and their molecular markers are discussed and compared with several insect species. Signaling pathways and the regulation of hematopoiesis by transcription factors are typically conserved among these arthropods, whereas cytokines and growth factors are more variable and species specific. However, considering the great diversity among the crustaceans, one should be cautious in drawing general conclusions from studies of only a few species.

Effect of Y-organ removal on limb regeneration and molting in the terrestrial crab, Sesarma haematocheir

The effect of Y-organ removal on limb regeneration and molting was investigated in the crab, Sesarma haematocheir. Basal growth of regenerating limb bud was achieved independently of the Y-organs. However, bilateral removal of the Y-organ inhibited premolt growth and molting. It was also found that removal of the Y-organs from crabs at stage D2 inhibited further premolt growth of regenerating limb bud and molting. Ecdysterone injections in Y-organless crabs induced premolt growth of regenerating limb bud and gastrolith formation, but were insufficient to induce molting.

The hemopoietic character of the "cephalic gland" in the crayfish Orconectes limosus

Topographical, histological, and radioimmunological reinvestigations of the "cephalic gland" in the head of the crayfish Orconectes limosus demonstrated that this tissue is not of an endocrine nature. It is a part of the hemopoietic tissue and does not produce ecdysteroids.