Among the proposed functions of carotenoids in aquaculture have been those of pigmentation, antioxidant functions, as a source of pro‐vitamin A, cellular protection from photodynamic damage, enhancement of growth and reproductive potential. However results reported by various authors are often contradictory. Some evidence suggests that these pigments may perform vital roles in growth and reproductive success in Crustaceans. Additional efforts need to be devoted to the understanding of the active forms of the carotenoid derived metabolites, retinoids in crustaceans. Dietary carotenoids are the sole biological precursors of retinoids in crustaceans. The importance of carotenoids as bioactive molecules reside to a large degree on their conversion to retinoids that are involved in the activation of hormonal nuclear receptors. Retinoids play a prominent role in many developmental processes, including embryonic development and differentiation of various cell types. The presence of receptors of retinoic acid in crustaceans and our findings of retinoids in the neuroendocrine complex and in reproductive tissue, as well as the enhancement of the ovarian development in shrimp suggests an important role of these metabolites in shrimp physiology for their successful aquaculture.

Regeneration of lost walking legs in the fiddler crab Uca pugilator is divided into three distinct phases-wound healing, basal growth, and proecdysial growth. By means of HPLCI RIA analysis of levels and composition of endogenous ecdysteroid hormones and in vitro assays of 14C-leucine incorporation, we have determined that the transition between anecdysis and proecdysis is the point at which limb bud growth is most affected by ecdysteroids. The growth that occurs during proecdysis is programmed during the anecdysislproecdysis transition by a small peak of ecdysteroids (Peak I). Early exposure to 20-hydroxyecdysone at this critical window is necessary for further proecdysial growth of limb buds. The later peak of ecdysteroids (Peak 11) seen in the hemolymph of these crabs during late proecdysis does not seem to be involved in the regeneration process.

No abstract

No abstract

No abstract