Neuroendocrine control of water content and calcium concentration in the crab Ocypode macrocera (H. Milne-Edwards 1852) (Brachyura, Ocypodae)

The present study is focused to see the effect of crustacean neuroendocrine organs on the water and calcium metabolism which is very much important for the osmoregulatory functions. Since the experiments were carried out to investigate the control of water contents and calcium concentration in the crab, Ocypode macrocera. The animals were collected from the shore of the Bay of the Bengal near Annan Koil one among the biggest landing centers of south east coast of Tamil Nadu, India. The data revealed that water content in the hepatopancreas and thoracic muscle of the control crab were 70.16 and 79.86%, respectively, whereas in the experimental ones, the values were 80.32 and 87.44% after eyestalk removal and 54.52 and 66.98% after eyestalk extract injection. Calcium concentration in both the hepatopancreas and thoracic muscle of the control crab were 2.16 and 2.14 mg g(-1), respectively, whereas in the experimental animals the values were 2.76 and 3.52 mg g(-1) in the eyestalkless crabs and 1.52 and 1.57 mg g(-1) after eyestalk extract injection, respectively. Hence it was observed the % of water content is more in eyestalk less crabs as compared to that of control and injected. The roles of neurosecretory secretions, which control these parameters, were discussed. The ability for Ocypode macrocera to adapt rapidly and maintain homeostasis in a wide range of abnormality supports the fact that Ocypode macrocera are a suitable species for land-based aquaculture in ponds as well as critical condition where rapid fluctuation in salinity can occur.

Hormonal regulatory role of eyestalk factors on growth of heart in mud crab, Scylla serrata

The present study was attempted to know the growth regulation of eyestalk factors on the growth of heart in Scylla serrata using eyestalk extractions and bilateral eyestalk ablations. The bilateral eyestalk ablation led to the maximum growth indices of the heart ((H) indices) to 0.162 and 0.158 in ablated male and female, respectively, in comparison to 0.153 and 0.167 in the control male and female and 0.147 and 0.157 in injected male and female, respectively. The data have shown that the heart of male crabs grows faster than female crabs. The study has also shown that bilateral eyestalk ablation resulted in a significant increase in the heart indices in males and has least effect on the growth of the female heart. The results presented strongly support a potential role of the eyestalk factors and molting hormone regulating the growth of the heart in S. serrata.