Neuroendocrine mechanisms in relation to control of maturation in cultivable teleost fishes

Reproductive processes are by no means fully impaired in captivity. The progressive development of the gonads -remains, in general, inhibited upto the final stages of gamete maturation, and it is only at the point of gamete release that the sequence is arrested. Both-gonadal maturation and spawning behaviour have long been known in responses to environmental stimuli viz., temperature, light and rainfall etc

Physiological and Endocrinological approaches in captive breeding of marine finfish

Reproductive processes are by no means fully impaired in captivity. The gradual and progressive development of the gonads remains, in general, uninhibited upto the final stage of gamete maturation, and it is only at the point of gamete release that the sequence is arrested. Both gonadal maturation and breeding behaviour have long been known in responses to environmental stimuli viz., temperature, light, rainfall etc. Our fishery scientists have made a timely breakthrough by inventing the technique of induced breeding through hormonal manipulation. Though the induced breeding technique has now been successfully used for carps many brackishwater and marine fishes have either responded to this technique with partial success or no response. This is because of the lack of understanding the mechanisms involved in the environmental complexities and their impact on neuroendocrine mechanisms in control of reproduction

Physiology of digestion in fishes and shellfishes

Some fish feed on plants, some on animals and a third group derives ijs protein, carbohydrate, fats, vijamins and minerals from both plant and animal sources. Some fishes live on blood and tissue fluid of other fishes (eg. Petromyzon). Some fishes feed on plankton during part of their life and some throughou1 life. Others feed on weeds. Many other feed on zooplankton and also on other larger animals like annelid worms, snail. mussel, clams, crustaceans, insect, birds, mammals, reptiles and amphibians. Even human beings are found in the stomach

Neurological endocrinology: the coordinating mechanism

The nervous and endocrine systems are integrative in nature for they provide th'e organism with sophisticated external and internal sensing devices which feed information into the central nervous system for appropriate responses of the target system

A stepping-stone in developing marine fish gene bank

The science of cryogenic preservation of fertile semen is not only meant for understanding the basic life secret, but also propagating living resources in long run. Efforts are being continuously made world over to evolve suitable methods of obtaining sperms through creation of gamete banks so that through artificial fertilization one will be able to produce the seeds at any time of the year. The central marine fisheries research institute engaged actively for the past 3 years in cryopreservation studies. Through the extensive Research efforts a breakthrough was made in evolving a viable technique for short term and long term preservation of sperm motility of fish liza parsia at —10°c and —196°c temperature respectivel

Freezing of viable embryos and larvae of marine shrimp, Penaeus semisulcatus de Haan

Although sperm cryopreservation has been carried out successfully in a number of commercially important aquatic species, particularly in some teleost fish (see review of Rana in Muir & Roberts 1993) and also shellfish (Subramoniam 1993), the technology is still not at the stage of advanced commercial application that is seen in domestic mammals. Cryopreservation of eggs and embryos, of aquatic animals however, is a virgin field in cryobiology and has not yet received any appreciable amount of attention. The first successful attempt at the cryopreservation of embryos of sea urchin was reported by Asahina & Takahashi (1978). Later Zell (1978) and Erdahl & Graham (1980) have reported preliminary attempts to freeze the eggs of rainbow trout

Osmoregulatory ability of Penaeus indicus H Milne Edwards in relation to varying salinities

Juvenile Penaeus indicus osmoregulated well between 3-26r .. S for 24 and 48 h duration with isosmotic points ~S 18r. . and ~S 14r. . respectively. Adults also showed good osmoregulatory capability between 5-30%0 S with isosmotic points ~S 2W .. and ~S 17%0 for 24 and 48 h duration respectively. A duration of 48 h is essential for prawns to adjust to the new medium. Influence of various neuroendocrine centres on the osmolal concentration of haemolymph was studied. In eyestalk ablated prawns osmolal concentration decreased with time and reached a lowest after 48 h. Eyestalk ablated prawns injected with extracts of eyestalk, brain and thoracic ganglia did not show any decrease in the values with time but remained on par with the values of normal ones

Note on seasonal fishery of Holothuria (Metriatyla) scabra Jaeger from Pamban Island

Out of the nearly 200 species of sea cucumber known from the seas around India, about 75 species are reported from the shallow waters of the Indian coast. Of these about 12 species are commercially important. Holothuria scabra locally ceilled as 'Vella attai' is the dominant species exploited by fishermen by skin diving in the Palk Bay and Gulf of Mannar

Fisheries research and development in India

The fisheries sector of India is immensely contributing to the economy of the country. It provides valuable fore ign exchange and employment to millions of people. At the same time it is an instrument of livelihood for a large section of economically backward population of the country