Genetic differentiation of black tiger shrimp Penaeus monodon Fabricius (Crustacea: Decapoda) in Andaman and Nicobar islands

Black tiger shrimp Penaeus monodon from 19 locations of Andaman and Nicobar Islands were studied for genetic differentiation and variability using allozyme electrophoretic analysis. Thirty two presumed loci were consistently expressed from 25 enzymes and a general protein, and these were also temporaly stable during the period 2002-2005. The percentage of polymorphic loci, mean number of alleles, mean effective number of alleles, observed homozygosity, expected homozygosity, observed heterozygosity, expected heterozygosity, average heterozygosity, gene flow (Nm), Fis, Fit, Fst, Rare alleles, monomorphic loci, diagnostic loci, genetic identity, genetic distance and establishment of breeding boundaries were documented in all tested populations, and between the population of Andaman group and Nicobar group of islands. Colonization of P. monodon population due to the decrease of genetic diversity has been formed from north Andaman to south Andaman. As a result, two insular populations i.e., A (Andaman group of islands) and B (Nicobar group of islands) were differentiate

Successful captive breeding and juvenile production of the tomato anemonefish, Amphiprion frenatus

The tomato anemonefish Amphiprion frenatus belonging to the family Pomacentridae and subfamily Amphiprioninae has very high demand in the marine aquarium industry due to their attractive bright red colouration. The adult A. frenatus is bright orange-red in colour, with one white vertical stripe just behind the eyes, joined over the head, whereas the juveniles are dark red, with three vertical white bands and black pectoral fins

स्फूटनशाला में समुद्री अलंकारी क्लाउन मछलियों का बीजोत्पादन : आजीविका के लिए एक लाभकारी विकल्प

कृपया पूरा लेखा पढ

Protandrous hermaphroditism in the clown fish Amphiprion percula from Andaman and Nicobar islands

Gonadal sex differetiation through histological analysis and social structure were investigated in anemone fish Amphiprion percula occuring in Andaman and Nicobar islands. Field observation in different locations of Bay island showed that this species is always seen in association with their host sea anemones Heteractis magnifica H. crispa and Stichodactyla gigantea as small social groups that include an adult pair and one to three juveniles (sub adults) and the largest fish is usually the female and the next largest one is the functional male. Considerable size difference consistently appeared between the sexually active female and male, and noticed that a hierarchy exists in which the female is the dominant individual in a social group. Histological examination of gonads indicated that all juveniles start their life as male and subsequently changes into females as they reach larger sizes and mature. Based on the histological observation, the gonad was categorized into seven phases: immature phase, preripe male phase, ripe male phase, transitional phase, pre-ripe female phase, ripe female phase-I and ripe female phase-II. All the juveniles had ambosexual gonads with testicular and ovarian tissues. Fishes in ripe female phase-II had ovaries with many fully grown yolky oocytes and vitellogenic oocytes, which were absent in ripe female phase-I, and characterized by the presence of many perivitellogenic oocytes and an ovarian cavity but have no testicular tissue. The study confirmed the sex reversal in A. percula from male to female (protandrous hermaphroditism). The field study supported that social structure plays an important role in its sex change

Mass culture of microalgae as an inherent part of hatchery operation- Winter School on Recent Advances in Breeding and Larviculture of Marine Finfish and Shellfish

Microalgae are microscopic unicellular phytoplankton which have less than 10 μ size. These floating planktons being the predominant component of the first tropic level in the aquatic food chain has got immense value as an aquaculture live feed and as a result the production of unicellular algae has gained importance in several countries due to their wide use as food in the hatchery. Most micro algae are rich sources of essential fatty acids; vitamins such as B12, B6, B1, biotin, riboflavin, nicotinic acid, pantothenate, C, E and A; chlorophyll ‘a’ and ‘b’ and carotenoids and these plankton plays a vital role in aquaculture to meet the nutritional requirements of the larvae as well as for bio-encapsulation. It is, therefore, its culture is an inherent part of aquaculture operation. The successful rearing, growth and survival of larvae in the hatchery depends upon the provision of suitable strain of these microalgae during their critical stages of life cycle. The algal species may vary in size, shape and nutritional quality, and are also used for generating “green water” system in many hatcheries. Inspite of all efforts to replace micro algae by artificial feeds, aquaculturists are still depending on the production and use of micro algae as live food for the fishes during their different stages of life cycles. In addition to these, micro algae together with bacteria have an important role in oxygen balance in fish culture system

Comparative Analysis on the Growth Response of Diatom Skeletonemu costaturn in Different Culture Media

Nine culture media, such as Walnes, PM, SEAFDEC, TMRL, Suto, Miquels, Guillard f, f12 and fl4 have been used to find out suitable media for successful culture of Skeletonema costatum which are widely used as larval food of prawns. Among the tested media, Walnes has given best multiplication (14.5 lakhs cells ml-I) of this species under laboratory conditions. The study revealed that the culture has to be harvested on 3rd to 4th day in media Walnes, Guillard f, TMRL, PM, SEAFDEC and Miquels whereas algae in the media of Suto, Guillard fl2 and Guillard f14 can be harvested on 2nd to 3rd day of culture after inoculation. The availability of nutrients such as nitrate, phosphate, iron and silicate is essential for the production of this species, and their appropriate proportions are required in the culture media to escalate the maximum cell multiplication. To keep the starter culture in good condition, Skeletonema culture is needed to be reinoculated on every 3rd day of its culture

Present scenario of marine ornamental fish trade in India captive breeding, culture, trade and management strategies

The marine ornamental fish industry has been expanding rapidly in recent years. The global annual marine om a me n fa I trade as at present is estimated at US$ 200 - 330 million. Nearly 98"/0 of the marine omamental fish species marketed are from the wild collected mainly from coral reefs of tropical developing countries

Seed production of marine ornamental fishes for trade

The marine ornamental fish industry has been expanding in recent years and the global marine ornamental fish trade is estimated at US $ 200-330 million. Nearly 98% of the marine ornamental species marketed are wild-collected mainly from coral reefs of tropical developing countries

Sex change of hatchery produced Amphiprion ocellaris: Influence of mating system removal on gonad maturation and nesting success

The influence of gonadal maturation and nesting success of the anemone fish Amphiprion ocellaris was analyzed through mating system removal. Four experiments viz., (i) Sex change of active male to female in the absence of active female, (ii) Juveniles in the presence of a functional male that was changing sex from male to female, (iii) Juvenile in the presence of a functional female, and (iv) Same length group juvenile fishes (total length: 50 mm) without the presence of adult fishes, were carried out. The gonad of male in experiment (i) showed first perceptible sign of sex inversion after 1 to 2 weeks. After 25 weeks the testicular zone almost disappeared and the gonad looked like maturing ovary with perivitellogenic oocytes and oocytes at various stages of development. The gonad of juveniles in the second experiment showed increased testicular development after 23 to 24 weeks, and testicular area became clearly discernible after 30 weeks. In the third experiment, the gonad of juvenile completed its spermatogenesis after 15 to 16 weeks and showed well-developed testicular zones. In the fourth experiment, the gonad of largest fish showed development of ovarian part after 24 weeks with oogonia and oocytes at various stages, and degeneration of testicular tissues. The observation of nesting success in the above experimental groups showed that spawning was obtained in the third group after 4 months of association; and after 12 to 18 months in the first and second groups, and after 20 to 24 months in the fourth group. The present study shows that in the absence or disappearance of adult female, the active male changes sex to female within a period of 25 weeks. The study also confirms that in the clownfish A. ocellaris, the largest and socially dominant fish in a host sea anemone (Heteractis magnifica) is generally female, whose gonads are functional ovaries with remnants of degenerated testicular tissues. The second largest fish in the same group is an active male and has gonad that are functioning testis but also possess non-functioning or latent ovarian cells (ovotestis). If the dominant female dies or is experimentally removed from the "queue", the male not only changes sex but also grows at an accelerated rate, and the juveniles also grow faster to become male and fill the size gap of the social group. This adaptation allows continuous reproduction. It is found that social structure plays an important role on the sex changing mechanism