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

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

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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

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

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

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

Broodstock development, breeding, embryonic development and larviculture of spine-cheek anemonefish, Premnas biaculeatus (Bloch, 1790)

The broodstock development, breeding, embryonic development and larviculture of Premnas biaculeatus and different feeding and envrionmental conditioins are reported for the first tiem. The influence of enriched rotifer (Brachionus rotundiformis, Brachionus plicatilis) and non-enriched newly hatched Artemia nauplii along with microalgae (Chlorella marina, Nannochloropsis oculata and Isochrysis galbana) on larval rearing and survival was elucidated. Fishes in the length range of of 55 to 70 mm (presumptive male) and 120 to 150 mm (presumptive female) were selected for pair formation experiments along with single host sea anemone Heteractis magnifica. All the 10 pairs started spawning within four months after they were shifted to the breeding tanks. Eggs were laid in round patches or clutches at intervals of 15 to 20 days with an average of 2.09 ± 0.3 spawnings per month per pair giving an annual number of 1752 -11832 eggs per pair. Upon incubation for six days in complete darkness, 95-98% of the eggs hatched with the peak hatching between 1830 and 1930 hrs. On 20th day post-hatch (d.p.h.), most of the larvae metamorphosed to juveniles and began to shift from partially pelagic to epibenthic and the juveniles reached marketable size from 60th d.p.h. onwards

Life history pathways in false clown Amphiprion ocellaris Cuvier, 1830: A journey from egg to adult under captive condition

There is a vast literature on distribution, rearing conditions and behavioural studies of clownfishes. However, descriptive information on reproductive behaviour, early developments and life history pathways of Amphiprion ocellaris are scarce. In this study, 7 pairs of A. ocellaris having size 89 to 100 mm (presumptive females) and 40 to 60 mm (presumptive males) were developed through pair formation to generate information on breeding and spawning behaviour, egg morphology, and embryonic, larval, juvenile and adult developments. The spawning was found to be year-round with reproductive cycle of 12 to 15 days intervals and laid 300 to 1000 capsule shaped and adhesive type eggs. The eggs were 1.5-3.0 mm in length and 0.8-1.84 mm in width containing multiple oil globules of varying size and were pale yellow or white for initial two days, turned to black on 3rd to 5th day and silvery on 6th to 7th day of incubation