ABSTRACT
The Cauvery carp Barbodes carnaticus (syn. Puntius carnaticus), an endemic and threatened species of the Western Ghats, was once commercially important species in the Krishnaraja Sagar reservoir, Mysuru but later became scarce due to exploitation. In this study, we attempted conservation and rehabilitation of this species. We raised wild-caught juveniles of Barbodes carnaticus to gonadal maturity in ponds, where male and female took 2 and 3 years to reach first maturity. The females exhibited a higher gonado-somatic index (GSI) than males. Sexing was accomplished based on morphological characteristics and subsequently the fish was induced to ovulate/spawn with ready-to-inject spawning agents viz. ovatide, ovaprim and human chorionic gonadotropin (HCG). The order of performance was ovatide >ovaprim >HCG. The ovatide-injected female produced higher relative fecundity (1462 eggs/kg body wt.) than the females administered ovaprim (814 eggs/kg body wt.). The ripe oocytes had a diameter of 0.98 mm, and the water-hardened eggs were of 1.90 mm. The injected fish responded to hormones between15 and 30 h at 25.6-28.5ºC. The fertilization rates were generally high (50-100%). However, the hatch rates were low (0-27%). The quantity of yolk-sac fry obtained was higher in ovatide trial (336 fry/kg body wt.) than the ovaprim trial (293 fry/kg body wt.). The performance of HCG was much lower than that of ovatide and ovaprim. The early development of B. carnaticus from activation of egg to yolk-sac absorption stage was recorded using live eggs, embryos and early fry. Five embryonic steps (blastodisc formation, cleavage, epiboly, organogenesis and blood circulation) and free embryo consisting of five larval steps were identified. Hatching occurred between 37 and 48 h (post-activation), the free embryo period lasting up to 5 days post-hatching. The transition from larva to juvenile occurred in 25 days when the fish were fully scaled and the lateral line organ clearly visible, with a distinct black blotch on caudal peduncle. A few deformed eggs with asymmetrical cleavage and embryos with yolk-sac malformations, spinal cord and tail curvatures were observed. When the fry were reared in manured and fed pond, they showed faster growth, reaching fingerling stage (3.5 g; 7.5 cm) in 50 days, with more than 95% survival. Spermatozoa motility duration (13-60 s) and percentage (16-63%) were moderate, while the spermatozoa density and spermatocrit were high
ABSTRACT
Norethindrone(NE) was evaluated for its efficacy on alteration of sex ratio of P. reticulata. Either the young fry or the brooders and the resultant fry were fed a commercial diet incorporated with NE at 0, 25, 50, 75 and 100 mg kg-1 diet (ppm) for 30-40 d in rectangular glass aquaria; this was followed by 40-60 d rearing on NE-free diet in out-door concrete tanks. In general, the androgen treatment altered sex ratio, leading to the production of a dose dependent increase in the percentage of males. The oral administration of the steroid at 75 ppm for 40 d or 100 ppmfor 30 or 40 d to first feeding fry, yielded 100% males. On the other hand, NE administration to brooders before parturition and the resultant fry also produced an all-male population of guppy. The sex ratio of the untreated control was almost 1:1. The survival of fish in all the trials was high, ranging between 67 and 100%. Mating masculinized males (“XX” male) with normal female resulted in an all-female progeny, while crossing normal male (XY) from treatment groups with normal female sired normal sex ratio (1:1), elucidating XX-XY sex determination system in the guppy.