Probiotic potential of a novel endophytic Streptomyces griseorubens CIBA-NS1 isolated from Salicornia sp. against Vibrio campbellii infection in shrimp.

A novel endophytic Streptomyces griseorubens CIBA-NS1 was isolated from a salt marsh plant Salicornia sp. The antagonistic effect of S. griseorubens against Vibrio campbellii, was studied both in vitro and in vivo. The strain was validated for its endophytic nature and characterized through scanning electron microscopy, morphological and biochemical studies and 16SrDNA sequencing. The salinity tolerance experiment has shown that highest antibacterial activity was at 40‰ (16 ± 1.4 mm) and lowest was at 10 ‰ salinity (6.94 ± 0.51 mm). In vivo exclusion of Vibrio by S. griseorubens CIBA-NS1 was studied in Penaeus indicus post larvae and evaluated for its ability to improve growth and survival of P. indicus. After 20 days administration of S. griseorubens CIBA-NS1, shrimps were challenged with V. campbellii. The S. griseorubens CIBA-NS1 reduced Vibrio population in test group when compared to control, improved survival (60.5 ± 6.4%) and growth, as indicated by weight gain (1.8 ± 0.05g). In control group survival and growth were 48.4 ± 3.5% and 1.4 ± 0.03 g respectively. On challenge with V. campbellii, the S. griseorubens CIBA-NS1 administered group showed better survival (85.6 ± 10%) than positive control (64.3 ± 10%). The results suggested that S. griseorubens CIBA-NS1 is antagonistic to V. campbellii, reduce Vibrio population in the culture system and improve growth and survival. This is the first report on antagonistic activity of S. griseorubens isolated from salt marsh plant Salicornia sp, as a probiotic candidate to prevent V. campbellii infection in shrimps.

Gonadal recrudescence and annual reproductive hormone pattern of captive female Spotted Scats (Scatophagus argus).

The Spotted Scat (Scatophagus argus), an important euryhaline fish inhabiting mangrove and coastal regions of Indo-Pacific waters, is both an ornamental and food fish in India. Detailed insight into maturation of Spotted Scat when maintained in aquaculture systems, therefore, needs to be elucidated. Lack of information on annual maturation dynamics of female scat collected from their natural habitat and reared in earthen ponds is the basis of this study. Oocytes were classified into five developmental stages: pre-vitellogenic, vitellogenic, late-vitellogenic, ripe, and follicular atresia. Ovarian maturity stages were subsequently categorized as immature (Stage 1), vitellogenesis (Stage 2), maturing (Stage 3), mature (Stage 4), and spent (Stage 5). In oocytes in primary, secondary and tertiary yolk stages, there are greater concentrations of E2 in vitellogenic females between March and June. Significant increases of E2, T, and 17-OHP paralleled the increase of diameter of late-vitellogenic oocytes in maturing females during July. The completion of vitellogenesis and initiation of germinal vesicle migration in the cytoplasm were evident in mature females (Stage 4) with a decreasing trend of sex steroids in and subsequent to the month of August. There were 50 % of oocytes in the final oocyte maturation stage (FOM) (490-620 µm) until completion of Stage 4 in September. The results of this study indicate there is complete ovarian maturation in female scats captured in their natural habitat and maintained in an earthen pond, which may be important information for hatchery management for induction of spawning of Spotted Scat in aquaculture systems.

Efficacy of exogenous hormone (GnRHa) for induced breeding of climbing perch Anabas testudineus (Bloch, 1792) and influence of operational sex ratio on spawning success.

The climbing perch, Anabas testudineus, is an air-breathing fish having great consumer preference as a food fish and is considered a prime candidate species for aquaculture. Spawning success is an important issue while using hormones for captive induced breeding. In the first experiment, a trial was conducted to assess the efficacy of a synthetic Gonadotropin Releasing Hormone analog (sGnRHa) on the spawning success of climbing perch. Female fish were administered six different doses each with a single intramuscular injection of sGnRHa hormone at 0.002 (TOD1), 0.005 (TOD2), 0.01 (TOD3), 0.015 (TOD4), 0.02 (TOD5), 0.03 (TOD6) µg/g body weight. Similarly, males were administered half of the hormone dose of females in all the respective treatment groups. The greatest (P<0.05) relative fecundity (715.13±15.0 eggs/g female body weight) and fertilization percentage rates (93.1±8.0%) occurred when female fish were treated at the 0.015µg/g body weight dose. There was a reduction in relative fecundity and hatching rate in female fish injected with the largest dose (1.5µL/g body weight) of sGnRHa. A second experiment was conducted to assess the effect of a different male-female ratio on optimum spawning success in climbing perch. For this study a different female to male ratio (1:1, 1:2, 1:3 and 1:4) and male to female ratio (1:1, 1:2 and 1:3) were used. There were a greater (P<0.05) relative fecundity (886.62±17.9 eggs/g female body weight), fertilization (98±6.7%) and hatching (99±5.4%) rates with the female to male ratio of 1:2. This indicated that the hormone dose of 0.015µg/g body weight and a female-male ratio of 1:2 are optimal for enhanced spawning success in the climbing perch.