The freshwater aquatic biodiversity is depleting alarmingly due to the introduction of exotic species and other anthropogenic activities. The indiscriminate transfer of exotic fishes has brought about a wide array of problems including extirpation of indigenous species. The exotics compete with the indigenous species for food, habitat and may even prey upon them, introduce new parasites and diseases, result in the production of hybirds and cause genetic 'erosion' of indigenous species and degradation of the physico-chemical nature of aquatic ecosystems. The potential risks not only affect the biodiversity, but also the socioeconomic aspects of the human community that depend on aquatic ecosystems for their sustenance. The paper reviews the impact of exotic fishes on aquatic biodiversity in India and the measures to check this.

The present investigation was carried out to isolate and characterize bioactive components from Mirabilis jalapa L. radix (紫茉莉根 zǐ mò lì gēn). Thin-layer chromatography was used for the separation of spots from fractions of the crude extract. Separated spots were collected for identification of their activities. Free-radical scavenging activity was evaluated by spraying thin-layer chromatography plates (spotted with fractions) with 0.2% of 2,2-diphenyl-1-picrylhydrazyl solution. Activity against human pathogens such as Staphylococcus aureus and Candida albicans were determined using the agar diffusion method. Potential spots were subjected to infrared (IR) analysis and gas chromatography for characterization. Two spots (5F1 and 1F3) showed free-radical scavenging activity. The 1F3 spot was active against both S. aureus and C. albicans, whereas the 5F1 spot was active against S. aureus only. IR spectral analysis indicated that 5F1 spot to be a triterpenoid. Using IR spectral analysis and an IR library search, the 1F3 spot was identified to be a flavone, which may have a hydroxyl group in ring “A” of the flavone nucleus. Our results indicated that the 1F3 and 5F1 spots are potential free-radical scavengers. Both 1F3 and 5F1 exhibited antimicrobial activity. IR spectral analysis coupled with an IR library search indicated 1F3 and 5F1 to be a flavone and a triterpenoid, respectively.

Survival and growth of tiger shrimp (Penaeus monodon) at three salinity levels, 5, 10 and 15 g/L were investigated in potassium deficient natural inland saline water (PD-ISW) and potassium supplemented inland saline water (PS-ISW). Shrimps reared in PS-ISW survived well, whereas total mortality occurred in PD-ISW. The survival at 45 and 60 days at the salinities of 5, 10 and 15 g/L was assessed in PS-ISW. The supplementation of potassium showed significant effect on the survival rates at different salinities. Length-weight studies at different salinities and periods of time in PS-ISW showed significant differences in the linear component, but there was no significant difference in respect to interaction of salinity and rearing periods in a two-way ANOVA repeated measures. Growth parameters indicated that a salinity of 10 g/L was best for the survival and growth of shrimps in inland saline water of the site with potassium supplementation. Individual cations and ratios between other cations were found to be equally important for survival and growth. The results of the present study will be useful in utilizing degraded ISW sites for the culture of tiger shrimp.

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Heteropneustes fossilis (Bloch) is an important candidate species for diversification of freshwater aquaculture in India. However, high mortality rate during larval rearing is the most serious bottleneck in commercial production of this species. A proper understanding of the ontogenic development of digestive system provide the basis to understand the nutritional physiology of larvae and develop appropriate feeding strategies. In the present study, the ontogenical development of the digestive tract in H. fossilis larvae was studied from hatching until 30 day post hatching (dph) at 29 ºC. At hatching (2.8 ± 0.2 mm standard length, SL), the digestive tract was undifferentiated and attached dorsally to the yolk sac. At 1 dph (2.9 ± 0.2 mm SL), the mouth opened and oral valves were visible.At 2 dph (3.0 ± 0.3 mm SL), goblet cells were observed in the buccoparyngaeal cavity. At this age, exogenous feeding started and the intestine was differentiated into the anterior and posterior regions, and the rudimentary liver and pancreas were also seen. Small supranuclear vacuoles were observed in the enterocytes of the posterior intestine at 2 dph. Zymogen granules were observed in acinar cells of pancreas by 3 dph and islets of Langerhans were be visible at 4 dph (3.5± 0.1 mm SL). At the same age, most of the yolk sac reserves were consumed, whereas they were completely exhausted by 5 dph (3.9 ± 0.5 mm SL). Between 4 and 6 dph, the liver elongated in size and started to accumulate lipids in the hepatocytes. Gastric glands were detected at 4 dph, and the pyloric sphincter was completely differentiated at 9 dph (6.1 ± 0.4 mm SL) as an epithelial fold that separated stomach from the anterior intestine. By 13 dph (8.6 ± 0.2 mm SL), profuse gastric glands were visible inside longitudinal mucosal folds of the stomach. The formation of gastric glands and their development was noticed as the last events in the development of the digestive tract in H. fossilis. This indicated the end of the larval period and the commencement of the juvenile stage. Considering these observations, it is suggested that H. fossilis larvae have a morphologically complete digestive tract by 13 dph. The findings of the study on the development of the digestive system in H. fossilis may help in synchronizing the larval stage of development and feeding strategies, and would be helpful in improving larval rearing techniques for catfish species.