Selvaraju Raja

The present study investigates the morphological, molecular, osteological, and evolutionary aspects of freshwater Bagrid catfish in the Western Ghats of India, focusing on the Cauvery River basin. Samples from three genera of the Bagridae family, namely Hemibagrus, Sperata, and Mystus, were collected from the Cauvery and Bhavani rivers. The study aims to assess the diversity and threatened status of Bagridae catfishes in the region, identify morphological discrimination using mitochondrial DNA (mtDNA), analyze phylogenetic relationships, and understand their evolutionary process from common ancestries. Morphological and meristic characterization was performed, and genetic analysis was conducted using the cytochrome oxidase subunit 1 (COX1) gene. DNA was extracted from tissue samples, amplified using specific primers, and sequenced. The study highlights the need for taxonomic revision of Bagridae catfishes in the Western Ghats, as previous classifications were primarily based on morphometric analysis, leading to confusion and invalid species claims. The findings contribute to a better understanding of the diversity, taxonomy, and evolutionary history of Bagrid catfishes in the Western Ghats, which is crucial for their conservation, as more than 50% of the species are threatened with extinction due to various factors such as pollution, biological resource use, and habitat modification.

In freshwater fish culture, water quality poses a serious hazard to survival and growth. To understand this high-risk factor associated with the poor water quality in the aquarium system, the hematological, histological, immunological, antioxidant, and growth performance of C. auratus, C. carpio, and P. hypophthalmus in the aquarium with different water treatment efficiencies and one without water filtration were compared. The experiment was conducted for approximately 120 days using water treatments: 1. PF, 2. BF, 3. PBF, 4. PBUVF, 5. WoF. Results showed that Fish health concerning turbidity (98%) was significantly reduced during post-filtration (PF, BF, PBF, and PB-UV-F) (p<0.05). In experimental tanks, water-treated fish showed improved growth and a 90% survival rate (p<0.05). In pot and bamboo filters, the hematological parameters such as RBC (93%, 94%, and 93%), WBC (79%, 18%, and 91%), and MCHC (93%, 45%, and 90%) were in the optimum levels during post filtration experiment. The immune response (IgM, C3, C4, NOS, and LSZ) of enzyme activities in the gut and liver of aquarium fishes and antioxidant parameters in the gut and liver (ABTS, CAT, GR, SOD, and LPO) were also the low-risk level where the water treatments in the aquarium tanks. In conclusion, our findings show that installing filtration systems in freshwater fish culture has helped to successfully regulate the fish health and water quality of aquariums and ensure their proper maintenance.

This study examined the effects of Tribulus terrestris and Basella alba on sex reversal in the guppy, Poecilia reticulata. This study aimed to introduce a new environmentally friendly method for masculinization in P. reticulata. Since male guppy has higher commercial value than females. T. Terrestris (ET) and Basella alba (EB) are a natural, non-toxic herb that helps enhance testosterone levels in humans and animals. Different concentrations (0.0, 5.0, 10.0, and 15.0 g L-1) of ET and EB were investigated for sex reversal in P. reticulata. The plant extracts were administered by immersion of newly hatched offspring once a week for two months. The dosage of 15.0, g L-1 ET was the most effective dosage that ensured a maximum male ratio (82.0, p0.05). Total survival rates in all treatments and control were uniformly high ranging from 92% and 97% (p>0.05). It is concluded that ET has no negative effect on the survival rate of P. reticulata. All groups of ET-treated fish exhibited growth acceleration compared to the control group, but only ET treatment at the concentration of 15 and 10 g L-1 ET significantly improved growth rate of P. reticulata (p<0.01). Histological examinations revealed that the testes of fish treated with ET and EB extract contained all stages of spermatogenesis. Sex reversal in P. reticulata demonstrated that ET and EB-treated progenies showed successful sex reversal, spermatogenesis, and better growth rate than untreated progenies.

The filtration of aquarium wastewater composed of a pot and bamboo is constructed for the purification of microbial activities and to reduce turbidity. The aquarium wastewater is treated with sand to reduce BOD and COD; the usage of coconut husk and vetiver act to decrease the turbidity, nitrite, and pH while raising DO level. Initially, sand was sieved to produce 12 size ranges between 180 and 2000 m. The effectiveness of each range in removing turbidity, BOD, and COD through sand beds 4 or 5 cm deep were tested. The critical size (300 & 425 m) at which no solid particles could penetrate through the sand bed was observed at 3 and 4 cm in depth, respectively. Moreover, the flow of solids through sand filter beds had all particles smaller than 180 m removed from them. A 2 cm bed of sand allowed 0.2-0.5% of solids to flow through, and a 4 cm bed allowed 0.07-0.1 %. Both fine and coarse sand layers are supported by a layer of gravel. In the column approach, the thickness and flow rate of each layer were fixed. The thickness of the layers of sand and charcoal were fixed at 4 cm and 6 cm, respectively. The findings of the column analysis, the combined filter showed decreases in turbidity by 48%, COD by 52%, BOD by 30%, and increasing DO by 48%, respectively. The results reveal that absorbing nutrients can serve as bio-filters to create better conditions for fish growth. The final weight, length, and SGR of fishes in the three aquariums were significantly different after seven weeks of trial, the treated aquarium showed the highest value than the control.

The descriptive and comparative osteological analysis was conducted on Bagridae catfish S. aorides based on the specimens collected from the Cauvery River Basin in Tamil Nadu. S. aorides with a supraoccipital spine that is equal to or longer than the inter-neural shield with 26 pre-caudal vertebrae and has the first dorsal fin pterygiophores that are externally visible and united anteriorly rather than being distinct. The supra-occipital spine had the same width from base to tip with a broader base. The groves in the skull serve as the primary osteological indicator and serve as the morphological marker. The neuron cranium, upper and lower jaws, pectoral and pelvic girdles, and the vertebral column were among the bones whose structures were described based on the findings.

Mass production, consumption, and disposal of plastics pollute the freshwater environment. Microplastics are small plastic particles less than 5mm in diameter that enter the ecosystem as a result of the breakdown of large plastic particles or the direct release of small plastic particles by climate and human activities. This study focused on investigating the spatial, and seasonal dispersal of microplastics in the surface water of Kumaraswamy Lake, Coimbatore which is located at the Latitude of 110’00.52'' N, Longitude of 76056’42” E. In different seasons, such as summer, pre-monsoon, monsoon, and post-monsoon samples were taken from the inlet, centre, and outlet. Microplastics made of linear low-density polyethylene, high-density polyethylene, and polypropylene were found in all sampling points. From the water samples, fibre, thin, fragments, and film shapes of microplastics were identified and most of them were black, pink, blue, white, transparent, and yellow in colour. The lake's microplastic pollution load index values were less than 10, which implies the risk I category. Microplastic concentration over four seasons was 8.77 ± 0.27 particles per liter and a high distribution was observed in the outlet area (10.70 ± 0.25 particles/L). Seasonally, the highest microplastic concentration was found in the monsoon season followed by pre-monsoon, post-monsoon, and the lowest in the summer season. These results emphasize that the distribution of microplastics spatially and seasonally wise may cause harmful effects on the fauna and flora that live in lake habitats.

Organic reduction of nanomaterials is an inexpensive and ecologically feasible method. The major challenge of this method is its optimization to improve efficiency. The reduction of metal ions with the conjugation, involves either through extraction from natural materials like plants, algae, fungus, and bacteria or by the action of micro-organisms (intracellular synthesis of these particles). The present investigation deals with the green synthesis of silver nanoparticles (SNPs) reduced by Spirulina platensis. The reduced nanoparticle synthesized by the microorganism was materialized to inhibit the pathogenic Vibrio parahaemolyticus isolated from the aquaculture system of Tamil Nadu. The highest percentage of distribution of V. parahaemolyticus was recorded in the farm water collected from shrimp farms of Nagapattinam than in the Cuddalore district. The presence of secondary metabolites in qualitative estimation and GCMS revealed the presence of 32 compounds in both acetone and methanol extract. The essential fatty acids eicosane was found to have antibiotic potency against shrimp infected with pathogenic bacteria. The synthesized Spirulina SNPs were characterized using UV-Vis spectrophotometer, EDAX, XRD, TEM and SEM. The analysis revealed a spherical structure without any agglomerates whose reduction absorption was at 200–450 nm. The good diffusion method showed inhibition of human and marine pathogen V. parahaemolyticus, exhibiting an inhibitory zone at 15.30 ± 2.21 and 15.19 ± 2.48 mm respectively. Thus, the Spirulina-mediated silver nanoparticles are found to be a simple, economical, and eco-friendly biomaterial to be a potent antibiotic against the pathogenic bacteria found in shrimps.