Full-length transcriptome from different life stages of cobia (Rachycentron canadum, Rachycentridae).

Cobia (Rachycentron canadum, Rachycentridae) is one of the prospective species for mariculture. The transcriptome-based study on cobia was hampered by an inadequate reference genome and a lack of full-length cDNAs. We used a long-read based sequencing technology (PacBio Sequel II Iso-Seq3 SMRT) to obtain complete transcriptome sequences from larvae, juveniles, and various tissues of adult cobia, and a single SMRTcell generated 99 gigabytes of data and 51,205,946,694 bases. A total of 8609435, 7441673 and 9140164 subreads were generated from the larval, juvenile, and adult sample pools, with mean sub-read lengths of 2109.9, 1988.2 and 1996.2 bp, respectively. All samples were combined to increase transcript recovery and clustered into 35661 high-quality reads. This is the first report on a full-length transcriptome from R. canadum. Our results illustrate a significant increase in the identified amount of cobia LncRNAs and alternatively spliced transcripts, which will help improve genome annotation. Furthermore, this information will be beneficial for nutrigenomics and functional studies on cobia and other commercially important mariculture species.

Microplastic contamination in commercially important bivalves from the southwest coast of India.

Due to the ever-increasing production of plastic litter and its subsequent accumulation as microplastic in the environment, the pollution caused by microplastics is considered as a global menace, especially in the coastal ecosystem. Occurrence of microplastics in water and three commercially important bivalves, Viz. green mussel (Perna viridis), edible oyster (Magallana bilineata) and black clam (Villorita cyprinoides) from five different locations of southwest coast of India was studied. The highest abundance of microplastics was observed in water samples from Periyar River (163.67 items L-1). Among bivalves, the highest abundance of microplastics was observed in clams from Periyar River (digestive gland: 22.8 g-1; gill: 29.6 g-1), whereas the lowest abundance was observed in mussels sampled from Vembanad estuary (digestive gland: 5.6 g-1; gill: 8.5 g -1). Fibers were the most prevalent type of microplastics found in bivalve tissues across each location. Microplastics less than 2 mm were the most prevalent based on size. Polypropylene and high-density polyethylene were the two types of microplastics observed based on the results of Raman spectroscopy. No relationship was observed between shell length, tissue weight and microplastic abundance. A strong positive correlation was observed between the microplastic presence in water and bivalve tissues. The usefulness of sedentary bivalves in assessing the aquatic pollution has been validated through this study.

Epitope analysis of white spot syndrome virus of Penaeus monodon by in vivo neutralization assay employing a panel of monoclonal antibodies.

A panel of six monoclonal antibodies (MAbs) against the major envelope proteins VP18, VP26 and VP28 of white spot syndrome virus (WSSV) was evaluated for neutralization of the virus in vivo in Penaeus monodon. WSSV stock diluted to 1 x 10⁻6 resulting in 100% mortality on 12 day post injection (dpi) was used as optimum infectious dose of virus for challenge. Constant quantity (100 µg/ml) of MAbs C-5, C-14, C-33, C-38, C-56 and C-72 was incubated separately with WSSV (1 x 10⁻6 dilution) at 27 °C for 90 min and injected to shrimp. WSSV infection was neutralized by the MAbs C-5, C-14 and C-33 with a relative percent survival (RPS) of 60, 80 and 60 on 12 dpi, respectively compared to 100% mortality in positive control injected with WSSV alone. MAbs C-38, C-56 and C-72 could neutralize WSSV infection with RPS on 12 dpi of 40, 30 and 30, respectively. Shrimp injected with WSSV (1 x 10⁻6 dilution) incubated with panel of the MAbs at 100 µg/ml separately were subjected to nested PCR analysis at 0, 8, 12, 24, 36, 48 and 72 hour post injection (hpi) to provide further evidence for neutralization. MAbs C-5, C-14 and C-33 showed delay in WSSV positivity by 24 and 48 hpi by 2nd and 1st step PCR, respectively. MAbs C-38, C-56 and C-72 showed WSSV positivity by 12 and 24 hpi by 2nd and 1st step PCR, respectively. Shrimp injected with WSSV alone showed WSSV positivity by 8 and 12 hpi by 2nd and 1st step PCR, respectively. The study clearly shows that infectivity of WSSV could be delayed by MAbs C-14, C-5 and C-33.