A K A Nazar

On the Recurrence of Coral Bleaching and Recovery in North Bay, Port Blair, Andaman and Nicobar Islands

Coral cover, live-form categories, bleaching and their recovery were monitored in North Bay, South Andaman during pre- and post-tsunami periods. The reef is a fringing type, with a total coral cover of 313,382 m2. The total live and dead coral percentages recorded prior to tsunami were 29.4% and 27%, respectively. A patchy bleaching of 7.5% was recorded in month of April–May 2005. However, the coral reef started to recover quickly, and as much as 4.7% of recovery was recorded, and 2.8% of the bleached coral failed to recover. No significant variations in the physicochemical parameters were recorded prior to and post-tsunami. A sudden change in the water column height due the land subduction caused by the mega earthquake on 26 December 2004 was evident. The sudden change in depth and light penetration might have exerted a stress in the corals, leading to expulsion of zooxanthellae from the gastrodermal layer of cells, causing the bleaching phenomena.

Isolation and characterization of pathogenic Vibrio alginolyticus from sea cage cultured cobia (Rachycentron canadum (Linnaeus 1766)) in India

Mass mortalities of cobia, Rachycentron canadum, sub‐adults occurred during August 2013 in cage culture in the Gulf of Mannar, Mandapam Tamil Nadu, India. The epizootic of disease was started with typical classical clinical signs followed by acute mortality. Grossly, severe haemorrhage and congestion were observed in the gastric mucosa. The abdomen was distended with peritoneal fluid. The heart revealed haemopericardium and fibrinous pericardium. Histologically, the gastric mucosa showed severe erosion and necrosis. Haemorrhagic pericarditis and an increased size of the melano macrophage centre (MMC) in the tail kidney were other histopathological changes. Vibrio sp. was isolated from the gastric lesions and heart blood swab of moribund fishes and it was found to be virulent to the cobia fingerlings. After the challenge, the same bacterium could be re‐isolated from moribund fingerlings. The 16S ribosomal RNA of the isolate was amplified and blast analysis of the sequence confirmed that the pathogen was Vibrio alginolyticus. The confirmation was also correlated with its cultural, biochemical and pathomorphological changes. This is the second report and the first incidence of epizootics with severe pathological lesions in cultured cobia in India. The study throws light on the pathology of vibriosis. By practising cage farm management measures, occurrences of infection may be prevented.

A record of a bifid rostrum in the penaeid shrimp Parapenaeopsis hardwickii (Miers, 1878) (Decapoda, Penaeidae) from Palk Bay, Tamil Nadu, India

Abnormal changes in the morphology of the appendages and body segments in decapods crustacean have long been noticed in the wild (Fauvel, 1900), including duplication of structures (Rudolph, 1996; Nakatani et al., 1997), lack of such structures (Kulkarni et al., 1980), reversal of asymmetry (Stevens & Munk, 1991) and deformed sexual appendages (Rodriguez & Campos, 2000). In shrimps, abnormalities of the rostrum have often been reported (De Grave, 1999) and mostly deal with a significant increase in size of the rostrum or in rostral teeth number (Ayub & Ahmed, 1991). Variations in the rostral shape, teeth number or shape and length have been further noticed in several species, e.g., Penaeus penicillatus Alcock, 1905, Penaeus merguiensis De Man, 1888 and Metapenaeus affinis (H.Milne Edwards, 1837) (Ayub & Ahmed, 1991). The present study report the rostral deformity in Parapenaeopsis hardwickii for the first time from Palk Bay