Aqua Research Lab

Sharma, J. G., Masuda, R. and Tanaka, M. 2005. Ultrastructural study of skin and eye of UV-B irradiated ayu Plecoglossus altivelius. Journal of Fish Biology (The Fisheries Society of the British Isles) 67: 1–7.

A scanning electron microscopic study of the skin and eye of UV-B radiated ayu Plecoglossus altivelius (age 30 days, mean±S.E. total length: 16.25±0.11 mm) under laboratory condition showed marked changes when compared with the control fish without UV-B radiation. The exposure of the fish to the radiation resulted in the destruction of microridges in the epidermis and exposed neuromast cells of the skin. Domed protrusions were also more common in the skin of UV-B radiated fish than in the control fish. The appearance of mucus in both groups was different. In the control skin the mucus was spread over a wide area whereas in the treated fish the mucus was concentrated in a small area. The anastomozing structures of the microridges of the eyes were lost in UV-B radiated fish and the microridges themselves were fewer in number, fragmented, and aggregated. Mucus cells, prominently visible in the control fish, were distorted in the treated fish. Cell contours were irregular in UV-B radiated fish and cell to cell contacts had been lost in this group.

Sharma, J. G. and Chakrabarti, R. 2006. Effects of UV-B radiation on the gills of Catla catla during early development. Toxicological & Environmental Chemistry(Taylor & Francis) 82: 367-371.

Scanning electron microscopic study of gills of Catla catla catla (17-day-old) exposed to UV-B radiation (145 µW/cm² at the water surface) for three different exposure times: 5, 10 and 15 min was conducted. Fish without UV-B exposure served as control. UV-B radiation damaged both gill filaments and lamellae. The intensity of damage was minimal in 5 min exposed fish, followed by 10 min exposed fish and maximal in 15 min. The gill epithelium was severely damaged in 15 min irradiated fish compared to control. Pavement cells (PVCs) were damaged and the numbers of microridges within PVCs decreased. The deep, boundary of PVC was not clear. In some area of gill epithelium, PVCs were destroyed and mitochondrion-rich cells (MRCs) were exposed. The 5 min exposure reduced the number of microridges in the pavement cells, but the boundary of PVCs was still visible. MRCs in the gill epithelium were not exposed in 5 min exposed fish. The damage to PVCs and subsequent exposure of MRCs in UV-B irradiated fish may hamper respiratory functions and disturb osmoregulation in catla.

Sharma, J. G., Masuda, R. And Tanaka, M. 2007. Orientation behaviour of Pagrus major larvae exposed to UV-B radiation in laboratory conditions. International Journal of Radiation Biology 83: 49-52.

Purpose: The increasing intensity of ultraviolet-B (UV-B) radiation is a potential threat to the aquatic environment. The recognition capacity of the aquatic animals may help them to avoid this harmful radiation. The response of individual species, especially during early development may help to understand the vulnerability of that species and its potentiality in natural ?shery. Materials and methods: The orientation behaviour of red sea bream Pagrus major larvae exposed to UV-B radiation (280 - 315 nm) was studied within the laboratory (1.41 W/m2) under following experimental conditions: (i) two ?uorescent lamps ?xed above the tank, (ii) one ?uorescent lamp on the left side, one ?uorescent lamp and one UV-B lamp on the right side, and (iii) one UV-B lamp and one ?uorescent lamp on the left side, one ?uorescent lamp on the right side of the tank. Results: In the ?rst treatment, 7-and 20-day-old larvae were signi?cantly (p < 0.0095) higher in number at the right side than left and middle regions of the tank. Some 33 - 60% of larvae were found in the middle region of the tank at the age of 30 - 32 days. In the second treatment, signi?cantly (p < 0.0034) lower numbers of larvae (10 - 13.3%) were found in the middle region of the tank compared to the other sides between days 17 and 20, whereas 40 - 86.67% larvae were found in the middle region between days 25 and 36. In the third treatment, signi?cantly (p < 0.015) higher numbers of larvae were found in the right side at the age of days 17 - 25 and in the middle region between days 32 and 36. Conclusions: This study showed that UV-B sensitivity of P. major developed during ontogenic development. Care should be taken at early stages.

Sharma, J. G., Mittal, P. and Chakrabarti, R. 2008. Development of survivorship model for UV-B irradiated Catla catla larvae. Aquatic Ecology (Springer) 42: 17-23.

A survivorship model was developed for UV-B irradiated Catla catla (17 days) larvae with the help of Kaplan and Meier Product-Limit (PL) method. Larvae were exposed to UV-B radiation (145 µW/ cm2) for three different exposure times: 5, 10 and 15 min on every other day. The mean survival time of ?sh was calculated for each treatment using uncensored and censored survival data during 74 days study period. The mean uncensored and censored survival data for the 5-min exposed ?sh were 7 and 43, respectively. In 10-min exposure period, the uncensored and censored survival data were 19 and 31, respectively. During maximum exposure of 15 min, the uncensored survival data was 20 and censored data was 30. The mean survival time of ?sh calculated using PL estimate in 5, 10 and 15 min exposure treatments were 69.61 ± 0.50, 65.25 ± 0.96 and 60.60 ± 1.55 days, respectively. The mean survival time showed a decreasing trend with the increase of exposure period. The survival time was signi?cantly (P < 0.001) higher in 5-min exposure treatment than others. This is clear from the present study that the exposure of UV-B radiation affects the survival rate of surface feeder catla larvae.