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
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 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 fishery.
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 fluorescent lamps fixed above the tank, (ii) one fluorescent lamp on the left side, one fluorescent lamp and one UV-B lamp on the right side, and (iii) one UV-B lamp and one fluorescent lamp on the left side, one fluorescent lamp on the right side of the tank. Results: In the first treatment, 7-and 20-day-old larvae were significantly (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, significantly (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, significantly (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 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 fish 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 fish 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 fish 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 significantly (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.
Sharma, J .G., Rao, Y. V., Kumar, S. and Chakrabarti, R. 2010. Impact of UV-B radiation on the digestive enzymes and immune system of larvae of Indian major carp Catla catla. International Journal of Radiation Biology 86: 181-186.
Purpose: Ultraviolet radiation is a potent threat to the aquatic animals. Exposure to such stressor affects metabolic and immunological processes. The present investigation aims to study the effect of UV-B radiation on digestive enzymes and immunity of larvae of Catla catla.
Materials and methods: Larvae were exposed to ultraviolet-B (UV-B, 280–320 nm) radiation (145 μW/cm2) for three different exposure times of 5, 10 and 15 min on every other day. After 55 days, important digestive enzymes were assayed. For immunological study, lysozyme, glutamate oxaloacetate transaminase (GOT) and glutamate pyruvate transaminase (GPT) levels were measured. Then the fish were kept for one month without radiation and lysozyme level was measured.
Results: Protein concentration varied directly with the duration of exposure and was highest among fish that had received the 15 min UV-B irradiation. Significantly higher amylase, protease, trypsin and chymotrypsin activities were found in 5 min exposed fish compared to others. Lysozyme level was significantly higher in control group compared to the UV-B treated fish. The lysozyme level decreased with the increasing duration of UV-B radiation. When fish were kept without UV-B radiation for one month, lysozyme level was brought to the normal level in all treatments, except 15 min exposed fish. The GOT and GPT levels were significantly higher in the 15 min exposed group than others.
Conclusions: The effects of UV-B radiation on the digestive physiology and immune system of catla have been clearly observed in the present study. The decreased enzyme activities in UV-B radiated fish results into improper digestion and poor growth.
