Orientation behaviour of Pagrus major larvae exposed to UV-B radiation in laboratory conditions.
OBJECTIVE
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.


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/m(2)) 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 5 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
Jai Gopal
JG
Aqua Research Lab, Department of Zoology, University of Delhi, Delhi, India. indian_fish@yahoo.com
Masuda
Reiji
R
Tanaka
Masaru
M
D000818:Animals; D004307:Dose-Response Relationship, Radiation; D007814:Larva / Q000502:physiology / Q000528:radiation effects*; D009949:Orientation / Q000528:radiation effects*; D010473:Perciformes / Q000196:embryology / Q000502:physiology*; D013997:Time Factors; D014466:Ultraviolet Rays