Aggressive behavior and serotonin immunoreactivity in nile tilapia (Oreochromis niloticus Linn) following exposure to chlorpyrifos insecticide

Issue Date

10-2009

Abstract

Two treatment sets were established to determine the effects of exposure to chlorpyrifos at varying residual levels and lengths of exposure on the aggressive behavior and brain serotonin level of Nile tilapia. The dominant fish was characterized as having red-colored dorsal fins while the subordinate fish had dark body coloration that appeared zebra-like. No significant skin darkening was noted among the fishes exposed to residual concentrations of chlorpyrifos while fishes exposed to 1.6 ug/L chlorpyrifos at different exposure periods showed that skin coloration is dependent on length of exposure. The aggressive observed was characterized by tail chasing, side butting and uncoordinated movements such as lateral swimming with the body touching the bottom of the tank close to the wall while the dominant fish swims freely and often attacking the subordinate ones. Serotonin immunoreactive (5HT-IR) structures were generally found in 4 areas of the tilapia brain - telencephalon, diencephalons, mesencephalon and brain stem. A negative correlation between the number of 5HT- IR neurons and the different residual concentrations of chlorpyrifos was observed. Histopathological examination showed hepatocytes with lipid droplets and degenerative hepatocytes characterized by destruction of cytoplasm and absence of nuclei. No significant relationship between the exposure period and the number of agonistic encounters was established. The number of 5HT-IR neurons was found to be related to the length of exposure to the chlorpyrifos than to dose levels. Likewise, less aggressive individuals were found to have less 5HT-IR neurons.

Source or Periodical Title

Philippine Entomologist

ISSN

0048-3753

Volume

23

Issue

2

Page

200

Document Type

Article

Frequency

semi-annually

Language

English

En – AGROVOC descriptors

OREOCHROMIS NILOTICUS; SEROTONIN; CHLORPYRIFOS; INSECTICIDES; BEHAVIOUR; AGGRESSIVE BEHAVIOUR

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