Sublethal effects of carbaryl on embryonic and gonadal developments of zebrafish Danio rerio

  • PK Mensah
  • GE Okuthe
  • M Onani


Carbaryl is a broad-spectrum insecticide used to control insect pests. In aquatic environments, it can disrupt the endocrine system and adversely affect the reproductive function of aquatic animals. This study investigated sublethal impacts of carbaryl on embryos and gonads of zebrafish Danio rerio in order to assess the pesticide’s impact on its reproduction. Fertilised embryos were exposed to 1.7 mg l–1 carbaryl until hatching, while larvae aged 10 days post hatching were exposed to 0.1, 0.2, 0.4, 0.8 and 1.7 mg l–1  carbaryl concentrations until 50 days post hatching (dph). Treatments were applied in a static renewal system and all experiments involved watesupr only and a solvent control. At the end of 50 dph, all surviving fish were sacrificed and processed for light microscopy. Results indicated a mean hatching success rate of 92.5% for control groups, while embryos exposed to carbaryl recorded an 81.0% success rate. Sex reversal was delayed in the experimental groups, with a sex ratio of 13 females to 0 males, but the control group recorded 6 females to 8 males. These results suggest that sublethal doses of carbaryl in the environment, similar to those used in the current study, may have an adverse effect on the reproductive success of zebrafish.

Keywords: carbamate insecticide, embryo development, sex ratio, water quality

African Journal of Aquatic Science 2012, 37(3): 271–275

Author Biographies

PK Mensah
Department of Zoology, Walter Sisulu University, Private Bag X1, Mthatha 5117, South Africa; Current address: Unilever Centre for Environmental Water Quality, Institute for Water Research, Rhodes University, PO Box 94, Grahamstown 6140, South Africa
GE Okuthe
Department of Zoology, Walter Sisulu University, Private Bag X1, Mthatha 5117, South Africa
M Onani
Department of Chemistry, University of Western Cape, Private Bag X17, Bellville 7535, South Africa

Journal Identifiers

eISSN: 1727-9364
print ISSN: 1608-5914