Delayed Effects Of An Insect Growth Regulator Methoprene On Embryos Of The Grass Shrimp Palaemonetes Pugio
No Thumbnail Available
Links to Files
Permanent Link
Collections
Author/Creator
Author/Creator ORCID
Date
2016
Department
Biology
Program
Master of Science
Citation of Original Publication
Rights
This item is made available by Morgan State University for personal, educational, and research purposes in accordance with Title 17 of the U.S. Copyright Law. Other uses may require permission from the copyright owner.
Abstract
The delayed sublethal toxic effects of an insect growth regulator (IGR) methoprene on the grass shrimp Palaemonetes pugio, were determined using a short term predictive bioassay (GSELTOX- Grass Shrimp Embryo-Larval Toxicity) test. Both excised embryos and embryos attached to the females (ovigerous females) were exposed to sublethal concentrations of the pesticide methoprene. The method involves single pulse exposure of embryos to sublethal concentrations of toxicant and seawater or acetone controls for four days followed by transfer to seawater for the rest of the embryonic development until hatching. Different sublethal toxicity endpoints were measure at the larval stage such as: embryo survival, hatchability, larval abnormalities, larval behavior (swimming and phototaxis) and larval viability (hatch to day four, H-D4). Various life stages (larvae, post larvae, non-spawning adults, and ovigerous females) of the grass shrimp were used in acute toxicity tests. Chronic effects of methoprene on larval grass shrimp were also determined. Static renewal exposure system was used for both acute and chronic tests. For post larvae, non-spawning adults, and ovigerous females, methoprene was not found to be acutely toxic at nominal concentrations up to 40 ppm. In addition, there was no acute toxic effect on the larval grass shrimp up to 1000 ppb of methoprene. However, continued exposure of larvae up to post larvae resulted in decrease in the survival from 97.5% in seawater control down to 42% at 1000 ppb of methoprene. For all sublethal tests, the larval viability (H-D4) was the most sensitive to methoprene at all test concentrations (0.5 ppb to 80 ppb). For all embryonic stages used (stage IV, 6-d old (Body Segment stage), stage V, 8-d old (Embryonic Eye Stage), and stage VI, 10-d old (Compound Eye Stage); there was concentration depended response for larval viability. In the larval chronic and sublethal embryonic tests; NOEC (no observed effect concentration) could not be determined. While, the LOEC (lowest observed effect concentration) was determined as 5 ppb in the larval chronic test, and 0.5 ppb in sublethal embryonic test. Hence, the embryonic test was ten times more sensitive than the larval chronic test.