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EFFECTS OF THE INSECT JUVENILE HORMONE AGONIST, METHOPRENE, ON FEMALE GROWTH AND REPRODUCTION IN THE GULF SAND FIDDLER CRAB.
Citation:
Tuberty, S. R., S. F. Nates, H. Zhong, AND C L. McKenney Jr. EFFECTS OF THE INSECT JUVENILE HORMONE AGONIST, METHOPRENE, ON FEMALE GROWTH AND REPRODUCTION IN THE GULF SAND FIDDLER CRAB. Presented at e-hormone 2001 Conference, New Orleans, LA, October 18-20, 2001.
Description:
Adult Uca panacea were collected from the shores of West Bay Point near Panama City, Florida, in late April of 2000. These crabs (250 females, 100 males per pond) were distributed randomly into six specially constructed estuarine ponds to determine the effects of field applications of the insect juvenile hormone agonist, methoprene (AltosidO XR briquets) on female growth and reproduction. Duplicate reference ponds, low-dose ponds (22 g AltosidO briquet/pond/application) and high-dose ponds (44 g AltosidO briquet/pond/application) were utilized. Monthly sub-samples were collected by pitfall trapping May-October 2000, and April 2001. Methoprene exposure had a negative impact on the reproductive potential of the exposed crabs. Mean carapace width (CW) and wet weights increased from 13.82 ? 1.10mm and 1.04 ? 0.26g in May, respectively, to 17.41 ? 1.19 mm and 2.32 ? 0.30g the following April. Secondary vitellogenesis (VTG), indicative of advanced egg maturity, was observed in all classes greater than or equal to 15 mm CW. The peak mean ovarian index (OI) occurred in August, followed in September by a precipitous decline, due to hatching of the young from the attached egg mass. Females that were exposed to methoprene exhibited increased percentages of secondary VTG in June and July 2000. Both exposure levels, however, resulted in reduced percentages of total vitellogenic females (primary plus secondary VTG) from August 2000 to April 2001. Reduced OI were observed in the low-dose and high-dose crabs (-16% and -10.2%, respectively) relative to the reference group at its peak of ovarian maturation in August 2000. The April 2001 sample showed 23.8% and 75% reductions in OI, 10.6% and 25% reductions in total number of vitellogenic females, and 29.5% and 50% reductions in number of secondary VTG females in the low and high dose groups, respectively, as compared with the April 2001 reference group. Reduction in the number of reproducing females and OI (as related to fecundity) affected by exposure to methoprene could seriously diminish the reproductive potential of crabs chronically exposed to environmentally relevant concentrations of this widely used juvenile hormone analog.