Meeting Abstract
P2.141 Wednesday, Jan. 5 The role of methyl farnesoate as a reproductive regulator in the tadpole shrimp, Triops longicaudatus TRAN, Michael C*; TSUKIMURA, Brian; California State University, Fresno tranmc@mail.fresnostate.edu
In the tadpole shrimp, Triops longicaudatus, methyl farnesoate (MF) appears to suppress and delay ovary development in 5-day old juveniles (Tsukimura et al., 2006). This study aims to investigate the amount of cyst production both for daily, and in total, during one life cycle of this organism exposed to dietary MF. Furthermore, we collected cysts produced by these treated Triops, and hatched them in order to determine their viability and if future generations are affected by MF ingestion. Cyst viability was measured by the percentage of hatching. MF decreased cyst production in individuals that survived beyond 5 days of oviposition. The control group laid 92.4 ±4.9 SEM cysts/day, whereas MF-fed animals laid only 79.2 ±4.5 SEM cysts/day (p=0.03). Similarly, the total cyst production was 866.4 ±72.1 SEM cysts for controls compared to 658.4 ±51.3 SEM cysts (p=0.01) for MF-fed animal. The number of days of oviposition between the two groups also showed a decrease; control animals had 9.2 ±0.5 SEM days of oviposition compared to 8.1 ±0.3 SEM for MF-fed (p=0.04). Cyst hatching was performed using two types of containers, glass vials and plastic cups. We hatched cysts collected from control and MF-fed animals, and as an added control, cysts that were hand selected from field soil. In glass vials, controls hatched at an average rate of 24.6% and MF-treated at 26.2%. In plastic cups, control cysts had an average hatch rate of 29.3%, whereas the cysts from MF-fed animals hatched at a rate of 24.7%. Field soil cysts hatched in vials had an average hatch rate of 36.2%, whereas in cups it averaged at 33%. There was no difference in hatch rate between the cysts from control and MF-fed animals. This study provides evidence that MF reduces the fecundity of tadpole shrimps, and supports the hypothesis that MF acts as a juvenilizing factor in pre-adult tadpole shrimp.
