Meeting Abstract

P2.122  Tuesday, Jan. 5  Effects of methyl farnesoate on cyst production and growth in Triops longicaudatus TRAN, Michael C.*; TSUKIMURA, Brian; California State University, Fresno; California State University, Fresno tranmc@csufresno.edu

Since the discovery of the putative hormone methyl farnesoate (MF), it has been identified in 30 crustacean species, in which it regulates reproduction and morphogenesis (Laufer and Biggers, 2001). In the tadpole shrimp, Triops longicaudatus, MF appears to suppress and delay ovary development in 5-day old juveniles (Tsukimura et al., 2006). This study aims to investigate the effects of MF on ovarian output by looking at total and daily cyst production, while also examining the somatic effects, upon MF ingestion. Two groups of animals were cultured and fed 120 mg of control and MF pellets (6 µg/g) every 24 hours. Average daily cyst production in individuals that survive beyond 5 days of oviposition were similar. The control and MF-treated animals had 76.4±9.9 SEM cysts/day (n=11) and 72.5±7.9 SEM cysts/day (n=13), respectively. However, there was a decline in the total number of cysts produced by MF-treated animals compared to controls, 665.3±98.5 SEM cysts (n=11) to 542.4±66.7 SEM cysts (n=13). The decrease of total cyst production appears to be the result of a decreased number of days of oviposition. MF-treated animals appears to live 1.5 days less compared to control animals, and had a mean of 7.4±0.5 SEM days of oviposition compared 9.0±1.1 SEM in control. The average daily cyst production appears to not be affected by dietary MF, but it may decrease the total cyst production by decreasing in lifespan. Daily administration of MF may also stunt the overall growth of the animal, MF-treated and control animals had growth rates of 0.67±0.1 SEM and 0.75±0.1 SEM mm/day, respectively. This coincides with a previous study, where 5-day old juveniles had a decrease body length and weight after being fed 3.8 µg/g MF-concentrated pellets (Tsukimura et al., 2006).