NELSON, W.K.; LINDER, C.J.; TSUKIMURA, B.: Effect of Methyl Farnesoate Incorporated into Feed on the Development of Tadpole Shrimp, Triops longicaudatus

Triops longicaudatus, inhabitants of ephemeral pools, have a short life cycle, being reproductive one week after hatching. This life cycle was useful to examine the effects of methyl farnesoate (MF), a putative crustacean hormone, as a possible reproductive regulator. MF-laden shrimp pellets were developed at 0.0001% and 0.001% MF concentrations by weight and created by mixing MF with 20% Tween-20, then sprayed this mixture onto commercial pellets (35% protein). Tadpole shrimp gonads were examined after 5 days (when gonadal reproduction has commenced) and at 10 days (when ovoposition has commenced). Pellets containing 0.0001% MF significantly reduced fecundity in 5- and 10-day-old (oocyte number or ovarian weight, respectively) tadpole shrimp without affecting somatic growth. However, the 0.001% MF concentration significantly reduced oocyte number/ovarian weight and also reduced somatic development. This was assumed to be a toxic event. MF appears to inhibit ovarian development at physiological concentrations when administered to juveniles. We also attempted to incorporate MF into “home-made” pellets containing a standard mixture of lecithin, wheat gluten and casein. MF was incorporated into the feed at 0.0001% and 0.00001% by weight. These pellets are air-dried at ambient temperature. Similar quantities of MF-pellets were provided developing tadpole shrimp as before. We found that these pellets had no effect on either reproductive or somatic growth. There was significantly less MF retained in these pellets and may be the reason for their ineffectiveness. California Agricultural and Technology Institute – Agricultural Research Initiative funded this research.