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Inhibition of ovarian development by methyl farnesoate in the tadpole shrimp, Triops longicaudatus
B Tsukimura1, W K Nelson, C J Linder
1Department of Biology, California State University, Fresno, 2555 E. San Ramon Ave. M/S SB73, Fresno, CA 93740, USA. BrianT@CSUFresno.edu
Abstract:
Methyl farnesoate (MF), a putative crustacean hormone, is the immediate precursor of insect juvenile hormone III (JHIII) in the biosynthetic pathway. We examined whether MF, shown to inhibit adult metamorphosis in several crustacean species, is a juvenilizing factor in the tadpole shrimp, Triops longicaudatus. Oocyte production was chosen as a parameter for measuring reproductive development. MF was administered to juveniles by ingestion via biological vector (Artemia nauplii), MF-coated food pellets, and MF liposome food pellets. Artemia were incubated in 30 microl of 5 microg/ml MF. The MF-coated and MF liposome pellets were prepared with MF concentrations ranging between 0.1 microg/g and 10 microg/g MF by weight. Groups of tadpole shrimp were treated with these vectors from the time of hatching for 5 or 10 days in laboratory and field studies. The treatment groups of all the MF vectors showed reductions in oocyte production. Lower concentrations of MF (0.75 microg/g-3.8 microg/g MF) appeared to have a physiological effect on fecundity, but higher concentrations (10 microg/g MF) reduced somatic growth. MF-coated pellets (1 microg/g MF) administered to adults (after 5 days) caused no difference in oocyte production. The observed reductions of fecundity and the disparity of results between MF treatment on juveniles and adults suggest that MF may regulate ovarian development.
Insights
Methyl farnesoate (MF) reduces oocyte production in juvenile tadpole shrimp, indicating it may regulate ovarian development. Higher MF concentrations also inhibited somatic growth in these crustaceans.
Area of Science:
- Endocrinology
- Developmental Biology
- Crustacean Physiology
Background:
- Methyl farnesoate (MF) is a precursor to insect juvenile hormone III (JHIII).
- MF is known to inhibit metamorphosis in several crustacean species.
- Its role in crustacean reproductive development requires further investigation.
Purpose of the Study:
- To determine if methyl farnesoate (MF) acts as a juvenilizing factor in the tadpole shrimp, Triops longicaudatus.
- To investigate the effect of MF on oocyte production and reproductive development in T. longicaudatus.
- To assess MF's impact on somatic growth and fecundity.
Main Methods:
- Juvenile tadpole shrimp were exposed to MF via three delivery methods: Artemia nauplii, MF-coated food pellets, and MF liposome food pellets.
- MF concentrations ranged from 0.1 to 10 microg/g.
- Treatment durations were 5 or 10 days, with studies conducted in laboratory and field settings.
Main Results:
- All MF delivery methods led to reduced oocyte production in juvenile shrimp.
- Lower MF concentrations (0.75–3.8 microg/g) affected fecundity, while higher concentrations (10 microg/g) reduced somatic growth.
- MF administration to adult shrimp did not alter oocyte production.
Conclusions:
- Methyl farnesoate (MF) appears to regulate ovarian development in tadpole shrimp.
- The differential effects on juveniles versus adults suggest MF's role is stage-specific.
- MF's impact on fecundity and growth highlights its potential as a key developmental regulator in crustaceans.
