T3- and T4-induced rates of metamorphosis in immature and sexually mature larvae ofAmbystoma tigrinum (amphibia: Caudata)
✍ Scribed by Norris, David O. ;Platt, James E.
- Book ID
- 102889988
- Publisher
- John Wiley and Sons
- Year
- 1974
- Tongue
- English
- Weight
- 604 KB
- Volume
- 189
- Category
- Article
- ISSN
- 0022-104X
No coin nor oath required. For personal study only.
✦ Synopsis
Rates of Tsand T4-induced metamorphosis in sexually mature and immature tiger salamander larvae (Ambystoma tigrinurn) from a single local population were proportional to daily injected doses (1.0, 10 1, 10 2, or 10 3 pg T, or T4). Larvae were maintained at 16" C on 12L:12D photoperiod, and were fed beef liver daily. Metamorphic rates were compared as the mean number of days to achieve 50% resorption of the gills (GR5J. S a l i n e -~e c t e d and untreated control larvae exhibited no metamorphic tendencies during the experiments. Immature larvae were induced to metamorphose with as little as 0.05 ng T3 or T4/g body weight/day. Small, sexually mature larvae were less sensitive to a given dose of T4, especially at the lowest doses. Large sexually mature larvae did not differ from small larvae. It is presumed that the observed differences in sensitivity would not account solely for the observations of neoteny in this species. Metamorphosis was not influenced by sex. T3 and Tq are equipotent inducers of metamorphosis in immature larvae under conditions of this experiment except that some animals receiving the lowest dose of T S did not undergo metamorphosis.
Larvae receiving 10-1 pg T4/day did not metamorphose at 5" C, and gill resorption was slower for larvae at 10" C as compared to 16" C. GR50 for larvae maintained at 21 C was not different from 16" C.