Abstract
Male dung beetles (Onthophagus taurus) facultatively produce a pair of horns that extend from the base of the head: males larger than a threshold body size develop long horns, whereas males that do not achieve this size develop only rudimentary horns or no horns at all. Using topical applications of methoprene, we identified a sensitive period during the feeding stage of third (final) instar larvae when application of methoprene shifted the threshold body size for horn expression. Male larvae that received methoprene at this time delayed horn production until they attained a larger threshold body size than acetone-treated control larvae. This new sensitive period occurs earlier than a sensitive period previously reported for male horn regulation, and it coincides with a morph-specific pulse of ecdysteroid secretion described for this species. It appears that male horn expression is influenced by endocrine events at two different periods of larval development. We incorporate these results into an expanded model for the endocrine regulation of male horn expression.
Original language | English |
---|---|
Pages (from-to) | 1045-1054 |
Number of pages | 10 |
Journal | Journal of Insect Physiology |
Volume | 47 |
Issue number | 9 |
DOIs | |
State | Published - 2001 |
Keywords
- Horned beetle
- Juvenile hormone
- Male dimorphism
- Polyphenism
- Threshold