Intergenerational effect of juvenile hormone on offspring in Pogonomyrmex harvester ants

• Published in: Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology Vol. 181; no. 8; pp. 991 - 999
• Main Authors: Cahan, Sara Helms, Graves, Christopher J., Brent, Colin S.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.12.2011; Springer Nature B.V
• Subjects: Age; Animal Physiology; Animal Structures - anatomy & histology; Animal Structures - drug effects; Animals; Ants - anatomy & histology; Ants - drug effects; Ants - physiology; Biochemistry; Biomedical and Life Sciences; Biomedicine; Body size; Body Size - drug effects; Body Size - physiology; Caste determination; Colonies; Ecdysteroids; Ecdysteroids - analysis; Eggs; Female; Females; Formicidae; Genotype; Genotypes; Human Physiology; Insecticides; Juvenile hormones; Juvenile Hormones - analysis; Juvenile Hormones - pharmacology; Larva - genetics; Larvae; Life Sciences; Maternal effects; methoprene; Methoprene - pharmacology; Offspring; Oocytes - cytology; Oocytes - drug effects; Original Paper; Ovarian Follicle - anatomy & histology; Ovarian Follicle - drug effects; Ovary - anatomy & histology; Ovary - drug effects; Pogonomyrmex; Population genetics; Progeny; Pupa - anatomy & histology; Pupa - drug effects; Pupa - physiology; Queens; Reproduction - drug effects; Reproduction - physiology; Temperature effects; Workers; Zoology; Zygote - chemistry; Zygote - cytology; Zygote - drug effects; Harvester ant; Ecdysteroids; Caste; Maternal effect; Social insect; Juvenile hormone
• ISSN: 0174-1578; 1432-136X
• DOI: 10.1007/s00360-011-0587-x

Parents can influence the phenotypes of their offspring via a number of mechanisms. In harvester ants, whether female progeny develop into workers or daughter queens is strongly influenced by the age and temperature conditions experienced by their mother, which is associated with variation in maternal ecdysteroid deposition in fertilized eggs. In many insects, juvenile hormone (JH) is antagonistic to ecdysteroid release, suggesting that seasonal and age-based variation in maternal JH titers may explain maternal effects on offspring size and reproductive caste. To test this hypothesis, we artificially increased maternal JH titers with methoprene, a JH analog, in laboratory colonies of two Pogonomyrmex populations exhibiting genetic caste determination. Increasing maternal JH resulted in a 50% increase in worker body size, as well as a sharp reduction in total number of progeny reared, but did not alter the genotype of progeny reared to adulthood. The intergenerational effect of JH manipulation was not mediated by a reduction in ecdysteroid deposition into eggs; instead, changes in egg size, trophic egg availability or brood/worker ratio may have altered the nutritional environment of developing larvae. Egg ecdysteroid content was significantly negatively correlated with natural variation in worker body size, however, suggesting that there are multiple independent routes by which queens can modify offspring phenotypes.