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Biomedical subjects

D Crews

Publications and source records attributed to D Crews.

197 records · Page 11Linked to original sources
PubMed1979

Effects of intracranial implantation of oestradiol and dihydrotestosterone on the sexual behaviour of the lizard Anolis carolinensis.

Intrahypothalamic implantation of oestradiol and dihydrotestosterone rapidly restored sexual behaviour in castrated, sexually inactive Anolis carolinensis. Implants in areas other than the anterior hypothalamus-preoptic area failed to elicit sexual behaviour. Male aggressive behaviour was unaffected by intracranial hormone implants. Histological examination of the renal sex segment, a secondary sex structure, gave no indication of leakage into the peripheral plasma. The effectiveness of oestradiol and dihydrotestosterone in inducing male courtship behaviour when administered intracranially was compared with the relative ineffectiveness of systemic injections of these hormones.

Aggression↗
PubMed1978

Hormonal control of male reproductive behavior in the lizard, Anolis carolinensis: role of testosterone, dihydrotestosterone, and estradiol.

The androgen aromatization hypothesis was examined in the male lizard, Anolis carolinensis. After castration, sc silastic implants of testosterone (T) restored both challenge and courtship behavior, while dihydrotestosterone (DHT) or 17beta-estradiol (E) had no effect on male behaviors. Both T and DHT, but not E, stimulated hypertrophy and colloid production by the renal sex segment, a secondary sexual characteristic of male lizards. In two separate studies, castrates received DHT in combination with E. In each replicate, half of the castrates responded with increases in courtship behavior after hormone treatment. Epithelial cell height of the sex segment of all DHT and E-treated castrates was comparable to T- or DHT-treated castrates, but colloid production was not stimulated. These experiments indicate that in this species, treatment with T stimulates both sexual behavior and secondary sex character development, whereas treatment with E alone is without effect centrally or peripherally.

Animals↗
PubMedDate not supplied

Female mimicry in garter snakes.

In many diverse taxa, males of the same species often exhibit multiple mating strategies. One well-documented alternative male reproductive pattern is 'female mimicry', whereby males assume a female-like morphology or mimic female behaviour patterns. In some species males mimic both female morphology and behaviour. We report here female mimicry in a reptile, the red-sided garter snake (Thamnophis sirtalis parietalis). This form of mimicry is unique in that it is expressed as a physiological feminization. Courting male red-sided garter snakes detect a female-specific pheromone and normally avoid courting other males. However, a small proportion of males release a pheromone that attracts other males, as though they were females. In the field, mating aggregations of 5-17 males were observed formed around these individual attractive males, which we have termed 'she-males'. In competitive mating trails, she-males mated with females significantly more often than did normal males, demonstrating not only reproductive competence but also a possible selective advantage to males with this female-like pheromone.

Animals↗