Dr. Godwin's Abstracts e, f, g, & h from his
Bibliographic Publications from 1989-1998

Abstract e: Godwin, J.R. (1994). Behavioral Aspects of Protandrous Sex Change in the anemonefish Amphiprion melanopus and endocrine correlates. Animal Behaviour 48: 551-567.

Behavioural and endocrine differences between males and females, and during protandrous sex change were characterized in the anemonefish, Amphiprion melanopus. Females are the largest and behaviourally dominant members of social groups, displaying frequent aggression towards their smaller male mates and other smaller non-reproductive individuals. Sex change was stimulated experimentally through females removals in 1989 and 1991. Behavioural samples were taken prior to female removal are from 10 to 45 days after removal in 1989 and 1-20 days after re removal in 1991. Sex-changing individuals showed striking increases in aggression within 1 day following female removal. While the frequency of aggressive acts initiated by sex-changing individuals decreased gradually over the 5-, 10- and 20-day samples, it remained significantly elevated over baseline male levels. A decrease in aggression was also observed from 20 to 45 days after female removal in 1989. Presentations of a model intruder to sex-changing individuals at various stages revealed changes to a pattern of territorial defence characteristic of females. Overall aggression increased and the ratio of attacks at the periphery of the territory to those at the centre increased with time after female removal. There was no convincing evidence of a relationship between plasma levels of the five steroids measured and (1) male/female behavioural differences or (2) behavioural changes with sex change.
abstract f: Godwin, J.R. (1995). Phylogenetic and habitat influences on mating systems in the damselfish genus Dascyllus (Pomacentridae, Teleostei). Bulletin of Marine Science 57(3): 637-652.

The damselfish genus Dascyllus contains nine species and exhibits protogynous sex change and/or functional gonochorism with variation both interspecifically and possibly intraspecifically between habitats. The genus can be divided into three species complexes and along lines of both descent and body size: 1) five species in two species complexes (complexes 1 & 2) are relatively small-bodied, closely associate with branching coral throughout life, and commonly exhibit resource defense polygyny and associated protogynous sex change, 2) three species in a third species complex (complex 3) reach larger body size, closely associate with branching coral only as juveniles, and do not exhibit resource defense polygyny, and 3) D. flavicaudus, a large-bodied member of the otherwise small-bodied species complex 2. Dascyllus flavicaudus and D. albisella (complex 3) are both large bodied, but differ in their responses to habitat type. Dascyllus flavicaudus shows differences in sex ratio, space use and mating system between a discontinuous coral cover habitat (female-biased sex ratio, resource defense polygyny) and continuous coral cover habitat (non-biased sex ratio, no resource defense polygyny) while D. albisella does not (non-biased sex ratio, no apparent resource defense polygyny in either habitat type), suggesting that both ecological factors and phylogenetic history influence these characters.
abstract g: Godwin, J. and D. Crews (1995). Sex differences in the estrogenic regulation of estrogen and progesterone receptor messenger ribonucleic acid regulation in the brain of little striped whiptail lizards. Neuroendocrinology 62(3):293-300.

Sex differences in the regulation of steroid hormone receptors in brain areas controlling female- and male-typical sexual behavior may be important in determining sex differences in the display of these behaviors. This study examined sex differences in estrogenic regulation of messenger RNA for estrogen receptor (ER) and progesterone receptor (PR) in discrete brain areas of whiptail lizards, Cnemidophorus inornatus, by in situ hybridization with radiolabeled riboprobes. Gonadectomized females and males received an estradiol benzoate injection (0.5 mg EB) which effectively induces receptive behavior in females; controls received vehicle alone. Sex and regional differences in estrogenic regulation of ER- and PR-mRNA were found. Females responded to EB treatment with increases in ER- and PR-mRNA relative abundance in the ventromedial nucleus of the hypothalamus (VMH). Males had similar relative mRNA abundances to females in gonadectomized controls, but did not exhibit increases with EB treatment. EB treatment increased ER-mRNA abundance in the dorsal hypothalamus of females, but not males. ER-mRNA decreases in the lateral septum and PR-mRNA increases in the posterior hypothalamus with hormone treatment were also found, but did not differ by sex. Neither sex or treatment effects were definitively shown for ER- or PR-mRNA abundance in the anterior hypothalamus-preoptic area. The VMH controls female-typical receptive behavior in this species. Sex differences in the transcriptional response to estrogen in this nucleus may therefore underlie sex differences in the display of receptive behavior. The VMH sex differences described are similar to those in rats, in that females exhibit estrogenic regulation of ER- and PR-mRNA while males do not, suggesting that this pattern is evolutionarily conserved.
abstract h: Young, L.J., J. Godwin, M. Grammer, and D. Crews (1995). Reptilian sex steroid receptors: Amplification, sequence analysis and tissue expression. J. Steroid Biochem. Mol. Biol. 55: 261-269.

Sex steroid hormones secreted by the gonads play a central role in the reproduction of all vertebrates. In addition to direct effects on gametogenesis, sex steroid hormones are important in sexual development, brain organization, and sexual behavior. The actions of sex steroid hormones are mediated primarily by ligand-dependent transcription factors, or receptors which bind to specific sequences of the DNA and alter the transcription rates of nearby genes. We have used the polymerase chain reaction to amplify cDNA fragments of the estrogen receptor, progesterone receptor and androgen receptor from the unisexual whiptail lizard, Cnemidophorus uniparens. The lizard steroid hormone receptors share a high degree of sequence homology to the steroid hormone receptors of other vertebrates. Ribonuclease protection assays demonstrate that both estrogen receptor mRNA and progesterone receptor mRNA are increased in the oviduct during vitellogenesis and after estrogen treatment. This report demonstrates the utility of the polymerase chain reaction to generate species-specific probes for comparative molecular studies and provides the first report of cDNA sequences for reptilian steroid hormone receptors.
End of subsite "jrgabs.e-h.html" for Dr. Godwin's Bibliographic Subsite, which you'll want to return to. Abstract subsite created for him 4-7-97 by J.Kemper. (http://www4.ncsu.edu/unity/users/g/godwin/www/jrgabs.e-h.html)