Sex-role reversal in vertebrates: behavioural and endocrinological accounts

  title={Sex-role reversal in vertebrates: behavioural and endocrinological accounts},
  author={Marcel Eens and Rianne Pinxten},
  journal={Behavioural Processes},
  • M. Eens, R. Pinxten
  • Published 5 October 2000
  • Biology, Psychology, Environmental Science
  • Behavioural Processes

Neuroendocrinology of sex-role reversal.

It is refuted that the most widely tested activational hypothesis for sex differences in androgen secretion is correct; sex-role reversed females do not have higher levels of androgens in circulation than males, however, there is some evidence that the effects of androgen may be sex-specific.

The evolution of sex roles in birds is related to adult sex ratio.

It is suggested that social environment has a strong influence on breeding systems and therefore revealing the causes of ASR variation in wild populations is essential for understanding sex role evolution.

The Role of Androgens in Male Pregnancy and Female Competitive Behavior in a Sex Role Reversed Pipefish

The goal of this dissertation was to examine the role of androgens in the male reproductive cycle and female intrasexual competitive behavior in the sex-role reversed Gulf pipefish, Syngnathus scovelli and develop a model for the hormonal regulation of themale reproductive cycle in seahorses.

Testosterone secretion varies in a sex- and stage-specific manner: insights on the regulation of competitive traits from a sex-role reversed species

It is suggested that the mechanisms regulating competitive traits vary with reproductive role in ways that are unique from gonadal sex.

Progesterone modulates aggression in sex-role reversed female African black coucals

It is shown that territorial aggression in female black coucals is modulated by progesterone, suggesting that progester one may suppress territorial aggression and is downregulated during aggressive encounters.

Hormones and the development of sex differences in behavior

Results of experimental manipulations of sex steroid actions in juvenile zebra finches suggest hormonal regulation of the onset of interest in the opposite sex as sexual maturity is reached, and the concepts of organization and activation raise a number of questions.



Prospects for Sex Role Reversal in Teleost Fishes

This reproductive rates approach should reveal more examples of sex role reversal in teleosts and could contribute to the development of hitherto largely unformulated generalisations about sex differences inteleost fishes.

Sex Roles Are Not Always Reversed When the Potential Reproductive Rate Is Higher in Females

  • N. Okuda
  • Biology, Psychology
    The American Naturalist
  • 1999
The facts that the variance in reproductive success was greater in males and the males developed a sexual trait suggest that sexual selection is acting more strongly on males than on females, suggesting that this fish is not sex‐role reversed.

The Bateman gradient and the cause of sexual selection in a sex–role–reversed pipefish

It is shown that, in the male–pregnant pipefish Syngnathus typhle, females exhibit a stronger positive association between number of mates and fertility than do males and that this relationship responds in the predicted fashion to changes in the adult sex ratio.

Operational Sex Ratios in Seahorses

A study of a laboratory population of the Sri Lankan seahorse Hippocampus fuscus finds that the operational sex ratio (OSR) among mated seahorses is male-biased, because unmated (empty) males can prepare to mate more quickly and can remain ready to mate for longer than can unmated females.

Sex-Role Reversal in the Black-Chinned Tilapia, Sarotherodon Melanotheron (RÜPpel) (Cichlidae)

The prediction of sex role reversal (competitive females and discriminating males) is confirmed by examining competition for mates and mate choice in the black-chinned tilapia, Sarotherodon melanotheron, a paternal mouth brooding cichlid.

Shield Characteristics Are Testosterone-Dependent in Both Male and Female Moorhens

In the moorhen, moorhens implanted with testosterone had higher intensities of ectoparasite infestations than control birds, but other indirect measures of immunocompetence did not differ significantly between the two categories of birds.

Seahorses exhibit conventional sex roles in mating competition, despite male pregnancy

The laboratory experiments in this paper demonstrate that, contrary to expectations, seahorses exhibit conventional sex roles: male seahorse compete more intensely than females for access to mates, on both the first and final days of courtship.

Sexual selection and the potential reproductive rates of males and females

It is shown that among species where males care for the young, the sex with the higher potential reproductive rate competes more intensely for mates than thesex with the lower potential rate of reproduction.

Plasma steroid hormones in relation to behavioral sex role reversal in the spotted sandpiper, Actitis macularia.

The results indicate that the high level of intrasexual competition for mates among female spotted sandpipers is not based upon a total reversal of the normal male/female levels of androgens and estradiol.

Courting females: ecological constraints affect sex roles in a natural population of the blenniid fish Salaria pavo

Evidence for ecological modulation of sex roles in a natural population of the blenniid fish Salaria pavo (Risso) is presented, where nest sites are very scarce, courtship is almost entirely initiated by females, and both male and female intra-sexual competition occurs.