SOCIAL FACILIATION AND SENSORY MEDIATION OF ADULT SEX-CHANGE IN A CRYPTIC, BENTHIC MARINE GOBY

When females of the protogynous gobiid, Coryphopterus glaucofraenum Gill 1863, were removed from their natural social system and isolated from males in all-female groups, the number of females in a group influenced both the proportion of groups exhibiting sex change, as well as the number of females changing sex within groups. Sex change was most prevalent in large, all-female groups; solitary females, however, infrequently changed sex. Therefore, in C. glaucofraenum the presence of other female conspecifics promotes sex change. In the presence of larger male(s), the incidence of sex change among experimental females was either reduced or negated, depending upon the number of females. Sensory isolation experiments revealed the importance of two sensory modalities in the induction and incidence of sex change. Water-borne cues, probably chemical in nature, released by conspecific female groups increased the probability of sex change among solitary females. These induction cues were both sex- and species-specific. In addition, visual cues influenced the number of females changing sex within larger, all-female groups. Visual cues, in the absence of other means of information exchange, appear to play a role in determination of group membership among female C. glaucofraenum. Lastly, while all females within social groups experienced the same sensory cues, usually only the largest female(s) ultimately changed sex. Thus, while sensory cues mediated the timing of sex change, other factors (probably social) likely played a part in determining which individuals within the social group actually changed sex.