Phenotypic plasticity in sex allocation for a simultaneously hermaphroditic coral reef fish.

Phenotypic plasticity can facilitate reproductive strategies that maximize mating success in variable environments and lead to differences in sex allocation among populations. For simultaneous hermaphrodites with sperm competition, including Serranus tortugarum a small coral reef fish, proportional male allocation (testis in total gonad) is often greater where local density or mating group size is higher. We tested whether S. tortugarum reduced male allocation when transplanted from a higher density site to a lower density site. After 4 months, transplants mirrored the sex-allocation patterns of the resident population on their new reef. Transplants had significantly lower male allocation than representatives from their source population, largely as a result of reduced testis mass relative to body size. © 2011 Springer-Verlag

Otolith-check formation and accelerated growth associated with sex change in an annual protogynous tropical fish

Growth of the haremic sandperch Parapercis cylindrica (family Pinguipedidae) was examined in relation to sex change using otolith microstructure and gonad histology. The influence of previous growth history on the timing of sex change and which individuals underwent sex change were also explored. Examination of otolith increments shows that P. cylindrica has a maximum longevity of 411 d, which is reduced in a lower latitude population. P. cylindrica is a monandric hermaphrodite, with males being larger than females at any given age. An abrupt optical discontinuity or Œcheck¹ on sagittal cross-sections was found to be associated with sex change. This check appears to be formed at the initiation of sex change. Growth rate following sex change, inferred from otolith increment widths, increased markedly and more than doubled in some individuals. Individuals retained accelerated growth for a period of up to 30 d, after which time growth rate declined. Larval growth, relative size at metamorphosis, juvenile growth, and female growth (all determined from otolith microstructure), did not influence which individuals changed sex, or the timing of their sex change. Evidence suggests that sex change and subsequent growth acceleration in these haremic fish are influenced by the strong size-based social hierarchy in which they live

Growth acceleration, behaviour and otolith check marks\ud associated with sex change in the wrasse Halichoeres miniatus

In protogynous sex-changing fishes, females are expected to compete for the opportunity to change sex following the loss of a dominant male and may exhibit growth and behavioural traits that help them maintain their dominant status after sex change. A male removal experiment was used to examine changes in female growth and behaviour associated with sex change in the haremic wrasse Halichoeres miniatus and to test whether any changes in growth associated with sex change were recorded in otolith microstructure. Dominant females began displaying male-characteristic behaviour almost immediately after the harem male was removed. The frequency of interactions between females increased following male removal. In contrast, feeding frequency of females decreased. The largest one to three females in each social group changed sex following male removal and exhibited an increase in growth associated with sex change. Sex changers grew more than twice as fast as non-sex changers during the experimental period. This growth acceleration may enable new sex-changed males to rapidly reach a size where they can defend the remaining harem from other males. An optical discontinuity (check mark) was present in the otoliths of sex-changed fish, and otolith accretion rate increased significantly after the check mark, corresponding with the increased growth rate of sex-changing females. Wild caught males, but not females, exhibited an analogous check mark in their otoliths and similar increases in otolith increment widths after the check. This indicates that an increase in growth rate is a regular feature of sex-change dynamics of H. miniatus

Relative size-at-sex-change in parrotfishes across the Caribbean: is there variance in a supposed life-history invariant?

Invariant life-history theory has been used to identify parallels in life histories across diverse taxa. One important invariant life-history model predicts that, given simple assumptions and conditions, size-at-sex-change relative to maximum attainable body size (relative size-at-sex-change, RSSC) will be invariant across populations and species in sequential hermaphrodites. Even if there are broad pecies-wide limits to RSSC, populations could fine-tune RSSC to local conditions and, onsequently, exhibit subtle but important differences in timing of sex change. Previous analyses of the invariant sexchange model have not explicitly considered the potential for meaningful differences in RSSC within the confines of a broader ‘invariance’. Furthermore, these tests differ in their geographical and taxonomic scope, which could account for their conflicting conclusions. We test the model using several populations of three female-first ex-changing Caribbean parrotfish species. We first test for species-wide invariance using traditional log–log regressions and randomisation analyses of population-specific point estimates of RSSC