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

摘要

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 'check' 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.