Social organization and sexual pattern in the Mediterranean parrotfish Sparisoma cretense (Teleostei: Scaridae) |
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Authors: | M de Girolamo M Scaggiante M B Rasotto |
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Institution: | (1) Dipartimento di Biologia, viale G. Colombo 3, I-35131 Padova, Italy, IT |
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Abstract: | We examined the social organization and reproductive pattern of a population of Sparisoma cretense L. at Lampedusa Island (Italy). During the breeding season (July to September) individuals occur either in territorial or
in non-territorial groups, which quantitatively differ with respect to use of space, sex-ratio and sexual activity. Territorial
groups consist of one male plus one to three females, whereas in non-territorial groups as many as 54 fish share a common
area. Among non-territorial groups, variations, in both sex-ratio and behavior, suggest they could represent either feeding
aggregations or reproductive aggregations. Spawning, always in pairs, occurs daily in a short period of time before dusk and
has been observed only in territorial groups. Group spawning has never been observed, but another alternative mating tactic,
streaking on pair spawning, was recorded. In the non-breeding season fish do not aggregate in organized social units. Histological
examination of gonads showed that adults are larger than 12 cm total length. Females have an asynchronous ovary, typical of
species spawning several times during the breeding season. Males show secondary testes, indicating that their gonads develop
ovaries as juveniles, which are later redifferentiated into functional testes. Histological and demographic data seem to indicate
that, as in other species of this genus, prematurational sex-change occurs. The sexual pattern appears to be essentially gonochoristic,
but the potential for sex-change is not excluded.
Received: 5 January 1999 / Accepted: 22 June 1999 |
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