Abstract
Mediterranean razorfish, Xyrichthys novacula, were collected between July and December in a sandy bay of Ponza Island (Central Mediterranean Sea) to investigate the effects of reproduction and growth patterns on sexual inversion processes and haremic territoriality. The minimum body size of males decreased from 17 cm in July to 15 cm (T.L.) in October as a consequence of the sexual inversion after reproduction. Females showed a reproductive peak in August using both the Holden and Rait scale and the gonodosomatic index. The gonads of males were small, on average only 0.14% of total body weight. The proportion of body weight devoted to gonads did not change with male size. This is probably a consequence of the haremic mating system of the species which reduces sperm competition between males. A new coloration phase for females was introduced in addition to the three already described in the literature. Individuals of each age class are characterised by different coloration patterns. This chromatic feature of the species allows dominant males to recognize the age of females and consequently to choose during harem formation the older and larger specimens able to produce a larger number of offspring.
Highlights
The Mediterranean razorfish Xyrichthys novacula (L., 1758) is a benthic wrasse found on sandy bottoms at depths ranging from 1 to 50 m
Females showed a reproductive peak in August using both the Holden and Rait scale and the gonodosomatic index
This chromatic feature of the species allows dominant males to recognize the age of females and to choose during harem formation the older and larger specimens able to produce a larger number of offspring
Summary
The Mediterranean razorfish Xyrichthys novacula (L., 1758) is a benthic wrasse found on sandy bottoms at depths ranging from 1 to 50 m. A species with a population structured in this way is defined as polygynous In such a species, as Victor (1987) stated, a dominant male can monopolise females in two different, but not mutually exclusive ways: keeping other males away from the resources of his territory essential to females (resource defence polygyny) or merely defending the females of his territory from males (female defence polygyny). Ethological studies on Xyrichthys novacula (Terao et al, 1991; Marconato et al, 1995) have indicated that the Mediterranean razorfish is a haremic species in which dominant males defend the females of their territory from the mating attempts of others males
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