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 Editorial
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Vertebrates
Reproductive biology of Halichoeres nigrescens, the bubblefin wrasse?
by Valerie C.M. Ho
A great variety of sexual patterns is exhibited by the teleosts. Labrids are generally gonochorists or protogynous hermaphrodites (Kobayashi and Suzuki 1990, Shibuno et al. 1993, Sadovy and Cornish 2000). Any species that functions as only male or female throughout life is considered to be gonochoristic. Sequential change of sex from female to male (protogyny) can be further subdivided into two forms, monandry (all males derive from sex changing females) and diandry (some males derive from juveniles, others from sex-changing adult females).
The family Labridae is one of the best studied groups of fish for protogynous hermaphroditism and this sexual pattern is better known in this family than in any other (Kobayashi and Suzuki 1990; Shibuno et al. 1993; Gillander 1995). Little is known of the reproductive cycle and sex succession in the life history of Halichoeres nigrescens, however, although it is a very common species in Hong Kong waters and the most common wrasse (Sadovy and Cornish 2000). This summer I had the chance to inspect some slides of the gonads of H. nigrescens taken from throughout the year. This article describes the reproductive biology of bubblefin wrasse. These data may be relevant to the management of H. nigrescens and provide reference for further research.
The sex and size frequency distributions fit the general labrid pattern of size and sex distribution indicating that H. nigrescens is a protogynous hermaphrodite. The fact that no males are found at smaller sizes suggests that all males are derived from females, i.e. monandry. The inspection of monthly data of the various maturity stages by sex revealed that the fish become mature from May to September inclusive as indicated by the dominance of vitellogenic (i.e. yolky) oocytes. The species has a spawning season that lasts for three months. This contrasts with the year-round spawning in some tropical species as suggested by Warner and Robertson (1978). A distinctive feature is observed in the inactive mature male. Sperms in the early developing stage aggregate in lobules with tails oriented towards the centre. This feature is lost later when the gonads become ripe close to spawning. The significance of this to the biology of the species requires further investigation.
This work was conducted as part of a summer project. Taking up this project was a challenge for me, because I knew nothing on this topic. In the end, I overcame all the difficulties and managed to come out with a story. If I could have also collected samples and prepared slides, it would have made my job more complete but I was working with samples already collected and prepared I wish to thank Dr. Sadovy for giving me this opportunity to explore and provide me the guidance and support throughout my job.
Note: Funding for Valerie’s summer research position was provided by proceeds from the sale of Sadovy and Cornish, 2000, initially funded by the Hong Kong Jockey Club.
Bibliography
Gillanders, B.M. (1995) Reproductive biology of the protogynous hermaphrodite Achoerodus viridis (Labridae) from south-eastern Australia. Mar. Freshwater Res. 46: 1009-20.
Kobayashi, K. & Suzuki, K. (1990) Gonadogenesis and sex succession in the protogynous wrasse, Cirrhilabrus temmincki, in Suruga Bay, Central Japan. Japan. J. Ichthyol 37(3): 256-264.
Sadovy, Y. & Cornish, A. (2000) Reef Fishes of Hong Kong. Hong Kong University Press pp. 200-216.
Shibuno, T., Chiba, I., Gushima, K., Kakuda, S. & Hashimoto, H. (1993) Reproductive behavior of the wrasse, Halichoeres marginatus, at Kucherabu-jima. Japan. J. Ichthyol 40(3): 351-359.
Warner R. R & Robertson, D.R. (1978) Sexual patterns in the labroid fishes of the western Caribbean, I: The Wrasses (Labridae). Biological Bulletin 181: 199-204.
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