Sexual differentiation,gonad development,and spawning seasonality of the Hawaiian butterflyfish,Chaetodon multicinctus |
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Authors: | Timothy C Tricas Joy T Hiramoto |
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Institution: | (1) Department of Zoology, University of Hawaii at Manoa, Honolulu, HI, 96822, U.S.A.;(2) Present address: Department of Otolaryngology, Washington University School of Medicine, 517 S. Euclid Ave., Box 8115, St. Louis, MO, 63110, U.S.A.;(3) Marine Biological Laboratory, Woods Hole, MA, 02543, U.S.A. |
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Abstract: | Synopsis The reproductive biology of the coral reef butterflyfish,Chaetodon multicinctus, was investigated by histological examination of gonads sampled over an 18 month period from a shallow inshore population
on Oahu, Hawaii. Most gonads developed directly from previously undifferentiated tissue. Ovarian development (the structural
formation of lamellae and primary oocytes) was observed in fish ≥44 mm and testicular development (the formation of spermatogenic
crypts) in fish ≥62 mm standard length (SL). In addition, testis formation was identified within the ovarian lamellae of several
differentiated but immature fish. It is hypothesized that prematurational sex change may facilitate monogamy within the highly
competitive social structure of this site attached species. Oocyte development in mature females was marked by distinct phases
of primary growth, the formation of yolk vesicles, and vitellogenesis. Spawning activity was histologically identified by
the maturation and hydration of fully yolked oocytes, and presence of postovulatory follicles. Recently spawned females from
field collections and experimental gonadotropin-treatments exhibited postovulatory follicles that were estimated to persist
at least 24 h after ovulation. Atresia of yolked oocytes was classified into four stages of cell degeneration and resorption.
Monthly analyses of oocyte development and atresia within the sample population show thatC. multicinctus has a protracted annual spawning season with a major peak during the early spring and evidence of spawning activity among
some individuals in the fall. Histological analyses of spawning activity provide more accurate and unambiguous information
than do traditional gonadosomatic assays in this and probably other coral reef fishes. |
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Keywords: | Chaetodontidae Coral reef fishes Fish reproduction Gonad histology |
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