Histological evidence of lunar-synchronized ovarian development and spawning in the spiny rabbitfish Siganus spinus (Linnaeus) around the Ryukyus
Fisheries
Science, 67(5): 888-893
Abstract:
This
study clarifies the annual reproductive cycle and the lunar-synchronized
spawning of the spiny rabbitfish (Siganus spinus) that inhabit the
Okinawan waters. Annual and weekly changes in the gonadosomatic index (GSI)
and the histological features of the ovaries were checked. Gonadosomatic
index was high during the months of May to July, and yolk-laden oocytes were
observed in the ovaries from March to July. Some of the ovaries collected
during June and July contained oocytes at maturation stage or ovulatory
follicles. These results suggest that the spiny rabbitfish undergo active
vitellogenesis and spawning from May to July. During the reproductive season
(May to July), collection of fish according to the lunar phase revealed that
a high GSI occurred around the time of the new moon. Cyclic oocyte
development with peaks around the time of the same moon phase was also
observed, suggesting that, in Okinawan waters, this species is a
lunar-synchronized spawner and spawns three times.
(Sesoko
Station, Tropical Biosphere Research Center, University of the Ryukyus,
Motobu, Okinawa 905-0227, Japan, Tel: 81-980-47-2888. Fax: 81-980-47-4919. Email: tilapia@lab.u-ryukyu.ac.jp)