Zoological Studies

Vol. 48 No. 4, 2009

Sexual Reproduction in Transplanted Coral Fragments of Acropora nasuta

Nami Okubo1,*, Hiroki Taniguchi2, and Makoto Omori2

1Japan Society for the Promotion of Science/ Seto Marine Biological Laboratory, Field Science Education and Research Center, Kyoto University, Shirahama, Nishimuro, Wakayama, 649-2211 Japan
2Akajima Marine Science Laboratory, 179 Aka, Zamami-son, Shimajiri-gun, Okinawa, 901-3311 Japan

Nami Okubo, Hiroki Taniguchi, and Makoto Omori (2009) The survival rate and sexual reproduction were examined after fragmentation and transplantation of the reef-building coral Acropora nasuta.  Fragments of 2 different lengths, of approximately 5 and 10 cm, were transplanted onto a reef substrate in July 2001 (n = 85 at 5 cm and 71 at 10 cm) and Feb. 2002 (n = 66 at 5 cm and 66 at 10 cm), corresponding to the early and late vitellogenic stages of oocyte development, respectively.  Oocyte development, fecundity, and spawning, were monitored over a 3 yr period.  Oocyte development was influenced by both fragment size and season of transplantation.  In smaller fragments, oocytes were resorbed, while development continued in larger fragments, suggesting that smaller fragments could not afford to invest in sexual reproduction and converted resources from oocytes into growth/survival.  Oocytes of July-transplanted fragments (in the early vitellogenic stage) were resorbed, while oocytes of Feb.-transplanted fragments (in the late vitellogenic stage) continued to develop.  This may have occurred because of the large amount of energy needed for further oocyte development in Julytransplanted fragments until spawning in June of the following year.  Transplanted fragments spawned in the 1st year; none, except for 1 fragment, spawned in the 2nd year; and no gametes were produced in the 3rd year, indicating that fragments reallocated energy resources, and that infertility occurred for a certain period of time.

Key words: Fragmentation, Conservation, Fragment size, Season, Sexual reproduction.

*Correspondence: E-mail:namiokubotitech@yahoo.co.jp