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Vol. 47 No. 1, 2008
The Smallest Oocytes among Broadcast-Spawning Actiniarians
and a Unique Lunar Reproductive Cycle in a Unisexual Population of the
Sea Anemone, Aiptasia pulchella (Anthozoa: Actiniaria)
Chienhsun
Chen1,2,3, Keryea Soong3, and Chaolun Allen Chen1,2,*
1Institute
of Oceanography, National Taiwan University, Taipei 106, Taiwan
2Research Center for Biodiversity, Academia Sinica,
Nankang, Taipei 115, Taiwan
3Institute of Marine Biology, National Sun Yat-Sen
University, Kaohsiung 806, Taiwan
Chienhsun
Chen, Keryea Soong, and Chaolun Allen Chen (2008) Aiptasia
pulchella, an aquarium species and invasive pest, is used as a common
model actinarian for laboratory-based experiments to study
environmental regulation of asexual reproduction, mutualism of
cnidarian-dinoflagellate intracellular symbiosis, and cnidarian
bleaching mechanisms. In this study, gametogenesis and the
reproductive cycle of A. pulchella were studied in a population from
the outlet of Tungkang Marine Station, southern Taiwan using
histological sections. Samples were taken on a monthly basis in
1993 and 1994, and at 6 d intervals in Aug. to Oct. 1997. Additional
sampling was conducted in 1998 to examine the relationship between
sexuality and body size. Among the 211 individual sea anemones
examined, only females (n = 173) and non-reproductive (n = 38) anemones
were observed; no male individuals were recorded throughout the course
of these sampling periods. Gonads of A. pulchella females were located
in one of the paired primary mesenteries and two of the paired
secondary mesenteries. The body size of A. pulchella was
significantly larger in individuals with developed gonads in both
primary and secondary mesenteries compared with those with developed
gonads only in the primary mesenteries and with sterile
individuals. The mature oocytes of A. pulchella, which ranged
60-100 µm in diameter, are the smallest recorded among broadcasting
actiniarians. Gametogenesis in this unisexual population of A.
pulchella followed the lunar cycle, and spawning occurred between the
24th and 29th lunar days year round, which is also first reported for
actiniarians.
Key words: Gametogenesis,
Unisexual population, Aiptasia pulchella, Lunar cycle, Smallest oocyte.
*Correspondence: Tel: 886-2-27899549. Fax:
886-2-27858059. E-mail:cac@gate.sinica.edu.tw
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