| Summary: | 碩士 === 國立臺灣海洋大學 === 海洋環境與生態研究所 === 106 === Sexual reproduction is among the most important biological phenomenon required for
establishing coral populations. To date, most studies regarding coral sexual
reproduction have focused on the environmental factors affecting coral gametogenesis
and spawning. However, little studies have been performed on the intrinsic
mechanisms underlying coral sexual reproduction. Sex steroids in vertebrates play
fundamental roles in gametogenesis and spawning. Previous studies found that stony
coral tissues contain sex steroids (e.g., 17beta-estradiol, testosterone). Interestingly,
the concentration of 17beta-estradiol in the coral tissue elevated when the coral
approached to the spawning month in the stony coral Euphyllia ancora. These
findings suggest that sex steroids may be involved in the regulation of gametogenesis,
oocyte maturation, and/or spawning in corals. However, the elevation in the
concentration of 17beta-estradiol has only reported in E. ancora, it is still unclear that
similar patterns can be observed in other corals. To get a better understanding of the
function of steroids in the sexual reproduction, especially in germ cell development,
of the stony corals, the present study investigated the relationship between
gametogenesis and sex steroids using a stony coral Goniopora burgosi. G. burgosi
colonies were collected at Pitouchiao near northern Taiwan at different timings over
the periods during October 2016-December 2017. The germ cell development was
investigated by immunohistochemical analysis with anti-Piwi (germ-cell marker)
antibody. The sex steroids (17beta-estradiol, progesterone, and testosterone) in the
tissue extract of G. burgosi were determined by UPLC-MS. We found that the germ
development took approximately one year in both sexes. It started from August and
proceeds until the next spawning periods, July or August. UPLC-MS analysis
confirmed the presence of progesterone and testosterone in the most coral tissue that
we examined. However, the concentration of these steroids in the coral tissues were
basically very low throughout the year, and the distinct elevation in the levels of these
steroids were not observed even in the corals that approached to the spawning month.
Further studies were required to clarify the function of steroids in in germ cell
development of the stony corals.
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