Comparative Biochemistry and Physiology Part A 122 (1999) 85 – 92
Estrone and estradiol-17 concentration in tissue of the scleractinian
coral, Montipora errucosa
Ann M. Tarrant
a,
*, Shannon Atkinson
b
, M.J. Atkinson
b
a
Department of Oceanography, Uniersity of Hawaii at Manoa, Honolulu, HI 96822, USA
b
Hawaii Institute of Marine Biology, Uniersity of Hawaii at Manoa, P.O. Box 1346, Kaneohe, HI 96744, USA
Received 11 June 1998; accepted 5 October 1998
Abstract
Spawnings of scleractinian corals are affected by light, temperature, and other environmental cues, but no studies elucidate
physiological mechanisms that regulate coral gametogenesis. We hypothesized that estrogens may act as bioregulators of coral
reproduction. Estrone (E
1
) and estradiol-17 (E
2
) concentrations were measured in homogenates of tissue and skeleton from M.
errucosa. Tissue samples were collected monthly throughout the year, and more frequently in July and August around spawning.
Steroids were extracted with diethyl ether, purified via celite chromatography and assayed with radioimmunoassay. Non-specific
binding in coral tissue varied with sample weight and was elevated relative to standards. Monthly mean E
1
ranged from 20–70
ng E
1
g ash-free dry weight (AFDW)
-1
, with highest values in April. Smaller asynchronous peaks occurred in early July, prior
to spawning. Monthly mean E
2
ranged from 8–25 ng E
2
g AFDW
-1
, with highest values in February and March. Peaks in E
2
preceded peaks in E
1
, indicating metabolism of a pool of estrogen. E
1
was positively correlated with protein concentration, which
is consistent with a bioregulatory role of estrogens. Estrogen peaks in spring and prior to the July spawn corroborate our
hypothesis that estrogens regulate coral gametogenesis and spawning. © 1999 Elsevier Science Inc. All rights reserved.
Keywords: Coral; Estradiol; Estrone; Gametogenesis; Hawaii; Invertebrate; Steroids; Scleractinia
1. Introduction
Steroids occur throughout the animal kingdom as
ancient and highly conserved regulators of reproduc-
tion [24]. Estrogens act through receptors to effect
tissue hydration and cellular proliferation in target
cells; they are essential to development of reproductive
organs in most, if not all, female vertebrates. Estrogens
and other steroids that are biologically active in verte-
brates have also been found in invertebrates, including
echinoderms [29], crustaceans [28], and molluscs [18,21];
however, mechanisms of steroid action are poorly un-
derstood in these species. Concentrations of C
21
(progestins) and C
18
(estrogens) steroids in the gonads
and pyloric caeca of asteroids vary predictably during
annual gametogenic cycles [13,25,29,30]. Similarly, the
concentrations of C
21
,C
19
, and C
18
steroids in female
Artemia sp. varied among individuals but also peaked
during specific stages of egg development [28]. Peaks in
steroid concentrations during gametogenesis support
the hypothesis that steroids act as bioregulators of
reproduction in invertebrates.
Estradiol-17 (E
2
) has been measured using radioim-
munoassay (RIA) in coral eggs and seawater collected
during a coral mass-spawn in Western Australia [3]. In
addition, RIA has facilitated measurement of estradiol,
progesterone, androstenedione, and testosterone in al-
cyonacean soft corals [26]. Cnidarians also contain a
variety of C
25
–C
30
sterols, but origin and function of
these compounds have not been elucidated [7,12,16].
Cytochrome P-450 and associated mixed function oxi-
dase enzymes have been measured in the Caribbean
scleractinian, Faia fragum, indicating the potential of
* Corresponding author. C/o M.J. Atkinson, Tel.: +1 808 236
7422; fax: +1 808 236 7443; e-mail: atarrant@soest.hawaii.edu
1095-6433/99/$ - see front matter © 1999 Elsevier Science Inc. All rights reserved.
PII S1095-6433(98)10155-1