Abstract
Temporal variations in estradiol-17β (E2) and testosterone (T) levels from initiation to partially spent stages of Fujian oyster, Crassostrea angulata from China were investigated by enzyme-linked immunosorbent assay. E2 concentration varying between 95.97 and 280.98pg/g wet weight in the female gonads was higher than that in the male gonads (P<0.05), while T concentration ranging from 16.06 to 30.09pg/g wet weight in the male gonads was higher than that in the female gonads (P<0.05). Both steroids increased during sexual maturation in females and males respectively, and then decreased markedly after spawning. These findings indicated that the fluctuations in the levels of both steroids were closely related to the reproductive cycle, thus E2 and T could have a role as endogenous modulators in sex determination, development and maturation of C. angulata. In addition, a full-length cDNA (3161bp) encoding a peptide of 744 amino acids of estrogen receptor (ER) from C. angulata was obtained and the similarities of its deduced amino acid sequence to these of other molluscan species were more than 60%. caER mRNA transcript was most abundantly expressed in ovary (P<0.05) and in situ hybridization revealed that the distribution of this gene was expressed exclusively in “auxiliary cells” of ovary. Similar to the variation trends of E2, the expression of caER in the ovary continuously increased from initiation to ripeness stages (P<0.05), and then decreased sharply to the lowest level in the partially spent stage (P<0.05), whereas the caER mRNA transcript of male oyster in the testis maintained a relatively stable low level during the reproductive cycle. These findings suggested that ER may play an important role in the gonad development of oysters.
Published Version
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