Reproductive evaluation of triploid yellowtail flounder, Limanda ferruginea (Storer)
2004
Manning, A.J. | Burton, M.P.M. | Crim, L.W.
The reproductive effects of induced triploidy were assessed in 3-year-old yellowtail flounder. Diploids of this small flatfish show a propensity for early sexual maturation in culture. Triploidy was effective in reducing gonadal development in yellowtail flounder, but permitted physiological maturation in both sexes. Triploid males sampled during the regular spawning period in captivity had small testes and variable plasma androgen levels (n = 7; age, 34 months). A limited production of spermatozoa and evidence of spermatogenetic dysfunction were noted histologically. Spermatozoa from triploids exhibited poor or no motility and further demonstrated reduced fertility in fertilization trials with eggs from diploid females. Most larvae resulting from fertilization trials were abnormal and nonviable; however, some triploid males produced a few larvae of normal appearance which may indicate long-term viability. Females sampled at 37 and 40 months of age had small ovaries with varying numbers of oocytes, previtellogenic to vitellogenic, that were developing amid oogonial tissue (oog). Evidence of prior summer ovulatory activity was found in 2 of the 17 females. A high proportion of the remaining 3-year-old females had vitellogenic oocytes and was likely to become fully mature by 4 years of age. Plasma estradiol-17beta (E2) levels were low in triploid females despite the fact that ovarian tissue from pubertal triploids can demonstrate a strong steroidogenic response to gonadotropic stimulation in vitro. The production of triploids will help to reduce the energetic costs of reproduction in the yellowtail flounder.
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