Sex Differentiation and Early Gonadogenesis in Sebastes inermis Cuvier

Choi, Hee Jung; Oh, Sung-Young; Myoung, Jung-Goo; Kim, Jong-Man; Hur, Jun Wook; Park, Min-Ouk; Park, In-Seok

doi:10.4217/opr.2008.30.4.401

Cited by 1 publication

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“…One commonality between sablefish sex differentiation and that of most other fishes is the earlier onset of meiosis in females relative to males (Devlin and Nagahama 2002;Strüssman and Nakamura 2002). Delayed onset of meiosis in males relative to females is especially common in long-lived and/or cold-water fishes (Nakamura 1982;Doroshov et al 1997), including rockfishes (Choi et al 2008;Omoto et al 2010). …”

Section: Resultsmentioning

confidence: 99%

Gonadal sex differentiation and effects of dietary methyltestosterone treatment in sablefish (Anoplopoma fimbria)

Luckenbach

Fairgrieve

2015

Fish Physiol Biochem

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Methods for sex control are needed to establish monosex aquaculture of sablefish (Anoplopoma fimbria). Here we conducted the first characterization of sex differentiation by histology and hormonal sex reversal experiment in sablefish. Ovarian differentiation was first discernible at ~80 mm fork length (FL) and characterized by development of lamellar structures and onset of meiosis. Testes exhibited a dual-lobe appearance over much of their length and remained non-meiotic until males were ≥520 mm FL (2 years post-fertilization). Juveniles with undifferentiated gonads were provided diets containing 0 (control), 5 or 50 mg 17α-methyltestosterone (MT)/kg for 2 months. Following treatment, controls possessed either ovaries or non-meiotic testes, whereas MT-treated fish exhibited meiotic testes (60% of the fish), intersex gonads (~30%), or gonads that appeared sterile (~10%). A genetic sex marker revealed that all intersex fish were genetic females, although other females appeared to be completely sex reversed (i.e., neomales). One year after treatment, MT-treated fish possessed non-meiotic testes similar to control males or intersex gonads with reduced ovarian features, presumably due to atresia following MT withdrawal. Milt collected from neomales and genetic males 3 years post-treatment permitted sperm motility analyses; however, neomale sperm were virtually immotile. These results demonstrated that sablefish are differentiated gonochorists and that MT treatment from 76 to 196 mm FL induced permanent masculinization of a portion of the genetic females, but acquisition of sperm motility was impaired. Earlier administration of MT may be necessary to sex reverse a higher proportion of genetic females and reduce negative effects on fertility.

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