Puberty visualized: sexual maturation in the transparentCasperzebrafish

Abstract

SummaryTransparentCasperzebrafish allow studies of vertebrate sexual maturation and gonad developmentin vivo.Caspergonad dynamics can be observed longitudinally over time and non-invasively. Gonad maturation and reproduction are complex processes subject to disruption by endocrine-disrupting chemicals (EDCs), such as diethylstilbestrol (DES). DES was used as a ‘proof of principle’ to ascertain the usefulness of theCaspermodel to determine EDC effects on gonad maturation. Puberty onset in control juvenileCasperzebrafish (N= 43) averaged 13.2 weeks post fertilization (WPF) for females and included increased vent size, while in males puberty occurred at 11.7 WPF along with maintenance of small vents. DES treatment for 6 days in early juveniles (N= 20) induced an average delay in puberty of 5 weeks in females and 10 weeks in males. DES induced loss of breeding tubercles and vent enlargement in post-pubescent males. Puberty in control fish was correlated with an average body length of 1.7 cm for males and 1.8 cm for females. Increased testes opacity, small vent and breeding tubercles denoted male puberty. Puberty in females was defined as ovarian follicle diameters reaching 400 µm with increasingly opaque follicles and by an increased vent size. These results are like those for wild-type zebrafish and indicate that theCaspermodel is a useful system for studying gonad dynamicsin vivo. Future use of transgenic reporter lines inCasperwill allow new avenues of investigation into the reproductive biology of this vertebrate model.