Puberty visualized: sexual maturation in the transparent Casper zebrafish

Area of Science:

• Reproductive Biology
• Endocrinology
• Aquatic Toxicology

Background:

• Transparent Casper zebrafish provide a unique in vivo model for observing vertebrate sexual maturation and gonad development non-invasively.
• Gonad maturation and reproduction are complex processes susceptible to disruption by endocrine-disrupting chemicals (EDCs).

Purpose of the Study:

• To ascertain the usefulness of the Casper zebrafish model for determining the effects of EDCs on gonad maturation.
• To use diethylstilbestrol (DES) as a proof of principle to assess EDC impacts.

Main Methods:

• Juvenile Casper zebrafish were treated with DES for 6 days to observe effects on puberty onset and characteristics.
• Control and treated groups were monitored for puberty indicators such as vent size, breeding tubercles, and ovarian follicle development.

Main Results:

• Puberty onset in control females averaged 13.2 weeks post fertilization (WPF), and in males, 11.7 WPF.
• DES treatment delayed puberty by an average of 5 weeks in females and 10 weeks in males.
• DES also induced loss of breeding tubercles and vent enlargement in post-pubescent males.

Conclusions:

• The Casper zebrafish model is effective for studying gonad dynamics and the effects of EDCs in vivo.
• Results are comparable to wild-type zebrafish, validating the model's utility.
• Future studies using transgenic reporter lines in Casper zebrafish will further advance reproductive biology research.