Developmental regulation of the male urogenital papilla in the male marine teleost black rockfish, Sebastes schlegelii (Hilgendorf, 1880).

Abstract

The male external genitalia of the black rockfish (Sebastes schlegelii Hilgendorf, 1880) is a fleshy protrusion known as the urogenital papilla (UGP), which functions to deliver sperm into the female reproductive tract for internal fertilization. It is not known which genes regulate the development of the UGP. The aim of this study was to identify key genes that regulate the development of the UGP in black rockfish and to determine the distribution of androgen receptor gene (ar) in the UGP. A total of twenty-six adult males and 560 juvenile fish were used in the experiment, in which we divided all normally developing juveniles into normal development and androgen groups. We added methyltestosterone solution (100 ug/L) to the androgen group-treated fish tank, soaked for 2hours per day for 38days, and sampled 5 ~ 10 samples each time every 5days during the culture process. Gene expression changes related to urogenital papilla were analyzed with tissue specificity between control and androgen groups during sex differentiation, adult male maturation, and the copulation stage (September to December) using Real Time Quantitative PCR (RT-qPCR). The expression of ar (ara and arb) was also localized by two-color in situ hybridization in the UGP region of juvenile fish. Androgen treatment enhanced ar expression levels and the ar signal was stronger in the UGP region of both adult breeding fish and androgen-treated juvenile fish. This study provides insights into the regulation of the external genitalia of black rockfish and presents vital information for the artificial breeding of viviparous fish.