Male little skate on the left, female little skate on the right.
Image credit: SCOTT BENNETT, MARTIN J. COHN, AND KATHERINE O'SHAUGHNESSY from https://www.science.org/content/article/how-shark-penises-evolved
The little skate is found in the northwestern Atlantic. They are one of the dominant members of the sea floor dwelling fish in this region.
Males and females have paired reproductive organs. The males have two claspers that transfer sperm via grooves. Females have two uteri and ovaries.
Image from O’Shaughness et al., 2015
During mating, the male mounts the female. He maintains a firm hold on her back with spines on his back.
The male then inserts one of his claspers into the females. The sperm is transferred along a groove down the clasper.
The female reproductive tract of a similar species (a freshwater ray). RO and LO are the right and left ovaries. RU and LU are the right and left uteri. V is the vertebrate column. E is the internal anatomy of the uterus.
Image from da Silva et al., 2017
Sperm move up to the oviductal or shell gland, an organ that functions for both long-term sperm storage and producing the egg case.
Sperm may be stored in the shell gland for months.
Egg cases visible in the shell glands in a similar species (thornback ray).
Image from Serra-Pereira et al., 2010
The female produces 10 to 35 eggs per year. Each egg is laid in a capsule, often called a mermaids purse.
References and Further Reading