Little Skate - Biology and Ecology - Reproduction

Reproduction

Little skates are oviparous. Mating occurs frequently throughout the year and pregnant females can be found year-round. However, eggs are most common from October to December and from April to May, and least common from August to September and February to March. An average little skate spawns twice a year, in spring and fall, and produces a total of 10-35 eggs annually. Females deposit their egg capsules in pairs on sandy bottoms, in water no more than 27 meters (89 ft) deep. The egg cases are amber-colored when first laid but become greenish-brown and leathery. Each roughly rectangular case contains a single fertilized egg and measures 4.4-6.3 cm (1.7-2.5 in) long and 3-4.5 cm (1.2-1.8 in) wide. There are hollow horns at each corner with sticky tendrils to secure the egg case to the substrate; the anterior horns are half as long as the case and curved inward, while the posterior horns are as long as the case and nearly straight.

Eggs raised in captivity hatch in 5–6 months, while those in the wild may take up to 12 months to hatch, depending on temperature. While inside the case, the embryos have a whip-like extension on the tail believed to be used for circulating water. The newborns measure 9.3-10.2 cm (3.7–4 in) long and are perfectly formed miniatures of the adults. After hatching, the empty egg capsules often wash ashore and are known as "mermaid's purses". Growth is about 10 cm (4 in) per year for the first three years, then slows down to 5 cm (2 in) per year between the third and fourth years. At adolescence, males become larger than the females, and this difference persists through adulthood. Males mature at 32–43 cm (13–17 in) long and females at 36–45 cm (14–18 in) long. Very few little skates over 5 years old have been found, suggesting a high mortality rate at that age.

An unusual little skate specimen found off Fishers Island, New York contained a developed testis, vas deferens, and functional clasper on its left side and an adolescent ovary, shell gland, oviduct, and abortive clasper on its right. This example of hermaphroditism is one of very few known for elasmobranch fishes.