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Two zebra bullhead sharks were born at the Primorsky Aquarium in late February this year as a result of an eight-year-long reproduction project. Now, another fish species, Japanese red stingray Hemitrygon akajei, took over. While both males and females participated in the shark reproductive process, the offspring of the red stingray was generated through virgin birth. Parthenogenesis reproductive strategy that involves development of a sex cell without fertilization and mostly produces female offspring. It occurs in many live organisms, including insects, rotifers, cartilaginous and bony fishes, amphibians, reptiles and birds, however, parthenogenetic breeding at the Primorsky Aquarium has happened for the first time. The matriarch of the stingray family arrived here on a charter flight from Taiwan in 2016 and this March, eight years later, three pups appeared.
Red stingrays, or whip rays, are distributed over the tropical waters of the Northwest Pacific and the Western Central Pacific. They are often recorded along the Primorsky Krai coast during warm season, especially in the south of Peter the Great Bay. Red stingrays occur both at the bottom and at the surface water layers. They sometimes eat small fish, but their common food is marine worms, crabs, snails and clams, which they dig out of the sand with their pectoral fins.
The body of Hemitrygon akajei is 60-80 cm in diameter and its average weight is 10 kg. Large pectoral fins are fused with the head to form a rhomboid disc, the underside of which is orange red, hence its name. The tail is one and a half as long as the body and has a venomous spine.
Stingrays aren’t naturally aggressive. However, they are potentially dangerous for scuba divers and tourists. If a stingray meets a human, it prefers to retreat rather than to strike. The main tips to avoid ray’s attack are: never grab it and don’t touch its back.
It is also risky to step on a stingray buried in the sand. If that happens, the fish may whip its tail and drive the dorsal spine into the human’s skin. The sting causes severe pain and, if fragments of the spine are retained in the victim’s tissues, initiates an intense inflammatory process. Ray’s venom contains a range of toxins that induce low blood pressure, nausea, dizziness, headache, and muscle cramps. More severe symptoms include seizures, respiratory distress, and sometimes, death.
Returning to our three baby stingrays again, they are still very small, and their main armor, the venomous spine, is hidden under an integumentary sheath. The babies have different characters: one of them is very active and curious, the other two are calmer and more phlegmatic. We hope they will happily reach maturity in two to three years and two years later will give rise to a new generation.