Several weeks ago, a group from the museum visited the ODWC’s Red Slough in search of some salamanders that only occur in swamps of the southeastern part of Oklahoma. We were able to trap more than 20 sirens, which are elongate, eel-shaped salamanders that live their lives in water. They are in their own family, the Sirenidae, and the species that occurs in Oklahoma is the Western lesser siren, Siren intermedia.
Unlike eels, sirens have external gills and a pair of tiny front legs, that on first glance, appear useless. Believe it or not, they use these legs on rainy nights when they move short distances across land. These sirens can reach eight inches in length, but most are slightly smaller. In most salamanders that have aquatic larvae, external gills used for respiration in water are lost when the salamanders metamorphose into terrestrial adults. In sirens, no obvious metamorphosis takes place, with the adults looking exactly like the “larvae,” just larger in size. However, close examination of the internal morphology reveals that reproductive organs develop as the “larvae” increase in size and age. Consequently, they do “metamorphose” but retain some larval characteristics (external gills).
Sirens reach sexual maturity in about two years. They deposit from 100–200 eggs in cavities in mud at the bottom of swamps. One of the most interesting aspects of the biology of sirens is their ability to form a cocoon around their body when swamps dry up. They burrow into the mud and secrete mucous that forms the cocoon, the function of which is to prevent them from drying up. Sirens can remain inactive for as much as eight months in their cocoon until rains fill the swamps that they live in.
Although sirens are difficult to observe because they are under water, they can be easily trapped with minnow traps, and no bait is needed. If you should trap one to observe, be sure to keep it in water that contains oxygen and is not chlorinated. It might also be useful to drop a few dried pine needles or oak leaves into the aquarium as tannins released from needles and leaves can keep mold from attacking the skin of sirens and other aquatic amphibians and reptiles.