Sirens and Dwarf Sirens: Sirenidae
SIRENS AND DWARF SIRENS: SirenidaeLESSER SIREN (Siren intermedia): SPECIES ACCOUNT
Sirens and dwarf sirens are salamanders with eel-like bodies, no hind legs, and front legs that are extremely small. The jaws are covered with a hard, beaklike structure. The gills are large and stick up from the head like feathers. The body is shaped like a tube with a flat tail. Young sirens have a clear fin on their back that extends to the tip of the tail. On older sirens the part of the fin on the back disappears, and the tail fin that is left becomes solid rather than clear. The legs of sirens have three or four toes that have hard tips.
Sirens and dwarf sirens never leave the water. They get oxygen from water passing through their gills and skin, but they also have lungs. These salamanders live their entire lives with a larva body form. A larva (LAR-vuh) is an animal in an early stage that changes form, or goes through metamorphosis (meh-tuh-MOR-foh-sus), to become an adult. Sirens and dwarf sirens do not respond to the environmental signals that tell other salamanders to start metamorphosis.
Sirens and dwarf sirens are 5 to 40 inches (12 to 100 centimeters) long. Newly hatched sirens and younger larvae (LAR-vee, the plural of larva) are deep black with yellow, red, or silvery white markings. There is a band across the nose and another on the top of the head. Many of these animals have stripes on the body. When the animals are older the markings become dull or disappear.
Sirens live in North America from the far northeastern part of Mexico north to the southwestern part of Michigan and east to Maryland. Dwarf sirens live in the southeastern part of the United States from Florida to South Carolina.
Sirens and dwarf sirens live in still to slowly flowing, often swampy, water with a muddy bottom and sometimes with floating and rooted plants.
Sirens and dwarf sirens eat any water animal small enough for them to swallow.
BEHAVIOR AND REPRODUCTION
Sirens and dwarf sirens hide in burrows near the water's edge during daylight hours and come out at night to look for food along the water bottom and among plants. These salamanders swim by making wavy movements of their body and tail, but they also move their small legs in walking motions when they are near the bottom.
To find food, sirens and dwarf sirens poke around with their snouts and find prey using their sense of smell. They suck food into their mouth by rapidly expanding their throat and opening the mouth so that the food is sucked inside with a rush of water. Gill rakers keep the food inside the throat, and the water passes to the outside through gill slits. Sirens and dwarf sirens are greedy eaters. They shake their prey vigorously and swallow larger animals in a series of gulps without breaking the prey into pieces.
Even though they look like larvae, adult sirens and dwarf sirens have reproductive organs and produce young. Scientists do not know how fertilization (FUR-teh-lih-ZAY-shun), or the joining of egg and sperm to start development, takes place in these salamanders. They believe it happens outside the body because males do not have glands for making a sperm packet, and females do not have a sac for sperm storage. The large eggs are laid singly, sometimes attached to plants, or in groups.
SIRENS, DWARF SIRENS, AND PEOPLE
Dwarf sirens have been sold as fishing bait.
Sirens and dwarf sirens are not considered threatened or endangered.
Physical characteristics: In addition to having a long, tubular body, no hind legs, and very short front legs, lesser sirens have thirty-one to thirty-seven grooves along their sides, four toes, and three gill slits. They are 7 to 27 inches (18 to 69 centimeters) long. The head is broadly rounded when looked at from the top. Newly hatched larvae are densely black and have bright red bands across the tip of the snout, across the head, and on the body. Older lesser sirens may keep a pale snout band, but the other markings disappear. The adult color pattern appears to vary from place to place in the geographic range, but there is always a greenish to gray background color with different amounts of shimmery speckling. The clear fin on the young siren's back and tail becomes solid in older lesser sirens and is present only on the tail.
Geographic range: Lesser sirens live in North America from the far northeastern part of Mexico north to the southwestern part of Michigan and east to Florida and the southeastern part of Virginia.
Habitat: Lesser sirens live in many types of still or slowly flowing water, such as swamps, ponds, and ditches.
Diet: Lesser sirens eat almost any water animal they can catch and fit into their mouths, including small crustaceans such as crayfish, worms, mollusks such as snails, insect larvae, and small fishes. Crustaceans (krus-TAY-shuns) are water-dwelling animals that have jointed legs and a hard shell but no backbone. Mollusks (MAH-lusks) are animals with a soft, unsegmented body that may or may not have a shell.
Behavior and reproduction: Lesser sirens spend all their time in the water. Large numbers of them may live in one place. These salamanders spend the daylight hours burrowed into the water bottom or near the water's edge. They look for food along the water bottom at night. They suck the prey into their mouths and swallow it whole.
Salamanders usually do not make a sound, but when bitten or forced from a hiding spot by another salamander, lesser sirens yelp. Lesser sirens placed in unfamiliar surroundings may make several types of sounds. If there is not enough oxygen in the water, these lesser sirens come to the surface to gulp air.
If their pond, ditch, or mud hole dries out, lesser sirens move into burrows at the bottom and wait for water. They make a cocoon by shedding their skin several times and become inactive until water returns. The gills do not work unless the salamander is underwater, and they become small nubs while the lesser siren is in its burrow and breathing with its lungs.
Female lesser sirens lay as many as fifteen hundred eggs in a nest at the water bottom. Scientists believe one of the parents guards the nest. Each egg is enclosed in four jelly envelopes. The eggs hatch forty-five to seventy-five days after being laid. At this point the larvae are about 0.4 inches (10 millimeters) long.
Scientists do not know how lesser sirens find their mates or how the eggs are fertilized (FUR-teh-lyzed). They have found that during the breeding season most lesser sirens large enough to reproduce have a number of bite marks on them that match the size of the mouth of this species. Scientists believe males and females may bite each other during mating or that males bite one another while fighting over females or over territory.
Lesser sirens and people: Lesser sirens have no known importance to people. Some people are afraid of these salamanders because they confuse them with amphiumas (AM-fee-yoo-muhs), which give a dangerous bite.
Conservation status: Lesser sirens are not considered threatened or endangered. ∎
FOR MORE INFORMATION
Bernhard, Emery. Salamanders. New York: Holiday House, 1995.
Llamas Ruiz, Andres. Reptiles and Amphibians: Birth and Growth. New York: Sterling, 1996.
Gabbard, J. "Siren intermedia." Animal Diversity Web.http://animaldiversity.ummz.umich.edu/site/accounts/information/Siren_intermedia.html (accessed on March 28, 2005).