Siren lacertina

Geographic Range

Greater sirens are found in the southern and eastern United States, along the Atlantic and Gulf coastal plains. They can be found as far north as eastern Virginia and south through the southern tip of Florida, and as far west as southwestern Alabama. There are reports of a disjoint population occupying the Rio Grande valley of southern Texas and northern Mexico. However, further investigation is required to assess the relationship of the two populations.

• Biogeographic Regions
• nearctic nearctic
  • native native

Habitat

Unlike many salamanders, greater sirens lack a terrestrial life stage and are found exclusively in aquatic environments for their entire lifespan. They prefer the shelter of heavily vegetated swamps, ponds, and ditches, but are also found in streams and large lakes. They migrate to shallow water in order to lay their eggs. Hatchlings live among thick vegetation (such as the roots of water hyacinth) and progressively move to deeper water as they mature. Adults spend the majority of their time near the bottoms of pools, entwined in plant roots and branches, or under sunken logs. When bodies of water dry out, greater sirens burrow into the muddy lake or stream bed and enter a state of aestivation to avoid dessication.

• Habitat Regions
• temperate temperate
• freshwater freshwater

• Aquatic Biomes
• lakes and ponds
• rivers and streams
• coastal coastal

• Wetlands
• swamp swamp

Physical Description

Greater sirens have a similar overall body shape to other salamanders, but have reduced forelimbs (containing four toes each) and no hind limbs giving, them rather eel-like appearance. Their body is round in cross section and encompasses about two thirds of their total length, with the rest being composed of a long, vertically flattened tail. The head is rounded into a square jaw with one small eye on each side. They possess external gills with three gill appendages a few centimeters behind their eyes, but before their legs. These appendages are crowded in the front of the body as opposed to being spread-out. Their skin is an olive or grayish brown color with black speckles and yellow dashes along its length (particularly on the dorsum). The underbelly tends to be lighter in color than the skin on the sides and back. Greater sirens can reach a length of 97 cm, but average around 62 to 77 cm.

Greater sirens can be distinguished from lesser sirens ( Siren intermedia ) by counting the number of costal grooves (lateral indentations that run down the length of a salamander's body) present. Greater sirens have 36 to 40 costal grooves as opposed to the 31 to 35 costal grooves found on lesser sirens. Additionally, lesser sirens are uniformly dark, more slender, and have sharper tails. Newly hatched greater sirens are striped and have a yellow or red triangular marking on their snout, while newly hatched lesser sirens lack stripes and snout markings.

• Other Physical Features
• ectothermic ectothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• sexes alike

Development

Greater sirens retain larval features throughout life. Their gills remain external throughout their life and they never develop hind limbs. Hatchlings are approximately 11 mm in length and are born with distinct stripes, which gradually fade and are completely lost within the first year of life. Newly hatched individuals will also have a red or yellow triangular marking on their snout. Juveniles tend to be brighter in color and have a more mottled appearance when compared to adult specimens.

• Development - Life Cycle
• neotenic/paedomorphic
• metamorphosis metamorphosis

Reproduction

Specifics of greater siren mating systems are unknown.

Greater sirens reach reproductive maturity around the age of two to three years. Mating behavior has yet to be observed and reported for this species. However, as in other amphibians, fertilization is assumed to be external. Greater sirens breed once yearly between February and March, although this depends on environmental conditions. Females lay a large clutch of about 500 eggs, which look like small grapes and adhere to each other. The eggs gestate for about two months and hatch in the months of April or May.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• fertilization fertilization
  • external external
• oviparous oviparous

Female greater sirens will guard their eggs in the shallows until they hatch and then return to deeper water. No further parental protection occurs.

• Parental Investment
• pre-fertilization
  • provisioning
• pre-hatching/birth
  • protecting
    • female

Lifespan/Longevity

Little is known about the expected lifespan of greater sirens in the wild or captivity. However, a single greater siren residing in the Cincinnati zoo has been reported to be at least 25 years of age.

Behavior

Greater sirens are strictly nocturnal. During the day, they seek refuge in dense vegetation near the bottom of the bodies of water in which they reside. When these habitats dry up, greater sirens burrow into the mud and secrete a cocoon consisting of dead squamous and epithelial cells. This outer covering prevents water loss. The gills waste away. There are reports of greater sirens living up to 5.2 years in this suspended state, losing nearly 80% of their body mass. However, when water returns, recovery from this aestivation period is rapid. In addition to gills, greater sirens possess lungs and are reported to gulp air at the surface of bodies of water. They also have the ability to perform gas exchange through their epidermis and have been observed crawling out of the water to rest on logs and shores. However, the reduced forelimbs are not suitable for extensive land travel.

• Key Behaviors
• natatorial natatorial
• nocturnal nocturnal
• motile motile
• sedentary sedentary
• aestivation
• solitary solitary

Home Range

No information is currently available regarding home ranges and territoriality in greater sirens.

Communication and Perception

Because greater sirens are solitary and seldom interact, little information is available regarding modes of intraspecific communication. They are known to produce hissing sounds when threatened by predators, however.

Because the eyes of greater sirens are rather small and they often inhabit areas of high water turbidity or otherwise low visibility, vision is likely to be a secondary sensory modality by which this species perceives its environment. They use an auxilliary olfactory organ (the vomeronasal or Jacobson's organ) to detect prey in these situations. They are also likely to use their lateral line (which most larval amphibians possess and which greater sirens maintain throughout their adult lives) to sense vibrations in their environment. It is thought that they may also be able to sense disturbances in electrical fields using dense arrays of neuromasts that are found on the head.

• Communication Channels
• acoustic acoustic

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• vibrations vibrations
• chemical chemical
• electric electric

Food Habits

Greater sirens are active at night and are primarily carnivorous. However, algae has been found in the digestive tract of some individuals, leading researchers to believe that they may be omnivorous. Greater sirens will prey on insects, crustaceans, gastropods, bivalves, spiders, mollusks, crayfish, and small fish.

• Primary Diet
• carnivore carnivore
  • insectivore insectivore
  • eats non-insect arthropods
  • molluscivore molluscivore
• herbivore herbivore
  • algivore

• Animal Foods
• fish
• insects
• terrestrial non-insect arthropods
• mollusks

• Plant Foods
• algae

Predation

Greater sirens have been found in the digestive tracts of American alligators and red-bellied mud snakes. Otherwise, little is known about their predators. To avoid predation, greater sirens employ several techniques. They can produce an array of sounds that can intimidate predators. These include yelps (similar to calls made by green tree frogs), hissing, croaking and a sound similar to that of a young duck. In addition, greater sirens may use their muscular tails to make a hasty getaway. As a last resort, a greater siren can deliver a painful bite to ward off predators.

• Anti-predator Adaptations
• cryptic cryptic

Ecosystem Roles

Greater sirens act as mid-level predators, feeding on insects and other invertebrate species. Greater sirens are also hosts to platyhelminth parasites, including flatworms ( Ophiotaenia sireni and Progorgodera foliata ) and trematodes ( Allassostomoides louisianaensis ).

Economic Importance for Humans: Positive

Greater sirens benefit humans by keeping aquatic invertebrate and insect populations in check.

• Positive Impacts
• controls pest population

Economic Importance for Humans: Negative

There are no known adverse effects of greater sirens on humans.

Conservation Status

Greater sirens are considered common throughout the central regions of their geographic range. However, their status throughout the peripheral regions of the range varies between abundant and rare. In Maryland, they are considered endangered. Greater siren populations are difficult to monitor, due to their permanently aquatic lifestyle. Encroachment on habitats by agricultural and urban development, including runoff of harmful pesticides, is the major potential threat to greater siren populations.

Additional Links

AmphibiaWeb

Encyclopedia of Life

BioKIDS Critter Catalog

Contributors

Kimberley McKenzie (author), Sierra College, Jeremy Wright (editor), University of Michigan-Ann Arbor, Catherine Kent (editor), Special Projects.

References

Behler, J., F. King. 1979. The Audubon Society Field Guide to North American Reptiles and Amphibians . New York: Knopf.

Brooks, D., R. Buckner. 1976. Some platyhelminth parasites of sirens (Amphibia: Sirenidae) from North America. The Journal of Parasitology , 62: 906-909.

Conant, R., J. Collins. 1991. A Field Guide to Reptiles and Amphibians of Eastern and Central North America. Third Edition, Expanded . New York, NY: Houghton Mifflin Company.

Fritzsch, B., T. Neary. 1998. The octavolateralis system of mechanosensory and electrosensory organs. Pp. 878-922 in Amphibian Biology, Volume 3, Sensory Perception . Chipping Norton, New South Wales, Australia: Surrey Beatty and Sons.

Hendricks, R. 2005. Siren lacertina Linnaeus, Greater Siren. Pp. 141, 361, 364, 372, 644, 911-4 in Amphibian Declines: The Conservation Status of United States Species . Berkeley: University of California Press.

Leviton, A. 1971. Reptiles and Amphibians of North America . Garden City, New York: Doubleday.

Sorensen, K., P. Moler. 2008. Greater Siren, Siren lacertina. Pp. 263-5 in Amphibians and Reptiles of Georgia . Athens, Georgia: University of Georgia Press. Accessed November 20, 2011 at http://books.google.com/books?id=F4ffa47N9wwC&pg=PA265&lpg=PA265&dq=greater+siren+male+female&source=bl&ots=Fu92LOsFq8&sig=MubvlRASvax-rv7_sTcQcVvzUiA&hl=en&ei=xA-uTpjeJIvYiALAvPmyCw&sa=X&oi=book_result&ct=result&resnum=3&ved=0CDAQ6AEwAg#v=onepage&q&f=false .

Sullivan, A., P. Frese, A. Mathis. 2000. Does the aquatic salamander, Siren intermedia, respond to chemical cues from prey. Journal of Herpetology , 34: 607-611.