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Amphiuma meansTwo-toed Amphiuma

By Amiha Beri

Geographic Range

Two-toed amphiumas (Amphiuma means) are native to the southeastern United States. Their geographic range includes the Coastal Plain of southeastern North America. This includes southeastern Virginia into Florida and eastern Louisiana. Two-toed amphiumas are also found in the Gulf of Mexico and Atlantic Coastal Plains from New Orleans to southeastern Virginia and all of Florida. (Bonett, et al., 2009)

Habitat

Two-toed amphiumas are found in bayous, swamps, lakes, drainage ditches, wet meadows, and thick aquatic vegetation. Typically, two-toed amphiumas are found in very polluted waters, but they may also be found in clear streams. They may leave water on wet nights to travel to new areas, and during egg-laying season. (Bonett, et al., 2009)

  • Aquatic Biomes
  • lakes and ponds
  • rivers and streams

Physical Description

Two-toed amphiuma adults can reach 36.8 to 117 cm and can weigh between 39 to 1,042 g. Hatchlings range from 5.7 to 6.7 cm.

Larval two-toed amphiumas hatch with external gills, but they lose their gills shortly after hatching.

Two-toed amphiumas have long, cylindrical bodies. They have four vestigial legs and all four feet have two toes. Their tiny eyes are covered with skin and lack lids. Two-toed amphiuma adults have smooth skin. Their backs are dark brown or black in color and their ventral sides are dark gray. Sexes are alike; there is no sexual dimorphism. (Lannoo, 2005; Martof, et al., 1980; Sorensen, 2004)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    39 to 1,042 g
    1.37 to oz
  • Range length
    36.8 to 117 cm
    14.49 to 46.06 in

Development

Two-toed amphiuma females lay eggs that hatch after 5 months. Two-toed amphiumas begin their larval stage with external gills, but lose them around 2 weeks after hatching. Their gills are usually white, and are described as 3 finely branched on both sides of their heads.

Two-toed amphiumas remain mostly aquatic into adulthood, but they breathe through lungs and thus can travel over land. One pair of gill slits remains even when two-toed amphiumas are fully grown. Two-toed amphiumas exhibit neoteny because they retain their juvenile gill slits into adulthood. (Duke and R. Ultsch, 1990; Lannoo, 2005)

Reproduction

Not much is known about reproductive mating systems of two-toed amphiumas. Three-toed amphiumas (Amphiuma tridactylum) have better-studied courting behaviors. Male three-toed amphiuma court females by rubbing their snouts on the body of a female. If a female is ready to mate, it will turn its body and coil under the courting male so that their cloacas touch. During aquatic courtship between two individuals, a courting male swims rapidly in a circle and flaps its tails above the surface of the water and females respond by swimming below males. It is presumed that two-toed amphiumas follow a similar pattern. (Lannoo, 2005)

Two-toed amphiumas breed in the winter and spring. They employ internal fertilization, wherein the sperm of a male is transferred directly into the cloaca of a female. Courtship presumably takes place in the water, although courtship has never been directly observed for two-toed amphiumas. Females appear to release 150 to 200 eggs in moist, terrestrial sites from June to July. Eggs take about 5 months to hatch. Female two-toed amphiumas become sexually mature at 3 years old and males become sexually mature at 4 years old. (Lannoo, 2005)

  • Breeding interval
    Breeds once yearly
  • Breeding season
    Winter through Spring
  • Range number of offspring
    150 to 200
  • Average time to hatching
    5 months
  • Average time to independence
    0 minutes
  • Average age at sexual or reproductive maturity (female)
    3 years
  • Average age at sexual or reproductive maturity (male)
    4 years

Female two-toed amphiuma coil around and on top of their eggs, which protects them until they hatch around 5 months after being laid. Males provide no parental investment beyond mating. (Zug, et al., 2001)

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

Lifespan/Longevity

There is no information available concerning the maximum lifespan of two-toed amphiumas in the wild. The longest recorded lifespan for a captive individual was 27 years old. (Aresco, 2005; Snider and Bowler, 1992; Sorensen, 2004)

  • Range lifespan
    Status: captivity
    27 (high) years

Behavior

Two-toed amphiumas are mainly active at night, because they have eyes sensitive to ultra-violet light. They are described as sit-and-wait nocturnal predators.

Two-toed amphiumas are often difficult to handle because of their oily skins.

No distinct seasonal migrations have been recorded for two-toed amphiumas. They are primarily aquatic, but they may move over land. Two-toed amphiumas dig burrows in muddy bottoms or take over burrows of other creatures in semi-terrestrial habitats.

It has been suggested that two-toed amphiumas brumate in some parts of their range, as individuals have been found burrowed into moss and mud, immobile in winter months. However, with no obvious seasonal changes in body mass in Florida, it is likely that some populations are active year-round. (Aresco, 2005; Lannoo, 2005)

Home Range

Two-toed amphiumas have small home ranges. A study from 1983 reported that, in a 4-month period, males have home ranges that are commonly 12.4 square meters. Compared to adults, juvenile two-toed amphiumas are likely to have smaller home range sizes. There are no reports that two-toed amphiumas defend a territory. (Lannoo, 2005)

Communication and Perception

Two-toed amphiuma adults have tiny eyes that are covered with skin and lack lids. This means their vision is poor and they do not depend heavily on them. When feeding, two-toed amphiumas appear to use their senses of smell and touch. If the ends of their bodies rub against a food item, two-toed amphiumas instantly turn and grab it. Not much is known about courtship and mating behaviors of two-toed amphiumas. A related species, three-toed amphiumas (Amphiuma tridactylum) display courtship behavior that involves a male rubbing its snout on the body of a female. (Aresco, 2005)

Food Habits

Two-toed amphiumas are ambush predators, using a sit-and-wait feeding strategy. They remain still and wait for prey to come near as they remain hidden in their burrows. Adults feed on a variety of aquatic insects, including adults and larvae. Prey items include dragonflies (order Odonota), water striders (family Gerridae), and predaceous diving beetles (family Dytiscidae). They also feed on amphibians including greater sirens (Siren lacertina), other individuals in the genus Amphiuma, other salamander species, newt species such as eastern newts (Notophthalmus viridescens), adults frogs and tadpoles including southern cricket frogs (Acris gryllus) and southern leopard frogs (Lithobates sphenocephalus). Reptiles in their diet include multiple species of water snakes (genus Nerodia), anoles (genus Anolis), and mud turtles (genus Kinosternon). Two-toed amphiumas also consume small fish, spiders and mollusks. Crayfish make up a large part of their diet. Given this wide diet range, two-toed amphiumas are considered opportunistic feeders.

Food requirements of larval two-toed amphiumas include adult aquatic insects, larval aquatic insects, and amphipods (order Amphipoda). (Lannoo, 2005; Montana, et al., 2014)

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

Predation

Known predators of two-toed amphiumas include snakes, birds, and mammals. Mud snakes (Farancia abacura) and rainbow snakes (Farancia erytrogramma) are major predators. Two-toed amphiumas are nocturnal and typically inhabit dense vegetation, both of which are adaptations that help them avoid predators. Two-toed amphiumas also bite in self defense. (Lannoo, 2005; Sorensen, 2004)

Ecosystem Roles

Two-toed amphiumas are major predators of small aquatic vertebrates and invertebrates throughout their geographic range. Because of their diverse diet, two-toed amphiumas likely help control insect pest populations. There are some parasitic species that use two-toed amphiumas as hosts. These include trematodes (Telorchis stunkardi, Cephalogonimus amphiumae, and Megalodiscus americanus) and nematodes (Filaria amphiumae). (Heisler, et al., 1982; Lannoo, 2005)

Commensal/Parasitic Species
  • Trematode (Telorchis stunkardi)
  • Trematode (Cephalogonimus amphiumae)
  • Trematode (Megalodiscus americanus)
  • Nematode (Filaria amphiumae)

Economic Importance for Humans: Positive

Humans consume two-toed amphiumas in some parts of their geographic range. However, there is no information regarding the parts of their geographic range in which consumption by humans occurs. Two-toed amphiumas has no other known economic benefits to humans. (Willson, et al., 2005)

  • Positive Impacts
  • food

Economic Importance for Humans: Negative

When disturbed by humans, two-toed amphiumas can deliver a strong bite, which can lead to severe infection if untreated. There are no other known adverse effects of two-toed amphiumas on humans. (Willson, et al., 2005)

  • Negative Impacts
  • injures humans
    • bites or stings

Conservation Status

Two-toed amphiumas are listed as a species of "Least Concern" on the IUCN Red List. Some populations of two-toed amphiumas have disappeared because of wetland loss across their geographic range. Two-toed amphiumas require conservation measures directed towards the protection of coastal plain wetlands. Despite habitat loss affecting some populations, two-toed amphiumas are still common throughout much of their range and have sufficiently stable populations. Two-toed amphiumas have no special status on US Federal List, CITES, or the State of Michigan List. (Hammerson, 2004)

Contributors

Amiha Beri (author), Radford University, Karen Powers (editor), Radford University, April Tingle (editor), Radford University, Emily Clark (editor), Radford University, Cari Mcgregor (editor), Radford University, Jacob Vaught (editor), Radford University, Genevieve Barnett (editor), Colorado State University, Galen Burrell (editor), Special Projects.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

fertilization

union of egg and spermatozoan

food

A substance that provides both nutrients and energy to a living thing.

fossorial

Referring to a burrowing life-style or behavior, specialized for digging or burrowing.

freshwater

mainly lives in water that is not salty.

hibernation

the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.

insectivore

An animal that eats mainly insects or spiders.

internal fertilization

fertilization takes place within the female's body

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

metamorphosis

A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

molluscivore

eats mollusks, members of Phylum Mollusca

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

piscivore

an animal that mainly eats fish

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

tactile

uses touch to communicate

References

Aresco, J. 2005. Mitigation measures to reduce highway mortality of turtles and other herpetofauna at a North Florida Lake. Journal of Wildlife Management, 69/2: 549-560.

Aresco, J., M. S. Gunzburger. 2004. Effects of large-scale sediment removal on herpetofauna in Florida Wetlands. Journal of Herpetology, 38/2: 275-279.

Bonett, M., P. T. Chippindale, P. E. Moler, R. Van Devender, D. B. Wake. 2009. Evolution of gigantism in amphiumid salamanders. PLoS One, 4/5: e5615.

Duke, J., G. R. Ultsch. 1990. Metabolic oxygen regulation and conformity during submergence in the salamanders Siren lacertina, Amphiuma means, and Amphiuma tridactylum, and a comparison with other giant salamanders. Oecologia, 84/1: 16-23.

Hammerson, G. 2004. "Amphiuma means" (On-line). Accessed March 27, 2015 at http://www.iucnredlist.org/.

Heisler, N., G. Forcht, G. R. Ultsch, J. F. Anderson. 1982. Acid-base regulation in response to environmental hypercapnia in two aquatic salamanders, Siren lacertina and Amphiuma means. Respiratory Physiology, 49/2: 141-158.

Lannoo, M. 2005. Amphibian Declines. Berkeley and Los Angeles, California: Regents of the University of California.

Martof, S., W. M. Palmer, J. R. Bailey, J. R. Harrison III. 1980. Amphibians and Reptiles of the Carolinas and Virginia. United States of America: The University of North Carolina Press.

Montana, G., M. Ceneviva-Bastos, C. M. Schalk. 2014. New vertebrate prey for the aquatic salamander Amphiuma means (Caudata: Amphiumidae). Herpetology Notes, 7/1: 755-756.

Rose, L. 1967. Seasonal changes in lipid levels of the salamander Amphiuma means. Copeia, 1/3: 662-666.

S. Gunzburger, M. 2003. Evaluation of the hatching trigger and larval ecology of the salamander Amphiuma means. Herpetologists, 59/4: 459-468.

Snider, A., J. Bowler. 1992. Longevity of Reptiles and Amphibians in North American Collections. S. S. A. R., Lawrence, KS: Society for the Study of Amphibians and Reptiles.

Sorensen, K. 2004. Population characteristics of Siren lacertina and Amphiuma means in north Florida. Southeastern Naturalist, 3/2: 249-258.

Taylor, H., J. P. Ludlam. 2013. The role of size preference in prey selection of Amphiuma means. BIOS, 84/1: 8-13.

Tinkle, D. 1959. Observations of Reptiles and Amphibians in a Louisiana Swamp. American Midland Naturalist, 62/1: 189-205.

Willson, D., C. T. Winne, L. A. Fedewa. 2005. Unveiling escape and capture rates of aquatic snakes and salamanders (Siren spp. and Amphiuma means) in commercial funnel traps. Journal of Freshwater Ecology, 20/2: 397-403.

Zug, R., L. J. Vitt, J. P. Caldwell. 2001. Herpetology. San Diego, California: Elsevier Science.

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