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Description

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A relatively large, elongate aquatic salamander. All members of the Family Sirenidae (sirens and dwarf sirens) lack hind limbs and eyelids, have a horny beak on the upper and lower jaws, and retain gills throughout life (Martof 1974a b; Petranka 1998). Sirens have four toes on the forelimbs and three gill slits. There is a dorsal fin, restricted to the tail. Adult Siren intermedia attain lengths of 18-69 cm, total length (Petranka 1998). The tail is 28 - 40% of the total length in adults (Martof 1973). Males have enlarged jaw (masseter) muscles which cause the head, posterior to the eyes, to appear swollen. Males are also slightly longer than females. Hatchlings have large, bushy gills and a dorsal fin on the tail which extends onto the trunk region of the body (Martof 1973; Petranka 1998).. Hatchlings are 11 - 11.5 mm total length and the tail is about 19 - 25% of the total length (Martof 1973; Godley 1983). Limb buds are present at hatching (Godley 1983).The dorsal ground color of adults is variable, ranging from olive green to grayish blue or black. Brown or black spots can be seen scattered on the dorsum of lighter colored individuals. The venter is lighter than the back and white or yellowish flecks may occur on the sides (Martof 1973; Petranka 1998). Hatchlings and juveniles are more brightly colored than adults, having light stripes along the body and yellow or red banding on the head (Martof 1973; Petranka 1998). The bright colors and stripes fade and the dorsal fin on the back is lost as animals age (Petranka 1998).Two or three subspecies are recognized and can be distinguished based on distribution (see below), size, and coloration. Siren i. intermedia, the eastern lesser siren, is a dark colored form, sometimes having tiny black spots on the dark brown or black dorsum. The venter is also dark, without spots or mottling, and lighter than the dorsum. Maximum length is about 38 cm, and the modal number of costal grooves is 32-33. Siren i. nettingi, the western lesser siren, is olive green to gray with tiny black spots on the dorsum. The venter is also dark with numerous light flecks. Maximum length is 50 cm, with a modal number of 35 costal grooves. Siren i. texana, the Rio Grande siren, is the largest subspecies, reaching 69 cm total length, and having a modal costal groove count of 37. The dorsum is gray to brownish gray with tiny black spots and the venter is light gray. Descriptions from Petranka (1998)

References

  • Fauth, J. E. and Resetarits, W. J., Jr. (1999). ''Biting in the salamander Siren intermedia intermedia: Courtship component or agonistic behavior?'' Journal of Herpetology, 33, 493-496.
  • Flores-Villela, O., and Brandon, R.A. (1992). ''Siren lacertina (Amphibia: Caudata) in northeastern Mexico and southern Texas.'' Annals of Carnegie Museum, 61, 289-291.
  • Gehlbach, F. R., and Kennedy, S. E. (1978). ''Population ecology of a highly productive aquatic salamander (Siren intermedia).'' Southwestern Naturalist, 23, 423-430.
  • Godley, J. S. (1983). "Observations on the courtship, nests and young of Siren intermedia in southern Florida." American Midland Naturalist, 110, 215-219.
  • Martof, B. S. (1973). ''Siren intermedia Le Conte. Lesser Siren.'' Catalogue of American Amphibians and Reptiles. Society for the Study of Amphibians and Reptiles, 127.1-127.3.
  • Martof, B. S. (1974). ''Siren Linnaeus. Sirens.'' Catalogue of American Amphibians and Reptiles. Society for the Study of Amphibians and Reptiles, 152.1-152.2.
  • Raymond, L. R. (1991). "Seasonal activity of Siren intermedia in northwestern Louisiana (Amphibia: Sirenidae)." Southwestern Naturalist, 36, 144-147.

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Distribution and Habitat

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Siren intermedia occurs on the Atlantic Coast Plain from Virginia to Florida and west to southern Texas and north eastern Mexico. The range also extends northward in the Mississippi Valley to Illinois, Indiana, and southwestern Michigan. Siren i. intermedia, the eastern lesser siren, ranges from central Alabama to sourtheastern Virginia. Siren i. nettingi, the western lesser siren, occurs from central Texas to Alabama, and northwards up the Mississippi Valley. Siren i. texana, the Rio Grande siren, occurs only in the lower Rio Grande Valley and adjacent areas of northern Mexico. Range information taken from Petranka (1998).Recent studies have suggesed that S. i. texana is not distinct from S. i. nettingi and that all populations from the western portion of the range should be treated as S. i. nettingi (Flores-Villela and Brandon 1992).Lesser sirens are found in a diversity of permanent and semi-permanent aquatic habitats including swamps, marshes, ditches, canals, sloughs, farm ponds, temporary pools in floodplains, and shallow heavily vegetated ponds with deep sediments into which they burrow. See Petranka, (1998) and references therein.
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Life History, Abundance, Activity, and Special Behaviors

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Continuing loss of wetlands is a threat to the habitat of lesser sirens (Petranka 1998).
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Life History, Abundance, Activity, and Special Behaviors

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Courship and mating have not been observed. Fertilization is presumed to be external (Martof 1974; Sever et al. 1996). Sirens are more active in the fall and winter (Raymond 1991), gravid females are found in late winter, and eggs are laid from late winter to early spring (January to March) (Gehlbach and Kennedy 1978; Raymond 1991). The precise timing of mating and egg deposition varies with locality (Raymond 1991). Females lay 151-362 eggs and have been found attending the developing eggs (Gehlbach and Kennedy 1978; Godley 1983). Nests have been found among the roots of water hyacinth, and grass (Spartina) (Godley 1983).Biting of females by males apparently occurs during the mating season (Godley 1983; Fauth and Resetarits 1999), but bite marks have also been reported on males (Raymond 1991; Fauth and Resetarits 1999). This and the fact that biting also occurs outside of the mating season (on males and females) suggests that there is male-female and male-male aggression; females have not been found to bite other females (Fauth and Resetarits 1999).When temporary water bodies dry, sirens burrow into soft mud and can aestivate for several months until the ponds fills again (Petranka 1998). Diet of sirens includes a variety of aquatic invertabrates both benthic and pelagic (Petranka 1998).Sirens are locally abundant and densities have been estimatied as 0.9-1.3 sirens/m2(Gehlbach and Kennedy 1978).Sirens are known to vocalize, and they emit barks, yelps, and clicks in intraspecific interactions and also when disturbed (Petranka and references therein 1998).
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Relation to Humans

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Sirens are sometimes seen in the pet trade.
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Lifespan, longevity, and ageing

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Maximum longevity: 25.7 years (captivity)
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Trophic Strategy

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Siren intermedia feeds primarily on aquatic invertebrates such as crustaceans, insect larvae, worms, and snails. They will also readily consume young amphibian larvae and their own eggs. Siren intermedia often feeds by gulping large quantities of material at a time, which is filtered through the bronchial openings. Vegetable matter sometimes found in their digestive tracts is probably eaten accidentally.

Animal Foods: insects; terrestrial non-insect arthropods; mollusks; terrestrial worms; aquatic crustaceans

Primary Diet: carnivore (Insectivore , Eats non-insect arthropods, Molluscivore , Vermivore)

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Gabbard, J. 2000. "Siren intermedia" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Siren_intermedia.html
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Distribution

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Siren intermedia, the Lesser Siren, ranges from the Coastal Plains of Virginia to Florida, then westward to southern Texas and northeastern Mexico. Populations extend northward in the Mississippi Valley to Illinois, Indiana, and southwestern Michigan. Geographic isolates occur in northern Indiana, southwest Michigan, northeastern North Carolina, and southeastern Virginia.(Petranka 1998) This range is occupied by three subspecies, they are S. i. intermedia, S. i. nettingi, and S. i. texana. All of these subspecies only vary slightly in physical characteristics such as length and color (Conant and Collins, 1998).

Biogeographic Regions: nearctic (Native )

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Gabbard, J. 2000. "Siren intermedia" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Siren_intermedia.html
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Habitat

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Siren intermedia will inhabit most any slow and sluggish body of water that is shallow and with plenty of aquatic vegetation, including marshes, ponds, ditches, and canals. In most circumstances they need a permanent or semi-permanent body of water but they are able to move short distances over land if factors are right or stay encased in a cocoon of slime if drought occurs.

Habitat Regions: temperate ; freshwater

Aquatic Biomes: lakes and ponds

Wetlands: marsh ; swamp ; bog

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Gabbard, J. 2000. "Siren intermedia" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Siren_intermedia.html
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Life Expectancy

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Average lifespan
Status: captivity:
6.3 years.

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Gabbard, J. 2000. "Siren intermedia" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Siren_intermedia.html
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Morphology

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Siren intermedia is an eel-like salamander with a long slender body (18-68 cm long) and a very small dorsal fin that runs from the vent to the tail tip. It has only a pair of front legs; each foot has four toes. The front legs are very reduced and the rear legs are completely absent. The head is rather flattened, and there are bushy external gills located on each side of the head. Siren intermedia varies in coloration from light grayish green to olive or black; there are also small irregular markings (dots) that are visible on lighter colored individuals.

Larvae and juveniles are more brightly marked, with a red band across the nose and along the side of the head.

Other Physical Features: endothermic ; ectothermic ; heterothermic ; bilateral symmetry

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Gabbard, J. 2000. "Siren intermedia" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Siren_intermedia.html
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Benefits

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Sirens are occasionally used for fish bait, but this species normally attracts little attention from humans. They occupy a predatory niche in shallow freshwater habitats, and have ecological value in the environment.

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Gabbard, J. 2000. "Siren intermedia" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Siren_intermedia.html
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Benefits

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On occasion a Siren might take a fisherman's baited hook, but this would be an uncommon and minor annoyance. These animals are properly considered harmless to human interests.

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Gabbard, J. 2000. "Siren intermedia" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Siren_intermedia.html
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Life Cycle

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Development - Life Cycle: metamorphosis

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Gabbard, J. 2000. "Siren intermedia" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Siren_intermedia.html
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Conservation Status

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Siren intermedia is extremely rare and possibly extirpated in Michigan but this species is not threatened over most of its range. It could be harmed by chemicals such as Rotenone, which is used as a fisheries management tool and can be fatal to aquatic amphibians such as Siren intermedia. Another factor that may affect the vitality of this species is habitat destruction and the filling in of wetlands.

US Federal List: no special status

CITES: no special status

State of Michigan List: no special status

IUCN Red List of Threatened Species: least concern

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Gabbard, J. 2000. "Siren intermedia" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Siren_intermedia.html
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Reproduction

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The courtship behavior of Siren intermedia has not yet been described. Fertilization has been presumed to be external, since the females lack cloacal sperm storage areas. There is thought to be a lot of aggression during mating due to the amount of scaring from bite marks on both the males and females. Eggs are laid in early spring they are deposited in shallow depressions in the soft bottom of the occupied water body, usually in highly vegetated areas. In these shallow depressions the female will lay from 12 to over 300 eggs; the female may lay multiple clutches through out the season. Freshly laid eggs are dark brown and 2.5-3 mm in diameter. The hatchling larvae are about 1.1 cm in length. (Petranka 1998; Harding 1997)

Key Reproductive Features: gonochoric/gonochoristic/dioecious (sexes separate)

Average number of offspring: 200.

Average age at sexual or reproductive maturity (male)
Sex: male:
730 days.

Average age at sexual or reproductive maturity (female)
Sex: female:
730 days.

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Gabbard, J. 2000. "Siren intermedia" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Siren_intermedia.html
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Lesser siren

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The lesser siren (Siren intermedia) is a species of aquatic salamander native to the eastern United States and northern Mexico. They are referred to by numerous common names, including two-legged eel, dwarf siren, and mud eel. The specific epithet intermedia denotes their intermediate size, between the greater siren, Siren lacertina, and the dwarf sirens, Pseudobranchus species.

Description

Lesser sirens have elongated bodies possessing only two limbs, a pair of four-toed legs located behind the base of the head, and range in length from 7 to 27 inches (17 – 69 cm). Unlike greater sirens, lesser sirens have less than 35 costal grooves.[2] Juvenile specimens have red to yellow banding on their heads and stripes running along the main length of the body, although these stripes are absent in Siren intermedia. Adults have plainer coloration; the dorsal side is typically olive green to blue-gray or black, while the ventral is usually light grey. Spotted patterns may also be present in adults.[3] In salamanders, sexual size dimorphism is usually female-biased, but in Siren intermedia, it’s the opposite. Males are the larger sex, and they also have significantly larger heads and enlarged masseter muscles than females.[4]

Lesser sirens are notably neotenic, and possess external gills throughout their lives.[3]

Taxonomy

Siren intermedia nettingi, the western lesser siren.

Sources disagree on the number of subspecies within S. intermedia. The majority of the sources in the field agree there are at least two: an eastern and a western variety. Many sources also include a third subspecies, the Rio Grande lesser siren, S. i. texana, but researchers disagree whether the Rio Grande variety belongs as a lesser siren, within S. intermedia, or as a greater siren, within S. lacertina, and some others even consider it to be its own species, as S. texana.[5][6]

  • Eastern lesser siren, S. i. intermedia Goin, 1942
  • Western lesser siren, S. i. nettingi Goin, 1942
  • Rio Grande lesser siren, S. i. texana Goin, 1957

Habitat and distribution

Habitat

Sirens are likely to be found in ponds near other intermittent wetlands. They usually inhabit swamps and ponds, and can survive in dry ponds for up to two years by a process called “aestivating”. Sirens are considered poor overland dispersers because they rarely leave the water, so their geographical distribution is largely determined by pond connectivity and biotic interactions.[7]

Lesser sirens are aquatic salamanders, but their ability to withstand factors like dehydration allows them to have good survival skills in their ephemeral habitats. Sirens are able to osmoregulate and produce a mucoid cocoon during aestivation, which greatly reduces dehydration and electrolyte stress.[8] Their small legs enable them to move on dry land for short periods of time.[9]

Geographic distribution

The lesser siren is found in the United States and Mexico, primarily from Virginia to Florida, west to Texas, ranging into northeastern Mexico as far as Veracruz, and north to Illinois and southwest Michigan.[1][10] Multiple specimens have recently been rediscovered in Michigan after a 60-year absence.[11][12] Lesser sirens only occur in permanent wetlands, whereas other salamander and frog species can occupy a range of dry and wetlands. Lesser sirens are top predators in permanent wetlands.[13] They can quickly colonize and become dominant consumers in new ponds such as those constructed by beavers. Their ability to aestivate and burrow in soft sediments and live in dense aquatic vegetation in shallow waters facilitates their dominance. In addition, the species’ high productivity, high fecundity, and rapid growth to early sexual maturity allows it reach a high density quickly and easily, and thus establish dominance in the habitat.[14]

Conservation

The lesser siren is quite common through most of its range, but rarely seen due to its secretive nature. Like almost all species of amphibian, their numbers are believed to be declining due to general reductions in water quality caused by agricultural pesticide and fertilizer runoff. They are frequently collected and used as bait for fishing.

The species was once believed to be extirpated from Michigan,[11] but has been recently rediscovered in limited numbers.[15] The S. i. texana subspecies is listed as a threatened species in Texas. They are listed as Least concern on the IUCN Red List and a species with "Special Protection" in Mexico.[1]

Physiology

Vision

Western Lesser Sirens (Siren intermedia nettingi) have poor eyesight. They rely on their other senses to forage, hunt, and survive.[13]

Chemical Sense

Sirens rely on chemical cues to detect prey and not on visual cues. The use of chemical stimuli in the detection of prey and predators are common in amphibians. [16]

Respiration

All species in the sirenidae family are paedomorphic, eel-shaped salamanders that live in aquatic environments. They respire through their gills, lungs and skin, and survive well in hypoxic environments low in oxygen. Siren intermedia is unique among amphibians in its ability to construct a mucoid cocoon that slows down dehydration during aestivation, and the lesser siren can withstand long periods of food deprivation without ill effects. During aestivation, respiration slows down significantly, and gills atrophy over the next 16 or more weeks.[8]

Acoustic behavior

The lesser siren is vocal, unlike most salamanders. The lesser siren is known to emit a series of clicks when it approaches others of its species, or a short screeching sound if handled. Acoustic behavior serves a functional service in S. intermedia, especially since it is nocturnal and it burrows in sediments, swims and crawls through densely vegetated waters. However, ts visual and olfactory senses are very limited in this habitat, and thus the possibility of predation and other risks are high in this case. Nevertheless, acoustic behavior in lesser sirens is still infrequent, and becomes even less frequent with undisturbed habitat residency, perhaps because of their familiarity with the environment.[17]

Siren intermedia make and responds to underwater sounds that may have specific communicational significance. Resting sirens are usually silent, but they may produce trains of pulsed sounds or “clicks”. Their tendency to click is greater in groups than in single specimens, which suggests that they are involved in intraspecific communication. These acoustic behaviors occur most often when other sirens are present. They are emitted at different pulse rates by specimens clicking simultaneously, and are associated with head-jerking motions. Head-jerking may offer visual reinforcement of an acoustically defended individual space, or it may be required for sound production. S. intermedia can produce clicks by moving the horny jaw coverings together rapidly, and head-jerking may be associated with such movement when it is particularly forceful. This means of sound production is similar to the upper and lower teeth of humans, clicking with the mouth open.[17]

Another frequently produced sound ("yelp") is associated with cases of distress, or alarm. When S. intermedia butt or bite each other in their habitat, the bitten or injured individuals may swim away quickly, emitting yelps at frequencies of 880 Hz. These yelp sounds could have communicational significance if they prevent further attack or signal to other individuals that one is injured.[17]

Osmoregulation

Animals that inhabit freshwater habitats have high-affinity sodium uptake systems. Therefore, the better an animal is adapted to freshwater, the lower the rate of sodium loss and uptake. Sirens have a high sodium affinity (around 0.2 peq/g per day), and thus are able to resist the harmful effects of low-sodium environments.[8]

Hormones

Insulin has been isolated from the pancreas of lesser sirens that is mostly conserved in sequence as compared to other amphibian orders. However, it does have some substitution differences that indicate that sirens diverged early from other salamanders.[18]

Diet

Lesser sirens are filter feeders. They sift through pond bottoms and aquatic vegetation for prey items.[13] They have heavily keratinized beaks and vomerine dental arrays that can inflict substantial wounds.[7] The diet of the lesser siren includes at least 10 different taxa, which includes primarily aquatic invertebrates, including tadpoles and snails. They also eat several insects and their larvae, crayfish, mollusks, amphibians, siren eggs, and algae, although the plant material may be an incidental result of their gape-and-suck feeding style.[19]

Reproduction and life cycle

Annual seasonal behavior changes

The lesser siren is nocturnal, spending its days hidden in the debris and mud at the bottom of slow-moving bodies of water. Sirens are most active in the fall and spring seasons, when water temperatures are close to 15 °C and there is no danger of drought.[20] During the summer months, the ponds and other habitats that the lesser siren live in go through periods of drought, which leads to low water levels and possibly dried-up ponds. The lesser siren’s strategy to withstand the rigors of these dry seasons is something called “aestivation”, or summer dormancy, which can last up to 35 weeks, depending on the severity of the drought. During the sixteen-week period from July to October, aquatic lesser sirens increase the osmotic concentration of their body fluids, and slow down bodily functions.[21]

They do this by burrowing themselves into the bottom of its drying pond in tube-like channels about the length and width of their bodies. For the rest of the aestivating process, they then secrete a mucous cocoon. That is then followed by a significant drop in their oxygen consumption and heart rate. The gills slowly atrophy and the body shrinks, and as a result the fat is metabolized at one-fifth the normal rate. As expected, large individuals store more fat and consume less oxygen per unit weight than small ones, and thus can survive much longer periods of aestivation. Some individuals, especially the smaller sirens during aestivation, die or suffer from dehydration as they are unable to store sufficient fat and the greater metabolic demand reduces their chance of survival.[21]

As the drought season comes to an end, lesser sirens become active within a day, and slowly regain the lost weight over the next 8–11 weeks.[21]

Mating

Mate choice

From November to January, males occupy a shelter as a nest site usually surrounded by vegetation or among plant roots, and actively equip it with moss from the surrounding nest site, plucking plant material and dragging it back to the nest site. They then defend their territory aggressively against others through biting.[4]

Courting

Though little is known about their courtship, it is believed to be quite violent, as many specimens collected have scarring from healed bite marks from other sirens. About 12-300 eggs are laid at a time, and several clutches may be laid over the course of the year. Hatchlings are only about 0.4 in (1.1 cm) in length, but grow quickly. Maturity is typically reached in approximately three to four years. Courtship includes several repeating behavioral patterns. Once the female approaches the nest site, the male and female start moving within the area, coiling around each other. The male pursues the female’s cloaca closely, sometimes rubbing his head against the flank and the cloacal region of the female. Both the male and the female wave their tail fins by undulating the tail tip.[4]

Parental care

Oviposition

During oviposition, the female turns on its back, positions the cloaca near the top of the nest cavity and halts for several seconds. Then the male positions his cloaca near the site of oviposition. Eggs are directly coiled into the moss that the male has prepared in the nest. Interlacing of the eggs into the plant material in the nest ensures that the eggs adhere to the nest as a compact mass, and facilitates external fertilization.[4]

Egg guarding

In S. intermedia, parental care is fulfilled by the males. Paternal care as observed in the lesser siren is very rare for salamanders. After the female completes oviposition and leaves the nest, the male stays in close proximity to the eggs and takes the responsibility of parental care. The total number of eggs can be around 120–130, with a diameter of about 3 mm. The male constantly moves the egg mass, circles around it, and aerates the eggs through vigorous tail fanning. The tail-fanning behavior of the male towards the eggs can enhance sperm dispersal. Additionally, the male continuously cleans the nest from sand and other materials, to improve hygienic conditions and possibly to prevent infections from pathogens and fungi. It is also likely that males remove dead or infected eggs, in order to prevent further infection of the viable eggs.[4]

The development of the larvae takes approximately 35 days. Paternal care does not end there however, it continues after the larvae hatch and the male continues to aggressively defend the larvae up to one week after hatching.[4]

Mutualisms

Siren intermedia has many important effects on community structure as it is one of the most important predators in temporary ponds, where it complements the keystone predator role of eastern newts (Notophthalmus viridescens).[22] S. intermedia reduces the total densities of the anuran larvae, and by doing that, it allows the eastern newts to act as keystone predators over a broad range of prey densities.[7]

Enemies

Adult mole salamanders (Ambystoma talpoideum) and lesser sirens (Siren intermedia), are the top two predators in temporary ponds of the southeastern United States. Siren intermedia competes with and is an intraguild predator of A. talpoideum, limiting its growth and controlling its recruitment.[7]

References

  1. ^ a b c Parra-Olea, G.; Wake, D.; Hammerson, G.A. (2008). "Siren intermedia". IUCN Red List of Threatened Species. 2008: e.T59491A11936674. doi:10.2305/IUCN.UK.2008.RLTS.T59491A11936674.en. Retrieved 19 November 2021.
  2. ^ Lesser siren (siren intermedia). Species Profile: Lesser Siren (Siren intermedia) | SREL Herpetology. (n.d.). Retrieved April 28, 2022, from https://srelherp.uga.edu/salamanders/sirint.htm
  3. ^ a b Caudata Culture Species Entry – Siren intermedia. Caudata.org. Retrieved on 2019-12-23.
  4. ^ a b c d e f Reinhard, Sandy, et al. “External Fertilisation and Paternal Care in the Paedomorphic Salamander Siren Intermedia Barnes, 1826 (Urodela: Sirenidae).” Zoologischer Anzeiger - a Journal of Comparative Zoology, vol. 253, no. 1, August 2013, pp. 1–5, 10.1016/j.jcz.2013.06.002. Accessed 25 March 2022.
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Lesser siren: Brief Summary

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The lesser siren (Siren intermedia) is a species of aquatic salamander native to the eastern United States and northern Mexico. They are referred to by numerous common names, including two-legged eel, dwarf siren, and mud eel. The specific epithet intermedia denotes their intermediate size, between the greater siren, Siren lacertina, and the dwarf sirens, Pseudobranchus species.

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