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Spiny softshell turtle
Apalone spinifera.jpg
Conservation status
Scientific classification
Genus:
Apalone
Species:
spinifera
Apalone spinifera map.svg
Synonyms
Apalone spinifera spinifera
  • Trionyx nasica
    Rafinesque, 1822
    (nomen suppressum)
  • Trionyx spiniferus
    LeSueur, 1827
  • Apalone hudsonica
    Rafinesque, 1832
  • Gymnopus spiniferus
    — A.M.C. Duméril & Bibron, 1835
  • Trionyx annulifer
    Wied, 1839
  • Tyrse argus
    Gray, 1844
  • Trionyx annulatus
    Gray, 1856
  • Trionyx argus
    — Gray, 1856
  • Gymnopodus spiniferus
    — A.H.A. Duméril, 1856
  • Aspidonectes nuchalis
    Agassiz, 1857
  • Aspidonectes spinifer
    — Agassiz, 1857
  • Gymnopus spinifer
    — Agassiz, 1857
  • Trionyx spinifer
    — Agassiz, 1857
  • Gymnopus olivaceus
    Wied, 1865
  • Callinia spicifera
    Gray, 1869
  • Callinia spinifera
    — Gray, 1870
  • Platypeltis nuchalis
    — Baur, 1893
  • Platypeltis spinifer
    — Baur, 1893
  • Tyrse spinifera
    — O.P. Hay, 1904
  • Amyda spinifera
    — O.P. Hay, 1905
  • Platypeltis spinifera
    — O.P. Hay, 1907
  • Amyda spinifer
    — Potter, 1920
  • Amyda spinifera spinifera
    — Stejneger & T. Barbour, 1939
  • Trionyx spinifera spinifera
    — Cagle, 1941
  • Amyda ferox spinifera
    — Neill, 1951
  • Trionyx ferox spinifera
    — Schmidt, 1953
  • Trionyx spinifer spinifer
    — Schwartz, 1956
  • Trionyx spiniferus spiniferus
    — Wermuth & Mertens, 1961
  • Apalone spinifera
    — Meylan, 1987
  • Apalone spiniferus
    — Meylan & Webb, 1988
  • Apalone spinifera spinifera
    — Ernst & R. Barbour, 1989
  • Apalone spinifera spinifera
    — Stubbs, 1989
  • Trionix spiniferus
    — Richard, 1999

The spiny softshell turtle (Apalone spinifera) is a species of softshell turtle, one of the largest freshwater turtle species in North America. Both the common name, spiny softshell, and the specific name, spinifera (spine-bearing), refer to the spiny, cone-like projections on the leading edge of the carapace, which are not scutes (scales).

Description

The spiny softshell turtle's scientific name is very descriptive of the animal. Apalone comes from the Greek word apalos, meaning soft or tender, and spinifera is of Latin origin; spina- referring to thorn or spine and -ifer meaning bearing. This species is a member of the family Trionychidae, and one of the most distinguishing features of members in this family is the presence of a leathery, moderately flexible carapace. This is caused by loss of keratinized scutes and some bony tissue loss. Spiny softshell turtles have webbed feet, each with three claws. Another distinguishing feature of softshell turtles is the presence of a fleshy, elongated nose.

The carapace (the upper part of the shell) ranges from brown or yellow-brown to olive in color, while the plastron (lower part of the shell) is lighter, usually white or yellow. Hatchlings usually have dark spots on the carapace, but as females age, they frequently become darker in color, or their carapace becomes splotched. Males tend to maintain the same coloration pattern from birth. Coloration also varies between each subspecies, and the exact coloration can also depend on an individual turtle's environment. Spiny softshell turtles are cryptically colored, meaning that their coloration helps them blend in with their surrounding environment.

Spiny softshell turtles also have pale lines bordered by black lines running from its head down the side of its neck. The carapace length ranges from 18-54 cm, with females growing larger than males. The namesake spines are found along the anterior border of the carapace and are more commonly found in males. The variation in coloration, size, and spine presence indicates that this species exhibits sexual dimorphism.

Respiration

A. spinifera turtles are bimodal breathers, meaning they have the ability (to some degree) to perform oxygen and carbon dioxide exchange by breathing air or while breathing underwater. A variety of factors allow for these turtles to perform respiration underwater. They have an increase of cutaneous surface area and blood flow, reduction in lung size, and increase of respiratory epithelium in the cloaca and buccopharynx. Spiny softshell turtles are more dependent on underwater respiration than other freshwater species. This has led to their low tolerance of hypoxic waters; this becomes especially important during times of hibernation, when these turtles must choose hibernacula that are unlikely to become hypoxic.

Geographic range

The spiny softshell has a wide range, extending throughout much of the United States, as well as north into the Canadian provinces of Ontario and Quebec, and south into the Mexican states of Tamaulipas, Nuevo León, Coahuila and Chihuahua.

Ecological range

The spiny softshell can be found in bodies of fresh water including ponds, lakes, rivers, tributaries, and streams. They inhabit shallow water (less than 1 m deep), but can also be found as far as 10 m deep. They can be found in areas with varying levels of vegetation, and although they are generally found in more slow-moving waters, this species can be found in fast-moving waters than other, less-aquatic species of turtles. Spiny softshells prefer waters with sandy bottoms and clean, sandy banks. Sandy environments are important for nesting sites, proper juvenile growth and development, and camouflage. Spiny softshells migrate between warm and cold seasons. In each season, turtles generally stay in a single zone, and they move more within their zone during warm months.

Diet

Spiny softshell turtles feed on a variety of food items. They commonly consume insects, crayfish, fish, algal stocks and other plant material, and mussels. They are generally observed as benthic feeders; they can either actively hunt prey or bury themselves in the sand and wait to ambush prey.

Taxonomy

The species was first described by Charles Alexandre Lesueur in 1827. It has been redescribed numerous times, leading to some confusion in its taxonomy. The recognized subspecies differ in the markings on their carapaces, on the sides of their heads, and on their feet. These markings, which are distinct as hatchlings, fade as the turtles grow larger. Adult females of the various subspecies, which grow larger than males, are not easily distinguishable from one another, and sometimes can only be assigned to a particular subspecies based on geography.

Reproduction

Spiny softshells begin mating between ages 8 and 10. A large female turtle may live up to 50 years. The turtles mate in mid-to-late spring in deep water. The male will nudge the female's head while swimming, and if she chooses to mate, the male will swim above the female without clasping her with his claws (unlike other turtles). A few months later, the female turtle quickly lays her eggs along a sunny sandbar or gravel bank in a flask-shaped cavity she has dug close to the water. The turtle nests more than once during a single season. She can lay between 9 and 38 round, calcareous-shelled eggs. The eggs are laid around July and September, and they hatch in the spring. Unlike in other turtles, in the spiny softshell turtle, the sex of the hatchlings is not determined by temperature variations; it is determined by genetics. The nesting sites are at risk of predation from animals such as coyotes, foxes, and raccoons.

Subspecies

Six subspecies of A. spinifera are recognized, including the nominate subspecies:

A previously recognized subspecies, Apalone spinifera hartwegi (Conant & Goin, 1941), has been synonymized to A. s. spinifera as of 2011.

Genomics

A rough-draft assembly of the A. spinifera aspera genome was completed in 2013 by the Genome Institute at Washington University - St. Louis. The assembly ASM38561v1 can be accessed via its Genbank accession ID APJP00000000.1 [1]

Gallery

Bibliography
  • Behler JL, King FW (1979). The Audubon Society Field Guide to North American Reptiles and Amphibians. New York: Alfred A. Knopf. 743 pp. ISBN: 0-394-50824-6. (Trionyx spiniferus, pp. 485–486 + Plates 270, 271).
  • Boulenger GA (1889). Catalogue of the Chelonians, Rhynchocephalians, and Crocodiles in the British Museum (Natural History). New Edition. London: Trustees of the British Museum (Natural History). (Taylor and Francis, printers). x + 311 pp. + Plates I-III. (Trionyx spinifer, pp. 259–260).
  • Lesueur CA (1827). "Note sur deux espèces de tortues, du genre Trionyx de M[onsieur]. Geoffroy-Saint-Hilaire ". Mémoires du Muséum d'Histoire Naturelle, Paris 15: 257-268 + Plates 6-7. (Trionyx spiniferus, new species, pp. 258–263 + Plate 6). (in French).
  • Smith HM, Brodie ED Jr (1982). Reptiles of North America: A Guide to Field Identification. New York: Golden Press. 240 pp. ISBN: 0-307-13666-3. (Trionyx spiniferus, pp. 31–33).
  • Stejneger L, Barbour T (1917). A Check List of North American Amphibians and Reptiles. Cambridge Massachusetts: Harvard University Press. 125 pp. (Amyda spinifera, p. 125).
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