Apalone spinifera

Geographic Range

Apalone spinifera occupies areas from central-eastern U.S. (western New York and southern Carolina) to Wisconsin and from Minnesota and southern Ontario as far south as Mexico. The eastern spiny soft-shell turtle ( A. spinifera spinifera ) occupies the ranges from western New York to Wisconsin south to the Tennessee River, with a population in the lower part of Canada, by the Ottawa River. The Western spiny soft-shell ( A. spinifera hartwegi ) occupies territory that ranges from Minnesota to Arkansas west to south east Wyoming, eastern Colorado, and north eastern New Mexico, with a large population in the Missouri River drainage in Montana. The Gulf spiny soft-shell turtle ( A. spinifera aspera ) can be found from northern Carolina to Alabama and south to the northern tip of Florida. The Guadalupe subspecies ( A. spinifera guadalupensis ) can be found from south central Texas to the Colorado river system. The Pallid subspecies ( A. spinifera pallida ) can be found in western Louisiana to southern Oklahoma, and most of the northern and eastern parts of Texas. The Texas subspecies ( A. spinifera emoryi ) occupies the Rio Grande to the Pecos river drainages and south to Rio Purificacion, Tamaulipas and also from southwest new Mexico and south west Utah to the Gulf of California with an isolated population in eastern central Arizona (Conant and Collins 1998).

• Biogeographic Regions
• nearctic nearctic
  • native native

Habitat

Apalone spinifera inhabits various freshwater systems such as rivers, lakes, marshes, farm ponds (Behler and King 1998) as well as bays of the Great Lakes . Apalone spinifera prefers open habitats with a small amount of vegetation and a sandy or muddy bottom and require sandy raised nesting areas close to water (Harding 1997).

• Habitat Regions
• temperate temperate
• freshwater freshwater

• Aquatic Biomes
• lakes and ponds
• rivers and streams

Physical Description

Spiny softshell turtles have soft, flat, rounded carapaces without scutes. The edges are pliable with small spines, in the eastern subspecies the spines are toward the front of the carapace. Some subspecies have the spines on the posterior part of the carapace ( A. s. pallida ) while some have them on most parts of the carapace (Behler and King 1998). The nose is long, tapered, and upturned at the end with ridges (Harding 1997). Unlike gulf spiny soft-shell turtles ( A. s. aspera ), with two distinct black-bordered yellow stripes on each side of the head that come together before the long neck, eastern spiny soft-shell turtles ( A. spinifera spinifera ) have two black-bordered yellow stripes that travel along the neck and do not connect (Conant and Collins 1998). The plastron is whitish or yellow with bones visible underneath. They have claws and their feet are webbed for swimming. The body is olive or tan with black speckles and a dark rim around the edge of their carapace. In A. s. aspera two or more dark lines can be found bordering the rear margin of the shell and in A. s. pallida , the black ring is lacking. Some subspecies have whitish spots on their whole carapace, the posterior half of their carapace, or on the rear third of their carapace, these subspecies being A. s. guadalupe , A. s. pallida , and A. s. emoryi respectively. These characteristics intergrade where hybrid zones occur. There is some sexual dimorphism. Adult males retain the juvenile's olive and yellow coloration with black "eyespots", have a slightly rougher carapace than females, and are smaller than females, with a carapace length of 12.7 to 24 cm. Males also have longer and thicker tails that females. The carapace of females darkens during adulthood and becomes a mottled gray. The length ranges from 24 to 48 cm and the tail barely extends past the edge of her carapace.

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

• Sexual Dimorphism
• female larger
• sexes shaped differently

Development

Sex is not determined by temperature variations in A. spinifera .

Reproduction

In courtship, males 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 most other turtles).

• Mating System
• polygynandrous (promiscuous) polygynandrous (promiscuous)

Spiny softshell turtles sexually mature between the ages of 8 to 10 years. They mate in mid to late spring in deep water. Apalone spinifera females lay clutches along a sunny sandbar or gravel bank in a flask-shaped cavity that they dig close to water as quickly as possible (usually within an hour). Spiny softshell turtles sometimes nest more than once during a single season. Females lay between 9 and 38 round calcareous-shelled eggs. The eggs hatch around August and September. Clutches can even incubate through the winter and hatch in the spring.

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

Females invest energy into supplying their eggs with nutrients for development and deposit them into a safe nest. Once the eggs are laid there is no further parental investment.

• Parental Investment
• no parental involvement
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female

Lifespan/Longevity

Estimated longevity in spiny softshell turtles is up to fifty years in a large female.

Behavior

Spiny softshell turtles are diurnal animals, spending most of the day basking in the sun and foraging for food. They can be spotted sunning on logs and river banks. If disturbed, they will quickly retreat into the water and bury themselves in sand, leaving only their heads visible. These turtles are also able to breathe underwater for extended periods through their pharyngeal lining, cloacal lining, and skin. Spiny softshell turtles spend October to April in the water buried underneath substrate in a state of dormancy.

• Key Behaviors
• natatorial natatorial
• diurnal diurnal
• motile motile
• sedentary sedentary
• hibernation hibernation
• solitary solitary

Communication and Perception

Spiny softshell turtles use their sense of vision and touch to find prey. When they mate they respond to tactile stimulation.

• Communication Channels
• tactile tactile

• Perception Channels
• visual visual
• tactile tactile
• vibrations vibrations
• chemical chemical

Food Habits

Apalone spinifera preys on on various macroinvertebrates such as aquatic insects, crayfish, and occasionally a fish. They find their food underneath objects, along the floor of the lake, and in vegetation. They also hide in the floor substrate and grab prey as they swim by (Harding 1997).

• Primary Diet
• carnivore carnivore
  • insectivore insectivore
  • eats non-insect arthropods

• Animal Foods
• amphibians
• fish
• insects
• mollusks
• terrestrial worms
• aquatic crustaceans

Predation

Spiny softshell turtle nests are often destroyed by raccoons, skunks, and foxes. Young softshell turtles are eaten by raccoons, herons, and fish. Adults are killed and eaten only by humans, they have few natural predators. When bothered, spiny softshell turtles will extend their long necks and snap viciously at their attacker, inflicting a painful bite. They are wary and can hide themselves quickly.

• Anti-predator Adaptations
• cryptic cryptic

Ecosystem Roles

Spiny softshell turtles are important predators in aquatic systems, impacting populations of crustaceans and aquatic insects.

Spiny softshell turtles are important members of the ecosystems where they live. They prey on aquatic insects and crustaceans.

Economic Importance for Humans: Positive

Spiny softshell turtles are sometimes marketed for human consumption and some places have made laws dealing with catch limits, catch seasons, as well as size limitations.

• Positive Impacts
• food food

Economic Importance for Humans: Negative

It was once thought that spiny softshell turtles damaged game fish populations. However, all data shows that these animals have no impact on game fish populations or humans whatsoever. If handled, they can aggressively defend themselves and inflict painful bites.

• Negative Impacts
• injures humans
  • bites or stings

Conservation Status

Because A. spinifera respire aquatically with pharyngeal gill slits and cloaca, they are vulnerable to Rotenone, a chemical that is used to kill unwanted fish. Rotenone hinders oxygen absorption and many soft shell turtles are now gone from Rotenone contaminated waters in the Great Lakes. Habitat fragmentation and shoreline development continues to threaten nesting sites. Along with other turtles, A. spinifera is hunted or shot for "fun" and human consumption. Eggs, hatchlings, and juveniles are threatened by various human activities and vulnerable to predators such as raccoons, foxes, and skunks, all of which thrive in areas of human development. They are not listed as endangered, vulnerable, or threatened by the IUCN, CITES, or the U.S. Endangered Species Act.

Other Comments

Spiny softshell turtles were previously known as Trionyx spiniferus . There are several subspecies including Eastern, Western, Gulf Coast, Pallid, Guadalupe, and Texas.

Additional Links

Encyclopedia of Life

BioKIDS Critter Catalog

Contributors

David Armitage (editor), Animal Diversity Web.

Pamela Bartholomew (author), Michigan State University, James Harding (editor), Michigan State University.

References

Behler, J., F. King. 1998. National Audubon Society Field Guide to North American Reptiles and Amphibians . Alfred A. Knopf, Inc..

Conant, R., J. Collins. 1998. A Field Guide to Reptiles and Amphibians; Eastern and Central North America . New York: Houghton Mifflin Co..

Harding, J. 1997. Amphibians and Reptiles of the Great Lakes Region . Ann Arbor: University of Michigan Press.