Apalone spinifera emoryi
Apalone spinifera emoryi
(Texas Spiny Softshell)
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Apalone spinifera emoryi (Agassiz, 1857)

Common name: Texas Spiny Softshell

Taxonomy: available through www.itis.govITIS logo

Identification: Like most trionychids (softshells), Apalone spinifera lacks a hard shell and has a greatly flattened body (Behler and King, 1979; Conant and Collins, 1998; Powell et al., 1998).  Unlike Apalone ferox, the Florida Softshell, A. spinifera has a circular, rather than oblong, carapace (upper shell); the carapace length is 180-540 mm (7-21.25 in) (Ernst et al., 1994; Conant and Collins, 1998).  Unlike other North American Apalone, most males have tiny projections covering part of the carapace giving it a sandpaper-like feel with a row of spines along the anterior edge of the carapace, and usually retain a juvenile pattern of dark (or white in western subspecies) spots (large and circular or tiny blotches) (Conant and Collins, 1998).  Adult females have a smooth, typically patternless carapace, usually (lacking in some) adorned with a row of spines or single row of tubercles of variable size along its anterior edge (Stebbins, 1985; Conant and Collins, 1998).  This combination of features of the carapace separates Spiny Softshells from A. ferox and Apalone mutica (Smooth Softshell).  Like A. ferox, but unlike A. mutica, spiny sofshells have horizontal ridges projecting from the nasal septum (Collins, 1993; Ernst et al., 1994; Conant and Collins, 1998; Powell et al., 1998).  The pale background color of juvenile A. spinifera does not compare to the darker, more colorful patterning of juvenile A. ferox (Conant and Collins, 1998).  See the species account titled "Apalone ferox (Schneider, 1783)" on this website. 

There are currently six recognized subspecies (geographic races) of Spiny Softshells (Webb, 1973; Conant and Collins, 1998; Iverson et al., 2000):  Apalone spinifera aspera (Agassiz, 1857), Gulf Coast Spiny Softshell; A. s. emoryi (Agassiz, 1857), Texas Spiny Softshell; A. s. guadalupensis (Webb, 1962), Guadalupe Spiny Softshell; A. s. hartwegi (Conant and Goin, 1948), Western Spiny Softshell; A. s. pallida (Webb, 1962), Pallid Spiny Softshell; A. s. spinifera (Lesueur, 1827), Eastern Spiny Softshell.  Ernst et al. (1994), and Conant and Collins (1989) should be consulted for morphological differences between the six subspecies.  Spiny Softshells have been widely illustrated by numerous authors (Carr, 1952; Smith, 1961; Ernst and Barbour, 1972, 1989; Stebbins, 1972, 1985; Mount, 1975; Behler and King, 1979; Pritchard, 1979; Martof et al., 1980; Caldwell and Collins, 1981; Vogt, 1981; Smith and Brodie, 1982; Cook, 1984; Obst, 1986, 1998; Garrett and Barker, 1987; Green and Pauley, 1987; Dundee and Rossman, 1989; Harding and Holman, 1990; Carmichael and Williams, 1991; Collins, 1993; Ernst et al., 1994; Oldfield and Moriarty, 1994; Palmer and Braswell, 1995; Degenhardt et al., 1996; Conant and Collins, 1998; Powell et al., 1998; Behler, 1999; Hammerson, 1999; Phillips et al., 1999; Johnson, 2000; Hulse et al., 2001; Minton, 2001; Zug et al., 2001).

Size: 180-540 mm carapace length

Native Range: Apalone spinifera is a wide-ranging species occurring almost continuously throughout the Central Plains states from northern Mexico to as far north as South Dakota; throughout the Midwest states ranging north to Minnesota, Wisconsin, Michigan, and Ontario, Canada; east to western West Virginia, Pennsylvania and New York, with disjunct populations Quebec, Canada, and in eastern New York and Vermont; throughout the Coastal Plains and Gulf Coast states starting from southern North Carolina ranging southward and westward to the western Panhandle of Florida and extreme northeastern Florida (Bishop, 1923; Martof, 1956; Smith, 1961; Webb, 1970; Mount, 1975; Vogt, 1981; DeGraaf and Rudis, 1983; Cook, 1984; Lynch, 1985; Garrett and Barker, 1987; Green and Pauley, 1987; Moler, 1988; [Sievert] and Sievert, [1988]; Carpenter and Krupa, 1989; Dundee and Rossman, 1989; Harding and Holman, 1990; Ashton and Ashton, 1991; Carmichael and Williams, 1991; Gibbons and Semlitsch, 1991; Collins, 1993; Mitchell, 1994; Oldfield and Moriarty, 1994; Palmer and Braswell, 1995; Casper, 1996; Conant and Collins, 1998; Bartlett and Bartlett, 1999a, b; Phillips et al., 1999; Ballinger et al., 2000; Dixon, 2000; Johnson, 2000; King, 2000; Hulse et al., 2001; Minton, 2001).  The western border of the range of Spiny Softshells extends into river systems from Wyoming, Colorado and New Mexico, including disjunct areas in eastern Wyoming and the Missouri River drainage of Montana (Webb, 1973; Stebbins, 1985; Iverson, 1992; Ernst et al., 1994; Hammerson, 1999; Conant and Collins, 1998).

Apalone s. emoryi is confined to the Rio Grande and Pecos River drainages of Texas and New Mexico, south to the Río Purificación, Tamaulipas, Mexico, with an isolated colony in east-central Arizona (Smith and Smith, 1973, 1976, 1979, 1993; Webb, 1973; Stebbins, 1985; Iverson, 1992; Flores-Villela, 1993; Ernst et al., 1994; Stuart, 1995, 2000; Degenhardt et al., 1996; Conant and Collins, 1998).

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Nonindigenous Occurrences: In California, individual A. s. emoryi have been collected from the San Pablo Reservoir, Contra Costa County, and the San Gabriel River, Los Angeles County (Bury and Luckenbach, 1976; Stebbins, 1985).  Two additional A. s. emoryi from California were collected from Kern County, one in 1989 and another from Bakersfield, no date (D. Holland, personnal communication 1997).  Other California records include a Texas Spiny Softshell collected in 1994 from El Dorado Park, Long Beach, Los Angeles County (D. Holland, personal communication 1997), those found in the Lower Otay Reservoir and San Diego River, San Diego County (Stebbins, 1985), individuals seen or collected in 1999 from Coyote Creek and Vasona Reservoir, Los Gatos Creek (tributary to Guadalupe River), Santa Clara County (J. Abel, personal communication 2001), and individuals observed in the Sacramento River system (counties not listed) by C. Swolgaard (J. Quinn, personal communication 2000).

A Spiny Softshell was collected in Suffolk County, Massachusetts, in 1988 (Cardoza et al., 1993).

In Nevada, A. s. spinifera were collected in the Meadow Valley Wash and Colorado, Moapa, and Virgin Rivers (Bradley and Deacon 1967). 

In New Jersey, A. s. spinifera were collected from Cooper's Creek, Camden County, in 1902; Kearn's Lake, Elmer, in the years 1949, 1957, 1959,and 1960, Palatine Lake in 1954, and observed in Rainbow Lake and Willow Grove Lake in 1961, Salem County (Conant, 1961).  Conant (1961) indicated that this was evidence they had dispersed via the Maurice River.  The Eastern Spiny Softshell is now found throughout the Maurice River System of New Jersey (Conant and Collins, 1998), which includes Cumberland County.

Apalone s. emoryi was probably introduced into the Gila-Colorado River System from New Mexico around 1900 (Miller, 1946; Stebbins, 1985; Degenhardt et al., 1996; Conant and Collins, 1998).  They have since spread throughout this river system from extreme southwestern Utah, eastern Nevada, southwestern Mew Mexico, and Arizona, to the head of the Gulf of California, Imperial Valley, Imperial Valley County and Riverside County to the Salton Sea, California, and into Mexico (Bury and Luckenbach, 1976; Stebbins, 1972, 1985; Ernst et al., 1994; Conant and Collins, 1998).  In Arizona, nonindigenous records of Texas Spiny Softshells include individuals collected in the Papago Park Ponds, Maricopa County (M. Demlong, personal communication 1997), and in the Alamo Lake on Bill Williams River on the border of Mohave and La Paz Counties (Jones, 1988).

In 1982, an A. s. spinifera was collected from a small pond in Fairfax County, Virginia (Ernst et al., 1997; C. Ernst, personal communication 1997).

Means of Introduction: The means of introduction of A. s. spinifera in Massachusetts and Virginia are unknown but pet releases or escapes are likely.

The A. s. spinifera in Camden County, New Jersey, may have been intentionally introduced to stock aquaria (Conant, 1961).  Those found in the Maurice River system of New Jersey were intentionally introduced from Indiana in order to establish a breeding population (Conant, 1961).

Apalone s. emoryi in the Gila-Colorado river system may have escaped from an aquaculture pond on a ranch in New Mexico, around 1900, during a flood (Miller, 1946).  Their spread throughout this river system, since their original escape, into the states of Arizona, Utah, Nevada, and California, has been through natural dispersal (Bury and Luckenbach, 1976; Stebbins, 1972, 1985).  Other A. s. emoryi collected or seen in other parts of California are of unknown origin, but probably anthropogenic.

Status: Eastern Spiny Softshells were collected and are not established in Massachusetts (Cardoza et al., 1993) or Virginia (Ernst et al., 1997).

In New Jersey, A. s. spinifera is currently well-established throughout the Maurice River system but probably not Camden County (Conant, 1961;Webb, 1973; Smith and Kohler, 1978; Ernst et al., 1994; Conant and Collins, 1998).  Their slow dispersal through this river system does not seem to indicate that they are highly invasive in New Jersey.

Apalone s. emoryi is currently well-established and invasive throughout the Gila-Colorado River systems in southwestern New Mexico, Arizona (including Alamo Lake on the Bill Williams River), southwestern Utah, eastern Nevada, southern California (including the Salton Sea and San Diego River), and into Mexico to the Gulf of California (Degenhardt and Christiansen, 1974; Smith and Kohler, 1978; Endemic Species Committees, 1982; Stebbins, 1985; Jones, 1988; Degenhardt et al., 1996; Howland, 1996; Conant and Collins, 1998).  In California, A. s. emoryi also is established in the Lower Otay Reservoir, San Diego County (Stebbins, 1985).  The status of individuals collected or observed from the San Pablo Reservoir (Contra Costa County), San Gabriel River and Long Beach (Los Angeles County), Coyote Creek/Guadalupe River system (Santa Clara County), and the Sacramento River system (counties not specified) remains uncertain (Stebbins, 1985; D. Holland, personal communication 1997; J. Quinn, personal communication 2000; J. Abel, personal communication 2001).  Texas Spiny Softshells from Kern County, California (D. Holland, personal communication) may only represent single waifs, not a breeding population.  However, it seems clear that Spiny Softshells are an invasive species in California and may be able to increase its range by dispersing through intersecting artificial canals.

Impact of Introduction: While the impact of the introduction of spiny sofshells throughout various localities in the United States and Mexico remains unknown, established populations in Maurice River system of New Jersey, the Gila-Colorado River system of California, Utah, Arizona, New Mexico, Mexico and Nevada, and the Lower Otay Reservoir and San Diego River of California all occur in localities were there are no native Apalone.  Clearly they could have some impact upon indigenous ecosystems in these regions.

Remarks: The taxonomy of A. spinifera has been reviewed or summarized by Webb (1973, 1989, 1990), Meylan (1987), Iverson et al. (2000), and Weisrock and Janzen (2000).  Webb (1990) has called for retaining the genus name Trionyx for all North American trionychids without providing any detailed evidence (Webb's opinion is accepted by Ernst et al., 1994), but most authorities (Conant and Collins, 1998; Iverson et al., 2000; Weisrock and Janzen, 2000) follow Meylan's (1987) groundbreaking revision placing all North American softshells under Apalone.  Summaries on the literature and natural history of Spiny Softshells can be found in Webb (1973), Ernst and Barbour (1989), Ernst et al. (1994), and Hammerson (1999).  Scientific and standard English names follow Crother (2008).

Apalone spinifera is a highly aquatic species that prefers highly-oxygenated rivers, but also inhabits creeks, canals, impoundments, lakes, and oxbows; especially those with a soft bottom, sandbars or mud flats (Stebbins, 1985; Ernst et al., 1994; Conant and Collins, 1998; Hammerson, 1999).  Like many softshells, they may spend some time buried in the soft bottom with only the head protruding (Ernst and Barbour, 1989; Ernst et al., 1994).  While submerged under water they may supplement respiration through gas exchange across the linings of the pharynx and cloaca (Ernst et al., 1994).  Spiny Softshells are carnivores that eat fish, carrion, crayfish, insects, and a wide variety of other invertebrates (Carr, 1952; Ernst and Barbour, 1989; Ernst et al., 1994).  Females lay 4-39 eggs, during late spring or summer, which they bury in soil exposed to sunlight, often near sand or gravel bars, or further away from water if the proper nest environment is not close (Minton, 1972; Vogt, 1981; Ernst and Barbour, 1989; Ernst et al., 1994; Hammerson, 1999).

Like most softshells, A. spinifera is difficult and dangerous to handle because of its sharp claws, sharp, powerful jaws and long protrusive neck; they are quick to defend themselves (Carr, 1952; Conant and Collins, 1998), and also are aggressive toward conspecifics (Ernst et al., 1994).  In North America, Apalone species are commonly exploited and exported for the commercial trade in the Asian market (Zug et al., 2001).

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Author: Somma, L.A.

Revision Date: 10/28/2009

Citation Information:
Somma, L.A., 2017, Apalone spinifera emoryi (Agassiz, 1857): U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, https://nas.er.usgs.gov/queries/FactSheet.aspx?speciesID=1275, Revision Date: 10/28/2009, Access Date: 10/23/2017

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Citation information: U.S. Geological Survey. [2017]. Nonindigenous Aquatic Species Database. Gainesville, Florida. Accessed [10/23/2017].

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