Leptoxis plicata 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Mollusca Gastropoda Sorbeoconcha Pleuroceridae

Scientific Name: Leptoxis plicata (Conrad, 1834)
Common Name(s):
English Plicate Rocksnail
Anculosa plicata Conrad, 1834
Taxonomic Source(s): Johnson, P.D., Bogan, A.E., Brown, K.M., Burkhead, N.M., Cordeiro, J.R., Garner, J.T., Hartfield, P.D., Lepitzki, D.A.W., Mackie, G.L., Pip, E., Tarpley, T.A., Tiemann, J.S., Whelan, N.V. and Strong, E.E. 2013. Conservation status of freshwater gastropods of Canada and the United States. Fisheries 38(6): 247-282.
Taxonomic Notes: The genus Leptoxis was formerly called Anculosa (Goodrich, 1922). The genus Leptoxis is a difficult group. There is considerable disagreement in regard to the number of valid species (Goodrich 1922, Burch 1982). Dillon and Lydeard (1998) found high levels of genetic divergence among populations of Leptoxis praerosa and Leptoxis plicata and from all other populations of Leptoxis studied, indicating they are distinct species. In a preliminary analysis of molecular phylogeny of Mobile River basin pleurocerids, Lydeard et al. (1997) concluded that Leptoxis picta and Leptoxis plicata are quite distinct from one another and all other pleurocerids studied, while Leptoxis taeniata and Leptoxis ampla are sister taxa, and Leptoxis picta the most basal of the group.

Assessment Information [top]

Red List Category & Criteria: Critically Endangered B1ab(i,ii,iv) ver 3.1
Year Published: 2011
Date Assessed: 2011-08-01
Assessor(s): Cordeiro, J. & Perez, K.
Reviewer(s): Böhm, M. & Collen, B.
Contributor(s): Bogan, A.E., Dyer, E., Soulsby, A.-M., Whitton, F., McGuinness, S., De Silva, R., Milligan, H.T., Kasthala, G., Herdson, R., Thorley, J., McMillan, K. & Collins, A.
Leptoxis plicata has been assessed as Critically Endangered under criterion B1ab(i,ii,iii,iv) due to its restricted distribution. The occurrence of this species has been restricted by 90% leaving less than 32 linear km of occupied habitat. This habitat is patchy and continues to decline under the impact of many threats. The one extant population exists in a short reach of stream in 15 shoals half of which appear to be declining.
Previously published Red List assessments:

Geographic Range [top]

Range Description:In the past, this species has been reported by Goodrich (1938, 1941) from forks of the Black Warrior River, Walker County, the Black Warrior River in Jefferson County (including Valley Creek, Burch 1989) and at Tuscaloosa Co.; the Little Black Warrior River and the Tombigbee River (Stein 1976).

The current range of the species is limited to a short reach of the Locust Fork of the Black Warrior River in Jefferson and Blount Counties, Alabama (Hartfield 1994, USFWS 1995, 2000, 2004, 2005). Recent status surveys have located Plicate Rocksnail populations only in an approximately 88 km (55 mile) reach of the Locust Fork of the Black Warrior River, Jefferson and Blount counties, Alabama (USFWS 2005). The latest survey information indicates that the snail has recently disappeared from the upstream two-thirds portion of that habitat and now appears to be restricted to an approximately 32 km (20 mile) reach in Jefferson County (USFWS 2005). As such the current extent of occurrence falls well within the Critically Endangered category threshold.

Three subpopulations can be considered as one location, due to the threat of pollution and impoundment potentially severely impacting the entire location.
Countries occurrence:
United States (Alabama)
Additional data:
Number of Locations:1
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:Extensive surveys have located only one population. Historically, there were many more (Hartfield 1994, USFWS 2005). The current population consists of subpopulations on fifteen shoals in 30 km reach of Locs Fork (Black Warrior drainage), Jefferson County, between Kimberly and Sayre (Mirarchi et al. 2004, USFWS 2000, 2004, 2005). There are less than three shoals with a high density of snails.

It appears to be declining in the Locust Fork of the Black Warrior River where it recently occurred in about an 88 km stretch, but now exists in about a 32 km reach (USFWS 2005). Biologists conducting recent surveys have noted the disappearance of the species from one reach of stream since the work began on the species (P. Hartfield pers. comm. 1996). A 50% reduction in range has occurred in the last decade.

Decline since the early 20th century is documented as the species has disappeared from over 90% of its historic range where it formerly occurred in the Black Warrior River, Little Warrior River and Tombigbee River (USFWS 2004, 2005).
Current Population Trend:Decreasing
Additional data:

Habitat and Ecology [top]

Habitat and Ecology:This species requires shallow flowing water over gravel, cobble, or bedrock in the strong currents of rapids and shoals (Hartfield 1994, USFWS 2000, 2005).

Threats [top]

Major Threat(s): The main threat to this species is habitat modification. A proposed impoundment within the reach of habitat for the existing population would bisect the current known range (USFWS 1995). Other impacts which threaten this species include channel modification, agriculture, silviculture, cattle grazing, mining, drainage from unpaved roads, industrial and residential development (Bogan and Pierson 1993). Curtailment of habitat and range in the Mobile River Basin's larger rivers (Coosa, Alabama, Tombigbee and Black Warrior) due to extensive construction of dams and inundation of the snails shoal habitats by impounded waters (snails have disappeared from all portions of historic habitats that have been impounded by dams). Short and long-term impacts of point and non-point source water and habitat degradation continue to be a primary concern, compounded by population isolation and localization (USFWS 2004, 2005).

In the Mobile River basin, the greatest threats are dams (navigation, water supply, electricity, recreation, and flood control), channelization (causing accelerated erosion, altered depth, and loss of habitat diversity, substrate stability, and riparian canopy), dredging (for navigation or gravel mining), mining (for coal, sand, gravel and gold) in locally concentrated areas, pollution-point source (industrial waste effluent, sewage treatment  (USFWS 2000).

Conservation Actions [top]

Conservation Actions: The short reach of the Locust Fork where this species still persists is surrounded by private lands (Hartfield 1994). A captive breeding population has been established at the Southeast Aquatic Research Institute but breeding in captivity has not been successful (USFWS 2000). An ongoing captive propagation program started at the Tennessee Aquarium Research Institute should continue. Augmentation of the population in Locust Fork, using propagated juveniles, began in 2003 and continues. Reintroductions elsewhere should be considered where suitable habitat is found (Mirarchi et al. 2004).

This species was listed as federally endangered in the U.S. in 1998 (USFWS 1998). A recovery plan was drafted with the objective to delist the species (USFWS 2005):

Recovery Criteria:
Reclassification of the Cylindrical Lioplax (Lioplax cyclostomaformis), Flat Pebblesnail (Lepyriam showalteri) and Plicate Rocksnail (Leptoxis ampla); and the Painted Rocksnail (Leptoxis taeniata), Round Rocksnail (Leptoxis ampla), and Lacy Elimia (Elimia crenatella) will require confirmation of stability or increase in their existing populations for 10 or more years, establishment of captive populations, and identification or establishment of at least two additional populations for each species. Delisting of all six species will require the confirmation of at least three stable or increasing populations for each species for 10 or more years. Before either reclassification or delisting may be considered, threats to the species will be removed and plans should be developed and implemented to protect and monitor water and habitat quality in the watersheds where they occur.

Actions needed:
(1) Protect habitat integrity and water quality.
(2) Develop mitigation strategies that give high priority to avoidance and restoration.
(3) Promote increased levels of voluntary stewardship to reduce non-point source pollution from private land use.
(4) Encourage and support community based watershed stewardship planning and action.
(5) Develop and implement public education programs and materials defining ecosystem management and stewardship responsibilities.
(6) Conduct basic research on endemic species and apply the results of this research to management.
(7) Develop and implement technology for maintaining and propagating endemic species in captivity.
(8) Reintroduce imperiled aquatic species into restored habitats, as appropriate.
(9) Monitor listed species populations.
(10) Coordinate ecosystem management actions.

A specific recovery plan has been created for the Mobile River basin (USFWS 2000) which contains the following objectives: (1) protect habitat integrity and quality of river and stream segments that currently support it could support imperiled aquatic species, (2) consider options for free-flowing river and stream mitigation strategies that give high priority to avoidance and restoration, (3) promote voluntary stewardship as a practical and economical means of reducing non-point pollution from private land use, (4) encourage and support community based watershed stewardship planning and action, (5) develop and implement programs and materials to educate the public on the need and benefits of ecosystem management, and to involve them in watershed stewardship, (6) conduct basic basic research on endemic aquatic species and apply the results toward management and captivity, (8) reintroduce aquatic species into restored habitats as appropriate (9) monitor listed species population levels and distribution and periodically review ecosystem management strategy, (10) coordinate ecosystem management actions.

Further research is recommended to determine the extent of the existing population and an estimate of extant individuals. All populations should be monitored  periodically and habitat degradation identified and mitigated.

A survey for potential reintroduction sites within the Black Warrior River drainage should be conducted. An ongoing captive propagation program started at the Tennessee Aquarium Research Institute should continue. Augmentation of the population in Locust Fork, using propagated juveniles, began in 2003 and continues. Reintroductions elsewhere should be considered where suitable habitat is found (Mirarchi et al. 2004).

Citation: Cordeiro, J. & Perez, K. 2011. Leptoxis plicata. The IUCN Red List of Threatened Species 2011: e.T11783A3305444. . Downloaded on 22 August 2018.
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