Assiminea pecos

Pecos Assiminea

FWS Focus

Overview

Characteristics
Overview

Pecos assiminea (Assiminea pecos) is a very small, federally endangered snail found in a few locations of the Pecos River Basin in New Mexico and Texas. Snails in the Assiminea genus are primarily marine and usually associated with the sea, Pecos assiminea is found the furthest inland of all these species. They live in association with vegetation and under plant litter, in saturated soils near flowing springs and seeps. Significant threats to the species and its habitat are primarily correlated to deterioration of water quality and quantity, which is exacerbated by drought, as well the as impacts from intense wildfire and invasive plants and animals.     

Scientific Name

Assiminea pecos
Common Name
Pecos Assiminea
Pecos assiminea snail
FWS Category
Snails
Kingdom

Location in Taxonomic Tree

Identification Numbers

TSN:

Characteristics

Characteristic category

Physical Characteristics

Characteristics
Weight

No recorded weight measurements for Pecos assiminea are available at this time.

Physical Characteristics

Pecos assiminea (Assiminea pecos) is a very small golden snail found in a few locations of the Pecos River Basin in New Mexico and Texas. Snails in the Assiminea genus are primarily marine and usually associated with the sea, Pecos assiminea is found the furthest inland of all these species.   

Color & Pattern

The shell of Pecos assiminea is chestnut color and nearly translucent.  

Sound

Sounds have not been identified or recorded for Pecos assiminea. 

Size & Shape

Pecos assiminea range from 1.36 to 2.16 millimeters (0.05 to 0.08 inches) in shell length, with females being larger than males. Their shell has a broad, oval opening and is regularly conical, with up to 4.5 strongly incised whorls. The genus Assiminea does not have tentacles and their eyes are in the tips of short stalks.

Characteristic category

Similar Species

Characteristics
Similar Species

A population of snails along the Río Monclova in Coahuila, Mexico, were initially reported to be Pecos assiminea. They have since been described as a separate species, Assiminea cienegensis, which are genetically distinct and have a smaller and broader shell. 
 

Characteristic category

Life Cycle

Characteristics
Life Cycle

Individual Pecos assiminea snails are strictly male or female. Fertilization is internal, and females likely deposit eggs in gelatinous masses in their habitat where they develop into larvae. Little is known about specific development details in this species, other gastropods may reach sexual maturity in as few as six months. The seasonality, frequency of breeding, fecundity, or other aspects of reproduction are also unknown. Fluctuating surface water levels and winter freezing of inundated areas appear to be limiting factors influencing population size and individual mortality. 

Life Span

The lifespan of Pecos assiminea has not been recorded. 

Reproduction

Breeding habitat specifics or associated behavior has not been studied for this species. 

Characteristic category

Habitat

Characteristics
Habitat

Pecos assiminea is closely associated with permanent spring run wetland habitats, where they live in saturated mud with plant communities that are dominated by species like saltgrass (Distichlis spicata), chairmaker’s bulrush (Schoenoplectus americanus), common reed (Phragmites australis), spike rushes (Eleocharis spp.) and rushes (Juncus spp.). They are typically near the surface of the soil beneath mats of vegetation and plant litter, and may also rarely occur in the water of aquatic habitats. A balanced amount of vegetation litter is an important habitat component that provides food, shade, cover and maintains microhabitat temperature and moisture.

Grassland

Ecosystem with large, flat areas of grasses.

Desert

Area of land that receives no more than 25 centimeters (10 inches) of precipitation a year.

Cave or Karst
Lake
River or Stream
Urban
Rural
Wetland
Characteristic category

Food

Characteristics
Food

Pecos assiminea have a radula, an organ of tiny teeth, that they use to scrape food off of surfaces and into their mouth. They likely forage on the bacteria, detritus, fungi and algae found on live and dead vegetation and coarse organic matter. They may also incidentally consume small invertebrates as they feed.  

Characteristic category

Behavior

Characteristics
Behavior

Pecos assiminea respire by breathing air directly. They commonly maintain an air bubble in their mantle cavity, and have gills that are vestigial, or remnant, and not likely used for primary respiration. Pecos assiminea are presumably nocturnal and most active at night, which is similar to their neighboring gastropods. 

Geography

Characteristics
Range

When Pecos assiminea was described in 1987, snails were found at three isolated localities: in
Chaves County on BLNWR in New Mexico; Diamond Y Spring in Pecos County, Texas; and in
the Bolsón de Cuatro Ciénegas, Coahuila, Mexico (Taylor 1987: 9). Taylor (1987: 8-9) reported
extirpation of two locations in Chaves County: one at North Spring at the Roswell Country Club
and the other at the type locality (Unit 7 spring ditch) on BLNWR (Figures 5 and 12). Taylor
(1987: 9) reported possible fossil Pecos assiminea from along the Pecos River near Grandfalls,
Texas, and the Río Monclova, Coahuila, México. Pecos assiminea occurs at Diamond Y Spring Preserve (Diamond Y Spring source pool,
Monsanto Spring, Euphrasia Spring, and John’s Pool) owned by The Nature Conservancy, in
Pecos County, Texas (Figure 6; NMDGF 2000: A3) and at East Sandia Spring in Reeves
County, Texas, on private lands under stewardship of The Nature Conservancy (Figure 7;
NMDGF 2000: A3). The species also persists at BLNWR. On BLNWR, Pecos assiminea is
currently found in the upper reaches of Bitter Creek near Dragonfly Spring, the lower end of
Bitter Creek, the lower reaches of the Sago Spring Complex near Sinkhole No. 32 (and 31), in
the Unit 7 spring ditch, in the Snail Unit, and at a spring in the extreme southwestern corner of
Unit 15 (Figures 8 12, and 12a; Lang 2002: A5; Roesler 2016: 58). The species was not found at
North Spring on the Roswell Country Club during a survey in August 2004 (Figure 5; NMDGF
2005: 1). Pecos assiminea was found (single recent empty shell) in Hunter Marsh in 2009, but
subsequent intensive sampling in 2010 did not further identify any individuals (Figure 10;
NMDGF 2010: 9).

Import/Export

This species and its parts are not available to import or export.

Launch Interactive Map

Timeline

Explore the information available for this taxon's timeline. You can select an event on the timeline to view more information, or cycle through the content available in the carousel below.

29 Items