Overview

Distribution

National Distribution

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

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Global Range: (100-1000 square km (about 40-400 square miles)) Once thought to have the most restricted distribution of any fairy shrimp (Eng et al., 1990), but now found to be more widespread (USFWS, 2000). The five original pools from which it was collected are all in western Riverside County in an area about 13 by 7 km, between elevations of 348 and 413 m, near Temecula and Rancho California. (Eng et al. 1990). Subsequent localities have been found in Los Angeles, Orange, San Diego, and Ventura Counties, California. In total range extends from coastal southern California south to northwestern Baja California, Mexico (USFWS, 2000; Eriksen and Belk, 1999).

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Historic Range:
U.S.A. (CA)

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Physical Description

Size

Length: 2.3 cm

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Diagnostic Description

Streptocephalus seali is the described species most similar to Streptocephalus woottoni. The cercopods of mature male S. wootoni are edged with plumose setae, while on S. seali, spines replace the setae on the distal half of the cercopods. In addition, S. seali and S. similis have confluent inner margins of the cercopods, which S. wootoni lacks. In preserved females, no species-distinguishing characteristics are observable; however, in living S. wootoni, both male and female have the red color of the cercopods covering the ninth and part of the eighth abdominal segments. In living S. seali, no red extends onto the abdominal segments of either sex. (Eng et al., 1990; FWS, 2000)

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Type Information

Paratype for Streptocephalus woottoni Eng et al., 1990
Catalog Number: USNM 1156069
Collection: Smithsonian Institution, National Museum of Natural History, Department of Invertebrate Zoology
Preparation: Alcohol (Ethanol)
Collector(s): C. Eriksen
Year Collected: 1985
Locality: Hot Springs Country Club at edge of golf course near Highway 79, ca. 4 mi east of Murietta, Riverside County, California, United States
  • Paratype:
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Paratype for Streptocephalus woottoni Eng et al., 1990
Catalog Number: USNM 1156068
Collection: Smithsonian Institution, National Museum of Natural History, Department of Invertebrate Zoology
Preparation: Alcohol (Ethanol)
Collector(s): C. Eriksen
Year Collected: 1986
Locality: natural slump west side of Pala Road near Pechanga Indian Reservation, Riverside County, California, United States
  • Paratype:
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Holotype for Streptocephalus woottoni Eng et al., 1990
Catalog Number: USNM 234417
Collection: Smithsonian Institution, National Museum of Natural History, Department of Invertebrate Zoology
Preparation: Alcohol (Ethanol)
Collector(s): C. Eriksen
Year Collected: 1986
Locality: Hot Springs Country Club Golf Course, Near Cal. 79, 4 Mile E Of Murietta;, Riverside County, California, United States
  • Holotype:
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Paratype for Streptocephalus woottoni Eng et al., 1990
Catalog Number: USNM 234418
Collection: Smithsonian Institution, National Museum of Natural History, Department of Invertebrate Zoology
Preparation: Alcohol (Ethanol)
Collector(s): C. Eriksen
Year Collected: 1986
Locality: Hot Springs Country Club Golf Course, Near Cal. 79, 4 Mile E Of Murietta;, Riverside County, California, United States
  • Paratype:
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Ecology

Habitat

Habitat and Ecology

Systems
  • Freshwater
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Habitat Type: Freshwater

Comments: The 5 original sites in Riverside County are vernal pools, seasonally astatic (dry up and refill one or more times during the year), and occur in earth slump basins or tectonic swales, in patches of grassland and agriculture interspersed in coastal sage scrub vegetation. Minimum habitat size was 750 square meters, with a minimum depth of 30 cm at maximum filling. Total Dissolved Solids, alkalinity, and chloride were very low, conditions corroborated by pH at neutral or just below. This species did not appear until later in the season, so it can be considered a warm water species. (Eng et al., 1990). The species is generally found in vernal pool complexes, which average 5 to 50 pools although some contain as few as 2 and a few contain several hundred; that are generally hydrologically connected; and it is also found at one man-made complex at Johnson Ranch (USFWS, 2008)

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Migration

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

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Trophic Strategy

Comments: In general, Anostracans are free-swimming filter feeders, feeding primarily on bacteria, algae, rotifers, Protozoa, and bits of detritus (Pennak, 1989; FWS, 2000). No specific studies have been done on the feeding habits of Streptocephalus woottoni.

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Population Biology

Number of Occurrences

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 6 - 80

Comments: When inititally listed it was known from 9 vernal pool complexes in Orange, Riverside, and San Diego Counties, California, and northwest Baja California, Mexico (FWS, 2000). Subsequently, it has been found in as many as 52 additional complexes with 9 of these known to have been extirpated and status unknown at 3 others. More than half of these are in San Diego Co. with another 24% in Riverside Co. and 17% in Orange Co., plus single occurrences in Ventura and Los Angeles Cos.; status of the two occurrences in Mexico is unknown at this time (USFWS, 2008).

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Global Abundance

Unknown

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General Ecology

Occurs in seasonal pools that are filled by winter and spring rains that usually begin in November and continue into April or May. There was minimal perennial vegetation immediately surrounding these pools, but two contained emergent Eleocharis. One pool contained a good deal of dead, but rooted, woody portions of terrestrial vegetation which apparently grew in the basin when it was dry. The more open pools had turbid water, while deeper or partially vegetated pools were clear. In three of the five collection sites, Streptocephalus woottoni and Branchinecta lindahli occurred together. S. woottoni was always taken in deeper water among loose emergent vegetation. (Eng et al., 1990; FWS, 2000)

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Life History and Behavior

Cyclicity

Comments: Like other Anostracans, S. WOOTTONI has a seasonal cycle that varies with the water level and temperature of the pools in which it lives. Most Anostracans bear eggs that overwinter in the dried-out mud of the pool and hatch in early spring. The rapidly maturing animals produce eggs in the autumn that fall to the bottom of the pool and do not hatch until the following spring (Pennak, 1990).

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Reproduction

The biology of this new species has not been studied. However, it seems to appear later in the season. Early February collections from the type locality did not contain any Streptocephalus woottoni, mid-March collections contained immature individuals, and late March collections contained mature specimens. (Eng et al., 1990). Hatching of cysts observed in January to March; however, in years with early or late rainfall, the hatching period may be extended. The species hatches within 7 to 21 days after the pool refills, depending on water temperature, and matures between 48 to 56 days, depending on a variety of habitat conditions. "Resting" or summer cysts are capable of withstanding temperature extremes and prolonged drying. When the pools refill in the same or subsequent rainy seasons, some but not all of the eggs may hatch. Reproductive success is spread over several seasons (FWS, 2003).

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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
EN
Endangered

Red List Criteria
A2c

Version
2.3

Year Assessed
1996
  • Needs updating

Assessor/s
Inland Water Crustacean Specialist Group

Reviewer/s

Contributor/s
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National NatureServe Conservation Status

United States

Rounded National Status Rank: N1 - Critically Imperiled

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NatureServe Conservation Status

Rounded Global Status Rank: G1 - Critically Imperiled

Reasons: Limited to the southern California coastal mesa system, an area with significant pressure from urban and industrial development. Vast areas of habitat have been eliminated by conversion.

Intrinsic Vulnerability: Highly vulnerable

Comments: A recent mitochondrial DNA study sampled 316 San Diego fairy shrimp (a related species) from 24 vernal pool complexes (Bohonak, 2005); and two distinct genetic clades were identified that are surprisingly not geographically separate; the two clades are somewhat intermixed geographically. Bohonak (2005) found that gene flow between pool complexes is lower in areas that have less disturbance from urbanization and human activitiesand postulated that human activities tend to homogenize the genetic composition of natural populations of the species by translocating cysts between pool complexes. It is not known what effect this suspected human-related homogenization may have on the long-term viability of this fairy shrimp. More genetic research is necessary.

Environmental Specificity: Very narrow. Specialist or community with key requirements scarce.

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Current Listing Status Summary

Status: Endangered
Date Listed: 08/03/1993
Lead Region:   California/Nevada Region (Region 8) 
Where Listed: Entire


Population detail:

Population location: Entire
Listing status: E

For most current information and documents related to the conservation status and management of Streptocephalus woottoni , see its USFWS Species Profile

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Global Short Term Trend: Decline of 10-30%

Comments: Vast areas of habitat have been eliminated by conversion to residential areas. The type locality (Murrietta Golf Course) was lost to development prior to the listing of the species so it no longer occurs in Los Angeles Co. (USFWS, 2008). Although as many as 52 additional vernal pool complexes have been identified since the listing of the species (with 9 lost to development, 10 partially lost to development, 8 with pools impacted, and 3 with status unknown), these are not believed to be range expansions but occurrences missed in previous surveys (USFWS, 2008). Surveying occurrences for changes in numbers of individuals and demographic trends over time is not possible due to the small size and life history traits. Population trends are determined indirectly by assessing changes in the amount of habitat occupied by the species over time. Although there are more known occupied locations now then were known at the time of listing, with the exception of the one man-made complex at Johnson Ranch, the additional occupied pools were likely in existence (though undocumented) when the species was listed. Additionally, most losses due to development since the species was listed have been, or will be, offset via vernal pool preservation, restoration, and enhancement. Abundance, therefore, has not increased or decreased substantially since listing (USFWS, 2008).

Global Long Term Trend: Decline of 30-50%

Comments: At the time of listing in 1993, habitat in San Diego Co. had declined 97%, in Orange Co. 90-98%, with similar declines in Riverside and Ventura Cos., and to a lesser degree in Baja California, Mexico, and all pools lost in Los Angeles Co.

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Threats

Degree of Threat: High

Comments: From USFWS (2008):
Development is the greatest threat to the species across its range. The growth rate of the human population and associated urban and road development in southern California and northwestern Baja California is equal to or exceeds that of any other region in California and San Diego is one of the fastest growing counties in the nation (adjacent counties of Riverside and Orange are expected to grow very rapidly as well). Development of border security and associated infrastructure also threatens the species along the international border; which could have direct impacts to fairy shrimp habitat, i.e., destruction of vernal pools or their watersheds, and isolation of pools and fragmentation of pool systems; development can also cause alterations in the hydrology of adjacent pools. There are currently development proposals in place that would partially impact another 10 complexes (approximately) occupied by the fairy shrimp but it is expected that impacts will be minimized by imposing conservation measures along the way. Designation of critical habitat and vernal pool restoration have lessened development pressure. Fragmentation and isolation and associated impacts to hydrology continue to threaten the species throughout its range. Development within a vernal pool watershed can alter the timing, temperature, frequency, and length of inundation of nearby vernal pools; and persistence of this species is dependent on maintaining stable hydrology. Modifications to the uplands surrounding a vernal pool (e.g., grading cuts) can negatively affect the pool's hydrology by accelerating the flow of water into or out of the subsoil, even if such modifications occur outside the pool's surface watershed. Although initially considered a threat, destruction of pools by agriculture has largely been mitigated and is no longer considered a substantial threat. This is also the case for limited livestock grazing, which is also no longer considered the threat it once was. Human disturbance (trampling and vehicle traffic) is a minor threat in small portions of the range. Another threat is invasion by non-native plants including two nonnative wetland grasses: Agrostis avenacea (Pacific bentgrass) and Polypogon monspeliensis (annual rabbits foot grass). These invasives can overtake pools and decrease the number of days of inundation following rain events so pools no longer provide suitable fairy shrimp habitat. Threats of military activities originally identified in the recovery plan (USFWS, 1998) have largely been alleviated by better management practices and partnerships with military bases to better protect the species on military lands. Hybridization and competition with the versatile pool fairy shrimp, Branchinecta lindahli, is also a threat, but only in a few locations of disturbed pools where the species overlap. Herbicide and pesticide use is assumed to be a threat but overall impacts are not well known. Other pollution from runoff and rainwater may also threaten portions of the range. Dumped trash and other litter may decrease water quality as materials dissolve or decompose. Dumped material can also fill pools leaving little or no space for water to collect, or cover the bottom of pools, preventing larvae hatching from cysts from moving from the soil into the water column. Drought was noted in the listing rule as a stochastic (random or unpredictable) event that could have drastic affects on the species given its fragmented and restricted range. As such, climate change is now considered a potential threat. Climate change has the potential to adversely affect the fairy shrimp through changes in vernal pool inundation patterns and consistency. The exact effects are not known but are postulated, based on current climate change models, to be deleterious. Although fire was initially considered a substantial threat, the greater number of newly discovered populations helps alleviate the catastrophic effect fire would have on a single or few closely spaced occurrences. More information is needed on the impacts of fire on newly hatched fairy shrimp.

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Management

Global Protection: Unknown whether any occurrences are appropriately protected and managed

Comments: 8 ac (3 ha) of occupied habitat have been restored and approximately 42 ac (18 ha) (including most restored habitat) have been conserved to minimize habitat losses and impacts. Most vernal pool restoration projects to successfully support the species so far. Despite this and restoration efforts, 17 of the 45 known occupied complexes, or about 38 percent, occur on private lands that are not preserved and are thus vulnerable to future development. Currently, approximately 42 ac (17 ha) of occupied habitat has been conserved to offset losses and impacts. Conservation of these lands captures, in part, approximately 36 percent (16) of known occupied complexes. An additional 27 percent of known occupied complexes occur on approximately 5 ac (2 ha) of military land where they are generally provided some protection (USFWS, 2008).

Needs: Critical habitat proposed designation in 4880 hectare area in Los Angeles, Orange, Riverside, San Diego, and Ventura Counties, California (FWS, 2000).

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Relevance to Humans and Ecosystems

Benefits

Economic Uses

Comments: No known commercial use.

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Wikipedia

Streptocephalus woottoni

Streptocephalus woottoni, with the common name Riverside fairy shrimp, is a rare species of crustacean in the family Streptocephalidae. It is native to Southern California in the United States, and northern Baja California in Northeast Mexico.

Description[edit]

This fairy shrimp, Streptocephalus woottoni, lives in vernal pools or other seasonal pools at least 30 centimeters in depth, and can be observed in January through March. It feeds on microscopic organisms such as bacteria and protozoa. The eggs are cysts that can tolerate drying and persist in the soil through the dry seasons until pools are formed by rainwater. The shrimp then hatches and completes its life cycle in 7 or 8 weeks.[1]

Conservation[edit]

This organism can only be found in: five locations in southern California in Riverside County and San Diego County; and two in northern Baja California. Some known population occurrences have been extirpated, including the type locality in Murrieta, in the Peninsular Ranges foothills. The shrimp is threatened by the loss, degradation, and fragmentation of its habitat.[1]

Streptocephalus woottoni is a federally listed endangered species of the United States. In December 2012, the United States Fish and Wildlife Service identified 1,724 acres of critical habitat of the shrimp.[2]

See also[edit]

Wikimedia Commons has media related to Streptocephalus woottoni.

References[edit]



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