(DRAFT) - Taxonomy
Species MUSSEL, CURTUS'
Species Id ESIS404021
Date 13 MAR 96
TAXONOMY
NAME - MUSSEL, CURTUS'
OTHER COMMON NAMES - MUSSEL, CURTUS';MUSSEL CURTUS; SHELL, CLUB, BLACK; SHELL, CLUB+, BLACK;CLUBSHELL and BLACK
ELEMENT CODE -
CATEGORY - Aquatic Molluscs
PHYLUM AND SUBPHYLUM - MOLLUSCA,
CLASS AND SUBCLASS - BIVALVIA,
ORDER AND SUBORDER - UNIONOIDA,
FAMILY AND SUBFAMILY - UNIONIDAE,
GENUS AND SUBGENUS - PLEUROBEMA,
SPECIES AND SSP - CURTUM,
SCIENTIFIC NAME - PLEUROBEMA CURTUM
AUTHORITY -
TAXONOMY REFERENCES -
COMMENTS ON TAXONOMY -
Curtus' Mussel
Pleurobema curtum (I. Lea, 1859)
KINGDOM: Animal GROUP: Clam
PHYLUM: Mollusca CLASS: Bivalvia
ORDER: Unionoida FAMILY: Unionidae
Curtus' mussel is a bivalve mollusk about 55 mm long, 35 mm high,
and 30 mm wide. The shell varies from green in young shells to a dark
greenish-brown in older adults. The shell is sub-triangular, inflated
in front and has a bluish-white, iridescent, thin nacre (01).
The following name combinations are recognized as being
equivalent to P. curtum (Lea, 1859):
Unio curtus Lea, -- Lea 1859:113.
Margaron (Unio) curtus (Lea) -- Lea, 1870:40.
Pleurobema curta (Lea) -- Simpson, 1900:754.
Pleurobema curtum (Lea) -- Simpson, 1914:762.
Obovaria (Pseudoon) curta (Lea) -- Frierson, 1927:91.
The species maybe referred to as the Curtus mussel or the black
Taxonomy - 1 (DRAFT) - Taxonomy
Species MUSSEL, CURTUS'
Species Id ESIS404021
Date 13 MAR 96
club shell, also spelled black clubshell (08).
The figured holotype is at the United States National Museum
(01). The type locality is the Tombigbee River, Columbus, Lowndes
Co., MS.
Taxonomy - 2 (DRAFT) - Status
Species MUSSEL, CURTUS'
Species Id ESIS404021
Date 13 MAR 96
STATUS
Coded Status
Alabama; Federal Endangered
Alabama; Unofficially Listed
Mississippi; Federal Endangered
Mississippi; State Recognized
E: Federal Endangered
Commercial
COMMENTS ON STATUS -
U.S. STATUSES AND LAWS:
The Curtus' mussel (Pleurobema curtum) has been designated an
Endangered species pursuant to the Endangered Species Act of 1973
(50 CFR 17.11; P.L. 93-205, 87 Stat. 884; 16 U.S.C. 1531-1540), as
amended. The species has this status wherever found including the
States of AL and MS. Critical Habitat has not been designated.
This species is protected by the Lacey Act (P.L. 97-79, as
amended; 16 U.S.C. 3371 et seq.) which makes it unlawful to import,
export, transport, sell, receive, acquire, or purchase any wild animal
(alive or dead including parts, products, eggs, or offspring):
(1) in interstate or foreign commerce if taken, possessed,
transported or sold in violation of any State law or
regulation, or foreign law; or
(2) if taken or possessed in violation of any U.S. law,
treaty, or regulation or in violation of Indian tribal law.
It is also unlawful to possess any wild animal (alive or dead
including parts, products, eggs, and offspring) within the U.S.
territorial or special maritime jurisdiction (as defined in
18 U.S.C. 7) that is taken, possessed, transported, or sold in
violation of any State law or regulation, foreign law, or Indian
tribal law.
RESPONSIBLE FEDERAL AGENCIES:
USFWS -Responsible for the management/recovery, listing, and
law enforcement/protection of this species.
All Federal agencies have responsibility to ensure that any
action authorized, funded, or carried out by that agency is not likely
to jeopardize the continued existence of the species or result in the
destruction or adverse modification of Critical Habitat (50 CFR 402),
and to utilize their authorities to carry out programs for the
conservation of the species.
STATE STATUSES AND LAWS:
STATE: Alabama
UNOFFICIAL LIST: Endangered, Bulletin No.2, "Endangered and
Threatened Plants and Animals of Alabama",
Status - 1 (DRAFT) - Status
Species MUSSEL, CURTUS'
Species Id ESIS404021
Date 13 MAR 96
Alabama Museum of Natural History.
STATE: Mississippi
DESIGNATED STATUS: Recognized Endangered
ADMINISTRATIVE AGENCY: Department of Wildlife Conservation
STATE STATUTES: Public Notice No. 2156, Eff. Sept. 1, 1981.
INTERNATIONAL STATUSES, TREATIES, AND AGREEMENTS:
Pleurobema curtum is listed as endangered in the 1986 IUCN Red
List of Threatened Animals.
ECONOMIC STATUSES:
The stirrup shell may have some value in the cultured pearl
industry. The species is valued by collectors for scientific
purposes.
79/05/01:44 FR 25589/ - Notice of review
80/04/11:45 FR 24904/24905 - Notice of review
84/05/22:49 FR 21664/21675 - Notice of review
86/04/07:51 FR 11761/11768 - Proposed rule
86/06/18:51 FR 22092/ - Notice of public hearing
87/04/07:52 FR 11162/11169 - Final rule, listed as Endangered
Status - 2 HABITAT ASSOCIATIONS
HABITAT - AQUATIC
INLAND AQUATIC
LAND USE -
Streams and Canals
NATIONAL WETLAND INVENTORY CODES
NWI NWICLS NWIMOD NWISPEC
Riverine, upper perennial SB2
Riverine, upper perennial SB1
COMMENTS ON HABITAT ASSOCIATIONS -
The Curtus' mussel is found associated with a riffle-runs
habitat. Williams (05) found it in the main channel in gravel or
sandy-gravel in moderate to swift current. It does better in stable
substrates in strong current (01). It has been taken in water ranging
from 0.3 m to 1.3 m in depth (05). Specific environmental parameters
required by the species are unknown.
Much of the historic habitat has been modified by reservoir and
barge canal construction. The remaining population is in the East
Tombigbee River that was bypassed by the Tennessee-Tombigbee Waterway.
They are away from and not affected by operation of the completed
Waterway.
Habitat Associations - 1 (DRAFT) - Food Habits
Species MUSSEL, CURTUS'
Species Id ESIS404021
Date 13 MAR 96
FOOD HABITS
TROPHIC LEVEL -
OMNIVORE
LIFESTAGE FOOD FOOD PART
General Detritus
General Bacteria
General Phytoplankton
General Diatoms
General Zooplankton
General Fish
Food Habits - 1 (DRAFT) - Environment Associations
Species MUSSEL, CURTUS'
Species Id ESIS404021
Date 13 MAR 96
ENVIRONMENTAL ASSOCIATIONS
G = General A = Adult
LIM = Limiting RA = Resting Adult
J = Juvenile FA = Feeding Adult
RJ = Resting Juvenile BA = Breeding Adult
FJ = Feeding Juvenile P = Pupae
L = Larvae E = Egg
RL = Resting Larvae
FL = Feeding Larvae
LIFESTAGE ENVIRONMENTAL ASSOCIATIONS
G Aquatic Features: Pool areas
Environment Associations - 1 (DRAFT) - Life History
Species MUSSEL, CURTUS'
Species Id ESIS404021
Date 13 MAR 96
LIFE HISTORY
FOOD HABITS:
Glochidia are probably obligate parasites on the tissues of the
gills or fins of fish. Adult Curtus' mussels (Pleurobema curtum) are
filter-feeders and consume particulate matter suspended in the water
column (02). Identifiable stomach contents almost invariably include
detritus, bacteria, phytoplankton, diatoms, and zooplankton (02). No
study of the food habits of adult P. curtum has been conducted;
specific required/preferred foods are therefore unknown.
HOME RANGE/TERRITORY:
Non-territorial. The species is sedentary during its adult life
and generally occurs in rivers with others of its kind.
PERIODICITY:
No known periodicity.
MIGRATION PATTERNS:
Non-migratory.
COVER/SHELTER REQUIREMENTS:
The Curtus' mussel requires flowing water, frequently a riffle,
over stable sand and gravel. Water velocity can vary greatly. The
sand and gravel substrate must remain free of any heavy sediment (01).
REPRODUCTIVE SITE REQUIREMENTS:
Since P. curtum is a sedentary species reproductive site
requirements are the same as habitat requirements in general (See also
Cover/Shelter Requirements, above). Water velocity can vary greatly.
The sand and gravel substrate must remain free of any heavy sediment
(01).
REPRODUCTIVE CHARACTERISTICS:
Sperm are discharged into the surrounding water and dispersed by
water currents. Females downstream from the males obtain sperm during
the normal process of siphoning water while feeding and during
respiration. Fertilization occurs within the gills of the female,
which serve as marsupia for embryos developing to the parasitic stage
(glochidia) and are then released (02). The specifics of reproductive
characteristics for this species are unknown.
PARENTAL CARE:
No parental care occurs.
POPULATION BIOLOGY:
The population biology of this species is unknown.
SPECIES INTERRELATIONSHIPS:
The required fish hosts for the parasitic glochidia of Pleurobema
curtum are unknown.
OTHER LIFE HISTORY DESCRIPTORS:
Life History - 1 (DRAFT) - Life History
Species MUSSEL, CURTUS'
Species Id ESIS404021
Date 13 MAR 96
None.
Life History - 2 (DRAFT) - Management Practices
Species MUSSEL, CURTUS'
Species Id ESIS404021
Date 13 MAR 96
MANAGEMENT PRACTICES
RESULT MANAGEMENT PRACTICE
Beneficial Maintaining/Controlling Water Flow
Beneficial Land Acquisition
Beneficial Creating Artificial Habitat/Nesting Structure
Adverse Harassment/Vandalism/Indiscriminate Killing
Existing Harassment/Vandalism/Indiscriminate Killing
Adverse Siltation
Existing Siltation
Adverse Water Level Fluctuation
Existing Water Level Fluctuation
Adverse Reservoirs
Existing Reservoirs
Adverse Dredging
Existing Dredging
Adverse Applying fertilizers
Existing Applying fertilizers
Adverse Applying herbicides
Existing Applying herbicides
Adverse Applying pesticides
Existing Applying pesticides
COMMENTS ON MANAGEMENT PRACTICES -
The decline of Curtus' mussel to only one remaining population is
directly related to construction of the Tennessee-Tombigbee Waterway
(TTW). This species occurs in the East Fork Tombigbee River in a
reach near the confluence with Bull Mountain Creek. The only other
known site was a reach of the Tombigbee River in Pickens County, AL.
This area was so altered by the TTW that Curtus' mussel was extirpated
from this reach. The one reference to this species occurring in the
Big Black River, MS is an apparent labeling error (01).
The situation of the remaining Curtus' mussels away from the
navigation channel of the TTW allowed them to escape the full force of
the threats that extirpated it elsewhere in the Tombigbee River.
The Curtus' mussel has greatly declined in range and/or numbers
in the Tombigbee River owing to alteration of its habitat from a
free-flowing riverine system to an impounded system by the
construction of the Tennessee-Tombigbee Waterway. The modification of
the free-flowing Tombigbee River into a series of impoundments
adversely impacted the Curtus' mussel by physical destruction during
dredging, increasing siltation, reducing water flow, and suffocating
juveniles with sediment (03,04,05,01).
Although not considered a primary reason for listing Curtus'
mussel, the species is exposed to a continuing threat from runoff of
fertilizers and pesticides. Runoff of fertilizers into small streams
can exceed the assimilation ability of the stream and result in algal
blooms and excesses of other aquatic vegetation. This condition can
produce stream eutrophication and result in the death of native fauna.
Herbicides, insecticides, fungicides, and other pesticides are easily
washed from fields into streams, along with silt particles to which
Management Practices - 1 (DRAFT) - Management Practices
Species MUSSEL, CURTUS'
Species Id ESIS404021
Date 13 MAR 96
these substances adhere. While being transported downstream, these
particles may be ingested by filter feeders, such as this mussel. The
siphoning period and metabolic rate of mussels can be affected by such
contaminants as heavy metals and agricultural chemicals (07).
Pesticide laden silt particles eventually settle to and become part
of the substrate, thus increasing the pesticides in the clam's
habitat.
The Curtus' mussel may be adversely affected by the loss of its
fish host. No fish host has been identified yet, but the hosts of
clams from riffle habitats tend to be riffle-dwelling species (06) and
are likely to decline or become extirpated as this habitat is
modified.
Curtus' mussel continues to be threatened by flood control
projects and a low population level (02).
UNAPPROVED PLAN:
No recovery plan is yet developed for Curtus' mussel. Recovery
planning should be initiated in FY 1988.
Recovery actions that are anticipated for Curtus' mussel include:
Maintaining water flow; creating artificial habitat (e.g., gravel
bars); prohibiting sand and gravel dredging; and land easement
protection for remaining habitat.
At present, dredging is being prohibited and water flow is being
maintained.
Management Practices - 2 (DRAFT) - References
Species MUSSEL, CURTUS'
Species Id ESIS404021
Date 13 MAR 96
References
***** REFERENCES FOR ALL NARRATIVES EXCEPT N-OCCURRENCE *****
01 Stansbery, D.H. 1983. The status of Pleurobema curtum (Lea, 1859)
(Mollusca:Bivalvia:Unionoida). Unpubl. rep. on file at: USFWS,
Jackson Field Office, Jackson, MS. 10 pp + 2 pp museum records.
02 U.S. Fish and Wildlife Service. 1984. Recovery Plan for the Rough
Pigtoe Pearly Mussel [Pleurobema plenum (Lea, 1840)]. U.S. Fish
and Wildlife Service, Atlanta, GA. 51 pp.
03 Stansbery, D.H. 1980. Comments on naiad mollusks being reviewed
for possible addition to the Federal list of endangered and
threatened wildlife and plants. Unpubl. Rep. on file at: Jackson
Field Office, Jackson, MS. 23 pp.
04 Stein, C.B. 1971. Naiad life cycles: Their significance in the
conservation of fauna. Pages 19-25. IN: Proceedings of a
symposium on rare and endangered mollusks (naiads) of the U.S
Department of Interior, Fish and Wildlife Service. On file at:
Jackson Field Office, Jackson, MS. 79 pp.
05 Williams, J.D. 1982. Distribution and habitat observations of
selected Mobile basin unionid mollusks. Pages 61-85. IN: Report
of freshwater mollusks workshop, 19-20 May 1981. A.C. Miller, ed.
U.S. Army Eng. Waterway Exper. Sta. Environ. Lab., Vicksburg, MS.
184 pp.
06 Fuller, S.L.H. 1974. Clams and mussels (Mollusca:Bivalvia).
Pages 215-273. IN: Pollution ecology of freshwater invertebrates.
C.W. Hart and S.L.H. Fuller, eds. Academic Press, NY.
07 Salanki, J. 1979. Behavioural studies in mussels under changing
environmental conditions. Symp. Biol. Hung. 19:169-176.
08 Turgeon, D.D., A.E. Bogan, E.V. Coan, W.K. Emerson, et al. 1986.
Mollusks; A list of common and scientific names of aquatic
invertebrates from the United States and Canada. Am. Fish. Soc.
Special Publ., Bethesda, MD. 156 pp.
***** REFERENCES FOR N-OCCURRENCE NARRATIVE ONLY *****
01 Stansbery, D.H. 1981. The status of Pleurobema curtum (Lea, 1859)
(Mollusca:Bivalvia:Unionoida). Unpublished rep. on file at:
USFWS, Jackson Field Office, Jackson, MS. 10 pp + 2 pp museum
records.
References - 1