Occurrence of Microtralia ovula and Creedonia succinea (Gastropoda: Pulmonata: Ellobiidae) in South Carolina
D. Blake Sasse, Richard L. Clawson, Michael J. Harvey, and Steve L. Hensley
Southeastern Naturalist, Volume 6, Number 1 (2007): 173–178
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2007 SOUTHEASTERN NATURALIST 6(1):173–178
Occurrence of Microtralia ovula and Creedonia succinea
(Gastropoda: Pulmonata: Ellobiidae) in South Carolina
Julian R. Harrison1,* and David M. Knott2
Abstract - Gastropods in the family Ellobiidae are a cryptic and easily overlooked
component of intertidal habitats in South Carolina salt marshes. Recent and
archived collections reveal the presence of two ellobiid species, Microtralia ovula
and Creedonia succinea, which are established and occasionally abundant in the
mid- to upper-intertidal zone on oyster reefs and under wrack on washed shell
banks. These species are previously known to occur only in Bermuda, southern
Florida, the Bahamas, the Greater Antilles, and Mexico. This note reports a significant
northward extension of their known range and acknowledges that similar
distributional shifts are being more widely recognized for estuarine benthic fauna
along the US Atlantic coast.
Observations and Discussion
The faunal diversity and distribution of ellobiid snails in estuarine environments
of coastal South Carolina are poorly known. This undoubtedly
reflects, in part, a lack of collecting effort in estuarine marshes in the area,
rather than the low level of diversity sometimes assumed to prevail in this
part of the Carolinian province (Morrison 1951a). This note reports the
occurrence in South Carolina of two species of ellobiids previously documented
only from Bermuda, southern Florida, the Bahamas, the Greater
Antilles, and Mexico. Representative specimens of both species have been
deposited into the collections of the Southeastern Regional Taxonomic
Center in Charleston, SC (Creedonia: SERTC # S2192, S2193, S2194,
S2195, S2196, S2307, S2308, and S2309; Microtralia: SERTC # S2306) and
of the National Museum of Natural History in Washington, DC (Creedonia:
NMNH # 1083053; Microtralia: NMNH # 1083054). The following abbreviations
have also been used in this note: MCZ is the Museum of Comparative
Zoology, Harvard University, Cambridge, MA; USNM is the former
designation used for material in the United States National Museum, now
known as the NMNH.
At least three species of ellobiids are previously known or presumed
to occur within the state of South Carolina: Melampus (Melampus)
bidentatus Say; Melampus (Detracia) floridanus Pfeiffer; and Myosotella
myosotis (Draparnaud) (Abbott 1947, Martins 1996, Mazÿck 1913 [as
1Grice Marine Laboratory, College of Charleston, 205 Fort Johnson, Charleston, SC
29412. 2Southeastern Regional Taxonomic Center (SERTC), Marine Resources Research
Institute, South Carolina Department of Natural Resources, PO Box 12559,
Charleston, SC 29422-2559. *Corresponding author - email@example.com.
174 Southeastern Naturalist Vol. 6, No. 1
Melampus lineatus], Shoemaker et al. 1978). Mazÿck (1913) collected
one specimen of M. myosotis (listed by him as Alexia mysotis [sic]) from
Sullivans Island, SC, and there are three additional lots of this species
from the city of Charleston in the Mazÿck shell collection at the Charleston
Museum. Martins (1996) also recorded occurrences of M. myosotis
from Charleston (MCZ, uncatalogued) and McClellanville (USNM
663059). To date, however, no additional specimens of this species have
been found within the state. Two additional species, Melampus obliquus
Say and Blauneria heteroclita (Montagu), reported from South Carolina
by Mazÿck (1913), were based upon literature records; the former was
described by Say (1822) from specimens collected in South Carolina.
Melampus obliquus is now considered a junior synonym of M. bidentatus
(Martins 1996). The collection locality in Mazÿck’s (1913) report of B.
heteroclita was uncertain, and Martins (1996) considered that uncertainty
and the lack of further confirmation to warrant exclusion of South Carolina
from the range he reported for that species.
Microtralia ovula (Pfeiffer) was first observed in South Carolina in
1976 at Leadenwah Point and nearby in the North Edisto River, Charleston
County (32º36.5'N, 80º13.8'W). Between 1976 and 1978, 117 specimens
(seven of which were alive) were collected by one of us (J.R. Harrison)
from beneath oyster shells, driftwood, and Spartina wrack on shell banks
adjacent to intertidal S. alterniflora Loisel salt marsh. Specimens averaged
2.2 mm in length (range of 1.02–2.89), 1.2 mm in diameter (range of 0.72–
1.67), and 6.5 whorls (range of 5–7) (Fig. 1). Mollusks most frequently
found with M. ovula were Assiminea succinea (Pfeiffer) and juvenile or
subadult Melampus bidentatus. Microtralia ovula is otherwise known in
the United States only from Clearwater, FL, south to the Florida Keys
(Martins 1996). However, there is an unpublished report of this species
from northeast Florida, specific locality not given (Lee 2005). Outside of
the US, it is known to occur in Bermuda, the Bahamas, Cuba, Jamaica, and
Hispaniola (Morrison 1951b). Prior to the nomenclatural review of Faber
(2004), many authors referred to the species by its invalid junior synonym
Five specimens of Creedonia (= Marinula) succinea (Pfeiffer, 1854)
were also found at Leadenwah Point in July 1977, although none were alive.
These specimens averaged 2.2 mm in total length and 1.4 mm in diameter; of
these, three had four whorls and two had five whorls. The most northerly
record of this species previously reported is that of a specimen (USNM
#663054) collected by Leslie Hubricht at the Isle of Hope, Chatham County,
GA, and it was known elsewhere in the US only from the Florida Keys
(Martins 1996). The Georgia record was discounted by Martins (1996), who
stated that it could be better explained as a consequence of waif distribution,
perhaps as a result of accidental transportation by currents, due to the great
distance from its “normal range.” Water from the Mississippi River dis2007
J.R. Harrison and D.M. Knott 175
charge plume was previously observed off Georgia (Atkinson and Wallace
1975), and Walker (1994) suggested that the simultaneous occurrence of
oceanic current anomalies and meteorological conditions may deliver water
from remote locations to the east coast of the United States more often than
has been previously recognized.
Although the source and pathway of the introduction and subsequent
establishment of C. succinea in South Carolina is unknown, one of us
(D.M. Knott) recently documented the occurrence of persistent reproducing
populations of that species near Charleston, SC. A large number of
individuals were obtained from 430 mid-intertidal samples taken on 24
occasions between March 1995 and January 1998 at two sites near
Charleston Harbor: a) 2063 individuals from natural oyster clusters, shell
trays, and associated sediments at Toler’s Cove, off the Intracoastal Waterway
behind Sullivan’s Island (32º46.6'N, 79º50.8'W), and b) 2841 individuals
from similar substrates on oyster flats near the head of Inlet
Creek, landward of Sullivan’s Island and Isle of Palms (32º47.9'N,
79º49.7'W). The abundance of C. succinea appeared to be greater during
the fall and winter than during the rest of the year, and it was among the
Figure 1. Left: Microtralia ovula shown in ventral aspect. Scale bar = 1mm. Right:
Microtralia ovula shown in dorsal aspect. Scale bar = 1mm.
176 Southeastern Naturalist Vol. 6, No. 1
dominant resident macroinvertebrates in the 430 samples, ranking 6th out
of more than 80 species. The mollusks most commonly occurring in
samples with high numbers of C. succinea were the bivalves Geukensia
demissa (Dillwyn, 1817) and Sphenia antillensis (Dall and Simpson,
1901). Eighteen of these live-collected specimens of C. succinea, selected
at random, averaged 2.5 mm (2.1–2.8) in length, 1.4 mm (1.0–1.5) in
diameter, and all except one had four whorls (Fig. 3).
The new records of Creedonia succinea and Microtralia ovula presented
here provide evidence that the two species are now established in South
Carolina waters. Further collecting within their newly extended range
should reveal their occurrence in additional localities. Similar northward
expansion of the ranges of the anomuran decapod Petrolisthes armatus
(Gibbes, 1850) and the amphipod Caprella scaura Templeton, both from
south Florida and northwestern Atlantic tropical waters into South Carolina,
have recently been documented (Foster et al. 2004, Knott et al. 2000). These
observations conform to the speculation of Engle and Summers (1999) that
distributional shifts of estuarine benthic fauna are likely to occur along the
Atlantic coast, given current climate-change scenarios that predict increased
Figure 2. Left: Creedonia succinea shown in ventral aspect. Scale bar = 1mm. Right:
Creedonia succinea shown in dorsal aspect. Scale bar = 1mm.
2007 J.R. Harrison and D.M. Knott 177
global temperatures of up to 2 °C. It is also likely that the ranges of some
species will be extended into South Carolina simply as a result of increased
scrutiny of the biodiversity of that region.
We would like to thank Loren Coen and the staff of the Oyster Reef Program
at the Marine Resources Research Institute. We also especially thank Drs.
António M. De Frias Martins and Robert T. Dillon for their helpful comments on
the manuscript. Research by J.R. Harrison in the North Edisto River salt marsh
system was supported by a grant (R-804-688-01) from EPA to the Grice Marine
Laboratory. This is Contribution No. 298 of the Grice Marine Laboratory and
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