Invasion History

First Non-native North American Tidal Record: 1898
First Non-native West Coast Tidal Record: 1898
First Non-native East/Gulf Coast Tidal Record:

General Invasion History:

Crepidula convexa is native to the East Coast of North America from New England to Georgia. Records of C. convexa from Florida to Colombia and the Caribbean refer to a sibling species, C. ustulatulina, which differs at the molecular level and larval mode. Crepidula ustulatulina has lecithotrophic larvae, which settle soon after release (Collin 2002). The northern limits of the range are uncertain, but museum and literature records are scarce north of Cape Cod (Gould 1841; Academy of Natural Sciences of Philadelphia 2013). Gould (1870) lists records from Sable Island, Nova Scotia, which could have resulted from animals on seaweed or debris carried by the Gulf Stream. Verrill and Smith (1873) and the Malacolog.org database (Rosenberg 2013) list occurrences in the Gulf of St. Lawrence, but we have been unable to find the source for these. Bousfield (1960) does not list this species for Atlantic Canada. The Convex Slippersnail has been introduced to California (San Francisco Bay in 1898 and Humboldt Bay in 1998), Washington (Padilla Bay in 1970) and British Columbia (Boundary Bay in 1988) (Carlton 1979; McGlashan et al. 2008; Collin 2006).

North American Invasion History:

Invasion History on the West Coast:

Crepidula convexa was first collected in San Francisco Bay in 1898 from beds of planted Eastern Oysters (Crassostrea virginica) near Alameda (Carlton 1979). It occurs commonly on the shells of the native Ostrea lurida (Olympic Oyster) and the introduced Ilyanassa obsoleta (Eastern Mudsnail). Most records are from the South Bay, from Alameda to Redwood City (Carlton 1979; Cohen and Carlton 1995; California Academy of Sciences 2013), but there is a 1931 record from San Pablo Bay, and a 2002 record from Treasure Island, off San Francisco (California Academy of Sciences 2013).

Crepidula convexa has been discovered at several locations north of San Francisco Bay. In Humboldt Bay, California (CA) this snail was originally collected in 1989 and reported as C. fornicata (Carlton 1992), but dried specimens were identified as C. convexa using DNA sequencing (McGlashan et al. 2008). Boyd et al. (2002) reported Crepidula spp. as established in Humboldt Bay, and these are presumed to include C. convexa. Further north, C. convexa was found in Padilla Bay, Washington (WA), north of Puget Sound, in 1970 (Penttila 1971, cited by Collin et al. 2006), and in Boundary Bay, British Columbia in 1988. The identity of these animals was confirmed by molecular methods (Carlton 1992; Collin et al. 2006). The dates of introduction to these northern bays are unknown. The likeliest vector is with transplants of Eastern Oysters which took place from the 1870s to the 1930s (Collin et al. 2006).


Description

Crepidula convexa is a small, limpet-like marine snail, with a deeply convex oval shell. The shell has a strongly coiled, hook-like apex, and an interior shelf-like deck covering about 1/3 of the aperture, giving it a boat-like appearance. The deck is situated deep inside the shell and is slightly asymmetrical, extending forward on the left side (in ventral view). A muscle scar is located inside the shell on the right side. The edge of the deck is very slightly curved inward, almost straight. The thickness of the shell is highly variable, as is the color, from tan to dark or reddish brown. The overall shape of the animal is variable too, usually oval, but can be more elongate when growing on Eelgrass (Zostera) blades. This snail grows to about 20 mm in size. It grows attached to a solid surface, such as rock, wood, live or dead mollusk shells, or eelgrass. Description from: Hendler and Franz 1971, Abbott 1974, Morris 1975, Gosner 1978, Lippson and Lippson 1997.


Taxonomy

Taxonomic Tree

Kingdom:   Animalia
Phylum:   Mollusca
Class:   Gastropoda
Order:   Neotaenioglossa
Family:   Calyptraeidae
Genus:   Crepidula
Species:   convexa

Synonyms

Crepidula acuta (H. C. Lea, 1842)
Crepidula glauca (Say, 1822)
Crypta (Crypta) navicula (Morch, 1877)

Potentially Misidentified Species

Crepidula fornicata
Small juveniles of C. fornicata and C. convexa have been confused (McGlashan et al. 2008).

Crepidula ustulatulina
A new species described by Collin (2002), found from southern Florida through the Caribbean. It differs in molecular characters and mode of development, with lecithotrophic larvae.

Ecology

General:

Crepidula convexa, the Convex Slippersnail, is a small mobile, but sedentary, filter-feeding marine gastropod, with a limpet-like body. It lives attached to a solid substrates. It is a protandric hermaphrodite. It first matures as a male at 3-8 mm with a phallus and copulates with females. Then at 6-8 mm, it loses its phallus and converts to a female. Unlike C. fornicata, C. convexa does not form stacks of multiple individuals – a female carries only one male. Snails begin carrying embryos at about 10 mm length. Eggs are laid in masses of flask-shaped egg capsules, each containing multiple eggs, brooded on the substrate under the shell. The number of eggs in the capsule ranges from ~7-25, increasing with the size of the snail. The total number of eggs laid ranges from 100 to over 1,000 over the range of female shell size (11 to 21 mm). Eggs take about two weeks to hatch and development is direct, resulting in crawling juveniles ~ 1 mm long. Some eggs disintegrate and probably serve as food for the developing embryos. Individuals can mature first as males and then produce embryos as females in only one season. Maximum longevity is probably 1 1/2 years (Hendler and Franz 1971).

Crepidula convexa can grow on a variety of substrates, including rock, wood, eelgrass blades, shells of dead or live mollusks, or shells inhabited by hermit crabs. It is most common at salinities of 20-30 PSU and inhabits shallow estuaries with a wide temperature range (Wass 1972; Leathem and Maurer 1975). Common molluscan hosts include Crassostrea virginica (Eastern Oyster, East Coast), Ostrea lurida (Olympic Oyster), Ilyanassa obsoleta (Eastern Mudsnail), and Batillaria attramentaria (Japanese False Cerith) (Carlton 1979; Carlton 1992; Collin et al. 2006). In San Francisco Bay and Boundary Bay, C. convexa is found on shells inhabited by the hermit crabs Pagurus hirsutiusculus and P. granosimanus (Wohnam et al. 2005; McLean, in Carlton 2007). On the East Coast, C. convexa is commonly associated with eelgrass (Lippson and Lippson 1997), but does not seem to occur on these plants on the West Coast. Crepidula convexa, like others of its genus, is a filter feeder, trapping phytoplankton and detritus in strings of mucus on its gills, which are conveyed to its mouth (Lippson and Lippson 1997).

Food:

Phytoplankton, detritus

Trophic Status:

Suspension Feeder

SusFed

Habitats

General HabitatGrass BedNone
General HabitatOyster ReefNone
Salinity RangePolyhaline18-30 PSU
Salinity RangeEuhaline30-40 PSU
Tidal RangeSubtidalNone
Tidal RangeLow IntertidalNone
Vertical HabitatEpibenthicNone


Tolerances and Life History Parameters

Minimum Temperature (ºC)0Field- Delaware Bay (Hendler and Franz 1971)
Maximum Temperature (ºC)30Field- 'Near freezing', Delaware Bay (Hendler and Franz 1971)
Minimum Salinity (‰)15Field, rare below 20 (Leathem and Maurer 1975)
Maximum Salinity (‰)35Typical ocean salinity
Minimum Length (mm)3Minimum length for maturation as males. The snails first develop as males and then convert to femalesat 6-13 mm, and produce embryos at about 10 mm (Hendler and Franz 1971).
Maximum Length (mm)20Hendler and Franz 1971
Broad Temperature RangeNoneCold temperate-Warm temperate
Broad Salinity RangeNonePolyhaline-Euhaline

General Impacts

Ecological and economic impacts have not been reported for Crepidula convexa (Convex Slippersnail) in introduced locations. At high densities, this attached mollusk could affect the mobility of snails and hermit crabs, and could reduce growth, productivity, and habitat quality of Eelgrass (Zostera marina) if it begins to colonize the plant. As a filter-feeder, it has the potential to affect phytoplankton biomass. However, these impacts have not been seen on the West Coast.

Regional Distribution Map

Bioregion Region Name Year Invasion Status Population Status
NEP-VI Pt. Conception to Southern Baja California 2015 Non-native Established
P062 _CDA_P062 (Calleguas) 2015 Non-native Established
NEP-IV Puget Sound to Northern California 1989 Non-native Established
P130 Humboldt Bay 1989 Non-native Established
NEP-V Northern California to Mid Channel Islands 1898 Non-native Established
P090 San Francisco Bay 1898 Non-native Established

Occurrence Map

OCC_ID Author Year Date Locality Status Latitude Longitude
701295 Carlton 1979 1898 San Francisco Bay Non-native 37.8494 -122.3681
702159 Cohen et al. 2005 (SF Bay Area RAS) 2004 2004-05-24 San Leandro Marina, San Francisco Bay Non-native 37.6966 -122.1932
704286 Cohen et al. 2005 (SF Bay Area RAS) 2004 2004-05-23 Brisbane Lagoon, San Francisco Bay Non-native 37.6862 -122.3906
760242 H. Hemphill, in litt., in Stearns 1899b; Stearns 1900 1899 "Alameda flats" (off Oakland) Non-native 37.7521 -122.2643
760243 Packard 1918 1913 South San Francisco Bay Non-native 37.5457 -122.1645
760244 Dall 1921 1921 "Alameda flats" (off Oakland) Non-native 37.7521 -122.2643
760245 Filice 1958 1951 1951-10-08 off Hercules Wharf, San Pablo Bay Non-native 38.0281 -122.2983
760246 Filice 1958 1951 1951-11-23 off Davis Point, San Pablo Bay Non-native 38.0589 122.2806
760247 Wicksten 1978 1978 Coyote Point Non-native 37.5922 -122.3210
760248 Anatek Laboratories, Inc. and Kinnetic Laboratories, Inc. 1982, after Filice 1986 1980 1980-09-23 Offshore of Berkeley Aquatic Park Non-native 38.8575 -122.3056
775449 Ruiz et al., 2022 2015 2015-07-25 Naval Base floating dock, Port Hueneme, California, USA Non-native 34.1537 -119.2090
775450 Ruiz et al., 2022 2015 2015-07-25 Naval Base floating dock, Port Hueneme, California, USA Non-native 34.1537 -119.2090
775451 Ruiz et al., 2022 2015 2015-07-25 Naval Base floating dock, Port Hueneme, California, USA Non-native 34.1537 -119.2090
775452 Ruiz et al., 2022 2015 2015-07-25 Naval Base floating dock, Port Hueneme, California, USA Non-native 34.1537 -119.2090
775453 Ruiz et al., 2022 2015 2015-07-25 Naval Base floating dock, Port Hueneme, California, USA Non-native 34.1537 -119.2090
775454 Ruiz et al., 2022 2015 2015-07-25 Naval Base floating dock, Port Hueneme, California, USA Non-native 34.1537 -119.2090
775455 Ruiz et al., 2022 2015 2015-07-24 Naval Base alpha dock, Port Hueneme, California, USA Non-native 34.1528 -119.2102
775456 Ruiz et al., 2022 2015 2015-07-24 Naval Base alpha dock, Port Hueneme, California, USA Non-native 34.1528 -119.2102
775457 Ruiz et al., 2022 2015 2015-07-24 Naval Base alpha dock, Port Hueneme, California, USA Non-native 34.1528 -119.2102
775458 Ruiz et al., 2022 2015 2015-07-24 Naval Base alpha dock, Port Hueneme, California, USA Non-native 34.1528 -119.2102
775459 Ruiz et al., 2022 2015 2015-07-24 Naval Base alpha dock, Port Hueneme, California, USA Non-native 34.1528 -119.2102
775460 Ruiz et al., 2022 2015 2015-07-24 Naval Base sealion dock, Port Hueneme, California, USA Non-native 34.1466 -119.2126
775461 Ruiz et al., 2022 2015 2015-07-24 Naval Base sealion dock, Port Hueneme, California, USA Non-native 34.1466 -119.2126
775462 Ruiz et al., 2022 2015 2015-07-24 Naval Base sealion dock, Port Hueneme, California, USA Non-native 34.1466 -119.2126
775463 Ruiz et al., 2022 2015 2015-07-24 Naval Base sealion dock, Port Hueneme, California, USA Non-native 34.1466 -119.2126
775464 Ruiz et al., 2022 2015 2015-07-22 Port Hueneme site 1, Port Hueneme, California, USA Non-native 34.1473 -119.2092
775465 Ruiz et al., 2022 2015 2015-07-20 Port Hueneme Site 2, Port Hueneme, California, USA Non-native 34.1479 -119.2022
775466 Ruiz et al., 2022 2015 2015-07-20 Port Hueneme Site 2, Port Hueneme, California, USA Non-native 34.1479 -119.2022
775467 Ruiz et al., 2022 2015 2015-07-20 Port Hueneme Site 2, Port Hueneme, California, USA Non-native 34.1479 -119.2022
775468 Ruiz et al., 2022 2015 2015-07-20 Port Hueneme Site 2, Port Hueneme, California, USA Non-native 34.1479 -119.2022
775469 Ruiz et al., 2022 2015 2015-07-22 Port Hueneme Site 3, Port Hueneme, California, USA Non-native 34.1482 -119.2018
775470 Ruiz et al., 2022 2015 2015-07-22 Port Hueneme Site 3, Port Hueneme, California, USA Non-native 34.1482 -119.2018
775471 Ruiz et al., 2022 2015 2015-07-22 Port Hueneme Site 3, Port Hueneme, California, USA Non-native 34.1482 -119.2018
775472 Ruiz et al., 2022 2015 2015-07-22 Port Hueneme Site 3, Port Hueneme, California, USA Non-native 34.1482 -119.2018
775473 Ruiz et al., 2022 2015 2015-07-21 Port Hueneme Site 4, Port Hueneme, California, USA Non-native 34.1487 -119.2049
775474 Ruiz et al., 2022 2015 2015-07-21 Port Hueneme Site 4, Port Hueneme, California, USA Non-native 34.1487 -119.2049
775475 Ruiz et al., 2022 2015 2015-07-21 Port Hueneme Site 4, Port Hueneme, California, USA Non-native 34.1487 -119.2049
775476 Ruiz et al., 2022 2015 2015-07-21 Port Hueneme Site 4, Port Hueneme, California, USA Non-native 34.1487 -119.2049
775477 Ruiz et al., 2022 2015 2015-07-21 Port Hueneme Site 4, Port Hueneme, California, USA Non-native 34.1487 -119.2049
819012 Ruiz GM and JB Geller (2015) 2012 San Leandro None 37.6580 -122.2217
819013 Ruiz GM and JB Geller (2015) 2012 Redwood City None 37.5574 -122.1755
819014 Ruiz GM and JB Geller (2015) 2012 Coyote Point None 37.5987 -122.3252
819015 Ruiz GM and JB Geller (2015) 2012 None None
819016 Ruiz GM and JB Geller (2015) 2012 Corte Madera None 37.9309 -122.4819
819017 Ruiz GM and JB Geller (2015) 2012 Oyster Point None 37.6805 -122.3731
819018 Ruiz GM and JB Geller (2015) 2012 Richardson Bay None 37.8788 -122.4759
819019 Ruiz GM and JB Geller (2015) 2012 Emeryville None 37.8596 -122.3152
819020 Ruiz GM and JB Geller (2015) 2012 Ballena Isle None 37.7643 -122.2978
819510 Ruiz GM and JB Geller (2015) 2013 Marriott Marina None 32.7065 -117.1695
819511 Ruiz GM and JB Geller (2015) 2013 Cabrillo Isle None 32.7249 -117.2063
819512 Ruiz GM and JB Geller (2015) 2013 Imperial Beach None 32.6141 -117.1273
819513 Ruiz GM and JB Geller (2015) 2013 Point Loma None 32.6912 -117.2390
819514 Ruiz GM and JB Geller (2015) 2013 Chula Vista None 32.6407 -117.1251
819515 Ruiz GM and JB Geller (2015) 2013 National City None 32.6750 -117.1348
819516 Ruiz GM and JB Geller (2015) 2013 Fiddler's cove None 32.6483 -117.1402
819517 Ruiz GM and JB Geller (2015) 2013 None None
819518 Ruiz GM and JB Geller (2015) 2013 Coronado None 32.6843 -117.1606
819519 Ruiz GM and JB Geller (2015) 2013 Coronado Cays None 32.6339 -117.1332
819598 Ruiz GM and JB Geller (2015) 2013 Emeryville None 37.8602 -122.3000
819599 Ruiz GM and JB Geller (2015) 2013 Corte Madera None 37.9364 -122.4833
819600 Ruiz GM and JB Geller (2015) 2013 Richardson bay None 37.8737 -122.4667
819601 Ruiz GM and JB Geller (2015) 2013 None None
819602 Ruiz GM and JB Geller (2015) 2013 Ballena isle None 37.7578 -122.2500
819603 Ruiz GM and JB Geller (2015) 2013 Oyster Point None 37.6788 -122.3667
819604 Ruiz GM and JB Geller (2015) 2013 Redwood city None 37.5588 -122.2000
819605 Ruiz GM and JB Geller (2015) 2013 Coyote Point None 37.5926 -122.2667
819606 Ruiz GM and JB Geller (2015) 2013 San Leandro None 37.6602 -122.2167
819753 Ruiz GM and JB Geller (2018) 2014 Oyster Point None 37.6937 -122.3689
819754 Ruiz GM and JB Geller (2018) 2014 SF marina None 37.8075 -122.4347
819755 Ruiz GM and JB Geller (2018) 2014 Hayward None 37.6485 -122.2184
819756 Ruiz GM and JB Geller (2018) 2014 Ballena Isle None 37.7583 -122.2841
819757 Ruiz GM and JB Geller (2018) 2014 San Mateo None 37.5938 -122.3036
819758 Ruiz GM and JB Geller (2018) 2014 San Bruno None 37.6479 -122.3662
819759 Ruiz GM and JB Geller (2018) 2014 Richmond None 37.9187 -122.3919
819760 Ruiz GM and JB Geller (2018) 2014 Albany None 37.8877 -122.3247
819761 Ruiz GM and JB Geller (2018) 2014 San Quentin None 37.9372 -122.4787
819762 Ruiz GM and JB Geller (2018) 2014 Richardson bay None 37.8715 -122.4790
819963 Ruiz GM and JB Geller (2018) 2015 Oakland None 37.7056 -122.2473
819964 Ruiz GM and JB Geller (2018) 2015 Ballena Isle None 37.7588 -122.2834
819965 Ruiz GM and JB Geller (2018) 2015 SF marina None 37.8074 -122.4345
819966 Ruiz GM and JB Geller (2018) 2015 Richardson bay None 37.8705 -122.4797
819967 Ruiz GM and JB Geller (2018) 2015 Smithsonian None 37.8981 -122.4623
819968 Ruiz GM and JB Geller (2018) 2015 Hunters Point None 37.7088 -122.3691
819969 Ruiz GM and JB Geller (2018) 2015 Oyster Point None 37.6747 -122.3753
819970 Ruiz GM and JB Geller (2018) 2015 Union City None 37.5865 -122.1743
819971 Ruiz GM and JB Geller (2018) 2015 Albany None 37.8879 -122.3245
819972 Ruiz GM and JB Geller (2018) 2015 San Lorenzo None 37.6480 -122.2159
820183 Ruiz GM and JB Geller (2018) 2016 SF marina None 37.8071 -122.4345
820184 Ruiz GM and JB Geller (2018) 2016 Bay Farm None 37.7237 -122.2632
820185 Ruiz GM and JB Geller (2018) 2016 Brisbane None 37.6560 -122.3697
820186 Ruiz GM and JB Geller (2018) 2016 Mission Bay None 37.7553 -122.3790
820187 Ruiz GM and JB Geller (2018) 2016 Albany None 37.8773 -122.3241
820188 Ruiz GM and JB Geller (2018) 2016 El Cerrito None 37.8885 -122.3367
820189 Ruiz GM and JB Geller (2018) 2016 Richardson bay None 37.8669 -122.4751
820190 Ruiz GM and JB Geller (2018) 2016 Paradise Cay None 37.9044 -122.4684
820191 Ruiz GM and JB Geller (2018) 2016 Oyster Point None 37.6688 -122.3741
820192 Ruiz GM and JB Geller (2018) 2016 Ballena Isle None 37.7516 -122.2878
820403 Ruiz GM, Chang AL, and JB Geller (2023) 2022 Oracle Park None 37.7780 -122.3843
820404 Ruiz GM, Chang AL, and JB Geller (2023) 2022 Tiburon Ferry None 37.8724 -122.4540
820405 Ruiz GM, Chang AL, and JB Geller (2023) 2022 Point Richmond None 37.9082 -122.3941
820406 Ruiz GM, Chang AL, and JB Geller (2023) 2022 San Francisco Marina None 37.8076 -122.4332
820407 Ruiz GM, Chang AL, and JB Geller (2023) 2022 Hunter's Point None 37.7058 -122.3750
820408 Ruiz GM, Chang AL, and JB Geller (2023) 2022 Oyster Point None 37.6797 -122.3774
820409 Ruiz GM, Chang AL, and JB Geller (2023) 2022 Richardson Bay None 37.8624 -122.4636
820410 Ruiz GM, Chang AL, and JB Geller (2023) 2022 Albany None 37.8648 -122.3229
820411 Ruiz GM, Chang AL, and JB Geller (2023) 2022 Oakland None 37.6977 -122.2501
820412 Ruiz GM, Chang AL, and JB Geller (2023) 2022 Ballena Isle None 37.7637 -122.3002

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