The family Calpytraeidae is made up of three
genera: Crepidula (slipper shells), Crucibulum (cup and saucer
shells) and Calyptraea (hat shells). All of the species have
limpet-shaped shells with an internal shelly septum. The genera are
distinguished by shell morphology. In Crepidula the shell apex is
directed posteriorly and the internal septum is a flat shelf that attaches along
both sides of the shell. In Crucibulum the shell is conical with a
central apex and a cup-shaped internal septum. In Calyptraea the shell
is conical with a central apex but the internal shelly septum is a coiled ramp.
Shells are often not diagnostic on the species level. Cryptic species often
co-occur but they can usually be distinguished on the basis of developmental
characters and body pigmentation. There are 6 species of Crepidula, one
Crucibulum and one
Calyptraea reported from Florida: Crepidula ustulatulina, C.
depressa, C. atrasolea, C. aculeata, C. maculosa and
C. fornicata, Crucibulum auriculum, and Calyptraea centralis.
Crepidula ustulatulina, is distinguished from other species by the following suite of characters: the
shell is small (usually less than 1.5 cm), smooth, and convex. It is often
cream with distinct chestnut brown spots or streaks, sometimes it is brown
overall with darker spots or streaks. The internal septum is flat and white,
and the animal's left side usually extends somewhat farther forward than does
the right side. The margin is straight or slightly bowed. There is an oval
muscle scar just anterior to the shelf on the animal's right side. The small
apex is usually directly posterior and is slightly rostrate in animals living on
small snails but not in those from flat substrates. The external body color is
light to dark gray with opaque white or cream on the tips of the tentacles and
the lips. There are usually large yellow pigment splotches on the mantle, neck
and sometimes foot, visible only in life.
Potentially Misidentified Species
In Florida the species most similar to
Crepidula ustulatulina are the congeners C. maculosa and C.
fornicata. Both species are significantly larger (4-5 cm) but have brown
markings. C. fornicata is easily differentiated from C. ustulatulina
by the absence of the large muscle scar and the sinusoidal shape margin of the
septum. C. maculosa is uncommon and is usually much larger than C.
ustulatuulina. Juveniles of C. maculosa are indistinguishable
from C. ustulatulina on the basis of morphology.
A sister species to C.
ustulatulina, C. convexa, occurs along the coast of New England at
least as far south as Georgia. Since the southern extent of its range is not
known, it is possible that C. convexa occurs in Florida. It can be
distinguished from C. ustulatulina by the fact that the hatchlings crawl
away from the mother, by the morphology of the salivary glands, and by
differences in allozymes and DNA sequences.
Other similar but distinct species
occur in the southern Caribbean (Crepidula cf. convexa from Panama
and C. navicula). These have small convex shells but instead of being
spotted or streaked the shells are flecked with cream and dark brown and there
is no muscle scar anterior to the septum in these species.
HABITAT AND DISTRIBUTION
This species occurs throughout the Gulf of
Mexico and along the east coast of Florida north to at least Fort Pierce. It is
common in the low intertidal and shallow subtidal, often on dead clam shells and
on columbellids and cerithids in or near sea grass. Those living on large flat
substrates are oval in shape but those on small snails have highly arched and
often compressed on the left side.
Crepidula ustulatulina is likely to occur throughout the IRL,
to date however, it has not been documented north of Ft. Pierce.
LIFE HISTORY AND POPULATION BIOLOGY
Age, Size, Lifespan
Shell size in Crepidula ustulatulina is usually less than 1.5 cm.
Crawls. Hatchlings are briefly planktonic,
swimming freely for approximately an hour before settling to the benthos.
All calyptraeids are protandric hermaphrodites:
small, young animals are males that later change to females as they grow.
All species copulate. Females are able to store sperm for several months.
The females deposit eggs into transparent capsules that they brood between the
neck and the propodium. In some species, swimming larvae hatch from the
capsules; in others, benthic juveniles crawl away from the capsules. Crepidula ustulatulina embryos hatch as swimming pediveligers.
The large eggs (300-340mm) produce direct developing embryos
with a smooth shell, and an average length of 744mm at hatching. The large embryonic
velum is not absorbed prior to hatching and the embryo hatches as a swimming
pediveliger. The non-feeding larvae settle within an hour of hatching. There
are between 3 and 16 eggs in each capsule and the number of eggs per capsule
increases with female size.
Species in all three genera of the Calyptraeidae are suspension feeders. They collect phytoplankton on mucus covering the gills. Phytoplankton are then transported to the mouth on a mucus string along the dorsal right side of the neck. The string is drawn into the mouth by the radula.
Crepidula ustulatulina is common in the low intertidal and
shallow subtidal, often on dead clam shells and on columbellids and cerithids in
or near sea grass. Those living on large flat substrates are oval in shape but
those on small snails have highly arched and often compressed on the left side.
No information is available at this time
Collin, R. 2002. Another last word on Crepidula
convexa and a description of C. ustulatulina sp. nov. (Gastropoda:
Calyptraeidae) from the Gulf of Mexico. Bulletin of Marine Science 70: 177-184.
Collin, R. 2001. The effects of mode of development
on phylogoegraphy and population structure of North Atlantic Crepidula
(Gastropoda Calyptraeidae). Molecular Ecology. 10: 2249-2262.
[This includes, C. atrasolea, C. depressa and C.
Collin, R. 2000. Phylogeny of the Crepidula
plana (Gastropoda Calyptraeidea) cryptic species complex in North
America. Canadian Journal of Zoology. 78: 1500-1514. [This includes C.
depressa and C. atrasolea]