Crepidula formicataCrepidula formicata
Easily seen Crepidula fornicata along the shoreline. Class: Gastropoda Order: Littorinimorpha Family: Calyptraeidae Genus: Crepidula
Distribution It is native to the eastern This species has been introduced to several other countries, coast of North America. especially in Europe. It is considered to be an invasive, nuisance It occurs from the Gulf of species. The first known occurrence of Crepidula fornicata in St. Lawrence in the north Europe was in 1872. It was introduced accidently with imported all the way south to the American oysters. They have been repeatedly introduced ever Gulf of Mexico. since in ballast water and on ships’ hulls.
Habitat They are most abundant in muddy or mixed muddy areas, This species occupies a reaching their highest densities in wave protected locations. variety of seabed surfaces. These include bays, estuaries and sheltered sides of wave- They also occur in a wide exposed islands. In Nova Scotia they are common in intertidal range of environmental and shallow subtidal regions. They attach themselves to almost conditions. any hard surface to be found (including each other and the shells of other living or dead hard-shelled invertebrates.
Food They are active suspension feeders, generating a water current They live off of plankton through the mantle cavity by ciliary (hair-like) action and which they filter out of the trapping food particles on a mucous sheet lying across the front seawater. surface of the gill filament.
Reproduction Being hermaphrodites they contain both male and female The Slipper limpet is a. reproductive organs. Sperm producing ability advances quicker protandric hermaphrodite. than ovum production which results in them being born male. This means it is born as a They often stack on top of each other. Larger females are on the male with the potential to bottom, the smaller males are on the top. Stacks can be viewed become female at a later as independent mating groups with copulation occurring date. Young males seek out between individuals occupying any position in a chain. Males at older females for mating the top fertilize the bisexual individuals below and they in turn purposes. Once they fertilize each other as well as the larger females at the bottom of convert to being female, the stack. These females control the sexual definition of the they remain as females. group by releasing pheromones into the surrounding water.
Development Larvae are pelagic and are found in the water Most females spawn twice column. Growth of the larvae is temperature in a year. Fertilized adult dependent and takes about 2 weeks longer at females create about 45 18° C than at 24° C. After swimming around membrane sacs into which feeding on plankton for several weeks (2 to 4), the they place 250 eggs or so in veliger larvae become capable of metamorphosis. each of these. They are kept The larvae are about 0.4 mm long when released nearby her, either under her and about 1 mm when they metamorphose. A newly foot or attached to the rock formed juvenile limpet may settle on its own or on she is on. She broods these top of an established group. If the individual settles for about a month as they alone, it becomes male briefly, passing rapidly on to develop to the veliger stage. a female. If it settles on a stack it remains a male.
Characteristics On the inside of the shell there is a white "deck", The shell is oval, up to 5 or septum which causes the shell to resemble a boat cm in length. It is smooth or a slipper, hence the common name. The with irregular growth lines. septum protects the visceral mass of the limpet. It can be white, cream, It keeps the important digestive organs in place. yellow or pinkish in colour There is variability in the shape of the shell: with streaks or blotches of some shells are more arched than others. red or brown. The shell of a limpet settling on its own grows Adaptations to fit the substratum. Another limpet may join They form curved stacks of it, thus initiating a stack formation. When up to 12 individuals. Being settling on an existing group maturation from stationary this facilitates juvenile to male and the maintenance of the reproduction. They have male state is promoted by pheromones released the ability to change from by the larger females at the bottom of the stack. being male to female. A If the females in the stack die, one of the larger waterborne hormone males will become a female. Sex change occurs regulates female traits. to the bottom-most male in a stack and takes If the ratio of males to approximately 60 days. During this time the females becomes too high, penis regresses and the pouches and glands of the male reproductive the female duct develop. Adults live on the organs will degenerate and seabed on a variety of surfaces in a wide range the limpet will become a of environmental conditions. They often attach female. to the shells of dead and living hard-shelled invertebrates including scallops, crabs, whelks Status/Threats and mussels. These are considered an invasive species. They occur Natural predators include birds, fish, crabs, in very large numbers in starfish and other marine invertebrates. many areas of the Atlantic Considered to be a threat to marine biodiversity Ocean. these limpets are subject to various eradication programs, including dredging. Studies are ongoing Sightings in Nova Scotia relating to their effect on the environment and control These are very common measurements are in place to limit further expansion. in Nova Scotian waters. They are a great inconvenience to aquacultures, especially oyster and mussel beds.