Species Description: Siphonaria pectinata possesses an oval, limpet-like shell that is white to cream-tan in color with numerous radial brown stripes. Examined from above, the apex is slightly off-center with respect to both x-axis and y-axis midlines. As with other members of the family, the underside of the shell exhibits a c-shaped muscle scar (often indistinct) that opens to one side. The underside also shows a shallow siphonal groove that passes through the open end of the muscle scar.
Members of the Siphonariidae family are not true limpets. They are a distinct gastropod family exhibiting an evolutionarily convergent (unrelated species exhibit similar form and function) shell morphology well suited for life on wave-swept rocky intertidal shorelines.
Potentially Misidentified Species: Despite the convergent shell morphology of a number of unrelated IRL gastropod taxa, Siphonaria pectinata should be fairly easy to identify. Several keyhole limpets of the genus Diodora occur in the IRL and all of these are readily discernable by the presence of the 'keyhole' opening at the apex of the shell.
Regional Occurrence: Siphonaria pectinata is widespread throughout the Mediterranean and Atlantic basin north of the equator. It is a common rocky high intertidal inhabitant on the Florida east coast and Florida Keys (Voss 1959, Baker et al. 2004).
IRL Distribution: In east Florida Siphonaria pectinata is restricted primarily to rocky intertidal habitats. To the north and south of the IRL, various types of beach rock provide suitable habitat (Craig et al. 1969). Within the IRL region, however, the majority of rocky intertidal sites are manmade habitats such as inlet rock jetties, seawalls, and concrete pier and bridge pilings. In light of its dependence on human-made hard substrate, Baker et al. (2004) refer to S. pectinaria in Florida as an "urban" species.
In the IRL S. pectinaria is a common to abundant inhabitant of the high inertidal rock inlet jetties that connect the estuary to the Atlantic Ocean.
Age, Size, Lifespan: The shell length of Siphonaria pectinata can reach about 30 mm, but most individuals only grow half as large (Baker et al. 2004).
Abundance: Where suitable habitat can be found Siphonaria pectinata can be among the most abundant gastropods of the high intertidal on Florida's east coast. Whitney Laboratory in St. Augustine lists the species as common, indicating that 10-50 individuals can easily be collected from the field in a day. The species is similarly perennially abundant on the rock jetties of Fort Pierce Inlet of the IRL in St. Lucie County.
Reproduction: A study by Ocana and Emson (1999) reveals aspects of the reproductive biology of S. pectinata populations from Gibraltar that may hold for animals in Florida. Maturation occurred between 6-12 months of age when individuals attained a shell length of 5-6 mm. Spawning occurred from March to June, with activity peaking in the second half of this timeframe. Spawning and egg deposit appeared to be less common at exposed sites relative to protected sites.
Small oval ribbons containing several hundred (and up to 1000) eggs in a gelatinous matrix are deposited in shallow depressions, cracks and crevices, usually away from home scars the limpets return to at low tide (Voss 1959, Ocana and Emson 1999).
Embryology: Ocana and Emson (1999) report that fertilized eggs took 14-21 days to develop at ambient temperatures of 14-19ºC. Larvae hatch out as free-swimming veligers exhibiting a planktonic larval stage of short duration. Voss (1959) indicates this to be a primitive trait in pulmonate gastropods.
Temperature: High temperature stress is a distinct possibility in the upper intertidal during periods of exposure and animals have evolved a number ways to reduce thermal stress. Siphonaria pectinata returns to its home scar to wait out periods of exposure to air and potential lethal temperatures (Williams and Morritt 1995). When air temperatures are not extreme S. pectinata may also exhibit a behavior known as 'mushrooming,' i.e., lifting the shell to expose the foot and other tissue, possibly as a means of enhancing evaporative cooling (Lowell 1984). There exists potential conflict in intertidal organisms between the need to combat desiccation and the need to regulate temperature, and suggests water conservation is often the overriding concern.
Salinity: Experimental work by McAlister and Fisher (1968) suggest that Siphonaria pectinata is capable of tolerating salinities between 20 and 40 ppt. Animals exposed to salinities above and below this range were unable to attach to hard surfaces. In addition, no animals survived more than 24 hours after exposure to these extremes. The authors suggest that S. pectinata clamps down on the substratum in response to exposure to salinity extremes, and maintains muscle tonus for extended periods to avoid coming into contact with the extreme environment.
Desiccation: Striped false limpets are well-adapted for life in the high intertidal. McAlister and Fisher (1968) demonstrated that when Siphonaria pectinata are clamped onto a hard substratum they can withstand desiccation for up to 72 hours.
Trophic Mode: Siphonaria pectinata is a grazer that forages short distances from its home scar in the rocky intertidal, scraping epiphytic (plant) material and from hard surfaces with its radula. Voss (1959) suggested the organism fed on encrusting material, but more recent studies indicates that S. pectinata instead grazes superficial, soft algae (including spores and emerging germlings) with its fine-toothed radula (Ocana and Fa 2003).
Associated Species: S. pectinata co-occurs with other rocky intertidal species. In Florida, this assemblage includes several species of barnacles and littorinid snails.
Invasion History: The striped false limpet has been present in Florida waters since the 19th century. Morrison (1963, 1972) believed the species was introduced from the Mediterranean. Carlton (1992), however, suggests the western Atlantic to have been the source of invasion. In both cases accidental transport as fouling organisms on ship hulls is the putative vector. Consensus as to the origins of the species is lacking, however, and it is considered to be cryptogenic by many authorities. (Baker et al. 2004).
Potential to Compete with Natives: Rocky intertidal marine communities occupy a classically space-limited environment. Competition between Siphonaria pectinata and native species would likely be for living spaces as well as food. The apparent dietary semi-specialization of S. pectinata on superficial, soft microalgae may serve to reduce competition with other grazers that consume harder encrusting material (Ocana and Fa 2003).
In some instances, S. pectinata may function as an ecosystem engineer. Craig et al. (1969) reported that grazing by this species facilitates the formation of secondary solution features characteristic of south Florida beach rock by exposing new rock surfaces to biochemical erosion.
Possible Economic Consequences of Invasion: The economic impacts of striped falselimpets has been deemed negligible in the Tampa Bay estuary system (Baker et al. 2004), and a similar assumption may be made with regard to the IRL and Florida east coast where the species occurs.
Baker P., Baker S.M., and Jon Fajans. 2004. Nonindigenous marine species in the greater Tampa Bay ecosystem. Tampa Bay Estuary Program Technical Publication 02-04. 131p.
Biskupiak J.E. and C.M. Ireland. 1983. Pectinatone, a new antibiotic from the mollusc Siphonaria pectinata. Tetrahedron Letters 24:3055-3058.
Carlton J.T. 1992. Introduced marine and estuarine mollusks of North America: An end-of-the-20th-Century perspective. Journal of Shellfish Research 11:489-505.
Craig A.K., Dobkin S., Grimm R.B., and J.B. Davidson. 1969. The Gastropod, Siphonaria pectinata: a Factor in Destruction of Beach Rock. American Zoologist 9:895-901.
Lowell R.B. 1984. Desiccation of intertidal limpets: Effects of shell size, fit to substratum, and shape. Journal of Marine Biology and Ecology 77:197-207.
McAlister R.O. and F.M. Fisher. 1968. Responses of the false limpet, Siphonaria pectinata Linnaeus (Gastropoda, Pulmonata) to osmotic stress. Biological Bulletin 134:96-117.
Morrison J.P.E. 1963. Notes on American Siphonaria. Annual Reports of the American Malacological Union 1963:7-9. Morrison J.P.E. 1972. Mediterranean Siphonaria: West and east-old and new. Argamon 3:51-62.
Ocana T.M.J., and R.H. Emson. 1999. Maturation, Spawning and Development in Siphonaria pectinata Linnaeus (Gastropoda: Pulmonata) at Gibraltar. Journal of Molecular Studies 65:185-193.
Ocana T. and D.A. Fa. 2003. Microalgal availability and consumption by Siphonaria pectinata (L., 1758) on a rock shore. Boletin del Instituto Espanol de Oceanografia 2003:1-4.
Voss, Nancy A. 1959. Studies on the pulmonate gastropod Siphonaria pectinata (Linnaeus) from the southeast coast of Florida. Bulletin of Marine Science 9:84-99.
Williams G.A. and D. Morritt. 1995. Habitat partitioning and thermal tolerance in a tropical limpet, Cellana grata. Marine Ecology Progress Series 124:89-103.