Carbon dating on Lottia gigantea shells found on the California Channel Islands revealed human harvesting for over 10,000 years. In modern history, California commercial fishing occurred during the majority of the 1900s until harvest levels declined in the 1990s. Since L. gigantea has no effective defenses against human predation, people have significantly impacted the larger, predominantly female population. To compensate for the loss of females, males utilize the plasticity of their genes to mature faster and transform into females.
The American black oystercatcher preys on giant owl limpets. Approximately 45% of the adult bird’s diet is chiefly limpets. An adult bird cannot pry a mature female from its home scar due to the limpet’s formidable adhesive strength, so smaller male limpets are routinely removed. Oystercatchers are sensitive to human presence and avoid human populated areas. In a remote setting, a single wintering flock can remove hundreds of limpets during a single low tide, and one study reported that L. gigantea represented 78% of the limpets that parents fed to young chicks.
When confronted by the predatory sea star Pisaster ochraceus, L. gigantea will "mushroom" by lifting its shell off the rock to reduce drag and allow for speedier retreat. When fleeing, L. gigantea hastily withdraws, crawling upwards on the substratum at a rate comparable to territorial ramming speed. The sea star cannot crawl out of water to follow, because its locomotory system functions only when the animal is submerged.
The angular unicorn snail also preys on L. gigantea which defends itself by mushrooming or bulldozing these predatory gastropods.
Known Predators:
Anti-predator Adaptations: cryptic
Lottia gigantea gets its name from the brown outline found on the inner surface of its shell which resembles the silhouette of the tufted Great Horned Owl. Lottia gigantea is North America’s largest limpet, and adults average 8 to 10 cm in length. As with all prosobranchs, limpets have a mantle, shell, foot and radula. The mantle secretes a calcium carbonate shell to protect its soft, visceral tissues. The low, rounded univalve is oval shaped, and its apex is off center and closer to the anterior end. The rough shell is mottled with light grey and brown colors which camouflage it within its rocky intertidal habitat. Attached atop the shell, the smaller rough limpet Collisella scabra can often be found, as well as bluish scars indicating locations of prior hitchhikers.
The muscular foot is its means of locomotion and is light orange in color. The radula is a ribbon of teeth used to scrape algae off of rocks and other hard substrata. As the anterior teeth are worn down, new ones are replaced from the posterior end of the radula.
Range length: 8 to 10 cm.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry
Sexual Dimorphism: sexes alike; female larger
Based on 100 years of museum collection data, Lottia gigantea are long-lived to 20 years of age.
Range lifespan
Status: wild: 20 (high) years.
Range lifespan
Status: captivity: N/A (low) hours.
Typical lifespan
Status: wild: N/A (low) hours.
Typical lifespan
Status: captivity: N/A (low) hours.
Lottia gigantea resides in mussel beds and on bare rock in the middle to high rocky intertidal zone. This narrow, vertical zone is covered by high tide. During the day, a limpet clamps down within its home scar to prevent desiccation and overheating. Its adhesion is so strong that regardless of its orientation on the substratum, the limpet is not dislodged by high-energy wave impacts.
Range elevation: 0 to 2 m.
Range depth: -1 to 0 m.
Habitat Regions: temperate ; saltwater or marine
Aquatic Biomes: coastal
Other Habitat Features: intertidal or littoral
The owl limpet, Lottia gigantea, lives on North America’s Pacific coast, from Baja California, Mexico, to Washington in the United States. Predation and exploitation have reduced the extent of the species' northern range, whereas populations in the southern range are relatively stable. The greatest abundance of this species is found in the middle of its range, offshore of San Diego, California.
Biogeographic Regions: nearctic (Native ); pacific ocean (Native )
The female Lottia gigantea is a territorial herbivore that alters its environment by gardening. The limpet maintains a 1 mm thick algae mat of nearly 1000 square centimeters around its home scar. Garden size is proportional to shell size. After exposure to approximately 20 minutes of incoming tidal splash, the limpets begin to graze. While eating, glands on the foot secrete a sticky pedal mucus trail that acts like fertilizer, trapping bacteria and stimulating algae growth for later consumption. This pedal or provendering mucus is a nutritional adaptation which also aids in locomotion.
Provendering mucus lasts significantly longer and differs chemically and physically from stationary mucus. Stationary mucus has a high water content (93.5%) to reduce desiccation while resting on its home scar between high tides. Provendering mucus contains nourishing proteins and carbohydrates. Before L. gigantea forages, it encircles its home scar, depositing a lot of provendering mucus which it retraces on its return trip home.
The female limpet uses its radula to scrape back and forth on rock, removing the surface layer of algae. Distinctive, parallel scraping marks remain after the day’s feeding. On subsequent days, adjacent areas within the algae patch are grazed. The female moderately grazes all of its territory in patches over 3-4 days. Careful management promotes long-term benefits, and a competent female can maintain the same garden for at least 4 years. Removal of a mature female limpet from its home range can have devastating effects, as trespassing juveniles, non-territorial males, and interspecific species raze the algal meadow within 2 weeks, leaving nothing to farm. If transplanted to a barren area, Lottia will generate another 1000 square cm algae garden within approximately 3 weeks.
In contrast, a non-territorial neighboring male does not create a garden; therefore, he has neither foraging strategy nor resources to protect. Instead, the male is an opportunistic feeder that raids female gardens, eating indiscriminately and disregarding recent grazing trails. The intrusive male eats in the garden until detected, then hastily retreats from the alerted female.
Animal Foods: zooplankton
Plant Foods: algae
Other Foods: microbes
Primary Diet: herbivore (Algivore); planktivore
Lottia gigantea was the first lophotrochozoan selected for whole genome sequencing by the Joint Genome Institute in order to shed light on the origin of the owl limpet's evolutionary success. The genome was sequenced in 2007, and the sequence data are available from The Genome Portal of the Department of Energy Joint Genome Institute website.
A female Lottia gigantea must come in tactile contact with an intruder before the trespasser is perceived. Approximately 70% of the time, trespassers are detected. Scientists do not know how the mucus trails of a female acts as a territory marker; however, female L. gigantea avoid mucus of conspecific females, indicating chemoreception/chemical sensory ability.
Lottia gigantea can distinguish between grazers, predators, and benign foreign objects. In experiments, objects such as a human finger, pencil erasers, and steel pegs elicited no response and were likely perceived by the limpets as obstructions.
Communication Channels: tactile ; chemical
Perception Channels: tactile ; chemical
Marine Protected Areas, or MPAs, offer incidental poaching protection so males and females can grow larger and more slowly at a more natural rate. In 1999, commercial fishing of Lottia gigantea was prohibited in California; however, recreational harvesting is permitted with a daily limit of 35 individuals per person. The resilient intertidal limpet population is a human-stressed species. Shifting baselines of reduced shell length and decreasing population size show the need for effective monitoring, enforcement, and habitat management; these can be accomplished not only by extending MPAs in California for intertidal organisms such as L. gigantea, but also for countless marine species worldwide.
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
During high tide in January or February, Lottia gigantea annually broadcast spawn directly into the water. Large amounts of gametes are released from the intertidal zone and swept out by the tide into the open ocean where they unite with gametes from conspecifics in the process of external fertilization. The developing larvae are part of the zooplankton which feed on phytoplankton. Scientists have not determined the length of time required to develop from gametes into veliger larvae, a ciliated free-swimming stage, because the microscopic larvae are indistinguishable from those of other limpets. In similar Lottia species, Lottia digitalis and Lottia asmi, each take five days to reach metamorphic competence, transforming to the settlement stage.
Tides, longshore, and Davidson currents return mollusk larvae to shore where they adhere to mussel shells or hard substrate cracks and crevices within the mussel bed community. Due to the long stretches of unsuitable sandy beach habitat along the California coast, Lottia gigantea larvae can settle only within the rocky intertidal coastline where they can continue to grow. Owl limpets are indistinguishable from other limpets when shell length is less than 15 mm. Between two to three years old, males transition into females.
Growth rate is slower and highly varied in mussel bed communities. On bare rock, the majority of growth takes place in spring and summer, and minimal growth occurs in autumn and winter when limpets allocate resources to gamete development.
Development - Life Cycle: metamorphosis ; indeterminate growth
There are no known adverse effects of Lottia gigantea on humans.
In the 1980s, owl limpet commercial harvesting peaked and then declined in the 1990s, although numerous incidents of contemporary poaching indicate that Lottia gigantea is still a desirable harvested species. Unfortunately, large scale poaching occurs regardless of site protection. In September 2004 at Rancho Marino Reserve in Cambria, California, a full-time resident manager noted four major harvesting occurrences, including the illegal collection of 2500 limpets. On a smaller scale, in 2005 at White’s Point near Los Angeles, a family collected approximately 75 owl limpets.
Positive Impacts: food ; research and education
Lottia gigantea are herbivores whose behaviors affect nearby conspecifics as well as other species within the middle to upper intertidal community. The shells of female owl limpets serve as substrata to commensal organisms such as small barnacles and limpets including the rough limpet, Lottia digitalis, and L. pelta. Females are territorial algae gardeners. Preferential removal of a larger female affects the species composition of the local microhabitat. Smaller limpets consume the unguarded microalgae while mussels, barnacles, and anemones move in to compete for the newly unoccupied space.
Owl limpets are an important food source for shorebirds such as the American black oystercatcher and are collected by humans for subsistence and for fishing bait.
Commensal/Parasitic Species:
During high tides in January or February, owl limpets annually broadcast spawn.
Lottia gigantea is a protandric sequential hermaphrodite, in that an individual begins life as male. A subordinate male grows well into adulthood within an area of densely aggregated conspecifics, but after an adult male acquires personal territory, his behavior changes to that of a solitary, dominant, territorial limpet, thus triggering sex change from male to female.
Adult males are physically smaller and substantially outnumber the larger, solitary females, yet males produce far less gonadal mass. Less available male gonadal production leads to lower reproduction within the population. Of potentially greater reproductive stress is human predation.
Humans collect larger individuals for the shell, the muscular foot, and for fish bait. Size-selective harvesting targets sexually mature females, reducing their overall body size and lowering the population's reproductive potential. In addition, human selection has driven the evolution of different life history characteristics in this species. Owl limpets in harvested areas change sex at a smaller size, and grow more slowly than L. gigantea in Marine Protected Areas where sex change occurs in larger, faster growing individuals.
Breeding interval: Owl limpets annually broadcast spawn during January or February winter high tides
Breeding season: January or February
Average age at sexual or reproductive maturity (female): 3 years.
Range age at sexual or reproductive maturity (male): 2 to 3 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sequential hermaphrodite (Protandrous ); fertilization (External ); broadcast (group) spawning
There is no parental involvement after releasing gametes.
Parental Investment: no parental involvement
There are shell matrix proteins (SMPs) that are present in all mollusks. These proteins are an assemblage of biomolecules that are known to increase the fracture resistance of the shell by severla orders of magnitude, determine the polymorph of calcium carbonate deposited, and regulate crystal nucleation, growth initiation and termination (Marine et. al 2013). By studying these proteins in Lottia gigantea, scientists are able to understand how these proteins evolved and contributed to the overall diversity and expansion of metazoa life during the Cambrian Period 543 million years ago. From the calcium carbonate shell in Lottia gigantea, 39 SMPs were discovered through proteomic analysis and genomic transcriptomic database interrogations. These SMPs suggest that they lie in the shell matrix, showing highly conserved and linage-specific bioremineralizing proteins (Marie et. al 2013). From this, it was concluded that there may be an ancestral molluscan SMP that contributes to the diversity of shell microstructures found in mollusks in present day.
Lottia gigantea can be genotyped for 6 microsatellite markers from populations across California to explore the genetic structure and diversity of the species and an overall understanding of its exploited populations (Fenberg et. al 2010). By genotyping this species, it was found that there is no significant genetic structure or diversity in this California species. However, phenotypic plasticity explains the reason why there is high gene flow among populations and the differences in their life history, demography and body size between protected and exploited populations (Fenberg er. al 2010). Even though phenotypic plasticity effects are difficult to understand, exploited populations can begin to recover if the proper actions are taken to reduce or eliminate harvesting of L. gigantea. In order to reduce harvesting, effective management needs to take into account the genetic data,the history, ecology, biogeography and life history parameters (Fenburg et. al 2010). Therefore, management must take place to restore exploited populations to further understand whether size-selective harvesting has had a long-term impact on the biology of this species.
Дөө лоттия (лат. Lottia gigantea) – деңиз үлүлдөрүнүн бир түрү.
Lottia gigantea, common name the owl limpet, is a species of sea snail, a true limpet, a marine gastropod mollusc in the family Lottiidae. Its genome has been sequenced at the Joint Genome Institute.
The owl limpet is found on the Pacific coast of North America from northern California to southern Baja California.[1]
The owl limpet grows to a length of up to nine centimetres. The often much eroded shell has an elongated low cone shape with the apex close to one end. The anterior slope is concave. The general colour is brownish grey with pale markings and the foot is pale grey with a yellow or orange sole. There is also a small form that lives on the shells of mussels. It is even more elongated, up to twenty-five millimetres long, and dark blue with concentric growth rings. Lottia gigantea present a muscular orange foot.[2][1]
Round the edge of the foot the owl limpet has a distinctive pallial gill system which uses currents caused by the beating of cilia to circulate water over the gills when submerged.[3]
It is most abundant in California and favours vertical rock faces in wave-swept areas in the upper littoral zone. It grows slowly and may live for up to twenty years.[4] It browses on microalgae growing on rock surfaces.[1]
The owl limpet is a territorial species and some individuals return to the same specific homesite every time the tide goes out. The limpet's contours grow to fit the homesite rock surface tightly.[5]
Owl limpets are protandric hermaphrodites. They spend about two years as juveniles before starting their reproductive lives as male limpets. If they survive long enough, some of them later transform into females. Spawning takes place once a year in the winter. The larvae are pelagic and form part of the zooplankton. They may be transported large distances by currents before settling on suitable rock surfaces.[6]
Larger individuals will themselves have encrusting animals such as barnacles and algae growing on their shells. Sometimes the shell will be used by other limpets or chitons for grazing on the microalgae that grows there. The black oystercatcher, Haematopus bachmani is the only known predator of the owl limpet[6] but they are also harvested by humans for food.[7]
Large female limpets graze on the film of algae growing on rocks and defend their territory against other owl limpets, mobile gastropods, mussels, sea anemones, barnacles and macroalgae. Large competitors are dislodged by pushing them away with the anterior part of the shell, and if barnacles settle, they are rasped away with the radula. In this way, each individual maintains a territory of about 900 square centimetres. It selectively grazes its algal meadow maintaining a turf depth of at least one millimetre. In spring and summer, these green meadows are visible from fifteen metres away and if the owl limpet is transplanted to a new area, it establishes a new meadow over the course of about three weeks.[8][9]
Lottia gigantea, common name the owl limpet, is a species of sea snail, a true limpet, a marine gastropod mollusc in the family Lottiidae. Its genome has been sequenced at the Joint Genome Institute.
Lottia gigantea est une espèce de mollusque appartenant à la famille des Lottiidae.
On la trouve sur la côte ouest de l'Amérique du Nord depuis l'État de Washington jusqu'en Basse-Californie. Elle est très abondante en Californie.
Elle apprécie les parois verticales balayées par les vagues dans la partie supérieure de la côte.
Elle grandit lentement et peut vivre jusqu'à vingt ans. Elle broute les microalgues croissant sur la surface des rochers.
C'est une espèce territoriale et certains individus reviennent au même endroit chaque fois que la marée se retire.
Elle a une longueur moyenne de 9 cm lorsqu'elle est adulte.
L'homme et l'Huîtrier de Bachman sont ses seuls prédateurs.
Lottia gigantea est la première espèce de mollusque dont le génome ait été séquencé par le Joint Genome Institute.
Lottia gigantea is een slakkensoort uit de familie van de Lottiidae.[1] De wetenschappelijke naam van de soort is voor het eerst geldig gepubliceerd in 1834 door Gray in G. B. Sowerby I.
Bronnen, noten en/of referenties
