Tegula Funebralis
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''Tegula funebralis'', the black turban snail or black tegula, is a
species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
of medium-sized marine
sea snail Sea snails are slow-moving marine (ocean), marine gastropod Mollusca, molluscs, usually with visible external shells, such as whelk or abalone. They share the Taxonomic classification, taxonomic class Gastropoda with slugs, which are distinguishe ...
in the family
Tegulidae Tegulidae is a family of small to large sea snails, marine gastropod mollusks in the superfamily Trochoidea (according to the taxonomy of the Gastropoda by Bouchet & Rocroi, 2005).Bouchet, P. (2013). Tegulidae Kuroda, Habe & Oyama, 1971. Acces ...
.Bouchet, P. (2012). Tegula funebralis (A. Adams, 1855). Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=607163 on 2012-09-10 This eastern
Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five Borders of the oceans, oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is ...
species was previously known as ''Chlorostoma funebralis''.


Description

Most adults have shells which are 20 to 50 mm (or about an inch, to an inch and three quarters) in diameter. Adults weigh anywhere from 2 to 20 grams. Individuals can live anywhere from 7 to 30 years; studies have shown that individuals inhabiting the more northern portions of the organism's range are larger and live longer on average than organisms inhabiting the southern portions. In 1971, a new sense organ was discovered in this marine snail.
Chemoreceptor A chemoreceptor, also known as chemosensor, is a specialized sensory receptor which transduces a chemical substance ( endogenous or induced) to generate a biological signal. This signal may be in the form of an action potential, if the chemorece ...
organs were found near the base on the border of the leaflets of the ctenidium (comb-like respiratory gills), one on each leaflet. They form a light swelling near the base of the leaflet with a pocket lying within the swelling. Together they are termed a "bursicle".


Distribution and habitat

Black turban snails are found along the
Pacific coast Pacific coast may be used to reference any coastline that borders the Pacific Ocean. Geography Americas North America Countries on the western side of North America have a Pacific coast as their western or south-western border. One of th ...
of
North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...
from
British Columbia British Columbia is the westernmost Provinces and territories of Canada, province of Canada. Situated in the Pacific Northwest between the Pacific Ocean and the Rocky Mountains, the province has a diverse geography, with rugged landscapes that ...
to
Baja California Baja California, officially the Free and Sovereign State of Baja California, is a state in Mexico. It is the northwesternmost of the 32 federal entities of Mexico. Before becoming a state in 1952, the area was known as the North Territory of B ...
, where they are one of the most abundant snail species. Studies have recorded densities of up to 1,400 individuals per m2 near
Monterey, California Monterey ( ; ) is a city situated on the southern edge of Monterey Bay, on the Central Coast (California), Central Coast of California. Located in Monterey County, California, Monterey County, the city occupies a land area of and recorded a popu ...
. Local densities are influenced by many factors, including abundance of food, predators, and suitable habitat. This species inhabits rocky
intertidal zone The intertidal zone or foreshore is the area above water level at low tide and underwater at high tide; in other words, it is the part of the littoral zone within the tidal range. This area can include several types of habitats with various ...
s, between
low Low or LOW or lows, may refer to: People * Low (surname), listing people surnamed Low Places * Low, Quebec, Canada * Low, Utah, United States * Lo Wu station (MTR code LOW), Hong Kong; a rail station * Salzburg Airport (ICAO airport code: LO ...
and
high High may refer to: Science and technology * Height * High (atmospheric), a high-pressure area * High (computability), a quality of a Turing degree, in computability theory * High (tectonics), in geology an area where relative tectonic uplift t ...
tide lines. Juveniles are found mostly under rocks and among coarse sands. Empty black turban snail shells are often utilized by another common intertidal animal, the
hermit crab Hermit crabs are anomuran Decapoda, decapod crustaceans of the superfamily (taxonomy), superfamily Paguroidea that have adapted to occupy empty scavenged mollusc shells to protect their fragile exoskeletons. There are over 800 species of hermit c ...
.


Diet

''Tegula funebralis'' is primarily
herbivorous A herbivore is an animal anatomically and physiologically evolved to feed on plants, especially upon vascular tissues such as foliage, fruits or seeds, as the main component of its diet. These more broadly also encompass animals that eat n ...
. Food for ''T. funebralis'' can be categorized as either rock encrusting algae,
macroscopic The macroscopic scale is the length scale on which objects or phenomena are large enough to be visible with the naked eye, without magnifying optical instruments. It is the opposite of microscopic. Overview When applied to physical phenome ...
algae Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...
, or organic
detritus In biology, detritus ( or ) is organic matter made up of the decomposition, decomposing remains of organisms and plants, and also of feces. Detritus usually hosts communities of microorganisms that colonize and decomposition, decompose (Reminera ...
. Studies into the macroscopic algal preferences of ''T. funebralis'' revealed a strong preference for '' Nereocystis luetkana'' and ''
Macrocystis integrifolia ''Macrocystis'' is a monospecific genus of kelp (large brown algae) with all species now synonymous with ''Macrocystis pyrifera''. It is commonly known as giant kelp or bladder kelp. This genus contains the largest of all the Phaeophyceae or b ...
''. Macroscopic algae species preferred by ''T. funebralis'' are similar in that they are non-
calcareous Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime (mineral), lime or being chalky. The term is used in a wide variety of Science, scientific disciplines. In zoology ''Calcare ...
, non-filamentous, and softer in comparison to other macroscopic algae in the region. These species do not grow in the intertidal, so they are only available to ''T. funebralis'' as drift material.


Threats

Predators of ''T. funebralis'' include
sea star Starfish or sea stars are Star polygon, star-shaped echinoderms belonging to the class (biology), class Asteroidea (). Common usage frequently finds these names being also applied to brittle star, ophiuroids, which are correctly referred to ...
s,
crab Crabs are decapod crustaceans of the infraorder Brachyura (meaning "short tailed" in Greek language, Greek), which typically have a very short projecting tail-like abdomen#Arthropoda, abdomen, usually hidden entirely under the Thorax (arthropo ...
s,
octopus An octopus (: octopuses or octopodes) is a soft-bodied, eight-limbed mollusc of the order Octopoda (, ). The order consists of some 300 species and is grouped within the class Cephalopoda with squids, cuttlefish, and nautiloids. Like oth ...
es, sea gulls, and
sea otter The sea otter (''Enhydra lutris'') is a marine mammal native to the coasts of the northern and eastern Pacific Ocean, North Pacific Ocean. Adult sea otters typically weigh between , making them the heaviest members of ...
s. Experiments showed that ''T. funebralis'' will flee if it detects a predator nearby, and if already in motion, can increase its speed from 2–3 cm per minute to around 8 cm per minute. If the
anterior Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position pro ...
portion of ''T. funebralis'' is touched by a predator, it can raise the front of the foot and make a 90° turn to escape. Additionally, if ''T. funebralis'' detects a predator while on a steep surface, it can detach itself and roll down the incline.


Human use

Archaeological evidence shows that humans have utilized black turban snails for over 12,000 years. The edible portion of the snail can range in weight from less than a gram to 8 grams. It is estimated that the average human would need to consume around 400 snails a day to meet their minimum caloric needs if it were the only food consumed. Evidence for human consumption of black turban snails includes the discovery of shell
midden A midden is an old dump for domestic waste. It may consist of animal bones, human excrement, botanical material, mollusc shells, potsherds, lithics (especially debitage), and other artifacts and ecofacts associated with past human oc ...
s in association with tools referred to by researchers as "turban crackers". Evidence from several late Holocene middens suggest that harvesting increased around 3,000 years ago. The analysis of middens found near Point Conception reveal that black turban snails comprised up to 60% of meat yields for the native people in that area. Researchers speculate that the prevalence of eating these snails was probably influenced by the abundance of individuals and the ease of collection.


References


External links

*
photo of operculum
{{Taxonbar, from=Q3137597 funebralis Molluscs of the Pacific Ocean Gastropods described in 1855 Taxa named by Arthur Adams (zoologist)