''Leukoma staminea'', commonly known as the Pacific littleneck clam, the littleneck clam, the rock cockle, the hardshell clam, the Tomales Bay cockle, the rock clam or the ribbed carpet shell, is a species of

bivalve Bivalvia () or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class (biology), class of aquatic animal, aquatic molluscs (marine and freshwater) that have laterally compressed soft bodies enclosed b ...

mollusc Mollusca is a phylum of protostome, protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant taxon, extant species of molluscs are recognized, making it the second-largest animal phylum ...

in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Veneridae The Veneridae or venerids, common name: Venus (mythology), Venus clams, are a very large family of minute to large, saltwater clams, marine bivalve molluscs. Over 500 living species of venerid bivalves are known, most of which are edible, and m ...

. This species of mollusc was exploited by early humans in

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 ...

; for example, the

Chumash people The Chumash are a Native Americans in the United States, Native American people of the central and southern coastal regions of California, in portions of what is now Kern County, California, Kern, San Luis Obispo County, California, San Luis O ...

s of

Central California Central California is generally thought of as the middle third of the U.S. state of California, north of Southern California (which includes Los Angeles and San Diego) and south of Northern California (which includes San Francisco and San Jose, ...

harvested these clams in

Morro Bay Morro Bay (''Morro'', Spanish for "Hill") is a seaside city in San Luis Obispo County, California, United States. Located on the Central Coast of California, the city's population was 10,757 as of the 2020 census, up from 10,234 at the 2010 ...

approximately 1,000 years ago, and the distinctive shells form

middens 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 occupati ...

near their settlements.

Description

Like other members of Veneridae, this species has a chalky shell, the umbo being anterior to the midline of the shell, but closer to the midline than to the anterior end of the shell. The two equal-sized valves are oval or heart-shaped. The width of the shell is greater than a quarter of its length, and the shell seldom exceeds in length. The umbones point towards the anterior end of the shell. The hinge has three cardinal teeth in each valve, and a row of small teeth along the ventral margins of the valves. There are numerous concentric ridges, more clearly demarcked at the anterior end, but the radial ridges are often more clearly sculpted. The foot is large and there is a clearcut pallial sinus.

Right and left valve of the same specimen: File:Leukoma staminea 01.jpg, Right valve File:Leukoma staminea 02.jpg, Left valve

Distribution and habitat

''Leukoma staminea'' is native to the eastern Pacific Ocean. Its range extends along the coasts of North America from the

Aleutian Islands The Aleutian Islands ( ; ; , "land of the Aleuts"; possibly from the Chukchi language, Chukchi ''aliat'', or "island")—also called the Aleut Islands, Aleutic Islands, or, before Alaska Purchase, 1867, the Catherine Archipelago—are a chain ...

and

Alaska Alaska ( ) is a non-contiguous U.S. state on the northwest extremity of North America. Part of the Western United States region, it is one of the two non-contiguous U.S. states, alongside Hawaii. Alaska is also considered to be the north ...

in the north 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 ...

in the south. It usually occurs in protected areas on sand, hard mud and clayey-gravel substrates from the mid and lower shore down to depths of about , usually buried less than beneath the surface of the sediment. Occasionally it is in more exposed locations, in gravel-filled cracks in rocks or in empty burrows of other clams.

Ecology

This clam is a

filter feeder Filter feeders are aquatic animals that acquire nutrients by feeding on organic matters, food particles or smaller organisms (bacteria, microalgae and zooplanktons) suspended in water, typically by having the water pass over or through a s ...

and consumes microscopic

alga Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular microalgae, suc ...

e such as

dinoflagellate The Dinoflagellates (), also called Dinophytes, are a monophyletic group of single-celled eukaryotes constituting the phylum Dinoflagellata and are usually considered protists. Dinoflagellates are mostly marine plankton, but they are also commo ...

diatom A diatom (Neo-Latin ''diatoma'') is any member of a large group comprising several Genus, genera of algae, specifically microalgae, found in the oceans, waterways and soils of the world. Living diatoms make up a significant portion of Earth's B ...

s, and

cyanobacteria Cyanobacteria ( ) are a group of autotrophic gram-negative bacteria that can obtain biological energy via oxygenic photosynthesis. The name "cyanobacteria" () refers to their bluish green (cyan) color, which forms the basis of cyanobacteri ...

. Some dinoflagellates produce

neurotoxin Neurotoxins are toxins that are destructive to nervous tissue, nerve tissue (causing neurotoxicity). Neurotoxins are an extensive class of exogenous chemical neurological insult (medical), insultsSpencer 2000 that can adversely affect function ...

s, such as

saxitoxin Saxitoxin (STX) is a potent neurotoxin and the best-known paralytic shellfish toxin. Ingestion of saxitoxin by humans, usually by consumption of shellfish contaminated by toxic algal blooms, is responsible for the illness known as paralytic she ...

and its derivates, that

bioaccumulate Bioaccumulation is the gradual accumulation of substances, such as pesticides or other chemicals, in an organism. Bioaccumulation occurs when an organism absorbs a substance faster than it can be lost or eliminated by catabolism and excretion. Th ...

in the clams and other bivalve mollusks and can cause

paralytic shellfish poisoning Paralytic shellfish poisoning (PSP) is one of the four recognized syndromes of shellfish poisoning, which share some common features and are primarily associated with bivalve mollusks (such as mussels, clams, oysters and scallops). These shellfi ...

(PSP) when the clams are eaten. Despite this fact, the clam was eaten by Native Americans and is still used as a food for humans. According to a 1996 report from the Marine Advisory Program at the

University of Alaska The University of Alaska Fairbanks (UAF or Alaska) is a public land-, sea-, and space-grant research university in College, Alaska, United States, a suburb of Fairbanks. It is the flagship campus of the University of Alaska system. UAF was e ...

, the

United States Food and Drug Administration The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respo ...

(FDA) considers seafood unsafe if it contains more than 80

μg In the metric system, a microgram or microgramme is a Physical unit, unit of mass equal to one millionth () of a gram. The unit symbol is μg according to the International System of Units (SI); the recommended symbol in the United States and Uni ...

of PSP-causing toxins per 100 g of tissue of the seafood. PSP is caused by a mixture of at least 21 different chemical species, some of which undergo chemical transformations within the dinoflagellates or within the animals that acquire the saxitoxins, and which are retained by different animals for different lengths of time. It is clear that PSP-causing toxin levels are typically much higher in the summer months though this does not mean the seafood is necessarily safe at other times. Risks also vary based on species but seafood available for retail sale is required to meet the FDA standards. In PSP poisonings that occurred in the summer of 1993 in

Kodiak, Alaska Kodiak (Alutiiq language, Alutiiq: ) is the main city and one of seven communities on Kodiak Island in Kodiak Island Borough, Alaska, Kodiak Island Borough, Alaska. All commercial transportation between the island's communities and the outside ...

, saxitoxin levels as high as 19,600 μg / 100 g were measured in the Alaska blue mussel ''

Mytilus edulis The blue mussel (''Mytilus edulis''), also known as the common mussel, is a medium-sized edible marine (ocean), marine bivalve mollusc in the family (biology), family Mytilidae, the only extant family in the order (biology), order Mytilida, known ...

'' – sufficient to provide a lethal dose in a single 2.5 g mussel. By contrast, the highest measured level of saxitoxin in the Pacific littleneck clam was 580 μg / 100 g according to this 1996 report. Littleneck clams are "typically less toxic and retain their toxins for a shorter amount of time than the other species" such as "butter clams and blue mussels

hat A hat is a Headgear, head covering which is worn for various reasons, including protection against weather conditions, ceremonial reasons such as university graduation, religious reasons, safety, or as a fashion accessory. Hats which incorpor ...

tend to accumulate the highest levels of PSP toxins ... ndgeoducks and scallops

tend to be toxic for longer periods of time" but this does not mean that these clams "are always safe to eat syou can get PSP from littleneck clams." The reason for the difference is likely that the littleneck clam has an

enzyme An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...

that converts saxitoxin into

decarbamoylsaxitoxin Decarbamoylsaxitoxin, abbreviated as dcSTX, is a neurotoxin which is naturally produced in dinoflagellate. DcSTX is one of the many analogues of saxitoxin (STX). Saxitoxin is a tricyclic alkaloid compound, which has multiple structural related n ...

, a capability not shared by the blue mussel nor by the butter clam ''

Saxidomus gigantea ''Saxidomus gigantea'' is a large, edible saltwater clam, a marine bivalve mollusk in the family Veneridae, the venus clams. It can be found along the western coast of North America, ranging from the Aleutian Islands to San Francisco Bay. Commo ...

'' (in which levels of saxitoxin as high as 7,750 μg / 100 g have been reported). This transformation to decarbomyl derivative has been reported in some other clam species and significantly reduces the toxicity of saxitoxins present.

Predators Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill ...

include such molluscs as the leafy hornmouth snail (''Ceratostoma foliatum'') and Lewis's moon snail (''Neverita lewisii''), the crabs ''

Metacarcinus magister The Dungeness crab (''Metacarcinus magister'') makes up one of the most important seafood industries along the west coast of North America. Its typical range extends from Alaska's Aleutian Islands to Point Conception, near Santa Barbara, Califor ...

'' and ''

Cancer productus ''Cancer productus'', one of several species known as red rock crabs, is a crab of the genus ''Cancer'' found on the western coast of North America. This species is commonly nicknamed the Pearl of the Pacific Northwest. Description ''Cancer p ...

'', the

giant Pacific octopus The giant Pacific octopus (''Enteroctopus dofleini''), also known as the North Pacific giant octopus, is a large marine cephalopod belonging to the genus '' Enteroctopus'' and Enteroctopodidae family. Its spatial distribution encompasses much o ...

(''Enteroctopus dofleini'') and the

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 ...

. Fish such as the

Pacific staghorn sculpin The Pacific staghorn sculpin (''Leptocottus armatus'') is a species of marine ray-finned fish belonging to the family Cottidae, the typical sculpins. This species is found in the eastern Pacific Ocean. It is the only species in the monospecific ...

sometimes nips off the siphons when they are extended to feed. This clam spawns during the summer in the north of its range. It is a slow-growing species and may live for up to sixteen years.

References

{{Taxonbar, from=Q3014651 Veneridae Molluscs of the Pacific Ocean Seafood in Native American cuisine Bivalves described in 1837 Taxa named by Timothy Abbott Conrad