''Onchidella binneyi, also known as Onchidella carpenteri, Onchidium carpenteri,'' and ''Oncidiella hildae,'' is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of air-breathing

sea slug Sea slug is a common name for some marine invertebrates with varying levels of resemblance to terrestrial slugs. Most creatures known as sea slugs are gastropods, i.e. they are sea snails (marine gastropod mollusks) that over evolutionary t ...

, a shell-less

marine Marine is an adjective meaning of or pertaining to the sea or ocean. Marine or marines may refer to: Ocean * Maritime (disambiguation) * Marine art * Marine biology * Marine debris * Marine habitats * Marine life * Marine pollution Military * ...

pulmonate Pulmonata or pulmonates, is an informal group (previously an order, and before that a subclass) of snails and slugs characterized by the ability to breathe air, by virtue of having a pallial lung instead of a gill, or gills. The group includ ...

gastropod The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...

mollusk Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is e ...

in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Onchidiidae Onchidiidae are a family of small, air-breathing sea (and land) slugs. They are shell-less marine (except for 2 species)preview pulmonate gastropod molluscs. Onchidiidae is the only family within the superfamily Onchidioidea. These animals are ...

Description

The ''Onchidella binneyi'' are dark grey sea slugs around 2-3 centimeters in length. They produce a defensive secretion as protection against predators because of the absence of the typical defense mechanism of other gastropods, an external shell. This defensive secretion contains the compound

Onchidal Onchidal is a naturally occurring neurotoxin produced as a defensive secretion by the mollusc '' Onchidella binneyi'' and several other related species in ''Onchidella'', a genus of small, air-breathing sea slugs. It acts as an irreversible acet ...

, which acts as a feeding deterrent. Released after the initial attack, the effect on the predator is irreversible. Onchidal causes the predator to forego the sea-slug as a meal option. The toxicity level to predators and humans is not well known.

Distribution

This species is found along the western coast of the Pacific from the Bahia de Los Angeles in the

Gulf of California The Gulf of California ( es, Golfo de California), also known as the Sea of Cortés (''Mar de Cortés'') or Sea of Cortez, or less commonly as the Vermilion Sea (''Mar Bermejo''), is a marginal sea of the Pacific Ocean that separates the Baja Ca ...

to Ecuador. ''Onchidella binneyi'' are found in the upper intertidal zones of rocky shores. They cannot be on the lower levels because they do not have strong enough grips to withstand the rising and falling tides and the harsh wave activity that occurs in the rocky intertidal zone.

Behavior

''O. binneyi'' feeding and general activity patterns have strong correlations with the rise and fall of the tides. When the tide is low, there is often a burst of activity among the sea slug as they come out to feed. They are most active at night, when they are exposed to air. This is because they lack any adaptation that allows them to clamp tightly to rocks on the intertidal zones. Therefore, when wave surges happen on the shore, they are easily dislodged. Alternatively, when tides are high, ''O. binneyi'' activity is lessened and their presence is sparse.

Importance

Onchidal, when isolated from the defensive secretion of the ''Onchidella binneyi'', has demonstrated growth inhibition of ''

Staphylococcus aureus ''Staphylococcus aureus'' is a Gram-positive spherically shaped bacterium, a member of the Bacillota, and is a usual member of the microbiota of the body, frequently found in the upper respiratory tract and on the skin. It is often positive ...

''. This means it is a compound to inhibit Gram-positive bacteria. This is important because of its antimicrobial activity, which means it can help prevent disease. ''O. binneyi'' performs naturally cytotoxic activities that have a significant effect on lymphocytic leukemia cell growth in humans. They also have substantial growth inhibition for colon cancer cells, epidermoid carcinoma cells, breast cancer cells, and many more. With these agents, anti-tumor drugs can be produced and usher in a new type of cancer treatment. They also produce anti-inflammatory and lipid lowering effects. This means that they are able to lower cholesterol levels in humans.

References

Acetylcholinesterase inhibitors Onchidiidae Gastropods described in 1894 {{onchidiidae-stub