Scaphopoda
Scaphopoda, commonly known as tusk shells or tooth shells, is a class of marine mollusks that are characterized by their elongated, conical shells that are open at both ends. They are found in a variety of marine environments, from shallow waters to deep-sea trenches, with their distribution ranging from the Arctic to the Antarctic. Unlike other mollusks, scaphopods lack a distinct head and are adapted to a burrowing lifestyle. They use their foot to dig into soft sediments, extending their slender bodies outwards, with their open ends protruding from the sediment.
Characteristics
Scaphopods are typically small, ranging in size from a few millimeters to a few centimeters. Their shells are usually smooth and white, but some species may have ridges or other ornamentation. The shell is composed of calcium carbonate and is typically composed of three layers: the periostracum (outermost layer), the ostracum (middle layer), and the hypostracum (innermost layer). The shell of scaphopods is unique in that it is open at both ends, with one end slightly wider than the other. This allows for the animal to burrow into sediment with its wider end facing downwards, and extend its head and foot out of the narrower end to capture food.
Scaphopods are carnivorous and feed on small marine organisms such as foraminiferans and other benthic invertebrates. They have a unique feeding mechanism, using a long, protrusible proboscis to capture prey. The proboscis is covered in cilia that create currents that sweep food particles towards the mouth. Scaphopods also have a radula, a ribbon-like structure with rows of teeth, that helps them scrape food from the sediment.
Environment
Scaphopods are found in a wide range of marine environments, from the intertidal zone to the deep sea. They are most common in soft sediments, such as sand, mud, and gravel. They are also found in association with coral reefs and seagrass beds. Their distribution is global, with species found in all oceans of the world. Some species are known to live at depths of over 6,000 meters (20,000 feet).
Classification
Scaphopoda is a class within the phylum Mollusca. It is divided into two orders: Dentaliida and Gadilida. The order Dentaliida is the larger of the two orders, with about 200 species. The order Gadilida is smaller, with only about 30 species. Both orders are further divided into families, genera, and species.
Some common examples of scaphopod species include:
- Dentalium entale (Tusk shell)
- Cadulus jeffreysi (Tooth shell)
- Fissidentalium vernedei (Fissidentalium)
References
Scaphopoda: A Review of the Morphology, Biology, and Phylogeny
Scaphopoda
Scaphopoda - Discover Life