''Carinaria cristata'', commonly known as the glassy nautilus, 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 ...

pelagic The pelagic zone consists of the water column of the open ocean, and can be further divided into regions by depth (as illustrated on the right). The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or wa ...

marine

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 ...

mollusc 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 ...

Carinariidae Carinariidae, known by the common name "heteropods" like their relatives in the Pterotracheoidea, is a taxonomic family of swimming or floating sea snails, pelagic marine gastropod molluscs in the clade Littorinimorpha. Distribution The snails ...

. It is found in the Pacific Ocean and is described as being

holoplankton Holoplankton are organisms that are plankton, planktic (they live in the water column and cannot swim against a current) for their entire life cycle. Holoplankton can be contrasted with meroplankton, which are planktic organisms that spend part of ...

ic, because it spends its entire life as part of the plankton. It was first described by

Carl Linnaeus Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his ennoblement in 1761 as Carl von Linné Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalised binomial nomenclature, the ...

in 1767. Its fragile shell was much prized by early conchologists for their collections, being so rare that it was said to be worth more than its weight in gold.

Description

''Carinaria cristata'' is a very large gastropod mollusc that can reach a length of . The shell is a ribbed, cap-shaped cone, about as wide as it is long. It is relatively small, and the body is too large to retract inside it. The body consists of a short proboscis, a central portion and a crested tail. The whole is roughly cylindrical and has a swimming fin on the opposite side from the shell, with a small sucker on its edge. The gelatinous body is translucent, and the gut and its contents can be seen through the body wall. The

retina The retina (from la, rete "net") is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs. The optics of the eye create a focused two-dimensional image of the visual world on the retina, which then ...

s of the eyes are visible as two black spots. The visceral nucleus, which includes the liver, heart, gonad, sexual glands and kidneys, is a dark, stalked, triangular area protected by the shell, which also houses the

gill A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...

Distribution

There are two forms of this species, ''Carinaria cristata'' form ''cristata'', and ''Carinaria cristata'' form ''japonica''. The former is found in the

Indo-Pacific The Indo-Pacific is a vast biogeographic region of Earth. In a narrow sense, sometimes known as the Indo-West Pacific or Indo-Pacific Asia, it comprises the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the ...

region while the latter is found only in the Pacific. It is uncommon in the Indian Ocean but more plentiful in warm waters off the western coast of North America.

Ecology

''Carinaria cristata'' is carnivorous and is an opportunistic

predator Predation is a biological interaction where 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 th ...

. Although its diet is varied, it feeds selectively on

salp A salp (plural salps, also known colloquially as “sea grape”) or salpa (plural salpae or salpas) is a barrel-shaped, planktic tunicate. It moves by contracting, thereby pumping water through its gelatinous body, one of the most efficient ...

s and

doliolids The Doliolida are an order of small marine animals of the subphylum Tunicata. They are in the class Thaliacea, which also includes the salps and pyrosomes. The doliolid body is small, typically 1–2 mm long, and barrel-shaped; it features ...

, but also consumes

arrow worms The Chaetognatha or chaetognaths (meaning ''bristle-jaws'') are a phylum of predatory marine worms that are a major component of plankton worldwide. Commonly known as arrow worms, about 20% of the known Chaetognatha species are benthic, and can ...

and

copepod Copepods (; meaning "oar-feet") are a group of small crustaceans found in nearly every freshwater and saltwater habitat (ecology), habitat. Some species are planktonic (inhabiting sea waters), some are benthos, benthic (living on the ocean floor) ...

s. The copepods are eaten to a much smaller extent than their proportion in the

plankton Plankton are the diverse collection of organisms found in Hydrosphere, water (or atmosphere, air) that are unable to propel themselves against a Ocean current, current (or wind). The individual organisms constituting plankton are called plankt ...

ic community would suggest. Other prey includes

siphonophore Siphonophorae (from Greek ''siphōn'' 'tube' + ''pherein'' 'to bear') is an order within Hydrozoa, which is a class of marine organisms within the phylum Cnidaria. According to the World Register of Marine Species, the order contains 175 specie ...

s, planktonic worms, fish eggs and larvae, and juveniles and smaller adults of its own species. The food is ingested whole and retained in the oesophagus where it is digested by enzymes secreted by the salivary glands. ''C. cristata'' is eaten by a number of predators including

turtle Turtles are an order of reptiles known as Testudines, characterized by a special shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Cryptodira (hidden necked tu ...

s and

tuna A tuna is a saltwater fish that belongs to the tribe Thunnini, a subgrouping of the Scombridae (mackerel) family. The Thunnini comprise 15 species across five genera, the sizes of which vary greatly, ranging from the bullet tuna (max length: ...

References

{{Taxonbar, from=Q4946522 Carinariidae Gastropods described in 1767 Taxa named by Carl Linnaeus