Carinaria cristata
{{Short description|Species of gastropod}}
{{Speciesbox
| name = Glassy nautilus
| image = Carinaria cristata.jpg
| image_caption = The shell has been removed in the upper specimen. The tail is to the left.
| taxon = Carinaria cristata
| authority = (Linnaeus, 1767)Linnaeus C. (1767). Systema naturae 12a ("13"), Vol. 1, part 2: 533–1327, [https://archive.org/stream/mobot31753002832555#page/1259/mode/2up page 1260].
| synonyms_ref =
| synonyms =
Patella cristata Linnaeus, 1767
}}
Carinaria cristata, commonly known as the glassy nautilus,{{cite web |url=http://www.conchology.be/?t=68&u=634150&g=369c5b1b24f3f729a2b1204b1dbfe46f&q=1d7906c795173432e138a77f97582f09 |title=Carinariidae: Carinaria cristata |work=Shell Encyclopedia |accessdate=2015-04-21}} is a species of pelagic marine gastropod mollusc in the family Carinariidae.{{cite WoRMS |author=Bouchet, Philippe |year=2015 |title=Carinaria cristata (Linnaeus, 1767) |id=574935 |accessdate=2015-04-17 }} It is found in the Pacific Ocean and is described as being holoplanktonic, because it spends its entire life as part of the plankton. It was first described by Carl Linnaeus 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.{{cite book|title=Rare Shells |url=https://books.google.com/books?id=gpg1l2MXTQkC&pg=PA27 |publisher=University of California Press |page=27 }}
Description
Carinaria cristata is a very large gastropod mollusc that can reach a length of {{convert|50|cm}}. 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 retinas 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 gills.{{cite web |url=http://species-identification.org/species.php?species_group=pelagic_molluscs&menuentry=soorten&id=343 |title=Carinaria cristata cristata |author1=van der Spoel, S. |author2=Newman, L.J. |author3=Estep, K.W. |work=Pelagic Molluscs |publisher=Marine Species Identification Portal |accessdate=2015-04-17}}{{cite web |url=http://tolweb.org/Carinaria/28741 |title=Carinaria Lamarck 1801 |author=Seapy, Roger R. |date=2008-07-12 |work= |publisher=Tree of Life Web Project |accessdate=2015-04-17}}
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 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. Although its diet is varied, it feeds selectively on salps and doliolids, but also consumes arrow worms and copepods. The copepods are eaten to a much smaller extent than their proportion in the planktonic community would suggest. Other prey includes siphonophores, planktonic worms, fish eggs and larvae, and juveniles and smaller adults of its own species.{{cite book|author1=Lalli, Carol M. |author2=Gilmer, Ronald W. |title=Pelagic Snails: The Biology of Holoplanktonic Gastropod Mollusks |url=https://books.google.com/books?id=yIAfwz5cxPMC&pg=PA40 |year=1989 |publisher=Stanford University Press |isbn=978-0-8047-1490-7 |pages=40–42}} 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 turtles and tuna.