''Hypselodoris tryoni'' 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 ...

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 dorid

nudibranch Nudibranchs () are a group of soft-bodied marine gastropod molluscs which shed their shells after their larval stage. They are noted for their often extraordinary colours and striking forms, and they have been given colourful nicknames to matc ...

, a

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 * ...

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 genus

Chromodorididae Chromodorididae, or chromodorids, are a taxonomic family of colourful, sea slugs; dorid nudibranchs, marine gastropod mollusks in the superfamily Doridoidea. “Chromodorid nudibranchs are among the most gorgeously coloured of all animals.” ...

.Caballer, M. (2011)
''Hypselodoris tryoni'' (Garrett, 1873).
Accessed through: World Register of Marine Species on 9 August 2012

Taxonomic history

The decision to include ''Risbecia'' species within the family ''Hypselodoris'' was made on the basis of a molecular (DNA) study which showed that ''Risbecia'' species are a clade inside the genus ''Hypselodoris'' as currently constituted.

Distribution

This species was described from the

Society Islands The Society Islands (french: Îles de la Société, officially ''Archipel de la Société;'' ty, Tōtaiete mā) are an archipelago located in the South Pacific Ocean. Politically, they are part of French Polynesia, an overseas country of the F ...

. It is reported to occur widely in the tropical Western Pacific Ocean from

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

to the

Philippines The Philippines (; fil, Pilipinas, links=no), officially the Republic of the Philippines ( fil, Republika ng Pilipinas, links=no), * bik, Republika kan Filipinas * ceb, Republika sa Pilipinas * cbk, República de Filipinas * hil, Republ ...

.Rudman, W.B., 1999 (January 22
''Risbecia tryoni'' (Garrett, 1873).
nSea Slug Forum. Australian Museum, Sydney.

Description

''Hypselodoris tryoni'' has a brown body and white foot. The body and upper dorsum are covered in purple spots ringed with white or light-brown. The

gills 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 ...

are typically translucent white or light-brown and the

rhinophores A rhinophore is one of a pair of chemosensory club-shaped, rod-shaped or ear-like structures which are the most prominent part of the external head anatomy in sea slugs, marine gastropod opisthobranch mollusks such as the nudibranchs, sea hares ...

are brown to dark-brown and covered in circular white lines. It has a thin blue or purple line on the mantle edge. There is some colour variation between individuals. ''Hypselodoris tryoni'' is similar in appearance to ''

Goniobranchus geminus ''Goniobranchus geminus'', also known as the gem sea slug, is a species of very colourful sea slug, a dorid nudibranch, a marine gastropod mollusc in the family Chromodorididae.Bouchet, P. (2012)''Goniobranchus geminus''.Accessed through: World R ...

'', ''

Goniobranchus kuniei ''Goniobranchus kuniei'' is a species of very colourful sea slug, a dorid nudibranch, a marine gastropod mollusc in the family Chromodorididae.WoRMS (2011)''Goniobranchus kuniei'' Pruvot-Fol, 1930.Accessed through: World Register of Marine Specie ...

'' and '' Goniobranchus leopardus'', although it lacks the wide purple mantle edge line present in those species. ''Goniobranchus'' species also tend to have a lower, more rounded body. Sea slugs such as ''Hypselodoris tryoni'', are known to exhibit trailing behaviour where up to four animals will follow one another very closely, often touching. It is not known what causes this behaviour. ''Hypselodoris tryoni'' reaches at least 60 mm in length and has been observed to raise and lower its head while crawling.

Ecology

Like many slugs in the genus

, ''Risbecia tryoni'' feeds on

sponges Sponges, the members of the phylum Porifera (; meaning 'pore bearer'), are a basal animal clade as a sister of the diploblasts. They are multicellular organisms that have bodies full of pores and channels allowing water to circulate through ...

and have been seen feeding on sponges from the family ''

Dysidea ''Dysidea'' is a genus of sponges belonging to the family Dysideidae. The genus has cosmopolitan distribution. Species: *'' Dysidea aedificanda'' *'' Dysidea amblia'' *'' Dysidea anceps'' *'' Dysidea arenaria'' *'' Dysidea avara'' *'' D ...

''. When feeding they are sometimes accompanied by a group of shrimp, ''

Periclimenes imperator ''Periclimenes imperator'', known as the emperor shrimp, is a species of shrimp with a wide distribution across the Indo-Pacific. It lives commensally on a number of hosts, including the sea slug '' Hexabranchus''. A. J. Bruce A is the fi ...

'', in an apparent form of

commensalism Commensalism is a long-term biological interaction (symbiosis) in which members of one species gain benefits while those of the other species neither benefit nor are harmed. This is in contrast with mutualism, in which both organisms benefit fro ...

.Swann, R., 2007 (May 16
Feeding ''Risbecia tryoni'' from Borneo.
essage in/nowiki> Sea Slug Forum. Australian Museum, Sydney. File:Twin chromodoris, treasure chest, wakatobi, 2018 (45088636004).jpg, Hypselodoris tryoni in

Wakatobi National Park Wakatobi National Park is a marine national park in Southeast Sulawesi, Indonesia. The name of Wakatobi is a portmanteau of the four main Tukangbesi Islands: Wangi-wangi, Kaledupa, Tomia, and Binongko.

, 2018 File:Kuni's chromodoris, fan 38 west, wakatobi, 2018 (45763962462).jpg, Hypselodoris tryoni in

, 2018 File:Risbecia tryoni 2.jpg, ''Hypselodoris tryoni'' File:Risbecia tryoni 1.jpg, ''Hypselodoris tryoni'' exhibiting "trailing" behaviour.

References

External links

* {{Taxonbar, from=Q1133633 Chromodorididae Gastropods described in 1873