''Cephalopyge trematoides'' is a
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 w ...
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
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 match, ...
. A free-swimming
marine gastropod in the family
Phylliroidae
The Phylliroidae are a family of nudibranch sea snails, highly adapted to a pelagic lifestyle and occurring in tropical surface waters around the globe. The two species of the genus '' Phylliroe'' and '' Cephalopyge trematoides'' that have been ...
. ''Cephalopyge trematoides'' is the only known species in its genus (i.e. the genus is
monotypic
In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispe ...
).
[
]
Etymology
Cephalopyge is a contraction of cephalus (Greek: κεφαλή , "head") and (πūγή, "behind") referring to the position of the anus close to the head. The species epithet trematoides expresses a likeness to flukes.
Description
''C. trematoides'' grows to 2.5 cm in length. It swims at approximately 12 cm/s, by passing several undulatory waves down its body each second. It is flattened and transparent; its internal organs are visible.[Marine species identification portal]
Cephalopyge
an
Cephalopyge trematoides
Pelagic nudibranchs
Of the approximately 3000 species of nudibranch, the vast majority are benthic, only a couple are neustonic, and ''C. trematoides'' is very unusual in that it is pelagic. It is estimated to be one of only five planktonic nudibranch species (another epipelagic example is '' Phylliroe bucephala'').[Orso Angulo-Campillo, Gerardo Aceves-Medina and Raymundo Avedaño-Ibarra, ''Holoplanktonic mollusks (Mollusca: Gastropoda) from the Gulf of California, México']
Further information (including photos):
Nudibranch Encyclopedia Kousuke Chibi
(in Japanese)
References
External links
film of ''Cephalopyge'' swimming
{{Taxonbar, from=Q5063321
Phylliroidae
Gastropods described in 1905