''Janolus'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of small to large

sea slug Sea slug is a common name for some Marine biology, marine invertebrates with varying levels of resemblance to terrestrial Slug, slugs. Most creatures known as sea slugs are gastropods, i.e. they are Sea snail, sea snails (marine gastropod moll ...

s, or more accurately

nudibranch Nudibranchs () are a group of soft-bodied marine gastropod molluscs, belonging to the order Nudibranchia, that shed their shells after their larval stage. They are noted for their often extraordinary colours and striking forms, and they have b ...

s, marine

gastropod Gastropods (), commonly known as slugs and snails, belong to a large Taxonomy (biology), taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, freshwater, and fro ...

mollusk Mollusca is a phylum of protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant species of molluscs are recognized, making it the second-largest animal phylum after Arthropoda. The ...

s, in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Janolidae. The name ''Janolus'' is derived from the two-headed god

Janus In ancient Roman religion and myth, Janus ( ; ) is the god of beginnings, gates, transitions, time, duality, doorways, passages, frames, and endings. He is usually depicted as having two faces. The month of January is named for Janus (''Ianu ...

, in ancient Roman mythology.

Description

Adult individuals of ''Janolus'' species can be between 2.5 cm to 8 cm long, depending on the species. They are semi-translucent and the body is covered in short

cerata :''The tortrix moth genus ''Cerata'' is considered a junior synonym of ''Cydia (genus), Cydia. Cerata, singular ceras, are anatomical structures found externally in nudibranch sea slugs, especially in aeolid nudibranchs, marine animal, marine opi ...

Distribution

''Janolus'' species are found in many areas world-wide, including

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

and

Africa Africa is the world's second-largest and second-most populous continent after Asia. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 20% of Earth's land area and 6% of its total surfac ...

Ecology

Habitat

This genus of nudibranch is found in shallow and

subtidal The neritic zone (or sublittoral zone) is the relatively shallow part of the ocean above the drop-off of the continental shelf, approximately in depth. From the point of view of marine biology it forms a relatively stable and well-illuminate ...

waters.

Feeding habits

''Janolus'' species feed on

Bryozoa Bryozoa (also known as the Polyzoa, Ectoprocta or commonly as moss animals) are a phylum of simple, aquatic animal, aquatic invertebrate animals, nearly all living in sedentary Colony (biology), colonies. Typically about long, they have a spe ...

, moss animals.

Predators

In California, '' Navanax'' is a known predator of ''Janolus''. ''Navanax'' tracks the slime of ''Janolus'' by using

chemoreceptors A chemoreceptor, also known as chemosensor, is a specialized sensory receptor which transduces a chemical substance ( endogenous or induced) to generate a biological signal. This signal may be in the form of an action potential, if the chemorece ...

. When ''Janolus'' is about to be caught, it rolls into a ball, leaving its cerata exposed.

Species

Species in the genus ''Janolus'' include:MolluscaBase (2019). MolluscaBase
''Janolus'' Bergh, 1884.
Accessed on 2020-10-20. * '' Janolus anulatus'' Camacho-Garcia & Gosliner, 2006 * ''

Janolus australis ''Janolus'' is a genus of small to large sea slugs, or more accurately nudibranchs, marine (ocean), marine gastropod mollusks, in the family (biology), family Janolidae. The name ''Janolus'' is derived from the two-headed god Janus (mythology), J ...

'' Bergh, 1884 * '' Janolus chilensis'' M.A. Fischer, Cervera & Ortea, 1997 * ''

Janolus comis ''Janolus'' is a genus of small to large sea slugs, or more accurately nudibranchs, marine (ocean), marine gastropod mollusks, in the family (biology), family Janolidae. The name ''Janolus'' is derived from the two-headed god Janus (mythology), J ...

'' Er. Marcus, 1955 * '' Janolus eximius'' Miller & Willan, 1986 * '' Janolus faustoi'' Ortea & Llera, 1988 * '' Janolus flavoanulatus'' Pola & Gosliner, 2019 * '' Janolus hyalinus'' (Alder and Hancock, 1854) * '' Janolus ignis'' Miller & Willan, 1986 * '' Janolus incrustans'' Pola & Gosliner, 2019 * '' Janolus kinoi'' Edmunds & Carmona, 2017 * '' Janolus mirabilis'' Baba & Abe, 1970 * ''

Janolus mokohinau ''Janolus'' is a genus of small to large sea slugs, or more accurately nudibranchs, marine gastropod mollusks, in the family Janolidae. The name ''Janolus'' is derived from the two-headed god Janus, in ancient Roman mythology. Description Adul ...

'' Miller & Willan, 1986 * '' Janolus mucloc'' (Er. Marcus, 1958) * '' Janolus rebeccae'' Schrödl, 1996 * '' Janolus savinkini'' Martynov & Korshunova, 2012 * '' Janolus toyamensis'' Baba & Abe, 1970 * '' Janolus tricellariodes'' Pola & Gosliner, 2019 ;Species brought into synonymy: * ''Janolus barbarensis'' (J. G. Cooper, 1863):synonym of '' Antiopella barbarensis'' (J. G. Cooper, 1863) * ''Janolus capensis'' Bergh, 1907:synonym of '' Antiopella capensis'' (Bergh, 1907) (original combination) * ''Janolus costacubensis'' Ortea & Espinosa, 2000:synonym of ''Janolus comis'' Er. Marcus, 1955 * ''Janolus cristatus'' (Delle Chiaje, 1841):synonym of '' Antiopella cristata'' (Delle Chiaje, 1841) * ''Janolus flagellatus'' Eliot, 1906:synonym of Janolus hyalinus (Alder & Hancock, 1854) (dubious synonym) * ''Janolus fuscus'' O'Donoghue, 1924:synonym of '' Antiopella fusca'' (O'Donoghue, 1924) (original combination) * ''Janolus longidentatus'' Gosliner, 1981:synonym of '' Antiopella longidentata'' (Gosliner, 1981) (original combination) * ''Janolus nakaza'' (Gosliner, 1981):synonym of '' Bonisa nakaza'' Gosliner, 1981 * ''Janolus novozealandicus'' (Eliot, 1907):synonym of '' Antiopella novozealandica'' Eliot, 1907 * ''Janolus praeclarus'' (Bouchet, 1975):synonym of '' Antiopella praeclara'' Bouchet, 1975

References

{{Taxonbar, from=Q3020001 Nudibranchia