Janolus

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
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.

Distribution
Janolus species are found in many areas world-wide, including Europe, Australia, Japan and Africa.

Habitat
This genus of nudibranch is found in shallow and subtidal waters.

Feeding habits
Janolus species feed on Bryozoa, moss animals.

Predators
In California, Navanax is a known predator of Janolus. Navanax tracks the slime of Janolus by using chemoreceptors. When Janolus is about to be caught, it rolls into a ball, leaving its cerata exposed.

Species
Species in the genus Janolus include:
 * Janolus anulatus Camacho-Garcia & Gosliner, 2006
 * Janolus australis Bergh, 1884
 * Janolus chilensis M.A. Fischer, Cervera & Ortea, 1997
 * Janolus comis 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 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