Janolus cristatus

Janolus cristatus, sometimes known by the common name crested aeolis, is a species of nudibranch, a marine gastropod mollusc in the family Proctonotidae.[1]

Janolus cristatus
Janolus cristatus, head end towards the top of the image
Scientific classification
Kingdom:
Animalia
Phylum:
Mollusca
Class:
Gastropoda
(unranked):
clade Heterobranchia
clade Euthyneura
clade Nudipleura
clade Nudibranchia
clade Dexiarchia
clade Cladobranchia
Family:
Proctonotidae
Genus:
Janolus
Species:
J. cristatus
Binomial name
Janolus cristatus
(Delle Chiaje, 1841)
Synonyms

Antiopa splendida Alder & Hancock, 1848

  • Antiopella cristata (Chiaje, 1841)
  • Eolidia cristata Delle Chiaje, 1841
  • Eolis cristata Delle Chiaje, 1841
  • Janus spinolae Vérany, 1846

Taxonomy

Some authors assign the genus Janolus to the Janolidae family (see ITIS.gov[2] or AnimalDiversity[3]), other (see Seaslug[4]) to the family of Zephyrinidae, that are synonymised names of Proctonotidae' (see WoRMS).[5]

Description

This rare species is semi-transparent and has an oval-shaped outline. It is cream or light brown in colour, and grows to approximately 7.5 cm in length. The head has oral tentacles that are short.[6]

The lateral cerata are numerous, have a smooth surface and an inflated appearance. The central digestive gland lobe is thin and brown in colour and can be seen through each ceras. These gland lobes divide at the tip of the cerata into numerous terminal branches. The tips of the cerata are bluish-white and iridescent.[7]

This white colouration that is present on the cerata also appears in patches or lines along the bare central dorsum, as well as around the lamellate rhinophores and on the metapodium. The rhinophores are joined together at their bases with a swollen and wrinkled accessory caruncle. Both the rhinophores and median sensory caruncle are somewhat darker in colour than the rest of the body.[6]

Distribution

Janolus cristatus has been found as far north as Norway down through the British Isles and the French Atlantic coast.[6] It has also been recorded in Moroccan waters as well as in the western Mediterranean Sea.[7][8]

Habitat

It is found at depths of up to 40 metres, only in calm, clean water, on hard substrata in the sublittoral zone.[6]

Biology

Janolus cristatus eats erect bryozoan of the species Alcyonidium gelatinosum, Bicellariella ciliata and in the genus Bugula, such as B. turbinata, B. plumosa, B. neritina and possibly species in the genus Cellaria.[7]

The spawn of this species appear as a light pink or white string forming a wavy, circular pattern. The eggs themselves are contained within packets with transparent patches in between. This gives them the appearance of beads.[7]

Bibliography
  • Gary R. McDonald Nudibranch Systematic Index (2nd ed.), University of California Santa Cruz University of California Santa Cruz in Institute of Marine Sciences, (2009).
  • Gary R. McDonald, James W. Nybakken, A List of the Worldwide Food Habits of Nudibranchs, in University of California Santa Cruz.
  • R. Cattaneo-Vietti, R. Chemello et R. Gianuzzi-Savelli, Atlas of Mediterranean nudibranchs, Roma, Editrice La Conchiglia, 1990, 264 p. (OCLC 26035712, LCCN 93155161)
  • Thomas E. Thompson et G.H. Brown, Biology of Opisthobranch Molluscs : The standard work on British nudibranchs, with up to date information and colour paintings of nearly all species, vol. 2, Ray Society, 1984 (ISBN 0903874180)
  • Delle Chiaje, S. (1841). Descrizione e notomia degli animali invertebrati della Sicilia citeriore osservati vivi negli anni 1822-1830, Napoli, 7: pls. 86-173 (Nudibranchia pls. 88, 89, 100, 106, 178). Text in vol. 8, p. 6 (1844)
  • Egidio Trainito, Nudibranchi del Mediterraneo. Guida al riconoscimento dei molluschi opistobranchi, 2005ª ed., Milano, Il Castello, 2005, ISBN 88-8039-438-X.
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References
  1. "WoRMS - World Register of Marine Species - Janolus cristatus (Delle Chiaje, 1841)". Marinespecies.org. 2004-12-21. Retrieved 2014-05-24.
  2. IT IS Report
  3. IT IS Report Animal Diversity
  4. The Sea Slug Forum Australian Museum
  5. Proctonotidae at WoRMS
  6. "Marine Species Identification Portal : Janolus cristatus". Species-identification.org. Retrieved 2014-05-24.
  7. "Janolus cristatus - Marine Life Encyclopedia". Habitas.org.uk. Retrieved 2014-05-24.
  8. Thomas E. Thompson, Molluscs: Benthic opisthobranchs, Leiden, Brill, coll. « Synopses of the British Fauna » (no 8), 1988 (ISBN 9004084398)
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