Overview

Comprehensive Description

Description

 Janolus cristatus is a semi-transparent nudibranch growing to at least 7.5 cm. The body is oval and flattened. There are numerous swollen cerata, each with a central thin dark thread of digestive gland. The cerata tips contain an irridescent bluish-white pigment. Similar patches of pigment are found on the back, between the cerata and in the head region. The lamellate rhinophores are especially large and conspicuous, non-retractile and without sheaths. A coarsely ridged, sensory cocks comb-like structure called a caruncle lies between the rhinophores, which is unique to Janolus species.Spawning has been recorded from April to September and in December (Thompson & Brown, 1984). The egg-mass contains a series of bead-like white or pale pink ovoids, each being a capsule containing up tp 250 separate individual spherical eggs (ova). The spawn is wound in a wavy circle pattern (Thompson & Brown, 1984).
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Description

A semi-transparent nudibranch with numerous swollen cerata, each with a thin dark thread of digestive gland running through the centre. The tips of the cerata are coloured with an iridescent bluish-white pigment, and similar pigment patches are found on the back, between the cerata and in the head region. The rhinophores have lamellae set at an angle, giving the appearance of spiral grooves. Between them is a cockscomb-like structure called a caruncle which is unique to Janolus species. A large species, growing to at least 75mm.
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Source: Encyclopedia of Marine Life of Britain and Ireland

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Distribution

A common species in moderate depths around most of the British Isles. Recorded from Norway to the Mediterranean.
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Ecology

Habitat

Depth range based on 122 specimens in 1 taxon.
Water temperature and chemistry ranges based on 7 samples.

Environmental ranges
  Depth range (m): 0 - 41
  Temperature range (°C): 10.422 - 11.721
  Nitrate (umol/L): 4.909 - 7.251
  Salinity (PPS): 34.243 - 35.333
  Oxygen (ml/l): 6.095 - 6.218
  Phosphate (umol/l): 0.399 - 0.598
  Silicate (umol/l): 2.311 - 4.820

Graphical representation

Depth range (m): 0 - 41

Temperature range (°C): 10.422 - 11.721

Nitrate (umol/L): 4.909 - 7.251

Salinity (PPS): 34.243 - 35.333

Oxygen (ml/l): 6.095 - 6.218

Phosphate (umol/l): 0.399 - 0.598

Silicate (umol/l): 2.311 - 4.820
 
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 Janolus cristatus lives in shallow sublittoral conditions, especially on sheltered rocky coasts. They feed on erect tufted bryozoans such as Bugula and Cellaria species.
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Found in shallow sublittoral conditions, especially on sheltered rockfaces. It feeds on erect Bryozoans, especially Bugula species. The spawn consists of a white or pale pink string wound in a wavy circle pattern, usually on the food. The eggs are in packets with clear patches between them, giving a beaded appearance to the spawn.
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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage: Janolus cristatus

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 1
Species With Barcodes: 1
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Wikipedia

Janolus cristatus

Janolus cristatus is a species of nudibranch, a marine gastropod mollusk in the family Proctonotidae.[1]

Description[edit]

This 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.[2]

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.[3]

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.[2]

Distribution[edit]

Janolus cristatus has been found as far north as Norway down through the British Isles and the French Atlantic coast.[2] It has also been recorded in Moroccan waters as well as in the Mediterranean Sea.[3]

Habitat[edit]

Janolus cristatus depositing eggs

Janolus cristatus eats erect bryozoan in the Bugula genus, such as B. turbinata, B. plumosa, and possibly species in the Cellaria genus.[3] It is found at depths of up to 40 metres, only in calm, clean water, on hard substrata in the sublittoral zone.[2]

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.[3]

References[edit]

  1. ^ "WoRMS - World Register of Marine Species - Janolus cristatus (Delle Chiaje, 1841)". Marinespecies.org. 2004-12-21. Retrieved 2014-05-24. 
  2. ^ a b c d "Marine Species Identification Portal : Janolus cristatus". Species-identification.org. Retrieved 2014-05-24. 
  3. ^ a b c d "Janolus cristatus - Marine Life Encyclopedia". Habitas.org.uk. Retrieved 2014-05-24. 
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