Tritonia hombergii

Tritonia hombergii Cuvier, 1803

• Sphaerostoma jamesonii MacGillivray, 1843
• Sphaerostoma jamiesoni MacGillivray, 1843 
• Tritonia alba Alder & Hancock, 1854 
• Tritonia atrofusca MacGillivray, 1843 
• Tritonia conifera Dalyell, 1853 
• Tritonia divaricata Dalyell, 1853 
• Tritonia hombergi [sic] 
• Tritonia pustulosa Deshayes, 1853

Description
It is a large nudibranch as it can reach 20 cm in length. Its color varies from whitish to purplish brown or orange, depending on the size of the animal and its feeding, The whole body has rounded tubercles of various sizes. The frontal veil is bilobed and each lobe has numerous short fingerings. The rhinophores have digitiform extensions in their upper area and their base is surrounded by an elevated rhinophoric sheath with a widened and slightly scalloped upper edge. On the margin of the back there are 5-6 large gill branches directed upwards and smaller ones interspersed between them and projecting laterally. The foot is wide and whitish.

Biology
It lives at a certain depth, in Alcyonacean colonies. In the Atlantic coasts it feeds on Alcyonium digitatum and in the Mediterranean possibly Alcyonium palmatum. The spawn is a scalloped spirally wound cord with pink eggs of about 200 microns. When disturbed it produces a defensive secretion capable of irritating the human skin.

Etymology

• Tritonia. The genus Tritonia is dedicated to Triton, in Greek mythology the god of the sea, son of Poseidon and Amphitrite, portrayed as having the head and trunk of a man and the tail of a fish.
• Hombergii. Probably in honor of the German-Dutch-French chemist Wilhelm (Guillome) Homberg (1652-1715), because he is the only person known to have been active within natural history, possibly collected creatures when visiting relatives in Normandie.

Distribution
It is a frequent species in northern Europe, from the Faroe Islands, Norway and the British Isles, where it is very common. It is also known from the Iberian Peninsula and in the western Mediterranean, where it is considered rare. In Catalonia it has only been observed in the commercial trawling grounds off Blanes and Vilanova i la Geltrú. The recent description of Marionia gemmii has shown that it has been historically confused with Tritonia hombergii, so all previous reports of this species should be re-evaluated and clarified. Specifically, the report of T. hombergii by Rolán et al. (1991) in the Ría de Vigo could be M. gemmii due to its identical radular morphology. Similarly, the Andalusian report of T. hombergii by García-Gómez (1982) could also belong to M. gemmii. The other Iberian reports of T. hombergii (Hidalgo 1916; Ros 1975) are a simple name in a list and have no description, so the entire distribution range of this species would have to be reviewed, especially in the Mediterranean.

Known georeferenced records of the species: Tritonia hombergii

Sources:
OBIS GROC 2010-2011 Enric Madrenas João Pedro Silva Bernard Picton GBIF	OPK VIMAR Manuel Ballesteros M@re Nostrum Altres fonts Marine Regions

Similar species
Marionia gemmii, an Atlantic species described in 2018 in Galicia, with the mantle with a characteristic dorsal reticulated pattern and without dorsal tubercles, and with fewer papillae on the oral veil.

Videos

Tritonia hombergii mating in Lochcarron, Scotland 23/04/2018
Video by Chris Rickard (from NE Atlantic Nudibranchs forum @ Facebook)

More pictures

Tritonia hombergii

Tritonia hombergii Juvenile 25mm long. Lee’s Wreck, Strangford Lough, Northern Ireland. 5 Aug 2008. – Photograph ©Bernard Picton

Tritonia hombergii – Photograph ©Bernard Picton

Tritonia hombergii 48mm @ Rubh an Dunain, Skye, Scotland in 15 m by Jim Anderson

Tritonia hombergi by José Carlos García Gómez

Tritonia hombergii @ Inner Forth estuary, Scotland 20150628 by Matt Barnes (NE Atlantic Nudibranchs)

Tritonia hombergii @ Norway by Viktor Vasskog Grøtan

Tritonia hombergii feeding @ Norway by Viktor Vasskog Grøtan

Tritonia hombergii spawning @ Norway by Viktor Vasskog Grøtan

Tritonia hombergii @ Spain by Manuel Ballesteros

Bibliography

1246567 Tritonia hombergii 1 eunomia-revista-en-cultura-de-la-legalidad 50 creator asc 1 10731 https://opistobranquis.info/wp-content/plugins/zotpress/
Bibliography based on the works by Steve Long, 2006. Bibliography of Opisthobranchia 1554-2000 and Gary McDonald, 2009. Bibliographia Nudibranchia, with later updates from other resources.

Further reading

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