Hermaea bifida

Hermaea bifida (Montagu, 1815)

Hermaea bifida @ Oosterschelde, Netherlands by Stefan Verheyen




































Hermaea bifida  (Montagu, 1816)

 Classification according to Bouchet et al. (2017)
Taxonomic source: World Register of Marine Species (AphiaID: 140092).

  • Doris bifida Montagu, 1815 (original)
  • Hermaea hancockii Trinchese, 1877
  • Physopneumon carneum A. Costa, 1864
  • Physopneumon corneus Costa A., 1864

This species can reach a size of more than 20 mm but specimens generally found on seaweeds measure just a few millimeters. The body is narrow, elongated, with a semitransparent and slightly yellowish-green hue. Cerebral ganglia, some reproductive and digestive organs, such as the buccal bulb and the esophagus, can be seen by transparency, for instance, two reddish-brown or brown lines, corresponding to the digestive gland can be seen, one on each side of the back, passing very close to the base of the cerata and reaching almost the end of the queue. The head is very short and with two rounded lobes at its anterior margin. The rhinophores are located well ahead of the body and are auriculate, open at its outer side, semitransparent and decorated with white granulations on the tip, in their middle and between the two insertion points into the head. The tip of the rhinophres shows two lobulations, a longer dorsal one and a ventral somewhat shorter one. The cerata are semitransparent and can be extended or contracted a lot, becoming long and slender when the animal is in motion but short and thick when the animal is at rest. The cerata, when fully extended are thin at the base and go wider until near the apex, where there is a conical tubercule on the apex and several subapical tubercules (up to 4-5). In small specimens of about 4-5 mm, the cerata are inserted into the body single or in pairs, and are often of very different sizes. In larger specimens there can be up to 9-10 groups of 2-3 cerata on each side of the body. Within cerata, digestive gland is seen as a narrow, longitudinal, straight and brown cord having perpendicular leads which are directed toward the tip of the tubercules. There could be translucent white granulations on the cerata surface, especially at the tip of the tubercules. The anal papilla is located directly in front of the heart area and is short and shaped conical, having white granulations near its base. The genitalia orifices are located at the right side of the body, between the base of the rhinophore and the insertion of the first cerata. The foot is relatively narrow, colored greenish-yellow and has two rounded lobes at the front side; may show whitish granulations on the foot margins.

This sacoglossan species lives in shallow places among Rhodophyceae algae such as Griffithsia flosculosa, of which apparently it feeds on and acquires the algae rhodoplasts that confer the reddish-brown color to the digestive gland of the animal. It has been collected in shallow water (2-3 m) among Rhodophyceae algae of the genus Lophosiphonia. The spawn is a flat spiral ribbon of about 5 mm in diameter, with white eggs measuring 50 microns in diameter. It can easily be confused with Hermaea cantabra, but they are distinguished by the longitudinal stripes in the head and along the rhinophores, present in Hermaea cantabra and absent Hermaea bifida.


  • Hermaea. Derived from Hermes, character in Greek mythology.
  • Bifida. From Latin bifidatus, divided in two.

This species is known in Atlantic waters, around the British Isles, in the Strait of Skagerrak (separating Norway from Denmark), in the Iberian Peninsula and in the western Mediterranean. It has also been cited in the Caribbean Sea. In the Iberian Peninsula it has been cited in Galicia, all along the Portuguese coast, in the Atlantic coast of Andalusia, in the Strait of Gibraltar, the southeastern coast and, in the Catalan coast, in several locations of the Costa Brava like Cadaqués, Cala Aiguafreda (Begur), Cala Margarida (Palamos) and Tossa de Mar. Existing reports of this species should be revised because they could correspond to misidentified Hermaea cantabra specimens.

Known georeferenced records of the species: Hermaea bifida
: GROC 2010-2011
: Enric Madrenas
: João Pedro Silva
: Bernard Picton
: Manuel Ballesteros.
: M@re Nostrum
: Altres fonts
: Marine Regions


    Western Mediterranean: ★★☆☆☆
    Eastern Mediterranean: ☆☆☆☆☆
    Atlantic Ocean: ★★☆☆☆

This chart displays the monthly observation probability for Hermaea bifida based on our own records.



More pictures


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    Ballesteros, M. 2007. Lista actualizada de los opistobranquios (Mollusca: Gastropoda: Opisthobranchia) de las costas catalanas. Spira. 2: 163–188.
    Ballesteros, M., E. Madrenas, and M. Pontes. 2016. Actualización del catálogo de los moluscos opistobranquios (Gastropoda: Heterobranchia) de las costas catalanas. Spira. 6: 1–28.
    Ballesteros, M., E. Madrenas, and M. Pontes. 2023. OPK - Opistobranquis. (https://opistobranquis.info/).
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    Riedl, R. 1983. Fauna und Flora der Mittelmeeres, ein systematischer Meeresfuhrer fur Biologen und Naturfreunde, 836 pp. Paul Parey, Hamburg & Berlin.
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    Taylor, D. L. 1971. Symbiosis between the chloroplasts of Griffithsia flosculosa (Rhodophyta) and Hermaea bifida (Gastropoda: Opisthobranchia). Pubbl. Staz. Zool. Napoli 39:116-120.
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    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

Cite this article as:

Ballesteros, M., Madrenas, E. & Pontes, M. (2023) "Hermaea bifida" in OPK-Opistobranquis. Published: 14/05/2012. Accessed: 28/02/2024. Available at (https://opistobranquis.info/en/?p=266)

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