Akera bullata

Akera bullata O. F. Müller, 1776

Akera bullata (blue) @ Etang de Thau, France by Pascal Girard




































Akera bullata  O. F. Müller, 1776

 Classification according to Bouchet et al. (2017)
Taxonomic source: World Register of Marine Species (AphiaID: 138734).

  • Acera bullata (Müller O.F., 1776)
  • Acera bullata var. nana Jeffreys, 1867
  • Acera elegans Locard, 1886
  • Aceras elegans Locard, 1886
  • Akera flexilis Brown, 1844
  • Bulla akera Gmelin, 1791
  • Bulla elastica Danilo & Sandri, 1856
  • Bulla farrani Norman, 1890
  • Bulla fragilis Lamarck, 1822
  • Bulla hanleyi Adams A. in Sowerby G.B. II, 1850
  • Bulla norwegica Bruguière, 1792
  • Bulla resiliens Donovan, 1801
  • Eucampe donovani Leach, 1847

With a maximum reported length of about 60 mm, it has an elongated body provided with two large parapodial lobes. Body is coloured pale grey to orange, often streaked anteriorly with blotchy lines of purplish-brown, covered with white and dark spots. The head is indented in the front part, somewhat expanded laterally to form flattened tentacular lobes. The eyes are located in the periphery of the head. The shell is large, up to 40 mm, bubble-like, fragile, glossy, up to six characteristic whorls forming a rather flat spire. The shell cannot contain the entire body of the animal and it is visible from its rear side. The mantle ends at the back with a thin and long appendage which protrudes from the shell.

Classified as a primitive Anaspidea, it has a life form resemblant to Cephalaspidea, as the front of the animal’s body is intended for digging and, in fact, this sea slug spends most of its life buried in mud or silt, only coming out during the breeding season. During mating season (March and April in the Mediterranean) these animals can be found forming long chains of individuals crawling the sea bottom. The egg spawn is formed by a tangled light yellow cord, similar to the spawn of sea hares but thinner, less bulky and lighter in color. The large parapodial lobes cover the lateral and dorsal areas of shell when the animal is at rest, but they are used for evasive swimming action when disturbed. When it swims, due to its bulky shell, it does so in a very particular way, with the head up, the shell down and the parapodia forming a moving “skirt” around the animal. It feeds on algae, as do other sea hares.


  • Akera, god from Egyptian mythology, symbol of the earth and more particularly of the underground life. Originally represented by a piece of earth with a human head, later representations show two opposite man heads or two opposite lion heads. It could also be from Greek [Ker] = horn and [a] privative: could also mean that has no body processes as most other sea hares do.
  • Bullata, from Latin “Bullatus”, meaning “inflated”, “water-bubble like”, “empty”, in reference to its shell.

It is present in NE Atlantic waters, from Norway to the Canary Islands, Madeira and Azores, also along the Mediterranean Sea. Present in all Iberian waters. In Catalonia it has been found in the Bay of Roses, and in the Ebro Delta.

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

References for the species: Akera bullata

    Cantabria: Hidalgo (1917), Ortea (1975-76, 1977c), Lastra et al. (1988), Ávila Escartín (1993), Martínez Cueto-Felgueroso (1995). Galicia: Hidalgo (1917), Cadee (1968), Hernández and Jiménez (1972), Rolán (1983), Urgorri and Besteiro (1983). Portugal: De Oliveira (1895), Hidalgo (1917), Nobre (1936), Machado and Fonseca (1997). Andalucía (Med.): Moreno and Templado (1998). Levante: Templado, Talavera and Murillo (1983), Olmo and Ros (1984). Catalunya: Altimira (1977b), Ballesteros (1983). Baleares: Ballesteros and Templado (1996). Canarias: Ortea et al. (2001), Moro et al. (2003). Madeira: Watson (1897, as Acera bullata), Nobre (1937, as Acera bullata), Ledoyer (1967, as Acera bullata). Azores: Nobre (1924), Ávila (2000), Malaquias (2001).

    Sources: Cervera et al., 2004, Ballesteros, 2007 & 2016, McDonald, 2006 and other sources.

Similar species
This species closely resembles many species of the genus Haminoea, both are physically similar and live in a similar substrate, but Akera has a more elongated body, with far larger parapodia, and egg size and shape are fundamentally different from those of Haminoea. Also the shell of Akera has 6 turns, while Haminoea has far less turns. The eyes of Haminoea are located close to the center of the head, while in Akera they are on the periphery of the body. Differentiation is often difficult because literature is scarce.


    Western Mediterranean:1 out of 5 stars
    Eastern Mediterranean:1 out of 5 stars
    Atlantic Ocean:2 out of 5 stars

This chart displays the monthly observation probability for Akera bullata based on our own records.



More pictures


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Further reading

Cite this article as:

Pontes, Miquel, Manuel Ballesteros, Enric Madrenas (2021) "Akera bullata" in OPK-Opistobranquis. Published: 13/08/2014. Accessed: 11/04/2021. Available at (https://opistobranquis.info/en/DFZi1)

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