Bursatella leachii

Bursatella leachii (de Blainville, 1817)

Bursatella leachii @ Ebro Delta (2007) by Boris Weitzmann




































Bursatella leachii  Blainville, 1817

 Classification according to Bouchet et al. (2017)
Taxonomic source: World Register of Marine Species (AphiaID: 138759).

  • Aclesia africana Engel, 1926
  • Aclesia glauca Cheeseman, 1878
  • Aclesia rosea Engel, 1926
  • Aplysia bursatella Rang, 1834
  • Bursatella lacinulata Gould, 1852
  • Bursatella leachi [sic]
  • Notarchus (Bursatella) leachii (Blainville, 1817)
  • Notarchus intrapictus Cockerell, 1893
  • Notarchus laciniatus Rüppell & Leuckart, 1830

Although Bursatella is a monophyletic genus containing only a single species Bursatella leachii, a wide range of colors and morphological variations has induced several authors to suggest that the global distribution comprises several distinct subspecies (Eales and Engel, 1935; Bebbington 1969):

  • Bursatella leachii Blainville, 1817
  • Bursatella leachii guineensis Bebbington, 1969
  • Bursatella leachii leachii Blainville, 1817
  • Bursatella leachii pleii (Rang, 1828)
  • Bursatella leachii savigniana Audouin, 1826
  • Bursatella leachii africana (Engel, 1926) (=Bursatella leachii Blainville, 1817)
  • Bursatella leachii lacinulata Gould, 1852 (=Bursatella leachii Blainville, 1817)
  • Bursatella leachii rosea (Engel, 1926) (=Bursatella leachii Blainville, 1817)

With a maximum size of 25 cm (J.Prkić, pers.comm.), this species usually has a length of 8 to 10 cm. The body color is variable and has two different patterns, the greenish-brown dark pattern, and the greenish gray or whitish brown clear pattern. The body usually is decorated with round dark blotches and they usually have a colored spot, usually bright blue, in the middle. The body surface is covered with elongated and uneven extensions that give the body its typical appearance. The foot is wide with the head end separated in two, and a rounded rear end. The parapodia does not let it swim like other sea hares because they are fused together, leaving only a slit in the center of the dorsum that gives access to the mantle cavity. Adults lack any internal shell (Voss 1980, Kaplan 1988, Rupert and Fox 1988). In the head it has two rhinophores (olfactory tentacles) long and retractile and two oral tentacles, one on each side of the mouth.

It is normally found in shallow waters with low hydrodynamics, so it is very common in lakes and harbors. In the Mediterranean it is found in soft bottoms with algae like Caulerpa prolifera, Cymodocea nodosa and Zostera noltii, where it feeds on green algae like Lyngbya majuscula that can form thick layers in mud bottoms, or coat -as an algal film- the mentioned macro-algae . They can also feed on diatoms and occasionally on macrophytes like Ectocarpus or Enteromorpha (Paige, 1988). The spawn is a cord, with a highly variable color (orange, brown, yellow or green), formed by egg capsules that may contain between 1 and 20 eggs with a diameter of 87 micron each (Paige 1988). After hatching, the larvae become part of the plankton. The larvae probably only attach to the substrate in the presence of blue-green algae from which they can feed. Juveniles reach sexual maturity at 2-3 months of age (Paige 1988). At least in some areas this species has continued recruitment, without a clearly defined breeding season (Clarke 2004). Paige (1988) observed that embryonic development was normal at temperatures between 20 and 30ºC, but stopped at 15 ° C. The presence of Bursatella leachii in a variety of oceanic and estuarine habitats suggests that it also has some tolerance to salinity fluctuations. It has a high tolerance to low quality water, so it survives in highly polluted environments. The first specimens of Bursatella leachii found in the Mar Menor (Levante, Spain) were detected in 2008; in 2010 and 2011 there was a population bloom. There have been reported densities of up to 660 individuals per square meter (Paige, 1988), that  are probably due to optimal environmental conditions: good larvae supply, abundant food, and favorable tides, currents and weather conditions (Rudman, Sea Slug Forum). There are also episodes of mass mortality, where hundreds of thousands of specimens appear on the coast after being swept away by the waves, storms and tides after periods of extreme temperatures. Under normal conditions it is believed that this species can live a little over one year.
It is believed to be capable of sequestering secondary metabolites (like lyngbyatoxin-a with cytotoxic and antimicrobial properties) from the algae it feeds on (Capper et al., 2005), and concentrate it on a series of skin glands for its self-protection. It may expel a small cloud of purple ink when disturbed (Paige 1988). An anti-HIV protein (bursatellanin-P), has been isolated from the purple ink secretion, but it is still pending to find any feasible biomedical application related to this discovery (Rajaganapathi et al., 2002; Avila, 2006) .
Basically with a daily behavior, specimens tend to concentrate at night, scattering around every morning to feed.


  • BursatellaDerived from Latín “bursa”, bag; because of the globous shape of the body.
  • Leachii. Dedicated to Dr. William Elford Leach, (1791-1836), an English zoologyst and naturalyst characterized by his “most indomitable enthusiasm and very extraordinary acquirements”.

Its distribution range is circumtropical, living in all tropical and temperate seas between 40ºN and 40ºS (Lowe and Turner 1976). The first cite for the Mediterranean was in Israel (O’Donoghue & White, 1940) and since then it has been found in Turkey, Greece, Italy and only recently on the Mediterranean coast of France (Cagnes sur Mer, Nice, by B. Riondy, DORIS 2014) and Spain, where it has been cited in the Balearic Islands (Mallorca, Oliver & Terrasa, 2004), Levante (Alicante and Aguilas) and Catalonia. The first observation in Catalan waters (Weitzmann et al., 2007) took place in the Ebro delta, where it is well established in shallow meadows of Cymodocea nodosa and Caulerpa prolifera, and it seems that it has expanded its distribution northward with specimens detected at Vilanova i la Geltrú in 2011 and Barcelona in 2012 (Weitzmann, pers. comm.) and 2018 (Parera et al. 2020; Pontes et al. 2021). First detected in Eastern Mediterranean in 1940, it was asumed these specimens were lessepsian (of Red Sea origin), however Bazzicalupo et al (2018) demonstrated they were of Atlantic origin after performing molecular studies on Mediterranean specimens.

Known georeferenced records of the species: Bursatella leachii
: 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 Bursatella leachii based on our own records.



More pictures


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Further reading

Cite this article as:

Ballesteros, M., Madrenas, E. & Pontes, M. (2023) "Bursatella leachii" in OPK-Opistobranquis. Published: 15/05/2012. Accessed: 18/05/2024. Available at (https://opistobranquis.info/en/?p=369)

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