Slug like mollusc covered all over with simple and compound villi (papillae) of unequal size, giving it a ragged appearance. Head short and broad, with many branched median villi. Oral tentacles broad and projecting laterally. Foot broad, with a short acute tail. Parapodia short, not very mobile, their edges recurved and fused posteriorly high up, bearing a row of simple villi. A large arcuate ctenidium usually protudes through the dorsal slit.
dull brown or greenish brown, with reticulate markins, black spots and clear, brighter green areas, each with a peacok-blue ocellus (sometimes absent). Inner edges of the parapodia, mantle cavity and pedal sole paler.
common size :
usually from 50 to 100 mm, up to 150 mm.
Eales and Engel (1935) reviewed the genus Bursatella and considered that there was a single species world-wide, B. leachii, which for convenience they divided into several geographical subspecies. Here we do not recognize this sub-division and treat the Mediterranean subspecies B. leachii leachii and B. leachii savignyana as synonyms.
BIOLOGY / ECOLOGY
The population numbers of this species fluctuate sporadically. Thousands of individuals can be present in a small area of a lagoon, in very dense aggregations, but may be entirely absent a few weeks later. Individuals seem to form a chain when copulation occurs (mainly in the late summer and autumn). Each specimen acts as a male (sperm donor) to the one in front, and as a female (sperm recipient) to the one behind. The egg masses consist of a tangled string, yellow-orange in color, adhered to the substratum. Each egg capsule within the jelly matrix of the string encloses from two to 20 embryos. The planktotrophic veligers hatch 7-8 days after ovoposition (at 25 °C) and they can delay the metamorphosis up to 2-3 month, until an adequate substratum for settlement is found. This extended time of the larvae in the plankton confers a high dispersal ability to the species. From gut contents, Bursatella leachi seems to be a deposit feeder with grazing habits (Russo, 1987).
in the Mediterranean usually found in soft bottoms covered by Caulerpa prolifera or by Cymodocea nodosa and Zostera noltii.