black sea red data book - Department of Biology

Branchiostoma lanceolatum Pallas, 1774
Synonyms: Amphioxus lanceolatus Pallas, 1744
Common names: Engl: Amphioxus, Lancelet; Bulg: Lantsetnik, Russ: Lantsetnik,
Ukr: Lantsetnyk
Order AMPHIOXI
Family BRANCHIOSTOMIDAE
Taxonomic description. The Amphioxus belongs to the chordates. It does not have
a spine, but, by possessing a notochord, it ranks only just below the vertebrates. The
chorda is well differentiated and runs along the whole body. The body is segmented,
dorso-ventrally flattened, spindle-shaped, and pointed at both ends. Colour pink,
body semi-transparent. A membranaceous flipper along the dorsal side. The caudal
end of the body has a lance-like flipper, where the name of the animal originates
from. Cranium, head and central nervous system not differentiated. There is no heart,
but pulsating blood vessels instead. The length of the body reaches usually 3-5 cm,
rarely 8 cm.
IUCN Status
World level:
Black Sea Regional level:
Subregion level: VU
Distribution, Habitat type, Critical habitats, Limiting factors. Amphioxus inhabits
the sandy sublittoral at depths down to 28-30 m. It is accompanied by some specific
Polychaeta species (e.g. Staurocephalus keffersteini) in a biocoenoses called
Amphioxus sands. It prefers sand mixed with shells. It is very rare on muddy bottoms
because it is not adapted to life on bottoms with fine particles.
Biology. Amphioxus feeds on microalgae, infusoria, crustaceans, etc. Its behaviour
differs according to bottom structure. In coarse sand, where water is rich in oxygen
and food particles circulate freely, it buries itself entirely. In fine sand, only half of
the body is buried, the other half emerges from the bottom. In muddy grounds it does
not bury itself at all because it can neither feed nor breathe there. The animal is more
active during the night. It reproduces during summer and lives for three to four years.
Population trends. Muddy areas have expanded during the last decade as a result of
intensive dumping of dead organic matter. This is unfavourable for Amphioxus and
any such change in bottom structure results in a considerable decrease in its
abundance. In the 1960s, it was common along the Bulgarian coast, with the highest
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