Page 94 - Invasive_Species_2013

Mediterranean invasive species factsheet

ASCIDIANS

Reproduction Common name: Sea squirt

identification

Scientific Name:
Microcosmus squamiger
Picture

Key identifying features
Brief history
Microcosmus squamiger is a solitary (non-colonial)
ascidian up to 4 cm in height which looks like a
globular tube with two short openings (siphons) on
the top. It attaches to a hard substrate by a stalk.
When the individuals are contracted (as when
touched) the siphons are hidden. The body surface
(tunic) is wrinkled, leathery brown or reddish, often
with other organisms (such as algae) growing or
encrusted on its surface. Internally, the tunic is softer
and purple in colour.
Field identification signs and habitat

Microcosmus squamiger occurs in the Mediterranean
Sea in shallow littoral rocky habitats, particularly
reproduces in summer and fertilized eggs develop
inside marinas, harbours and aquaculture facilities,
normally at 20–25 °C in a relatively short period of
where it forms dense aggregations that can reach
time. Old ascidians seem to die afterwards, to be
more than 2,000 individuals per square metre. It can
replaced by new individuals the following winter.
also spread locally and colonize nearby natural rocky
habitats.

Reproduction
Microcosmus squamiger is a simultaneous
hermaphrodite, capable of producing and releasing
both sperm and eggs almost at the same time. It

Microcosmus squamiger covered with algae and sediments.
Microcosmus squamiger. Photo: C. Griffiths and M. Rius Photo: B. Weitzmann

Monitoring Marine Invasive Species in Mediterranean MPAs: A strategy and practical guide for managers 91