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(Risso, 1816)

Description
Larval morphology changing with developmental stage; larval development encompasses six megalopal (or erichtus) stages. A good description was not available from literature. Giesbrecht, 1910 provides an extended description and illustrations of the subsequent stages and a comparison with the similar stages of Rissoides desmaresti. The medio ventra-spine on the antennular segment is present from stage 3-4 onwards (TL 3.6-3.9 mm), whereas in R. desmaresti this spine appears already in the first stage (TL 3.6-4.1 mm). The ventero-distal spines on abdominal pleurae appear in the eighth stage (TL 13 mm); in R. desmaresti these spines are present from the first stage onwards.

Size
Total larval body length 3.6-14.5 mm.

Depth range/habitat
Larvae: planktonic, shallow.
Adult: benthic, subtidally to about 40 metres.

Distribution in the North Sea
In the North Sea, it is restricted to the southern part, entering the area from the Channel.

World distribution
Adults occur in the Mediterranean, on the Atlantic coasts of Portugal, France, southern coasts of the British Isles. Larvae have a more widespread distribution, in our area also occurring in the southern North Sea, entering from the Channel.

Platysquilla eusebia