Simocephalus vetulus


Subphylum: Crustacea – Crustaceans

Order: Diplostraca

Family: Daphniidae: Water Fleas

Scientific Name: Simocephalus vetulus (O. F. Müller, 1776)


Length: 1.1-3.8 mm.

This rather peculiar, microscopic organism is actually a crustacean, which also includes crabs and lobsters. Simocephalus vetulus has a compartively small head with an elongated eyespot. Compared to other similar species it is the more transparent of them.

Simocephalus vetulus
Simocephalus vetulus, local canal, South Staffordshire, 13th July 2020. © Peter Hillman


It feeds by filtering small phytoplankton (microscopic marine algae) species from the surrounding water.


It is found in freshwater environments like small ponds, ditches, and canals. It is known as an early colonist of newly constructed ponds, or after disturbances in established water bodies.

Distribution & Status

It appears to be common and widsepread in England and Wales, being scarcer further north.