How to recognize an Acartia male:

Using a binocular :

Top of the head quite flat or slightly triangular.

Prosome with a typical slender shape and 4 visible thoracic segments.

A1 shorter than the prosome, with many quite long and spaced setae.

Urosome 5-segmented.

Furca rather short (approximativelly as long as one urosome segment).

Furcal setae rather robust with a typical fan shape.

Using a microscope :

No rostrum.

P5 asymmetrical, uniramous and forming a claw.

How to differenciate A. clausi from other Acartia

Using a binocular :

Corners of the last thoracic segment rounded, without spine.

Small P5.

Using a microscope :

Right part of P5 ending with 2 short spines.

Second and third segment of left P5 with a bump (see figures).

 

Ecological Notes :

Very common. Very abundant in shallow waters.