How to recognize a Paracalanus female:

Using a binocular :

Prosome with a regular ovoid shape.

Rostrum with two points.

A1 longer than prosome

3 visible thoracic segments.

Urosome 4-segmented.

Furca length similar to anal segment length

Using a microscope :

Exopodites of P3 and P4 with serrated outside margin.

Tiny, uniramous, symmetrical, 2-segmented P5 carrying a short and a long terminal spine (one leg is sometime 3-segmented).

Anal segment with a prominence in lateral view on the dorsal posterior margin.

How to differenciate P. parvus from other Paracalanus

Using a binocular :

A1 shorter than body (but longer than prosome).

Head as wide as thorax.

Using a microscope :

P5 first segment rounded.

P5 second segment as long as the first segment.

No spines on the dorsal posterior margin of the genital segment.

Ecological Notes :

Very common.