Technical key

1 Total body length greater than 2 mm.....Calanus pacificus

1' Total body length less than 2 mm.....2


2 (1') Posterior corners of prosome produced as rounded spines, urosome asymmetrical.....Tortanus discaudatus

2' Posterior corners of prosome not angular or produced as spines; urosome of three segments......3


3 (2') Last segment of metasome rounded, with 3-5 marginal spinules.....Acartia clausi

3' Urosome of four segments......4


4 (3') Total body length less than 1 mm.....Microcananus pygmaeus pusillus

4' Total body length greater than 1 mm.....5


5 (4')Reduced 5th leg present and urosome relatively thick......Paracalanus parvus

5' 5th leg not present.....6


6 (5')Genital segment swollen.....Pseudocalanus minutus

6' 1st antennae longer than the body.....Sinocalanus brevicaudatus


7 Urosome of 5 segments or more with 5th leg on 1 segment of urosome and short 1st antennae.....Oncaea borealis

Page author: Matthew P. Kweskin