Table 1 Comparison of characteristics among the Oithona species occurring in the North Sea and O. davisae

Total length (mm)

0.68–0.96

0.5–0.65

1.18–1.28

1.14–1.43

0.54–0.62

P:U

1.1–1.4

1.0–1.2

1.0–1.2

1.1–1.3

1.2

Rostrum

Curved, short, and pointed

No

Not curved, pointed, dorsally visible

Not curved, pointed, dorsally visible

Curved, strong, and ventrally pointed

Caudal rami L:W

1.9–2.4

2.1–2.7

3.0–3.7

3.1–3.8

3.0

Mx1 Li1 distal most spine

Short

Short

Short

Short

Longer than other setae

Mx1 End no. of setae

1 min seta

1 seta

1 min seta or lacking

1 long seta

1 seta^a

Md B2 distal spines

2 pointed spines

1 long and 1 min pointed spine

1 longer and 1 shorter pointed spine

1 longer and 1 shorter pointed spine

2 thick blunt curved spines

Outer marginal spines (Exp1, Exp2, Exp3)

 P1

1, 1, 2

1, 1, 3

1, 1, 2

1, 1, 2

1, 1, 3

 P2

1, 0, 1

1, 1, 3

1, 0, 2

1, 0, 2

1, 1, 3

 P3

1, 0, 1

1, 1, 3

1, 0, 1

1, 0, 1

1, 1, 3

 P4

0, 0, 1

1, 1, 2

0, 0, 1

0, 0, 1

1, 1, 2

References

Nishida (1985)

Nishida (1985)

Nishida (1985)

Nishida (1985)

Ferrari and Orsi (1984)