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Borgert, 1894

Description
Gonozooid small, with a dextrally arched intestine; the anus is at the right side of the animal, at M6. The gill slits are attached dorsally behind M2, they extend backwards to M5 and turn slightly forward to the ventral attachment point just in front of M5. The endostyle begins frontal at M2 and extends to M4. The dorsal nerve ganglion is just in front of M4. The testis is variable in length, it extends horizontally on the left side of the animal (the other doliolid species in our area have testes that are either oblique or spherical).
— Nurses are barrel shaped, without visceral mass, except for a heart. Budding on the dorso-ventral processs. M2-M8 fused in a continuous sheet. Length up to 2 mm. Nurses of Doliolum nationalis and Doliolum denticulatum cannot be separated.

Size
Body length 3 mm

Depth range

Distribution in the North Sea
An oceanic species that occurs incidentally in the southern North Sea.

World distribution
North and Central Atlantic Ocean, Mediterranean Sea, Red Sea, subtropical SW Atlantic Ocean, tropical Indian and W Pacific Oceans.

Remark
D. nationalis was collected from the German Bight in October 1989 in large numbers, after a warmer summer than normal; the flourishing of this species west off the British Isles and the subsequent seeding into the North Sea is thought to be related with summer temperatures that are higher than normal (Lindley et al., 1990).

Doliolum nationalis