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Lohmann, 1896

Description
Trunk long and narrow, post-anally drawn out to give place to the ovary and testis. Gill opening small and round; endostyle short and broad at the frontal side. Upper lip long, truncate.
Tail attached to trunk at mid-ventral side; tail short, with a broad fin and without particular gland cells. There are two forms (or subspecies) considered for the British waters (Fraser, 1981):
F. borealis acuta Lohmann and Bückmann, 1926. This is a cosmopolitan cold water form from the Arctic and subpolar waters. The tip of the tail musculature is pointed and the end of the tail fin is rather square cut.
F. borealis truncata Lohmann and Bückmann, 1926. This is a warm water form. The tip of the tail musculature is pointed and the tail fin is distinctly bifurcated.

Remark
By the form and relative position of ovaries and testes, as well as by variations in the tail, Lohmann recognised two subspecies with together seven forms for F. borealis (Lohmann, 1931). Later it was demonstrated that these forms are continuous variations (Tokioka, 1960). The subspecies were cancelled and the species was split in three forms by Tokioka, using names originally given by Lohman: F. borealis f. typica Lohman, 1900 (belonged to the "cold water" subspecies acuta ), F. borealis f. sargassi Lohman, 1900, and F. borealis f. intermedia Lohman, 1905 (both belonging to the "warm water" subspecies truncata ). The North Sea is the type locality of Lohmann's F. borealis f. intermedia. These three forms are still considered as valid for this species in the recent classification of appendicularians (Fenaux, 1998).

Size
The length of the trunk is 1.3 mm in the cold water form F. borealis acuta and maximal 0.9 in the warm water form F. borealis truncata.

Depth range
Epipelagic.

Distribution in the North Sea
Whole North Sea. The species is also known from brackish waters; the cold water form is also known from the inshore Wadden Sea. F. borealis is a characteristic species in the Dutch coastal waters (Wyatt, 1973).

World distribution
F. borealis typica : Atlantic, Pacific, Arctic and Antarctic Oceans, bipolar division.
F. borealis intermedia : Atlantic, Pacific and Indian Oceans, Red Sea, Mediterranean Sea.
F. borealis sargassi : Atlantic, Pacific and Indian Oceans, Red Sea, Mediterranean Sea.

Fritillaria borealis