In the coastal waters of Northern Europe, we find several species of sea pens. Best known are the “large sea pen” (Funiculina quadrangularis) and the “slender sea pen” (Virgularia mirabilis).
The Funiculina quadrangularis occurs down to a depth of more than 8,500 feet and can reach a size of more than 51/2 feet in height, while Virgularia mirabilis reaches a height of about 2 feet and occurs shallower, with a maximum depth occurrence of more than 1,100 feet. The latter species is also known from the Mediterranean.
Off the coast of Norway, sea pens normally occur in depths greater than accessible to most divers. However, in the fjords of western Norway, much of the deep-water fauna naturally occurring on the continental shelf are also found inside the fjords in relatively shallow water. This is also true for the sea pens. Consequently, divers have been able to study the sea pens up close and have reported on interesting reproductive behavior; the sea pens seem to release their gametes simultaneously and synchronously to the full moon. This behavior is very similar to that reported from coral reefs of the Central Pacific, where stony corals (and other invertebrates) are know to mass-spawn synchronously.
Another common species from the northern Atlantic is the cosmopolitan Pennatula phosphorea. This species is deep red in color and not very big, reaching a maximum size of about 91/2 inches. Like the other two mentioned species, P. phosphorea naturally occurs in deeper water, but even this species is found in relatively shallow water in the fjords of western Norway.