Binucleusphotoedo funes

Binucleusphotoedo funes developed from B. stringi that drifted farther north. B. stringi formed long strings of cells as they stayed connected after binary fission. In B. funes, cells in the middle of the string continue to split, but they attach sideways, causing the string to thicken. The string grows into a rope, which grows in the shape of a hollow tube, ever-widening.

This hollow form keeps the ropes quite light, so they float over the surface of the ocean, basking in the shallow sunlight of the northern polar sea. The shape tapers on either end, where they're still primarily growing lengthwise instead of across. Once they reach about a centimeter in length, they'll break apart, cells scattering separately, which will form new ropes.