Sporolithon mesophoticum sp. nov. (Sporolithales, Rhodophyta) from Plantagenet Bank off Bermuda at a depth of 178 m

Abstract

A coralline rhodolith was collected from a depth of 178 m, the lower end of the mesophotic zone, on Plantagenet Bank offshore of Bermuda by the submersible Nomad using a mechanical armature. DNA sequence comparisons of the plastid encoded psbA and rbcL loci of this specimen to Sporolithales from the tropical western Atlantic and worldwide revealed it to be an unnamed species of Sporolithon. Sporolithon mesophoticum sp. nov. possesses tetrasporangial sori flush to slightly raised above the thallus surface and has uniquely flattened perithallial and meristematic cells. Thus far, the new species is the deepest known living marine macroalga that has been sequenced and placed into a phylogenetic context.