Two creeping Ceramium species (Ceramiaceae, Rhodophyta) from the Florida Keys:: C reptans sp nov and recircumscription of C codii (Richards) Mazoyer

On the basis of comparative morphology, a new creeping Ceramium species with incomplete and narrow nodal cortication, C. reptans sp. nov. is described from the Florida Keys, USA, where it co-occurs epiphytically with C. codii on the same host, Hypnea spinella. Ceramium reptans sp. nov. is recognized by a prostrate axis producing unbranched upright axes dorsally; five periaxial cells per axial cell; three cortical cells cut off per periaxial cell, with the first acropetal cortical cell becoming the pseudoperiaxial cell that extends longitudinally parallel to the level of neighboring periaxial cells, a second acropetal and third basipetal horizontal cortical cell; and cruciately divided tetrasporangia in whorls bulging from a single node appressed to the contiguous node below on upright axes, 3-6 segments below the apex. Ceramium codii, described from Bermuda, is recognized by a prostrate axis producing unbranched, upright axes dorsally, four periaxial cells per axial cell, three cortical cells cut off per periaxial cell with the basipetal cortical cell cut off horizontally on the prostrate axis, and 1-2 tetrahedrally divided tetrasporangia produced per periaxial cell. Among the described creeping Ceramiaun species; C. codii, C. bisporum, C. cingulatum, C. cingulum, C. dorsiventrale, C. incospicuum, C. jolyi, C. luetzelburgii, C. procumbens, C. poeppigianum, C. punctiforme, C. serpens, and C. tenerrimum var. brevizonatum f. repens, none has the characteristic pseudoperiaxial cells of C. reptans. Ceramium codii may not be a widespread species as is widely reported in the literature.