Ramicrusta textilis sp. nov. (Peyssonneliaceae, Rhodophyta), an anatomically complex Caribbean alga that overgrows corals

Pueschel C.M. and Saunders G.W. 2009. Ramicrusta textilis sp. nov. (Peyssonneliaceae, Rhodophyta), an anatomically complex Caribbean alga that overgrows corals. Phycologia 48: 480–491. DOI: 10.2216/09-04.1 Ramicrusta textilis sp. nov. (Peyssonneliaceae, Gigartinales) is described from shallow, nearshore waters of Jamaica (Caribbean Sea). The reddish-gold to brown thalli grow on bedrock and dead coral heads, but they may also overgrow living corals. Thallus morphology is highly variable; a single confluent thallus may include smooth, prostrate crustose portions, overlapping foliose lobes, curtainlike erect lobes, and apically flaring columns. Tabular basal cells in parallel filaments support downgrowing, unicellular rhizoids on the ventral surface and branching assurgent filaments toward the dorsal surface. Extensive formation of secondary pit connections among lower cells of the assurgent filaments join cells of adjacent filaments along a horizontal axis that is oblique to that of each subtending layer, resulting in a pseudoparenchymatous construction that is highly patterned and tightly integrated. The outer cortex contains large cells associated with raised rims on the thallus surface, and these cells are interpreted as hair cell initials. Calcification is extensive, and the structure of the mineral skeleton, exposed by removal of organic material, is described by scanning electron microscopy. Peyssonnelia calcea and Ramicrusta nanhaiensis, both known only from the Indo-Pacific Ocean, are the only other peyssonnelioid species whose vegetative anatomy involves secondary pit connections or cell fusions, and their relationship to R. textilis is considered. Molecular analyses also indicate a relationship with R. nanhaiensis and support assignment of this new species to the genus Ramicrusta.