Leptofauchea coralligena (Faucheaceae, Rhodophyta), a new species from the Mediterranean Sea

Abstract

Morphological and reproductive studies, corroborated by gene sequence data, demonstrate that there are two distinct entities within Mediterranean specimens referable to the red alga Rhodymenia ardissonei (Rhodymeniaceae). Genuine R. ardissonei grows in shallow water while specimens from deep water habitats, traditionally attributed to the same species, belong to Leptofauchea, a genus placed in the Faucheaceae. The deep water growth is herein described as a new species, Leptofauchea coralligena. Female gametophytes in Leptofauchea are easily distinguished because of the presence of a tela arachnoidea in the pericarp cavity and tetrasporangia developing in nemathecia. Sterile specimens, however, can be extremely difficult to tell apart because differences in vegetative morphology and anatomy are subtle. Refractive bodies in the medullary cells form the most conspicuous diagnostic character separating L. coralligena from R. ardissonei. These structures can be easily observed in young specimens of L. coralligena, both in surface view and transverse sections. However this character becomes less obvious or even impossible to observe in mature thalli with medullary cells containing large amounts of floridean starch. Refractive bodies are also difficult to observe in herbarium specimens. The existence of these structures has not previously been reported from any other Leptofauchea species. The presence of L. coralligena has been confirmed in the western Mediterranean Sea. Atlantic specimens attributed to R. ardissonei require further study