Vegetative and reproductive morphology of Botryocladia botryoides, B. occidentalis and B. canariensis sp. nov. (Rhodymeniaceae, Rhodophyta) from the Canary Islands

Abstract

The type species of Botryocladia, B. botryoides, and B. occidentalis and B. canariensis Afonso-Carrillo & Sobrino sp. nov., are described in detail from material collected in the Canary Islands. The previously incomplete and partially ambiguous information about the vegetative and reproductive morphology of B. botryoides is completed and clarified. Botryocladia botryoides exhibits as its most relevant attributes arborescent solid axes bearing near-spherical determinate lateral vesicles, vesicle walls consisting of four (to six) cell layers, outer cortical cells loosely arranged forming a near-continuous surface layer, one to four secretory cells borne both on unmodified and modified stellate medullary cells, spermatangia cut off from closely packed palisade-like spermatangial mother cells, cystocarps incompletely immersed in the vesicle, and tetrasporangia derived from an inner intercalary cortical cell remaining immersed in the subsurface cortical layer. Occurrence of B. occidentalis in the eastern Atlantic is confirmed. Botryocladia occidentalis differs from B. botryoides mainly by its thinner threelayered vesicle walls and by the fact that its secretory cells are borne exclusively on unmodified medullary cells. Botryocladia canariensis, known so far only from the Canary Islands, differs from other Botryocladia species by a unique combination of significant attributes, including a dimorphism in secretory cells (obovoid to pyriform when they occur in small clusters on modified medullary cells, and subspherical when solitary on unmodified medullary cells). It is postulated that the eastern Atlantic B. guineensis, the western Atlantic B. ganesanii, and the Indo-Pacific B. skottsbergii are the closest relatives of the new species. We analyse the features of the type species B. botryoides with the aim of delineating a clear boundary between Botryocladia and the next genus Irvinea. The pattern of growth of the vesicles (determinate vs indeterminate) is suggested as a potentially important diagnostic feature for genus separation.