Morphology and distribution of nongeniculate coralline algae (Corallinaceae, Rhodophyta) on the leaves of the seagrass Cymodocea nodosa (Cymodoceaceae).

Abstract

Four species of non geniculate coralline algae (Corallinaceae, Rhodophyta) were identified on leaves of the seagrass Cymodocea nodosa (Ucria) Ascherson: three Fosliella states of Hydrolithon Foslie and one species of Pneophyllum KOtzing. The species were identified by the morphology of the spore germination disc, the position of the trichocytes and the morphology of the ventral filaments, trichocyte fields, and sporangial and gametangial conceptacles. The distribution of the epiphytes was examined in terms of density, cover and fertility along the old leaves and during a whole annual cycle from a sublittoral meadow at El Medano, Tenerife, Canary Islands. Marked seasonal variations were recorded in density, cover and fertility. In spring density, cover and fertility were low, increasing during summer and reaching maximal peaks in late summer; in autumn cover and fertility decreased but high density persisted; in winter low cover and low fertility were detected, together with high density values. The density of coralline epiphytes along the leaves also showed seasonal variations. Density increased from proximal (younger) to distal (older) segments of the leaf in winter, decreased in summer and was relatively constartt in spring and autumn. The percentage cover increased at all seasons, from proximal to distal segments. Although sterile planfs were more abundant than fertile ones, the fertility always increased from proximal to distal segments.