Laurencia minuta sp. Nov. (ceramiales, rhodomelaceae), a diminutive red alga from the gulf of aqaba (red sea)

Laurencia minuta sp. nov. is described from plants growing on leaves of the seagrass Halophila stipulacea (Forsskal) Ascherson at Elat, Gulf of Aqaba (Gulf of Elat), Red Sea. Erect, clavate fronds arise from a small basal disc and plants do not become stoloniferous. Spermatangia, carpogonial branches, carposporophytes and tetrasporangia are formed on fronds 0-7-3-5 mm in length and 400-800 pm in diameter. Plants grown from basal discs in crude culture became reproductively mature in five days, suggesting an opportunistic, ephemeral strategy. The presence of secondary pit connections between adjacent cortical cells, the occurrence of tetrasporangia in parallel rows near the apices, and the formation of tetrasporocytes abaxially place this species in the type subgenus Laurencia, although some reorganization of the subgenera and sections of the genus seems necessary. The terete fronds, the absence of lenticular thickenings, and the lack of radially elongated cortical cells suggest that L. minuta should be referred to the type section Laurencia. The irregular horizontal surface undulations at the apices, cortical cells with concave surfaces, and chloroplasts with radiating arms in this species are considered at present to be species-specific characters. Address for correspondence.