Gelidiella minima sp. Nov. (rhodophyta) from victoria, australia: Implications for the generic classification of the gelidiaceae

Gelidiella minima sp. nov. (Gelidiaceae, Gelidiales) is described from the shallow subtidal of Point Lonsdale, Victoria, Australia, where it grows on shell fragments and both calcareous and non-calcareous encrusting algae. Plants form lax, entangled mats consisting of narrow, creeping axes attached at intervals by peg-like, penetrating holdfasts. Branches arise at the points of attachment, and either reflex and re-attach or become erect, 0-5—1-5 mm in length and reproductive. Medullary rhizines, characteristically found in the erect axes of all genera of the Gelidiaceae except for Gelidiella, are not formed in any part of the thallus of G. minima. Irregularly cruciately divided tetrasporangia occur in terminal stichidia or, occasionally, in lateral branches; stichidia are flattened, and sporangia are produced in acropetally developed rows of (4—)6(-7). Gametangial plants are monoecious and protandrous; spermatangia are formed subterminally on the erect branches and persist below the cystocarps. Mature cystocarps are uniporate and unilocular, with carposporangia in chains of 2-3 formed from gonimoblasts radiating from the region of the axial cell. G. minima differs from other species of the genus Gelidiella in its diminutive size, largely prostrate axes, and numbers of tetrasporangia per row. This is the first detailed report of the gametangia and cystocarps for a species of Gelidiella. It is suggested that a reorganization of the species of Gelidiella and Pterocladia based on features of the development of the cystocarp will likely lead to a more natural attribution of species within the two genera. This is not possible at present, as cystocarps are unknown in most species of Gelidiella, including the type species G. acerosa (Forsskal) Feldman et Hamel.