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Capreolia implexa gen. et sp. nov. (Gelidiales, Rhodophyta) in Australia and New Zealand; an intertidal mat-forming alga with an unusual life history

1993; Taylor & Francis; Volume: 32; Issue: 4 Linguagem: Inglês

10.2216/i0031-8884-32-4-266.1

2330-2968

Michael D. Guiry, H. B. S. Womersley,

Marine and coastal plant biology

A mat-forming, stoloniferous, marine red alga previously included within the Gelidium pusillum (Stackhouse) Le Jolis complex (Gelidiaceae, Rhodophyta) is common in the lower and mid eulittoral zones on the coasts of South Australia, Victoria, southern New South Wales, and the North, South and Chatham Islands of New Zealand. Only tetrasporangial and male plants have been found in the wild. Tetrasporangia are most abundant in autumn and winter in regular, acropetal rows on compressed, more or less erect branches. Five separate strains from Victoria showed the same life history in laboratory culture. Gametangial plants were formed from tetraspores at 15, 17 and 20°C, 16: 8 h (LD) and at 20°C, 8: 16 h (SD), reproduction being initiated when the plants were 2.5–4 mm in length. Stellate protuberances were formed in the vicinity of carpogonia on female plants, but only in the presence of male plants. These protuberances elongated to form down-growing, terete fronds that attached to the substratum and formed tetrasporangia in basal compressed leaflets at 20°C, SD, but not at 20°C, LD, and 15°C, LD and SD. Plants had to be at least 3 0mm long in culture before tetrasporangia were initiated. Tetraspores germinated to give further male and female plants in a 1 : 1 ratio. This species thus has a diphasic life history in which there is an alternation of gametangial and tetrasporangial phases, the tetrasporophyte developing directly from the fertilized carpogonium . Cystocarps were not produced by any of the strains . Consequently, it is not referable to Gelidium pusillum and cannot be placed in either of the two genera to which it is morphologically related, Gelidium and Pterocladia (Gelidiaceae), which are characterized mainly on the basis of cystocarp characters. In view of this, plus a life history that is unique in the Gelidiales and very rare in the Rhodophyta, the genus Capreolia gen. nov. (Gelidiaceae, Gelidiales)with a single species, Capreolia implexa sp . nov., is described.