Peyssonnelia immersa sp. Nov. (Cryptonemiales rhodophyta) from the british isles and france with a survey of infrageneric classification

Authors: Maggs, C.A. and Irvine, L.M.

Journal: British Phycological Journal

Volume: 18

Issue: 3

Pages: 219-238

ISSN: 0007-1617

DOI: 10.1080/00071618300650241

Abstract:

Peyssonnelia immersa sp. nov. is described from the British Isles and France. The species has been found intertidally on bedrock and stones and on mobile substrata in the sublittoral. It differs from all previously described species by possessing a unique combination of vegetative and reproductive characters; of particular note is the development of reproductive organs in extensive immersed sori. Terminal cruciate tetrasporangia, occasionally borne on thickened filaments, are surrounded by a complex stratified wall. Carpogonial branches, auxiliary cell branches and spermatangia are accessory in origin and develop among pigmented sterile filaments in the same sori. One or more gonimoblasts arise from the connecting filament after fusion with a series of auxiliary cells and the mature carposporophyte consists of simple or branched chains of 2-5 large carposporangia.In laboratory culture, tetraspores obtained from field material of P. immersa gave rise to crusts similar to field plants. Gametangia and immature carposporophytes were present after 236 days; reproductive development was apparently identical to that of field plants. Carpo- spores were released 179 days (6 months) later.Infrageneric classification is surveyed and the taxonomic value of several characters assessed: degree of calcification, if present; mode of origin of ascending filaments from the basal layer; arrangement of the basal layer filaments; habit (degree of adherence) of the plant; development of sori in a superficial or immersed position; pattern of carposporophyte development. The significance within the genus of gonimoblast origin from either the connecting filaments or auxiliary cells is discussed: the grouping of species according to these two modes of reproduction does not coincide with that using other taxonomic features and consequently we consider that the genus should not be subdivided on this basis. Both types of gonimoblast development have also been reported in Nemastoma and Predaea (Nemastomataceae). © 1983 British Phycological Society.

Source: Scopus