COMPARATIVE MORPHOLOGY AND TAXONOMIC STATUS OF GRACILARIOPSIS (GRACILARIALES, RHODOPHYTA)

Abstract

The vegetative organization and reproductive development of Gracilariopsis lemaneiformis (Bory) Dawson, Acleto et Foldvik [including Gracilaria sjoestedtii Kylin] were investigated. Our observations on spermatangial development and post‐fertilization features establish that Gracilariopsis Dawson is distinct at the generic level from Gracilaria Greville, and ice propose the resurrection of Gracilariopsis Dawson as a result. Spermatangial parent cells of Gracilariopsis are superficial, initiated in pairs or groups of three by concavo‐convex longitudinal and transverse divisions. Each spermatangial parent cell cuts off a single, colorless spermatangium distally by a transverse division. The female reproductive apparatus consists of a supporting cell that bears a two‐celled carpogonial branch flanked by two sterile branches, as in Gracilaria. Likewise, up to six sterile cells fuse with the carpogonium after fertilization to produce a primary fusion cell that generates the gonimoblasts; however, a secondary fusion cell is absent. Inner gonimoblast cells unite with cytologically modified cells of the inner pericarp by means of secondary pit‐connections. Tubular nutritive cells are absent. The gonimoblast consists of a central sterile tissue interconnected throughout by secondary pit‐connections surmounted by a fertile layer composed of carposporangia aligned in straight chains. The distribution of Gracilariopsis is extended to Western Europe. Copyright © 1989, Wiley Blackwell. All rights reserved