Hostname: page-component-78c5997874-8bhkd Total loading time: 0 Render date: 2024-11-09T15:40:51.962Z Has data issue: false hasContentIssue false

Ellerbeckia arenaria (Bacillariophyceae): formation of auxospores and initial cells

Published online by Cambridge University Press:  28 November 2001

ANNA-MARIA M. SCHMID
Affiliation:
Institut für Pflanzenphysiologie, Universität-Salzburg, Hellbrunnerstrasse 34, 5020 Salzburg, Austria
RICHARD M. CRAWFORD
Affiliation:
Alfred Wegener Institut für Polar und Meeresforschung, Postfach 120161, 27515 Bremerhaven, Germany
Get access

Abstract

The development of auxospores and initial cells of the freshwater chain-forming diatom Ellerbeckia arenaria forma arenaria was studied using light and electron microscopy. Whether the auxospore mother cell is formed vegetatively (parthenogenesis) or through autogamy is still a matter for speculation. Because no signs of spermiogenesis could be detected in our material, we exclude oogamy. Further development involves retraction of the protoplast from the epivalve and the formation of a featureless siliceous cap with a central opening on its free surface. The homology and function of this cap remain uncertain. At the other end of the cell the protoplast remains tightly attached to the hypovalve throughout its further development. This hypovalve always has a concave valve face. An organic wall bearing many layers of overlapping, small silica scales begins to be formed while the cell is still enclosed within the mother cell wall, and allows the auxospore to swell, thus breaking the siliceous cap and girdle bands. External and internal surfaces of scales can be distinguished morphologically. Initial valves are formed internal to the scales at an oblique angle to the parent chain. The initial epivalve always faces the hypotheca of the auxospore mother cell, and the initial valves already show elements of the heterovalvy manifest in the vegetative cells. The significance of the observations in terms of ecology and phylogeny is discussed. The combinations Ellerbeckia arenaria (Moore ex Ralfs) R. M. Crawford, and E. arenaria forma teres (Brun ex Schmidt) R. M. Crawford are made.

Type
Research Article
Copyright
2001 British Phycological Society

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)