Original paper
Intraclonal variation of the tripolar pennate diatom "Centronella reicheltii" in culture: strategies of reversion to the bipolar Fragilaria-form
Schmid, Anna Maria M.
Nova Hedwigia Band 65 Heft 1-4 (1997), p. 27 - 45
40 references
published: May 15, 1997
DOI: 10.1127/nova.hedwigia/65/1997/27
ArtNo. ESP050006500002, Price: 29.00 €
Abstract
Seven clones of "Centronella reicheltii" (6 tripolar, 1 bipolar with the typical kink, incisions and swellings) and 2 chains of Fragilaria crotonensis were isolated from a plankton sample taken from the Plußsee, Germany. Both, F. crotonensis and "C. reicheltii" varied in their chain length during culture, but variation in "C. reicheltii" was really dramatic. All 6 tripolar clones became bipolar, by either loosing one arm, becoming kinked as clone 7, or by shedding two arms, thus generating short-celled Fragilaria colonies. Polar wall features, such as the apical porefield, spines, and rimoportula were then combined with the features of the central outline, and the "ghost striae", originally in the center of the tripolar form, shifted into the arm. Restoration of the normal Fragilaria cell wall is accomplished by correcting the margin. Shortening of the apical axis of arms is often accompanied by increase in the transapical dimension and irregularity of striation, as well as a spontaneous switch from uni- to biseriate striation within a single colony. The relationship of "Centronella reicheltii" to Fragilaria crotonensis is discussed with respect to triradiation in other pennate and centric diatoms as a result of a disturbance either during auxospore formation or during regeneration from "resting stages". Torsion along the longitudinal axis of the arms, present also in F. crotonensis along the apical axis, is discussed with respect to a possible twist in cytoskeletal elements during valve formation. Evolution of bipolarity in diatoms may have been dependent on the evolution of a bundling mechanism of individual microtubules, and a defect in this mechanism may cause tripolarity.
Keywords
Bacillariophyceae • bipolarity • "Centronella reicheltii" • clonal cultures • Fragilaria crotonensis • teratologies • torsion • tripolarity