Author: Bunke D.

Source: Acta Zoologica, Volume 84, Number 2, April 2003 , pp. 87-97(11)

Publisher: Wiley-Blackwell

Abstract:

Bunke, D. 2003. Early development of metanephridia in the caudal budding zone of a clitellate annelid, Dero digitata (Naidida): an electron-microscopical study. — Acta Zoologica (Stockholm) 84: 87–97

Ultrastructural analysis has revealed that metanephridia in Dero digitata arise from three nephroblast cells in the frontal epithelium of a septum suggesting its mesodermal origin. Each cell has a fixed developmental destination, one nephroblast cell produces the entire canal part and two cells give rise to the nephrostome. The nephroblast cell nearest to the body wall enlarges and proliferates a first set of canal cells, then one of the two proximally adjacent nephroblast cells differentiates into the envelope of the nephrostome generating the marginal cilia of the opening (mantle cell) and the second one transforms into the anteriormost cell of the funnel, producing a flame of cilia that beats into the canal lumen (flame cell). Thereafter, new canal cells appear, mainly by mitosis of the first cell, enlarging the body of the nephridium whose further differentiation was not analysed. Comparison with other clitellate species suggests a mantle cell (or some marginal cells) and a flame cell (or a central cell) to be special characters of the metanephridium in the stem species of the Clitellata and that, compared to many polychaete species, its early development assumes a special course by a precocious determination and arrangement of nephroblast cells, which, in both groups, probably originate from an identical mesodermal stem cell. Results further indicate that the nonclitellate Aeolosomatidae, by virtue of corresponding nephrostomata, are possibly closer related to the Clitellata.

Keywords: Dero digitata; Clitellata; metanephridia; development; nephrostome; nephroblast cells; Aeolosomatidae; phylogeny

Document Type: Research article

DOI: http://dx.doi.org/10.1046/j.1463-6395.2003.00128.x

Publication date: 2003-04-01

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