Ultrastructure of the nephrostome in Enchytraeus albidus (Annelida, Clitellata) |
| |
Authors: | Dieter Bunke |
| |
Institution: | (1) Zoologisches Institut, Lehrstuhl für Spezielle Zoologie, Auf der Morgenstelle 28, D-72076 Tübingen, Germany e-mail: dieter.bunke@uni-tuebingen.de, Tel.: 07071/ 2972617, Fax: 07071/294634, DE |
| |
Abstract: | The nephrostome of Enchytraeus albidus exhibits a longitudinal slit-like opening on the dorsal side of a bulbous organ which is mainly composed of three cells,
one flame cell situated centrally and endowed with a ciliary flame, and two cells lying superficially, called the mantle cell
and the accessory mantle cell. The mantle cell occupies the ventral side of the organ extending on both sides up to the opening
to constitute its immediate border on the frontal and lateral sides. Here it forms a kind of crest which is heavily subdivided
into many protrusions and infoldings endowed with long cilia which exclusively spread into the coelomic cavity. The accessory
mantle cell borders the narrow posterior slit of the opening, forming the roof of the initial canal which is devoid of cilia.
From its anterior region a projection arises extending above the opening. The flame cell forms a groove from which the ciliary
flame arises which extends into the canal. At its posterior region it replaces the accessory mantle cell displacing it onto
the dorsal surface of the organ. It is argued that the mantle cell and the accessory mantle cell have presumbly originated
from coelothelial cells. Thus the metanephridium may be a composite organ developing from a nephridioblastic and a coeloblastic
source. A discussion of results in other annelid species indicates that metanephridia in the Annelida may have evolved more
than once.
Accepted: 13 October 1997 |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|