Morphological characterization of two new species of Dicontophrya (Ciliophora: Astomatia: Contophryidae) commensal of earthworms (Oligochaeta: Annelida) of Ebebda and Nkolbikogo (Cameroon)

Abstract

Two new species of astomatous ciliates (Dicontophrya minus n. sp. and Dicontophrya ebebdaensis n. sp.) endocommensal of Glossoscolecidae earthworms pertaining to the genus Alma are described using light-microscopy and a combination of staining techniques (pyridinated ammoniacal siver nitrate and DAPI). Studies reveal the existence of two distinct morphological types as evidence of morphological diversification within the genus Dicontophrya de Puytorac and Dragesco, 1969. In the first morphological type represented by Dicontophrya minus n. sp., the cell is ovoid (90 x 125–35 x 115 µm) with a ribbon like axial macronucleus flanked with a relatively big micronucleus (6.2 µm in diameter). In the second morphological type (Dicontophrya ebebdaensis n. sp.), the cell is elongated and wormlike (180 x 215–35 x 50 µm) with a nuclear apparatus composed of a long ribbon shape macronucleus (171.1 µm), bearing in its posterior half a globulous micronucleus. In the two cases cells bear in the anterior end a depression in which lodges a skeletal apparatus build in the same plan of organization (a modified V shaped skeletal branch bearing about 7 skeletal fibers) that characterize the genus.

Introduction

The gut of oligochaetes Annelids can be considered as a succession of many contiguous microhabitats (de Puytorac & Mauret, 1956; Nana et al., 2014; Fokam et al., 2015) in which many microorganisms work cooperatively in the process of soil mineralization (Lavelle, 1997). Diverse ciliated unicellular organisms constitute the major component of this complex microbial community among which mouthless ciliates belonging to the Subclass Astomatia Schewiakoff, 1896, have been only covered by a few studies over the past four decades (de Puytorac and Dragesco, 1968, 1969; de Puytorac, 1969, 1972; Ngassam, 1983; Fokam, 2005; Fokam et al., 2008 ; Fokam et al., 2011, 2012, ).

Much work remains to be done for understanding the contribution of astomatous ciliates to earthwormsmediated soil mineralization and for analyzing their diversity as well as host-specificity. Since the Astomes are deprived of an oral region, classification within this enigmatic group of ciliate is based on four major features: (1) the presence and the nature of an attachment apparatus; (2) the presence, arrangement, and number of suture lines in the somatic ciliature; (3) the size and shape of the nuclear apparatus; and (4) the number and arrangement of pulsatile vacuoles.

The aim of the present study was to pursue the inventory of astomatous ciliates living in the gut of earthworms from Cameroon.Two new species are described on the basis of standard cytological methods and fluorescence labeling of nuclear and skeletal components. Morphological traits revealed through this dual approach, especially the topography of the attachment apparatus, clearly indicate the two ciliates as species belonging to the genus Dicontophrya de Puytorac and Dragesco, 1969, from Alma nilotica collected in the southwestern part of the center region of Cameroon.

Source : Morphological characterization of two new species of Dicontophrya (Ciliophora: Astomatia: Contophryidae) commensal of earthworms (Oligochaeta: Annelida) of Ebebda and Nkolbikogo (Cameroon)