Morphological and Morphometric Characterization of Eodinium posterovesiculatum (Ciliophora, Ophryoscolecidae) in Brazilian Cattle

Abstract

The morphological variability of Eodinium posterovesiculatum (Ciliophora, Trichostomatia) has been interpreted in different ways: four distinct species or four morphotypes of the same species. The present study aims to perform morphological and morphometric comparative analysis of the four morphotypes found in cattle from the southeastern region of Brazil. Ruminal content samples were obtained from four Holstein x Gir cattle and fixed at 18.5% formalin for morphological analysis. Morphometry was performed based on individuals stained with Lugol's solution [1]. The infraciliary bands were stained using silver carbonate impregnation technique [2]. Morphological and morphometric characterizations, supported by literature, suggest that the four morphotypes of E. posterovesiculatum are actually a single polymorphic species due to small morphometric differences and mostly identical morphological characters, with the format of the caudal processes being the only morphological characteristic that sets them apart.

Insights into the systematics of the family Ophryoscolecidae (Ciliophora, Entodiniomorphida)

“…On the other hand, Kofoid and MacLennan (1930, 1932 considered such divergences as species-specific variations, separating each forma proposed by Dogiel (1927) into new species. However, Strelkow (1934, 1938) and more recently Williams and Coleman (1992), Imai et al (2002Imai et al ( , 2004, Cedrola, Senra, et al (2017), andFregulia et al (2020) showed that these polymorphisms used to describe these formae are artificial characters, which can be modulated by ruminal metabolic conditions, contradicting the organizational scheme proposed by Kofoid and MacLennan (1930, 1932.…”