Polymorphism and inconsistencies in the taxonomy of Diplodinium anisacanthum da Cunha, 1914 (Ciliophora, Entodiniomorphida, Ophryoscolecidae) and taxonomic notes on the genus Diplodinium Schuberg, 1888

Abstract

The genus Diplodinium includes 31 species of ophryoscolecid ciliates with two retractable ciliary zones in the anterior end of the body, with no skeletal plates, inclined macronucleus and two contractile vacuoles. They have a broad geographical distribution and low host specificity. The genus has several taxonomic inconsistencies, mainly due to polymorphism of most species. Diplodinium anisacanthum is a case of taxonomic inconsistency in the genus. It presents polymorphism in posterior end of the body, so it is considered a polymorphic species or seven distinct species. This study presents the morphological characterization of six D. anisacanthum morphotypes based on general morphology, morphometric analysis and oral infraciliature characterization and taxonomic notes on the genus Diplodinium. The morphological and morphometric characterization of D. anisacanthum showed great similiarities among morphotypes suggesting that these ciliates constitute a single species with polymorphisms. A brief review conducted highlights the inconsistencies in the taxonomy of the genus Diplodinium and demonstrates the need for recent studies with representatives of the genus. There is no information on how polymorphism of Diplodinium anisacanthum morphotypes correlates to molecular data, since there are only two sequences of this species available in the GenBank database.

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

“…Recently, some studies revised the systematics of some Ophryoscolecidae genera [ Diplodinium , Diploplastron , Ostracodinium , and Metadinium Cedrola et al, 2017a, b, 2018, 2021] and according to molecular phylogenetic reconstructions (Cedrola, Senra, et al, 2017; Cedrola et al, 2020; Rossi et al, 2015), the systematics of the family needs reconsideration, as many of the classification available do not reflect evolutionary divergences.…”

“…In fact, according to Cedrola, Senra, et al (2017) the evolutionary signal of the 18S rDNA is insufficient to reconstruct intra‐family relationships within Ophryoscolecidae. Recent studies have recently revised the classification of the genera Diplodinium , Diploplastron , Metadinium , and Ostracodinium (Cedrola et al 2017a, b, 2018, 2021), and here, we complemented the discussion with considerations of the validity of the genera Elytroplastron and Eremoplastron , and on the phylogenetic position of D . polygonale .…”

“…In fact, according to Cedrola, Senra, et al (2017) the evolutionary signal of the 18S rDNA is insufficient to reconstruct intra-family relationships within Ophryoscolecidae. Recent studies have recently revised the classification of the genera Diplodinium, Diploplastron, Metadinium, and Ostracodinium (Cedrola et al 2017a(Cedrola et al , b, 2018(Cedrola et al , 2021, and here, we complemented the discussion with considerations of the validity of the genera Elytroplastron and Eremoplastron, and on the phylogenetic position of D. polygonale. We conclude that integrative approaches, using ultrastructural data and multigene phylogenies or phylogenomics are necessary to better understand the evolutionary relationships within Ophryoscolecidae and improve its systematics.…”

“…The most recent systematic review of the family was performed 55 years ago (Latteur, 1966) and only recently, some studies revised the systematics of part of its genera, such as Diplodinium Schuberg, 1888, Diploplastron Kofoid & MacLennan, 1932, Metadinium Awerinzew & Mutafowa, 1914, and Ostracodinium Dogiel, 1927 (Cedrola et al, 2017a, b, 2018, 2021) and discussed systematic incongruences based on molecular analyses (Cedrola, Senra, et al, 2017; Cedrola et al, 2020; Rossi et al, 2015). These papers stress that a far‐reaching revision of the systematics of this family is required, indicating that the current taxonomy does not reflect evolutionary relationships and is insufficient to organize the diversity of the group (Dogiel, 1927; Kofoid & MacLennan, 1930, 1932, 1933).…”

Rumen Ciliated Protozoa of the Free-Living European Bison (Bison bonasus, Linnaeus)

“…At least four replicates were counted per sample and per ciliate species. The protozoan genera and species were identified according to the size and the shape of cells, skeletal plates (if present), macronucleus, and ciliature arrangement (Dogiel, 1927 ; Ogimoto and Imai, 1981 ; Williams and Coleman, 1992 ; Ito and Imai, 1998 ; Ito et al, 2001 ; Cedrola et al, 2017a , b , 2018 ). Different staining procedures were used to stain skeletal plates (iodine solution), nuclei (methyl green-formalin-saline and chrome-alum-carmine), and infraciliature (pyridinated silver carbonate method) (Ogimoto and Imai, 1981 ).…”