Morphological and Molecular Characterization of Kochinema farodai Baqri and Bohra, 2001 (Dorylaimida: Nordiidae) from California, with the First Molecular Study and an Updated Taxonomy of the Genus.

Sergio Álvarez-Ortega

doi:10.3390/ani10122300

Abstract

Simple SummaryIn this paper, a population of a free-living nematode collected from Northern California (USA) is identified and studied. The aim of the present work is to characterize a Californian population of the nematode genus Kochinema, with morphological and molecular methods. In addition, a revision of this genus is also provided including an updated diagnosis, a list of species, a key to species identification, and a compendium of their main morphometrics and distribution data.This paper deals with the morphological and molecular characterization of Kochinema farodai Baqri and Bohra, 2001, with an integrative approach. The finding of K. faroidai in California is a remarkable biogeographical novelty, as it is the first American record of the species. Molecular data herein obtained represent the first molecular study of the genus Kochinema. Furthermore, scanning electron microscopy (SEM) observations of a member of Kochinema are provided for the first time. Additionally, this contribution provides new insights into the phylogeny and taxonomy of the nematode genus Kochinema. A brief historical outline of the matter is presented. Then, the morphological pattern of the genus is revised and illustrated, the anterior position of amphids, whose opening is located on lateral lip, being its most relevant diagnostic feature. The phylogenetic analysis inferred from D2–D3 expansion segments of 28S rRNA gene shows that Kochinema clustered together with other dorylaimid species characterized by the absence of pars refringens vaginae and that it does not share a recent common ancestor with other members of the family Nordiidae. A likely polyphyly of the family Nordiidae is confirmed. Finally, an updated taxonomy of the genus is proposed, including a revised diagnosis, a list of species, a key to species identification, and a compendium of their main morphometrics and distribution data.

Highlights

The genus Kochinema Heyns, 1963, is a very interesting and rare dorylaimid taxon.Kochinema has a narrow distribution, with occurrence only in Africa and Asia [1]
Eight valid species are listed under Kochinema [1], but most of these species were described based on only a few specimens
During nematological surveys conducted during the spring–summer of 2011 in natural areas of Northern California (USA), several specimens belonging to Kochinema were collected

Summary

Introduction

The genus Kochinema Heyns, 1963, is a very interesting and rare (infrequent) dorylaimid taxon. Eight valid species are listed under Kochinema [1], but most of these species were described based on only a few specimens (see Table S1). This nematode genus has never been the subject of a Animals 2020, 10, 2300; doi:10.3390/ani10122300 www.mdpi.com/journal/animals. Animals 2020, 10, 2300 revision of its taxonomy, and to date, there are no molecular data available of the genus which allow the elucidation of the relationships of Kochinema with its closest taxa. The morphological and molecular characterization of this new population of Kochinema from California provided new data that were used to elucidate the taxonomy and phylogeny of this rare nematode genus

Materials and Methods

Phylogenetic Analyses

Description

Molecular Characterization

Remarks

Bayesian

Distribution

Historical Outline

General Morphology

On the Phylogeny of Kochinema

Diagnosis

Key to Species Identification