AN INTEGRATIVE INVESTIGATION OF NORTH AMERICAN GYRINICOLA (NEMATODA: OXYUROIDEA)

Author

Matthew Walker, Southern Illinois University CarbondaleFollow

Date of Award

5-2023

Degree Name

Master of Science

Department

Zoology

First Advisor

Jiménez-Ruiz, Francisco Agustín

Second Advisor

Brown, Jason L.

Third Advisor

Bolek, Matthew G.

Abstract

Gyrinicola Yamaguti, 1938 are oxyurid mutualists found within the intestinal tract of numerous larval anuran species in Europe, Asia, South America and North America, with 6 species being currently recognized. The systematic placement and hierarchical treatment of the genus has shifted since its discovery, originally considered as its own family (Gyrinicolidae), then treated as a subfamily (Gyrinicolinae) within Cosmocercidae, then considered a member of the Pharyngodonidae, followed by a transference to the Cosmocercidae, and finally a recent proposal to resurrect Gyrinicolidae. The morphology of the uterine tract is a characteristic often used to diagnose members the genus; yet, species show variability in the morphology of these tracts. Until recently very few DNA sequences were available to aid in the phylogenetic placement of this unique group of worms. Within North America, only Gyrinicola batrachiensis is recognized. This species, however, also has a controversial taxonomic history. Historically, two nematodes infecting larval anurans were once recognized in North America: Pharyngodon batrachiensis and Pharyngodon armatus though these were synonymized due to morphological similarity. To evaluate the potential distribution, taxonomic relation, and possible species diversity of Gyrinicola I used an integrative approach utilizing locality, morphology and genetic information of specimens from a wide range within the United States. Phylogenies of the nuclear ribosomal genes 28S, 18S, ITS1-5.8S-ITS2, and newly sequenced partial mitochondrial genomes suggest at least four species groups exist among the nematodes from North America and that these groups, alongside G. japonica, form a well-supported group within Oxyuroidea. This study represents the first genetic evaluation of the diversity of the genus in North America, and the first comparison of these nematodes collected from such distant localities, and clearly indicates that further investigation of these worms is required to characterize their true diversity. It also suggests further representation of Pharyngodonidae from other vertebrate classes may help clarify the relations of this historical grouping to other members of the Oxyuroidea.