Stenamoeba polymorpha, a New Species Isolated from Domesticated Horse Equus ferus caballus.

This research identifies a new type of amoeba species, Stenamoeba polymorpha, discovered in the diarrheic stool of a domesticated horse in the U.S., with unique features distinguishing it from other species in its genus.

Introduction

• The research focuses on the discovery and study of Stenamoeba polymorpha, a new species of amoeba, which was found in a domesticated horse suffering from diarrhea in Great Falls, Virginia, in the United States.

Characteristics & Morphology

• Stenamoeba polymorpha shares some features with the five other previously known Stenamoeba species. However, it differs in several ways, which justify its classification as a new species.
• Through the use of electron microscopy, it was determined that S. polymorpha has a substantially thicker cell surface lamina compared to other species in its genus.
• When observed under a light microscope, the amoebae displayed a dynamic polymorphic appearance, due to the formation and absorption of subpseudopodia from any region of the cell.
• The amoeba also exhibits distinctive locomotion patterns, creating subpseudopodia that direct and alternate their movement in a zigzagging path.
• Additionally, S. polymorpha amoeba can hold a vertical stance that is noticeably taller than it is wide or long.

Methodology & Findings

• Various scientific techniques and analyses were used to uphold the classification of Stenamoeba polymorpha as a new species. This included using small subunit ribosomal ribonucleic acid (RNA) gene analyses, which comprised phylogenies employing both broad and narrow taxon sampling, pairwise nucleotide comparisons, and secondary structure predictions developed in-silico.
• The analyses suggested discriminatory motifs in the eighth variable region in the Stenamoeba species.

Significance of Findings

• The discovery is significant as Stenamoeba polymorpha represents the first species of its genus found in mammal feces. Moreover, it is the first to produce a possible group one intron.
• The new species is only the second of its genus described from North America.
• Phylogenetic analyses suggest that Stenamoeba limacina is the closest known relative to this newly discovered species.