# Heterorhabditis caligo n. sp. (Rhabditida: Heterorhabditidae): A New Entomopathogenic Nematode from Pichilemu Sand Dunes, Chile

## TL;DR

Scientists discovered a new species of nematode, Heterorhabditis caligo, in Chile's coastal dunes, distinguishing it from similar species through physical and genetic traits.

## Contribution

The paper introduces and describes Heterorhabditis caligo as a new species within the Heterorhabditidae family, based on morphological and molecular evidence.

## Key findings

- Heterorhabditis caligo differs from H. marelatus in juvenile morphometrics like pharynx length and excretory pore position.
- Males of H. caligo have shorter bursal papillae that do not reach the bursa's edge, unlike H. marelatus.
- Phylogenetic analysis confirmed H. caligo as a distinct species within the megidis group.

## Abstract

During a survey of the nematode biodiversity in the Petrel wetland (central Chile), a population of Heterorhabditis sp. was found in the coastal dune samples. Morphological, morphometric, and molecular studies indicated that this nematode belonged to the megidis group, and represented a novel species, which we named Heterorhabditis caligo n. sp. This nematode species resembles H. marelatus but it is different in the morphometrics of its infective juvenile in the following ways: pharynx length (135–150 μm vs. 120–138 μm), and the position of the excretory pore from the anterior end (105–128 μm vs. 81–113 μm). In males, the fourth and eighth pairs of the bursal papillae are shorter and do not reach the edge of the bursa in H. caligo n. sp., whereas all the papillae in H. marelatus reach the edge of the bursa. The excretory pore of amphimictic females of H. caligo n. sp. is located more posteriorly than in those of H. marelatus 193 (169–224) μm vs. 157 (139–178) μm, respectively. Phylogenetic analyses of the genus based on whole nuclear and mitochondrial genome sequences and on five gene markers showed a clear separation of Heterorhabditis caligo n. sp. from the other species, placing it within the megidis group.