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.

Centre of Systemic Biology for Crop Protection Universidad de O'Higgins Campus Colchagua Chile

Computational Biology Independent Researcher Medellin Colombia

Faculty of Agriculture and Technology University of South Bohemia České Budějovice 37005 Czech Republic

Institute of Entomology Biology Centre of the Czech Academy of Sciences CAS České Budějovice 37005 Czech Republic

Laboratory of Nematology Institute of Agri food Animal and Environmental Sciences Universidad de O'Higgins Campus Colchagua Chile

Zobrazit více v PubMed

Andaló V., Nguyen K. B., Moino A.. Heterorhabditis amazonensis n. sp. (Rhabditida: Heterorhabditidae) from Amazonas, Brazil. Nematology: International Journal of Fundamental and Applied Nematological Research. 2006;8:853–867. doi: 10.1163/156854106779799286. DOI

Astashyn A., Tvedte E. S., Sweeney D., Sapojnikov V., Bouk N., Joukov V., Mozes E., Strope P. K., Sylla P. M., Wagner L., Bidwell S. L., Brown L. C., Clark K., Davis E. W., Smith-White B., Hlavina W., Pruitt K. D., Schneider V. A., Murphy T. D.. Rapid and sensitive detection of genome contamination at scale with FCS-GX. Genome Biology. 2024;25:60. doi: 10.1186/s13059-024-03198-7. PubMed DOI PMC

Auch A. F., Klenk H. P., Göker M.. Standard operating procedure for calculating genome-to-genome distances based on high-scoring segment pairs. Standards in Genomic Sciences. 2010a;2:142–148. doi: 10.4056/sigs.541628. PubMed DOI PMC

Auch A. F., Von Jan M., Klenk H. P., Göker M.. Digital DNA-DNA hybridization for microbial species delineation by means of genome-to-genome sequence comparison. Standards in Genomic Sciences. 2010b;2:117–134. doi: 10.4056/sigs.531120. PubMed DOI PMC

Bankevich A., Nurk S., Antipov D., Gurevich A. A., Dvorkin M., Kulikov A. S., Lesin V. M., Nikolenko S. I., Pham S., Prjibelski A. D., Pyshkin A. V., Sirotkin A. V., Vyahhi N., Tesler G., Alekseyev M. A., Pevzner P. A.. SPAdes: A new genome assembly algorithm and its applications to single-cell sequencing. Journal of Computational Biology. 2012;19:455–477. doi: 10.1089/cmb.2012.0021. PubMed DOI PMC

Bedding R. A., Akhurst R. J.. A simple technique for the detection of insect parasitic rhabditid nematodes in soil. Nematologica. 1975;21:109–110. doi: 10.1163/187529275X00419. DOI

Bernt M., Donath A., Jühling F., Externbrink F., Florentz C., Fritzsch G., Pütz J., Middendorf M., Stadler P. F.. MITOS: Improved de novo metazoan mitochondrial genome annotation. Molecular Phylogenetics and Evolution. 2013;69:313–319. doi: 10.1016/j.ympev.2012.08.023. PubMed DOI

Bhat A. H., Machado R. A. R., Abolafia J., Ruiz-Cuenca A. N., Askary T. H., Ameen F., Dass W. M.. Taxonomic and molecular characterization of a new entomopathogenic nematode species, Heterorhabditis casmirica n. sp., and whole genome sequencing of its associated bacterial symbiont. Parasites and Vectors. 2023;16:383. doi: 10.1186/s13071-023-05990-z. PubMed DOI PMC

Bolger A. M., Lohse M., Usadel B.. Trimmomatic: a flexible trimmer for Illumina sequence data. Bioinformatics. 2014;30:2114–2120. doi: 10.1093/bioinformatics/btu170. PubMed DOI PMC

Cantarel B. L., Korf I., Robb S. M. C., Parra G., Ross E., Moore B., Holt C., Sánchez Alvarado A., Yandell M.. MAKER: An easy-to-use annotation pipeline designed for emerging model organism genomes. Genome Research. 2008;18:188–196. doi: 10.1101/gr.6743907. PubMed DOI PMC

Chen S., Zhou Y., Chen Y., Gu J.. Fastp: An ultra-fast all-in-one FASTQ preprocessor. Bioinformatics (Oxford, England) 2018;34:i884–i890. doi: 10.1093/bioinformatics/bty560. PubMed DOI PMC

Chevenet F., Brun C., Bañuls A. L., Jacq B., Christen R.. TreeDyn: Towards dynamic graphics and annotations for analyses of trees. BMC Bioinformatics. 2006;7:439. doi: 10.1186/1471-2105-7-439. PubMed DOI PMC

Courtney W. D., Polley D., Miller V. L.. TAF, an improved fixative in nematode technique. Plant Disease Reporter. 1955;39:570–571.

Dhakal M., Nguyen K. B., Hunt D. J., Ehlers R. U., Spiridonov S. E., Subbotin S. A.. Molecular identification, phylogeny and phylogeography of the entomopathogenic nematodes of the genus Heterorhabditis Poinar, 1976: A multigene approach. Nematology: International Journal of Fundamental and Applied Nematological Research. 2020;23:451–466. doi: 10.1163/15685411-bja10052. DOI

Dierckxsens N., Mardulyn P., Smits G.. NOVOPlasty: De novo assembly of organelle genomes from whole genome data. Nucleic Acids Research. 2016;45:e18. doi: 10.1093/nar/gkw955. PubMed DOI PMC

Edgar R. C.. MUSCLE: Multiple sequence alignment with high accuracy and high throughput. Nucleic Acids Research. 2004;32:1792–1797. doi: 10.1093/nar/gkh340. PubMed DOI PMC

Edgington S., Buddie A. G., Moore D., France A., Merino L., Hunt D. J.. Heterorhabditis atacamensis n. sp. (Nematoda: Heterorhabditidae), a new entomopathogenic nematode from the Atacama Desert, Chile. Journal of Helminthology. 2011;85:381–394. doi: 10.1017/S0022149X10000702. PubMed DOI

Emms D. M., Kelly S.. OrthoFinder: Phylogenetic orthology inference for comparative genomics. Genome Biology. 2019;20:238. doi: 10.1186/s13059-019-1832-y. PubMed DOI PMC

Griffin C. T., Downes M. J., Block W.. Tests of Antarctic soils for insect parasitic nematodes. Antarctic Science. 1990;2:221–222. doi: 10.1017/S095410209000030X. DOI

Katoh K., Kuma K., Toh H., Miyata T.. MAFFT version 5: Improvement in accuracy of multiple sequence alignment. Nucleic Acids Research. 2005;33:511–518. doi: 10.1093/nar/gki198. PubMed DOI PMC

Kimura M.. A simple method for estimating evolutionary rates of base substitutions through comparative studies of nucleotide sequences. Journal of Molecular Evolution. 1980;16:111–120. doi: 10.1007/BF01731581. PubMed DOI

Kumar S., Stecher G., Tamura K.. MEGA7: Molecular Evolutionary Genetics Analysis version 7.0 for bigger datasets. Molecular Biology and Evolution. 2016;33:1870–1874. doi: 10.1093/molbev/msw054. PubMed DOI PMC

Langmead B., Salzberg S. L.. Fast gapped-read alignment with Bowtie 2. Nature Methods. 2012;9:357–359. doi: 10.1038/nmeth.1923. PubMed DOI PMC

Lankin G., Santiagos A., Hermosilla M., Aballay E., San-Blas E.. A novel approach for the biological control of invasive Bagrada bugs with entomopathogenic nematodes. Journal of Pest Science. 2022;95:699–707. doi: 10.1007/s10340-021-01400-4. DOI

Letunic I., Bork P.. Interactive tree of life (iTOL) v3: An online tool for the display and annotation of phylogenetic and other trees. Nucleic Acids Research. 2016;44:W242–W245. doi: 10.1093/nar/gkw290. PubMed DOI PMC

Machado R. A. R., Abolafia J., Robles M. C., Ruiz-Cuenca A. N., Bhat A. H., Shokoohi E., Půža V., Zhang X., Erb M., Robert C. A. M., Hibbard B.. Description of Heterorhabditis americana n. sp. (Rhabditida, Heterorhabditidae), a new entomopathogenic nematode species isolated in North America. Parasites and Vectors. 2025a;18:101. doi: 10.1186/s13071-025-06702-5. PubMed DOI PMC

Machado R. A. R., Bhat A. H., Abolafia J., Muller A., Bruno P., Fallet P., Arce C. C. M., Turlings T. C. J., Bernal J. S., Kajuga J., Waweru B., Toepfer S.. Multi-locus phylogenetic analyses uncover species boundaries and reveal the occurrence of two new entomopathogenic nematode species, Heterorhabditis ruandica n. sp. and Heterorhabditis zacatecana n. sp. Journal of Nematology. 2021;53:1–42. doi: 10.21307/jofnem-2021-089. PubMed DOI PMC

Machado R. A. R., Muller A., Hiltmann A., Bhat A. H., Půža V., Malan A. P., Castaneda-Alvarez C., San-Blas E., Duncan L. W., Shapiro-Ilan D., Karimi J., Lalramliana, Lalramnghaki H. C., Baimey H.. Genome-wide analyses provide insights into genetic variation, phylo- and co-phylogenetic relationships, and biogeography of the entomopathogenic nematode genus Heterorhabditis. Molecular Phylogenetics and Evolution. 2025b;204:108284. doi: 10.1016/j.ympev.2025.108284. PubMed DOI

Machado R. A. R., Wüthrich D., Kuhnert P., Arce C. C. M., Thönen L., Ruiz C., Zhang X., Robert C. A. M., Karimi J., Kamali S., Ma J., Bruggmann R., Erb M.. Whole-genome-based revisit of Photorhabdus phylogeny: Proposal for the elevation of most Photorhabdus subspecies to the species level and description of one novel species Photorhabdus bodei sp. nov., and one novel subspecies Photorhabdus laumondii subsp. clarkei subsp. nov. International Journal of Systematic and Evolutionary Microbiology. 2018;68:2664–2681. doi: 10.1099/ijsem.0.002820. PubMed DOI

Meier-Kolthoff J. P., Auch A. F., Klenk H. P., Göker M.. Genome sequence-based species delimitation with confidence intervals and improved distance functions. BMC Bioinformatics. 2013;14:60. doi: 10.1186/1471-2105-14-60. PubMed DOI PMC

Meier-Kolthoff J. P., Hahnke R. L., Petersen J., Scheuner C., Michael V., Fiebig A., Rohde C., Rohde M., Fartmann B., Goodwin L. A., Chertkov O., Reddy T., Pati A., Ivanova N. N., Markowitz V., Kyrpides N. C., Woyke T., Göker M., Klenk H. P.. Complete genome sequence of DSM 30083T, the type strain (U5/41T) of Escherichia coli, and a proposal for delineating subspecies in microbial taxonomy. Standards in Genomic Sciences. 2014;9:2. doi: 10.1186/1944-3277-9-2. PubMed DOI PMC

Nguyen K. B. Nguyen K.B., Hunt D.J. Entomopathogenic nematodes: systematics, phylogeny and bacterial symbionts. Nematology Monographs and Perspectives. Vol. 5. Brill; Leiden: 2007. Methodology, morphology and identification; pp. 59–119. (Eds.),

Nguyen K. B., Shapiro-Ilan D., Mbata G. N.. Heterorhabditis georgiana n. sp. (Rhabditida: Heterorhabditidae) from Georgia, USA. Nematology: International Journal of Fundamental and Applied Nematological Research. 2008;10:433–448. doi: 10.1163/156854108783900276. DOI

Parks D. H., Imelfort M., Skennerton C. T., Hugenholtz P., Tyson G. W.. CheckM: Assessing the quality of microbial genomes recovered from isolates, single cells, and metagenomes. Genome Research. 2015;25:1043–1055. doi: 10.1101/gr.186072.114. PubMed DOI PMC

Pereira C.. Rhabditis hambletoni n. sp., nema apparentemente semiparasito da Broca do algodoeiro (Gasterocercodes brasiliensis) Archivos Instituto Biologico. 1937;8:215–231.

Poinar G. O.. Description and biology of a new insect parasitic rhabditoid, Heterorhabditis bacteriophora n. gen., n. sp. (Rhabditida; Heterorhabditidae n. fam.) Nematologica. 1975;21:463–470. doi: 10.1163/187529275X00239. DOI

Poinar G. O., Karunakar G. K., David H.. Heterorhabditis indicus n. sp. (Rhabditida: nematoda) from India: Separation of Heterorhabditis spp. by infective juveniles. Fundamental and Applied Nematology. 1992;15:467–472.

Price M. N., Dehal P. S., Arkin A. P.. FastTree 2 – approximately maximum-likelihood trees for large alignments. Plos One. 2010;5:e9490. doi: 10.1371/journal.pone.0009490. PubMed DOI PMC

Půža V., Machado R. A. R.. Systematics and phylogeny of the entomopathogenic nematobacterial complexes Steinernema–Xenorhabdus and Heterorhabditis–Photorhabdus. Zoological Letters. 2024;10:13. doi: 10.1186/s40851-024-00235-y. PubMed DOI PMC

Půža V., Machado R. A. R., Malan A. P.. Systematics, diversity and biogeography of entomopathogenic nematodes and their bacterial symbionts. Journal of Invertebrate Pathology. 2025;211:108362. doi: 10.1016/j.jip.2025.108362. PubMed DOI

San-Blas E., Campos-Herrera R., Dolinski C., Monteiro C., Andaló V., Leite L. G., Rodríguez M. G., Morales-Montero P., Sáenz-Aponte A., Cedano C., López-Nuñez J. C., Del Valle E., Doucet M., Lax P., Navarro P. D., Báez F., Llumiquinga P., Ruiz-Vega J., Guerra-Moreno A., Stock S. P.. Entomopathogenic nematology in Latin America: A brief history, current research and future prospects. Journal of Invertebrate Pathology. 2019;165:223–245. doi: 10.1016/j.jip.2019.03.010. PubMed DOI

Seppey M., Manni M., Zdobnov E. M. Kollmar M. Gene prediction. Vol. 1962. New York: Springer; 2019. BUSCO: Assessing genome assembly and annotation completeness; pp. 227–245. PubMed

van Lenteren J. C., Bueno V. H. P., Betiol W.. Latin America has the largest area under augmentative biological control worldwide, mainly with applications in open field crops. Biological Control. 2025;207:105827. doi: 10.1016/j.biocontrol.2025.105827. DOI

Walker B. J., Abeel T., Shea T., Priest M., Abouelliel A., Sakthikumar S., Cuomo C. A., Zeng Q., Wortman J., Young S. K., Earl A. M.. Pilon: An integrated tool for comprehensive microbial variant detection and genome assembly improvement. Plos One. 2014;9:e112963. doi: 10.1371/journal.pone.0112963. PubMed DOI PMC

Wayne L. G., Brenner D. J., Colwell R. R., Grimont P. A. D., Kandler O., Krichevsky M. I., Moore L. H., Moore W. E. C., Murray R. G. E., Stackebrandt E., Starr M. P., Truper H. G.. Report of the ad hoc committee on reconciliation of approaches to bacterial systematics. International Journal of Systematic Bacteriology. 1987;37:463–464. doi: 10.1099/00207713-37-4-463. DOI

White G. F.. A method for obtaining infective nematode larvae from cultures. Science. 1927;66:302–303. doi: 10.1126/science.66.1709.302.b. PubMed DOI

Wick R. R., Judd L. M., Gorrie C. L., Holt K. E.. Unicycler: Resolving bacterial genome assemblies from short and long sequencing reads. PLoS Computational Biology. 2017;13:e1005595. doi: 10.1371/journal.pcbi.1005595. PubMed DOI PMC