Kalicephalus (Occipitodontus) colossus (Nematoda: Diaphanocephalidae): a new hookworm from Naja kaouthia in central Thailand
- 1Laboratory of Helminth Biodiversity and Drug Development, Department of Helminthology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- 2Applied Animal Science Laboratory, Department of Biology, Faculty of Science, Mahidol University, Bangkok, Thailand
Abstract
The genus Kalicephalus Molin, 1861 comprises hookworms parasitizing the gastrointestinal tract of reptiles, particularly snakes, and currently includes 34 recognized species worldwide. Despite their diversity, the taxonomy of the genus remains poorly resolved because most species have been described primarily from morphology and molecular data remain limited. During a helminthological survey of monocled cobras (Naja kaouthia) from central Thailand, large hookworms were recovered from the oesophagus that corresponded morphologically to the group traditionally assigned to Occipitodontus but differed from previously described species. Using an integrative taxonomic approach combining light microscopy, scanning electron microscopy, morphometric analyses and molecular phylogenetic analyses based on nuclear 18S ribosomal RNA (18S rRNA) and mitochondrial cytochrome c oxidase subunit I (COI) sequences, Kalicephalus colossus sp. nov. is described herein. The new species is distinguished by its exceptionally large body size, posteriorly projecting buccal capsule, equal alate spicules, lobate copulatory bursa and oesophageal localization. Multivariate analyses revealed clear sexual dimorphism without evidence of discrete morphotypes. Phylogenetic analyses recovered K. colossus sp. nov. as a distinct lineage within Kalicephalus, with genetic divergences of 1.1–1.4% for 18S rRNA and 12–13% for COI relative to congeners. The parasite was detected in 18% of examined hosts, with infection intensities ranging from 1 to 48 individuals per cobra, and was recorded only from suburban localities surrounding Bangkok. No obvious gross pathological lesions were observed during necropsy. The discovery of K. colossus sp. nov. expands current knowledge of reptile hookworm diversity in Southeast Asia and highlights the importance of integrative taxonomy for resolving parasite biodiversity.
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BibTeX
@article{charoennitiwat2026kalicephalus,
title = {{Kalicephalus (Occipitodontus) colossus (Nematoda: Diaphanocephalidae): a new hookworm from Naja kaouthia in central Thailand}},
author = {Vachirapong Charoennitiwat and Sila Viriyautsahakul and Urusa Thaenkham and Kittipong Chaisiri and Napat Ratnarathorn},
journal = {Parasitology},
year = {2026},
month = jun,
doi = {10.1017/s0031182026102248},
url = {https://doi.org/10.1017/s0031182026102248},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Kalicephalus (Occipitodontus) colossus (Nematoda: Diaphanocephalidae): a new hookworm from Naja kaouthia in central Thailand
AU - Vachirapong Charoennitiwat
AU - Sila Viriyautsahakul
AU - Urusa Thaenkham
AU - Kittipong Chaisiri
AU - Napat Ratnarathorn
PY - 2026
DA - 2026/06/16
JO - Parasitology
DO - 10.1017/s0031182026102248
UR - https://doi.org/10.1017/s0031182026102248
AB - The genus Kalicephalus Molin, 1861 comprises hookworms parasitizing the gastrointestinal tract of reptiles, particularly snakes, and currently includes 34 recognized species worldwide. Despite their diversity, the taxonomy of the genus remains poorly resolved because most species have been described primarily from morphology and molecular data remain limited. During a helminthological survey of monocled cobras (Naja kaouthia) from central Thailand, large hookworms were recovered from the oesophagus that corresponded morphologically to the group traditionally assigned to Occipitodontus but differed from previously described species. Using an integrative taxonomic approach combining light microscopy, scanning electron microscopy, morphometric analyses and molecular phylogenetic analyses based on nuclear 18S ribosomal RNA (18S rRNA) and mitochondrial cytochrome c oxidase subunit I (COI) sequences, Kalicephalus colossus sp. nov. is described herein. The new species is distinguished by its exceptionally large body size, posteriorly projecting buccal capsule, equal alate spicules, lobate copulatory bursa and oesophageal localization. Multivariate analyses revealed clear sexual dimorphism without evidence of discrete morphotypes. Phylogenetic analyses recovered K. colossus sp. nov. as a distinct lineage within Kalicephalus, with genetic divergences of 1.1–1.4% for 18S rRNA and 12–13% for COI relative to congeners. The parasite was detected in 18% of examined hosts, with infection intensities ranging from 1 to 48 individuals per cobra, and was recorded only from suburban localities surrounding Bangkok. No obvious gross pathological lesions were observed during necropsy. The discovery of K. colossus sp. nov. expands current knowledge of reptile hookworm diversity in Southeast Asia and highlights the importance of integrative taxonomy for resolving parasite biodiversity.
SN - 0031-1820
SN - 1469-8161
ER -