Kalicephalus (Occipitodontus) colossus (Nematoda: Diaphanocephalidae), a new hookworm from Naja kaouthia in central Thailand
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Issued Date
2026-01-01
Resource Type
ISSN
00311820
eISSN
14698161
Scopus ID
2-s2.0-105042181249
Journal Title
Parasitology
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SCOPUS
Bibliographic Citation
Parasitology (2026)
Suggested Citation
Charoennitiwat V., Viriyautsahakul S., Thaenkham U., Chaisiri K., Ratnarathorn N. Kalicephalus (Occipitodontus) colossus (Nematoda: Diaphanocephalidae), a new hookworm from Naja kaouthia in central Thailand. Parasitology (2026). doi:10.1017/S0031182026102248 Retrieved from: https://repository.li.mahidol.ac.th/handle/123456789/117502
Title
Kalicephalus (Occipitodontus) colossus (Nematoda: Diaphanocephalidae), a new hookworm from Naja kaouthia in central Thailand
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Abstract
The genus Kalicephalus Molin, 1861 comprises hookworms parasitising the gastrointestinal tract of reptiles, particularly snakes, and currently includes 34 recognised 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 rRNA and mitochondrial 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 localisation. 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 1–48 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.