Ctenocephalides orientis and Ctenocephalides felis in Thailand: Head geometry by species, sex and geography

Kruawan Chotelersak; Srisombat Puttikamonkul; Yudthana Samung; Tanawat Chaiphongpachara; Jean-Pierre Dujardin; Suchada Sumruayphol

doi:10.1111/mve.12707

Ctenocephalides orientis and Ctenocephalides felis in Thailand: Head geometry by species, sex and geography

Med Vet Entomol. 2024 Jan 31. doi: 10.1111/mve.12707. Online ahead of print.

Authors

Kruawan Chotelersak¹, Srisombat Puttikamonkul¹, Yudthana Samung², Tanawat Chaiphongpachara³, Jean-Pierre Dujardin⁴, Suchada Sumruayphol²

Affiliations

¹ Department of Microbiology, Faculty of Medicine, Srinakharinwirot University, Bangkok, Thailand.
² Department of Medical Entomology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
³ Department of Public Health and Health Promotion, College of Allied Health Sciences, Suan Sunandha Rajabhat University, Samut Songkhram, Thailand.
⁴ INTERTRYP, University of Montpellier, CIRAD, IRD, Montpellier, France.

PMID: 38296831
DOI: 10.1111/mve.12707

Abstract

Fleas in the genus Ctenocephalides serve as biological vectors or intermediate hosts of microorganisms such as bacteria, rickettsia, protozoa and helminths. Ctenocephalides felis has a worldwide distribution, while C. orientis has long been considered as a subspecies of C. felis in Asia. To help the morphological recognition of these two species and further explore their differences, we used the geometric morphometric approach applied to the head. Both sexes were examined. Five anatomical landmarks of the head were used, and to capture the curvature of the front head, 10 semilandmarks were added. There was a consistent difference in species classification accuracy when considering landmarks only versus their combination with semilandmarks, suggesting the importance of the curve of the head as a taxonomic signal. Using or not the labels in the reclassification analyses, the head shape allowed by itself almost perfect recognition of the two species, in both sexes, even after adjustment for prior probabilities. The same approach disclosed a high level of sexual size and shape dimorphism in both species. The contribution of size variation to the discrimination by shape was much more important between sexes (from 27% to 45%) than between species (from 0.7% to 7.1%). Nevertheless, in our data, size never could represent a way to reliably recognise the sex of an individual, even less its species. Geographical variation in head shape could only be explored for the C. orientis sample. No significant correlation of morphometric variation with geography could be detected, which would be consistent with gene flow between Thai provinces. The geometric morphometric approach of the flea head, when it incorporates head curves, is a promising tool for rapid, economical, and accurate species and sex identification. It is, therefore, a useful tool for future epidemiological and demographic studies.

Keywords: C. felis; Ctenocephalides orientis; Thailand; geometric morphometrics; landmarks; semilandmarks; sexual dimorphism.

Grants and funding

JRA-CO-2563-13724-TH/The Coordinating Center for Thai Government Science and Technology Scholarship Students (CSTS), National Science and Technology Development Agency (NSTDA)