Characterization of melanic and non-melanic forms in domestic and peridomestic populations of Triatoma infestans (Hemiptera: Reduviidae)

Abstract

Background: Melanic (dark) morphs have been barely reported in peridomestic and sylvatic conditions for Triatoma infestans, the most important vector of Chagas disease in the Southern Cone of South America. Adults with dark and small yellow markings on the connexivum were collected after manual searches conducted by technical personnel in 62 domiciliary units in Cruz del Eje, Córdoba Province, Argentina. The last community-wide insecticide spraying campaign before the study had been conducted three years earlier. We investigated if there was a measurable color morph variation (melanic and non-melanic) in wings and connexivum; we determined infestation, distribution of melanic and non-melanic forms, and correspondence of colorimetric variation with variations in morphology (wing size and shape and body length), development (wing fluctuating asymmetry), physiology (nutritional status) or behaviour (flight initiation).Results: Forty-nine females, 54 males and 217 nymphs were collected in 24 domiciliary units. House infestation and colonization were 53% and 47%, respectively. Most of the T. infestans individuals (83.2%) were collected in chicken coops; intradomicile infestation was recorded in only one case. The chromatic cluster analysis showed two well-defined groups: melanic and non-melanic. The melanic group included 17 (35%) females and 25 (46%) males. Peridomestic infestation was lower for melanic than for non-melanic adults. Melanic morphs were collected in houses from several localities. Sexual dimorphisms were confirmed by morphometric measurements. Body length was large in melanic adults (P < 0.01 only for males). Differences between groups were significant for wing size and shape, but not for weight or weight/body length ratio. Melanic females and males showed significantly higher fluctuating asymmetry (FA) indices than their non-melanic counterparts.Conclusions: This is the second report of melanic forms of T. infestans in domestic and peridomestic habitats in the Dry Chaco region of Argentina. Although non-melanic adults exhibited a higher infestation rate, melanic adults were widespread in the area and were collected in the infested domicile and in most types of peridomestic annexes. Differences in morphometric variables between groups might be due to different ecological adaptations. The higher FA © The Author(s) 2020. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article' s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article' levels observed in melanic individuals suggest a higher developmental instability and a selective advantage of nonmelanic individ...

Quantitative Imagery Analysis of Spot Patterns for Haplogroup Classification of Triatoma Dimidiata (Latreille, 1811) (Hemiptera: Reduviidae) an Important Vector of Chagas Disease

“…The study of coloration in triatomines and its application in taxonomy has mainly been used in traditional qualitative approaches [32]. This has led to the assumption of a lack of clear morphological diagnostic characters to facilitate recognition and formal descriptions at the species level [15].…”

“…The lighter pattern elements can be present on any area of the body or appendages, and the color, intensity, and distribution of these elements are of considerable importance for systematic purposes. The pattern of the connexivum region is particularly marked [32].…”

Quantitative imagery analysis of spot patterns for the three-haplogroup classification of Triatoma dimidiata (Latreille, 1811) (Hemiptera: Reduviidae), an important vector of Chagas disease

“…However, despite the taxonomic importance of these pattern elements, there have been very few quantitative studies of color and pattern variation in Triatoma . The first studies to quantify color patterns in a species of Triatoma were by carried out by Nattero et al [ 33 ], who analyzed the melanic and non-melanic forms of domestic and peridomestic populations of Triatoma infestans , and by Carmona-Galindo et al [ 34 ] who, in addition to other aspects, explored pattern variation as a function of elevation in triatomines from El Salvador, including populations of T. dimidiata . To date, the utility of the spot pattern to discriminate among haplogroups within the dimidiata complex or any other triatomine complex has not been explored.…”