Morphometrics of Amblyomma mixtum in the State of Veracruz, Mexico

Abstract

The tick Amblyomma mixtum is an ectoparasite of veterinary and public health importance because of its role as a vector of zoonotic pathogens. However, little is known about A. mixtum intraspecific variability and if morphological differentiation exists between populations across its geographic range. This study aimed to determine by electron microscopy the morphological variability of A. mixtum populations in the state of Veracruz, which has a large livestock population among states in Mexico. Forty male and 40 female A. mixtum collected from the 10 natural regions of Veracruz state were analyzed microscopically to accomplish main component analysis for each sex. Clusters were calculated with the out-tree method and a dendrogram produced to group the specimens according to their morphometric characteristics. Using 10 main components, 77% of the morphological variation of the ticks was explained. This is a reflection of scarce intraspecific variation between females. The dendogram for females grouped six clusters of specimens with similar characteristics. Morphometric variability in males was described using eight main components. Limited intraspecific variation was also observed between males. In males, the dendogram yielded six groups with similar morphometric characteristics. Morphometric analyses confirmed that the only species from the Amblyomma cajennense complex that are parasites to livestock in Veracruz state is A. mixtum. The eryxenous nature of A. mixtum combined with the frequent movement of livestock hosts may contribute to the apparent homogeneous phenotype of this tick species in Mexico.

Molecular identification and morphological variations of Amblyomma lepidum imported to Egypt, with notes about its potential distribution under climate change

“…Fifteen morphological variables were measured for thirty A. lepidum male specimens. Abbreviations of the morphological characteristics follow previous literature (Walker et al 2003 ; Aguilar-Domínguez et al 2021b ; Okely et al 2021 ).…”

“…Variations in scutal ornamentation among Amblyomma species have been observed in African countries, such as A. variegatum and A. tholloni (Hoogstraal 1956 ). Morphometrics and morphological analyses have been conducted to examine shape variations in other Amblyomma species such as A. mixtum , A. gemma , A. variegatum , and A. hebraeum (Pretorius and Clarke 2001 ; Aguilar-Domínguez et al 2021b ). However, no study has yet investigated variations within the A. lepidum population.…”

Comparative mitogenomics elucidates the population genetic structure of Amblyomma testudinarium in Japan and a closely related Amblyomma species in Myanmar

“…Since different genes have different evolutionary rates, the final conclusions could have been affected by the targeted gene topology of the phylogenetic tree (Liu et al, 2018 ). Traditionally, morphological characterization has been used for species identification and differentiation of Amblyomma ticks (Aguilar‐Dominguez et al, 2021 ; Namgyal et al, 2021 ). Now, a molecular based characterization can provide insights on the genetic variance at the base‐pair level and the genetic diversity between and within species of Amblyomma ticks (Burger et al, 2012 ; Lopes et al, 2016 ).…”