The reptile tick Aponomma gervaisi (Acarina: Ixodidae) as a parasite of monitor lizards in Pakistan and India

Abstract

The common tick of monitor lizards (Varanus) in Pakistan, India, and Sri Lanka is Aponomma gervaisi. In nature it occurs on only one of three native varanid species (V. bengalensis), in spite of the fact that both remaining varanid species in the main area investigated (V. griseus and V. flavescens) are ecologically and geographically syntopic with Varanus bengalensis at the two extreme ecological conditions in which the latter is found. Individuals of Aponomma gervaisi do not use their major host (Varanus bengalensis) at random. The level of infestation varies between different localities, between different seasons of the year, and between hosts of different sizes.

Attachment sites of adult male and female Aponomma gervaisi are very specific. Males occur mainly on the lateral surfaces of the tail and/or in a shallow, medioventral depression immediately behind the cloaca; adult females are usually attached in the axillary or a nearby region. Larval and nymphal site preferences are less distinct than those of the adults, and attachment is probably partly determined by competitive factors. Breeding takes place at the adult female attachment sites.

It is suggested that there is an advantage in adult male ticks aggregating in specific small areas due to the proportionally greater effect of several closely packed individuals on the hosts immune response system, particularly in reference to lymphoid cell density. These cells and body fluids seem to comprise the main food of the males. Male attachment sites are often located in areas of high potential abrasion. Females tend to attach in protected sites. Since females are mainly blood-sucking, there is probably an advantage in dispersed attachment patterns.

Haemaphysalis sindensis Bilques and Masood is placed in the synonomy of Aponomma gervaisi.