Associations between reproductive cycle and occurrence of intestinal helminths infecting the Egyptian lizard, Chalcides ocellatus

Hala Ebaid

doi:10.21608/eajbsz.2011.14310

Abstract

Little attention has been given to the association between the host reproductive cycle and the dynamics of parasitic infection in the reptilian model. This relationship was investigated in this study with the common intestinal nematode, Thelandros schusteri (Family: pharyngodonidae) infecting the Egyptian lizards, Chalcides ocelattus. Fifty threelizards were collected during winter and spring 2009 and were weighted and sexed. The gonads were weighted and gonadosomatic index (GSI) was calculated; both represent measures of the reproductive cycle. The intestinal nematodes were recovered from the intestine by the standard technique. Results showed that the seasonal variation did not affect the infection prevalence in male or female lizards while GSI greatly affected the prevalence in female lizards only. Females with low GSI showed the highest infection prevalence while, those of high GSI showed the highest intensity of infection. Positive or negative correlations between number of follicles/ ovary, gonad mass or GSI and the intensity of infection in female hosts suggested that the investment in reproduction of females is more costly than for males. We interpret the high intensity of infection in females to be an effect of the reproductive cycle and conclude that sex dependent difference is very important in such pattern of host parasite relationship when aspects of reproductive cycle are considered and that the host reproductive investment may be a factor contributing to occurrence of parasitic infection.

Highlights

One of the most abundant and widespread reptile species in Africa and Egypt is the lizard, Chalcides ocelattus where its distribution being primarily attributed to its tolerance of diverse environments ranging from the steppe through agricultural fields to woodland habitats (Al-Shareef & Saber 1995)
Variations in infection prevalence of male and female lizards according to seasonal variation, host weight and gonadosomatic index (GSI) were shown in Figures (1-3)
The highest prevalence of infection was recorded in female lizards with a low GSI (43.8%) and the lowest one was recorded in female with a high GSI (33.3%)

Summary

Introduction

One of the most abundant and widespread reptile species in Africa and Egypt is the lizard, Chalcides ocelattus where its distribution being primarily attributed to its tolerance of diverse environments ranging from the steppe through agricultural fields to woodland habitats (Al-Shareef & Saber 1995). Hosts are expected to evolve defense mechanisms aiming at limiting the negative effect of parasitism on their fitness. Hosts have evolved a series of morphological, physiological, and behavioral adaptations to fight off parasitic attacks. On their side, parasites have responded to the selection pressures exerted by their hosts by evolving counter-adaptations to overcome host defenses. Parasites have responded to the selection pressures exerted by their hosts by evolving counter-adaptations to overcome host defenses These cycles of host–parasite adaptations/counter-adaptations define the so-called coevolutionary process, one of the most prominent characteristics of host–parasite interactions (Sorcia & Garnier 2008)

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