Furcifer labordi

Eckhardt, Falk, Strube, Christina, Mathes, Karina A., Mutschmann, Frank, Thiesler, Hauke, Kraus, Cornelia & Kappeler, Peter M., 2019, Parasite burden in a short-lived chameleon, Furcifer labordi, International Journal for Parasitology: Parasites and Wildlife 10, pp. 231-240 : 236-238

4.2. Interspecific comparison of F. labordi and F. cf. nicosiai

We found higher prevalence of gastrointestinal parasites in F. cf. nicosiai , but we found the first infections in F. labordi approx. 2–3 months after hatching. Among juvenile F. cf. nicosiai , which hatched around mid-February, we rarely detected any gastrointestinal parasites until the dry season in June. The delayed occurrence of gastrointestinal parasite infection in F. cf. nicosiai might be caused by a higher energy investment in the immune system and especially in parasite defense. In contrast to F. labordi , juveniles of this species exhibit rather slow growth rates, later sexual maturity and higher rates of recaptures and therefore potentially higher probability of survival ( Eckhardt et al., 2019) that might enable them to invest comparatively more energy into immune defense. Besides slow growth rates, juveniles probably digest less food insects and are therefore less prone to gastrointestinal parasites that are transferred by this route. Especially tapeworms that require reptiles as definite host use invertebrates as intermediate host. Furthermore, insects, such as flies can function as vectors to allocate parasite eggs to the next host ( Schneller et al., 2008). However, the probability of infection might not be equal during the sampling period and might be an additional factor for the later detection of gastrointestinal parasites in F. cf. nicosiai . Regarding the comparison of the adults of both species per month, we found that F. cf. nicosiai exhibited a higher prevalence of gastrointestinal parasites apart from May. We suspect that the longer cumulative exposure might have an influence on this observation. The higher prevalence of gastrointestinal parasites in F. labordi in May might be attributed to the relatively small amount of fecal samples of F. cf. nicosiai (n = 10) compared to F. labordi (n = 64).

With respect to multiple infections, we observed no significant interspecific differences. Although, triple infections were only found in F. labordi . Furcifer cf. nicosiai , as the longer living species probably has a comparatively longer exposure to potential infections, might have developed some resistance against these pathogens. However, when entering the mating season, the prevalence of gastrointestinal and blood parasites increased in F. cf. nicosiai as well. Concerning the intensity of coccidian oocyst shedding, we did not detect interspecific differences. However, as F. cf. nicosiai is the larger species, similar intensities of coccidian infection probably have milder effects on the individual's body condition.

Within the samples of both species, we found a very low prevalence of oxyurids, which is in accordance to the findings of Lutzmann (2007), who examined fecal samples of several wild living chameleon species from Masoala, Madagascar. Contrary to our findings, these parasites were frequently detected in specimens that were kept in captivity ( Biallas, 2013). Probably, in a terrarium, where the home range is very restricted, oxyurid density can increase rapidly due to their direct life cycle and resistant eggs.

In F. cf. nicosiai , we found a higher prevalence of filariid infection, which could be in turn explained by the comparatively longer exposition to blood-sucking arthropods such as Culex and Aedes due to their comparatively longer lifespan. Moreover, adult specimen of F. cf. nicosiai are considerably larger than adults of F. labordi and might therefore be easier to detect for mosquitos. As the prepatent period takes approx. 6 months ( Széll et al., 2001), due to its shorter lifespan F. labordi is less prone to be adversely affected by foleyellosis. Subsequently, this species rather irregularly functions as primary host for Foleyella aff. furcata . Contrary to F. labordi , we found that the comparatively high prevalence in January decreased towards March in F. cf. nicosiai , but hereafter rises towards June. Initially, this observation might be explained by the small amount of blood samples (n = 3) from F. cf. nicosiai in January. However, as sample size is respectively higher in the following months, this might indicate some immune defense mechanisms against the parasite, which changes to immunosenescence towards the beginning of the dry season. Additionally, the life cycle of Foleyella might also have an influence of the observed pattern. As adult stages are known to predominantly inhabit skin or muscle tissue, an infection with this parasite might not have always been detected.

We found that the prevalence and intensity of mites was higher in F. cf. nicosiai , which could be caused by their larger average body size and subsequently easier detection for mites. Moreover, regarding the differences in intensity, mite pockets are larger in F. cf. nicosiai and might therefore offer more space for these ectoparasites.

Concerning interspecific comparison, niche differentiation may in turn result in differences in the exposure to parasites. In our previous study ( Eckhardt et al., 2019) we observed that adults of F. cf. nicosiai showed significant higher roosting sites, which might reflect differences in habitat use of both species. Here, the composition of food insects (vectors for gastrointestinal parasites), mosquitos (vectors for blood parasites) and mites might be unequal.

In total, detailed studies investigating parasite burden and in connection with their life history and seasonality in reptiles are lacking ( Zimmerman et al., 2010). However, a comparative study in mammals revealed weak relationships between parasite species richness and longevity ( Cooper et al., 2012). These authors found a significant negative relationship between longevity and parasite species richness for ungulates, but not for carnivores or primates, indicating no general pattern of parasite richness according to life history in vertebrates. In contrast to our expectations, we found higher prevalences of gastrointestinal-, blood - and ectoparasites in adult F. cf. nicosiai compared to adult F. labordi . As F. cf. nicosiai is the longer living and larger species, these observations could be caused by differences of cumulative exposure, as well as body size. Here, it is difficult to disentangle which factors or interplay of factors influence these pattern. However, the fact that juveniles of F. cf. nicosiai show comparatively low infection rates until their maturation that takes approx. 11 months, suggests some immune defense mechanisms in juveniles compared to F. labordi . Although, following maturation this species seems to be affected by serious parasite infections, indicating that this age cohort reallocates their energy investment from self-maintenance to reproduction. Moreover, the accelerated growth rates that we observed after the aestivation ( Eckhardt et al., 2019), which involves higher food requirements might additionally influence the raise in gastrointestinal parasites.