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The distribution of parasites within host populations and communities, and the mechanisms responsible for these patterns, are poorly understood aspects of wildlife parasitology. Here, we evaluate the influence of the average abundance of endoparasite variance, using endoparasites of lizards from the Caatinga domain (semiarid region), north-eastern Brazil. We hypothesized that, due to the high number of generalist endoparasite species, they may occur randomly throughout host populations in an aggregate pattern. In addition, we evaluated the degree to which sample variance is influenced by the average abundance of endoparasite species, patterns of co-occurrence and dominance among endoparasite species and similarities between abundance and the richness of endoparasite infracommunities in several host species. Between September 2015 and February 2016, 2141 lizards (1233 infected) from 16 species were collected from six Caatinga areas. In total, 25,687 endoparasites were collected, which belonged to 13 species including nematodes, pentastomids, cestodes, trematodes and acanthocephalans. Parasite–host associations documented here included 39 newly identified interactions. Endoparasites occurred in a typical aggregate pattern of distribution within their hosts; there was no measurable preference related to the acquisition of hosts by endoparasites. Despite the new records, endoparasites found were commonly associated with lizards in Caatinga environments, which may reflect fauna composed of generalist endoparasite species.

Ecological characteristics and environmental variation influence both host species composition and parasite abundance. Abiotic factors such as rainfall and temperature can improve parasite development and increase its reproduction rate. The comparison of these assemblages between different environments may give us a more refined analysis of how environment affects the variation of helminth parasite abundance. The aim of the present study was to evaluate how temporal variation, host size, sex and reproduction affect helminth abundance in the Tropidurus hispidus lizard in Caatinga, Restinga and Atlantic Forest environments. Overall, larger-sized lizards showed higher helminth abundance. We found a monthly variation in the helminth species abundance in all studied areas. In the Caatinga area, monoxenic and heteroxenic parasites were related to the rainy season and to the reproductive period of lizards. In Restinga, monoxenic and heteroxenic helminth species were more abundant during the driest months. In the Atlantic Forest, the rainy and host reproductive season occurred continuously throughout the year, so parasite abundance was relatively constant. Nevertheless, heteroxenic species were more abundant in this area. The present results showed that the temporal variation, body size, sex, reproductive period and habitat type influence the abundance and composition of helminth species in T. hispidus.

Ethnozoological studies have shown that Spilotes pullatus Linn. (Colubridae: Ophidia), is associated with medicinal and magic-religious uses in Brazil.This study was designed to determine the chemical composition of the oil extracted from the body fat of S. pullatus and to test its antimicrobial properties, alone and in association with aminoglycosides, against fungi and bacterial strains in concentrations ranging between 1024 and 0.5 µg/mL.The snakes were collected in the Chapada do Araripe, county of Crato, Ceará State, Brazil. The oil was extracted in a Soxhlet apparatus using hexane. The methyl esters of the fatty acids present in the samples were identified using GC-MS. The antimicrobial and drug modulatory activities of oil were tested by microdilution against fungal and bacterial strains.The chemical composition of the fixed oils of S. pullatus identified 10 constituents representing 94.97% of the total sample. The percentages of saturated and unsaturated fatty acids were 33.59 and 61.38%, respectively, with the most abundant components being elaidic (37.26%). The oil did not demonstrate any antimicrobial or antifungal activity when tested alone, presenting MIC values ≥ 1024 µg/mL. However, when associated with antibiotics, it demonstrated synergistic effects with gentamicin against all the bacterial lineages assayed, and antagonistic effects with amikacin and neomycin against strains of Escherichia coli.Oil extracted from the body fat of S. pullatus did not demonstrate any inhibitory effects on bacterial or fungal activities, but was effective in modulating the effects of certain antibiotics.