Relationship between the weights of seed beetles of the genus Megacerus Fåhraeus, 1839 (Coleoptera: Chrysomelidae: Bruchinae) and their host seeds of the family Convolvulaceae.

We studied seeds from a set of plant species from the Convolvulaceae family. Seeds collected from natural populations and infested with beetles of genus Megacerus were monitored until the beetle emergence. We analyze the relationship between body weight of beetles and seed weight of host plants, and its connection with between-species differences and sexual dimorphism. The results show that differences in the scaling of body weight of beetles are associated with sexual dimorphism. For the same species of beetle, the females tend to have heavier bodies than the males. Differences between host plants species in the weight of seeds are related to differences in the body weight Megacerus species, resulting in a distinctive pattern of seed infestation across hosts. Small-sized (lighter) species of beetles tended to infest small-sized (lighter) seed species and, correspondingly, heavier beetles species tended to do it in heavier seed species. Mechanisms of female oviposition preferences may be involved to generate that pattern. In general, the beetle weight showed an asymptotic relation with the host seed weight. The greater the weight of the seed, the greater the weight of adult beetle was. However, the proportion in weights reaches an asymptotic value probably because beetles reached the maximum possible weight for their species. We conclude that the process of specialization in the seed-beetle assemblage studied is influenced by intrinsic traits of the species involved in the interaction (beetles and seeds) and by differences between sexes in their sexual-allocation paths.

Prevalence, Abundance and Intensity of Eggs and Oocysts of Gastrointestinal Parasites in the Opossum Didelphis Virginiana Kerr, 1792 in Yucatan, Mexico.

Virginia opossum, Didelphis virginiana, is a synanthropic mammal associated with peridomestic areas of Yucatán, However, little is known about the gastrointestinal parasite infections of this species. The infection prevalence, mean abundance and mean intensity of eggs and oocysts of gastrointestinal parasites, in opossums captured in the peridomestic areas were estimated in six rural localities of Yucatán, Mexico. Eighty-four faecal samples were processed by flotation technique. McMaster test was used to estimate the number of helminth eggs and protozoa oocysts per gram of feces. Seven genera of gastrointestinal parasites were identified, and then infection prevalence was estimated as follows: Protozoa Eimeria sp. (51.9 %) and Sarcocystis sp. (1 %); nematodes Ancylostoma sp. (80.56 %), Cruzia sp. (62.04 %), Trichuris sp. (60.19 %), Capillaria sp. (29.63 %), Turgida sp. (23.15 %), Toxocara sp. (11.11 %), and Ascaris sp. (1.85 %); and one acanthocephalan: Oligacanthorhynchus sp. (14.81 %). This is the first study on the diversity of gastrointestinal parasites in Virginia opossums, and first evidence about the potential role of opossums in the transmission of zoonotic gastrointestinal parasites in peridomestic areas of Yucatán, Mexico.

Survival and reproduction of Onthophagus landolti (Coleoptera: Scarabaeidae) exposed to ivermectin residues in cattle dung.

Two bioassays were conducted in parallel to assess the effects of cattle treated with either 1% ivermectin (IVM) or 3.15% IVM (dosed at 0.2 and 0.63 mg kg-1, respectively) on reproduction and survival of Onthophagus landolti Harold. Adult beetles were exposed 10 days to faeces of treated cattle starting at: one day before treatment (controls), 3, 6, 14, 28 and 35 days post-treatment. Adult survival of O. landolti was not affected by either of the two treatments. Faecal residues of 1% IVM almost completely suppressed fecundity of beetles at 3, 6 and 14 days post-treatment (dPT), and reduced fecundity of O. landolti at 28 dPT ( 38.3%), relative to controls. Meanwhile, IVM residues after treatment with 3.15% IVM almost completely suppressed fecundity of beetles at 3, 6, 14 and 28 dPT, and reduced fecundity of O. landolti at 35 dPT (80.9%), relative to controls. Larval survival was significantly reduced only at 3 dPT with 1% IVM. Meanwhile, treatment with 3.15% IVM significantly reduced larval survival at 6, 14 and 28 dPT. Larval mortality was recorded only in L-I and L-II instars. Moreover, in both bioassays, most of the L-I and L-II specimens that survived showed signs of toxicity. In conclusion, residual IVM in cattle faeces after treatment with injectable IVM has a detrimental effect on the fecundity of adult O. landolti up to 4 weeks post-treatment and on the subsequent larval survival.

Ticks collected from humans, domestic animals, and wildlife in Yucatan, Mexico.

Domestic animals and wildlife play important roles as reservoirs of zoonotic pathogens that are transmitted to humans by ticks. Besides their role as vectors of several classes of microorganisms of veterinary and public health relevance, ticks also burden human and animal populations through their obligate blood-feeding habit. It is estimated that in Mexico there are around 100 tick species belonging to the Ixodidae and Argasidae families. Information is lacking on tick species that affect humans, domestic animals, and wildlife through their life cycle. This study was conducted to bridge that knowledge gap by inventorying tick species that infest humans, domestic animals and wildlife in the State of Yucatan, Mexico. Amblyomma ticks were observed as euryxenous vertebrate parasites because they were found parasitizing 17 animal species and human. Amblyomma mixtum was the most eryxenous species found in 11 different animal species and humans. Both A. mixtum and A. parvum were found parasitizing humans. Ixodes near affinis was the second most abundant species parasitizing six animal species (dogs, cats, horses, white-nosed coati, white-tail deer and black vulture) and was found widely across the State of Yucatan. Ixodid tick populations may increase in the State of Yucatan with time due to animal production intensification, an increasing wildlife population near rural communities because of natural habitat reduction and fragmentation. The diversity of ticks across host taxa documented here highlights the relevance of ecological information to understand tick-host dynamics. This knowledge is critical to inform public health and veterinary programs for the sustainable control of ticks and tick-borne diseases.

Lethal and Sublethal Effects of Ivermectin on Onthophagus landolti (Coleoptera: Scarabaeidae).

Previous work has documented toxic effects of ivermectin (IVM) on dung beetles from the Old World, but very little is known about this drug's effect on Neotropical dung beetles. Accordingly, we conducted a bioassay with dung spiked with IVM to assess its lethal and sublethal effects on the Neotropical dung beetle Onthophagus landolti Harold. The experimental design consisted of five treated groups G1, G2, G3, G4, and G5 receiving 0.001, 0.01, 0.1, 1.0, and 10 mg IVM/kg dung fresh weight, respectively, and two control groups (solvent control [CGA] and untreated control [CGU]). Adult survival and fecundity were measured throughout a 10-d period, and subsequent egg development and survival were monitored. Adult survival was only affected for treatment groups G4 and G5 groups (70 and 30%, respectively); groups G1, G2, G3 and both controls exhibited 100% survival. Fecundity was completely suppressed under treatment groups G4 and G5. Group G3 only had 1.7 and 2.1% brood mass production relative to CGA and CGU, respectively. Additionally, for groups G1 and G2 the proportion of adults emerging from brood masses was lower relative to CGA. Furthermore, development time for the second generation in groups G1 and G2 was 12.5% slower relative to control groups. Finally, dung removal by beetles from groups G3, G4, and G5 was significantly lower relative to control groups. In conclusion, toxic effects of IVM on O. landolti are associated mainly with reduced fecundity and lower dung-removal by adult beetles as well as reduced survival and slower development of offspring.

Triatoma dimidiata (Latreille) abundance and infection with Trypanosoma cruzi in a rural community of Yucatan, Mexico.

The present is a longitudinal study that describes the abundance of Triatoma dimidiata (Latreille) (Hemiptera: Reduviidae) and its infection with Trypanosoma cruzi in a rural community of Yucatan, Mexico. From a total of 370 individuals collected, 81.3% were adults, most from intradomicile ecotope (282/301), but nymphs were more abundant in peridomicile (58/69). The overall proportion of infected bugs was 21.9% (23.9% of adults and 13% of nymphs). The infection proportion was similar between intradomicile and peridomicile ecotopes (22.8% and 18.1%, respectively). Overall, 76.5% (36/47) of the houses and their backyards were infested. Of those, 27.7% were colonized and 75% had infected triatomines. Our data showed different proportions on infestation, colonization and bug density. Ninety-seven percent of overall peridomicile abundance was distributed in chicken coops, doghouses, opossum nests and dove cages. Triatomine entomological indices showed higher infestation and density inside domiciles, but higher colonization in the peridomicile. The abundance, the amount of infected intradomicile adult T. dimidiata and the incidence of infestation showed a seasonal pattern, with 63.7% of all individuals collected during the late dry season (April to June). We showed the peridomicile colonization of animal shelters and suggest it as a relevant source of T. dimidiata individuals. As infected bugs were found in both ecotopes, the studied area is under a high risk of T. cruzi transmission to humans.

Cyanobacteria-containing biofilms from a Mayan monument in Palenque, Mexico.

Surfaces of buildings at the archaeological site of Palenque, Mexico, are colonized by cyanobacteria that form biofilms, which in turn cause aesthetic and structural damage. The structural characterization and species composition of biofilms from the walls of one of these buildings, El Palacio, are reported. The distribution of photosynthetic microorganisms in the biofilms, their relationship with the colonized substratum, and the three-dimensional structure of the biofilms were studied by image analysis. The differences between local seasonal microenvironments at the Palenque site, the bioreceptivity of stone and the relationship between biofilms and their substrata are described. The implications for the development and permanence of species capable of withstanding temporal heterogeneity in and on El Palacio, mainly due to alternating wet and dry seasons, are discussed. Knowledge on how different biofilms contribute to biodegradation or bioprotection of the substratum can be used to develop maintenance and conservation protocols for cultural heritage.