Prevalence of Trypanosoma lainsoni and its effects of parasitism on the health of non-volant small mammals from the Brazilian Cerrado

Small mammals are important hosts and/or reservoirs of Trypanosoma spp. This study aimed to verify the prevalence of Trypanosoma spp. in non-volant small mammals from the Brazilian Cerrado and to test the effects of T. lainsoni on the neutrophil/lymphocyte ratio (N/L) and body condition in rodent and marsupial populations. For this, we collected blood samples of 293 individuals captured in five forest fragments between 2019 and 2020. Blood was used to prepare the blood smears and packed on filter paper for DNA extraction. Generalized linear models were performed to test the effects of T. lainsoni on host health. The DNA was submitted to nested PCR targeting the Trypanosoma spp. 18S rRNA gene. From blood smears analyzed by microscopy, we obtained a positivity rate of 7.2% for Trypanosoma spp. About 31.1% of Gracilinanus agilis, Didelphis albiventris, and Rhipidomys macrurus samples were positive in nested PCR. From the obtained sequences, 83.3% were genetically identical to T. lainsoni and about 11% to T. cruzi TcI. In addition, we reported the infection of T. lainsoni in Hylaeamys megacephalus. We suggest that T. lainsoni does not influence the body condition and N/L ratio for either G. agilis or R. macrurus. Overall, our results expand the host list of T. lainsoni and demonstrate the infection of small mammals by T. cruzi TcI in peri-urban areas.

Spatial and social organization of the burrowing rodent Clyomys laticeps (Thomas, 1909)

Burrowing rodents display diverse patterns of social organization, ranging from solitary to group living. Differences in social organization are often inferred from patterns of space use, particularly differences in the degree to which individual home ranges overlap. Here, we characterize patterns of space use in a poorly studied species of burrow-dwelling echimyid rodent, the Broad-headed Spiny Rat (Clyomys laticeps). Specifically, we use radiotelemetry studies of a free-living population in Parque Estadual da Serra de Caldas Novas (Goiás, Brazil) to evaluate previous, apparently contradictory reports suggesting that this species is both solitary and social. A total of 20 adult (12 females, 8 males) C. laticeps were monitored via telemetry during two consecutive cycles of annual wet and dry seasons. The resulting data indicate that although overlap of individual home ranges was common, co-occurrence of adults in time and space was rare and was limited to male–female pairs, a pattern that is most consistent with a solitary lifestyle in which individuals occupy distinct burrow systems. Neither sex nor season affected spatial overlap; this outcome is consistent with evidence suggesting that reproduction in this species occurs throughout the year. Although home ranges for males were larger than those for females, areas occupied by both males and females overlapped with multiple opposite-sex individuals, making it difficult to determine from spatial data whether the study population was polygynous or polygynandrous. While genetic data are needed to characterize fully the mating system of these animals, our analyses provide the first detailed information regarding spatial relationships in C. laticeps, thereby allowing more accurate placement of this species within a larger, comparative behavioral framework and facilitating efforts to identify factors contributing to social diversity among burrow-dwelling rodents.

First report of the intestinal helminth community in the broad-headed spiny-rat Clyomys laticeps (Rodentia, Echimyidae)

The broad-headed spiny rat, Clyomys laticeps, is an echimyid rodent found in open areas of Cerrado and Pantanal biomes in central Brazil and Paraguay. Little is known about the parasites associated with this semi-fossorial species, as no previous studies have been conducted on their helminth fauna. The aim of this study was to report the helminth community structure of C. laticeps inhabiting Serra de Caldas Novas State Park, a Cerrado area in central Brazil. Trappings were carried out in dry grasslands from January to October 2016, and the large and small intestines of 14 C. laticeps individuals were examined for the presence of helminths. Three nematode species were found: Fuellebornema almeidai, Pterygodermatites (Paucipectines) sp., and Subulura forcipata, and 85.7% of the studied species were infected with at least one of these helminths. F. almeidai was the most prevalent species among hosts, and S. forcipata was the most abundant. This study is the first report on helminth community structure in C. laticeps. We report a new host species and increase the known geographical range of F. almeidai, and provide the first record of Pterygodermatites (Paucipectines) sp. infecting echimyids. This is also the first report of S. forcipata in a mammal host.

Seasonal changes of faecal cortisol metabolite levels in Gracilinanus agilis (Didelphimorphia: Didelphidae) and its association to life histories variables and parasite loads

The aim of this study was to evaluate the role of environmental (dry versus wet season) and individual (sex, body mass and reproductive status) factors in the levels of faecal cortisol metabolites (FGCs) in Gracilinanus agilis faecal samples as an index of stress levels in this species; as well as its association with abundance of Eimeria spp, as an indicator of immunocompetence against parasites. Our study found that FGCFGCs are a reliable indicator of adrenal activity in G. agilis. We found that FGCFGCs increase considerably by environmental stressors like the dry season. Moreover, the observed positive association between FGCs and body mass is the result of the effect of season and reproduction in both variables. We also demonstrated that an increase in FGC levels among G. agilis during the dry season is associated with a rise in the probability of being infected by Eimeria spp. Hence, our finding supports the corticosteroid-fitness hypothesis, which predicts that increased glucocorticoids as a response to stressors usually results in decreased fitness of individuals, translated into low future survival and reproductive success, and higher parasite infection. To our knowledge, this is the first study that integrates environmental changes, hormone responses and parasite loads in a US marsupial in both empirical and experimental approaches.

Non-volant small mammals at an Atlantic forest area situated nearby a limestone quarry (Limeira quarry), state of São Paulo, Brazil

Our aim was to survey the non-flying small mammals inhabiting an Atlantic forest area situated nearby a limestone quarry (Limeira quarry), located at Ribeirão Grande municipality (SP), southeastern Brazil. Species were captured with pitfall and Sherman traps along eight pairs of 60 m transects distributed at four different distances from the quarry (60, 220, 740 and 1300 m). Between October 2005 and January 2008, 20 small mammal species (11 rodents and nine marsupials) were captured through 4080 pitfall trap-nights and 2040 Sherman trap-nights. The high values of richness, diversity (H' = 2.65) and equability (J = 0.88), and the presence of endemic and threatened species indicates a preserved study site and small mammal assemblage. Marmosops incanus, Monodelphis americana and Oligoryzomys nigripes were the commonest species at the study site. Trapping sites located closer to the quarry (60 and 220 m away from the quarry) presented lower richness and were dominated by disturbance-tolerant species, such as O. nigripes, that usually benefit from habitat alterations. On the other hand, sites located away from the quarry and closer to Serra do Mar Protected Area (740 and 1300 m away from the quarry) presented higher richness and diversity, and a higher abundance of disturbance-intolerant species. These results suggest a negative distance-dependent impact of quarrying on small mammal communities. In this way, our results point out to the importance of long-term monitoring of quarrying impacts on small non-flying mammal communities and populations, and the need of conservation strategies in order to ensure species persistence in these areas.