Biology subjects

Lima, L. F.

Publications and source records attributed to Lima, L. F..

3 recordsLinked to original sources

bioRxiv2024

Elasmobranchs Exhibit Species-Specific Epidermal Microbiomes Guided by Denticle Topography

Elasmobranch epidermal microbiomes are species-specific, yet microbial assembly and retainment drivers are mainly unknown. The contribution of host-derived factors in recruiting an associated microbiome is essential for understanding host-microbe interactions. Here, we focus on the physical aspect of the host skin in structuring microbial communities. Each species of elasmobranch exhibits unique denticle morphology, and we investigate whether microbial communities and functional pathways are correlated with the morphological features or follow the phylogeny of the three species. We extracted and sequenced the DNA from the epidermal microbial communities of three captive shark species: Horn (Heterodontus francisci), Leopard (Triakis semifasciata), and Swell shark (Cephaloscyllium ventriosum) and use electron microscopy to measure the dermal denticle features of each species. Our results outline species-specific microbial communities, as microbiome compositions vary at the phyla level; C. ventriosum hosted a higher relative abundance of Pseudomonadota and Bacillota, while H. francisci were associated with a higher prevalence of Euryarchaeota and Aquificae, and Bacteroidota and Crenarchaeota were ubiquitous with T. semifasciata. Functional pathways performed by each species respective microbiome were species-specific metabolic. Microbial genes associated with aminosugars and electron-accepting reactions were correlated with the distance between dermal denticles, whereas desiccation stress genes were only present when the dermal denticle overlapped. Microbial genes associated with Pyrimidines, chemotaxis and virulence followed the phylogeny of the sharks. Several microbial genera display associations that resemble host evolutionary lineage, while others had linear relationships with interdenticle distance. Therefore, denticle morphology was a selective influence for some microbes and functions in the microbiome contributing to the phylosymbiosis. ImportanceMicrobial communities form species-specific relationships with vertebrate hosts, but the drivers of these relationships remain an outstanding question. We explore the relationship between a physical feature of the host and the microbial community. A distinguishing feature of the subclass Elasmobranchii (sharks, rays, and skates), is the presence of dermal denticles on the skin. These structures protrude through the epidermis providing increased swimming efficiency for the host and an artificial model skin affect microbial recruitment and establishment of cultured microbes but has not been tested on natural microbiomes. Here, we show some naturally occurring microbial genera and functional attributes were correlated with dermal denticle features, suggesting they are one, but not only contributing factor in microbiome structure on benthic sharks.

microbiology↗

bioRxiv2023

A ticket to ride: genetic structure and kdr mutations in Aedes aegypti populations along a road crossing the Amazon Rainforest in Amapa State, Brazil

Insecticide resistance in Aedes aegypti is a major threat to the control of this mosquito species that transmits viruses that cause diseases like dengue, Zika, and chikungunya. One type of resistance is caused by alterations in the Nav gene, known as kdr mutations. In Brazil, different kdr haplotypes are present in Ae. aegypti and they may impede vector control operations based on pyrethroids. Although natural populations tend to accumulate genetic differences among isolated localities, this mosquito can actively and passively disperse, hitchhiked with human transportation. In this study, we investigated the genetic structure and kdr dispersion in Ae. aegypti populations in six localities of the Amapa State, Brazil located along a north-south transect of the Amazonian Forest. Genetic structure was assessed using 12 microsatellite loci in a fragment analysis sequencing procedure, and qPCR methods were used to detect the presence and frequency of three well known kdr mutations (V410L, V1016I and F1534C). We found a high prevalence of kdr alleles in all localities, indicating that kdr is spreading in the Amapa State. The microsatellite analyses suggested a certain level of differentiation among the mosquito populations, dividing them into two well-defined clusters, as evidenced by Bayesian and DAPC analyses. The population from Oiapoque (located in the north along the border with French Guiana) had the highest kdr frequencies and the highest genetic differentiation compared to the other localities. Our findings suggest that there is genetic structure among Ae. aegypti from the Amapa State, but with some level of passive gene flow between population clusters. The study highlights the importance of continued surveillance of Ae. aegypti populations to monitor the spread of insecticide resistance and inform on vector control strategies. Author summaryAmapa, a State in northern Brazil, is crucial as a gateway for diseases due to its border with French Guiana. One notable example was chikungunya, transmitted by the Aedes aegypti mosquito, also responsible for dengue, Zika, and yellow fever viruses. Chemical insecticides have been the primary means of control, however, resistance to these compounds is spreading among Ae. aegypti populations, compromising their effectiveness. Mutations known as "kdr" contribute to resistance to pyrethroid insecticides. Our study focused on these mutations and genetic differentiation in Ae. aegypti populations from six cities along the road nestled amidst the Amazonian Forest, linking the capital, Macapa, to Oiapoque on the Brazil-French Guiana border. The results revealed high frequencies of kdr mutations in all populations, indicating probable resistance to pyrethroids. Genetic analysis showed two distinct groups among the mosquitoes, with evidence of mosquito flow, particularly between Macapa and Oiapoque, facilitated by human transportation. Monitoring insecticide resistance and mosquito migration is essential for effective vector control strategies. Understanding these factors enables us to combat mosquito-borne diseases and safeguard public health.

evolutionary biology↗

bioRxiv2019

The subtle balance of insulin and thyroxine on survival and development of primordial follicles cultured in vitro enclosed in ovarian tissue

Thyroid hormones have presented a positive hormonal interaction on follicular development of secondary follicles and oocytes from antral follicles; however, the effect of thyroid hormones on primordial follicles is unclear. Here we investigated the in vitro effects of combined insulin and thyroxine on caprine primordial follicle survival and development. Ovarian tissues were cultured for 1 or 7 days using 10 ng/ml (low) or 10 {micro}g/ml (high) insulin in the absence or presence of thyroxine at 0.5, 1 or 2 {micro}g/ml. Thereafter, follicular survival and development, gene expression related to apoptosis (Bcl2/Bax), insulin and thyroid receptors, and estradiol and reactive oxygen species production were evaluated. In low-insulin conditions, supplementation with 2 {micro}g/ml thyroxine maintained follicular survival similar to non-cultured control, while 0.5 {micro}g/ml thyroxine enhanced the survival (P<0.05) in comparison to thyroxine-free treatment. Only treatments containing low-insulin and thyroxine at 0.5 or 2 {micro}g/ml increased (P<0.05) reactive oxygen species production from day 1 to day 7. Contrarily to high-insulin containing medium, the presence of thyroxine in low-insulin medium yielded higher stromal cell density (P<0.05). There were higher (P<0.05) estradiol production and Bcl2/Bax ratio in low-insulin versus high-insulin treatments on day 1 and 7, respectively. High levels of both insulin and thyroxine showed better follicular development (P<0.05), yielding great follicle and oocyte diameter. Finally, the high-insulin level led to insulin and thyroid receptors expression reduction as compared to non-cultured control. In conclusion, the combination of low concentrations of insulin and thyroxine better maintained follicle survival, while high levels ensured better follicular development.

physiology↗