Seascape Genetics of the Atlantic Spotted Dolphin (Stenella frontalis) Based on Mitochondrial DNA.

The Atlantic spotted dolphin (Stenella frontalis) is endemic to tropical, subtropical, and warm temperate waters of the Atlantic Ocean. Throughout its distribution, both geographic distance and environmental variation may contribute to population structure of the species. In this study, we follow a seascape genetics approach to investigate population differentiation of Atlantic spotted dolphins based on a large worldwide dataset and the relationship with marine environmental variables. The results revealed that the Atlantic spotted dolphin exhibits population genetic structure across its distribution based on mitochondrial DNA control region (mtDNA-CR) data. Analyses based on the contemporary landscape suggested, at both the individual and population level, that the population genetic structure is consistent with the isolation-by-distance model. However, because geography and environmental matrices were correlated, and because in some, but not all analyses, we found a significant effect for the environment, we cannot rule out the addition contribution of environmental factors in structuring genetic variation. Future analyses based on nuclear data are needed to evaluate whether local processes, such as social structure and some level of philopatry within populations, may be contributing to the associations among genetic structure, geographic, and environmental distance.

Cetaceans along the southeastern Brazilian coast: occurrence, distribution and niche inference at local scale.

It is deemed important to understand cetacean occurrence and distribution to comprehend their ecological roles. The geographical occurrence of species' niche can be used to better describe their potential distribution. The niche can be defined using environmental variables. Those variables are considered static and not affected by biological activities. The present study goal was to assess the occurrence and distribution of cetaceans along the southeastern Brazilian coast, as well as to define the fundamental and realized niche of each species and to investigate niche overlap at local scale. The environmental requirements for each species were also investigated throughout statistical tests. Sighting data were obtained through oceanographic surveys conducted between 2012 and 2015. The environmental variables available on MARSPEC and the software NicheA were used for the ecological niche modeling. A total of twelve cetacean species were identified and the potential distribution areas of the six commonest ones were defined. Even though the species presented different environmental preferences, most of them had partial overlap among niches and potential distribution areas. The environmental heterogeneity of the study area might support the co-occurrence of different species with different environmental requirements.

Endochitinase CHI2 of the biocontrol fungus Metarhizium anisopliae affects its virulence toward the cotton stainer bug Dysdercus peruvianus.

Chitinases have been implicated in fungal cell wall remodeling and play a role in exogenous chitin degradation for nutrition and competition. Due to the diversity of these enzymes, assigning particular functions to each chitinase is still ongoing. The entomopathogenic fungus Metarhizium anisopliae produces several chitinases, and here, we evaluate whether endochitinase CHI2 is involved in the pathogenicity of this fungus. We constructed strains either overexpressing or lacking the CHI2 chitinase. These constructs were validated by Southern, Northern and Western blot analysis, and chitinase production. To access the effects of CHI2 chitinase in virulence, the cotton stainer bug Dysdercus peruvianus was used as a host. CHI2 overexpression constructs showed higher efficiency in host killing suggesting that the production of this chitinase by a constitutive promoter reduces the time necessary to kill the insect. More significantly, the knock out constructs showed decreased virulence to the insects as compared to the wild type strain. The lack of this single CHI2 chitinase diminished fungal infection efficiency, but not any other detectable trait, showing that the M. anisopliae family 18, subgroup B endochitinase CHI2 plays a role in insect infection.

Evidence of alternative splicing of the chi2 chitinase gene from Metarhizium anisopliae.

Metarhizium anisopliae is a filamentous fungus used in the biological control of arthropods and produces several chitinases in order to break the host cuticle chitin fibers. Chitinase function during fungal cell development and/or infection processes is also an important aspect when analyzing the life cycle of entomopathogens. The expression profile analysis of the endochitinase chi2 gene acquired by RT-PCR experiments indicated the presence of two different transcripts, suggesting the occurrence of alternative splicing in the chi2 gene. The presence of two transcripts, characterized by the removal or retention of the second 72 bp intron, was further confirmed by DNA sequencing, Northern blot and qRT-PCR. Furthermore, we detected the synthesis of two different proteins from the transcripts by two-dimensional Western blot and mass spectrometry analyses. This is the first reported occurrence of alternative splicing in M. anisopliae.