Spatial Models of Abundance and Habitat Preferences of Commerson’s and Peale’s Dolphin in Southern Patagonian Waters

Funding: This research was possible with the support of the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). Funding for travel to and accommodation for NAD in Aberdeen, Scotland was provided by CONICET and Cetacean Society International. The work of NAD was part of a postdoctoral fellowship funded by CONICET. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewedPublisher PD

Feeding aggregation and aggressive interaction between bottlenose (Tursiops truncatus) and Commerson’s dolphins (Cephalorhynchus commersonii) in Patagonia, Argentina

We report the first recorded interactions between bottlenose dolphin (Tursiops truncatus) and Commerson’s dolphins (Cephalorhynchus commersonii). The diurnal behavioral patterns of bottlenose dolphins in Bahía Engaño, Argentina, were similar to those described for other coastal populations around the world. The majority of the feeding bouts were recorded near the mouth the Chubut River. When not feeding near the river, bottlenose dolphins generally swam along the coast, and interactions with Commerson’s dolphins were recorded very close to the shore on two occasions during a 3-year period. In the first event, both species were feeding on a fish school. The second interaction was aggressive in nature, involving one juvenile and three adult bottlenose dolphins with several Commerson’s dolphins. Two of the adult bottlenose dolphins attacked the Commerson’s dolphins. We propose that the observed behavior represented defense of the juvenile bottlenose dolphin.Fil: Coscarella, Mariano Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina. Universidad Nacional de la Patagonia. Facultad de Ciencias Naturales. Sede Puerto Madryn; ArgentinaFil: Crespo, Enrique Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina. Universidad Nacional de la Patagonia. Facultad de Ciencias Naturales. Sede Puerto Madryn; Argentin

Cardiac troponin T N-domain variant destabilizes the actin interface resulting in disturbed myofilament function

Missense variant Ile79Asn in human cardiac troponin T (cTnT-I79N) has been associated with hypertrophic cardiomyopathy and sudden cardiac arrest in juveniles. cTnT-I79N is located in the cTnT N-terminal (TnT1) loop region and is known for its pathological and prognostic relevance. A recent structural study revealed that I79 is part of a hydrophobic interface between the TnT1 loop and actin, which stabilizes the relaxed (OFF) state of the cardiac thin filament. Given the importance of understanding the role of TnT1 loop region in Ca2+ regulation of the cardiac thin filament along with the underlying mechanisms of cTnT-I79N-linked pathogenesis, we investigated the effects of cTnT-I79N on cardiac myofilament function. Transgenic I79N (Tg-I79N) muscle bundles displayed increased myofilament Ca2+ sensitivity, smaller myofilament lattice spacing, and slower crossbridge kinetics. These findings can be attributed to destabilization of the cardiac thin filament's relaxed state resulting in an increased number of crossbridges during Ca2+ activation. Additionally, in the low Ca2+-relaxed state (pCa8), we showed that more myosin heads are in the disordered-relaxed state (DRX) that are more likely to interact with actin in cTnT-I79N muscle bundles. Dysregulation of the myosin super-relaxed state (SRX) and the SRX/DRX equilibrium in cTnT-I79N muscle bundles likely result in increased mobility of myosin heads at pCa8, enhanced actomyosin interactions as evidenced by increased active force at low Ca2+, and increased sinusoidal stiffness. These findings point to a mechanism whereby cTnT-I79N weakens the interaction of the TnT1 loop with the actin filament, which in turn destabilizes the relaxed state of the cardiac thin filament

Patterns of geographic variation between mitochondrial and nuclear markers in Heaviside's (Benguela) dolphins ( Cephalorhynchus heavisidii

Supplementary material: Table S1 Summary of genetic variation based on 16 microsatellite loci in the Heaviside's dolphin: Ta stands for annealing temperature, bp for allele sizes, and Na represents the number of alleles examined within each putative population where observed (HO) and expected (HE) heterozygosities were estimated; n indicates the number of individuals used in calculations; dash (−) indicates loci which were not polymorphic, PI stands for Probability of Identity per locus, and PIsibs indicates Probability of Identity for genetic similarity among siblings per locus. Locus SCA22 did not amplify and loci Dde09 and Dde059 were monomorphic Table S2 Genetic variability estimates in mtDNA control region sequences excluding singletons (n = 27) for haplotype diversity (h) and nucleotide diversity (π) Table S3 Summary of genetic variation based on 13 microsatellite loci in the Heaviside's dolphin: Na indicates the number of alleles examined per each sampling site where observed (HO) and expected (HE) heterozygosities were estimated, HWE stands for Hardy‐Weinberg equilibrium; n indicates the number of individuals used in calculations, § denotes loci out of HWE (≤0.05) and ∗ indicates evidence for null allele. Locus SCA22 did not amplify and loci Dde09 and Dde059 were monomorphic Table S4 Sex‐biased dispersal results for males and females with respect to FIS, FST, HO, HS, mean assignment and variance assignment Table S5 Haplotype frequencies per sampling location of 51 haplotypes identified in biopsy samples of Heaviside's dolphins obtained at seven locations off the southwest African coast Table S6 STRUCTURE clustering analysis: a. Proportion of Heaviside's dolphin individuals from each of the seven sampling locations assigned to each of the two clusters inferred from STRUCTURE analysis Figure S1 Median‐joining network of mtDNA control region haplotypes without singletons for Heaviside's dolphins found off the southwest coast of southern Africa. Figure S2 Average posterior probability (ln K) for each of the seven clusters (i.e., K 1 to 7) from 15 independent runs. Figure S3 Log‐likelihood values (Ln Pr(X/K)) from 15 independent runs, where the ad hoc statistic delta K (ΔK) shows the most probable number of genetic clusters (K). Figure S4 Bayesian assignment probabilities where K = 6 clusters were inferred from STRUCTURE analysis. Two sampling sites, Hondeklipbaai and Port Nolloth, are grouped together as in the AMOVA results using mtDNA control region data. Each individual is represented by a thin vertical line, which is portioned into K coloured segments that represent the individual's estimated membership fractions in K clusters. Black lines separate individuals of different populations. The six putative populations are labelled below the figure.The Heaviside's (or Benguela) dolphin (Cephalorhynchus heavisidii) is endemic to the west coast of southern Africa. The present study investigated the population genetic structure across a large portion of the species distribution using mitochondrial control region and nuclear (microsatellite) markers. A total of 395 biopsy skin samples were analyzed; they were collected from free‐ranging Heaviside's dolphins in 7 locations along 1650 km of coast between Table Bay, South Africa and Walvis Bay, Namibia. Both genetic markers rejected the hypothesis of 1 homogenous population but revealed contrasting results in the genetic structuring of putative populations. Mitochondrial DNA suggested either 2 populations or a fine‐scale division with 6 (sub) populations, while microsatellite markers were indicative of 2 widespread populations with measurable gene flow between them. Neutrality tests and mismatch distribution of the mitochondrial sequences indicated a departure from mutation–drift equilibrium due to a population expansion at the 2 extremes of the geographic range, but not towards the middle of the distribution. These results highlight the importance of evaluating multiple genetic markers to gain reliable insights into population processes and structure.The National Research Foundation (NRF) of South Africa, the Kate Sanderson Bequest Fund administered by the Internation-al Union for Conservation of Nature (IUCN), the South African National Biodiversity Institute-Threatened Spe-cies Programme, the Andrew W. Mellon Foundation and the Rufford Small Grants Foundation.https://onlinelibrary.wiley.com/journal/174948772020-09-01hj2020Mammal Research Institut