Highly divergent herpesviruses in threatened river dolphins from Brazil

River dolphins are a highly threatened polyphyletic group comprised of four odontocete families: Iniidae, Pontoporiidae, Lipotidae, and Platanistidae, the first two endemic to South America. To address the knowledge gap regarding infectious agents in this cetacean group, we surveyed the presence of herpesviruses by PCR in skin and/or blood samples of live-captured Amazon (Inia geoffrensis, n = 25) and Bolivian (Inia boliviensis, n = 22) river dolphins of the Amazon basin and in selected tissue samples of franciscanas (Pontoporia blainvillei, n = 27) stranded or bycaught in southeastern Brazil. Additionally, available franciscana tissue samples were examined by histopathology. Herpesvirus DNA was amplified in 13 Bolivian river dolphins (59.1%, 95% CI 38.5–79.6%) and 14 franciscanas (51.9%, 95% CI 33.0–70.7%). All Amazon river dolphins were herpesvirus-negative. Two different herpesviruses were found in Bolivian river dolphins: a previously known gammaherpesvirus detected in blood and/or skin samples of all positive individuals and a novel alphaherpesvirus in the skin of one animal. A new gammaherpesvirus was found in several franciscana samples—the first herpesvirus recorded in Pontoporiidae. Intranuclear inclusion bodies consistent with herpesvirus were observed in the lymph node of one franciscana. The high divergence among the obtained herpesviruses and those previously described can be explained by viral-host coevolution, and by the fact that these populations are fairly isolated.

Intrapopulation variation in the diet of franciscana dolphin (Pontoporia blainvillei) off southern Brazil

The franciscana dolphin (Pontoporia blainvillei) is a coastal dolphin endemic to the western South Atlantic Ocean. The dolphin is listed as vulnerable in the IUCN Red List, with incidental catches in gillnet fisheries the greatest conservation concern for this species. Insights into the feeding habits of this dolphin are essential to understand its distribution, movements and use of habitat, which are fundamental for effective management of the species. The feeding habits of franciscana dolphins were investigated from analyses of stomach contents of animals incidentally caught by two fishing operations from southern and northern regions of the southern Brazilian coast. In this study we investigate the existence of intrapopulation (sexual maturity and sex-related) variation in the diet of the franciscana dolphin, evaluating the spatial (northern and southern geographic areas) and seasonal influences. The analyses were based on Linear and Generalized Linear Models (LM and GLM). The majority of identified prey species were bottom-dwelling teleosts and the squid Doryteuthis sanpaulensis. The most important prey differed spatially and seasonally between northern and southern regions of the study area, and our results revealed significant differences between sexes and sexual maturity stages, mainly related to prey species sizes. This variation might indicate differences in prey selection, availability or habitat use patterns among these groups. In any case, these dietary differences are likely to minimize intraspecific competition for food resources, and/or indicate spatio-temporal variation in prey availability.

Uso de veículos aéreos não tripulados (VANT’s) para monitoramento de condição corporal de pequenos cetáceos sul americanos

Condição corporal em mamíferos pode ser interpretada como sua reserva energética, onde, melhor condição corporal está associada a maior sucesso reprodutivo e melhor eficiência em processos de termorregulação. A popularização dos veículos aéreos não tripulados (VANT’s ou drones), tornou possível monitorar condição corporal em cetáceos de vida livre, a partir de técnicas de fotogrametria aérea. Neste trabalho, um protocolo de fotogrametria aérea utilizando um drone, foi aplicado para estimar medidas morfométricas e de condição corporal em toninha (Pontoporia blainvillei, n = 122) e boto-cinza (Sotalia guianensis, n = 41), durante o inverno (julho / 2019) e verão (março / 2020), na Baía da Babitonga-SC. Um objeto de 115 cm, foi utilizado como escala para as medidas em pixel obtidas em diferentes altitudes (15-50 m). O modelo de calibração de escala considerando a altitude e variáveis ambientais (estado do mar e cobertura de nuvens) apresentou o melhor ajuste. Foram extraídas cinco medidas dos animais, comprimento do corpo, larguras na porção anterior a nadadeira peitoral, largura na região da axila, anterior a nadadeira dorsal e posterior a nadadeira dorsal (CC, AP, AX, AD, PD respectivamente). As larguras referentes às porções anteriores (AP, AX e AD) dos animais apresentaram maiores valores no inverno. O índice de condição corporal AD_CC, mostrou-se eficiente em monitorar variações sazonais na condição corporal das espécies estudadas, apresentando valores 1.1% superiores no inverno. As três categorias propostas para o índice AD_CC (“Abaixo”, “Média” e “Acima”), mostraram-se eficientes no monitoramento da condição corporal das espécies entre as classes de tamanho. A condição corporal “Média” foi a mais frequente para ambas as espécies estudadas e foi observada em todas as classes de tamanhos, enquanto a condição corporal “Abaixo” apresentou maior frequência no verão, ocorrendo apenas nas classes de tamanho superiores. O protocolo apresentado foi capaz de obter medidas morfométricas e de condição corporal precisas em ambas as espécies, destacando o potencial do uso de técnicas de fotogrametria aérea para monitorar padrões morfométricos e de condição corporal nas espécies de pequenos cetáceos estudados.

Low Genetic Diversity of the Endangered Franciscana (Pontoporia blainvillei) in Its Northernmost, Isolated Population (FMAIa, Espírito Santo, Brazil)

The franciscana, Pontoporia blainvillei, is the most endangered small cetacean in the Southwestern Atlantic Ocean, occurring from Itaúnas, Espírito Santo, Brazil to Chubut province, Argentina. This area is divided into four Franciscana Management Areas (FMA). The northern portion of this species distribution is not continuous and a previous genetic study using mitochondrial DNA (mtDNA) separated it into FMAIa (Espírito Santo state) and FMAIb (North of Rio de Janeiro state). In order to increase the information about this population we expanded the sample number and evaluated mitochondrial and nuclear DNA diversity. Samples of 68 franciscanas found stranded on beaches from 2005 to 2020 were analyzed. Analyses included 350 bp of the mtDNA control region (D-loop) and 12 microsatellite loci. We identified three control region haplotypes in FMAIa, two of them not previously observed in this population, one being a new haplotype. Haplotype and nucleotide diversities were 0.0408 and 0.00012 respectively, the lowest reported for all FMAs analyzed until now. The Neutrality tests were not significant and Mismatch Distribution analysis did not reject the hypothesis of population expansion. One of the microsatellite loci was monomorphic, and for the other loci, two to nine alleles were identified, with expected heterozygosities ranging from 0.306 to 0.801. No substructure was revealed and effective population size (Ne) was estimated in 117.9 individuals. Even with an increased sample size, the high mitochondrial genetic homogeneity suggested for the population in a previous study was confirmed. Among six loci previously analyzed in other franciscana populations, five showed the lowest observed heterozygosities for the Espírito Santo population. The novel microsatellite data also showed low genetic diversity and could not reject the hypothesis of a single, panmitic population along the coast of Espírito Santo. This species has been intensively impacted in the last years by incidental capture during fishing activities and habitat degradation, caused by pollution, coastal development and environmental disasters in FMAIa. Considering that this population is small, isolated, and with low levels of genetic diversity, we reinforce the necessity of different conservation actions, focusing mainly on the reduction of bycatch of this species in the region.