The Amazon River dolphin, Inia geoffrensis: What have we learned in the last two decades of research?

Silva, Vera Maria Ferreira da; Brum, Sannie M.; Mello, Daniela Magalhães Drummond de; Amaral, Rodrigo de Souza; Gravena, Waleska; Campbell, Elizabeth; Gonçalves, Rayane Da S.; Mintzer, Vanessa J.

doi:10.5597/lajam00298

Cited by 11 publications

(6 citation statements)

References 99 publications

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“…It is plausible that both dietary items and environmental metals dissolved in the waters of the Amazon basin could contribute to the exogenous pigmentation of the crown in tucuxis. Recent capture-release programmes have provided reference health parameters for Amazon River dolphins and tucuxis, including haematological chemistry and microbiological and parasitic infections (Mello et al, 2009(Mello et al, , 2021da Silva et al, 2023). However, those programmes are expensive to run and logistically challenging, particularly in the Amazon region.…”

Section: Discussionmentioning

confidence: 99%

“…Tucuxis and Amazon River dolphins are found in channels, lakes and rivers; however, Amazon River dolphins can also be observed within flooded forests and river rapids (Best & da Silva, 1989;Borobia et al, 1991). Amazon River dolphins and tucuxis are listed as Endangered by the IUCN Red List, with main threats related to hunting for bait, entanglement in fishing gear and modifications to their natural habitats such as damming of rivers and environmental pollution (da Silva et al, 2018(da Silva et al, , 2020(da Silva et al, , 2023. Density and abundance estimates for both species vary greatly between areas studied, and there are no estimates of total population size range-wide for either species (da Silva et al, 2018(da Silva et al, , 2020.…”

Section: Introductionmentioning

confidence: 99%

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Tooth wear and dental pathology in Amazon River dolphins (Inia geoffrensis) and tucuxis (Sotalia fluviatilis)

Loch,

Marmontel

2024

Lat. Am. J. Aquat. Mamm.

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The investigation of tooth wear and pathology in freshwater dolphins can increase our understanding of their life history, including interactions with the environment and impacts of disease and morbidity. This paper evaluated the occurrence, prevalence and discussed the putative etiology of dental wear and pathology in freshwater dolphins - tucuxi (Sotalia fluviatilis) and the Amazon River dolphin (Inia geoffrensis) - from the central Amazon basin. Teeth of 29 Amazon River dolphins and 14 tucuxis were visually inspected to identify wear facets and the presence of pathology. Dental wear was observed in 55% (n = 16) of the Amazon River dolphin and 79% (n = 11) of the tucuxi specimens. For both species, superficial wear restricted to the tooth crown was more frequent. Calculus deposits were observed in both species, occurring in 14% of tucuxi (n = 2) and 41% of Amazon River dolphin (n = 12) specimens. Caries-like lesions were observed in a third of Amazon River dolphin specimens (n = 10), affecting 10% of the teeth (n = 197). Gross caries was the most commonly caries type observed. Only one tucuxi had caries-like lesions, affecting 1.6% of the teeth (n = 13). While conditions such as tooth wear arise from normal physiological processes, severe wear and pathology such as caries and calculus can contribute to further disease development and morbidity, impacting the health of the animals. Further studies using materials from museum collections in other regions from the Amazon Basin will help elucidate the occurrence, etiology, and health impact of tooth wear and dental pathology in freshwater cetaceans, contributing to our growing understanding of their life history.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Tooth wear and dental pathology in Amazon River dolphins (Inia geoffrensis) and tucuxis (Sotalia fluviatilis)

Loch,

Marmontel

2024

Lat. Am. J. Aquat. Mamm.

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“…Also, L. vexillifer has been reported as having a wrinkled rugose enamel phenotype that is similar to I. geoffrensis [13]. The latter species is known to feed on hard-shelled river crabs (Poppiana) and river turtles (Podocnemis) and to cut large, armored fish and catfish into smaller pieces prior to swallowing [86][87][88]. Perhaps not surprisingly, there are no inactivating mutations in any of the seven enamel genes of L. vexillifer.…”

Section: Inactivating Mutations In Enamel Genesmentioning

confidence: 99%

Molecular Evidence for Relaxed Selection on the Enamel Genes of Toothed Whales (Odontoceti) with Degenerative Enamel Phenotypes

Randall,

Gatesy,

McGowen

et al. 2024

Genes

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Different species of toothed whales (Odontoceti) exhibit a variety of tooth forms and enamel types. Some odontocetes have highly prismatic enamel with Hunter-Schreger bands, whereas enamel is vestigial or entirely lacking in other species. Different tooth forms and enamel types are associated with alternate feeding strategies that range from biting and grasping prey with teeth in most oceanic and river dolphins to the suction feeding of softer prey items without the use of teeth in many beaked whales. At the molecular level, previous studies have documented inactivating mutations in the enamel-specific genes of some odontocete species that lack complex enamel. At a broader scale, however, it is unclear whether enamel complexity across the full diversity of extant Odontoceti correlates with the relative strength of purifying selection on enamel-specific genes. Here, we employ sequence alignments for seven enamel-specific genes (ACP4, AMBN, AMELX, AMTN, ENAM, KLK4, MMP20) in 62 odontocete species that are representative of all extant families. The sequences for 33 odontocete species were obtained from databases, and sequences for the remaining 29 species were newly generated for this study. We screened these alignments for inactivating mutations (e.g., frameshift indels) and provide a comprehensive catalog of these mutations in species with one or more inactivated enamel genes. Inactivating mutations are rare in Delphinidae (oceanic dolphins) and Platanistidae/Inioidea (river dolphins) that have higher enamel complexity scores. By contrast, mutations are much more numerous in clades such as Monodontidae (narwhal, beluga), Ziphiidae (beaked whales), Physeteroidea (sperm whales), and Phocoenidae (porpoises) that are characterized by simpler enamel or even enamelless teeth. Further, several higher-level taxa (e.g., Hyperoodon, Kogiidae, Monodontidae) possess shared inactivating mutations in one or more enamel genes, which suggests loss of function of these genes in the common ancestor of each clade. We also performed selection (dN/dS) analyses on a concatenation of these genes and used linear regression and Spearman’s rank-order correlation to test for correlations between enamel complexity and two different measures of selection intensity (# of inactivating mutations per million years, dN/dS values). Selection analyses revealed that relaxed purifying selection is especially prominent in physeteroids, monodontids, and phocoenids. Linear regressions and correlation analyses revealed a strong negative correlation between selective pressure (dN/dS values) and enamel complexity. Stronger purifying selection (low dN/dS) is found on branches with more complex enamel and weaker purifying selection (higher dN/dS) occurs on branches with less complex enamel or enamelless teeth. As odontocetes diversified into a variety of feeding modes, in particular, the suction capture of prey, a reduced reliance on the dentition for prey capture resulted in the relaxed selection of genes that are critical to enamel development.

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“…Nevertheless, only Inia geoffrensis has been assessed in the IUCN Red List, following the Society for Marine Mammalogy's Committee on Taxonomy that recognizes a single species with two subspecies (I. g. geoffrensis and I. g. boliviensis). Since 2018, Inia geoffrensis is considered endangered, facing several threats, and showing decreasing population number trends (da Silva et al, 2018b).…”

Section: Cetacea Odontoceti Family Iniidaementioning

confidence: 99%

Latin American aquatic mammals: an overview of 12 years focusing on molecular techniques applied to conservation

Castro

Caballero

Cunha

et al. 2023

Lat. Am. J. Aquat. Mamm.

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Ecological information useful for conservation purposes have benefitted from recent and rapid advancements in genetic techniques, revealing unknown aspects of behavior, natural history, population structure and demography of several aquatic mammal species, many of them with conservation concerns. Molecular markers have been used to define management units, to settle taxonomic uncertainties, to control illegal wildlife trade, among others, providing valuable information to decision-making to conserve and manage aquatic mammals. We review genetic studies applied to conservation-related issues involving natural populations of more than 40 species of aquatic mammals in Latin America, covering four taxonomic groups. The main goal was to assess which genetic approaches have been used and to identify gaps in genetic research relating to geographic areas and species. We reviewed studies published in peer-reviewed journals between 2011 and 2022, and found that most were focused on population structure, phylogeography, gene flow and dispersal movements. The review revealed that researchers need to increase and improve the knowledge in those species which face major conservation concern. Scarce findings were related to forensics and its application to wildlife trade. In the era of next-generation-sequencing techniques, just a few studies used genomics as a tool for monitoring gene diversity, an important goal to help us predict how species will cope with climate change events. Looking to the future we suggest which species, geographic areas and genetic studies should be prioritized in a scenario of climate change and increased human threats (e.g., fishery bycatch, habitat degradation, etc.) and the urgent need for conservation actions. Finally, we highlight the benefits of the collaborative works and the necessity of generating a conservation genetic network, with an open agenda to discuss the local and regional problematics. All in all, we strongly emphasize the generation of critical information towards the effective conservation and management of aquatic mammals in Latin America.

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The Amazon River dolphin, Inia geoffrensis: What have we learned in the last two decades of research?

Cited by 11 publications

References 99 publications

Tooth wear and dental pathology in Amazon River dolphins (Inia geoffrensis) and tucuxis (Sotalia fluviatilis)

Tooth wear and dental pathology in Amazon River dolphins (Inia geoffrensis) and tucuxis (Sotalia fluviatilis)

Molecular Evidence for Relaxed Selection on the Enamel Genes of Toothed Whales (Odontoceti) with Degenerative Enamel Phenotypes

Latin American aquatic mammals: an overview of 12 years focusing on molecular techniques applied to conservation

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