Mercury in aquatic ecosystems of two indigenous communities in the Piedmont Ecuadorian Amazon: evidence from fish, water, and sediments.

Mercury is a highly toxic element present in water, soil, air, and biota. Anthropogenic activities, such as burning fossil fuels, mining, and deforestation, contribute to the presence and mobilization of mercury between environmental compartments. Although current research on mercury pathways has advanced our understanding of the risks associated with human exposure, limited information exists for remote areas with high diversity of fauna, flora, and indigenous communities.

New records of native and introduced fish species in a river basin of Western Ecuador, the Chocó-Darien Ecoregion, using DNA barcoding.

DNA barcoding, based on mitochondrial markers, is widely applied in species identification and biodiversity studies. The aim of this study was to establish a barcoding reference database of fishes inhabiting the Cube River from Western Ecuador in the Chocó-Darien Global Ecoregion (CGE), a threatened ecoregion with high diversity and endemism, and evaluate the applicability of using barcoding for the identification of fish species. Barcode sequences were obtained from seven orders, 17 families, 23 genera and 26 species, which were validated through phylogenetic analysis, morphological measurements, and literature review.

Validating the occurrence of the giant mottled eel (Anguilla marmorata) in the Galápagos Islands.

The giant mottled eel (Anguilla marmorata) is distributed mostly in the Indo-West Pacific. However, a few records indicate the presence of this eel in the Tropical Central and East Pacific. In April 2019, an eel specimen was caught in a small stream in San Cristobal Island, Galápagos.

Climate and sea surface trends in the Galapagos Islands.

The Galapagos Islands are a global hotspot of environmental change. However, despite their potentially major repercussions, little is known about current and expected changes in regional terrestrial climate variables and sea surface temperatures (SST). Here, by analysing existing meteorological observations and secondary datasets, we find that the Islands have warmed by about 0.

Conservation threats and future prospects for the freshwater fishes of Ecuador: A hotspot of Neotropical fish diversity.

Freshwater fish communities in Ecuador exhibit some of the highest levels of diversity and endemism in the Neotropics. Unfortunately, aquatic ecosystems in the country are under serious threat and conditions are deteriorating. In 2018-19, the government of Ecuador sponsored a series of workshops to examine the conservation status of Ecuador's freshwater fishes.

Visual pigment evolution in Characiformes: The dynamic interplay of teleost whole-genome duplication, surviving opsins and spectral tuning.

Vision represents an excellent model for studying adaptation, given the genotype-to-phenotype map that has been characterized in a number of taxa. Fish possess a diverse range of visual sensitivities and adaptations to underwater light, making them an excellent group to study visual system evolution. In particular, some speciose but understudied lineages can provide a unique opportunity to better understand aspects of visual system evolution such as opsin gene duplication and neofunctionalization.

Seeing the rainbow: mechanisms underlying spectral sensitivity in teleost fishes.

Among vertebrates, teleost eye diversity exceeds that found in all other groups. Their spectral sensitivities range from ultraviolet to red, and the number of visual pigments varies from 1 to over 40. This variation is correlated with the different ecologies and life histories of fish species, including their variable aquatic habitats: murky lakes, clear oceans, deep seas and turbulent rivers.

Visual adaptation could aid sympatric speciation in a deep crater lake.

Allopatric speciation was originally suggested to be the primary mechanism of animal speciation (Mayr, 1942; Figure 1). During allopatric speciation, populations diverge when gene flow is reduced across significant biogeographic barriers. Sympatric speciation, where species diverge while inhabiting the same location, was thought to be essentially impossible.

Color discrimination thresholds in a cichlid fish: .

Color vision is essential for animals as it allows them to detect, recognize and discriminate between colored objects. Studies analyzing color vision require an integrative approach, combining behavioral experiments, physiological models and quantitative analyses of photoreceptor stimulation. Here, we demonstrate, for the first time, the limits of chromatic discrimination in , a rock-dwelling cichlid from Lake Malawi, using behavioral experiments and visual modeling.

Diurnal variation in opsin expression and common housekeeping genes necessitates comprehensive normalization methods for quantitative real-time PCR analyses.

To determine the visual sensitivities of an organism of interest, quantitative reverse transcription-polymerase chain reaction (qRT-PCR) is often used to quantify expression of the light-sensitive opsins in the retina. While qRT-PCR is an affordable, high-throughput method for measuring expression, it comes with inherent normalization issues that affect the interpretation of results, especially as opsin expression can vary greatly based on developmental stage, light environment or diurnal cycles. We tested for diurnal cycles of opsin expression over a period of 24 hr at 1-hr increments and examined how normalization affects a data set with fluctuating expression levels using qRT-PCR and transcriptome data from the retinae of the cichlid Pelmatolapia mariae.

Variable vision in variable environments: the visual system of an invasive cichlid () in Lake Gatun, Panama.

An adaptive visual system is essential for organisms inhabiting new or changing light environments. The Panama Canal exhibits such variable environments owing to its anthropogenic origin and current human activities. Within the Panama Canal, Lake Gatun harbors several exotic fish species including the invasive peacock bass (), a predatory Amazonian cichlid.

Behavioral color vision in a cichlid fish: .

Color vision is the capacity to discriminate color regardless of brightness. It is essential for many fish species as they rely on color discrimination for numerous ecological tasks. The study of color vision is important because it can unveil the mechanisms that shape coloration patterns, visual system sensitivities and, hence, visual signals.

The opsin genes of amazonian cichlids.

Vision is a critical sense for organismal survival with visual sensitivities strongly shaped by the environment. Some freshwater fishes with a Gondwanan origin are distributed in both South American rivers including the Amazon and African rivers and lakes. These different habitats likely required adaptations to murky and clear environments.

Proximate and ultimate causes of variable visual sensitivities: Insights from cichlid fish radiations.

Animals vary in their sensitivities to different wavelengths of light. Sensitivity differences can have fitness implications in terms of animals' ability to forage, find mates, and avoid predators. As a result, visual systems are likely selected to operate in particular lighting environments and for specific visual tasks.

Sensory modalities in cichlid fish behavior.

Among teleosts, cichlids are a great model for studies of evolution, behavior, diversity and speciation. Studies of cichlid sensory systems have revealed diverse sensory capabilities that vary among species. Hence, sensory systems are important for understanding cichlid behavior from proximate and ultimate points of view.

Discovering Hidden Diversity of Characins (Teleostei: Characiformes) in Ecuador's Yasuní National Park.

Background: Management and conservation of biodiversity requires adequate species inventories. The Yasuní National Park is one of the most diverse regions on Earth and recent studies of terrestrial vertebrates, based on genetic evidence, have shown high levels of cryptic and undescribed diversity. Few genetic studies have been carried out in freshwater fishes from western Amazonia.