Monitoring fish communities through environmental DNA metabarcoding in the fish pass system of the second largest hydropower plant in the world.

The Itaipu Hydroelectric Power Plant is the second largest in the world in power generation. The artificial barrier created by its dam imposes an obstacle for fish migration. Thus, in 2002, a fish pass system, named Piracema Channel, was built to allow fish to access areas upstream of the reservoir. We tested the potential of environmental DNA metabarcoding to monitor the impact of both the dam and associated fish pass system in the Paraná River fish communities and to compare it with traditional monitoring methods. Using a fragment of the 12S gene, we characterized richness and community composition based on amplicon sequence variants, operational taxonomic units, and zero-radius OTUs. We combined GenBank and in-house data for taxonomic assignment. We found that different bioinformatics approaches showed similar results. Also, we found a decrease in fish diversity from 2019 to 2020 probably due to the recent extreme drought experienced in southeastern Brazil. The highest alpha diversity was recorded in the mouth of the fish pass system, located in a protected valley with the highest environmental heterogeneity. Despite the clear indication that the reference databases need to be continuously improved, our results demonstrate the analytical efficiency of the metabarcoding to monitor fish species.

Metagenomic analysis of the bacterial microbiota associated with cultured oysters (Crassostrea sp.) in estuarine environments.

In this work, we identified the bacterial microbiota associated with farmed oystersin estuarine regions of four states in the north eastern region of Brazil. During the drought and rainy seasons, for eight months, twenty oysters were sampled seasonally from seven different marine farms. In the laboratory, DNA extraction, amplification, and sequencing of the 16S rRNA gene were performed to establish the taxonomic units. We identified 106 genera of bacteria belonging to 103 families, 70 orders, 39 classes, and 21 phyla. Out of the total, 40 of the genera represented bacteria potentially pathogenic to humans; of these, nine are known to cause foodborne diseases and six are potentially pathogenic to oysters. The most prevalent genera were Mycoplasma, Propionigenium, Psychrilyobacter, and Arcobacter. The results indicate the need for more systematic monitoring of bacteria of the genus Mycoplasma in oyster farming operations in the Brazilian north eastern region. Currently, Mycoplasma is not one of the microorganisms analysed and monitored by order of Brazilian legislation during the oyster production and/or commercialization process, even though this genus was the most prevalent at all sampling points and presents pathogenic potential both for oysters and for consumers.

Molecular identification of blood meals in mosquitoes (Diptera, Culicidae) in urban and forested habitats in southern Brazil.

The study of host associations of mosquitoes (Diptera, Culicidae) provides valuable information to assist in our understanding of a variety of related issues, from their life-history to the entomological surveillance of pathogens. In this study, we identified and characterized mosquito blood meals from both urban and forested areas in the city of Paranaguá, state of Paraná, Brazil, by analyzing the amplification of host DNA ingested by mosquitoes under different storage conditions and digestion levels. Host DNA preservation was evaluated in fresh blood meals according to storage duration (30 to 180 days) and temperature (-20°C / -80°C) and, in digested blood, according the degree of digestion classified on the Sella scale. Molecular analysis of blood meals was based on DNA extraction and amplification of a fragment of the mitochondrial COI gene. We determined that, up to180 days of storage, the evaluated temperatures did not influence the preservation of fresh blood meals DNA, whereas the amplification success was increasingly reduced over the course of the digestion process. The species Anopheles cruzii, Aedes fluviatilis, Aedes scapularis, Psorophora ferox, Culex quinquefasciatus, Culex mollis, and Culex intrincatus, together with specimens representing four subgenera and one genus of Culicidae [Ae. (Ochlerotatus), Cx. (Culex), Cx. (Melanoconion), Cx. (Microculex), and Limatus, respectively] had their blood meals identified. Their diverse host use was evidenced by the identification of 19 species of vertebrate host, namely two amphibians, three mammals and 14 birds. Birds were the most commonly identified host in blood meals. These results not only show the diversity of mosquito hosts, but also underscore the challenges involved in monitoring arboviruses of public health importance, given potential combinations of host use for each mosquito species.

Recurrence analysis of ant activity patterns.

In this study, we used recurrence quantification analysis (RQA) and recurrence plots (RPs) to compare the movement activity of individual workers of three ant species, as well as a gregarious beetle species. RQA and RPs quantify the number and duration of recurrences of a dynamical system, including a detailed quantification of signals that could be stochastic, deterministic, or both. First, we found substantial differences between the activity dynamics of beetles and ants, with the results suggesting that the beetles have quasi-periodic dynamics and the ants do not. Second, workers from different ant species varied with respect to their dynamics, presenting degrees of predictability as well as stochastic signals. Finally, differences were found among minor and major caste of the same (dimorphic) ant species. Our results underscore the potential of RQA and RPs in the analysis of complex behavioral patterns, as well as in general inferences on animal behavior and other biological phenomena.

Emigration of a colony of the leaf-cutting ant Acromyrmex heyeri Forel (Hymenoptera, Formicidae) / Emigração de uma colônia da formiga cortadeira Acromyrmex heyeri Forel (Hymenoptera, Formicidae)

Emigration of a colony of the leaf-cutting ant Acromyrmex heyeri Forel (Hymenoptera, Formicidae). Colony migration is a poorly studied phenomenon in leaf-cutting ants. Here we report on the emigration of a colony of the leaf-cutting ant A. heyeri in Brazil. The colony emigrated to a new location 47.4 m away from the original nest site, possibly because it had undergone considerable stress due to competitive interactions with a colony of Acromyrmex crassispinus.

Emigração de uma colônia da formiga cortadeira Acromyrmex heyeri Forel (Hymenoptera, Formicidae). A migração de colônias de formigas cortadeiras é um fenômeno pouco estudado. Nesse estudo, nós relatamos a emigração de uma colônia da formiga cortadeira A. heyeri no Brasil. A colônia emigrou 47,5 m de distância do seu ninho original para um novo local, provavelmente porque sofreu um estresse considerável devido à interações competitivas com uma colônia de Acromyrmex crassispinus.

The effect of temperature and body size on filtration rates of Limnoperna fortunei (Bivalvia, Mytilidae) under laboratory conditions

The golden mussel (Limnoperna fortunei, Mollusca: Bivalvia) is an invasive species that has been causing considerable environmental and economic problems in South America. In the present study, filtration rates of L. fortunei were determined in the laboratory under different temperatures (10, 15, 20, 25, 28, and 30 ºC) and two types of food (Algamac-2000® and the chlorophycean alga Scenedesmus sp.). There was a statistically significant relationship between time and filtration rates in the experiment using Scenedesmus sp., regardless of temperature. However, this pattern was absent in the experiment using Algamac, suggesting that the relationship between filtration rates and temperature might depend on the size of the filtered particles. In addition, there was no correlation between filtration rates and either shell size or condition index (the relationship between the weight and the length of a mussel). The filtration rate measured in the present study (724.94 ml/h) was one of the highest rates recorded among invasive bivalves to date. Given that the colonies of the golden mussel could reach hundreds of thousands of individuals per square meter, such filtration levels could severely impact the freshwater environments in its introduced range.

Duration of the pre-settlement period of the mangrove crab Ucides cordatus (Decapoda: Ocypodidae) under laboratory conditions

The goal of the present study was to determine the most appropriate time to release the immatures of Ucides cordatus (Linnaeus) produced in the laboratory into the natural environments. Specifically, the time when the megalopae sought the mangrove sediment to excavate the burrows was determined, as well as the time necessary for their metamorphosis into the first juvenile stage. Results indicated that the megalopae of U. cordatus reared in the laboratory took three to ten days (median = 6) after their molt to excavated burrows in the sediment. The average time for the megalopae to molt into juveniles was 12.6 days (SD = 2.3).

O estágio de desenvolvimento em que se encontram as formas jovens de caranguejo produzidas em laboratório, no momento da sua liberação para o ambiente, é um fator chave para o sucesso dos trabalhos de repovoamento. O presente trabalho teve como objetivo determinar a idade mais adequada das formas jovens de U. cordatus, produzidas em laboratório, para sua liberação no ambiente natural. Especificamente, o momento em que as megalopas procuram o sedimento de mangue para escavar tocas foi determinado, assim como o tempo que demoram até realizarem a metamorfose para o primeiro estágio juvenil. O experimento indicou que as megalopas de U. cordatus produzidas em laboratório levam de 3 a 10 dias (mediana = 6) após a metamorfose até escavarem tocas no sedimento. O tempo médio que as megalopas levaram até realizar a metamorfose para o primeiro estágio juvenil foi de 12,6 dias (desvio padrão = 2,33).

Seasonal variation in larval density of Limnoperna fortunei (Bivalvia, Mytilidae) in the Iguaçu and Paraná rivers, in the region of Foz do Iguaçu, Paraná, Southern Brazil

The larval density of the invasive mussel Limnoperna fortunei (Bivalvia, Mytilidae) was monitored from January 2005 to February 2006 at two points along the Paraná and the Iguaçu Rivers, near Foz do Iguaçu, PR, Brazil. The results indicated two density peaks in the Paraná River: a lower peak between March and June and a higher peak in October. In the Iguaçu River, the values were much lower, yet they also showed a peak between September and October. A reduction in the reproductive activity was observed in both the rivers between July and August. The average larval density at the collection point in the Paraná reached 948.5 larvae/m³, with a peak of 2,999.5 larvae/m³ in October. The present study represented the first quantification of the larval density of L. fortunei in the lower reaches of the Iguaçu River, downstream of the Iguaçu falls.

A densidade larval do molusco invasor Limnoperna fortunei (Bivalvia, Mytilidae) foi monitorada entre janeiro de 2005 e fevereiro de 2006 em dois pontos dos rios Paraná e Iguaçu, na região de Foz do Iguaçu, PR. Os resultados registraram dois picos de densidade no rio Paraná: entre março e junho e um maior em outubro. No rio Iguaçu, os valores foram muito inferiores, mas também com um pico entre setembro-outubro. Em ambos os rios foi verificada uma pausa reprodutiva entre os meses de julho-agosto. A densidade média de larvas de L. fortunei no ponto amostrado no rio Paraná chegou a 948.5 larvas/m³, com pico de 2.999,5 larvas/m³ em outubro. O presente estudo representa a primeira quantificação da densidade larval de L. fortunei no rio Iguaçu, a jusante das Cataratas do Iguaçu.