DIETA DO BAGRE ESTUARINO Cathorops arenatus (VALENCIENNES, 1840) NA ILHA DE MAIANDEUA, PARÁ, BRASIL

Cathorops arenatus (Siluriformes: Ariidae) inhabits shallow waters and is abundant in the North coast of Brazil. Despite its local use and susceptibility to overexploitation and pollution, basic biological information is lacking to shape conservation actions. Thus, information on the feeding of C. arenatus in the North coast of Brazil are provided herein. Specimens were sampled in one expedition during the rainy season and in another in the dry season, using horizontal trawling along a 10-m line. Food contents of 68 specimens were analyzed. They exhibited 13 food items and fed mainly on Haparcticoida copepods and plant fragments. A high number of specimens exhibited sediment in their digestive tract. No differences in the diet composition between hydrological seasons were observed. C. arenatus exhibit a benthivorous feeding habit in the Amazonian estuary, which agrees with other species of the genus, and no temporal variation in its diet was found, which may be related to the community dynamics of its main prey.Keywords: Amazon estuary, Ariidae, trophic ecology.Cathorops arenatus (Siluriformes: Ariidae) habita águas rasas e é abundante na costa Norte do Brasil. Apesar da sua abundância, uso local e suscetibilidade à superexploração e poluição, informações biológicas básicas para nortear ações de conservação são escassas. Portanto, informações sobre a dieta de C. arenatus na região costeira Norte do Brasil são aqui apresentadas. Indivíduos foram amostrados em uma expedição na estiagem e em outra na estação chuvosa, utilizando arrastos horizontais na praia ao longo de 10m. O conteúdo alimentar de 68 espécimes foi analisado, que apresentou 13 itens alimentares e se alimentaram predominantemente de copépodos Haparcticoida e fragmentos de plantas superiores. Um alto número de espécimes apresentou sedimento em seus tratos digestivos. Não foram observadas diferenças na composição da dieta entre estações hidrológicas. C. arenatus exibiu hábitos alimentares bentívoros no estuário Amazônico, o que está de acordo com outras espécies do gênero, e variações temporais em sua dieta não foram encontradas, o que pode estar relacionado à dinâmica de comunidade de suas presas principais.Palavras-chave: Ariidae, ecologia trófica, estuário amazônico

Environmental predictors of the life history of the flag tetra Hyphessobrycon heterorhabdus (Characiformes: Characidae) in streams of the Eastern Amazon

Abstract This study aimed to characterize the reproductive biology of Hyphessobrycon heterorhabdus, and its response to environmental variations in the Eastern Amazon streams. We sampled specimens every two months, between March 2019 and January 2020. The population was evaluated for sex ratio, reproductive activity, growth pattern, condition factor, size at the first sexual maturation, spawning type, and fecundity. We analyzed 180 specimens, which showed a sex ratio of 1.6 males for each female across the whole period, with 2.3 males for each female during the period of greatest reproductive activity. The peak of reproductive activity coincided with higher precipitation periods and was partially predicted by factors such as water temperature, stream discharge, dissolved oxygen, substrate complexity, and electrical conductivity. The length where 50% and 100% of population to reach sexual maturity was 18.0 and 22.0 mm for males and 19.7 and 27.0 mm for females. The oocyte diameters showed a bimodal frequency, with at least two batches of oocytes. The average fecundity of 197 oocytes. The results indicate that this species presents an opportunistic strategy, and the tactics that make up this strategy depend on variations in both the physical structure of the habitat and physicochemical aspects of the water

Unexpected species diversity in electric eels with a description of the strongest living bioelectricity generator

Is there only one electric eel species? For two and a half centuries since its description by Linnaeus, Electrophorus electricus has captivated humankind by its capacity to generate strong electric discharges. Despite the importance of Electrophorus in multiple fields of science, the possibility of additional species-level diversity in the genus, which could also reveal a hidden variety of substances and bioelectrogenic functions, has hitherto not been explored. Here, based on overwhelming patterns of genetic, morphological, and ecological data, we reject the hypothesis of a single species broadly distributed throughout Greater Amazonia. Our analyses readily identify three major lineages that diverged during the Miocene and Pliocene—two of which warrant recognition as new species. For one of the new species, we recorded a discharge of 860 V, well above 650 V previously cited for Electrophorus, making it the strongest living bioelectricity generator. © 2019, The Author(s)

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear un derstanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5–7 vast areas of the tropics remain understudied.8–11 In the American tropics, Amazonia stands out as the world’s most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepre sented in biodiversity databases.13–15 To worsen this situation, human-induced modifications16,17 may elim inate pieces of the Amazon’s biodiversity puzzle before we can use them to understand how ecological com munities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple or ganism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region’s vulnerability to environmental change. 15%–18% of the most ne glected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lostinfo:eu-repo/semantics/publishedVersio