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Hypostomus soniae is a small sized armored catfish endemic to the Tapajos River basin and ranked as one of the most exploited ornamental fish in the Santarem export marketplace. This study aims to evaluate distributional patterns of Hypostomus soniae and contribute to the species conservation in the face of development of the ornamental fish trade in the Amazon region. We compiled data associated with geographic coordinates in public repositories, supplemented with original field records. We compared our data to published records in the literature and museum collections to check for accuracy. To investigate the fishery and commercialization of H. soniae, we conducted interviews with ornamental fish stakeholders from the local trade. We also made direct observations in the fishing sites and export facilities in Santarem. A cluster analysis of the geolocation data was carried out to explore the spatial distribution patterns. The volume of captures and exportation of H. soniae decreased during the period 2020-2023. The occurrence of H. soniae was associated with annual rainfall ranging from 2,000 mm to 2,500 mm and concentrated in two municipalities of the State of Mato Grosso and two of the Para State. The species distribution area has been threatened, unfortunately, by fishermen who do not respect the laws that support artisanal fishing in the Amazon.

Many Amazonian fish' reproduction is associated to seasonality and to the conditions of habitat integrity. In a Neotropical floodplain lake of the Amazon region, the temporal structure of ichthyoplankton was investigated and the hypothesis that the density of fish eggs and larvae and the diversity of species vary between two areas with different levels of environmental changes occurred was tested. The sampling occurred monthly between September 2017 and August 2018. Six sampling stations were used, distributed in locations close to and far from the altered area. 195 eggs and 1,785 larvae from nine orders and 27 species were captured. The eggs were from non-migratory fish species and occurred during two moments. The larvae presented different abundance peaks during the sample months and all the initial stages of development occurred. Clupeiformes was the most abundant and Characiformes the species richest. The density of the ichthyoplankton and the diversity of species presented temporal variation. However, only the larval density varied between the areas of the lake. The Lake Juá is a spawning area for resident fish and is a nursery and growth area for larvae of species with different ecological categories and socioeconomic importance during different periods of the year.

Rhinella major is one of the component species of the Rhinella granulosa group and is distributed in the neotropical region of the South American continent, being found in anthropized environments. The occurrence of trypanosomes in anurans involves a yet unknown diversity of species and hosts. In the present study, we aimed to describe the first record of Trypanosoma sp. at R. major as a new host. Of the species captured, four were positive for trypomastigote forms of Trypanosoma sp. The morphometry of the trypomastigote forms revealed parasitemia by only one morphotype. There is a need for reports and studies of parasite-host relationships in anurans and a lack of records regarding hemoparasite diversity linked to the Rhinella granulosa group.

This study aimed to describe the occurrence, morphology and prevalence of Spirocamallanus krameri, a parasite of Hoplerythrinus unitaeniatus collected in state of Pará, Brazil. The morphological and morphometric characteristics are consistent with the species S. krameri, by having a hexagonal mouth opening, 16 cephalic papillae and two lateral papillae on the amphids. The buccal capsule is internally different in both sexes, with (11-13) spiral ridges in males and (13-17) spiral ridges in females. The basal ring is well developed, and three teeth are present in males and absent in females. Ten sessile caudal papillae and a pair of phasmidial pores occur in males. The spicules are small, subequal, 81-101 µm in length and the tail is tapered. The vulva in females is postequatorial, the tail is conical with lateral phasmidial pores. Among the species of Spirocamallanus that have short spicules, the general morphology of S. krameri most resembles that of S. inopinatus, but differs from that species, which have two cephalic teeth visible (absent in S. krameri) and specimens of S. inopinatus do not have sexual dimorphism in the buccal capsule of present in S. krameri.

The present study describes Trypanosoma spp. infection and blood parameters in Pterygoplichthys pardalis from the Tapajós River basin in eastern Amazon (Brazil). Of 32 fish examined, 40.6% were infected by Trypanosoma spp., while a total of 112 trypomastigotes were found. Two Trypanosoma morphotypes were characterized and compared with species described in literature infecting other Loricariidae, and a similarity of 94% was found with one species described for another host. The plasma glucose and aspartate aminotransferase levels, hematocrit, number of total erythrocytes, mean corpuscular volume (MCV) and mean corpuscular hemoglobin concentration (MCHC) in the infected and uninfected fish were similar, but hemoglobin was lower in fish infected with Trypanosoma spp. Hemoglobin levels declined with the abundance of the hemoparasites, but the condition factor was similar among fish infected and uninfected by Trypanosoma spp. This is the first study on the hemoparasitism by Trypanosoma spp. and blood parameters in P. pardalis.

The fires that occur in the Amazon are as damaging as the deforestation is. There is a need for further long-term studies on dynamics of tree communities in forests affected by fires. In the present study we evaluated the dynamics of tree species, before and after an accidental fire that occurred in 1997 in an experimental area of terra firme forest in the Floresta Nacional do Tapajós, in western Pará State, Brazil. Approximately 3500 trees with diameter measured at 1.30 m above ground (DBH) ≥ 5 cm were botanically identified and measured in 12 permanent plots of 0.25 ha (50 m x 50 m), in 1983, 1987, 1989, 1995, 2008 and 2012. Analyses of survival, mortality and recruitment of trees were performed. The results showed that although the fire has increased the mortality and recruitment rates after 15 years, the highest mortality occurred on trees with smaller diameters (DBH < 30 cm), so the fire did not affect the survival of large trees in the long term, explaining why the reduction in density of living trees has not greatly influenced the decrease in basal area in the burned forest.

The tambaqui, Colossoma macropomum, is the most popular fish species used for aquaculture in Brazil but there is no study comparing genetic variation among native and farmed populations of this species. In the present study, we analyzed DNA sequences of the mitochondrial DNA to evaluate the genetic diversity among two wild populations, a fry-producing breeding stock, and a sample of fish farm stocks, all from the region of Santarém, in the west of the Brazilian state of Pará. Similar levels of genetic diversity were found in all the samples and surprisingly the breeding stock showed expressive representation of the genetic diversity registered on wild populations. These results contrast considerably with those of the previous study of farmed stocks in the states of Amapá, Pará, Piauí, and Rondônia, which recorded only two haplotypes, indicating a long history of endogamy in the breeding stocks used to produce fry. The results of the two studies show two distinct scenarios of tambaqui farming in the Amazon basin, which must be better evaluated in order to guarantee the successful expansion of this activity in the region, and the rest of Brazil, given that the tambaqui and its hybrids are now farmed throughout the country.