Trophic plasticity of tetra-fish, Psalidodon aff. fasciatus (Cuvier, 1819) (Characidae), in an Atlantic Forest stream of Northeast Brazil.

Trophic plasticity is a distinctive feature of freshwater fishes, representing an essential strategy for fish living in resource-variable environments. We analyzed the stomach contents of individuals sampled in two Atlantic Forest streams to identify the primary food sources consumed by Psalidodon aff. fasciatus and verify the existence of spatial, seasonal, and ontogenetic variations. The diet was determined by analyzing the stomach contents using the Volume Method to quantify the importance of food items. In general, Psalidodon aff. fasciatus was classified as an omnivorous species, consuming mainly insects, plant material, and filamentous algae. The results also showed significant effects for all factors considered (spatial, seasonal, and ontogenetic). Finally, Psalidodon aff. fasciatus demonstrated considerable trophic plasticity, which can result in better use of available resources in the environment and improved resource partitioning, reducing intraspecific and interspecific competition.

Body size predicts ontogenetic nitrogen stable-isotope (δ15N) variation, but has little relationship with trophic level in ectotherm vertebrate predators.

Large predators have disproportionate effects on their underlying food webs. Thus, appropriately assigning trophic positions has important conservation implications both for the predators themselves and for their prey. Large-bodied predators are often referred to as apex predators, implying that they are many trophic levels above primary producers. However, theoretical considerations predict both higher and lower trophic position with increasing body size. Nitrogen stable isotope values (δ15N) are increasingly replacing stomach contents or behavioral observations to assess trophic position and it is often assumed that ontogenetic dietary shifts result in higher trophic positions. Intraspecific studies based on δ15N values found a positive relationship between size and inferred trophic position. Here, we use datasets of predatory vertebrate ectotherms (crocodilians, turtles, lizards and fishes) to show that, although there are positive intraspecific relationships between size and δ15N values, relationships between stomach-content-based trophic level (TPdiet) and size are undetectable or negative. As there is usually no single value for 15N trophic discrimination factor (TDF) applicable to a predator species or its prey, estimates of trophic position based on δ15N in ectotherm vertebrates with large size ranges, may be inaccurate and biased. We urge a reconsideration of the sole use of δ15N values to assess trophic position and encourage the combined use of isotopes and stomach contents to assess diet and trophic level.

Endoparasitic helminth fauna and diet of Geophagus sveni (Pisces) in Upper Paraná River basin.

In freshwater ecosystems, parasite infection patterns are influenced by factors including spatial-temporal variations, host diet, and habitat. Fish often change diets, affecting their parasite communities. This study focused on non-native host fish Geophagus sveni, aiming to characterize diet and endoparasitic helminth fauna patterns in the invaded area, investigating spatial and seasonal possible differences of endoparasite infections and correlating with host diet, in São José dos Dourados River and Tietê River areas. The host fish were collected in these areas during the dry and rainy season using gillnets. The endoparasites were collected and preserved in alcohol and identified using taxonomic methods, and stomach contents were examined for diet analysis. Parasitism descriptors were calculated and evaluated spatially and seasonally by ANOVA and the Kruskal-Wallis tests. PERMANOVA assessed G. sveni diet differences, and RDA correlated the endohelminth abundance with the host diet. Two endoparasites were recorded: metacercariae of Austrodiplostomum compactum (Trematoda) and larvae and adults of Raphidascaris (Sprentascaris) lanfrediae (Nematoda). Spatial differences were observed for the mean abundance and prevalence of R. (S.) lanfrediae and A. compactum prevalence. Seasonal variations of parasitic descriptors occurred for the nematode in the Tietê River area. The detritus and aquatic insects were the most consumed items by G. sveni. Detritus consumption positively correlates with nematode abundance. The findings indicate that factors such as artificial channels and rainfall, which can influence resource availability, may affect the fish's diet and potentially influence the structure of its endoparasite community. The study emphasizes the importance of understanding trophic chain-transmitted parasites and calls for further research in Neotropical environments.

Feeding ecology of Moenkhausia collettii (Steindachner, 1882) (Characiformes: Characidae) in streams in the eastern Amazon: Environmental factors and body size.

The present study aimed to characterize the diet of Moenkhausia collettii and investigate possible changes due to environmental variations and its body size in streams in the eastern Amazon. The specimens were sampled monthly between April 2019 and March 2020. They were measured for standard length (SL) and total mass (Tm) and eviscerated for analysis of stomach contents. Food items were identified and grouped into categories. Dietary aspects such as food importance index (AI%), trophic niche width, and stomach repletion index (SRI%) were evaluated. Furthermore, generalized linear models (GLMs) were used to evaluate the relation between diet and the SL, as well as between diet and the environmental variables of streams. A total of 355 specimens with SL ranging from 11.06 to 46.03 mm and weight ranging from 0.020 to 2.373 g were evaluated. Out of the 355 stomachs analysed, 88 contained material in an advanced stage of decomposition and 12 were empty. The diet of M. collettii was considered omnivorous, with a tendency toward insectivory. Formicidae was the most important category in the diet of the species, followed by immature Diptera and plant material. The GLMs showed a relationship between the diet and a set of environmental variables such as dissolved oxygen, conductivity, flow, width, depth, wood, leaf bank, and SL. The trophic niche width and feeding intensity increased with the length of the species, as well as in the period of higher precipitation, reinforcing trophic opportunism for M. collettii. Therefore, new studies that combine the traditional method of stomach content analysis, the use of stable isotopes, as well as ecomorphological attributes, are crucial for a profound understanding of the trophic ecology of the ichthyofauna in the face of natural changes occurring in their environment.

The impact of chronic and acute problems on sea turtles: The consequences of the oil spill and ingestion of anthropogenic debris on the tropical semi-arid coast of Ceará, Brazil.

Sea turtle mortality is often related to materials that reach the coast from different anthropic activities worldwide. This study aimed to investigate whether sea turtle mortality was related to older marine problems, such as solid waste, or one of the largest oil spill accidents on the Brazilian coast, that occurred in 2019. We posed three questions: 1) Are there solid residues in the digestive tract samples, and which typology is the most abundant? 2) Can meso­ and macro-waste marine pollutants cause mortality? 3) Is the dark material found really oil? A total of 25 gastrointestinal content (GC) samples were obtained, of which 22 ingested waste of anthropogenic origin and 18 were necropsied. These 22 samples were obtained during or after the 2019 oil spill, of which 17 specimens were affected, making it possible to suggest oil ingestion with the cause of death in the animals that could be necropsied. Macroscopic data showed that the most abundant solid waste was plastic (76.05 %), followed by fabrics (12.18 %) and oil-like materials. However, chemical data confirmed only three specimens with oil levels ranging from remnants to high. It was possible to infer possible causes of death in 16 of the total 18 necropsied cases: Most deaths were due to respiratory arrest (62.5 %), followed by pulmonary edema (12.5 %), cachexia syndrome (12.5 %), circulatory shock (6.25 %), and head trauma (6.25 %), which may have been caused by contact with solid waste, oil, or both. The study showed that not all dark material found in the GCs of turtles killed in oiled areas is truly oil, and in this sense, a chemical analysis step to prove the evidence of oil must be added to international protocols.

Trophic ecology of Acestrorhynchus falcirostris Cuvier, 1819 in island lakes on the lower stretch of the Solimões River, Amazon Basin / Ecologia trófica de Acestrorhynchus falcirostris Cuvier, 1819 em lagos de ilha no trecho inferior do Rio Solimões, Bacia Amazônica

Abstract The aim objective of this study was to determine the trophic ecology of juvenile and adult Acestrorhynchus falcirostris during the rising and flood (high-water) period in six island lakes adjacent to the Solimões River. As such, we investigated: i) the trophic position, through the fractional trophic niche; ii) the niche breadth; iii) niche overlap and iv) the food strategy of the species. The specimens were collected during the years 2014 to 2017, using gillnets with mesh sizes ranging from 30 to 120mm between opposite knots. Through the analysis of stomach contents, the preference in the consumption of items of animal origin was observed. Juveniles consumed insects in greater proportions (IAi% = 50%), while adults consumed fish (IAi%=99,98%). Despite the large supply of food items available in the high-water period, juveniles were the only ones to consume items of allochthonous origin, such as insects. Juveniles presented a different dietary strategy and dietary composition to adults. Juveniles were omnivores with a generalist strategy, while adults were piscivores with a specialist strategy. Thus, the food composition, niche breadth, trophic position and feeding strategy of Acestrorhynchus falcirostris change due to the stage of development.

Resumo O objetivo deste estudo foi determinar a ecologia trófica de juvenis e adultos de Acestrorhynchus falcirostris durante o período de enchente e cheia em seis lagos de ilha adjacentes ao rio Solimões. Assim, investigamos: i) a posição trófica, através do nicho trófico fracional; ii) a largura de nicho; iii) sobreposição de nicho; iv) a estratégia alimentar. Os espécimes foram coletados durante os anos de 2014 a 2017, utilizando redes de emalhar com malha variando de 30 a 120mm entre nós opostos. Por meio da análise do conteúdo estomacal, observamos a preferência no consumo de itens de origem animal. Os juvenis consumiram insetos em maiores proporções (IAi% = 50%), enquanto os adultos consumiram preferencialmente peixes (IAi% = 99,98%). Apesar da grande oferta de alimentos disponíveis no período da cheia, os juvenis eram os únicos a consumir itens de origem alóctone, como por exemplo, os insetos. Os juvenis apresentaram uma estratégia alimentar e composição alimentar diferente para os adultos. Os juvenis foram considerados onívoros com uma estratégia generalista, enquanto os adultos foram considerados piscívoros com uma estratégia alimentar mais especialista. Assim, a composição alimentar, amplitude do nicho, posição trófica e a estratégia alimentar de Acestrorhynchus falcirostris muda em função do estágio de desenvolvimento.

Microplastics in stomach contents of juvenile Patagonian blennies (Eleginops maclovinus).

Microplastics are one of the major environmental issues that need to be addressed because they are starting to impact food chains and are also affecting human populations. The size, colour, form, and abundance of microplastics in young blennies of the species Eleginops maclovinus were examined in the current study. While the stomach contents of 70 % of the studied individuals contained microplastics, 95 % of them included fibres. Individual size and the largest particle size that can be eaten, which ranges between 0.09 and 1.5 mm present no statistical correlation. The quantity of particles taken in by each individual does not change with size. The most present microfibers colours were blue and red. Sampled fibres were analysed with FT-IR and no natural fibres were detected, proving the synthetic origin of the detected particles. These findings suggest that protected coastlines create conditions that favour the encounter of microplastics increasing local wildlife exposure to microplastics, raising the danger of their ingestion with potential physiological, ecological, economical and human health consequences.

The use of an alimentary index to assess anthropogenic debris on green turtles (Chelonia mydas).

Studies on novel methodologies addressed to quantification of anthropogenic marine debris (AMD) types ingested by green turtles (Chelonia mydas) is not common in the scientific literature. To fill this gap, we used the alimentary index (IAi) to quantify and classify AMD ingested by green turtles stranded in the Potiguar Basin, northeastern Brazil. We classified 295 green turtles as juveniles (JUV-I (n = 190) and JUV-II (n = 58)) and adults (ADU (n = 47)). We collected gut contents during necropsy and analyzed them using the IAi. The IAi values were categorized as main (IAi ≥ 0.5), secondary (0.25 ≤ IAi < 0.5), and accessory (IAi < 0.25). The results revealed that transparent soft plastic was an accessory item for the three size groups and the second most frequent item (IAi = 0.23) for JUV-I. Our study brings insights into the application of the IAi to evaluate the amount and types of AMD ingested by green turtles.

First assessment of debris pollution in the gastrointestinal content of juvenile Magellanic penguins (Spheniscus magellanicus) stranded on the west south Atlantic coasts.

This paper provides the first evidence of debris pollution, including plastic, in juvenile Magellanic penguins (Spheniscus magellanicus) found stranded on the Atlantic coast of southern Buenos Aires Province, Argentina. Macro-, meso- and microparticles of anthropogenic origin were observed in 100 % of the studied birds, with debris abundance ranging between 33 and 200 items/bird. Microparticles represented 91 % of the total debris and 97 % of them were fibers. Black particles were the most abundant (30 %), followed by transparent (26 %), blue (14 %), yellow (10.3 %), and red (10 %). Infrared and Raman spectroscopy identified 62.7 % of the total particles as plastics, with polypropylene (27.8 %) and polyester (21.6 %) being the most abundant polymers. Semi-synthetic cellulosic fibers, metallic particles, and pigments were also found. The presence of metallic microparticles was suggested for the first time in penguins. Stranded juvenile Magellanic penguins are proposed as promising bioindicators of plastic pollution in the South Atlantic.

Reinforcing the valuable role of gastric ultrasound for volume and content assessment: an observational study

Abstract Background Pulmonary aspiration is one of the most important complications in anesthesiology. Assessment of gastric content by ultrasound is a good method to quantify gastric volume and to determine the risk of intraoperative pulmonary aspiration. The aim of this study is to determine the accuracy of the gastric ultrasonography in the qualitative analysis of gastric content, mainly in the analysis of small amounts of liquid content. Methods Gastric ultrasound was performed to 36 patients before upper gastrointestinal endoscopy (UGI), making two longitudinal scans at the epigastric level, one in supine position and the other in right lateral decubitus position, measuring two diameters and the area of the gastric antrum and assessing the content characteristics determining whether it was an empty stomach or contained fluid or solid content. Subsequently, the ultrasound findings were compared with UGI findings. Results Gastric areas were analyzed by the trace and the lengths of the craniocaudal and anteroposterior axes concluding that there are no significant differences between the two methods. No statistically significant difference was found between UGI and US assessment technics. No statistically significant difference was found between the estimated volume by UGI and US. Conclusions Though our study has some limitations, qualitative analysis of gastric content using ultrasound followed by endoscopy enabled the conclusion that there are no differences in the qualitative assessment regarding these two techniques, supporting the important role of point-of-care gastric ultrasound (POCGUS) in the assessment of pulmonary aspiration risk by the anesthesiologist in the perioperative period.

Preoperative fasting for the infusion of "yerba mate": a randomized clinical trial with ultrasound evaluation of gastric contents

Abstract Background The traditional infusion of "yerba mate" is widely consumed in South America and exported to countries around the world. Although generally considered a "clear fluid", there is no data to date on the gastric emptying time of yerba mate and safe preoperative fasting intervals. The objective of this study was to evaluate the gastric emptying time of a standardized infusion of yerba mate using bedside ultrasound and compare it with the time confirm of hot and cold tea. Methods This was a prospective, randomized crossover experimental study. Thirty healthy volunteers were evaluated after 8 hours of fasting for both fluids and solids. Gastric antral area and gastric volume were evaluated at baseline and every 20 minutes after drinking 300 mL of randomly assigned infusion of "yerba mate", hot tea, or cold tea. Results The mean gastric emptying time was: 69.7 ± 22.1 min, 63.1 ± 14.5 min, and 64.3 ± 23.5 min for the mate, hot tea, and cold tea respectively. No significant differences were found in emptying time among the infusion groups (p-value = 0.043). When same time measures were compared, the only significant difference detected was between hot teas and mate infusion at 20 minutes (p-value = 0.012) Conclusion Yerba mate infusion has a similar gastric emptying time to that of tea. All subject's gastric volume returned to baseline values by 100 minutes. It is reasonable to recommend a similar fasting period of 2 hours for mate infusion prior to elective surgery.

Abyssal ascidians (Chordata, Tunicata) from the Weddell Sea, Antarctica, including a new Styela species and stomach content identifications.

Deep-sea benthic communities from the Weddell Sea, Antarctica, were sampled in JanuaryApril 2005 in an area located between 61S70S and 0W49W. We found a total of eight ascidian species that belong to five different families, of which one corresponded to a new species. These were: Protoholozoa pedunculata Kott, 1969; Corynascidia suhmi Herdman, 1882; Styela andeepensis Maggioni Tatin sp. nov.; Culeolus suhmi Herman, 1881; Culeolus anonymus Monniot F. Monniot C., 1976; Culeolus likae Sanamyan K. Sanamyan N., 2002; Oligotrema lyra (Monniot C. Monniot F., 1973) and Asajirus indicus (Oka, 1913). We report: the extension of the known distribution ranges of P. pedunculata, Corynascidia suhmi, Culeolus suhmi, C. likae and A. indicus, being the first time they are collected from the Weddell Sea; and the shallowest record of C. likae. Six species were added to the list of ascidians of the Weddell Sea, being all deep-sea representatives. While the total number of ascidian species augmented from 43 to 49, the number of deep-sea representatives increased from 23 to 29. Our findings, thus, reinforce the need of performing more deep-sea prospections in the area.

Preoperative fasting for the infusion of "yerba mate": a randomized clinical trial with ultrasound evaluation of gastric contents.

BACKGROUND: The traditional infusion of "yerba mate" is widely consumed in South America and exported to countries around the world. Although generally considered a "clear fluid", there is no data to date on the gastric emptying time of yerba mate and safe preoperative fasting intervals. The objective of this study was to evaluate the gastric emptying time of a standardized infusion of yerba mate using bedside ultrasound and compare it with the time confirm of hot and cold tea. METHODS: This was a prospective, randomized crossover experimental study. Thirty healthy volunteers were evaluated after 8 hours of fasting for both fluids and solids. Gastric antral area and gastric volume were evaluated at baseline and every 20 minutes after drinking 300 mL of randomly assigned infusion of "yerba mate", hot tea, or cold tea. RESULTS: The mean gastric emptying time was: 69.7 ± 22.1 min, 63.1 ± 14.5 min, and 64.3 ± 23.5 min for the mate, hot tea, and cold tea respectively. No significant differences were found in emptying time among the infusion groups (p-value = 0.043). When same time measures were compared, the only significant difference detected was between hot teas and mate infusion at 20 minutes (p-value = 0.012) CONCLUSION: Yerba mate infusion has a similar gastric emptying time to that of tea. All subject's gastric volume returned to baseline values by 100 minutes. It is reasonable to recommend a similar fasting period of 2 hours for mate infusion prior to elective surgery.

Trophic ecology of Acestrorhynchus falcirostris Cuvier, 1819 in island lakes on the lower stretch of the Solimões River, Amazon Basin.

The aim objective of this study was to determine the trophic ecology of juvenile and adult Acestrorhynchus falcirostris during the rising and flood (high-water) period in six island lakes adjacent to the Solimões River. As such, we investigated: i) the trophic position, through the fractional trophic niche; ii) the niche breadth; iii) niche overlap and iv) the food strategy of the species. The specimens were collected during the years 2014 to 2017, using gillnets with mesh sizes ranging from 30 to 120mm between opposite knots. Through the analysis of stomach contents, the preference in the consumption of items of animal origin was observed. Juveniles consumed insects in greater proportions (IAi% = 50%), while adults consumed fish (IAi%=99,98%). Despite the large supply of food items available in the high-water period, juveniles were the only ones to consume items of allochthonous origin, such as insects. Juveniles presented a different dietary strategy and dietary composition to adults. Juveniles were omnivores with a generalist strategy, while adults were piscivores with a specialist strategy. Thus, the food composition, niche breadth, trophic position and feeding strategy of Acestrorhynchus falcirostris change due to the stage of development.

Reinforcing the valuable role of gastric ultrasound for volume and content assessment: an observational study.

BACKGROUND: Pulmonary aspiration is one of the most important complications in anesthesiology. Assessment of gastric content by ultrasound is a good method to quantify gastric volume and to determine the risk of intraoperative pulmonary aspiration. The aim of this study is to determine the accuracy of the gastric ultrasonography in the qualitative analysis of gastric content, mainly in the analysis of small amounts of liquid content. METHODS: Gastric ultrasound was performed to 36 patients before upper gastrointestinal endoscopy (UGI), making two longitudinal scans at the epigastric level, one in supine position and the other in right lateral decubitus position, measuring two diameters and the area of the gastric antrum and assessing the content characteristics determining whether it was an empty stomach or contained fluid or solid content. Subsequently, the ultrasound findings were compared with UGI findings. RESULTS: Gastric areas were analyzed by the trace and the lengths of the craniocaudal and anteroposterior axes concluding that there are no significant differences between the two methods. No statistically significant difference was found between UGI and US assessment technics. No statistically significant difference was found between the estimated volume by UGI and US. CONCLUSIONS: Though our study has some limitations, qualitative analysis of gastric content using ultrasound followed by endoscopy enabled the conclusion that there are no differences in the qualitative assessment regarding these two techniques, supporting the important role of point-of-care gastric ultrasound (POCGUS) in the assessment of pulmonary aspiration risk by the anesthesiologist in the perioperative period.

Niche partitioning of two piscivorous fish species in a river in the western brazilian amazon / Particionamento de nicho de duas espécies de peixes piscívoros em um rio na amazônia ocidental brasileira

We analyzed the seasonal variation in the diet, trophic niche breadth (Levins index), the partitioning of food resources (Pianka's symmetric index) and trophic level (weighed average of trophic level of each prey determined in FishBase and SeaLifeBase platform) of Plagioscion squamosissimus (Heckel, 1840) and Hydrolycus scomberoides (Cuvier, 1819) in the Machado River, Rondônia, Brazil. Fish samplings were conducted bimonthly from June 2013 to May 2015 in five sites, using eight sets of gillnets. The occurrence frequency and volumetric frequency were used to quantify the food items. We analyzed the stomach contents of 283 individuals, 134 of H. scomberoides and 149 of P. squamosissimus. Fish were the most consumed food item by both piscivorous species. However, H. scomberoides mostly ingested pelagic fish (e.g. Characiformes fishes and Prochilodus nigricas Spix & Agassiz, 1829), while P. squamosissimus mostly consumed benthic fish [e.g. Pimelodus blochii Valenciennes, 1840 and Tenellus trimaculatus (Boulenger, 1898)]. Hydrolycus scomberoides presented the trophic level 3.55 for both periods analyzed, while P. squamosissimus 4.01 in the flood period and 3.82 in the drought period. Seasonal variations in the diet of H. scomberoides and P. squamosissimus were observed (PERMANOVA). Specifically, P. squamosissimus consumed mainly "Siluriformes" fishes and P. blochii in the drought period. The trophic niche breadth of P. squamosissimus was greater than that of H. scomberoides in the flood period. The species P. squamosissimus and H. scomberoides had low (0.35) food niche overlap in both seasons analysed. The data indicated that P. squamosissimus has a generalist feeding habit, while H. scomberoides is specialized in prey selection. The overlap of food niche between the species in both periods of the hydrological cycle was low, indicating that niche partitioning was probably the main mechanism of coexistence of these species, with little relationship with variations of the hydrological cycle.

Nós analisamos a variação sazonal na dieta, a amplitude do nicho trófico (Índice de Levins), a partição dos recursos alimentares (Índice simétrico de Pianka) e o nível trófico (média do nível trófico de cada presa determinada pela plataforma FishBase e SeaLifeBase) de Plagioscion squamosissimus (Heckel, 1840) e Hydrolycus scomberoides (Cuvier, 1819) no rio Machado, Rondônia, Brasil. As amostragens de peixes foram realizadas bimestralmente de junho de 2013 a maio de 2015 em cinco locais, utilizando oito conjuntos de redes de emalhar. A frequência de ocorrência e a frequência volumétrica foram utilizados para quantificar os itens alimentares. Analisamos o conteúdo estomacal de 283 indivíduos, 134 de H. scomberoides e 149 de P. squamosissimus. Peixes foram o item alimentar mais consumido pelas duas espécies piscívoras. No entanto, H. scomberoides ingeriu principalmente peixes pelágicos (ex. peixes Characiformes e Prochilodus nigricas Spix & Agassiz, 1829), enquanto P. squamosissimus consumiu principalmente peixes bentônicos [ex. Pimelodus blochii Valenciennes, 1840 e Tenellus trimaculatus (Boulenger, 1898)]. Hydrolycus scomberoides apresentou nível trófico de 3,55 para ambos os períodos analisados, enquanto para P. squamosissimus o nível trófico foi de 4,01 no período da cheia e 3,82 no período de seca. Variações sazonais na dieta de H. scomberoides e P. squamosissimus foram observadas (PERMANOVA). Especificamente, P. squamosissimus consumiu principalmente peixes "Siluriformes" e P. blochii no período de seca. A largura do nicho trófico de P. squamosissimus foi maior que a de H. scomberoides no período da cheia. Plagioscion squamosissimus e H. scomberoides apresentaram baixa (0,35) sobreposição de nicho alimentar nas duas estações analisadas. Os dados indicaram que P. squamosissimus tem hábito alimentar generalista, enquanto H. scomberoides é especializado na seleção de presas. A sobreposição de nicho alimentar entre as espécies em ambos os períodos do ciclo hidrológico foi baixa, indicando que a partição de nicho foi provavelmente o principal mecanismo de coexistência dessas espécies, com pouca relação com as variações do ciclo hidrológico.

Feeding strategy of the introduced Astronotus crassipinnis (Cichlidae) in upper Paraná river floodplain / Estratégia alimentar do introduzido Astronotus crassipinnis (Cichlidae) na planície de inundação do alto rio Paraná

The cichlid Astronotus crassipinnis (Heckel, 1840) known as "oscar" or "apaiari" is native to the Amazon basin and presents an omnivorous feeding habit, with a tendency to carnivory. The species was introduced in the upper Paraná River floodplain, where the trophic strategies adopted by the species are not well-known. The objective of this study was to characterize the diet of A. crassipinnis in different size classes to identify ontogenetic differences in diet composition and to determine its feeding behavior in the invaded floodplain. In addition, we experimentally compared the feeding behavior of A. crassipinnis with Hoplias sp. 2, a native piscivorous. We evaluated the predation rate of the two species with different prey (fish and shrimp). Astronotus crassipinnis consumed items from several trophic levels in the juvenile stage, characterizing an omnivore feeding. In the adult stage, A. crassipinnis displayed a specialist strategy in which fish and mollusks dominated the diet. Under controlled conditions, A. crassipinnis consumed more shrimp than Hoplias sp. 2. The preference for shrimp during the experiment contrasted to its feeding in natural environments, showing the potential trophic plasticity of A. crassipinnis. The piscivorous habit in the invaded environment can be considered a trophic strategy of A. crassipinnis, which feeds on an abundant resource in the upper Paraná River floodplain. In conclusion, the ontogenetic diet shifts and the trophic opportunism of the carnivore adults can be the strategies used by the species to invade and settle the floodplain. The piscivorous strategy of A. crassipinnis may impact fish biodiversity, altering ecosystem functioning.

Astronotus crassipinnis (Heckel, 1840), conhecido como "oscar" ou "apaiari", é nativo da bacia Amazônica e apresenta hábito alimentar onívoro, com tendência à carnivoria. A espécie foi introduzida na planície de inundação do alto rio Paraná, onde as estratégias tróficas adotadas pela espécie não são bem conhecidas. O objetivo deste estudo foi caracterizar a dieta de A. crassipinis em diferentes classes de comprimento para identificar diferenças ontogenéticas na composição da dieta e determinar seu comportamento alimentar na planície de inundação invadida. Em adição, nós comparamos experimentalmente o comportamento alimentar de A. crassipinnis com Hoplias sp. 2, um piscívoro nativo. Avaliamos a taxa de predação das duas espécies com presas diferentes (peixes e camarões). Astronotus crassipinnis consumiu itens de diferentes níveis tróficos no estágio juvenil, caracterizando uma alimentação onívora. No estágio adulto, A. crassipinnis apresentou uma estratégia especialista em que peixes e moluscos dominaram a dieta. Em condições controladas, A. crassipinnis consumiu mais camarões que Hoplias sp. 2. A preferência por camarão durante o experimento em contraste com sua alimentação em ambientes naturais evidencia a alta plasticidade trófica de A. crassipinnis. O hábito piscívoro no ambiente invadido pode ser considerado uma estratégia trófica de A. crassipinnis, que se alimenta de um recurso abundante na planície do alto Rio Paraná. Em conclusão, as mudanças ontogenéticas na dieta e o oportunismo trófico dos adultos podem ser as estratégias utilizadas pela espécie para invadir e colonizar a planície de inundação. A estratégia piscívora de A. crassipinnis pode impactar a biodiversidade de peixes, alterando o funcionamento do ecossistema.

Digestive system of Anourosorex squamipes - appearance and morphological features

Background: Anourosorex squamipes have a wide range of feeding habits, which is a kind of omnivorous animal. As an indispensable part of organisms, the differentiation degree of digestive system indicates the evolution degree of species. The higher the evolution degree of animals, the higher the differentiation of digestive system. At present, the research on Anourosorex squamipes digestive system mainly focuses on its feeding habits and mainly depends on the direct observation of gastric contents with the naked eye, but the research on the morphology of digestive system has not been reported. Materials, Methods & Results: Twenty adult Anourosorex squamipes were selected to investigate the characteristics of the appearance, including the contour parameters (body weight, body length, forefoot length, posterior foot length, nasal length, tail length), digestive system parameters (length of esophagus, intestinal length, intestinal weight, stomach weight and liver weight) and morphological structure of the small intestine by histological methods. The results showed that there were no significant differences in body weight, body length, forefoot length, posterior foot length, nasal length and tail length between males and females in Anourosorex squamipes, and no significant differences were observed in parameters of digestive system in length of esophagus, intestinal length, intestinal weight, stomach weight and liver weight. There were no significant differences in villus height, muscular layer thickness and villus height/recess depth (V/C) between males and females, but only ileal crypt depth decreased significantly in males. Discussion: Animal morphological characteristics are closely related to their life habits, unique organs and lifestyles ensure that they thrive on earth. In our study, we found that unique characters are found by observing the appearance of Anourosorex squamipes, the snout is blunt and short, the eyes are degenerated, and the tail is very short and covered with scales, which may be related to its feeding habits, the living environment-long-term nocturnal life in underground with minimal exposure to sunlight, and the unique tail can reduce the friction between tail and soil during the movement. There are certain differences in the appearance parameters of male and female Anourosorex squamipes, but are not significant. The esophagus, stomach, intestine, liver and other parameters of Anourosorex squamipes have little difference between males and females, indicating that Anourosorex squamipes don't have obvious distinctions between males and females in food intake. However, the liver weight of male Anourosorex squamipes is larger than female, indicating that the physiological metabolic capacity of male is larger than female. It is speculated that this may be related to the difference in the amount of activity between males and females in daily life. Males are more active and require more energy, but their digestion and absorption abilities are weaker than females. Therefore, the male Anourosorex squamipes needs more food to provide energy to meet the daily physiological metabolism, and the larger stomach capacity provides the essential conditions for the male to store more food. In addition, we found that the crypt depth of male Anourosorex squamipes is generally greater than that of females, especially in the ileal crypt depth, indicating that the female's cell maturation rate is greater than that of the male. It is speculated that the female has a greater demand for nutrient absorption and better digestion and absorption of food, because females need to give birth to offspring and require greater nutrition.

Trophic relationships among three species of ornamental fish from the region of Lake Amanã, Amazon / Relações tróficas entre três espécies de peixes ornamentais da região do lago de Amanã, Amazonas

The present study objectified to evaluate the trophic relationships and the possible aggressive mimicry involving Carnegiella strigata, Carnegiella marthae and Gnathocharax steindachneri, in lowland forest streams. Samplings occurred in November 2002, March and August 2003 in Amanã Sustainable Development Reserve (ASDR). The total of 943 fish was caught, being 79.43% of C. marthae, 3.18% of C. strigata and 17.39% of G. steindachneri. Stomach contents, degree of stomach repletion, relative volume and frequency of occurrence of food items were evaluated. Thirteen food items were identified, and the presence of terrestrial and aquatic insects indicates the high dependence of these species and the flooded forest. Low feeding overlap was observed between Carnegiella strigata and C. marthae compared to Gnathocharax steindachneri. However, the overlap between the two Carnegiella species was relatively high, which could explain the low frequency of syntopic occurrence among these species, suggesting a possible case of competitive exclusion.

Este estudo teve como objetivo analisar as relações tróficas e a possível existência de uma relação de mimetismo agressivo envolvendo Carnegiella strigata, Carnegiella marthae e Gnathocharax steindachneri, em igarapés de terra firme. As coletas ocorreram em novembro de 2002, março e agosto de 2003 e foram realizadas na Reserva de Desenvolvimento Sustentável de Amanã (RDSA). Foram capturados 943 peixes, onde C. marthae representou 79,43%, C. strigata 3,18% e G. steindachneri 17,39%. Foram analisados os conteúdos estomacais e verificados grau de repleção, volume relativo e frequência de ocorrência dos alimentos. Foram identificados 13 itens alimentares, onde insetos terrestres e aquáticos denotaram alto grau de dependência destas espécies em relação à floresta alagada. Ocorreu baixa sobreposição alimentar das espécies Carnegiella strigata e C. marthae em relação a Gnathocharax steindachneri. Entretanto, a sobreposição entre as duas espécies de Carnegiella foi relativamente alta, o que poderia explicar a baixa frequência de ocorrência sintópica entre essas espécies, sugerindo um possível caso de exclusão competitiva.

Seasonal analysis of food items and feeding habits of endangered riverine catfish Rita rita (Hamilton, 1822) / Análise sazonal de itens e hábitos alimentares de bagres ribeirinhos Rita rita (Hamilton, 1822) ameaçados de extinção

This investigation presents the food and feeding activity of and endangered riverine catfish Rita rita, during February 2017-January 2018. A total of 225 fish individuals was analyzed for stomach contents by characterizing the dominant food items and morphometric features. The results divulged ten major food items consumed, preferably fish scales and eggs, teleost fishes, copepods, cladocerans, rotifers, and mollusks. Total length and body weight of fish varied between 9-34 cm (20.53 ± 6.90 cm) and 10-400 g (9125.94 ± 102.07 g), respectively. The index of relative importance (IRI%) showed the importance of rotifers over the other food items. Morisita's index of diet overlap indicated seasonal variations in catfish diets with summer and monsoon displaying the least overlap, while maximum overlap during monsoon and winter seasons. The non-metric multidimensional scaling (nMDS) indicated the close association between the food items available during summer and winter seasons with a significant difference among the seasons (ANOSIM, R = 0.638, P = 0.013). Levin's niche breadth index arranged in the order of 0.88>0.81>0.78>0.63>0.43 for the size classes of V, IV, III, II and I, respectively. The PCA explained 95.39% of the total variance among the food items and fish size groups. Small-sized fish individuals displayed a greater correlation with food items suitable for their mouth size. In conclusion, the variety and frequency of food items recorded indicated considerable feeding plasticity and opportunistic feeding behavior with a shift from carnivorous to omnivorous feeding nature. This study could render useful information on the food and feeding habits of R. rita and provide background for preparing its diet for future aquaculture practices.

Esta investigação apresenta a alimentação e a atividade alimentar de bagres ribeirinhos Rita rita ameaçados de extinção, no período de fevereiro de 2017 a janeiro de 2018. Um total de 225 peixes foi analisado quanto ao conteúdo do estômago, caracterizando os itens alimentares dominantes e as características morfométricas. Os resultados apresentaram dez principais itens alimentares consumidos, preferencialmente escamas e ovos de peixes, teleósteos, copépodes, cladóceros, rotíferos e moluscos. O comprimento total e o peso corporal dos peixes variaram entre 9-34 cm (20,53 ± 6,90 cm) e 10-400 g (9125,94 ± 102,07 g), respectivamente. O índice de importância relativa (IRI%) mostrou a importância dos rotíferos sobre os demais itens alimentares. O índice de sobreposição de dieta de Morisita indicou variações sazonais nas dietas de bagres no verão e nas monções, exibindo a menor sobreposição, enquanto a sobreposição máxima ocorreu durante as estações das monções e do inverno. A escala multidimensional não métrica (nMDS) indicou a estreita associação entre os itens alimentares disponíveis durante o verão e o inverno, com uma diferença significativa entre as estações (ANOSIM, R = 0,638, P = 0,013). O índice de amplitude de nicho de Levin foi organizado na ordem de 0,88 > 0,81 > 0,78 > 0,63 > 0,43 para as classes de tamanho de V, IV, III, II e I, respectivamente. O PCA explicou 95,39% da variação total entre os itens alimentares e os grupos de tamanho de peixes. Peixes de pequeno porte apresentaram maior correlação com itens alimentares adequados ao tamanho da boca. Em conclusão, a variedade e a frequência dos itens alimentares registrados indicaram plasticidade alimentar considerável e comportamento alimentar oportunista, com uma mudança da natureza carnívora para onívora. Este estudo pode fornecer informações úteis sobre os hábitos alimentares e de alimentação de R. rita e apresentar subsídios para a preparação de sua dieta em futuras práticas de aquicultura.