ABSTRACT
Predatory mites of the Phytoseiidae family are important biological control agents. Many species of this family are omnivores, i.e., besides on prey, they can feed on plant resources such as nectar and pollen. It has been shown that the addition of alternative food for predators to a crop enhances biological control. However, factors such as food availability and quality can also affect interactions such as cannibalism, and thus influence biological control. We investigated the role of quality of the alternative food in the tendency of Amblyseius herbicolus to engage in cannibalism, a common ecological interaction in many phytoseiid mite species. Cannibalism on eggs by A. herbicolus was significantly reduced in the presence of high-quality food (cattail pollen) compared to egg cannibalism without alternative food, whereas this was not the case in the presence of low-quality food (cotton pollen). This suggests that cattail pollen is a high-quality alternative food, not only because it results in increased development and reproduction of predators, but also because it can minimize cannibalism.
Subject(s)
Cannibalism , Mites , Predatory Behavior , Animals , Pest Control, Biological , PollenABSTRACT
The introduction of nonnative species is one of the main threats to freshwater ecosystems. Although omnivory and intraguild predation are common in those systems, little is known about the effects of introduced omnivorous fish on pelagic and littoral communities. This study tested predictions of food-web theory regarding the effects of omnivorous fish introduction on previously fishless lakes in the Amazonian uplands of Serra dos Carajás, Pará, Brazil. The trophic structure of two similar lakes, one with and the other without the introduced omnivorous fish Astyanax bimaculatus, was compared using a data series of biotic variables collected from both lakes twice a year from 2010 to 2013. Zooplankton was more abundant in the lake with fish, and the zooplankton composition differed between lakes. Phytoplankton richness and chlorophyll-a were higher in the lake with the introduced fish than in the fishless lake regardless of phosphorus limitation. For the benthic macroinvertebrate communities, species richness and biomass were higher in the fishless lake. Our results also indicate that A. bimaculatus has the potential to link pelagic and littoral habitats through nutrient cycling. The differences observed between the studied lakes are consistent with predictions from food-web theory regarding the effects of multichain omnivorous fish on trophic dynamics. Despite limitations regarding replication at the ecosystem level, it is possible to infer from our findings that the introduction of an omnivorous fish might have changed lake overall functioning.(AU)
A introdução de espécies não nativas é uma ameaça aos ecossistemas de água doce. Embora a onivoria e a predação intraguilda sejam comuns nesses sistemas, os efeitos da introdução de peixes onívoros nas comunidades pelágicas e litorâneas é pouco conhecido. Nós testamos as previsões da teoria da teia trófica considerando os efeitos da introdução de um peixe onívoro em um lago previamente desprovido de peixes localizado na Serra dos Carajás, Pará, Brasil. A estrutura trófica em dois lagos similares, um com a presença do peixe onívoro introduzido Astyanax bimaculatus, e outro sem peixes, foi comparada através de uma série de dados bióticos amostrados entre 2010 e 2013. A comunidade zooplanctônica foi mais abundante no lago com peixe e sua composição diferiu entre os dois lagos. Apesar da limitação por fósforo no lago com peixe, a riqueza do fitoplâncton e a concentração de clorofila-a foram maiores nesse lago. A comunidade de macroinvertebrados bentônicos apresentou maior riqueza e biomassa no lago sem peixe. Nossos resultados também indicam que A. bimaculatus tem o potencial de acoplar as comunidades litorâneas e pelágicas através da reciclagem de nutrientes. Apesar das limitações relacionadas à ausência de replicação no nível de ecossistemas, nós argumentamos que o nosso estudo mostra que a introdução do peixe onívoro pode ter causado mudanças no funcionamento do lago.(AU)
Subject(s)
Animals , Introduced Species , Feeding Behavior , Fishes , Lakes/analysis , Biodiversity , Amazonian EcosystemABSTRACT
The introduction of nonnative species is one of the main threats to freshwater ecosystems. Although omnivory and intraguild predation are common in those systems, little is known about the effects of introduced omnivorous fish on pelagic and littoral communities. This study tested predictions of food-web theory regarding the effects of omnivorous fish introduction on previously fishless lakes in the Amazonian uplands of Serra dos Carajás, Pará, Brazil. The trophic structure of two similar lakes, one with and the other without the introduced omnivorous fish Astyanax bimaculatus, was compared using a data series of biotic variables collected from both lakes twice a year from 2010 to 2013. Zooplankton was more abundant in the lake with fish, and the zooplankton composition differed between lakes. Phytoplankton richness and chlorophyll-a were higher in the lake with the introduced fish than in the fishless lake regardless of phosphorus limitation. For the benthic macroinvertebrate communities, species richness and biomass were higher in the fishless lake. Our results also indicate that A. bimaculatus has the potential to link pelagic and littoral habitats through nutrient cycling. The differences observed between the studied lakes are consistent with predictions from food-web theory regarding the effects of multichain omnivorous fish on trophic dynamics. Despite limitations regarding replication at the ecosystem level, it is possible to infer from our findings that the introduction of an omnivorous fish might have changed lake overall functioning. (AU)
Subject(s)
Introduced Species , Biota , Fishes , Fresh WaterABSTRACT
This study evaluated the functional role of the highly generalist omnivore Melichthys niger in the remote St. Peter and St Paul's Archipelago (SPSPA), Brazil, where grazing herbivorous fishes are very scarce. We analysed patterns of distribution from zero to 30 m deep during three time intervals during the day and sampled different aspects of their feeding behaviour, including diel feeding rate, feeding substrate and diet. The density of M. niger increased with depth (26-30 m) and decreased by the end of the day. Although M. niger did not present a typical herbivore diel feeding pattern, they targeted the epilithic algal matrix as their primary feeding substrate, ingesting predominantly algae and detritus. The characteristic Caulerpa racemosa var. peltata from SPSPA was ingested only as detached fronds. We suggest that in the isolated SPSPA, the single species M. niger may perform a unique role as a link between benthic primary production and higher levels. Further studies on the trophic ecology of omnivorous species are necessary to better understand their roles in a reef system, especially in impoverished areas where they are likely to play a crucial role.
Subject(s)
Feeding Behavior , Fishes/physiology , Herbivory , Animals , Atlantic Ocean , Brazil , Diet , Ecology , IslandsABSTRACT
Detrital-based trophic cascades are often considered weak or absent in tropical stream ecosystems because of the prevalence of omnivorous macroconsumers and the dearth of leaf-shredding insects. In this study, we isolate top-down effects of three macroconsumer species on detrital processing in headwater streams draining Trinidad's northern mountains. We separated effects of different macroconsumers by experimentally manipulating their temporal access to isolated benthic habitat over the diel cycle. We found no evidence that omnivorous macroconsumers, including a freshwater crab (Eudaniela garmani) and guppy (Poecilia reticulata), increased leaf decomposition via consumption. By contrast, above a waterfall excluding guppies, the insectivorous killifish, Anablepsoides hartii, reduced the biomass of the leaf-shredding insect Phylloicus hansoni 4-fold, which consequently reduced leaf decomposition rates 1.6-fold. This detrital cascade did not occur below the barrier waterfall, where omnivorous guppies join the assemblage and reduce killifish densities; here killifish had no significant effects on Phylloicus or decomposition rates. These patterns of detrital processing were also observed in upstream-downstream comparisons in a landscape study across paired reaches of six streams. Above waterfalls, where killifish were present, but guppies absent, leaf decomposition rates and Phylloicus biomass were 2.5- and ~35-fold lower, respectively, compared to measurements below waterfalls. Moreover, the strength of top-down control by killifish is reflected by the 20- and 5-fold reductions in variability (±SE) surrounding mean Phylloicus biomass and leaf decomposition rates in upstream relative to downstream reaches where no top-down control was detected. Findings show a clear, detrital-based trophic cascade among killifish, a leaf-shredding insect, and leaf decomposition rates. Results also show how omnivorous guppies disrupt this cascade by depressing killifish densities, thereby releasing invertebrate shredders from predation, and significantly increasing decomposition rates. Moreover, this combination of direct and indirect trophic interactions drives patterns in decomposition rates in stream networks at a landscape scale, resulting in significantly lower rates of decomposition above vs. below barrier waterfalls. Our findings reveal that omnivory can result in significant indirect effects on a key ecosystem process, illustrating the importance of these hidden trophic pathways in detrital-based systems and suggesting that resource control in tropical systems may be even more complex than previously envisioned.
Subject(s)
Ecosystem , Poecilia , Animals , Biomass , Plant Leaves , Predatory Behavior , Trinidad and TobagoABSTRACT
OBJECTIVES: Invertebrate consumption is thought to be an integral part of early hominin diets, and many modern human populations regularly consume insects and other arthropods. This study examines the response of gut microbial community structure and function to changes in diet in wild white-faced capuchins (Cebus capucinus), a primate that incorporates a large proportion of invertebrates in its diet. The goal of the study is to better understand the role of both fruit and invertebrate prey consumption on shaping primate gut microbiomes. MATERIALS AND METHODS: Fecal samples (n = 169) and dietary data were collected over 12 months. The V3-V5 region of microbial 16S rRNA genes was amplified and sequenced. The IM-TORNADO pipeline was used to analyze sequences. RESULTS: White-faced capuchin gut bacterial communities were characterized primarily by Firmicutes (41.6%) and Proteobacteria (39.2%). There was a significant relationship between the invertebrate diet composition of individual capuchins and their gut microbiome composition. However, there was no relationship between the fruit diet composition of individual capuchins and their gut microbiome composition, even when examining multiple timescales. DISCUSSION: The results of our study indicate that there is a stronger relationship between gut microbial community structure and invertebrate diet composition than between gut microbial community structure and fruit consumption. As invertebrates and other animal prey play an important role in the diet of many primates, these results give important insight into the role of faunivory in shaping the evolution of host-microbe interactions in primates.
Subject(s)
Cebus/microbiology , Cebus/physiology , Feeding Behavior/physiology , Gastrointestinal Microbiome/physiology , Animals , Anthropology, Physical , Costa Rica , Feces/microbiology , Female , Fruit , Insecta , MaleABSTRACT
The aim of the present study was to test whether different degrees of human activity affect the diet of the Brazilian silverside Atherinella brasiliensis in two tropical estuaries. Fish were collected along the salinity gradient of two Brazilian estuaries, the heavily impacted Paraiba Estuary and the less impacted Mamanguape Estuary, in the dry and wet seasons. The findings confirm that A. brasiliensis has generalist feeding habits and is able to change its diet under different environmental conditions. The results indicate clear spatial (i.e. along the estuarine gradient) changes in diet composition in both estuaries, but diet was also influenced by the degree of anthropogenic disturbance. During the wet season in the nutrient enriched Paraiba Estuary, when human activity was higher, the diet of A. brasiliensis was poorer and dominated by few dietary items, reflecting the potential impoverishment of prey items in this heavily disturbed system. The specimens collected in the most affected estuary also had a greater frequency of micro-plastics and parasites in their stomachs, reflecting the greater degree of human disturbance in the estuary. The present findings suggest that the diet of A. brasiliensis could be a useful indicator of changes in the ecological quality of these and other tropical estuaries of the western Atlantic Ocean.
Subject(s)
Diet , Feeding Behavior/physiology , Human Activities , Smegmamorpha/physiology , Animals , Atlantic Ocean , Brazil , Environment , Estuaries , Gastrointestinal Contents , Humans , Salinity , Seasons , Tropical ClimateABSTRACT
Se evaluó la dieta de la lagartija de los gramadales Microlophus thoracicus icae en tres localidades del Valle del río Ica, Perú. La dieta de este saurio se caracterizó por un importante consumo de material vegetal, principalmente foliolos del árbol Prosopis spp., e invertebrados, especialmente insectos como hormigas y larvas de insectos. No se registraron relaciones significativas entre el tamaño corporal de los individuos y el número total de presas consumidos, ni el volumen total consumido. Los juveniles, hembras y machos de M. t. icae no presentaron diferencias significativas en el número de hormigas o larvas de insectos consumidos. Tampoco se registraron diferencias significativas en la proporción de material vegetal consumido por juveniles, hembras y machos. Sin embargo, el volumen de material vegetal consumido fue mayor para machos y hembras, comparado con juveniles. No se observan diferencias evidentes entre las dietas de juveniles, hembras y machos en el análisis multivariado. La amplitud del nicho trófico para M. t. icae fue de Bij = 6.97. El consumo de material vegetal e invertebrados es importante para juveniles y adultos de M. t. icae, por lo tanto, no se observa una marcada variación etaria en la dieta de los individuos evaluados. Esta especie de saurio presentaría una gran plasticidad en su dieta (omnívora) influenciada principalmente por la variación local de la oferta de los recursos alimenticios. Las posibles consecuencias del consumo de una dieta tan variada podrían incluir características particulares en sus endoparásitos, estrategias y eficiencia de forrajeo, termorregulación, morfología, entre otros.
The diet of grass lizard, Microlophus thoracicus icae, was evaluated in three localities of the Ica River Valley, Peru. The dietary pattern was characterized by high consumption of vegetable material, mainly Prosopis spp. leaves, and invertebrates as ants and insect larvae. No significant relationships were found between body size, number of prey eaten or volume consumed. The juvenile, male and female M. t. icae not showed significant differences regarding number of ants or insect larvae consumed, neither on the proportion consumed of plant material. However, total volume of plant material was different between males and females, compared to juveniles. Multivariate analysis showed no evident difference in the diets of juveniles, males and females. Trophic niche amplitude for M. t. icae was Bij = 6.97. The consumption of plant material and invertebrates is important for both juvenile and adult iguanas, therefore; no clear age difference in diet was observed in the individuals studied. This species would present great diet plasticity (omnivory) influenced by the local variation of food resources. Possible consequences of a varied diet may include particular characteristics of its parasites, foraging strategies and efficiency, thermoregulation, morphology, among others.
ABSTRACT
Tambaqui is the main native fish species farmed in Brazil and, due to their favorable husbandry characteristics, the culture of this species is continually increasing with economic importance. This review summarizes the current knowledge on nutrition and feeding of tambaqui in order to guide future studies in these areas of research. In the wild, tambaqui feeds according to the rainfall regime and morphophysiological adaptations allow the species to explore a wide variety of food items. There are many studies assessing protein and energy requirements of tambaqui, however, results differ significantly. In general, not much information is available on nutritional requirements or feeding of tambaqui in intermediate and final grow-out phases as well as for breeders and larvae. Most studies focus on tambaqui from 1 to 100 g. The majority of the feed ingredients tested are only locally available in small amounts, which limits their use by the feed industry. Further studies are required to assess the inclusion level and digestibility of feedstuffs with higher potential to feed tambaqui.
O tambaqui, principal espécie nativa cultivada no país, possui uma série de características zootécnicas favoráveis que justificam seu cultivo crescente e importância econômica para a piscicultura nacional. Esta revisão sumariza o conhecimento atual em nutrição e alimentação do tambaqui, a fim de orientar futuros estudos na área. Em ambiente natural, o tambaqui varia sua dieta de acordo com o regime de chuvas, apresentando adaptações morfofisiológicas que o permitem explorar uma ampla gama de itens alimentares. Existem diversos estudos avaliando as exigências em proteína e energia para a espécie, no entanto, observam-se grandes divergências entre os resultados obtidos. De forma geral, há uma carência de estudos de exigências nutricionais e manejo alimentar com animais na fase intermediária e final de engorda e com reprodutores e larvas, havendo uma concentração de estudos com tambaquis entre 1 e 100 g. A grande maioria dos alimentos testados para a espécie apresenta disponibilidade restritamente local e volume de produção insuficiente para sua incorporação pelas indústrias de ração, fazendo-se necessária a avaliação de ingredientes com maior potencial de utilização para a alimentação do tambaqui e estudos que investiguem a digestibilidade dos mesmos.
Subject(s)
Animals , Characidae , Diet , Nutrients , Animal FeedABSTRACT
Tambaqui is the main native fish species farmed in Brazil and, due to their favorable husbandry characteristics, the culture of this species is continually increasing with economic importance. This review summarizes the current knowledge on nutrition and feeding of tambaqui in order to guide future studies in these areas of research. In the wild, tambaqui feeds according to the rainfall regime and morphophysiological adaptations allow the species to explore a wide variety of food items. There are many studies assessing protein and energy requirements of tambaqui, however, results differ significantly. In general, not much information is available on nutritional requirements or feeding of tambaqui in intermediate and final grow-out phases as well as for breeders and larvae. Most studies focus on tambaqui from 1 to 100 g. The majority of the feed ingredients tested are only locally available in small amounts, which limits their use by the feed industry. Further studies are required to assess the inclusion level and digestibility of feedstuffs with higher potential to feed tambaqui.(AU)
O tambaqui, principal espécie nativa cultivada no país, possui uma série de características zootécnicas favoráveis que justificam seu cultivo crescente e importância econômica para a piscicultura nacional. Esta revisão sumariza o conhecimento atual em nutrição e alimentação do tambaqui, a fim de orientar futuros estudos na área. Em ambiente natural, o tambaqui varia sua dieta de acordo com o regime de chuvas, apresentando adaptações morfofisiológicas que o permitem explorar uma ampla gama de itens alimentares. Existem diversos estudos avaliando as exigências em proteína e energia para a espécie, no entanto, observam-se grandes divergências entre os resultados obtidos. De forma geral, há uma carência de estudos de exigências nutricionais e manejo alimentar com animais na fase intermediária e final de engorda e com reprodutores e larvas, havendo uma concentração de estudos com tambaquis entre 1 e 100 g. A grande maioria dos alimentos testados para a espécie apresenta disponibilidade restritamente local e volume de produção insuficiente para sua incorporação pelas indústrias de ração, fazendo-se necessária a avaliação de ingredientes com maior potencial de utilização para a alimentação do tambaqui e estudos que investiguem a digestibilidade dos mesmos.(AU)
Subject(s)
Animals , Characidae , Animal Feed , Diet , NutrientsABSTRACT
The Neotropical region presents a high number of freshwater fish species, whose capability to explore different kinds of food is particularly evident in reservoirs, and reflects a considerable feeding plasticity. Characiformes is the most diversified fish order in the region, and Anostomidae one of its most speciose families, evidencing Leporinus and its 80 valid species. Although its species are mainly considered omnivorous, some present herbivorous diet, and the food plasticity of the genus is a common feature in environments subject to a seasonal variation of water level. In the present work, the diet composition of Leporinus reinhardtii Lütken, 1875 in the Sobradinho reservoir and the influence of its seasonal water level variation is analyzed along a three-year period (2006-2009). Among the 876 individuals analyzed, 302 were collected in the dry phase, and 574 in the flooding phase. The diet was composed of 47 items, grouped into nine categories: Mollusks, Microcrustaceans, Insects, Insect (parts), Chironomidae, Plants, Seeds, Sediment and Others. Chironomidae represented a mean of 60% of total weight of all food categories, followed by Seeds with 25% and the remaining categories with less than 10%. In the flooding phase, Seeds prevailed in the diet in the lentic and transition stretches, Chironomidae was most represented in the lotic one, and the remaining categories represented less than 20% in all stretches at this phase. In the dry phase, the prevailing items differed, with a higher dominance of Insetcs in the lentic stretch, mainly Coleoptera, and Plants in the lotic one, with greater participation of aquatic macrophytes, filamentous algae, Chlorophyceae and the diatom Oscillatoria. In the transition stretch, Microcrustaceans dominated in the diet, differing from the other stretches. The diet of L. reinhardtii was characterized by low values of frequence of occurrence for all food categories (mostly inferior to 50%), and high relative abundance (>80%) of all categories. Niche breadth was restricted in the different stretches in both periods, somewhat higher during flooding, due to a greater item diversity, particularly in the lotic stretch. Leporinus reinhardtii presents an omnivorous habit with specialized behaviour in the Sobradinho reservoir, whose prevailing food categories in the diet depend on the reservoir level, as well as the environmental characteristics of each stretch, thus reflecting a narrow trophic niche breadth for the species.
A Região Neotropical possui um elevado número de espécies de peixes de água doce, cujas adaptações para explorar diferentes tipos de alimento é particularmente evidente em reservatórios, refletindo numa considerável plasticidade alimentar. Characiformes é a mais diversificada ordem de peixes da região, tendo Anostomidae como uma das famílias mais especiosas, com destaque para Leporinus, com cerca de 80 espécies válidas. Embora suas espécies sejam consideradas primordialmente onívoras, algumas apresentam dieta herbívora, e a plasticidade alimentar do gênero é uma característica comum em ambientes sujeitos a variação sazonal de nível da água. No presente trabalho, são analisadas a composição da dieta de Leporinus reinhardtii Lütken, 1875 no reservatório de Sobradinho e a influência da variação sazonal de seu nível sobre a mesma ao longo de três ciclos anuais (2006-2009). Dentre os 876 indivíduos analisados, 302 foram coletados no período de seca e 574 no de cheia. A dieta foi composta por 47 itens, agrupados em nove categorias: Moluscos, Microcrustáceos, Insetos, Insetos (partes), Chironomidae, Vegetais, Sementes, Sedimento e Outros. Chironomidae representou em média 60% do peso total das categorias alimentares, seguido de Sementes com 25% e as demais categorias com menos de 10%. No período de cheia, nos trechos lêntico e de transição, predominaram Sementes na dieta, tendo Chironomidae sido mais representativa no trecho lótico, e as demais categorias não ultrapassando 20% de participação nos três trechos neste período. No período de seca, houve diferença nos itens predominantes, com predominância de Insetos no trecho lêntico, principalmente Coleoptera, e de Vegetais no lótico, com maior participação de macrófitas aquáticas, algas filamentosas, clorofíceas e da diatomácea Oscillatoria. Já no trecho de transição, Microcrustáceos dominaram na dieta, diferindo dos demais trechos. A dieta de L. reinhardtii se caracterizou por baixos valores de frequência de ocorrência de todas as categorias alimentares (predominantemente inferiores a 50%) e elevada abundância relativa (>80%) de diferentes categorias. A amplitude de nicho foi restrita nos diferentes trechos nos dois períodos, sendo ligeiramente mais elevada na cheia, devido à maior diversidade de itens, em particular no trecho lêntico. Leporinus reinhardtii possui hábito onívoro com comportamento especialista no reservatório de Sobradinho, cujas categorias predominantes da dieta dependem do regime hidrológico do reservatório e das características ambientais de cada trecho, refletindo numa amplitude restrita de nicho trófico para a espécie.
Subject(s)
Animals , Diet , Fishes , HydrologyABSTRACT
The Neotropical region presents a high number of freshwater fish species, whose capability to explore different kinds of food is particularly evident in reservoirs, and reflects a considerable feeding plasticity. Characiformes is the most diversified fish order in the region, and Anostomidae one of its most speciose families, evidencing Leporinus and its 80 valid species. Although its species are mainly considered omnivorous, some present herbivorous diet, and the food plasticity of the genus is a common feature in environments subject to a seasonal variation of water level. In the present work, the diet composition of Leporinus reinhardtii Lütken, 1875 in the Sobradinho reservoir and the influence of its seasonal water level variation is analyzed along a three-year period (2006-2009). Among the 876 individuals analyzed, 302 were collected in the dry phase, and 574 in the flooding phase. The diet was composed of 47 items, grouped into nine categories: Mollusks, Microcrustaceans, Insects, Insect (parts), Chironomidae, Plants, Seeds, Sediment and Others. Chironomidae represented a mean of 60% of total weight of all food categories, followed by Seeds with 25% and the remaining categories with less than 10%. In the flooding phase, Seeds prevailed in the diet in the lentic and transition stretches, Chironomidae was most represented in the lotic one, and the remaining categories represented less than 20% in all stretches at this phase. In the dry phase, the prevailing items differed, with a higher dominance of Insetcs in the lentic stretch, mainly Coleoptera, and Plants in the lotic one, with greater participation of aquatic macrophytes, filamentous algae, Chlorophyceae and the diatom Oscillatoria. In the transition stretch, Microcrustaceans dominated in the diet, differing from the other stretches. The diet of L. reinhardtii was characterized by low values of frequence of occurrence for all food categories (mostly inferior to 50%), and high relative abundance (>80%) of all categories. Niche breadth was restricted in the different stretches in both periods, somewhat higher during flooding, due to a greater item diversity, particularly in the lotic stretch. Leporinus reinhardtii presents an omnivorous habit with specialized behaviour in the Sobradinho reservoir, whose prevailing food categories in the diet depend on the reservoir level, as well as the environmental characteristics of each stretch, thus reflecting a narrow trophic niche breadth for the species.(AU)
A Região Neotropical possui um elevado número de espécies de peixes de água doce, cujas adaptações para explorar diferentes tipos de alimento é particularmente evidente em reservatórios, refletindo numa considerável plasticidade alimentar. Characiformes é a mais diversificada ordem de peixes da região, tendo Anostomidae como uma das famílias mais especiosas, com destaque para Leporinus, com cerca de 80 espécies válidas. Embora suas espécies sejam consideradas primordialmente onívoras, algumas apresentam dieta herbívora, e a plasticidade alimentar do gênero é uma característica comum em ambientes sujeitos a variação sazonal de nível da água. No presente trabalho, são analisadas a composição da dieta de Leporinus reinhardtii Lütken, 1875 no reservatório de Sobradinho e a influência da variação sazonal de seu nível sobre a mesma ao longo de três ciclos anuais (2006-2009). Dentre os 876 indivíduos analisados, 302 foram coletados no período de seca e 574 no de cheia. A dieta foi composta por 47 itens, agrupados em nove categorias: Moluscos, Microcrustáceos, Insetos, Insetos (partes), Chironomidae, Vegetais, Sementes, Sedimento e Outros. Chironomidae representou em média 60% do peso total das categorias alimentares, seguido de Sementes com 25% e as demais categorias com menos de 10%. No período de cheia, nos trechos lêntico e de transição, predominaram Sementes na dieta, tendo Chironomidae sido mais representativa no trecho lótico, e as demais categorias não ultrapassando 20% de participação nos três trechos neste período. No período de seca, houve diferença nos itens predominantes, com predominância de Insetos no trecho lêntico, principalmente Coleoptera, e de Vegetais no lótico, com maior participação de macrófitas aquáticas, algas filamentosas, clorofíceas e da diatomácea Oscillatoria. Já no trecho de transição, Microcrustáceos dominaram na dieta, diferindo dos demais trechos. A dieta de L. reinhardtii se caracterizou por baixos valores de frequência de ocorrência de todas as categorias alimentares (predominantemente inferiores a 50%) e elevada abundância relativa (>80%) de diferentes categorias. A amplitude de nicho foi restrita nos diferentes trechos nos dois períodos, sendo ligeiramente mais elevada na cheia, devido à maior diversidade de itens, em particular no trecho lêntico. Leporinus reinhardtii possui hábito onívoro com comportamento especialista no reservatório de Sobradinho, cujas categorias predominantes da dieta dependem do regime hidrológico do reservatório e das características ambientais de cada trecho, refletindo numa amplitude restrita de nicho trófico para a espécie.(AU)
Subject(s)
Animals , Diet , Fishes , HydrologyABSTRACT
Effect of gossypol on survival and reproduction of the zoophytophagous stinkbug Podisus nigrispinus (Dallas). Gossypol is a sesquiterpene aldehyde found in cotton plants conferring resistance against herbivory. Although the effect of this sesquiterpenoid on insect pests of cotton is known, the interaction of this compound with zoophytophagous predators such as Podisus nigrispinus (Dallas) (Hemiptera, Pentatomidae) has not been studied so far. Thus, the objective of this study was to evaluate the effect of the purified gossypol on nymphs and adults of P. nigrispinus. Nymphs and adults of this predator were fed on Tenebrio molitor pupae and supplemented with solutions of gossypol at concentrations of 0.00, 0.05, 0.10, and 0.20 percent (w/v) during the nymphal and adult stages or, only during the adult stage of P. nigrispinus. The nymphal stage of the predator was, on average, two days longer when suplemmented with gossypol. Emerged adults had lower fecundity and egg hatching, especially at the highest gossypol concentration (0.20 percent) ingested during the nymphal and adult stages. However, this predator was not affected when it ingested the compound only during the adult stage. P. nigrispinus can have delayed nymphal development and lower reproductive performance when ingesting the gossypol during the nymphal and adult stages, but only at higher concentrations of gossypol than that produced by cotton plants.
Efeito do gossipol na sobrevivência e reprodução do percevejo zoofitófago Podisus nigrispinus (Dallas). O gossipol é um aldeído sesquiterpeno produzido pelo algodoeiro que confere resistência contra a herbivoria. A interação deste sesquiterpeno com predadores zoofitófagos, como Podisus nigrispinus (Dallas) (Hemiptera, Pentatomidae), é inexistente apesar do reconhecido efeito do gossipol sobre insetos pragas do algodoeiro. Assim, este estudo avaliou o efeito do extrato de gossipol sobre ninfas e adultos de P. nigrispinus. O predador foi alimentado com pupas de Tenebrio molitor L. (Coleoptera, Tenebrionidae) e suplementado com soluções do gossipol nas concentrações 0, 0,05, 0,10 e 0,20 por cento (peso/volume) durante os estágios ninfal e adulto e somente durante o estágio adulto. A duração do estágio ninfal do predador foi em média dois dias mais longo quando suplementado com gossipol. Adultos oriundos de ninfas suplementadas com gossipol apresentaram menor fecundidade e viabilidade dos ovos, em especial na maior concentração (0,20 por cento). Contudo, adultos não foram afetados quando suplementados com gossipol somente durante este estágio. Os resultados demonstram que a ingestão prolongada do gossipol ocasiona efeito no desenvolvimento e reprodução do predador P. nigrispinus, porém somente em concentração superior àquela produzida naturalmente pela planta de algodão.
ABSTRACT
Food webs usually display an intricate mix of trophic interactions where multiple prey are common. In this context omnivory has been the subject of intensive analysis regarding food web stability and structure. In a three species omnivory setting it is shown that the modeling of prey preference by the top predator may exert a strong influence on the short as well as on the long term dynamics of the respective food web. Clearly, this has implications concerning the stability and the structure of omnivory systems under disturbances such as nutrient enrichment.
Redes tróficas apresentam geralmente uma variada rede de interações onde múltiplas presas são comuns. Neste contexto, a onivoria vem sendo objeto de intensas análises à luz da estabilidade e estrutura do sistema. A modelagem do termo de preferência pelo predador de topo sobre suas presas pode exercer uma forte influência sobre as dinâmicas transiente e de longo prazo em uma rede trófica onívora composta por três espécies. Claramente, isto tem implicações sobre a estrutura e estabilidade do sistema sob distúrbios tais como o enriquecimento por nutrientes.
Subject(s)
Animals , Ecosystem , Food Chain , Models, Biological , Predatory Behavior , Food PreferencesABSTRACT
Amazonian biodiversity is notorious, this is also valid for the fauna of the mineral-deficient waters of the Rio Negro System. Some 25 years of research on the benthic fauna of Central Amazonian streams resulted in species-rich foodwebs with a high degree of omnivory within dense animal communities. To exemplify the taxonomic range of omnivorous consumers, the detailed resource spectra of 18 consumer species, including Protozoa (2 species), Platyhelminthes (1 species), insects (2 species), fish (6 species) and shrimps (Decapoda, 7 species), associated primarily with the benthic habitats of Rio Negro tributaries, are presented. Special features of omnivory are characterized, and the importance of litter-decomposing fungi as essential energy input into the foodwebs is documented. It is shown that general omnivory -diverse omnivore consumers sharing most of the resource types- is a prevalent feature. The relevance of this general omnivory for the maintenance of biodiversity is discussed.
A biodiversidade do Amazonas é notório e isto também é válido para as águas pobres em nutrientes da bacia do Rio Negro. Uma pesquisa de 25 anos da fauna béntica de igarapés da Amazônia Central resultou em redes alimentares caraterizadas por alta diversidade de espécies, por intensa omnivoria e por alta densidade populacional. Para demonstrar a generalidade taxonômica de omnivoria no bentos dos igarapés, são apresentados as listas de presas / recursos de 18 espécies de consumidores, sendo Protozoa (2 epécies), Platyhelminthes (1 espécie), insetos (2 espécies), peixes (6 espécies) e camarões (Decapoda, 7 espécies). Diferentes categorias de omnivoria são apresentados, e a importância de fungos decompositores da liteira submersa como input básico de energia nas redes alimentares é demonstrada. É prevalente a omnivoria geral, sendo que as diferentes espécies omnívoros estão utilizando os mesmos recursos. Considera- se a relevância desta omnivoria geral para a manutenção da biodiversidade.
ABSTRACT
This study was carried in Ceará Mirim River, State of Rio Grande do Norte, Brazil. At this location, the river shows high water transparency and predominance of aquatic macrophytes in the margins. This study aims to describe the feeding habits and verify the presence of feeding overlap in the diet of four sympatric species of Cheirodontinae: Compsura heterura Eigenmann, 1915 (n= 452), Serrapinnus heterodon (Eigenmann, 1915) (n= 473), S. piaba (Lütken, 1875) (n= 509) and Serrapinnus sp. A (n= 313). The specimens were collected monthly, from April 2001 to April 2002, using seine nets. The stomach contents were analyzed using the frequency of occurrence, percentage composition and an alimentary importance index. The feeding overlap was calculated through the index of Morisita between pairs of species. The species did not showed seasonal variation in the diet. Algae, vegetal matter, microcrustaceans and autochthonous insects were predominant in the species diet. Serrapinnus heterodon and Serrapinnus sp. A presented omnivorous feeding behaviour, while C. heterura and S. piaba showed omnivorous feeding behaviour with tendency to herbivory. In addition, the species showed high feeding overlap due to the consumption of similar items. These results suggest that food resources are abundant and enough to be partioned by these four omnivorous sympatric species.
Este estudo foi realizado no rio Ceará Mirim, Estado do Rio Grande do Norte. No local de coleta, este rio apresenta águas transparentes e predominância de macrófitas aquáticas nas margens. Este estudo teve como objetivos descrever os hábitos alimentares e verificar a existência de sobreposição alimentar na dieta de quatro espécies simpátricas de Cheirodontinae: Compsura heterura Eigenmann, 1915 (n= 452), Serrapinnus heterodon (Eigenmann, 1915) (n= 473), S. piaba (Lütken, 1875) (n= 509) e Serrapinnus sp. A (n= 313). Os espécimes foram coletados mensalmente, entre abril de 2001 e abril de 2002, com redes de arrasto. Os conteúdos estomacais foram analisados através dos métodos de frequência de ocorrência, composição percentual e índice de importância alimentar. A sobreposição alimentar foi calculada entre os pares de espécies através do índice de Morisita. As espécies não mostraram variação sazonal na dieta. Algas, matéria vegetal, microcrustáceos e insetos autóctones foram predominantes na dieta das espécies. Serrapinnus heterodon e Serrapinnus sp. A apresentaram hábito alimentar onívoro, enquanto C. heterura e S. piaba apresentaram o hábito alimentar onívoro com tendência à herbivoria. Além disso, altos valores de sobreposição alimentar entre as espécies foram observados em decorrência do consumo de itens similares. Estes resultados sugerem que os recursos alimentares são abundantes e suficientes para serem partilhados por estas quatro espécies onívoras em simpatria.
ABSTRACT
This study was carried in Ceará Mirim River, State of Rio Grande do Norte, Brazil. At this location, the river shows high water transparency and predominance of aquatic macrophytes in the margins. This study aims to describe the feeding habits and verify the presence of feeding overlap in the diet of four sympatric species of Cheirodontinae: Compsura heterura Eigenmann, 1915 (n= 452), Serrapinnus heterodon (Eigenmann, 1915) (n= 473), S. piaba (Lütken, 1875) (n= 509) and Serrapinnus sp. A (n= 313). The specimens were collected monthly, from April 2001 to April 2002, using seine nets. The stomach contents were analyzed using the frequency of occurrence, percentage composition and an alimentary importance index. The feeding overlap was calculated through the index of Morisita between pairs of species. The species did not showed seasonal variation in the diet. Algae, vegetal matter, microcrustaceans and autochthonous insects were predominant in the species diet. Serrapinnus heterodon and Serrapinnus sp. A presented omnivorous feeding behaviour, while C. heterura and S. piaba showed omnivorous feeding behaviour with tendency to herbivory. In addition, the species showed high feeding overlap due to the consumption of similar items. These results suggest that food resources are abundant and enough to be partioned by these four omnivorous sympatric species.
Este estudo foi realizado no rio Ceará Mirim, Estado do Rio Grande do Norte. No local de coleta, este rio apresenta águas transparentes e predominância de macrófitas aquáticas nas margens. Este estudo teve como objetivos descrever os hábitos alimentares e verificar a existência de sobreposição alimentar na dieta de quatro espécies simpátricas de Cheirodontinae: Compsura heterura Eigenmann, 1915 (n= 452), Serrapinnus heterodon (Eigenmann, 1915) (n= 473), S. piaba (Lütken, 1875) (n= 509) e Serrapinnus sp. A (n= 313). Os espécimes foram coletados mensalmente, entre abril de 2001 e abril de 2002, com redes de arrasto. Os conteúdos estomacais foram analisados através dos métodos de frequência de ocorrência, composição percentual e índice de importância alimentar. A sobreposição alimentar foi calculada entre os pares de espécies através do índice de Morisita. As espécies não mostraram variação sazonal na dieta. Algas, matéria vegetal, microcrustáceos e insetos autóctones foram predominantes na dieta das espécies. Serrapinnus heterodon e Serrapinnus sp. A apresentaram hábito alimentar onívoro, enquanto C. heterura e S. piaba apresentaram o hábito alimentar onívoro com tendência à herbivoria. Além disso, altos valores de sobreposição alimentar entre as espécies foram observados em decorrência do consumo de itens similares. Estes resultados sugerem que os recursos alimentares são abundantes e suficientes para serem partilhados por estas quatro espécies onívoras em simpatria.
ABSTRACT
Amazonian biodiversity is notorious, this is also valid for the fauna of the mineral-deficient waters of the Rio Negro System. Some 25 years of research on the benthic fauna of Central Amazonian streams resulted in species-rich foodwebs with a high degree of omnivory within dense animal communities. To exemplify the taxonomic range of omnivorous consumers, the detailed resource spectra of 18 consumer species, including Protozoa (2 species), Platyhelminthes (1 species), insects (2 species), fish (6 species) and shrimps (Decapoda, 7 species), associated primarily with the benthic habitats of Rio Negro tributaries, are presented. Special features of omnivory are characterized, and the importance of litter-decomposing fungi as essential energy input into the foodwebs is documented. It is shown that general omnivory -diverse omnivore consumers sharing most of the resource types- is a prevalent feature. The relevance of this general omnivory for the maintenance of biodiversity is discussed.
A biodiversidade do Amazonas é notório e isto também é válido para as águas pobres em nutrientes da bacia do Rio Negro. Uma pesquisa de 25 anos da fauna béntica de igarapés da Amazônia Central resultou em redes alimentares caraterizadas por alta diversidade de espécies, por intensa omnivoria e por alta densidade populacional. Para demonstrar a generalidade taxonômica de omnivoria no bentos dos igarapés, são apresentados as listas de presas / recursos de 18 espécies de consumidores, sendo Protozoa (2 epécies), Platyhelminthes (1 espécie), insetos (2 espécies), peixes (6 espécies) e camarões (Decapoda, 7 espécies). Diferentes categorias de omnivoria são apresentados, e a importância de fungos decompositores da liteira submersa como input básico de energia nas redes alimentares é demonstrada. É prevalente a omnivoria geral, sendo que as diferentes espécies omnívoros estão utilizando os mesmos recursos. Considera- se a relevância desta omnivoria geral para a manutenção da biodiversidade.
ABSTRACT
Food webs usually display an intricate mix of trophic interactions where multiple prey are common. In this context omnivory has been the subject of intensive analysis regarding food web stability and structure. In a three species omnivory setting it is shown that the modeling of prey preference by the top predator may exert a strong influence on the short as well as on the long term dynamics of the respective food web. Clearly, this has implications concerning the stability and the structure of omnivory systems under disturbances such as nutrient enrichment.
Redes tróficas apresentam geralmente uma variada rede de interações onde múltiplas presas são comuns. Neste contexto, a onivoria vem sendo objeto de intensas análises à luz da estabilidade e estrutura do sistema. A modelagem do termo de preferência pelo predador de topo sobre suas presas pode exercer uma forte influência sobre as dinâmicas transiente e de longo prazo em uma rede trófica onívora composta por três espécies. Claramente, isto tem implicações sobre a estrutura e estabilidade do sistema sob distúrbios tais como o enriquecimento por nutrientes.
ABSTRACT
Ecologists have long struggled to explain variation in food-chain length among natural ecosystems. Food-chain length is predicted to be shorter in ecosystems subjected to greater disturbance because longer chains are theoretically less resilient to perturbation. Moreover, food-chain length is expected to be longer in larger ecosystems because increasing ecosystem size increases species richness and stabilizes predator-prey interactions, or increases total resource availability. Here we test the roles of disturbance and ecosystem size in determining the food-chain length of terrestrial food webs on Bahamian islands. We found that disturbance affected the identity of top predators, but did not change food-chain length because alternative top predators occupied similar trophic positions. On the other hand, a 106 -fold increase in ecosystem size elevated food-chain length by one trophic level. We suggest that the effect of disturbance on food-chain length is weak when alternate top predators are trophic omnivores and have similar trophic positions. This and previous work in lakes suggest that ecosystem size may be a strong determinant of food-chain length in both aquatic and terrestrial ecosystems.