Are rare species rare or just overlooked? Assessing the distribution of the freshwater bryozoan, Lophopus crystallinus

Given the widespread degradation of freshwater habitats, assessing the distributions of species that may be negatively or positively impacted should be of general interest. However, determining distributions of freshwater organisms that are small and patchily distributed and attached or sedentary is particularly problematic, as it is time consuming, inaccurate, and nearly impossible when the focal species is rare. Here we illustrate the use of indirect sampling approaches to survey the distribution of the rare freshwater bryozoan Lophopus crystallinus, a priority species in the UK Biodiversity Action Plan [Anonymous, 1999. UK Biodiversity Group Tranche 2 Action Plans. Invertebrates, Vol. 4. Environment Agency, Peterborough, pp. 437-439.1. By utilising two complementary methods for sampling bryozoan propagules (statoblasts), namely the collection of debris samples and sediment cores, we achieved an efficient and integrative sampling of habitats across spatial and temporal scales. Analysis of 154 debris samples, encompassing 62 rivers and lakes, identified at least 16 new populations while analysis of 26 sediment cores provided evidence of current or very recent (in the last 10-20 years) occurrence in a further six localities. These results represent a more than 10-fold increase in the current recorded distribution of the species in the UK. Logistic regression analysis provided evidence that L. crystallinus is generally found in lowland sites and is tolerant of eutrophication. Our study exemplifies how integrative and indirect sampling approaches can greatly aid in assessing the conservation status of rare aquatic species and reveals, in this case, that the focal species is less rare than previously appreciated. (c) 2006 Elsevier Ltd. All rights reserved.

Seasonally resolved growth of freshwater bivalves determined by oxygen and carbon isotope shell chemistry

By means of a monitoring experiment in two rivers in the Netherlands, we establish a relationship between seasonally resolved growth rates in unionid freshwater bivalves and their environment. We reconstructed these seasonally resolved growth rates by using relationships of stable isotopes in the shells and their ambient river water. The reconstructed growth rates reveal that shells grow fastest in spring-early summer, when highest food availability occurs in the rivers. In addition, the reconstructed growth rates show that onset and cessation of growth are mainly influenced by water temperature.

Carbon and nitrogen stable isotope ratio analysis of freshwater, brackish and marine fish from Belgian archaeological sites (1st and 2nd millennium AD)

Carbon and nitrogen stable isotope ratios were measured in 157 fish bone collagen samples from 15 different archaeological sites in Belgium which ranged in ages from the 3rd to the 18th c. AD. Due to diagenetic contamination of the burial environment, only 63 specimens produced results with suitable C:N ratios (2.9–3.6). The selected bones encompass a wide spectrum of freshwater, brackish, and marine taxa (N = 18), and this is reflected in the δ13C results (−28.2‰ to −12.9%). The freshwater fish have δ13C values that range from −28.2‰ to −20.2‰, while the marine fish cluster between −15.4‰ and −13.0‰. Eel, a catadromous species (mostly living in freshwater but migrating into the sea to spawn), plots between −24.1‰ and −17.7‰, and the anadromous fish (living in marine environments but migrating into freshwater to spawn) show a mix of freshwater and marine isotopic signatures. The δ15N results also have a large range (7.2‰ to 16.7‰) indicating that these fish were feeding at many different trophic levels in these diverse aquatic environments. The aim of this research is the isotopic characterization of archaeological fish species (ecology, trophic level, migration patterns) and to determine intra-species variation within and between fish populations differing in time and location. Due to the previous lack of archaeological fish isotope data from Northern Europe and Belgium in particular, these results serve as an important ecological backdrop for the future isotopic reconstruction of the diet of human populations dating from the historical period (1st and 2nd millennium AD), where there is zooarchaeological and historical evidence for an increased consumption of marine fish.

Strengthening the link between climate, hydrological and species distribution modeling to assess the impacts of climate change on freshwater biodiversity

To understand the resilience of aquatic ecosystems to environmental change, it is important to determine how multiple, related environmental factors, such as near-surface air temperature and river flow, will change during the next century. This study develops a novel methodology that combines statistical downscaling and fish species distribution modeling, to enhance the understanding of how global climate changes (modeled by global climate models at coarse-resolution) may affect local riverine fish diversity. The novelty of this work is the downscaling framework developed to provide suitable future projections of fish habitat descriptors, focusing particularly on the hydrology which has been rarely considered in previous studies. The proposed modeling framework was developed and tested in a major European system, the Adour-Garonne river basin (SW France, 116,000 km(2)), which covers distinct hydrological and thermal regions from the Pyrenees to the Atlantic coast. The simulations suggest that, by 2100, the mean annual stream flow is projected to decrease by approximately 15% and temperature to increase by approximately 1.2 °C, on average. As consequence, the majority of cool- and warm-water fish species is projected to expand their geographical range within the basin while the few cold-water species will experience a reduction in their distribution. The limitations and potential benefits of the proposed modeling approach are discussed. Copyright © 2012 Elsevier B.V. All rights reserved.

Climate change and coupling of macronutrient cycles along the atmospheric, terrestrial, freshwater and estuarine continuum

This paper provides an introduction to the Special Issue on “Climate Change and Coupling of Macronutrient Cycles along the Atmospheric, Terrestrial, Freshwater and Estuarine Continuum”, dedicated to Colin Neal on his retirement. It is not intended to be a review of this vast subject, but an attempt to synthesize some of the major findings from the 22 contributions to the Special Issue in the context of what is already known. The major research challenges involved in understanding coupled macronutrient cycles in these environmental media are highlighted, and the difficulties of making credible predictions of the effects of climate change are discussed. Of particular concern is the possibility of interactions which will enhance greenhouse gas concentrations and provide positive feedback to global warming.

ATP pulse and calcium homeostasis in cells from hepatopancreas of Dilocarcinus pagei, a freshwater crab

Calcium (Ca) is critical for crustaceans due to their molting cycle and its presence in the carapace as calcium carbonate, apart from the usual functions of Ca, such as cell signalling. Ca transport in Dilocarcinus pagei, a freshwater crab, was studied in isolated cells from hepatopancreas to further characterize Ca transport mechanisms in these crabs. Cells were isolated and loaded with Fluo-3, a calcium fluorescent dye. Three different cell treatments were performed: Group 1 cells were Ca free during cell dissociation, and calcium was present (at 1mM) for fluorescence cell loading and transport experiments (FC); Group 2 cells were calcium free during cell dissociation and for transport experiments, but not during cell loading (LC); and Group 3 cells were Ca free during cell dissociation, cell loading and transport experiments (WC). Intracellular Ca was recorded through time after ATP was added to the cells and ATP caused an increase in Ca efflux within 30s in all cells. WC cells showed the smallest Ca efflux compared to the other cells, probably because it was intracellularly Ca ""depleted"". Vanadate and amiloride decreased the Ca efflux when ATP was added to the cells, while verapamil did not cause any effect in Ca efflux, confirming the presence of a Ca(2+)-ATPase sensitive to vanadate in hepatopancreas of D. pagei. In a different set of experiments, cells were also exposed to a Ca pulse of 1 and 10mM during 180s. 10mM Ca increased intracellular Ca compared to 1mM, and the increase was not recovered during the experimental time. Additionally, Ca influx was reduced by verapamil and amiloride, but not completely. The results suggest that Ca influx probably occurs through an undefined exchanger, apart from Ca channels (verapamil sensitive) and electrogenic 1Na(+)(1H(+))/1 Ca(2+) exchanger (amiloride-sensitive). Similarities between freshwater and seawater crabs, lobsters and crayfish in relation to plasma membrane Ca transporters, although the environment where they live is quite diverse, suggest that universal mechanisms for Ca homeostasis are widespread among crustaceans. (C) 2010 Elsevier Inc. All rights reserved.

Testicular structure and spermatogenesis of Amazonian freshwater cururu stingray Potamotrygon cf. histrix

The cururu stingray Potamotrygon cf. histrix, a new and endemic Amazonian freshwater species, presents appropriate characteristics for fish keeping and is exploited from its natural environment. The present study identified the testicular structure and spermatogenesis of this species. Gonads from adult male specimens were dissected, fixed and processed for histological analysis. The testes were of testicular/epigonial type. The presence of germinal papillae was observed in the upper portion of organ with primordial germ cells and Sertoli cell precursors. The testis was lobular with zonal organization and cystic gametogenesis, with the occurrence of spermatoblasts. The Sertoli cells underwent morphological modifications over the course of gamete formation. The spermatozoids had long heads and were spiraled on their own axis. Information on the reproductive biology will serve as basis for studies on the reproduction and phylogeny of this peculiar group of cartilaginous fish.

Hematological parameters in two neotropical freshwater teleost, Leporinus macrocephalus (Anostomidae) and Prochilodus lineatus (Prochilodontidae)

Leporinus macrocephalus is a non-migratory omnivore fish which occurs in waters with a relatively high oxygen rate. Prochilodus lineatus is a migratory fish that inhabits deoxygenated hypolimnion and feeds on detritus material. Red blood cell, thrombocytes and white blood cell counts, hematocrit and hemoglobin, serum electrolytes (sodium, potassium, calcium, magnesium and chloride), metabolic products (total serum protein and plasma glucose) and blood cells major axis length for L. macrocephalus and P. lineatus were compared. White blood cell counts for both species indicated a similar activity of the immune functions. The concentration of total protein, sodium, calcium, magnesium and chloride, MCV, as well as red blood cells, monocytes, and thrombocytes size in L. macrocephalus were higher than in P. lineatus. However, P. lineatus had higher red blood cell counts, hematocrit and hemoglobin, which reflects a considerable adaptation to survive in an environment with low levels of oxygen.

Bioaccumulation of chlorinated pesticides and PCBs in the tropical freshwater fish Hoplias malabaricus: Histopathological, physiological, and immunological findings

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Use of the freshwater crab Trichodactylus fluviatilis to biomonitoring Al and Mn contamination in river water.

Determinations of Al and Mn concentrations in the tissues (gills, hepatopancreas and muscle) of the freshwater crab Trichodactylus fluviatilis and water samples, both collected from sites on tributaries of the Corumbatai River (São Paulo, Brazil) were performed. The Bioaccumulation Factor (BAF), calculated for different sites with respect to the water concentration, ranged from 173-555 for Al and from 636 - 921 for Mn. Dissolved concentrations of Al and Mn in water samples (collected in different sites) were related to the accumulation of these metals in crabs, suggesting that T. fluviatilis is good biomonitor for Al and Mn pollution in aquatic ecosystem.

Quantitative fidelity of recent freshwater mollusk assemblages from the Touro Passo River, Rio Grande do Sul, Brazil

O presente estudo teve como objetivo apresentar uma das primeiras contribuições ao conhecimento sobre a fidelidade quantitativa de associações de moluscos recentes em rios subtropicais. Tanatocenoses e biocenoses foram estudadas em seções retilínea e meandrante tendendo a anastomosada, no curso médio do rio Touro Passo, um tributário de 4ª ordem do rio Uruguai, localizado no extremo oeste do Rio Grande do Sul. As amostragens foram realizadas por meio de quadrats de 5 m², cinco em cada seção, amostrando-se um total de 50 m². Também foram feitas amostragens em um ambiente lêntico, com comunicação intermitente com o Touro Passo, objetivando detectar a existência de transporte de comunidades lênticas para o interior do rio. Os resultados obtidos mostram que, apesar da freqüente oscilação do nível da água, a biocenose do Touro Passo apresenta uma alta fidelidade ecológica e sofre pouca influência de espécies de ambientes lênticos. A composição taxonômica e características de estrutura de comunidades, especialmente as espécies dominantes, refletem, ainda, diferenças ecológicas relacionadas às duas seções amostradas, como a maior complexidade de habitats da estação meandrante. Quanto à fidelidade quantitativa, 60% das espécies encontradas vivas também foram encontradas mortas e 47,3% das espécies encontradas mortas também foram encontras vivas em escala de rio. Porém, 72% dos exemplares coletados mortos são representantes de espécies encontradas vivas. Essa percentagem alta pode estar relacionada à boa correlação entre o ranking de dominância das associações vivas e mortas e, conseqüentemente, as espécies dominantes das tanatocenoses podem ser utilizadas para inferir características ecológicas das biocenoses. Todos os índices analisados variaram muito em escala local (quadrat) e seus valores são mais aproximados aos de outros, registrados em estudos prévios, apenas quando analisados em escala mais ampla (seção, área total).

Feeding ecology, density and biomass of the freshwater turtle, Phrynops geoffroanus, inhabiting a polluted urban river in south-eastern Brazil

This study examines the ecology of a population of Geoffroy's side-necked turtle Phrynops geoffroanus inhabiting a polluted urban river in Ribeirão Preto city, São Paulo state, south-eastern Brazil. Adult turtles fed mainly on Chironomidae larvae and pupae (Chironomus cf. plumosus, 100% of occurrence frequency) and domestic waste, but they also consumed terrestrial items (cockroach, snails) and carrion. Juvenile turtles showed more feeding diversity than the adults and exhibited a trend for predation on Chironomidae pupae, but this is not reflected in resource partitioning. The elevated number of turtles (170-230 turtles/ha of river) and biomass (255-345 kg/ha of river) inhabiting this urban river is probably the result of the abundance of sewage and organic waste produced by humans, the absence of predators, and increased availability of nesting areas. Such factors convert this area into an environment highly advantageous for the survival of Geoffroy's side-necked turtle.

Occurrence of the Indo-Pacific freshwater prawn Macrobrachium equidens Dana 1852 (Decapoda, Palaemonidae) on the coast of Brazilian Amazonia, with notes on its reproductive biology

O camarão de água doce Macrobrachium equidens, nativo da região do Indo-Pacífico, foi registrada pela primeira vez na costa da Amazônia Brasileira. Esta espécie foi encontrada habitando o mesmo ambiente que duas espécies nativas do gênero Macrobrachium: M. amazonicum e M. acanthurus, e é morfologicamente muito similar à última. A identificação dessa espécie foi confirmada pela análise da sequencia genética do gene mitocondrial Citocromo Oxidase (COI). Uma descrição detalhada das características morfológicas e biologia reprodutiva de M. equidens neste novo ambiente que é apresentada.

Feeding ecology of immature Lithodoras dorsalis (Valenciennes, 1840) (Siluriformes: Doradidae) in a tidal environment, estuary of the rio Amazonas

O estudo da ecologia alimentar de peixes é uma abordagem consistente na avaliação dos processos interativos dentro das comunidades. Dessa forma, este trabalho teve como objetivo investigar a ecologia alimentar do bacu-pedra Lithodoras dorsalis em furos próximos no delta do estuário Amazônico (Brasil), uma área sobre influência de macro-marés, em diferentes períodos pluviométricos. Durante 12 meses de coletas (julho de 2010 a junho de 2011), foram coligidos 371 espécimes jovens, sendo que a dieta da espécie foi composta por 28 itens alimentares analisados pelos seguintes índices: Índice de Repleção Estomacal, Índice de Importância Alimentar e Amplitude de Nicho. Lithodoras dorsalis quando jovem foi classificada como herbívora com tendência à frugivoria, devido aos altos valores de importância de frutos e sementes em sua dieta. A intensidade de obtenção de alimento por L. dorsalis diferiu entre os meses de coleta, onde o final do período de transição chuva-estiagem e o início da estiagem foram os períodos de menor e maior atividade alimentar, respectivamente. Também houve diferença na importância alimentar dos itens entre os períodos pluviométricos. Estes resultados fornecem informações importantes sobre a ecologia alimentar de doradídeos na Amazônia. Além disso, percebeu-se o alto consumo de material alóctone pelo bacu-pedra, sendo estes itens alimentares provenientes da floresta ripária, o que reforça a importância deste ambiente para a conservação da ictiofauna neotropical.

Larval development of indigenous South American freshwater fish species, with particular reference to pacu (Piaractus mesopotamicus): A review

In recent years, a number of South American freshwater fish have gained increasing attention for their potential in aquaculture, not only because of their excellent performance in farming systems but also to meet the high consumer demand for these species due to declining fishery resources. Many South American freshwater species are migratory and produce altricial larvae, with a small amount of yolk reserves. Unlike precocial freshwater species and altricial coldwater marine fish, these freshwater fish investigated have rapid yolk depletion and metamorphosis. Specific studies on the initial development of South American fish are scarce and fragmented. One of the most widely studied species is the pacu (Piaractus mesopotamicus), farmed in warm continental waters. In the present review we compile new and published data on the initial development of pacu, including morphogenesis of the skeletal, muscle, digestive and sensory systems; compare it to other Neotropical species; and discuss the importance of this information to develop larviculture protocols. When pacu larvae exhaust yolk reserves, they initiate a new form of interaction with the environment, becoming exclusively exotrophic. This type of interaction is made possible by the rapid development of sensory, skeletal, locomotor and digestive structures. In addition to understanding fish ontogeny, studies on larval development are necessary to improve farming systems and larviculture techniques aimed at producing high-quality juveniles in aquaculture. (C) 2014 Elsevier B.V. All rights reserved.