19,402 research outputs found

    An Authentication Survey on Retail Seafood Products Sold on the Bulgarian Market Underlines the Need for Upgrading the Traceability System

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    Economically motivated or accidental species substitutions lead to economic and potential health damage to consumers with a loss of confidence in the fishery supply chain. In the present study, a three–year survey on 199 retail seafood products sold on the Bulgarian market was addressed to assess: (1) product authenticity by molecular identification; (2) trade name compliance to the list of official trade names accepted in the territory; (3) adherence of the list in force to the market supply. DNA barcoding on mitochondrial and nuclear genes was applied for the identification of whitefish (WF), crustaceans (C) and mollusks (cephalopods—MC; gastropods—MG; bivalves—MB) except for Mytilus sp. products for which the analysis was conducted with a previously validated RFLP PCR protocol. Identification at the species level was obtained for 94.5% of the products. Failures in species allocation were reconducted due to low resolution and reliability or the absence of reference sequences. The study highlighted an overall mislabeling rate of 11%. WF showed the highest mislabeling rate (14%), followed by MB (12.5%), MC (10%) and C (7.9%). This evidence emphasized the use of DNA–based methods as tools for seafood authentication. The presence of non–compliant trade names and the ineffectiveness of the list to describe the market species varieties attested to the need to improve seafood labeling and traceability at the national level

    Assessing the species boundary and ecological niche in freshwater gastropods of the family Physidae (Gastropoda, Hygrophila)

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    The present thesis contributed to increasing the knowledge about the diversity of the neotropical freshwater mollusks. Through the use of different methodologies for analyzing molecular and geographical occurrence data, we address important taxonomic issues and show new paths for future taxonomic research on the Physidae family. This family for a long time had classification proposals based only on morphological characters of the shell and, later, on the anatomy of the soft parts. The application of molecular delimitation methods based on coalescence showed the inadequacy of morphological criteria in discriminating intraspecific variability (overestimating family diversity) and in detecting the existence of cryptic species complexes (underestimating family diversity). The data on the occurrence along with the use of georeferencing tools, modeling, and ecological niche analyses applied to South American physid species, indicated the possibility of errors in species identification and the need to reassess the distribution of these physids using other operational criteria such as molecular approaches to access the actual family diversity and distribution for the continent.A presente tese contribuiu para ampliar o conhecimento sobre a diversidade da malacofauna dulcícola neotropical. Através do emprego de diferentes metodologias de análise de dados moleculares e de ocorrência geográfica abordamos importantes questões taxonômicas e mostramos novos caminhos para futuras pesquisas taxonômicas da família Physidae. Família essa que por muito tempo teve propostas de classificação embasadas apenas em caracteres morfológicos da concha e, posteriormente, na anatomia das partes moles. A aplicação de métodos de delimitação molecular baseados em coalescência, evidenciou a insuficiência dos critérios morfológicos em discriminar a variabilidade intraespecífica (superestimando a diversidade da família) e, em detectar a existência de complexos de espécies crípticas (subestimando a diversidade da família). A abordagem de busca intensiva por dados de ocorrência junto a utilização de ferramentas de georreferenciamento, modelagem e análises de nicho ecológico aplicadas às espécies de fisídeos sul-americanos, indicaram a possibilidade de erros de identificação de espécies e a necessidade de reavaliar a distribuição desses fisídeos usando outros critérios operacionais, incluindo abordagens moleculares, para acessar a diversidade e distribuição reais da família para o continente

    RCE - Zooarchaeological reference collection

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    The archaeology department of the Cultural Heritage Agency holds a zooarchaeological reference collection. The collection consists of fossil, archaeological and recent remains of mammals, birds, fish and mollusks. Our aim is to support zooarchaeological research. Therefore we want to publish a catalogue of our collection, so researchers can browse the collection from home, before planning a visit

    Feeding Diversity of Finfish in Different Wild Habitat

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    Sonmiani Bay has unique faunal diversity and distribution especially finfish as mangroves provides an imperative ecosystem which offer the shelter and protection to the associated organisms and care of their juveniles in bay limits. This study aimed to evaluate the diversity pattern according to physical and physiological responses and feeding habits (carnivorous and herbivorous) of finfish species in accordance with current habitat conditions in the Sonmiani Bay. A total of 4499, individuals of comprising 155 finfish species that represent 50 families were captured by these four (beach seines, purse seines, gill nets, and cast nets) nets during a twelve-month survey in a year. The distribution pattern of finfishes captured classified into four groups (tidal visitors, permanent residents, partial residents, and seasonal visitors) according to their patterns of distribution. Understanding of the true feeding behavior of organisms needs a more reliable and functional approach. The feeding ecology is not only functional for food and feeding behavior of fish as usually described by various tools and techniques of analytical research to take up more reliable details to explain the feeding biology in fish but also the indicator of habitat quality and status

    Life history and mutation rate joint evolution

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    The cost of germline maintenance gives rise to a trade-off between lowering the deleterious muta-tion rate and investing in life history functions. Therefore, life history and the mutation rate evolve jointly, but this coevolution is not well understood. We develop a mathematical model to analyse the evolution of resource allocation traits affecting simultaneously life history and the deleterious mutation rate. First, we show that the invasion fitness of such resource allocation traits can be approximated by the basic reproductive number of the least-loaded class; the expected lifetime pro-duction of offspring without deleterious mutations born to individuals without deleterious mutations. Second, we apply the model to investigate (i) the joint evolution of reproductive effort and germline maintenance and (ii) the joint evolution of age-at-maturity and germline maintenance. This analysis provides two biological predictions. First, under higher exposure to environmental mutagens (e.g. oxygen), selection favours higher allocation to germline maintenance at the expense of life history. Second, when exposure to environmental mutagens is higher, life histories tend to be faster with individuals having shorter life spans and smaller body sizes at maturity. Our results suggest that mutation accumulation via the cost of germline maintenance is a major force shaping life-history traits

    A One-Year Systematic Study to Assess the Microbiological Profile in Oysters from a Commercial Harvesting Area in Portugal

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    As filter-feeding animals farmed in water bodies exposed to anthropogenic influences, oysters can be both useful bioremediators and high-risk foodstuffs, considering that they are typically consumed raw. Understanding the dynamic of bacterial and viral load in Pacific oyster (Crassostrea gigas) tissues, hemolymph, outer shell surface biofilm, and farming water is therefore of great importance for microbiological risk assessment. A one-year survey of oysters collected from a class B production area (Canal de Mira, on the Portuguese western coast) revealed that these bivalve mollusks have a good depurating capacity with regard to bacteria, as Salmonella spp. and viable enterococci were not detected in any oyster flesh (edible portion) samples, despite the fact that these bacteria have regularly been found in the farming waters. Furthermore, the level of Escherichia coli contamination was clearly below the legal limit in oysters reared in a class B area (>230–≤4600 MPN E. coli/100 g). On the contrary, norovirus was repeatedly detected in the digestive glands of oysters sampled in autumn, winter, and spring. However, their presence in farming waters was only detected during winter

    A molluscan class struggle: exploring the surprisingly uneven distribution of chemosymbiosis among two major mollusk groups

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    Many bivalves and gastropods from marine reducing environments such as deep ocean hydrothermal vents and seeps host chemosynthetic bacteria in a nutritional symbiosis. Despite their functional similarities, the distribution of chemosymbiosis in these two mollusk classes is surprisingly uneven: the number of bivalve species known to host chemosynthetic symbionts is more than twenty times that of gastropods, and chemosymbiotic bivalves are reported from a far greater diversity of marine habitats. Here we explore the potential drivers for this trend, including but not limited to physiological differences, habitat characteristics, and sampling bias. Sampling bias likely contributes to the magnitude of the observed discrepancy, but we posit that the phenomenon itself reveals how intrinsic (e.g. morphology) and extrinsic (e.g. organic matter availability) factors might have shaped the distribution of extant gastropod and bivalve associations. These observations also serve as an impetus for increasing investigation into gastropods and other mollusks from chemically reducing environments to better understand the evolution and ecology of chemosymbiosis among molluscan hosts

    Long-term zooplankton dynamics in Lake Taupō: 2000-2020

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    Long-term monitoring is essential for distinguishing between natural and anthropogenically induced changes within ecosystems, particularly those with high degrees of natural fluctuation. In order to gain further understanding of the links between physical, chemical and biotic factors, zooplankton have been highlighted as useful bioindicators within aquatic ecosystems. Long-term zooplankton monitoring studies have been utilized to highlight changes in lake trophic state, changes within catchments, fisheries practices and invasions. Lake Taupō, New Zealand’s largest lake, has been subject to a long-term monitoring programme by NIWA since 1994, commissioned by the Waikato Regional Council, with the primary purpose of detecting changes in the lake’s trophic state through time. Since January 2000, the monitoring programme has included biweekly zooplankton sampling; no results of this have yet been published. The purpose of my research was to assess if there have been any significant changes in the zooplankton community composition over the monitoring period (2000-2020), with a particular focus on the last 12 years of data (2009-2020), and determine the importance of measured environmental variables in influencing changes in the zooplankton community composition. Lake Taupō was assessed as microtrophic to oligotrophic throughout the monitoring period (Trophic Level Index (TLI) between 1.5 and 2.9), and there were no significant linear changes in any of the measured environmental variables (R-squared values all 0.05). The zooplankton data was separated into two separate datasets; a shorter February 2009 – December 2020 dataset with samples analysed entirely by myself, and a longer January 2000-December 2020 dataset, with earlier samples analysed by NIWA, utilising a lower taxonomic resolution. Multivariate analyses (nMDS and ANOSIM) indicated significant differences among three yearly groups of zooplankton data within both the shorter (Global R statistic = 0.179, p = 0.014) and longer dataset (Global R statistic = 0.353, p = 0.001). Time and temperature were inferred by Redundancy Analysis (RDA) as the most important environmental variables associated with change in zooplankton community composition in both the shorter 2009-2020 (Lambda-A = 0.08 for both, p = 0.002 for both) and longer 2000-2020 datasets (Lambda-A = 0.15, p = 0.002 for time, and Lambda-A = 0.06, p = 0.002 for temperature). Both ordinations indicated that changes associated with time (long-term) and changes in temperature were primarily unrelated. Changes in zooplankton community composition influenced by temperature were attributed to seasonal succession. Zooplankton community composition differed between the beginning and end of the monitoring periods in both datasets. However, the direction of the community change seemingly reversed around 2009-2011, with assemblages late in the study reverting to communities similar to those observed earlier in the study. Decreases in the native large Daphnia thomsoni and increased importance of the non-native Daphnia galeata indicate that colonisation by the invading species has influenced the observed changes in zooplankton community composition. The influences of top-down control in the form of predation on the zooplankton community by fish (an unmeasured variable) may have also influenced communities, with shifts from large- to small-sized species observed. Rotifers indicative of both low and high TLI are present throughout the study (e.g., Polyarthra dolichoptera and Keratella cochlearis respectively), but the community is dominated throughout by species indicative of low trophic state (e.g., Conochiloides dossuarius), which is consistent with previous zooplankton studies within Lake Taupō. Continued monitoring of zooplankton, physical and chemical lake properties, algae, and bacteria is advised, with the inclusion of fish monitoring recommended
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