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Meredith E. Protas - One of the best experts on this subject based on the ideXlab platform.
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Developmental transcriptomic analysis of the cave-dwelling crustacean, Asellus aquaticus
2019Co-Authors: Joshua B. Gross, Dennis A. Sun, Brian M. Carlson, Sivan Brodo-abo, Meredith E. ProtasAbstract:Cave animals are a fascinating group of species often demonstrating characteristics including reduced eyes and pigmentation, metabolic efficiency, and enhanced sensory systems. Asellus aquaticus, an isopod crustacean, is an emerging model for cave biology. Cave and surface forms of this species differ in many characteristics, including eye size, pigmentation and antennal length. Existing resources for this species include a linkage map, mapped regions responsible for eye and pigmentation traits, sequenced adult transcriptomes, and comparative embryological descriptions of the surface and cave forms. Our ultimate goal is to identify genes and mutations responsible for the differences between the cave and surface forms. To advance this goal, we decided to use a transcriptomic approach. Because many of these changes first appear during embryonic development, we sequenced embryonic transcriptomes of cave, surface, and hybrid individuals at the stage when eyes and pigment become evident in the surface form. We generated a cave, a surface, a hybrid, and an integrated transcriptome to identify differentially expressed genes in the cave and surface forms. Additionally, we identified genes with allele-specific expression in hybrid individuals. These embryonic transcriptomes are an important resource to assist in our ultimate goal of determining the genetic underpinnings of the divergence between the cave and surface forms.
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Embryonic origin and genetic basis of cave associated phenotypes in the isopod crustacean Asellus aquaticus
Scientific reports, 2018Co-Authors: Hafasa Mojaddidi, Franco E. Fernandez, Priscilla A. Erickson, Meredith E. ProtasAbstract:Characteristics common to animals living in subterranean environments include the reduction or absence of eyes, lessened pigmentation and enhanced sensory systems. How these characteristics have evolved is poorly understood for the majority of cave dwelling species. In order to understand the evolution of these changes, this study uses an invertebrate model system, the freshwater isopod crustacean, Asellus aquaticus, to examine whether adult differences between cave and surface dwelling individuals first appear during embryonic development. We hypothesized that antennal elaboration, as well as eye reduction and pigment loss, would be apparent during embryonic development. We found that differences in pigmentation, eye formation, and number of segments of antenna II were all present by the end of embryonic development. In addition, we found that cave and surface hatchlings do not significantly differ in the relative size of antenna II and the duration of embryonic development. To investigate whether the regions responsible for eye and pigment differences could be genetically linked to differences in article number, we genotyped F2 hybrids for the four previously mapped genomic regions associated with eye and pigment differences and phenotyped these F2 hybrids for antenna II article number. We found that the region previously known to be responsible for both presence versus absence of pigment and eye size also was significantly associated with article number. Future experiments will address whether pleiotropy and/or genetic linkage play a role in the evolution of cave characteristics in Asellus aquaticus.
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A Transcriptomic Analysis of Cave, Surface, and Hybrid Isopod Crustaceans of the Species Asellus aquaticus
PloS one, 2015Co-Authors: Bethany A. Stahl, Joshua B. Gross, Daniel I. Speiser, Todd H. Oakley, Nipham H. Patel, Douglas B. Gould, Meredith E. ProtasAbstract:Cave animals, compared to surface-dwelling relatives, tend to have reduced eyes and pigment, longer appendages, and enhanced mechanosensory structures. Pressing questions include how certain cave-related traits are gained and lost, and if they originate through the same or different genetic programs in independent lineages. An excellent system for exploring these questions is the isopod, Asellus aquaticus. This species includes multiple cave and surface populations that have numerous morphological differences between them. A key feature is that hybrids between cave and surface individuals are viable, which enables genetic crosses and linkage analyses. Here, we advance this system by analyzing single animal transcriptomes of Asellus aquaticus. We use high throughput sequencing of non-normalized cDNA derived from the head of a surface-dwelling male, the head of a cave-dwelling male, the head of a hybrid male (produced by crossing a surface individual with a cave individual), and a pooled sample of surface embryos and hatchlings. Assembling reads from surface and cave head RNA pools yielded an integrated transcriptome comprised of 23,984 contigs. Using this integrated assembly as a reference transcriptome, we aligned reads from surface-, cave- and hybrid- head tissue and pooled surface embryos and hatchlings. Our approach identified 742 SNPs and placed four new candidate genes to an existing linkage map for A. aquaticus. In addition, we examined SNPs for allele-specific expression differences in the hybrid individual. All of these resources will facilitate identification of genes and associated changes responsible for cave adaptation in A. aquaticus and, in concert with analyses of other species, will inform our understanding of the evolutionary processes accompanying adaptation to the subterranean environment.
Peter Calow - One of the best experts on this subject based on the ideXlab platform.
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Comparative ecology of Gammarus pulex (L.) and Asellus aquaticus (L.) I: population dynamics and microdistribution
Hydrobiologia, 1994Co-Authors: Manuel A S Graca, Lorraine Maltby, Peter CalowAbstract:Gammarus pulex and Asellus aquaticus generally occupy different zones in rivers; the former occurs in upper reaches but is ‘replaced’ by the latter in lower reaches. Microdistribution and life-history patterns of G. pulex and A. aquaticus in sympatry and allopatry, were analyzed. Both species exhibited similar patterns of microhabitat selection, with larger individuals associated predominantly with large-sized substratum particles, and juveniles with weed. Coexisting populations of G. pulex and A. aquaticus had similar densities and population dynamics. Within each species, differences in population dynamics of allopatric and sympatric populations were observed. Although variation in population dynamics of G. pulex may be explained in terms of competition between the two species, the evidence is weak and equivocal. Differences in the dynamics of the two A. aquaticus populations were possibly a consequence of coal-mine and organic pollution, reducing the survival of offspring in the allopatric population.
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Comparative ecology of Gammarus pulex (L.) and Asellus aquaticus (L.) II: fungal preferences
Hydrobiologia, 1994Co-Authors: Manuel A S Graca, Lorraine Maltby, Peter CalowAbstract:This paper continues to explore niche differentiation in Gammarus pulex and Asellus aquaticus by analysis of their food preferences. Individuals from both species discriminated between leaf discs colonized by different fungal species and exhibited strong preferences for Anguillospora longissima and Heliscus lugdunensis. Fungal preferences were not correlated with the relative abundance of fungi in the field and there was considerable intra-population variability in food preferences — both between individuals and for the same individual through time. Niche overlap between animals from all four study populations was high and there was no evidence of differences in the potential trophic niches of animals from sympatric and allopatric populations.
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Importance of fungi in the diet of Gammarus pulex and Asellus aquaticus I: feeding strategies
Oecologia, 1993Co-Authors: Manuel A S Graca, Lorraine Maltby, Peter CalowAbstract:The importance of fungi in the trophic biology of the freshwater detritivores Gammarus pulex and Asellus aquaticus was investigated. Inspection of leaves used in feeding trials indicated that whereas A. aquaticus scrapes at the leaf surface, G. pulex bites through the leaf material. Both species discriminated between fungal mycelia, fungally colonized and uncolonized leaf material but, although A. aquaticus selectively consumed fungal mycelia, G. pulex fed preferentially on leaf material. Fungi appear to be an important food source for A. aquaticus and selection of food material was positively correlated with fungal biomass. In contrast, for G. pulex, fungi appear to be more important as modifiers of leaf material. However, no significant correlations were found between food preference and any of the leaf modifications measured.
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Importance of fungi in the diet of Gammarus pulex and Asellus aquaticus : II. Effects on growth, reproduction and physiology.
Oecologia, 1993Co-Authors: Manuel A S Graca, Lorraine Maltby, Peter CalowAbstract:An important component of the interaction between macroinvertebrates and leaf litter in streams in the extent to which consumers can differentiate between undecomposed and decomposing leaves. The detritivores Gammarus pulex and Asellus aquaticus fed preferentially on conditioned rather on unconditioned leaf material. Growth in A. aquaticus was significantly reduced when unconditioned leaves were provided, but in G. pulex no significant effect of conditioning on growth was observed. The capacity of G. pulex to tolerate reductions in food quality seems to be a consequence of a compensatory system in which respiration rates change to compensate for reductions in food quality. In this way a constant growth rate is maintained. Increases in ingestion rates to compensate for low quality food were not observed.
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Inter- and intraspecific variation in sensitivity to toxins; the effects of acidity and zinc on the freshwater crustaceans Asellus aquaticus (L.) and Gammarus pulex (L.)
Water Research, 1990Co-Authors: Caroline Naylor, L. Pindar, Peter CalowAbstract:Abstract Sensitivity to pH and zinc is compared between species of freshwater crustaceans, within species between size classes, and within size classes and species between populations. Variation is recorded at all these levels. Asellus aquaticus is more tolerant than Gammarus pulex . Small size classes are generally less tolerant than large. Individuals from populations in polluted sites are more tolerant than those from populations in cleaner sites.
Peter Trontelj - One of the best experts on this subject based on the ideXlab platform.
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Phylogeography of subterranean and surface populations of water lice Asellus aquaticus (Crustacea: Isopoda)
Molecular Ecology, 2004Co-Authors: Rudi Verovnik, Boris Sket, Peter TronteljAbstract:The water louse Asellus aquaticus is a widespread, euryoecious species, mostly uniform throughout its range. However, six subspecies are known from the Dinaric karst in the northwestern Balkans. They include some specialized subterranean populations. The pattern of genetic variation among subterranean and surface populations in this hydrographically highly fragmented karst region was investigated using a 653 bp fragment of the mitochondrial gene (COI). Sequencing of 168 individuals from 25 localities revealed 72 haplotypes. amova and methods of phylogenetic reconstruction all uncovered hydrographic structuring of genetic variation of the populations. Nested clade analysis pointed out several fragmentation events, along with some range expansions within hydrographical systems. By superimposing the subterranean mode of life on the phylogeographical pattern, three independent cave colonizations could be inferred within a distance of < 100 km. Caves were invaded after the ancestral surface populations became isolated through vicariant fragmentation. A possible scenario of hydrographic history of the region was constructed combining the molecular data with palaeogeographical information.
G M Morrison - One of the best experts on this subject based on the ideXlab platform.
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Bioaccumulation of palladium, platinum and rhodium from urban particulates and sediments by the freshwater isopod Asellus aquaticus.
Water research, 2001Co-Authors: Mariella Moldovan, S Rauch, Milagros Gómez, M. Antonia Palacios, G M MorrisonAbstract:The three-way catalytic converters introduced to oxidize and reduce gaseous automobile emissions represent a source of platinum group elements (PGEs), in particular platinum, palladium and rhodium, to the urban environment. Abrasion of automobile exhausts leads to an increase of the concentration of PGEs in environmental matrices such as vegetation, soil and water bodies. The bioaccumulation of Pd, Pt and Rh by the freshwater isopod Asellus aquaticus was studied in natural ecosystems and under laboratory conditions. Owing to the low concentration level (ng g−1) of PGEs in the animals studied, analyses were performed with a quadrupole inductively coupled plasma mass spectrometry (ICP-MS) and hafnium, copper, yttrium, rubidium, strontium and lead were monitored for spectral interference correction. Asellus aquaticus collected in an urban river showed a content (mean±s) of 155.4±73.4, 38.0±34.6, and 17.9±12.2 ng g−1 (dry weight) for Pd, Pt and Rh, respectively. The exposure of Asellus aquaticus to PGE standard solutions for a period of 24 h give bioaccumulation factors of Bf: 150, 85, and 7 for Pd, Pt and Rh, respectively. Exposure of Asellus aquaticus to environmental samples for different exposure periods demonstrated that PGE bioaccumulation is time dependent, and shows a higher accumulation for the materials with a higher PGE content. While all three elements have the same uptake rate for exposure to catalyst materials, for exposure to environmental materials they have a different uptake rate which can be attributed to transformations of the PGE species in the environment.
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Platinum uptake by the freshwater isopod Asellus aquaticus in urban rivers.
The Science of the total environment, 1999Co-Authors: S Rauch, G M MorrisonAbstract:Platinum has been increasing in the environment as a result of emissions from catalytic converters. The platinum emitted is principally located in the vicinity of roads but might be transported to urban rivers through highway and urban run-off water. Platinum concentrations in the freshwater isopod Asellus aquaticus were measured for two urban rivers and a stormwater detention pond. Concentrations ranged from 0.04 to 12.4 micrograms g-1 for direct analysis and from 0.16 to 4.5 micrograms g-1 after depuration. Analyses of water, pore water and sediments indicate that platinum in urban rivers is mostly found in the sediments and these provide the major contribution of platinum to Asellus aquaticus. Exposure experiments showed the importance of platinum speciation for uptake.
Rudi Verovnik - One of the best experts on this subject based on the ideXlab platform.
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Asellus aquaticus: A Model System for Historical Biogeography
Encyclopedia of Caves, 2012Co-Authors: Rudi Verovnik, Marjeta KonecAbstract:Abstract The aquatic isopod Asellus aquaticus independently populated three cave systems in Europe, where it forms troglomorphic populations all described as separate subspecies. Molecular studies confirm that within northwestern part of Dinaric Mts. additional independent invasions of subterranean habitat occurred, resulting in differently developed troglomorphic traits of those populations. The population present in hidrographically isolated subterranean Reka River drainage is most distant both in terms of molecular markers and morphology and has been described as a separate species A. kosswigi. Similarly, the two populations, inhabiting two separate rivers within Planina Cave, show differences in morphology, mtDNA and microsatellites with very few hybrid specimens at the confluence of the rivers, indicating additional speciation in caves. In a broader view A. aquaticus reached central Europe from the east through current Panonian Plain and spread into the subterranean habitats during karstification linked with Dinaric orogenesis approximately 2–4 Mya ago. Several distinct subspecies both from isolated karst poljes and caves were therefore described. It is still not clear whether the formation of cave adapted populations proceeded in a complete isolation from the surface source population or it could have been achieved in sympatry through ecological speciation. These and other similar questions, provide future opportunities to study this exciting model organism.
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Description of a neotype for Asellus aquaticus Linné, 1758 (Crustacea: Isopoda: Asellidae), with description of a new subterranean Asellus species from Europe
Zoologischer Anzeiger - A Journal of Comparative Zoology, 2009Co-Authors: Rudi Verovnik, Simona Prevorčnik, Jure JugovicAbstract:Abstract Asellus aquaticus is one of the most common and well-studied freshwater macroinvertebrates in Europe, but its current taxonomic description is inadequate. Therefore, a neotype is designated and described to allow a comparison with a newly described and illustrated species, Asellus kosswigi sp. n. While several troglomorphic Asellus species are known from Japan, this is the first subterranean species of the genus in Europe. It is morphologically, as well as genetically, distinct from all other, local, surface and subterranean populations. Its species status is confirmed by its syntopic occurrence with Asellus aquaticus without any sign of gene flow.
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Phylogeography of subterranean and surface populations of water lice Asellus aquaticus (Crustacea: Isopoda)
Molecular Ecology, 2004Co-Authors: Rudi Verovnik, Boris Sket, Peter TronteljAbstract:The water louse Asellus aquaticus is a widespread, euryoecious species, mostly uniform throughout its range. However, six subspecies are known from the Dinaric karst in the northwestern Balkans. They include some specialized subterranean populations. The pattern of genetic variation among subterranean and surface populations in this hydrographically highly fragmented karst region was investigated using a 653 bp fragment of the mitochondrial gene (COI). Sequencing of 168 individuals from 25 localities revealed 72 haplotypes. amova and methods of phylogenetic reconstruction all uncovered hydrographic structuring of genetic variation of the populations. Nested clade analysis pointed out several fragmentation events, along with some range expansions within hydrographical systems. By superimposing the subterranean mode of life on the phylogeographical pattern, three independent cave colonizations could be inferred within a distance of < 100 km. Caves were invaded after the ancestral surface populations became isolated through vicariant fragmentation. A possible scenario of hydrographic history of the region was constructed combining the molecular data with palaeogeographical information.