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Meredith E. Protas - One of the best experts on this subject based on the ideXlab platform.

  • Developmental transcriptomic analysis of the cave-dwelling crustacean, Asellus aquaticus
    2019
    Co-Authors: Joshua B. Gross, Dennis A. Sun, Brian M. Carlson, Sivan Brodo-abo, Meredith E. Protas
    Abstract:

    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.

  • Embryonic origin and genetic basis of cave associated phenotypes in the isopod crustacean Asellus aquaticus
    Scientific reports, 2018
    Co-Authors: Hafasa Mojaddidi, Franco E. Fernandez, Priscilla A. Erickson, Meredith E. Protas
    Abstract:

    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.

  • A Transcriptomic Analysis of Cave, Surface, and Hybrid Isopod Crustaceans of the Species Asellus aquaticus
    PloS one, 2015
    Co-Authors: Bethany A. Stahl, Joshua B. Gross, Daniel I. Speiser, Todd H. Oakley, Nipham H. Patel, Douglas B. Gould, Meredith E. Protas
    Abstract:

    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.

Peter Trontelj - One of the best experts on this subject based on the ideXlab platform.

  • Phylogeography of subterranean and surface populations of water lice Asellus aquaticus (Crustacea: Isopoda)
    Molecular Ecology, 2004
    Co-Authors: Rudi Verovnik, Boris Sket, Peter Trontelj
    Abstract:

    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.

  • Bioaccumulation of palladium, platinum and rhodium from urban particulates and sediments by the freshwater isopod Asellus aquaticus.
    Water research, 2001
    Co-Authors: Mariella Moldovan, S Rauch, Milagros Gómez, M. Antonia Palacios, G M Morrison
    Abstract:

    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.

  • Platinum uptake by the freshwater isopod Asellus aquaticus in urban rivers.
    The Science of the total environment, 1999
    Co-Authors: S Rauch, G M Morrison
    Abstract:

    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.

  • Asellus aquaticus: A Model System for Historical Biogeography
    Encyclopedia of Caves, 2012
    Co-Authors: Rudi Verovnik, Marjeta Konec
    Abstract:

    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.

  • 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, 2009
    Co-Authors: Rudi Verovnik, Simona Prevorčnik, Jure Jugovic
    Abstract:

    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.

  • Phylogeography of subterranean and surface populations of water lice Asellus aquaticus (Crustacea: Isopoda)
    Molecular Ecology, 2004
    Co-Authors: Rudi Verovnik, Boris Sket, Peter Trontelj
    Abstract:

    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.