Project description:Larval settlement and metamorphosis is a vital transition period for marine invertebrates and can have far-reaching effects on the ecology and evolution of a species. To explore the molecular mechanisms of this critical process in a non-model organism, the tropical abalone Haliotis asinina, we employed cDNA microarray methods. By comparing gene expression profiles through mid to late larval development and metamorphosis, we identified 144 genes as likely candidates for a role in competence and/or metamorphosis. Gene characterization showed that ~60% of these were significantly similar to previously described genes from other taxa, while ~40% had no significant similarities to any known genes. A high 49.3% of genes were gastropod- or abalone-specific, but none appear to be Lophotrochozoan-specific, despite the fact that metamorphosis is thought to have had a separate origin in this group. Based on temporal expression profiles, the differentially expressed larval and postlarval genes can be clustered into 5 categories that reveal there are strikingly different transcriptional patterns occurring during this phase of development. Some classes of gene activation are contingent upon exogenous cues and correlate with the initiation of settlement and metamorphosis. Importantly, there is also extensive gene activity associated with the endogenous attainment of competence, which occurs prior to, and independent of, the exogenous induction of settlement. Our results show that as the haliotid veliger larva matures, it requires the coordinated regulation of temporally different batteries of genes involved in a wide range of physiological and developmental processes associated with colonisation of the benthos. Although the signalling pathways operating at metamorphosis may be conserved across the animal kingdom, it appears they are regulating the expression of novel genes specific to abalone, gastropods and molluscs during H. asinina metamorphosis. Keywords: timecourse; metamorphosis; marine ecology

Project description:Larval settlement and metamorphosis is a vital transition period for marine invertebrates and can have far-reaching effects on the ecology and evolution of a species. To explore the molecular mechanisms of this critical process in a non-model organism, the tropical abalone Haliotis asinina, we employed cDNA microarray methods. By comparing gene expression profiles through mid to late larval development and metamorphosis, we identified 144 genes as likely candidates for a role in competence and/or metamorphosis. Gene characterization showed that ~60% of these were significantly similar to previously described genes from other taxa, while ~40% had no significant similarities to any known genes. A high 49.3% of genes were gastropod- or abalone-specific, but none appear to be Lophotrochozoan-specific, despite the fact that metamorphosis is thought to have had a separate origin in this group. Based on temporal expression profiles, the differentially expressed larval and postlarval genes can be clustered into 5 categories that reveal there are strikingly different transcriptional patterns occurring during this phase of development. Some classes of gene activation are contingent upon exogenous cues and correlate with the initiation of settlement and metamorphosis. Importantly, there is also extensive gene activity associated with the endogenous attainment of competence, which occurs prior to, and independent of, the exogenous induction of settlement. Our results show that as the haliotid veliger larva matures, it requires the coordinated regulation of temporally different batteries of genes involved in a wide range of physiological and developmental processes associated with colonisation of the benthos. Although the signalling pathways operating at metamorphosis may be conserved across the animal kingdom, it appears they are regulating the expression of novel genes specific to abalone, gastropods and molluscs during H. asinina metamorphosis. Keywords: timecourse; metamorphosis; marine ecology Each microarray slide contained a different combination of 2 of the 9 developmental stages used in the experiment (66 hpf, 78 hpf, 90 hpf, 108 hpf, 120 hpf, 144 hpf, 12 hpi, 24 hpi, 48 hpi). Each developmental stage was subjected to 4 hybridisations â amounting to 4 technical replicates per stage - in a loop design (Churchill 2002; Oleksiak et al. 2002). This design led to raw data consisting of 72 measurements - 9 stages with 8 replicates (including 2 replicates per chip) - for each of 5541 spots.

Project description:Conceptual models of adaptive divergence and ecological speciation in sympatry predict differential resource use, phenotype-environment correlations, and reduced gene flow among diverging phenotypes. While these predictions have been assessed in past studies, connections among them have rarely been assessed collectively. We examined relationships among phenotypic, ecological, and genetic variation in Arctic charr (Salvelinus alpinus) from six Icelandic localities that have undergone varying degrees of divergence into sympatric benthic and pelagic morphs. We characterized morphological variation with geometric morphometrics, tested for differential resource use between morphs using stable isotopes, and inferred the amount of gene flow from single nucleotide polymorphisms. Analysis of stable isotopic signatures indicated that sympatric morphs showed similar difference in resource use across populations, likely arising from the common utilization of niche space within each population. Carbon isotopic signature was also a significant predictor of individual variation in body shape and size, suggesting that variation in benthic and pelagic resource use is associated with phenotypic variation. The estimated percentage of hybrids between sympatric morphs varied across populations (from 0% to 15.6%) but the majority of fish had genotypes (ancestry coefficients) characteristic of pure morphs. Despite evidence of reduced gene flow between sympatric morphs, we did not detect the expected negative relationship between divergence in resource use and gene flow. Three lakes showed the expected pattern, but morphs in the fourth showed no detectable hybridization and had relatively low differences in resource use between them. This coupled with the finding that resource use and genetic differentiation had differential effects on body shape variation across populations suggests that reproductive isolation maintains phenotypic divergence between benthic and pelagic morphs when the effects of resource use are relatively low. Our ability to assess relationships between phenotype, ecology, and genetics deepens our understanding of the processes underlying adaptive divergence in sympatry.

Dataset Information

Miles down for lunch: deep-sea in situ observations of Arctic finned octopods Cirroteuthis muelleri suggest pelagic-benthic feeding migration.

Publications

Miles down for lunch: deep-sea <i>in situ</i> observations of Arctic finned octopods <i>Cirroteuthis muelleri</i> suggest pelagic-benthic feeding migration.

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