Support Service and Support. Learning Centre Asset. Corsi, B. Wightman, and M. Pasadena CA : WormBook; Related assets Products. Sona sCMOS. Advantages of using Drosophila Melanogaster as a Model Organism. Figure 6: Drosophila melanogaster image credit Shutterstock Wild D. Advantages of using Zebrafish as a Model Organism. Zebrafish Danio rerio are small tropical fish 2.
First used in the s in biological research, Zebrafish have proven to be excelle Advantages of using Xenopus Tropicalis as a Model Organism. In the biology laboratory X Advantages of using the Mouse as a Model Organism. Genotypes were characterized using microsatellite markers.
Developmental regulation and the behavior of dauer larvae are central to the C. Dauer larvae display active locomotion and a specific behavior called nictation, where they stand on their tail and wave their body in the air. These behaviors are thought to help dauers to find passing invertebrate hosts that they can use for their dispersal, such as isopods, snails and slugs. Together, dauer physiology and behavior suggest that this developmental stage plays a key role in C.
Over the year, in surveys performed in France and Germany, C. This seasonal dynamic is consistent with that observed in a semi-natural habitat, such as a compost heap, where C. These bottlenecks can lead to local extinctions.
Where this happens, a new genotype may colonize the compost heap when favorable conditions return Figure 4C. The spatio-temporal distribution of C. At the global scale, C. What is the pattern of C. What are the relevant vectors? Are humans now major vectors over large scales? Over a small scale, ongoing local population surveys will provide insights into migration patterns. Over large scales, selective sweeps estimated to date from — years ago have spread to different continents: their migration and selection might thus relate to human activity e.
What is C. Are there species that are very closely related to C. Increased sampling in poorly sampled and isolated geographical regions might provide access to divergent populations that did not undergo the recent selective sweeps and so inform us of C.
The sterols it requires might come from yeast or from the rotting plant substrate itself. What is the generation time and the number of generations per year in the wild?
The latter is surely far less than in the laboratory ca. Whether associated organisms have an influence on dauer formation has not been investigated. Where does C. What are the source populations? In temperate regions, C. We ignore how and where this organism survives winter, for example, whether it becomes associated with a carrier organism. It can reproduce either by self-fertilizing selfing hermaphrodites or by hermaphrodites XX breeding with males X0.
Hermaphrodites develop a female soma, and early in adulthood produce sperm in limited quantities ca. Males occur by non-disjunction of the X chromosomes at meiosis or in the progeny of male-hermaphrodite crosses. The non-disjunction of X chromosomes occurs overall at a low frequency e. This combination of metapopulation dynamics, a very low outcrossing rate and selection has a major impact on the C.
These three factors reduce the effective population size, and thus genetic diversity, and can wipe out diversity in a large genomic region. Indeed, positively selected alleles carry with them a large part of the genome by linkage, at the scale of megabases, particularly in the center of chromosomes where recombination is low.
For example, most C. Because of high linkage disequilibrium due to selfing, selective sweeps may cover large fractions of chromosomes and have erased much genetic diversity. Background selection the loss of non-deleterious variants due to selection against linked deleterious alleles may further reduce linked genetic diversity in this selfing species Rockman et al.
As a consequence, genome-wide pairwise genetic diversity is low ca. Overall, this means that much of the C. These extreme sweeps also mean that recent events in historical times, perhaps mediated by humans, may have had a significant impact on C.
The selfing lifestyle of C. Most animal species that reproduce by outcrossing suffer from inbreeding depression through the accumulation of deleterious recessive alleles.
In a predominantly self-fertilizing organism, such as C. Instead of inbreeding depression, wild C. This phenomenon is best explained by the fact that selfing creates and maintains beneficial gene combinations, while outcrossing favors their disruption. Thus, the progeny of outcrossing are less fit than are the progeny of selfing. However, at least under certain circumstances of experimental evolution, outbreeding may contribute positively to C. Contributing also to a reduction in effective outcrossing, C.
The zeel-1 and peel-1 genes are closely linked on chromosome I. The two allelic combinations, with both genes or without both genes, co-exist in the same geographical location, and the rest of the genome shows evidence of mixing. Yet this system, and other incompatibilities, may further contribute to lowering the effective outcrossing rate. Male-specific genes are overall conserved yet appear to be subject to relaxed selection Cutter, ; Thomas et al. Although C. On the male side, some aspects of mating behavior also appear to have degenerated, such as the ability to deposit a copulatory plug Palopoli et al.
The effect, and the future, of males in C. Within the last 5 years, many Caenorhabditis species have been newly discovered, due to the collaborative, worldwide sampling of rotting fruits, flowers and stems for new C. Today, 27 species are available in culture and many more are being isolated. The genus is presently composed of two basal species, C. The genus is globally distributed, with a higher species diversity in the tropics. The three selfing species shown in red on the accompanying figure are spread over several continents, while some male-female species have regional distributions.
Most species were collected in microhabitats similar to those described for C. However, given the unavoidable bias in sampling, some species may have unexplored preferred microhabitats and animal vectors Kiontke and Sudhaus, For example, Caenorhabditis japonica appears to be specifically associated with the hemipteran bug Parastrachia japonensis, which feeds in summer on fruits of Schoepfia jasminodora Kiontke et al.
These new findings enable comparative studies across the Caenorhabditis genus. For instance, closely related species, such as C. Phenotypic diversity in the genus also includes morphology, mating behavior Kiontke et al. An improved understanding of the ecology and the biology of the Caenorhabditis species, combined with comparative genomics, promise great insights into the evolutionary biology of the Caenorhabditis clade.
Phylogeny of the Caenorhabditis genus, with emphasis on the Elegans group, based on Kiontke et al. If not with E. A specific association is actually found between another Caenorhabditis species and another Drosophila species: this nematode species, C. Some organisms may act as both food and pathogen, or as both vector and predator. Other nematodes may be competitors for food but also predators.
For example, antidepressant drug action can be studied in a functional serotonergic synapse within the context of a whole organism. Although there are intrinsic limitations associated with C. Despite its apparent simplicity, the nematode worm Caenorhabditis elegans has developed into an important model for biomedical research, particularly in the functional characterization of novel drug targets that have been identified using genomics technologies. The cellular complexity and the conservation of disease pathways between C.
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