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Topic: Bdelloid

	Bdelloid - Wikipedia, the free encyclopedia
		The bdelloids (Bdelloidea) are a class of rotifers, found in freshwater and moist soil.
		Bdelloids have been of interest to those interested in the evolutionary role of sexual reproduction, because it has disappeared entirely from the group: males are unknown, and females reproduce exclusively by parthenogenesis.
		Bdelloids respond to environmental stresses by entering a state of dormancy known as anhydrobiosis.
	en.wikipedia.org /wiki/Bdelloid (221 words)

	Ludmila A. Kutikova. Variability in obligatory parthenogenetic rotifers (Rotifera, Bdelloida).
		Bdelloid rotifers have relatively uniform structure of body adapted to life, in spatially restricted water film of edaphon, in mosses, lichens, leaf and fir litter where they are mostly spread and also in the littoral and profundal of fresh waters, in benthos and among aquatic vegetation.
		Bdelloids have false segmentation of the body with a definite number of segments in every section: 3 segments in head and neck, 6 segments in the body, 3-6 segments in foot.
		Therefore it can be assumed that obligatory parthenogenetic bdelloid rotifers invaded terrestrial biotopes on the early stage of their evolution; they are characterized by slow evolution rates as compared to heterogonetic monogononts; the variability of bdelloids is of principally of different character and concerns morphological structures of a lower taxonomic rank.
	www.zin.ru /annrep/2000/13.html (1399 words)

	Fresh Water Rotifers: A general introduction with photomicrographs of bdelloid rotifers. (Site not responding. Last check: 2007-10-12)
		Bdelloid rotifers are the commonest variety found in fresh water.
		In some bdelloids, the young develop to maturity within the body cavity and are born live.
		A bdelloid rotifer browses in a mass of decaying vegetation.
	www.micrographia.com /specbiol/rotife/homebdel/bdel0100.htm (893 words)

	bdelloid (Site not responding. Last check: 2007-10-12)
		Bdelloids are commonly found in freshwater and soils, as they can live in the thin water film surrounding soil particles, mosses and lichens.
		All bdelloids are able to creep on surfaces with a leech-like movement, and some swim using the cilia of the corona.
		Bdelloids reproduce through parthenogenesis and populations consist of female animals, only.
	users.unimi.it /ricci/html/bdelloid.htm (168 words)

	www.amateurmicroscopy.net...Bdelloid Rotifers
		When traveling from one location to another, bdelloid rotifers anchor their toes to the substrate, extend their bodies fully, anchor the rostrum to the substrate, and then release the toes and pull the rest of the body forward to the rostrum.
		Bdelloid rotifers are not strictly filter feeders and can spend a considerable amount of time foraging for food particles, too.
		Bdelloid rotifer populations can run as high as 1,000/liter of pond water making bdelloid rotifers one of the most prolific and numerous of the Metazoans.
	amateurmicroscopy.photomacrography.net /Articles/Rotifers/rotifers.htm (1344 words)

	Meselson Laboratory - The Bay Paul Center Portal
		Bdelloid rotifers are small fresh-water invertebrates comprising four families, 19 genera, and some 360 described species.
		This would be consistent with the lack of retrotransposons in bdelloids and suggests that bdelloids either lost such elements close to the time when sex was lost, either by chance or else by some active mechanism of suppression or removal.
		Further opportunities for utilizing bdelloid rotifers in the study of basic genetic problems include investigations of DNA repair, genetic silencing, heterosis, population genetic diversity, and response to selection.
	jbpc.mbl.edu /labs-meselson.html (1250 words)

	Bdelloids: No sex for over 40 million years: Science News Online, May 20, 2000 (Site not responding. Last check: 2007-10-12)
		Microscopic bdelloid rotifers have seemingly evolved without sex for millions of years and probably don't exist in male form, say Harvard University biologists.
		That's the age of the oldest bdelloid recovered from amber.
		Extrapolating from sexual rotifers, bdelloid specialist Bill Birky at the University of Arizona in Tucson speculates that males, if they existed, would be "small swimming hypodermic syringes full of sperm." He pictures them zooming up to females to inject sperm right through the body wall.
	www.sciencenews.org /20000520/fob6.asp (747 words)

	Survival of the fittest females / Tiny animals evolve through the ages without males' help
		New findings on bdelloid evolution have been developed by Jessica L. Mark Welch of the Josephine Bay Paul Center at the Woods Hole lab; her husband, David Mark Welch of Harvard; and Matthew Meselson, the famed Harvard biologist known not only as an expert on evolution but also on the biological effects of germ warfare.
		There are no males in some 370 known species of bdelloid rotifers, and although every one of the tiny animals is a female, they have managed to evolve from species to species with their own genes apparently doing the entire job, the researchers are discovering.
		From the bodies of ancient bdelloid species preserved in amber, and from "molecular clocks" estimating the mutation rates of the animals, the researchers concluded that the tiny animals have been around for at least 50 million years, and perhaps 100 million.
	www.sfgate.com /cgi-bin/article.cgi?f=/c/a/2004/03/22/MNG5U5OENJ1.DTL&type=science (1039 words)

	Bdelloidea (Site not responding. Last check: 2007-10-12)
		Bdelloids inhabit freshwater and most are found in intermittently moist terrestrial mosses and soil but some are benthic in aquatic habitats.
		Bdelloid rotifers have the ability to undergo cryptobiosis and withstand extended periods of desiccation and return to metabolic activity when wetted.
		The In bdelloids the lorica is in rings, or annuli, that telescope into each other to change the length of the worm (Fig 1, 23-17).
	www.lander.edu /rsfox/310BdelloideaLab.html (1948 words)

	Dr Tatiana's Sex Advice To All Creation - What Critics Say (Site not responding. Last check: 2007-10-12)
		It is the evidence that an obscure group of animals called bdelloid rotifers are "ancient asexuals." Many life forms are exclusive cloners, but their biological make-up suggests that we humans could not do without sex for long.
		Bdelloids are complex animals, and evolutionarily ancient; they have been around for 100m years or more.
		Bdelloid rotifers are not the only creatures in which pairs of genes differ within an individual because of a past history of cloning.
	www.drtatiana.com /critics/prospect_magazine.shtml (1737 words)

	[No title]
		Bdelloids live in fresh water and moist habitats around the world.
		If it is true that the bdelloids have evolved asexually, this would challenge the current evolutionary theory about the importance of sexual reproduction in evolution.
		If bdelloid rotifers have indeed evolved without sexual reproduction and genetic recombination for millions of years, they represent a uniquely advantageous system for studing why sex exists.
	www.whozoo.org /Intro2001/Explorations/MJS_bdelloids.doc (846 words)

	SNAIL'S TALES: The thing from the birdbath
		Bdelloid rotifers live in ponds, lakes, creeks, wet soil, mosses, leafy lichens, bird baths and any other place where water may accumulate even intermittently.
		Bdelloid rotifers (class Bdelloidea), with about 350 or so known species, have one characteristic that makes them stand out among all other animals: they are the largest group of animals that reproduce exclusively by parthenogenesis
		Every individual bdelloid is a female that produces unfertilized eggs from which more females hatch and so on.
	snailstales.blogspot.com /2005/10/thing-from-birdbath.html (673 words)

	Life Without Sex: Science News Online, June 28, 2003 (Site not responding. Last check: 2007-10-12)
		Biologists have mused that there might be something funny about the sexual history of bdelloid rotifers, one of the classes of a phylum of little stalk-like water animals crowned with a characteristic circle of hairlike cilia.
		The simplest explanation of the patterns, the researchers contended, was that in the asexuals, there had been no reshuffling of the genome, as occurs during sex, so an individual rotifer's two copies of a gene had each had plenty of time to independently build up quirky mutations.
		Geneticists argue that this bdelloid rotifer's ancestors stopped having sex perhaps as long ago as 80 million to 100 million years ago.
	www.sciencenews.org /articles/20030628/bob7.asp (1985 words)

	New_Scientist_1996
		Nor, it turns out, are the bdelloid rotifers the only sexless organisms that seem to have dug their evolutionary heels in and survived against the odds.
		And the painful truth is that the discovery of just one male bdelloid, fossilised or alive, would instantly tarnish the bdelloid's reputation and dent biologists' hopes of using these ancient virgins to crack the mystery of sex.
		It's probably no accident, either, that notorious asexuals like the bdelloid rotifers and Darwinulid ostracods live in freshwater habitats: dispersal to avoid parasites and found new colonies might be easier in water.
	courses.missouristate.edu /mcb095f/bio370/papers/virginal_rotifers.htm (3090 words)

	MBL scientists confirm evolutionary exception
		Bdelloids appear to have given up sex 50 million years ago, yet the organism has evolved into 370 described species.
		While the researchers previously demonstrated that bdelloid genomes contain two or more divergent gene copies, an observation consistent with long-term asexual reproduction, a significant shortcoming of their approach was the inability to detect nearly identical gene pairs, as might result from inbreeding or other rare forms of sexual reproduction.
		To overcome this methodical shortcoming and conclusively demonstrate that bdelloids are, in fact, completely asexual, Mark Welch and her colleagues painstakingly analyzed the genome of the bdelloid species, Philodina roseola.
	www.eurekalert.org /pub_releases/2004-01/mbl-msc012004.php (841 words)

	Dept of MCB, Harvard U: Faculty and Research - Meselson
		Bdelloid rotifers are small fresh-water invertebrates comprising four families, 19 genera, and some 350 species.
		While we are proceeding with this and with experiments to detect the possible occurrence in bdelloids of certain obscure and unprecedented forms of genetic exchange, we have also begun to examine bdelloid genomes for characteristics that may be associated with long-term asexuality.
		It would therefor appear that active retrotransposons cannot be retained in asexual lines over evolutionary time periods or that the absence of such elements is a pre-condition for the avoidance of extinction in asexual lines, a possibility that would ascribe to sexual reproduction a role in limiting the accumulation of insertion mutations.
	golgi.harvard.edu /Faculty/Meselson.html (878 words)

	Life Without Sex. - Unexplained - IN SEARCH FOR TRUTH - RIN.RU (Site not responding. Last check: 2007-10-12)
		This group of tiny water creatures, called bdelloid rotifers, is thriving in fresh water and soggy land worldwide despite, seemingly, no sex for at least 40 million years.
		The fossil record so far hasn't said much about the history of bdelloid rotifers-only that some specimens found in amber dating from 35 to 40 million years ago didn't include any obvious males.
		Bdelloids seem to be getting rid of menacing transposable elements, but so far as biologists know, don't seem bothered by an abundance of other mutations.
	istina.rin.ru /eng/ufo/text/89.html (1668 words)

	Introduction to the Rotifera
		A particular class of rotifers called bdelloids can be found living in almost all freshwater environments, and occasionally in brackish and marine waters.
		Bdelloids are known for their remarkable ability to survive drying through a process known as cryptobiosis.
		Laboratory Exercise on Bdelloid Rotifer Anatomy by Richard Fox.
	www.ucmp.berkeley.edu /phyla/rotifera/rotifera.html (1701 words)

	Topics
		Starve and survive: stress tolerance and life-history traits of a bdelloid rotifer.
		Evolutionary dynamics of ‘the’ bdelloid and monogonont rotifer life-history patterns.
		Bdelloid rotifer as model system to study development biology in space.
	users.unimi.it /ricci/html/papers.htm (492 words)

	BBC News \| SCI/TECH \| The breed without males
		For example, a species of scale-insects was thought to be only female, until minuscule males were found clinging to their legs.
		However, the DNA of the bdelloids shows a very high probability that they are all female and have been reproducing without sexual partners.
		The next step for the Harvard team, which report their findings in the journal Science, is to study the genes to find out how the bdelloids - which range in size from 0.1 mm to 1 mm - have survived for this long without being killed off by dangerous mutations.
	news.bbc.co.uk /1/hi/sci/tech/759579.stm (414 words)

	MBL researchers probe how an ancient microbe thrives and evolves without sex
		To learn more about the bdelloid rotifers' unique ability to evolve without sex, Arkhipova and Meselson studied portions of different bdelloid rotifer genomes and surveyed the diversity, structural organization, and patterns of evolution of DNA transposons.
		The scientists found that DNA transposons in bdelloid rotifers are in a different, perhaps less damaging, location than those found in other creatures.
		Indeed, many of them appear to be located at the tip of the chromosome in an area called the telomere, different from the gene-rich portions of the genome, whereas most species tend to have DNA transposons dispersed throughout their genome.
	www.eurekalert.org /pub_releases/2005-08/mbl-mrp080405.php (472 words)

	Interview with Olivia Judson -- ReadersRead.com
		Bdelloid rotifers are notorious in evolutionary circles because they do something that evolutionary theorists thought was impossible.
		Having the bdelloid rotifer as a guest on a TV show seemed to me to be a good way of keeping the chapter focused on this question.
		However, the rotifer is able to show (by referring to the very latest studies) that in fact, the bdelloid rotifers really are ancient asexuals.
	www.readersread.com /features/oliviajudson.htm (1859 words)

	Trehalose and suspended animation
		Some plants and animals can easily enter a state of suspended animation, during which the metabolic activity of their cells can effectively be stopped, and the delicate architecture of the plasma membranes and intracellular organelles protected against extremes of cold, heat, radiation and other insults.
		Examples which we can easily observe are dried yeast, brine shrimp eggs, tardigrades and certain metazoa such as bdelloid rotifers, which I have chosen to illustrate the process.
		The bdelloids in fig.1 are encysted - left to dry out on a slide, and they have been in this state for several weeks, lying on a slide on my desk.
	www.microscopy-uk.org.uk /mag/artnov02/hbjtrehalose.html (934 words)

	Rates of nucleotide substitution in sexual and anciently asexual rotifers -- Welch and Meselson 98 (12): 6720 -- ...
		Bdelloid remains have been reported in 30-40-million-year-old amber (24) and measurements of DNA sequence divergence suggest
		Scatter plot of unadjusted distances OB (bdelloids) and OM (monogononts) between the common bdelloid-monogonont ancestor and bdelloids or monogononts, respectively, based on 4-fold degenerate differences (A) and amino acid differences (B).
		for hsp82 are applicable to bdelloid and monogonont genomes in
	www.pnas.org /cgi/content/full/98/12/6720 (3178 words)

	IngentaConnect Patterns of diversity in microscopic animals: are they comparable... (Site not responding. Last check: 2007-10-12)
		Bdelloid rotifers showed low local species richness (alpha diversity), with strong habitat selection, as observed in larger organisms.
		Bdelloid rotifers have some of the peculiarities of protist biodiversity, although at slightly different spatial scales, thus confirming the idea of a major change in biodiversity patterns among organisms shorter than 2 mm.
		We suggest two possible explanations for the observed patterns: (1) dispersal is very rare, and not all bdelloid clones are arriving everywhere; and (2) dispersal is effective in displacing propagules, but environmental heterogeneity is very high and prevents many species from colonizing a given patch of moss.
	www.ingentaconnect.com /content/bsc/geb/2006/00000015/00000002/art00004 (383 words)

	Anhydrobiosis without trehalose in bdelloid rotifers. (Site not responding. Last check: 2007-10-12)
		Eukaryotes able to withstand desiccation enter a state of suspended animation known as anhydrobiosis, which is thought to require accumulation of the non-reducing disaccharides trehalose (animals, fungi) and sucrose (plants), acting as water replacement molecules and vitrifying agents.
		We now show that clonal populations of bdelloid rotifers Philodina roseola and Adineta vaga exhibit excellent desiccation tolerance, but that trehalose and other disaccharides are absent from carbohydrate extracts of dried animals.
		Furthermore, trehalose synthase genes (tps) were not found in rotifer genomes.
	www.cryonet.org /cgi-bin/dsp.cgi?msg=22738 (135 words)

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