Wholly Virgin

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Chapter XIII Wholly Virgin

compiled by
Megan Ponce
Aaron Wong
May Kim
Expanded concepts surrounding the bdelloid
rotifer with respect to Olivia Judsons Dr.
Tatianas Sex Advice to All Creation
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Thesis Statement While numerous species reproduce
asexuality in nature, many scientists agree that
sex is necessary for long term evolution. The
Bdelloid rotifer provides evidence that exclusive
parthenogenesis is not an evolutionary dead end.
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Definitions

• Parthenogenesis Reproduction with out sex.
• Sex The recombination of different genetic DNA
  from different organisms by crossing over or by
  fertilization or by conjugation.
• Apodictic Reproduction with specialized tissues
  but not necessarily fertilization.
• Haplotype set of alleles that determine
  different antigens but are closely linked on one
  chromosome and inherited as a unit

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Are men really necessary? Usually, but not always.
Common name Bdelloid rotifer
Scientific name Philodina roseola
parthenogenetic
chaetonotid gastrotichs
aphid
Lay eggs that develop into genetically identical
embryos
whiptail
darwinulid ostracods
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No meiosis!
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How old is ancient?
85 Million Years 3 week lifespan 1.5 billion
generations
Fossil record goes back 40 million
The rest is based on molecular evidence
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Evidence of the evolutionary scandal
Sexual and asexual rotifers exist
Researchers looked at similar genes in many
species of rotifer
Asexual gene copies differed significantly from
sexual gene copies
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What studies show

• Bdelloid rotifer
• Chromosomes lack homologous pairs
• Chromosomes no segregation
• Each copy of a gene belongs to one of two
  lineages
• Lineages differ by 50

• Sexual Species
• Homologous pairs
• Two sets of chromosomes, segregated by haplotypes

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Other asexuals
discredited asexual
discredited asexual
chaetonotid gastrotichs
darwinulid ostracods
males and hermaphrodites found
facultative asexual
time will tell
whiptail
aphid
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Pattern of molecular evolution in asexual species
Asexuals may simply have slow rates of mutation
Cloning does not necessarily create identical
organisms
Mutations that accumulate are selected out
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Why sex should be more favorable

• Homologous genes repair mutations in DNA
• Genetic recombination most favorable traits
• Parental care
• Eliminate harmful mutations
• Higher chance of parasites/pathogens resistance

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Why Bdelloid rotifer is asexual.

• The Bdelloid rotifer can live in distilled water,
  seawater, and every salinity variation.
• She lives in temperatures between 10 and 30
  degrees Celsius.
• The genome is very flexible and may contribute to
  the successes of the Bdelloid rotifer.

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Mullers ratchet and Kondrashov's hatchet
Muller's Ratchet
The theory that in small populations Harmful
mutation rate gt natural selection removes
mutations
Kondrashov's Hatchet
The theory that in large populations Harmful
mutations build up, mutations die out
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Endosymbionts
Endosymbiont The symbiont lives within the body
of the host. In asexual organisms, an
endosymbiont can increase the likelihood of
survival.
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Epigenetic effects

• Epigenetic A chain of developmental processes in
  epigenesist that lead from genotype to phenotype
  after the initial action of the genes. In the
  case of Myzus persicae an aphid, the heterozygous
  have the a resistance to certain pesticides, but
  when they are homozygous recessive they lose the
  resistance. This is caused by a change of the
  process of epigenesist.

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How to escape the red queen
Diversity - 360 species discovered
Mutations neutral
Run away from parasites
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Anhydrobiosis
-Escape method from parasites In dormant state,
can be flushed away, blown away by wind, or even
outlast parasites
A type of Cryptobiosis the reversible cessation
of metabolism under extreme environmental
conditions
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Conclusion

• There is strong evidence that the Bdelloid
  rotifer is an asexual that has had no sexual gene
  exchange for over 85 million years.

• Asexuality can be a way for a species to build up
  mutations that may allow them to evolve at an
  accelerated rate, which can be an advantage over
  the sexual species, but more research is needed
  to understand this better.

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Resources
Andrea Gandolfi,, Ian R. Sanders, Valeria Rossi
and Paolo Menozzi (2003). Evidence of
Recombination in Putative Ancient Asexuals.
Society for Molecular Biology and Evolution.
Retrieved 16 April 2005 from http//mbe.oupjourna
ls.org/cgi/content/full/20/5/754. C. William
Birky, Jr (2004). Bdelloid rotifers revisited.
The National Academy of Sciences. Retrieved 16
April from 2005 http//www.pubmedcentral.nih.gov/
articlerender.fcgi?toolpubmedp ubmedid14981265
Hales, D, Sunnucks, P, Wilson, A. (2003).
Heritable genetic variation and potential for
adaptive evolution in asexual aphids. Biological
Journal of the Linnaean Society, 79, page
115-135. Judson, Olivia (2003). Dr. Tatianas Sex
Advice to All Creation. Henry Holt and Company
New York. Pages 212-232.
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Resources
Martens K, Rossetti G, Horne DJ (2003).
Koninklijk Belgisch Instituut voor
Natuurwetenschappe. Retrieved 16 April 2005 from
http//www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd
Retrievedbpu bmeddoptAbstractlist_uids12713
746 Schon I, Martens K (2003). No slave to sex.
Royal Belgian Institute of Natural Sciences.
Retrieved 14 April 2005 from http//www.ncbi.nlm.
nih.gov/entrez/query.fcgi?cmdRetrievedbpu bmed
doptAbstractlist_uids12737661 Tunnacliffe A,
Lapinski J (2003). Resurrecting Van Leeuwenhoek's
rotifers a reappraisal of the role of
disaccharides in anhydrobiosis. Institute of
Biotechnology, University of Cambridge.
Retrieved 16 April 2005 from http//www.ncbi.nlm
.nih.gov/entrez/query.fcgi?cmdRetrievedbpu bmed
doptAbstractlist_uids14561331 Welch, Mark,
David B (2004). Mark Welch, and Matthew Meselson.
Cytogenetic evidence for asexual evolution of
bdelloid rotifers. The National Academy of
Sciences. Retrieved 15 April 2005 from
http//www.pubmedcentral.nih.gov/articlerender.fc
gi?toolpubmedp ubmedid14747655
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Resources list of figures
Ahydrobiosis. Retrieved 22 May 2005 from
http//users.unimi.it/ricci/html/anhydro.htm Aphi
d. Retrieved 21 May 2005 from http//www.nysaes.c
ornell.edu/ent/factsheets/images/gpa-nymph1b.jpg B
delloid. Retrieved 25 May 2005 from
http//www.sciencenews.org/articles/20000520/fob6
.asp Bdelloid rotifer. Retrieved 20 May 2005 from
http//www.sciencenews.org/articles/20030628/a372
3_2645.jpg Bdelloid rotifer. Retrieved 25 May
2005 from http//www.treknature.com/images/photos
/338/bdelloid__rotifer.jpg Darwinulid ostracods.
Retrieved 23 May 2005 from http//www.sciencenews
.org/articles/20030628/a3723_1859.jpg Evolution.
Retrieved 25 May 2005 from http//lifewithalacrit
y.blogs.com/photos/uncategorized/evolution.jpg Mex
ico Whiptail. Retrieved 24 May 2005 from
http//www.arts.arizona.edu/herp/asco2.jpg
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Resources list of figures
Ostracod shells. Retrieved 22 May 2005 from
http//www2.una.edu/microaquarium/images/Arthropo
ds/Crustaceans/ ostracods/OstracodShells1943cm.jpg
Red Queen. Retrieved 24 May 2005 from
http//www.funkervogt.net/News/redqueen.gif Red
Queen Software. Retrieved 24 May 2005 from
http//www.redqueensoftware.com/images/Index20pa
ge_r02_c3.gif Rotifer. Retrieved 21 May 2005 from
http//fs6.depauw.edu50080/cfornari/images/roti
001b.gif Rotifer. Retrieved 22 May 2005 from
http//www.microimaging.ca/rotifer1.jpg Rotifer.
Retrieved 25 May 2005 from http//www.microimaging
.ca/rotifer2.jpg Rotifera. Retrieved 24 May 2005
from http//www.ucmp.berkeley.edu/phyla/rotifera/
rotiferclad.gif