L20 - Microinvertebrates

• What are invertebrates more common, abundant, and diverse than?

  Vertebrates
• Why do most people know little about invertebrates?

  They are often small and live out of sight
• Where do invertebrates often live that makes them hard to observe?

  • Underwater
  • Underground
  • Tree canopies
  • Inside other animals (as parasites)
• List some phyla of invertebrates mentioned in the material.

  • Acanthocephala
  • Chordata
  • Cnidaria
  • Arthropoda
  • Mollusca
  • Tardigrada
  • Nematoda
  • Platyhelminthes
• What size are micro-invertebrates typically?

  Too small to be seen with the naked eye
• How many species of rotifers are there approximately?

  ~2,000 species
• What is the morphological diversity of rotifers like?

  They exhibit huge morphological diversity
• What are the four classes of rotifers?

  • Monogononta: ~1000 species, free living
  • Acanthocephala: ~1200 species, parasitic
  • Bdelloidea: ~450 species, free living
  • Seisonidea: ~2 species, live on gills of crustaceans
• What occurs during sexual reproduction in rotifers?

  Meiosis occurs, producing haploid gametes
• What is a pro and con of sexual reproduction in rotifers?

  Pro: Genetic diversity; Con: Requires fertilization
• What happens during asexual reproduction in rotifers?

  No meiosis occurs, producing diploid gametes
• What is a pro and con of asexual reproduction in rotifers?

  Pro: No fertilization required; Con: No genetic diversity
• What is cyclical parthenogenesis in Monogononta rotifers?

  • Fertilization leads to dormant zygote
  • No fertilization leads to dwarf males
• Why are bdelloid rotifers considered an "evolutionary scandal"?

  • Asexual reproduction is usually a dead end
  • They have survived asexual for ~80 million years
• How do bdelloid rotifers survive desiccation?

  By entering cryptobiosis, a hidden life state
• What is the 'tun' state in bdelloid rotifers?

  A state with no aging and high resistance
• What environmental stress can bdelloid rotifers resist in cryptobiotic state?

  Gamma radiation
• What is horizontal gene transfer (HGT)?

  • Transfer of a gene between non-direct descendants
  • Allows bdelloids to produce unique proteins
• How does HGT benefit bdelloid rotifers?

  It allows them to make proteins they couldn't otherwise
• What are tardigrades commonly known as?

  Water bears

  
• What is the size range of tardigrades?

  50-2100 μm

  
• How many legs do tardigrades have?

  Eight legs
• What habitats do tardigrades inhabit?

  • Freshwater
  • Marine
  • Terrestrial (mosses)
• What types of reproduction do tardigrades undergo?

  Both sexual and asexual reproduction
• What clade are tardigrades classified within?

  Panarthropoda
• How do tardigrades resist environmental stressors?

  • Via cryptobiosis
  • Different dormancy types depending on stressor

  
• What are tardigrades considered in research?

  Model organisms for space and aging research

  
• What is the 'sleeping beauty' concept in tardigrades?

  Reduced aging in the frozen state
• What is the significance of HGT in tardigrades?

  It may contribute to their survival strategies