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Carnivorous Plants and Insects

Carnivorous Plants and Insects. Plant-Animal Interactions. Tom Caudle. Background Protocarnivorous plants How they trap insects How they evolved. Background.

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Carnivorous Plants and Insects

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  1. Carnivorous Plants and Insects Plant-Animal Interactions Tom Caudle

  2. Background • Protocarnivorous plants • How they trap insects • How they evolved

  3. Background • “Plants that derive some or most of their nutrients (but not energy) from trapping and consuming animals, typically insects and other arthropods”. • Acidic bogs, rock outcroppings • Around 625 species that are true carnivores

  4. Protocarnivorous Plants • Lack ability to directly digest or absorb nutrients from prey • Rely on bacteria or internal food webs • Darlingtoniacalifornica • Relies on symbiotic bacteria and protozoa

  5. Trapping Methods • Five trapping mechanisms: • Pitfall traps (pitcher plants) • Flypaper traps • Snap traps • Bladder traps • Lobster-pot traps

  6. Pitfall Traps • Rolled leaves with enzymes or bacteria in a pool of liquid (phytotelmata) at base • Insects attracted by nectar “bribes” • Sides are slippery • Some have downward pointing hairs • Other mechanisms to trap prey – false exits

  7. Flypaper Traps • Utilise mucilage – polar glycoprotein used as glue • Secreted by glands on leaf • Can be projected (Droseracapensis), or flat (Pinguiculagigantea) • Leaves curl around prey to stop escape – thigmotrophic growth •  Droseraburmanii can bend 180° in ~ 1min

  8. Snap Traps • Leaves divided into two lobes, hinged along the middle • Trigger hairs in the lobes sensitive to touch • Action potential to midrib • Ions pumped out creating osmotic gradient • Cells collapse, lobes under tension, snap shut • Continuous stimulation keeps lobes shut, encourages growth

  9. Bladder and Lobster-pot Traps • Bladder Traps: • Exclusive to genus Utricularia(bladderworts) • Ions pumped out of bladders • Small hinged opening releases vacum • Lobster-pot Traps: • Easy to enter chamber • Escape hindered by bristles, or hard to find exit • Prey forced to move down chamber • Water movement

  10. Evolution • Hairy-leaf theory: • All traps are based on hairy leaves and folding • Hairs trap water droplets, insects drown in water • Bacteria decompose, nutrients absorbed into leaves • More water held, selective advantage  pitfall traps • Bladder traps originate from aquatic plants with pitfall traps

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