Phynotypic plasticity of Daphnia pulex in the presence of invertebrate predators: morphological and

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Phynotypic plasticity of Daphnia pulex in the
presence of invertebrate predators morphological
and life history responses

• Nguyen Manh Duy Linh

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INTRODUCTION

• Kingdom Animalia
• Phylum Arthropoda
• Class Branchiopoda
• Order Cladocera
• Family Daphniidae
• Genus Daphnia
• Species Daphnia pulex

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EXPERIMENTS

• 2 clones of Daphnia pulex (A and B).
• Exp. 1 (Chaoborus flavicans lavae).
• 5 Chaoborus larvae 25 newborn Daphnia.
• Exp. 2 (Notonecta glauca adult).
• 1 adult Notonecta 15 adult Daphnia.
• Exp. 3 (Chaoborus Notonecta).
• 1 adult Notonecta 5 Chaoborus 40 Daphnia
  (clone B)
• Exp. 4 (Chaoborus Notonecta extraction)
• 1 adult Notonecta 20 Chaoborus test Daphnids
  (clone A)

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RESULTS-NECK SPINE INDUCTION

• Control Clone A no neck spine
• Clone B 86 (individuals have
  neck spine).
• Exp.1 Clone A single neck teeth (in 2nd and 3rd
  instars).
• Clone B wide range of number of neck
  teeth (3-5 piece in 1st -4th instars, up to 8th
  no spines).
• Exp. 2 no differences (between treatment and
  control).
• Exp. 3 Exp. 4 no differences.

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RESULTS-TAIL SPINE

• Control Clone A B inverse ratio to instar
  number.
• Exp. 1 Clone A no differences (1st, 3rd, 5th
  instar slightly longer ).
• Clone B significantly longer
• Exp. 2 Clone A no differences (1st instar
  shorter).
• Clone B 1st instar shorter others longer
• Exp. 3 response similarly to Exp. 2 (the
  influence of Chaoborus seemed to be suppressed).
• Exp. 4 1st and 2nd instars longer (slightly
  dominance of the Chaoborus effect over the
  Notonecta effect).

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RESULTS-BODY SIZE

• Control Clone A increase until 10th instar
• Clone B increase until 9th
  instar
• (Clone A were smaller clone B in all instars).
• Exp. 1 Clone A larger (1st and 2nd instar, from
  3rd instar no difffernces).
• Clone B larger (adult significantly larger).
• Exp. 2 Clone A first 3 instars smaller
  4th-7th instar no differences, 8th-10th instar
  smaller.
• (in this treatment the clones reacted quite
  differently)
• Clone B no differences (6th, 9th larger
  Exp.1).
• Exp. 3 newborn smaller, adult larger ( single
  predator).
• Exp. 4 larger (1st, 4th, 5th) effected by
  Chaoborus.
• (Effect of Notonecta appeared to be suppressed)

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RESULTS-AGE OF MATURITY

• Control Clone A start at 6th instar (18.5)
• Clone B start at 5th instar
  (2.1)
• Exp. 1 Clone A lower (2.5) (delay of maturity)
• Clone B no gravid females in 5th
  and 6th instar (a clearly delay of maturity)
• Exp. 2 Clone A maturation was earlier (8.5
  carry eggs at 5th instar)
• Clone B 6th instar more gravid females (delay by
  one instar relative to the control)
• Exp. 3 start at 5th instar (higher than control
  in later stages)
• Exp. 4 all reached maturity in 7th instar
  (control 63)

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RESULTS-CLUTCH SIZE

• Control Clone A direct ratio to instar number
• Clone B Fluctuation
• Exp. 1 Clone A B produced less eggs than the
  controls.
• Exp. 2 Clone A B produced more offsprings
  than the controls.
• Exp. 3 Exp. 4 similar to Exp. 2

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CONCLUSIONS

• The young stages of Daphnia pulex which produce
  neck teeth are also the preferred food of
  Chaoborus. It is not clear wether the small
  spines protect the animal effectively against
  predators.
• Daphnia pulex showed phenotypic modifications of
  body size and age at maturity.
• Reduce egg number, delay maturity and large size
  of newborn in the Chaoborus treatment provide the
  best strategy to escape from the predators that
  prefer small animal.

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THANK YOU !