Adaptations to High Current in the Giant Green Anemone Anthopleura xanthogrammica

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Adaptations to High Current in the Giant Green
Anemone Anthopleura xanthogrammica

• Rosemary Byrne

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Meeting Biological Needs in a High Current
Environment

• Body Structure (protection from water pressure
  and abrasion from suspended materials)
• Reproductive Success (meeting of partners/gametes
  and survivorship of young)
• Food Acquisition (finding, capturing prey)

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Body Structure Adaptations in Anthopleura
xanthogrammica

• Allometric growth-Hides in boundary layer.
• Retractile body

• Adhesive Structures (Verrucae)
• Binds to substrate

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Reproductive Strategy

• Sexual Reproduction Only!

A. xanthogrammica are broadcast spawners

• Males release sperm into water column
• Stimulates females to release eggs
• External fertilization
• Permits high gene flow?

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Is Broadcast Spawning an Effective Adaptation to
High Current?

• Planula larvae in the plankton have high
  dispersal potential
• Dispersal range is dependent on larval time to
  settlement
• But larvae are very difficult to track in the
  open ocean!

Analyze adults for population structure
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What DNA Sequence Might Show Us If the Larvae
Travel Long Distances
Travel Short Distances

• Little variation in DNA sequence between
  populations
• This would suggest that A. xanthogrammica takes
  advantage of high water flow to disperse its
  young and increase gene flow

• More variation in DNA sequence between
  populations and little variation within
  populations

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Food Acquisition
Sea Anemones are Carnivores

• Capable of some (slow) movement, but acquire most
  food from water passing over them
• Nematocysts on tentacles stun macrofaunal prey
• We might expect sea anemones to tilt crown (prey
  catching surface) towards oncoming water flow
• Receive nutrients from symbiotic zooxanthellae
  and zoochlorellae

A. xanthogrammica eating a mussel
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Summary

• Evolved wide, short body shape to reduce stress
  from high current while maximizing feeding
  potential
• Rely on oceanic current to deliver prey items,
  but contain endosymbionts for additional
  nutrients
• Require water flow for mixture and dispersal of
  gametes, possibly over long distances

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Selected Readings

• Harris, V.A. (1990) Sessile Animals of the Sea
  Shore, Chapman Hall, London.
• Kozloff, E.N. (1993) Seashore Life of the
  Northern Pacific Coast, University of Washington
  Press, Seattle and London.
• Ricketts, E.F., Calvin, J., Hedgpeth, J.W.
  (1985) Between Pacific Tides, Stanford
  University Press, Stanford, California.
• Shick, M.J. (1991) A Functional Biology of Sea
  Anemones, Chapman Hall, London.