ABSTRACT

1
Nurse eggs and cannibalism influence
intracapsular development and survival in a
poecilogonous spionid polychaete
OBJECTIVE
This study examines interactions between
adelphophagic and planktotrophic larvae and
nurse egg in capsules specifically measures
cannibalism and larval growth rate
FERNANDA X. OYARZUN Department of Biology,
University of Washington.
ABSTRACT Poecilogony is the ability to alternate
between multiple developmental modes. Boccardia
proboscidea, a spionid polychaete, has three
different types of developmental strategies,
including one in which capsules have
approximately 90 nurse eggs and a mixture of
planktotrophic and adelphophagic larvae. In this
study I evaluated whether larval development was
influenced by the conditions in which larvae
develop inside the capsule, by manipulating
combinations of larval types and nurse egg
concentrations in vitro. Both larval types ate
nurse eggs inside the capsule and when they were
removed from capsules, showing an active feeding
behavior from early stages. Both larval types
grew more at higher concentrations of nurse eggs,
but adelphophagic larvae grew faster.
Planktotrophic larvae continued developing inside
the capsule and ate nurse eggs, contrary to
predictions from previous studies. I found no
significant effect of larval combination on
growth rate for either of the two developmental
modes, however mortality of planktotrophic larvae
was high due to cannibalism, implying that there
are big disadvantages for planktotrophic larvae
inside capsules that contain adelphophagic
siblings. Mothers capsule-opening behavior is
hypothesized as a mechanism to regulate survival
of different developmental types in nature.
METHODS RESULTS
II. Capsule Manipulation Experiment
I. Nurse-egg Manipulation Experiment

• Methods
• Two factors were used to test the effect of the
  environment in each larval type
• Encapsulation
• encapsulated larvae
• free larvae
• Combination of larvae
• 2 adelphophagic AA
• 2 planktotrophic PP
• 1 planktotrophic and 1 adelphophagic AP
• untouched capsules U
• open/close capsules C

Methods

• Two factors were used to test the effect of nurse
  eggs
• Number of nurse eggs 0, 20 and 40
• Larval type adelphophagic A and planktotrophic
  P

STUDY SYSTEM
Manipulated capsule (start)
Results
Results
Manipulated capsule (end)
Some population of B. proboscidea (Polychaeta
Spionidae deposit capsules with 90 of nurse
eggs and planktotrophic (p) and adelphophagic (a)
larvae (Gibson..).
Nurse eggs
Presence of sibling larvae does not influence
developmental mode or growth rate, but there are
high levels of cannibalism of planktrophic larvae
(71).
Growth is faster with more nurse eggs
Planktrophic larvae eat nurse eggs too
Experimentally opened capsules does not affect
the results
Adelphophagic larvae have a faster growth rate
FUTURE ON-GOING RESEARCH

• ACKNOWLEGMENTS
• Richard Strathmann,
• Danny Grunbaum, Bruno Pernet, Jennifer Ruesink,
  Billie Swalla, Martha Groom, Federico Brown, Alex
  Primus, Eric Edsinger-Gonzales, Paul Bourdeau,
• Caroline Faria,
• Larval Ecology Class,
• Friday Harbor Laboratories

CONCLUSIONS
Hatching time

• Planktotrophic larvae
• Eat nurse eggs!
• Most of them continue developing inside the
  capsule
• Although growth rates do not seem to be affected
  by the presence of nurse-egg feeding larvae, they
  suffer of high levels of cannibalism

1. Test interactions at earlier stages
2. Variation in timing of mother opening of capsules
   and stages and number at hatching
3. Consequence in population dynamics (model)

• Adelphophagic larvae
• Have an active feeding behavior, and do not need
  pressure inside the capsule to eat.
• Eat plankton-feeding larvae
• Grow faster at higher nurse egg concentrations