Energy availability predicts some gastropod reproductive strategies. The study analyzed data on 189 gastropod families to examine relationships between energy availability, larval development strategies, and hermaphroditism. Results showed that planktotrophic larvae were more common at lower productivity, supporting Thorson's hypothesis. However, hermaphroditism decreased rather than increased with lower energy availability, contrary to predictions. Accounting for taxonomy, the relationship with hermaphroditism disappeared. Overall, energy constraints seem to select for adaptations conserving energy or bet-hedging in patchy environments.

1. Does Energy Availability Predict
Gastropod Reproductive Strategies?
Craig R.McClain
National Evolutionary Synthesis Center, Duke University
McClain et al. Proceedings of the Royal Society B, in press
Two female bubble-rafting violet snails,
Janthina exigua. Egg capsules are
attached to the underside of the floats.

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3. Liferequiresenergy
Veined Octopus (Amphioctopus marginatus) eating a crab

4. Threedistinct
types of energy !
affect biological
systems
1. solar radiation in the form of
photons!
2.thermal kinetic energy as
indexed by temperature!
3.chemical potential energy
stored in reduced carbon
compounds
Clarke & Gaston (2006) Proc Roy Soc B

5. Planktotrophic: feed in the plankton
during their larval stage and are
considered to have longer dispersal
potential
Lecithotrophic: larvae derive
nourishment from yolk and are non-
feeding and are considered to have
longer dispersal potential
Direct: young develop directly into the
adult form without a larval phase and
typically have limited dispersal
potential

6. Thermal kinetic energy and chemical potential energy
are posited to influence reproductive strategies
Low
Temp
Food
%PlanktonicLarvae
slow larval growth
long larval duration
fast larval growth
short larval duration
Predation
High
Temp
Food
Thorson

7. Thermal kinetic energy and chemical potential energy
are posited to influence reproductive strategies
Low
Food
%PlanktonicLarvae
planktonic larvae cheap
minimize larval/adult competition
dispersal phases allow for bet hedging
direct development expensive
retention of larvae favored
High
Food

8. Hermaphroditic nudibranchs,
Siphopteron sp. nov., from the
Great Barrier Reef !
!
R. Lange, J. Werminghausen and N. Anthes. Cephalo-traumatic secretion transfer in a hermaphrodite sea slug. Proceedings of the Royal
Society B. Published online November 13, 2013. doi: 10.1098/rspb.2013.2424.!
!
J.M. Koene et al. A syringe-like love dart injects male accessory gland products in a tropical hermaphrodite. PLOS ONE. Vol. 8, July 2013,
p.e69968. doi:10.1371/journal.pone.00e69968

9. Thermal kinetic energy and chemical potential energy
are posited to influence reproductive strategies
Low
Food
%Hermaphroditism
density low
mate availability low
density high
mate availability high
High
Food
Abundance

10. For 189 !
gastropod families !
collected data on!
!
larval development !
(dispersing v. not)!
!
& hermaphroditism !
(present v. absent)

11. Analyses
• Binary and binomial regression models were implemented in R using the package
MCMCglmm
• uninformative priors and uniformly low levels of belief
• Model chains were run for 500,000 iterations with a burn-in of 200,000 iterations and
thinning intervals of 100 iterations.
• To evaluate convergence, we assessed the mixing of Markov chain Monte Carlo (MCMC)
chains
• Chemical energy available to the gastropods was estimated as particulate organic carbon
(POC) flux (g of C m−2 year−1) based on the Lutz et al. (2007) model.
• Temperature data was gathered from the NODC database (Locarnini et al. 2010).
• For each family, we quantified the median and standard deviation of carbon flux and
temperature over their known latitudinal and depth ranges.
• Taxonomic Order—from the most current taxonomy for Gastropoda (Bouchet & Rocroi 2005)
—was included as a random effect to account for the possible effects of shared phylogenetic
history in our model. A more explicit estimation of phylogenetic covariance was not possible
due to the current lack of a comprehensive molecular phylogeny for this clade.

12. sqrt (Median Carbon Flux)
ProbabilityofOccurrence
Mixed
Direct
Lecithotrophic
Planktotrophic
50 150 2500.00.51.0
the odds of having planktotrophic
larvae versus direct development
decreasing by 1% with every one-
unit increase in the square root of
carbon flux
Opposite of that predicted by
Thorson

13. 50 150 2500.00.51.0
sqrt (Median Carbon Flux)
ProbabilityofOccurrence
Hermaphroditic
Non-Hermaphroditic
Result opposite of prediction!
!
Relationship disappears when
accounting for taxonomic
relatedness.

14. 0.0 0.5 1.0 1.5 2.0
Caenogastropoda
Cocculiniformia
Eupulmonata
Heterobranchia
Neritimorpha
Patellogastropoda
Vetigastropoda
Log Median POC flux
(g of C m-2 year-1)
Distribution
Basal metabolic rates of
nudibranchs are highest
among gastropods.!
!
Metabolically expensive to
be a simultaneous
hermaphrodite

15. Planktotrophic larvae increases!
Direct development decreases!
with decreasing productivity. !
Thus, low energy availability is selecting for adaptations for energy conservation or
bet heeding in a patchy environment.!
!
The result for hermaphroditism is opposite of prediction, !
decreases not increases with decreasing energy availability !
and likely related to shifts in metabolic demand not life reproductive strategy
Does Energy Availability Predict
Gastropod Reproductive Strategies?

16. Acknowledgments
Coauthors: Ryan Filler (Duke
University) and Josh Auld (West
Chester University)
!
Statistical Guidance: Carlos
Botero (NC State University)
!
Funding: National Evolutionary
Synthesis Center (NSF Grant
#EF-0905606)
National Evolutionary Synthesis Center