Transcript Comparison of Evolutionary Intra-Sexual Selection on Sperm in

Intra-Sexual Selection on Sperm in Selfing (Caenorhabditis elegans)
and Out-Crossing (C. remanei) Mating Systems
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Janice M. Hodges , Katja Kasimatis , Patrick C. Phillips
of Mississippi,
2Institute
of Ecology and Evolution, University of Oregon
The importance of studying sperm in
intra-sexual selection.
• Sexual reproduction, specifically fertilization, is a powerful organizing principle in biology, but its
shaping processes are not well studied.
Microfluidics
• Although pre-copulatory sexual selection has been extensively studied, little is known about postcopulatory interactions between the sperm of different males and also between sperm and the
female reproductive tract.
Figure 1 Evidence that in the first three days of adulthood C. remanei steadily increases while C. elegans
staggers after Day 2.
• Understanding the basis of sperm competition will lead to a better understanding of sperm’s role
in intra-sexual selection and it’s influence in evolving the fertilization process.
Research Questions
Size (mm)
Correlations Between Testis & Sperm
Size
Size (mm)
1University
Day 1 C. Elegans
R=0.59
Day 2 C. Elegans
R=0.46
Day 3 C. Elegans
R=0.70
Day 1 C. Remanei
R=0.89
Sizing v1.1 (N. Timmermeyer)
Microfluidic Sizing Chip is to size the sperm, testis, and the full body of the worm and allow the
fine manipulation of the worms as they are pushed through the channels.
Day 1 C. Remanei
R=0.68
Day 2 C. Remanei
R=0.90
• Does sperm size correlate with testis size as predicted by sperm expenditure theory?
• How long can an activated spermatid live when not given any inputs? Does sperm longevity
correlate with sperm size?
Experimental Design
Model System
Figure 2 The three graphs demonstrate that in the first three days of adulthood there is a positive correlation
between testis size and worm size.
I) Correlation Between Testis & Sperm Size
a) Sizing Testis & Worm Size
i. Hatch-off – creates age-synced worms
Importance as model systems:
• Significant evolutionary diversity
• Short generational period
Figure 3 (left) This graph describes a trend that exists
between testis and sperm size of C. elegans.
ii. Pick male worms into sizing chip to size both the worm testis and size
• Hermaphroditic and Gonochoristic
species
b) Ejaculation Assay – Sizing sperm cells in a microfluidic chip
i. Hatch-off – creates age-synced worms
Reproductive Process
Vulva pit
Spicule
Sperm Longevity
Figure 4.1 (left) A qualitative representation of inactivated sperm longevity. Figure 4.2 (right) A qualitative
representation of activated sperm longevity.
n = 60
ii. Isolate male worms to ensure they are true virgins. Place the worms in a chip and
wait for spontaneous ejaculations.
Conclusion
II) Sperm Longevity
• Evident positive correlation between worm size and testis size.
• Preliminary observations demonstrate a possible trend between the testis and
sperm size.
• In both activated and inactivated sperm cell experiments, C. elegans sperm cells
outlasted C. remanei.
a) Sperm Extraction/ Storage
• The male will insert it’s spicule into the vulva of the hermaphrodite/female.
• This triggers the sperm to then flow from the testis into the female. (ejaculation)
• Once the inactivated sperm enter the female, the cells are then activated.
b) Activation
Acknowledgments
TEA
Thank you to my PI Patrick Phillips and my mentor Katja Kasimatis for making this lab experience
amazing, Peter O’Day and Marilyn Drennan for making the program worth wild, my fellow
cohorts for their love and friendship, and my beautiful parents for everything.
Future Directions
After observing that inactivated sperm cells can remain intact for more than 12 hours, will
that sperm be able to be activated after the given time period?
If sperm size and longevity correlate, are sperm cells provisioning more lipids or more
proteins?
NIH : P50GMO989911