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Transcript of Polyandry and tibial spur chewing in the Carolina ground cricket, Eunemobius carolinus Piascik, EK....
![Page 1: Polyandry and tibial spur chewing in the Carolina ground cricket, Eunemobius carolinus Piascik, EK. Judge, KA. Gwynne,](https://reader035.fdocuments.in/reader035/viewer/2022062803/56649cb15503460f94976c90/html5/thumbnails/1.jpg)
Polyandry and tibial spur chewing in the
Carolina ground cricket, Eunemobius carolinus
http://www.ojibway.ca/orthoptera.htm
Piascik, EK. Judge, KA. Gwynne, DT. (Can J Zool) 2010
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Nuptial Gifts in Various Insects
Spermatophylax Male body partsInsect prey
•Male material donations transferred to the female during or directly after copulation
http://www.livescience.com/imageoftheday/siod_050214.htmlPhoto by Gwynne DT
http://farm1.static.flickr.com/62/175348691_7df74ddb73.jpg?v=0
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Do nuptial gifts provide direct benefits or are they
manipulative devices?
A. Males provide females with direct
benefitsIncrease in female fitness with increased number of matings
Example:Nutritional and hydration benefits
B. Males manipulate females
Decrease in female fitness with increased number of matings
Example:Allohormones in male secretions reduce female receptivity to subsequent matings
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• Occurs when the two sexes have conflicting optimal fitness strategies
• Males mate multiply to increase fertilization success
• Females mate less to avoid costs
Sexual Conflict
http://www.ijmphotography.co.uk/Images/Wildlife-And-Nature/Large/IJM_DamselMating.jpg
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Polyandry and Sexual Conflict
• Females will mate with a variety of males, exceeding the mating rate necessary to produce all her offspring
Why are females mating with several males?
• Can nuptial gifts benefit the female and overcome these costs?
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Nutritious gifts
• Nuptial gifts may be providing the female with nutrients
• Increase the fitness of the male’s own offspring
• Increase the fitness of the female
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The Coercion Hypothesis
• Gifts manipulate the female’s mating rate
Sakaluk et al. 2006
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Material Benefits Hypothesis
• Resource-deprived females are predicted to:
• mating rate
• copulation duration
• gift consumption
• latency to copulate
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Katydids increase their refractory period
Simmons and Gwynne 1991
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Seed beetles increase their mating frequency
Ursprung et al. 2009
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Nursery web spiders accept more copulations
Prokop and Maxwell 2009
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Fedorka and Mousseau 2002
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Mays 1971
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Female southern ground crickets gain material benefits from multiple matings
(Fedorka and Mousseau 2002)
Female striped ground crickets copulate longer when chewing on tibial spurs
(Bidochka and Snedden 1985)
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Carolina ground cricket, Eunemobius carolinus
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Testing the Material Benefits Hypothesis
• Manipulate the nutritional content in female diet
• Prediction: If females are nutritionally deprived, then they will
1) increase their mating rate,2) copulate sooner,3) copulate longer and 4) chew longer
***This study would provide useful information on the basic mating behaviour of E. Carolinus
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Study animals
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Female diet manipulation
• Females were placed in one of two diet treatments (upon adult eclosion) varying in nutritional content
• Low-diet: 67% rabbit chow, 33% cellulose
• High-diet: 99% rabbit chow, 1% cellulose
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Mating trials
Each female was given an opportunity to mate with one male once a day for four
consecutive days
90 minutes
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Mating trials
Males
Day 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
1 H H H H H H H H L L L L L L L L
2 H H H H L L L L H H H H L L L L
3 H H L L H H L L H H L L H H L L
4 H L H L H L H L H L H L H L H L
Male A: H L H L
Male B: L L L H
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Fecundity and lifespan
Ovipositor
Eggs
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Fecundity and lifespan
• Total egg count = total # eggs from gauze over lifetime
• Egg-laying rate = total egg count / lifespan (days)
Survival was monitored dailyFood and water were replaced weekly
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Trend for females on the low-quality diet to copulate sooner
than those on the high-quality diet
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No significant effects of diet treatment on any of the mating
variables
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Females of this species may not receive direct benefits from
multiple matings
• Females fed a low-quality diet did not mate more often or sooner than females fed a high-quality diet
• When they did mate, they did not copulate or feed for longer
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No difference in female mass before first mating opportunity
p=0.361
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Females fed low-quality diet lived significantly longer
High-quality diet = solid line, n=22Low-quality diet = broken line, n=21
p=0.045
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Nutrient restriction was insufficient to limit the material
benefit• The diet DID have an effect on the females
• Females fed on low quality diets lived longer which indicates food stress because dietary restriction is known to extend the lifespan of animals (Partridge et al. 2005)
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Correlations among mating behaviours and male lifespan
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Spur chewing may be costly to males
• Males may be taking longer breaks from mating as they recoup lost energy reserve
• Sagebrush crickets are less likely to re-mate as a result of female wing-feeding (Sakaluk et al. 2004)
• Future work could examine condition dependence of male haemolymph gifts, also effects on male immune function and life span
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Males may be coercing females
• Male control over insemination• Spermatophore attachment
• Chemicals in the ingested hemolymph that function as a chemical signal to increase male fitness
• Field crickets exposed to courtship had shorter lifespans (Bateman et al. 2006)
• BUT E. carolinus that mated are actually living longer and laid more eggs than those that failed to mate.
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Mating behaviour
• 1971: Mays described the mating behaviour of E. carolinus based on 2 pairings
• Current study: describes mating encounters based on 70 complete mating sequences
• We now have a comprehensive description of courtship and copulation of this previously un-described gift-giving species
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Older females were more likely to mate than younger females
Diameter of data points is related to the number of observations with that combination of values
Smallest=1 Largest=6
p=0.024
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Further insight into the role of spur chewing during mating in E.
carolinus• Effects on both female and male fitness
• Our results do suggest that spur chewing may be costly for males
• Male mass loss correlated with both copulation and spur chewing in this cricket species
• Further studies should examine the relationship of both the gift size and the gift`s chemical composition to female fitness
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Acknowledgements
Dr. Darryl GwynneDr. Kevin Judge
Dr. G.K. Morris
The Gwynne Lab:Laura Robson
Kyla Ercit
http://www.pbase.com/tmurray74/image/89343329