Practice Makes Perfect

The last couple of weeks I’ve been getting in some practice here and there, taking pictures of eggs laid by backup lab culture flies, trying to figure out how to get the best picture I possibly can for measuring egg size in ObjectJ.

The 'Old' Way

Yesterday I size sorted IV flies, and let them lay on juice cookies over night. After clearing the flies and putting the cookies in the fridge to control for any changes in egg size from development, I worked my way through taking pictures of eggs in each size group. The pictures were looking pretty good, except for the lack of contrast between the red background and the eggs (that pick up a sort of pink colour from the cookie).

The 'New' Way

 It wasn’t until the last cookie that I discovered something that would make the photos much better. Instead of using a white platform underneath the juice cookie as I had been doing previously, I tried  using a black one. This instantly increased the contrast between the eggs and the background. I believe that with this discovery, future picture taking and egg measurements will be much more effective.

Getting in this practice and working out all the little details now will be very helpful in the future when I start working on my thesis project.

Repeatability of mate choice in female red jungle fowl

Johnson, T.S. and Zuk, M. 1995. Behavioural Ecology. 7:245-246

The authors investigated the repeatability of mate choice in female red jungle fowl by examining the heritability of female preference that is an assumption in models explaining the evolution of mate choice. Male morphology was characterized 2 weeks before mate choice trials. For the mate choice trials, males were chosen randomly with the only condition that females never saw a male more than once and males were not paired more than once during the experiment. Females were placed in a small cage in front of two males and left there for 30 min. The female's behaviour was then observed for 20 mins after being released from the small cage. Preference was scored if a female copulated with a male. The results showed that female preference differed with both male trait and the timing of the breeding season. The highest estimate of repeatability was found to be 0.19, which indicates that current heritability may be low. Yet there is still evidence that a heritable component exists in the female red jungle fowl. Females showed repeatability with respect to male combs, but not with respect to hackle feather colour. Male traits can thus evolve through female choice when female preference is genetically determined. and the male trait is heritable.

Positive genetic correlation between female preference and offspring fitness

Hine, E., Lachish, S., Higgie, M., Blows, M.W. 2002. Proc. R. Soc. Lond. 269:2215-2219

These authors showed that female Drosophila serrata prefer extreme male cuticular hydrocarbon (CHs) blends and that this preference affects offspring fitness. Mate choice experiments were preformed using virgin females individually placed with two virgin males. After observed copulation, the males were removed and killed and prepared for gas chromatography analysis of the CHs. From these results, the authors estimated the sexual selection fitness function and linear selection gradient for the more attractive male CH blend. It was then determined if female choice affected offspring fitness with a quantitative genetics experiment. This experiment encompassed female preference, male attractiveness, and offspring fitness all in one. The authors found that female preference is positively correlated with offspring fitness, and that choosing the more attractive male results in genetic benefits. In addition, males with the highest probability of mating conferred intermediate levels of offspring fitness, indicating that female choice in under stabilizing natural selection. Even though male cuticular hydrocarbons experience strong sexual selection, the genes underlying this conferred lower offspring fitness, suggesting a balance between sexual selection and natural selection may have occurred in this population.

Pushing Flies

Effects of Drosophila melanogaster Female Size on male Mating Success

Turiegano, E., Monedero, I., Pita, M., Torroja, L., Canal, I. 2012. Effect of Drosophila melanogaster Female Size on Male Mating Success. J Insect Behav.  

This article examines the importance of female body size on mating success in Drosophila melanogaster. The authors first confirm that larger males do mate more rapidly and more frequently, but stress the importance of examining female size relative to males. Through observation and analysis, the authors were able to conclude that in a non-competitive environment, an increase in female size prolongs copulation latency (i.e. the time between introduction and initiation of copulation), specifically that larger differences in size between a male and a female causes an increase in copulation latency. Larger females were also found to display lengthened avoidance behaviour during courtship. In competitive environments, it was found that the first male to initiate courtship had a much higher probability of mating, and that an increase in female size reduces the likelihood of the larger male initiating courtship.  This study is significant because examines the importance of the relative size of both males and females in determining mating success, and leaves room for further research into this topic.

Effect of Drosophila melanogaster Female Size on Male Mating Success

Turiegano, E., Monedero, I., Pita, M., Torroja, L., & Canal, I. 2012. J Insect Behav.   

The authors examined the effect of female Drosophila melanogaster body size on mating success. Their results confirmed that larger males have a higher mating success. The authors also found that female size with respect to male size also affects mating success; previously the role of female size was unknown. The effect of female size on mating behaviour and dynamics appears to influence male courtship displays. Males show an increased time in courtship initiation towards larger females, larger females are the recipients of more wing vibrations, and larger females tend to avoid males for longer periods of time during courtship attempts. Large males are known to copulate more rapidly in non-competitive experiments. In addition, large males are favoured to initiate courtship in a competitive environment.The analysis of these behaviours confirms that the female is the most important in courtship opportunities and that both male and female body size is important for successful mating.

Annotated Bibliography

Turiegano E, Monedero I, Pita M, Torroja L, Canal I. 2012. Effect of Drosophila melanogaster Female Size on Male Mating Success. J Insect Behav.

This article considers the importance of female size when examining male mating success. Previous studies have revealed that larger males tend to have higher mating success, but did not take female size into account. The study confirmed that male size affects mating success, but stresses that this must always be considered relative to female size. Males show greater latency to courtship toward larger females, larger females receive more wing vibrations from males during courtship, and larger females move around more during courtship. The article discusses possible reasons for observed behaviours, and invites further study into the relation of female and male size variation toward mating behaviour.