# The reproductive cost of Drosophila melanogaster : effects on cold tolerance

Romane Gout, Hervé Colinet

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## To cite this version:

Romane Gout, Hervé Colinet. The reproductive cost of Drosophila melanogaster: effects on cold tolerance. ISEPEP9 2022, Jul 2022, Rennes, France. . hal-03991236

HAL Id: hal-03991236

https://hal.science/hal-03991236

Submitted on 15 Feb 2023

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ECOBIO
Rennes

# The reproductive cost of *Drosophila melanogaster* : effects on cold tolerance

Romane Gout¹, Hervé Colinet¹

¹ Université de Rennes 1, France, UMR ECOBIO CNRS 6553 - CNRS : 6553 France

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## Drosophila's winter strategy

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In order to survive, species often make trade-offs between reproduction and survival, often resulting in reduced reproduction. During the cold and stressful winter months *Drosophila melanogaster*, like a lot of freeze avoidant insects, enters a reproductive dormancy. There could be a trade-off between reproductive activity and cold stress tolerance.

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The responses to overwintering by oogenesis stop suggests a cost of reproduction and/or an increased cold tolerance by reduced reproductive activity in *Drosophila melanogaster*.

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We compared fecundity and cold tolerance of gravid *versus* virgin females. We then attempted to artificially stop oviposition by pharmacological treatments : Rapamycin and Phloroglucinol. Our hypothesis was that virgin flies and chemical treated flies will lay respectively less or no eggs and this would affect cold tolerance.

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## Fecundity

1. We put either one female (virgin/mated) or a pair of females (chemical treatments) in falcon tubes

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2. Every 24h for 7 days we changed the charcoal medium filled caps and counted the eggs

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## Cold tolerance

### 1. Chill-Coma Recovery Time

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50 flies in ice slurry (0°C) for 3h

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25°C room for 1h, register the time to recover from chill coma

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2. Critical Thermal Minimum

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We put about 120 flies in a refrigerating column set with a ramping rate of -0.5°C/min.

When flies enter chill coma they fell off the column and the temperature was individually registered

## Take home message

* Virginity did quantitatively reduced egg oviposition, but it did not confer an advantage in cold thermal stress.

* Phloroglucinol completely stopped oviposition which conferred an advantage in cold thermal stress

* Phloroglucinol is considered a polyol, and thus might have some cryoprotective properties which are currently unknown

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## Results : fecundity

*We only show data for the phloroglucinol set as rapamycin showed no significant result*

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* Generally, mated flies laid more eggs than virgins

* The flies' temporal oviposition profile differs, there's a delay in peak egg laying activity for mated females compared to virgin ones

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* Control flies laid eggs normally

* Phloroglucinol treated flies gradually stopped laying eggs after the second day

## Results : cold tolerance

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* No difference in cold tolerance assays between Virgin versus Mated

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* Phloroglucinol-treated flies had better cold tolerance than control ones in both assays