Daphnia longicephala is a freshwater crustacean that can detect chemical cues produced by the predator Notonecta glauca. Researchers raised Daphnia clones and observed that those exposed to Notonecta chemical cues during their development produced larger protective crests, as described in Figures 1 and 2. Crest height and width are measured as ratios to body length. The increase in the size of the crest width and height is not associated with a corresponding change to the Daphnia’s genome. Researchers hypothesize that growing a crest is energetically costly, so Daphnia do not develop the large crests in the absence of Notonecta.

QUESTION: As a follow‑up experiment, researchers placed the Daphnia that were exposed to the Notonecta chemical cues into a tank without chemical cues. The Daphnia reproduced asexually, and the offspring developed in the tank without chemical cues. Predict the relative size of the crest height and width of offspring raised in the tank without chemical cues as compared to the parent Daphnia and justify.

⇒Whenever there’s a presence of Notonecta chemical cues there will be a change of epigenetic in the Daphnia genome due to which we are expected to observe differential gene expression in Daphnia in the presence of Notonecta chemical cues. This particular differential gene expression will overtime result to the development of higher and wider/larger crests.

⇒The comparative volume of the crest height and offspring width that was raised in tank without chemical cues is expected to be smaller as compared to the parent Daphnia.

⇒ A wider and higher crests are the outcome of the changes in epigenetic which are triggered by the presence of chemical cues. Since there will be no presence of these cues in the tank, these epigenetic changes will not be seen in offsprings as a result of the fact that there will be normal gene expression producing normal crest height and width.

topeadeniran2 topeadeniran2 · Answer 2 · 2022-01-24T14:42:50+01:00

It should be noted that whenever there’s a presence of Notonecta chemical cues there will be a change of epigenetic in the Daphnia genome.

Also, it can be deduced that the comparative volume of the crest height and offspring width that was raised in tank without chemical cues is expected to be smaller when it's compared to the parent Daphnia.

Lastly, there will be a wider and higher crests which are simply the outcome of the changes in epigenetic that are triggered by the presence of chemical cues.

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