Symbioses

[Vitto]

Of note is that photosynthesis has been found in quite a wide range of animals, like sea slugs, salamanders, hornets and aphids: https://umich.uloop.com/news/view.php/77...ic-animals. So it seems that at least a salamander-like metabolism is possible with photosynthesis (though I'm not sure how much energy these salamanders get from photosynthesis).

The interesting one here is the photosynthetic sea slug, as the article correctly say it harvest chloroplast eating algae. The part on the horizontal gene transfer is important but not well explained: what make this seal slug stand out from the rest is the fact that it is capable to integrate and mantain the chloroplast in its body for a very long time and this is possible only due to the transfer of genes that are responsable for the chloroplast manteinance.
As wrote, horizontal gene transfer is the exception among animals (preservation of your own genetic code) but much more common in bacterias (at times, usually when food is not abundant, some bacteria actively scavenge DNA from their surronding to "fish" new metabolic pathways).
What the slug pass to the offspring are the genes for the chloroplast manteinance, not the chloroplast themselves.


The slug can indeed survive months only on the chloroplast action... but it is a slug: flat, with a very large surface area compared to the body.
Also, slug are not that active metabolically, they don't have to mantain a certain body temperature and you have to factor that in water you don't have to support your body against gravity.

The sea slug is the only know animal, IIRC, that get a significant part of its energy intake from photosyntesis.