A lot of reptiles, fishes and insects are in vivariums that already provide a good light source. For wild animals, you are fine without a light since they are mostly outdoor and unless you're planning for it chances are that you'll stumble on them during daylight.
Personally, I have a lot of ring lights because beauty and makeup brands give them for free with a lot of products.
But even without all of this, you can get great footage and photos.
Take a look at this spider that was walking around my sink for example.
The phone (pixel 3, already quite aged) did not have a lot of trouble to focus on it even if we are talking about a small spider that is only a few milimiter in size.
It's a video so focus comes and goes but the parts where the focus is set on the spider are quite clear (ignoring the upload compression).
I am no artist and was focusing more on the spider's behavior. Someone who is an artist could have snapped great macros at that moment.
https://photos.app.goo.gl/z2RALoGeXiAo6uHG6
Another example is this queen ant when it was in it's founding stage. The nanitics (first workers) are small even when it comes to ant scale. You can see them in great details and can even see the translucent parts of their gaster with the sugar water inside.
Again, I focused on the behavior more than the art. But an artist could have taken a photo instead of a video with great results.
https://photos.app.goo.gl/dmzMXLqG5v1cfFKx9
Both of those were candid moments that I happened to snap because I had my phone in my pocket while my 4k camera and my canon reflex were in their box in my desk.