Peter Pettigrew's Animagus form was a rat. Colloquially, a "rat" is a snitch or informant. Webster's also lists the following possible definition: "a contemptible person: such as... one who betrays or deserts friends or associates."
Given that both of those meanings describe exactly what Peter Pettigrew did (he ratted the Potters out to Voldemort, and he betrayed his friends and associates), was the author subtly alluding to his betrayal?
A lot of this sort of magic in Harry Potter is closely connected to your personality - think the Patronus, or your sorting, or your wand. Similarly, your Animagi form is related:
Q: When you turn into an Animagus, can you choose what animal you become? Or does this get "assigned" to you?
JKR: No, you can't choose. You become the animal that suits you best. Imagine the humiliation when you finally transform after years of study and find that you most closely resemble a warthog.
Also consider Rowling's (not just magic's) tendency towards this sort of allusion - Snape's flower dialogue, the names of spells, names of chracters (Remus Lupin, as often pointed out, might as well be named Wolfy McWolf, and Sirus Black = dog star black = black dog) all point toward these sorts of things being very intentional because Rowling paid attention to that kind of thing.
Look at also at his nickname: Wormtail. One of the definitions for worm is "a weak or despicable person (often used as a general term of abuse)" - also probably intentional. Look also at the personality of Pettigrew when we finally meet him, and the characters' reaction to him - Harry
[threw] Pettigrew’s hands off him in disgust
Pettigrew was begging and groveling towards Harry and Ron, e.g., in
Kind boy ... kind master [...] I was your rat ... I was a good pet...
And of course there's
If you made a better rat than a human, it’s not much to boast about, Peter.
All of this seems to indicate that yes, Peter Pettigrew's Animagi form and what he did are quite related. Interesting end link - this essay; see the last section of the essay at the very bottom titled The Rat.
