Your animal companion’s bite attack deals an additional 1d4 points of acid damage, and the acid deals another 1d4 points of acid damage to the target on the next round. The acid continues to deal damage for 1 additional round per 4 caster levels (to a maximum of 6 total rounds at caster level 20th). This ongoing acid damage doesn’t stack from multiple attacks, but the duration resets if a newer bite would cause the ongoing damage to last longer than the duration remaining from a previous one. The acid does not harm the animal companion.