That is the parietal eye aka the "3rd eye" they use that to help them notice when predictors are above them since they can't see up..... I might be wrong on that but I think thats what it is for
It is essentially a photosensory organ on the top of their skull. They use it to aid in thermo-regulation, light sensing, and it helps them disern possible threats from the sky
I just set Swordtail's timer for his bath and paused it so I could actually fill his soaking bowl up and he crawled over my phone and canceled the timer
Mirage came out of brumation on April 26. He was doing great. On May 2 he started acting funny. We just redid his tank, and he keeps going into one of his hides. He just lays there. He shows no intrest in food. HELP!