CLARK, Z.L.; ZALISKO, E.J.; Blackburn College, Carlinville, IL; Blackburn College, Carlinville, IL: Skeletochronology of the Ringneck Snake Diadophis punctatus from western Illinois.

Ten adult (257-374mm TL) and six juvenile (128-155 mm TL) snakes were collected from western Illinois (Greene County) and fixed in 10% formalin within eight hours of collection. Tail tips of adults (10mm) and juveniles (5mm) and ribs from the snout-vent-length midpoint were removed, decalcified, embedded into paraffin, and serially cross-sectioned at 8�m. Sections were treated with PAS, Bromophenol Blue, Toluidine Blue, or Hematoxylin and Eosin. Growth layers and lines of arrested growth (LAGs) were best revealed in the regions deep and lateral to the neural spine of caudal vertebra stained with Toluidine Blue or Bromophenol Blue. The total number of LAGs in adult vertebrae ranged from 3-12. There was little correlation between snake length and the number of LAGs in adult caudal vertebrae. Growth layers and LAGs in ribs were less apparent and more difficult to interpret. Their inclusion in skeletochronological studies of this species is discouraged. All six juveniles had caudal vertebra with one LAG suggesting an age of nearly one year. Reliable estimations of the age of adult ringneck snakes may be made in the field without sacrificing the animals by sampling the distal 10mm of adult tails and examining the skeletochronology of the caudal vertebrae using Toluidine Blue or Bromophenol Blue. Adult tail samples shorter than 10mm and juvenile tail samples shorter than 5mm may be insufficient for this analysis.