Utilizing Coelomic Length to Determine Gender in Heloderma Suspectum

Driggers, Todd Avian and Exotic Animal Clinic of Arizona Mesa, Arizona USA todddriggers@mac.com

Sex determination of individuals of the Helodermatidae (Heloderma spp.) has proven to be a challenge. The goal of this study was to provide a tool for herpetoculturalists and field studies. Morphological and behavioral characteristics utilized in past studies failed to give objective and accurate tools for antemortum sex determination. Tail length, snout-vent length, head length and width have proven unreliable. While DNA sexing also exists in two squamates it has not been developed for this species. Here, 18 morphologically normal, mixed-origin Heloderma suspectum had coelomic and total length data collected systematically while anesthetized with propofol at 10 mg/kg IV and butorphanol at 1 mg/kg IM for pain. Surgical sexing was performed and compared to the length measurements to determine correlation. There was a positive correlation between longer coelomic length and those surgically identified as female. Adult females on average had coelomic to body length ratios that were on average between 43-44% and males between 39.5-41.5%. Juveniles were less differentiated. More variability in measurement existed in smaller juvenile specimens making the sex determination less accurate. In a clinical setting, radiographic measurements from thoracic vertebrae to the caudal pelvis would take the variability of soft tissues and angles out of the measurement and may increase the accuracy. While further studies may be necessary to increase the certainty of this study, coelomic length to body length ratio could be used as another tool to increase the certainty of accurate field sex determination and may be most accurate to differentiate adult females.