Effects of Oxygen and Isoflurane Anesthesia on Hemolymph Gas Analysis and Righting Reflex of Asian Forest (Heterometrus longimanus) and Dictator Scorpions (Pandinus dictator)
Large arachnids are commonly managed under professional care, and anesthesia is occasionally required for physical examination, diagnostic, and therapeutic procedures. Changes in acid-base balance and ventilatory status can affect immune responses in invertebrates, and previous studies found changes in tarantula hemolymph gas values when anesthetized; however, scorpions have not been investigated.1-4 This study measured hemolymph gas values using iSTAT CG4+ cartridges in healthy adult Asian forest (Heterometrus longimanus=HL, n=8) and dictator scorpions (Pandinus dictator=PD, n=12) breathing room air, 100% oxygen for 10 minutes in a chamber, and 5% isoflurane and oxygen in a chamber until induction, or loss of righting reflex (LRR). All scorpions recovered without complications and there were no cartridge failures. Analysis of hemolymph gas values in room air revealed species differences in pH, pCO2, TCO2, and HCO3. There was lower pH and higher PCO2 in oxygen in PD, increasing PO2 with each inhalant in both species, and lower base excess in oxygen in both species. HL had a significantly shorter induction time (6.5±1.9 min) than PD (12±2.1 min), but recovery time (regain of righting reflex) did not differ between species (21±13 min). Subjectively, PD exhibited rough inductions compared to HL, characterized by violent whole body and tail movements. The unexpected increase in PO2 in isoflurane compared to oxygen along with the species-specific differences and anesthetic effects emphasize the unique respiratory physiology of scorpions and further analyses of immune system responses are warranted and in progress.
The authors thank the Miller Park Zoo staff for caring for the scorpions and helping with handling during the study.
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