Effects of Short- and Long-Term Hypoxia on Hemolymph Gas Values in the American Horseshoe Crab (Limulus polyphemus)
American Association of Zoo Veterinarians Conference 2008
Matthew C. Allender1, DVM, MS; Juergen Schumacher1, Dr. med. vet., DACZM; Robert George2, DVM; Jennifer Milam2, BS; Agricola Odoi3, BVM, MSc, PhD
1Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN, USA; 2Ripley’s Entertainment, Ripley’s Aquarium of the Smokies, Gatlinburg, TN, USA; 3Department of Comparative Medicine, College of Veterinary Medicine, University of Tennessee, Knoxville, TN, USA
In order to evaluate the effect of short- and long-term hypoxia in the American horseshoe crab (Limulus polyphemus), 22 adult, healthy crabs were evaluated for this study. In group 1, baseline pH, PO2, PCO2, HCO3, base excess, TCO2 and lactate concentrations were determined from hemolymph samples collected from 10 horseshoe crabs submerged in water. Baseline results were compared to values obtained following removal from water for 5 minutes and following recovery in water for 10 and for greater than 60 min (range: 61–221 minutes). In group 2, hemolymph gas parameters were determined in 12 horseshoe crabs following shipment out of water for 24 h and compared to values obtained from group 1 animals. Following removal from water for 5 minutes, all crabs developed severe hypoxia with PO2 levels below the detectable limit of the analyzer. No significant changes in PCO2 concentrations were seen over time in group 1 animals. Group 2 crabs had pronounced respiratory acidosis (pH=6.7; PCO2=46 mm Hg) following transport, and PO2 concentrations were significantly below baseline values of group 1 animals. Baseline hemolymph gas values of the American horseshoe crab were within range reported for other aquatic vertebrates. Short-term removal of crabs from their aquatic environment causes severe hypoxia and metabolic changes. While crabs have the ability to compensate for a changing hypoxic environment if removed from water for long periods of time (24 h) severe hypercapnia and respiratory acidosis will still be present.