Meeting Abstract

P2.78  Thursday, Jan. 5  Respiratory Rates of BC-Floater Axolotls in Normoxic and Hypoxic Conditions ZALISKO, Edward J.*; ERTON, Timothy S.; FORBES, Scott T.; FEARN, Richard L.; Blackburn College; Blackburn College; Blackburn College; Blackburn College ezali@blackburn.edu

At the 2009 SICB meetings, our laboratory first reported a new, non-lethal axolotl phenotype based upon three generations of captive-bred axolotls (Ambystoma mexicanum). The new phenotype, named BC-Floater, results in the sustained inflation of the lungs for weeks to many months. Animals expressing this phenotype float inverted or list for two or more consecutive weeks, with trunks breaking the water’s surface. BC-Floaters inhale but rarely exhale, apparently exchanging gases primarily through long gills. The present investigation tested inhalation rates of BC-Floaters in normoxic and hypoxic conditions. BC-Floaters (F; N = 22), Recovered BC-Floaters which once expressed the BC-Floater trait but have recovered on their own to normal body postures (RF; N = 11), and Non-Floaters (NF; N = 19) were individually tested for 30 minutes in three aquatic conditions with varying oxygen concentrations: still water (4.0 mg/L), aerated water (6.4 mg/L), and hypoxic water (1.1 mg/L) created by bubbling nitrogen. In still water, inhalation rates for NF and RF were identical (1.6 breaths/30 min) and were 593% more frequent than rates for F (0.27 breaths/30 min). In aerated water, inhalation rates were similar to still water (NF = 1.2, RF = 1.6, F = 0.18). However, compared to the aerated conditions, breathing rates in hypoxic conditions greatly increased in all groups (NF = 500%, 6.0 breaths/30 min; RF = 563%, 9.0 breaths/30 min; F = 889%, 1.6 breaths/30 min). These data indicate that 1) RF appear to have returned to normal respiratory rates similar to NF, 2) F breathe at statistically significant lower rates than NF or RF (alpha = 0.05), and 3) F increase their respiratory rates greatly in hypoxic conditions to rates comparable to F and RF in aerated water (with 582% greater oxygen levels).