Normoxic and hypoxic breathing pattern in newborn grey seals

Abstract

We studied the breathing patterns of three newborn grey seals (Halichoerus grypus) at 2 – 3 days of age under normoxic and hypoxic conditions with the barometric technique, which does not require the animal to be restrained. Normoxic tidal volume was deeper and breathing rate slower than expected for newborns of this size on the basis of previously published allometric relationships. In addition, two characteristics were readily apparent: (i) occasional sudden long apneas, often exceeding 30 s in duration, and (ii) consistent brief interruptions of expiratory flow. Neither aspect is common in terrestrial newborns of this age, but both have been previously observed in adult seals. During hypoxia (10 min of 15% O2 and 10 min of 10% O2), ventilation increased markedly and steadily, at variance with what occurs in newborns of other species, indicating a precocial development of the regulation of breathing. This latter result also suggests that the blunted response to hypoxia previously reported in adult seals may be acquired postnatally with diving experience.