Gill morphometrics of two Antarctic fish species Pleuragramma antarcticum and Notothenia gibberifrons

Abstract

Gill dimensions of 27 juvenile and adult Pleuragramma antarcticum from the southern Weddell Sea and of 28 juvenile and adult Notothenia gibberifrons from the South Orkney and South Shetland Islands were estimated. The unit gill area (UGA) of P. antarcticum ranged from 75 to 167 mm2/g (mean=105); gill area index (GAI) and water-blood distance (WBD) were found to be 1.38 cm2 and 3.3 μm, respectively. The exponent dg in the relationship total gill area to weight was found to be 0.90. It is concluded that P. antarcticum belongs to sluggish species and, although pelagic, its routine energy costs tend to be low. However, the closely packed lamellae (NL/mm=21) indicate more active behaviour in comparison with N. gibberifrons. A preliminary estimation of growth parameters (P, k) is presented. The sluggish behaviour of N. gibberifrons, as expected from its benthic mode of life, is reflected by the gill parameters: the very low UGA ranged from 39 to 118 mm2/g; GAI and dg were found to be 0.73 cm2 and 0.98, respectively. Comparing gill dimensions and general respiration characteristics of fish from antarctic, temperate and tropical waters it is concluded that antarctic fish have increased their scope for activity.