Respiration of Lampreys

In lampreys, though the gross morphology of the branchial chamber and the method of ventilating the gills are radically different from that found in gnathostomes, the total gill area of larval (1462–2717 mm2∙g−1) and adult (1402–2337 mm2∙g−1) lampreys, the ultrastructure of the gills, and the thickness of the water–blood barrier are similar to active teleosts. The standard rates of oxygen consumption of ammocoetes are low, values for medium-sized Ichthyomyzon hubbsi ranging from 18.1 μL∙g−1∙h−1 at 3.5 °C to 90.1 μL∙g−1∙h−1 at 22.5 °C. The consumption rates increase during metamorphosis rising in Lampetra fluviatilis held at 10 °C from 29.3 to 60.4 μL∙g−1∙h−1, and at the same time a circadian rhythm of consumption develops; maximum rates occur in the dark. Adult lampreys have consumption rates ranging from 66.1 μL∙g−1∙h−1 in L. fluviatilis to 36.9 μL∙g−1∙h−1 in Petromyzon marinus, and Q10's in the temperature range 5–15 °C are from 1.6 to 4.83. Sexually mature males of L. planeri and L. fluviatilis have higher metabolic rates than the females. The active oxygen consumption of P. marinus at 332.5 μL∙g−1∙h−1 is within the range reported for teleosts. Resting ventilation rates are higher in adults than ammocoetes and reach maximum values in sexually mature spawning males. Hypoxia results in an increase in the ventilation and heart rates.Key words: lampreys, respiration; gills, morphology; oxygen consumption, sexual maturity, ventilation rates