Aerial and Aquatic Respiration in the River Crab Potamonautes Warreni Calman with Notes on Gill Structure

Abstract

The oxygen consumption rate (ṀO₂) for Potamonauteus warreni Calman (= Potamon warreni (Calman) kept in 25 °C water was 34,4 μmol 1⁻¹ O₂ kg⁻¹ and after 72 hours in 98% R.H. air the rate was 31,9 μmol 1⁻¹ O₂ kg⁻¹ min⁻¹. The ṀO₂ values for each of the two groups are not significantly different (P > 0,05). The partial oxygen tension of pre-branchial (v = venous) haemolymph (P_vCO₂) is 15,3 mm Hg in water and 13,0 mm Hg in air); partial carbon dioxide tension of pre-branchial (v) haemolymph (P_vCO₂) is 13,2 mm Hg in water and 13,0 mm Hg in air); the total carbon dioxide concentration in pre-branchial (v) haemolymph (C_vCO₂) tot. is 12,3 mmol 1⁻¹ in air and 13,9 mmol 1⁻¹ in water) are not significantly different for the two groups (P > 0,05). The haemolymph pH and the lactate concentration for crabs in water was found to be 7,51 and 0,38 mmol 1⁻¹ respectively. No significant differences were found in pre-branchial haemolymph oxygen tension, carbon dioxide tension, total carbon dioxide content, haemolymph pH, lactate level, chloride concentration, P₅₀ and haemocyanin-oxygen cooperativity in control crabs kept in water, and experimental crabs held in air for 72 hours. The chloride concentration, (327,0 mmol 1⁻¹) for crabs kept in water does not differ from that of crabs held in air for 72 hours but is at least 15% higher than the sodium concentration (255 mmol 1⁻¹) for crabs kept in water. The gill surface area is 520 mm² g⁻¹ wet body mass; on average 9,2 gill platelets (lamellae) can be found on a gill length of one millimetre. Each lamella is spaced 60–70 μm apart, each with a thickness of 30–40 μm. It is concluded that P. warreni may be described as a truly amphibious fresh-water crab.