Atelecyclus rotundatus

Abstract: 1. A study has been made of the oxygen and carbon dioxide transporting properties of the blood of three species of crab,Goneplax rhomboides, a species which constructs semi-permanent burrows in sublittoral muds, andAtelecyclus rotundatus andLiocarcinus depurator which simply bury themselves in the substratum. Investigations were also made of thein vivo blood/gas parameters in these three species. The oxygen carrying capacity of the blood was similar in all three species (0.31–0.34 μmol·ml−1) as were arterial and venous oxygen tensions. Arterial and venous blood pH values were not significantly different but inL. depurator pHa was 8.08 compared with 7.81 in the other two species. At pH 7.8 and 10°C the oxygen affinity of the blood ofA. rotundatus (P50=5.6 Torr) andG. rhomboides (P50=4.1 Torr) was higher than that ofL. depurator (P50=24.3 Torr). Oxygen affinity was relatively temperature independent between 5–15°C inA. rotundatus and inL. depurator butG. rhomboides exhibited a normal temperature dependence (ΔH=−64 kJ·mole−1). The Bohr effect was much larger inL. depurator (ϕ=−1.43) than inA. rotundatus (ϕ=−0.92) andG. rhomboides (ϕ=−0.59). 2. The haemocyanin of all three species exhibited a pronounced lactate effect i.e. an increase in blood lactate concentration increased the oxygen affinity of the haemocyanin, and inA. rotundatus it was also possible to demonstrate the existence of an unidentified factor in the blood which slightly increased the oxygen affinity of the haemocyanin. InA. rotundatus and inL. depurator, but not inG. rhomboides, an increase in blood lactate concentration caused a decrease in the cooperativity of the haemocyanin. 3. The blood ofA. rotundatus, G. rhomboides andL. depurator had a high capacitance for CO2 transport at physiological CO2 tensions and also exhibited a distinct Haldane effect, the magnitude of which differed between these species. The buffer value of the blood of these crabs was low (Δ[HCO3]/ΔpH=−4.93 to −5.99 mmol·l−1·pH unit−1). The observed differences in the oxygen and carbon dioxide transporting properties of the blood of these three species of crab are discussed in relation to their mode of life.

Abstract: The complete larval development is described of laboratory-reared Atelecyclus rotundatus and the stages are compared with larvae of other cancrideans (= corystoideans). The results suggest that the subfamily Atelecyclinae requires reappraising and that present larval evidence does not support the currently accepted grouping of families in the Cancridea.