Some Haemolymph Biophysical Parameters in the Giant African Land Snail Archachatina marginata During a Six-Week Aestivation Period

Two experiments were conducted to determine changes in some biophysical parameters of the haemolymph in two liveweight groups of the Giant African Land Snail Archachatina marginata during and after aestivation. Experiment 1 was carried out on haemolymph biophysical changes during aestivation, while experiment 2 was carried out on changes post-aestivation. Both experiments were of 2 x 4 x 2 factorial design, with two liveweight groups (smaller snails-100 to 200 g vs. larger snails-201 to 300 g), four periods (0, 2, 4 and 6 weeks) of aestivation (Experiment 1) or post-aestivation after six weeks aestivation (Experiment 2) and two types of haemolymph (oxygenated and deoxygenated). The experiments were replicated five times. Each experiment involved 40 snails. Samples of haemolymph were obtained from the mantle (oxygenated) and pedal sinus (deoxygenated). The results showed that haemolymph volume during the sixth week of aestivation declined significantly (P<0.05) by 73.3% of the haemolymph volume (8.91±0.702 ml) in the control snails. Similarly, haemolymph weight in aestivating snails declined significantly (P<0.05) by 82.6% of the haemolymph weight (9.02±0.723 g) in non-aestivating control snails at the end of the six-week aestivation period. As the haemolymph volume in aestivating snails declined, its specific gravity increased significantly (P<0.05) by 3.9% of the specific gravity (1.03±0.003) in the non-aestivating control group. During post-aestivation, haemolymph volume increased significantly (P<0.05) at the end of six-week post-aestivation period by 6.53 times the corresponding value (1.65±1.269 ml) in six-week aestivated snails, while haemolymph weight increased by 5.95 times the corresponding volume (1.84±1.279 ml) in six-week aestivated snails. However, haemolymph specific gravity decreased significantly (P<0.05) by 2.8% of the haemolymph specific gravity (1.06±0.002) in six-week aestivated control. Larger aestivating snails had a significantly (P<0.05) higher haemolymph volume and weight than smaller aestivating snails. The mantle had significantly (P<0.05) higher haemolymph volume than the pedal sinus during aestivation and post-aestivation. In conclusion, this study showed that haemolymph volume and weight declined during aestivation but increased post-aestivation due to rehydration. Haemolymph specific gravity on the other hand, increased during aestivation due to haemoconcentration, but decreased during post-aestivation due to rehydration. The compensatory phenomenon seen implied that the Giant African Snail Archachatina marginata can withstand six-week aestivation period with no adverse effect to its physiology.