DEEP-SEA SPIDERS THAT WALK THROUGH THE WATER

Deep-sea isopods of the family Munnopsidae exhibit four modes of swimm ing: forward striding, slow backward pedalling, fast backward pedallin g and escape, the first two of which use asymmetric phases of leg move ment, Instead of moving the left and right limbs (pereopods, P-2-P-7) of a segment in-phase (e.g. RP(2)LP(2), RP(3)LP(3), RP(4)LP(4)), as do most aquatic insects, leg movement is more like that of fastwalking i nsects, where closest synchrony occurs between diagonal limbs (e.g. RP (2)LP(3), RP(3)LP(4), RP(4)LP(2)). This is similar to the alternating tripod gait used by many animals on land to prevent them from toppling over. It therefore seems likely that this group of isopods learned to walk before they could swim.