Meeting Abstract

20.5  Sunday, Jan. 4  Similar motor pattern generators produce flexible walking behavior in juvenile and adult crayfish RINEHART, MD*; BELANGER, JH; West Virginia University; West Virginia University mrinehar@mix.wvu.edu

We have shown previously that juvenile and adult crayfish (Procambarus clarkii) use different stepping patterns when freely walking. These differences are primarily due to an increase in relative stance durations in the posterior two pairs of legs and a decrease in relative stance durations in the anterior two pairs of legs in the juveniles. In order to determine whether these differences are caused by inherent differences in coupling relationships between limbs, we re-created treadmill experiments conducted on adult crayfish in which limb coordination was observed after amputation of one, two, or all ipsilateral limbs. Stepping patterns were altered based on which leg was amputated with the adjacent legs showing the most change. In all cases intact legs adjacent to amputated limbs increased stance times with the anterior adjacent leg functionally replacing the missing limb. Protraction of the amputated fourth right leg (R4) showed synchrony with the anterior leg three (R3) when only leg R4 was missing and again when R4 and R3 were both amputated. Upon amputation of all right legs we observed an ascending metachronal wave of activity in the stumps; however, under this condition relative timings showed large amounts of variation. These results largely agree with the autotomy experiments conducted in adult crayfish and imply that central circuitry in the juveniles is similar to adults. This also suggests that observed differences in freely walking juveniles and adults are more likely due to altered sensory feedback, changes in relative load distributions, and/or differences in relative hydrodynamic forces.