Peristatic Contractions

Through the hydrostatic skeleton, annelids achieve various forms of locomotion. Swimming is enabled by undulation; as contrasting longitudinal muscles pass from head to tail, water or mud is pushed backwards, and thus the worm forwards .Additionally, peristatic contractions permit both crawling and burrowing. Longitudinal muscles contract, anchoring the worm to substratum and subsequently, circular muscles contract to stretch the worm. Crawling is aided by segmentally organised chaeta as seen in the Subclass Oligochaeta, Clade Clitella. Furthermore, septa assist in both crawling, and maintaining the worm. By facilitating widening and elongation, peristaltic contractions can reach otherwise constrained