Practice question

Pseudocoelomate body plan shows variation among Aschelminthes. In Nematoda body wall comprises resistant collagenous cuticle, syncytial hypodermis and only longitudinal muscle layer, circular muscle absent, enclosing fluid-filled pseudocoel at high turgor functioning as hydroskeleton. Musculature restricted to outer peripheral position muscles lie only on outer side of pseudocoel not lining gut. Contrasts with true coelomates where muscle layers border both sides of coelom. High internal pressure enables undulatory thrashing locomotion. Hence animal exhibiting pseudocoelom with muscle solely peripherally corresponds to nematode organization illustrating evolutionary intermediate between acoelomate and eucoelomate architectures and adaptation to interstitial and parasitic existence worldwide.