Practice question

Rotifera placed in Superphylum Gnathifera are pseudocoelomate bilaterians possessing persistent blastocoel between epidermis and gut serving as hydrostatic skeleton and nutrient distribution medium, not true mesoderm-lined cavity. Cavity lacks complete peritoneal lining, distinguishing from true coelom where mesoderm epithelium covers entirely. Rotifers display eutely with constant cell number about thousand, bilateral symmetry, visceral musculature and complete alimentary canal including mouth and anus. Acoelomates have solid body without cavity like flatworms, coelomate and eucoelomate terms imply fully lined coelom as in annelids arthropods. Pseudocoelomate organization explains small size, diffusion dependence and absence of circulatory system despite organ-level complexity.