Polyp: Sessile, tubular body morphology with oral surface directed upward.
Respiration: Tracheal tubes (Hexapoda), book lungs (Arachnida), or gills (Crustacea). invertebrate zoology lecture notes ppt new
If you're interested, I can also provide specialized lecture topics, such as "Advanced Arthropod Physiology" or "The Phylogeny of Lophotrochozoa." Polyp: Sessile, tubular body morphology with oral surface