Module 3 - Ctenephora

• Defining characteristics of Ctenophores:

  • Superficially resemble cnidaria
  • Lack nematocysts, have colloblasts (adhesive prey-capturing cells)
  • Have a complete gut
  • Name derived from ‘ctenes’—plates of fused cilia arranged in rows (comb rows or costae)
• Ctenophores have biradial symmetry and a trans-tentacular muscle (T.T. muscle) and apical organ and tentacle apparatuses muscle (A.O. muscle)
• Ctenophores are diploblastic, with each layer being 2 cell deep, but can be considered intermediate between diploblastic and triploblastic
• Ctenophores' musculature develops from ameboid cells into muscle fibers in mesoglea, primarily responsible for maintaining body shape and escaping predators
• Ctenophores are planktonic and weak swimmers, propelled by bands of partially fused, long cilia arranged in 8 rows (comb rows or costa) that beat in metachronal waves
• Ctenophores have apical sense organs called statoliths, sub-epidermal nerve networks, and nonpolar neurons forming elongate plexes
• Ctenophores are carnivorous, using solid tentacles studded with colloblasts to capture prey, and have a digestive system consisting of mouth, pharynx, stomach, and digestive canals
• Ctenophores reproduce sexually as hermaphrodites or rarely gonochoristic, with external fertilization and determinate cleavage
• Ctenophores exhibit iridescence and bioluminescence, possibly for mate location, prey attraction, predator avoidance, and species recognition
• Ctenophoran diversity includes classes like Tentaculata and Nuda, with orders like Cydippida, Lobata, Cestida, and Platyctenida, each with unique body structures and feeding mechanisms