Ctenophores Body Layers Quiz

Body Structure of Ctenophores

• Composed of a thick, jelly-like mesoglea sandwiched between two epidermal layers and an endodermis.
• Outer epidermal layer contains sensory cells that secrete mucus and interstitial cells that can differentiate into other cell types.
• Specialized outer epidermal cells include colloblasts for capturing prey and ciliated cells for locomotion.
• Inner epidermal layer includes a nerve net and muscle-like specialized cells.
• Internal cavity consists of a mouth, pharynx, stomach, and a branched canal system extending through the mesoglea.

Nutrition and Feeding

• Cilia around the mouth direct water and prey into the cavity for digestion.
• Prey digested in the pharynx using enzymes from the gastrodermis; muscle contraction aids digestion.
• Nutrient transport facilitated by cilia within the canal system and nutritive cells.
• Anal pores expel unwanted particles, with regurgitation being common for undersized matter.
• Ctenophores with short tentacles feed on the ciliated body surface; those without may consume gelatinous animals.

Prey Capture Mechanisms

• Various strategies employed for prey capture, including motionless web-like tentacles, ambush tactics, and sticky droplets to ensnare prey.
• Capture methods vary, with some species targeting strong swimmers and others preferring weaker organisms.

Movement

• Eight comb rows, or swimming-plates, equipped with cilia facilitate locomotion.
• Cilia arranged in transverse rows create waves for propulsion, starting from the aboral pole toward the oral end.

Symmetry

• Ctenophores exhibit biradial symmetry, allowing division into equal parts only in two planes, in contrast to radial symmetry.

Anatomical Features

• Body structure varies in shape: pear-shaped, cylindrical, flat, or ribbon-like; all are transparent and gelatinous.
• Lack of nematocysts; instead, they use adhesive cells called colloblasts for capturing prey.
• Absence of skeletal, circulatory, respiratory, or excretory systems; possess a diffused nervous system with a statocyst as a sensory organ.
• Monoecious reproduction with endodermal gonads located in digestive canal walls.

Diversity in Ctenophores

• Notable species include:
  • Beroe: Spherical body with mouth and statocyst.
  • Cestum: Ribbon-like with a central mouth.
  • Coeloplana: Flattened body with mouth on the underside.

Movement Dynamics

• Ciliary beating initiates at the aboral end, creating a moving wave effect toward the oral end of the comb rows.
• The organism can swim backward by reversing wave direction, allowing flexibility in movement.