Choanoderm

Definition

The choanoderm is the innermost layer of cells in sponges, specifically composed of specialized cells called choanocytes. These cells play a crucial role in the feeding mechanism of sponges, as they possess flagella that create water currents, allowing for the filtration of food particles from the water. The choanoderm is vital not only for nutrient acquisition but also for gas exchange and waste removal in these simple aquatic organisms.

5 Must Know Facts For Your Next Test

1. The choanoderm consists primarily of choanocytes, which are essential for the sponge's feeding strategy by trapping bacteria and organic particles.
2. Choanocytes have a unique structure with a flagellum that beats to create a current, drawing water into the sponge and through the ostia.
3. The water flow generated by choanocytes not only facilitates feeding but also plays a role in respiration by allowing gas exchange.
4. The efficiency of the choanoderm in filtering water directly impacts the sponge's overall health and its ability to thrive in various aquatic environments.
5. In some sponge species, choanocytes can transform into sperm or egg cells during reproduction, illustrating their versatility beyond just feeding.

Review Questions

• How do choanocytes contribute to the feeding mechanism in sponges?
  • Choanocytes are specialized cells within the choanoderm that play a crucial role in the sponge's feeding mechanism. They have flagella that create water currents, drawing water through the ostia and into the spongocoel. As water flows past the choanocytes, they capture food particles like bacteria and organic debris using their collar of microvilli, effectively filtering nutrients from the water.
• Discuss the significance of the choanoderm in maintaining sponge homeostasis.
  • The choanoderm is essential for maintaining homeostasis in sponges as it facilitates nutrient uptake and waste removal. The continuous flow of water generated by choanocyte activity allows for efficient gas exchange, ensuring that oxygen is delivered to cells while carbon dioxide is removed. This dynamic process not only supports metabolic functions but also contributes to the overall health and resilience of sponges in their aquatic habitats.
• Evaluate how changes in environmental conditions might affect the function of the choanoderm and overall sponge health.
  • Environmental changes such as pollution, temperature fluctuations, or alterations in water flow can significantly impact the function of the choanoderm. For instance, increased sedimentation can clog the ostia, reducing water flow and limiting feeding efficiency. This decline in nutrient acquisition can lead to weakened immune responses and reduced reproductive success. Furthermore, if gas exchange is impaired due to stagnant waters, sponges may experience stress or even mortality. Understanding these relationships highlights the importance of the choanoderm in sponge ecology and their vulnerability to environmental changes.

Related terms

Choanocyte: A type of cell found in sponges, equipped with a flagellum surrounded by a collar of microvilli, which helps in capturing food particles from the water.

Ostia: Small pores on the surface of a sponge that allow water to enter into its body for filtration and feeding.

Spongocoel: The central cavity within a sponge where water flows through after entering via ostia, leading to the exit through the osculum.