lecture 6 recording on 27 January 2025 at 09.50.56 AM

Understanding Calcareous Sponges

• Calcareous Sponges Characteristics

  • Prefer stable temperature environments, indicating a relation to latitude.

  • Thrive in warm waters, showing limitations in their geographical range due to temperature extremes.

• Physiological Needs

  • Require water conditions that are not too hot or too cold.

  • Their distribution offers insight into their evolutionary origins and adaptability.

• Diversity and Evolution

  • Observations from diversity maps indicate a concentration of species diversity notably in the Indo-Pacific region.

  • Suggests a historical hotspot for sponge diversity, correlating with the evolutionary timeline from one to multiple species.

  • Hotspots indicate regions where the group has existed for extensive periods.

Ecological Role of Sponges

• Habitat Provision

  • Sponges create environments for other organisms, acting as shelters.

  • Example organisms include amphipods and various small fish that use sponges for protection and camouflage.

• Camouflage Mechanisms

  • Small animals may use sponge coloration to blend into their surroundings, providing a form of camouflage.

  • Notable example: the decorator crab adorns itself with sponge material for increased concealment.

• Sponge Reefs

  • Some marine areas feature sponge reefs, with sponges acting as the dominant structural organisms.

  • Demonstrates a different ecological niche compared to coral reefs, with sponges serving as critical habitat providers.

Interactions with Other Species

• Feeding Relationships

  • While sponges are not primarily preyed upon, certain species, including sea turtles and some fish, feed on them.

  • Freshwater fly larvae also utilize sponges as a food source.

• Competitive Dynamics

  • Sponges must defend territory from other organisms, as they are sessile and cannot relocate.

  • Chemical warfare: sponges secrete substances to inhibit the growth of neighboring corals and other competing organisms.

  • Dominance can lead to exclusion zones around sponge colonies.

Predatory Behavior of Sponges

• Boring Sponges

  • Certain sponges bore holes into shells, feeding on the organisms inside, showcasing predatory behavior.

  • Mechanisms of attack include physical drilling and chemical dissolution of tissue.

• Chemical Warfare Studies

  • Specific sponges (e.g., Pseudonella swinohoei) are studied for the unique chemicals (e.g., PBDE) they produce, which can deter or kill nearby organisms, including corals.

  • These chemicals have potential applications in understanding both ecological dynamics and human uses.

Biological Mobility and Response

• Sponges' Movement and Adaptation

  • While often perceived as stationary, sponges can exhibit slow movements to better locations through growth patterns.

  • Some sponges demonstrate movement by excavating through materials to find a suitable habitat.

• Sponges' Immune Response

  • Sponges can distinguish between self and non-self entities, akin to immune responses in higher organisms.

  • Physical contact with other sponges can lead to rejection or acceptance based on genetic similarity.

Physiological Mechanisms of Water Flow

• Choanocyte Functionality

  • Choanocytes (cells responsible for water flow in sponges) are pivotal in maintaining water circulation.

  • Experiments show that these cells contribute significantly to the flow of water through sponges, highlighting their efficiency even when isolated.

• Impact on Ecosystem Dynamics

  • Vital for nutrient cycling in marine ecosystems, as sponges filter substantial amounts of water, impacting surrounding biodiversity.