Phylum Porifera Flashcards

Phylum Porifera (Sponges) Overview

• Sponges belong to the Phylum Porifera, a group of simple, aquatic organisms known for their porous bodies.
• They perform filtration feeding by drawing water through their bodies to extract food particles.

Key Terminology

• Osculum: Large opening through which filtered water is expelled from the sponge.
• Spicule: Needlelike structures providing support and protection, preventing entry of small animals.
• Choanocyte (Collar Cells): Specialized cells with flagella that create water currents for filtering food.
• Budding: Asexual reproduction method where new organisms grow off the parent sponge.
• Asexual Reproduction: Process involving one parent to produce genetically identical offspring.

Classes of Sponges

• Class Calcarea: Characterized by calcium carbonate spicules; includes simple forms of sponges.
• Class Hexactinellida: Known as glass sponges, distinguished by silica-based spicules.
• Class Demospongiae: Largest class with around 7,000 species; features silica spicules and/or spongin.
• Class Homoscleromorpha: Smallest class of sponges with silica spicules, often encrusting in form.

Sponge Body Forms

• Ascon Body Form: Features a simple, stalk-like structure with a single layer of choanocytes lining the spongocoel.
• Sycon Body Form: More complex with folded canals lined with choanocytes, enhancing surface area for filtration.
• Leucon Body Form: Highly complex with no central cavity, featuring narrow canals and numerous interconnected chambers.

Sponge Structure and Function

• Ostia: Small incurrent holes that facilitate water influx into the sponge.
• Pinacocytes: Protective outer layer of cells that also form ostia; serve as a skin for the sponge.
• Mesohyl Layer: Jelly-like layer beneath pinacocytes; contains various cell types including amoebocytes.
• Mesenchyme Cells (Amoebocytes): Amoeboid cells involved in reproduction, structure secretion, and nutrient transport.
• Spongin: Collagen-derived protein that provides spongy texture and flexibility to some sponges.

Reproductive Structures and Processes

• Gemmule: Asexual reproductive structure encased in a hard shell, produced during adverse environmental conditions.
• Fragmentation: Asexual reproduction involving the splitting of the parent sponge into parts that regenerate.
• Monoecious: Organisms possess both male and female reproductive organs (hermaphroditic) allowing for internal fertilization.
• Sexual Reproduction: Involves two parents that contribute genetic material to produce genetically diverse offspring.

Feeding Mechanism

• Filter Feeders: Sponges filter water to extract food, showcasing their role in aquatic ecosystems as efficient filter feeders.