Phylum Porifera: Sponges

Phylum Porifera: Overview

  • Commonly known as sponges.

General Characteristics of Phylum Porifera

  • Number of Species: Approximately 9,000 species.

  • Habitat:

    • Predominantly marine.

    • Includes around 100 freshwater species.

General Structure of Sponges

  • Canals and Pores:

    • Radial Canal: A canal structure associated with water flow within the sponge.

    • Excurrent Channel: Openings through which water and waste exit the sponge.

    • Prosopyle: An opening through which water passes into the radial canal.

    • Incurrent Canal: Channels that allow water to enter the sponge.

    • Apopyle: The opening from the radial canal into the excurrent canal.

    • Dermal Pore: Slots on the exterior of the sponge that facilitate water entry.

Sponge Morphology

  • Sponge Forms:

    • Asconoid: Simple structure with a single large central cavity (spongocoel).

    • Syconoid: More complex structure with folding walls to increase surface area.

    • Leuconoid: Most complex structure, featuring numerous flagellated chambers.

Symmetry and Reproduction in Sponges

  • Symmetry: Asymmetrical.

  • Reproduction:

    • Asexual Reproduction: Via budding (regeneration).

    • Sexual Reproduction:

    • Eggs remain within the sponge while sperm are released into the water.

    • Stages of Development:

      • Fertilization occurs, forming a zygote.

      • Zygote is "squirted out" to develop into larvae.

      • Larval stage leads to the formation of an adult sponge.

Sponge Reproductive Cycle

  • Asexual Reproduction:

    • Process involves budding, creating new sponge individuals.

  • Sexual Reproduction:

    • Fertilization: Egg and sperm cells unify to create an embryo.

    • Embryo Development:

    • Forms a planktonic larva called amphiblastula, which eventually settles on a substrate to form a new sponge.

Fascinating Facts About Sponges

  • Unique Characteristics:

    • Not all sponges have a soft texture; for example, a sponge measuring 10 cm in height and 1 cm in diameter can pump 22.5 liters of water daily (4-5 times its own volume every minute).

    • Some sponges release chemicals that are toxic to other organisms, although some compounds may have medicinal benefits.

    • If cut apart, a sponge can reassemble itself when placed in water.

Important Sponge Structures

  • Choanocytes (Collar Cells):

    • Composed of a flagellum that creates water current through the sponge.

    • Each cell has collars around it to trap food particles as water flows through.

  • Amoebocytes:

    • Function to transport nutrients throughout the sponge.

    • Responsible for the production of spicules, structural elements within sponges.

  • Porocytes:

    • Specialized cells that form pores to let water and food into the sponge.

  • Osculum:

    • The main opening for water and waste to exit the sponge.

  • Spicules:

    • Provide structural support, can be made of silica or calcium carbonate.

Water Flow and Feeding Mechanism in Sponges

  • Water Flow:

    • Water enters through porous openings, passes through the sponge body, and exits through the osculum.

  • Feeding Process:

    • Food particles such as organic material, phytoplankton, and detritus are filtered from the water, primarily consumed by choanocytes.

Questions to Consider About Sponges

  1. Structures of a Sponge: What are the different physical structures that make up a sponge?

  2. Phylum Classification: To what phylum do sponges belong?

  3. Type of Symmetry: What is the symmetry exhibited by sponges?

  4. Digestion Process: How do sponges perform digestion? The digestion is intracellular as food particles must be small enough to diffuse into the cell.