Sponge Anatomy and Function

• Sponges can reorganize themselves within minutes after being cut into pieces.
• Sponges possess 18 different cell types including sensory cells, external pinacoderm, a mesophyll containing skeletal elements and free cells, and internal choanoderm.

Sponge Anatomy and Function

• Myocytes form pores, regulating water entry.
• Water enters sponges through pores, flowing inside the cells.
• Choanocytes process food and extract nutrients from the water.
• Water exits the sponge through the osculum, located at the top.
• The aquiferous system is responsible for circulating water.
• Depending on the sponge type, water and nutrients pass through secondary cavities before reaching the internal cavity.
• Choanocytes have a neck called the colliard and a flagellum.
• Spongin forms collagen fibers, creating the skeletal structure.
• Archaeocytes generate spicules or spongin, while spongocytes can also produce spongin.
• Spicules of glass silica or calcium carbonate are produced by specific cells.
• Sponge classification relies on skeletal structure and aquiferous system traits.

Reproduction & Development

• Archaeocytes generate spicules or spongin, involved in reproduction and reside within the mesoglea or mesophyll.
• Archaeocytes are pluripotent cells.
• During sexual reproduction, sponges produce larvae that move to establish new sponges elsewhere.
• Gemmula are released as budding bodies for asexual reproduction, a form of larvae that settles to generate new sponges.
• Archaeocytes are involved in asexual reproduction; choanocytes involved in sexual reproduction.

Germ Layers

• Sponges were not considered to have true germ layers until 2020.
• New evidence classifies sponges as diploblastic.

Sponge Types

• Ascinoid sponges have porocytes that form pores.
• Water enters through these pores into an internal cavity lined with choanocytes, then exits through the osculum.
• Syconoid sponges have porocytes that allow water into chambers lined with choanocytes.
• Water is processed in these chambers before exiting.
• Leuconoid sponges are the most complex type.
• Leuconoid sponges contain complex chambers.
• Water flows through multiple chambers.
• Nutrients are extracted and waste excreted in chambers, which connect via canals.
• Canals then exit through multiple oscula.
• Leuconoid sponges reproduce sexually, forming amphiblastula larvae.

Symbiotic Relationships

• Sponges have symbiotic interactions with invertebrates like arthropods or crustaceans.
• Some sponges form close relationships with shrimp.
• Male and female shrimp may live inside a sponge permanently eg "wedding shrimps".
• Young O. plectella sponges can trap shrimp inside.
• Shrimp grow too large to escape the sponge's mesh-like osculum, even after the sponge dies.
• In Japan, it is used as a wedding gift.
• The shrimp are white due to never being exposed to light in the deep ocean.
• Sponges gives shrimps a secure environment, protection from predators, clean water, and nutrients.
• The sponge-shrimp relationship may date back to the Jurassic era.

Glass Sponges (O. plectella)

• The structure of O. plectella has been studied by many researchers.
• The glass in glass sponges combines different fibers, providing flexibility.
• Filaments are arranged horizontally, vertically, and diagonally.
• Diagonal filaments protect the structure from torsion.
• Spider-like ribs safeguard it from collapsing.
• The sponge anchors to the seabed with glass fibers.

Habitat

• Freshwater sponges are rare and usually found in temperate waters.
• Freshwater sponges are generally smaller and simpler than marine sponges.
• Seawater sponges are found worldwide.