Biology of Sponges Quiz

Porifera (Sponges)

• Phylum Porifera, also known as "pore bearers", are multicellular, aquatic animals
• Sponges lack true tissues and organs
• They have a cellular level of organization, where cells are loosely aggregated and perform specific functions
• They are mostly marine and entirely benthic
• They range from 5-10 thousand known species
• Reproduction is both sexual and asexual, with many species being hermaphroditic (monoecious)
• Some are gonochoristic (dioecious)
• Adult sponges are suspension feeders
• They feed on phytoplankton, small zooplankton, and bacteria
• Fossil forms date back as far as 750 million years ago
• Sponges lack a gut, circulatory system, body cavity, nervous system, organs, and have no symmetry
• Specialized water movement cells, including choanocytes
• Spicules are made of silica or calcium carbonate
• Spongin is a collagen-like protein that gives many sponges their structural support

Porifera Body Plan

• Water flow enters through pores (ostium)
• Water flows through channels (atrium)
• Water exits through a large opening (osculum)
• Choanocytes line the channels and create water current to filter food particles
• Specialized water movement cells in sponges are essential for their feeding and survival

Major Cell Types

• Choanocytes: collar cells, responsible for feeding and creating water movement
• Pinacocytes: flat cells that form the outer layer of the sponge
• Porocytes: tube-like cells that form pores in the sponge
• Archaeocytes: amoeboid cells that can differentiate into other cell types, including sclerocytes and spongocytes
• Sclerocytes: specialized cells that secrete spicules
• Spongocytes: specialized cells that secrete spongin fibers, providing further structural reinforcement for the sponge

Sponge Reproduction

• Asexual reproduction occurs through fragmentation and budding
• Gemmules are a specialized form of asexual reproduction in which internal buds (gemmules) are formed, each potentially capable of developing into a new sponge.
• When conditions are unsuitable, sponges release gemmules which can later develop
• Sexual reproduction involves the release of eggs and sperm, which can be released from the sponge and then taken up by other sponges for fertilization
• Further development results in a parenchymula larva that settles and develops into an adult sponge

Sponge Body Structure

• Three grades of body structure exist: asconoidea, syconoida, leuconoida
• Larger sponges exhibit a greater degree of internal complexity, reflecting their need for more extensive water flow systems for filtration of food

Sponge Spicules

• Spicules are made of either silica or calcium carbonate
• Provide structure support and defense against predators

Phylum Placozoa

• Approximately 20 species from the 1800s
• No tissues or organs
• They reproduce asexually by fission
• Mostly found in shallow coastal waters
• They exhibit a unique and simple body structure
• They have no true tissues or organs
• Body symmetry is asymmetrical

Additional information

• Sponges are important filter feeders and contribute to their environments' water quality
• Sponges serve as habitat for various other animals
• Some species of sponges have chemical defenses