Sponges are among the simplest animals, yet their bodies contain specialized cells that work together to move water, obtain food, and provide support. This lesson introduces their place in animal diversity, basic body plan, and key cell types.
The phylum Porifera includes the animals commonly called sponges. Porifera means “pore-bearers,” a reference to the many openings through which water enters their bodies. Sponges are often placed with Placozoa in the clade Parazoa, animals that lack the organized true tissues found in Eumetazoa.
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What are ostia?
Ostia are small openings in the sponge body through which water enters.
What is the osculum?
The osculum is a large opening through which water leaves the sponge.
What do choanocytes do?
Choanocytes use a beating flagellum to draw water through the sponge and a collar of microvilli to trap food particles, which they ingest by phagocytosis.
What is the mesohyl?
The mesohyl is a jelly-like region between the outer covering and feeding chambers. It contains fibers and mobile or specialized cells, including amoebocytes and sclerocytes.
What do amoebocytes do?
Amoebocytes move through the mesohyl, distribute nutrients, and can develop into other cell types. They can also give rise to eggs.
Quiz questions
What distinguishes Parazoa from animals with true tissues?Answer: Parazoans lack organized true tissues.
Which skeletal combination characterizes sponges in class Calcarea?Answer: Calcium carbonate spicules and no spongin.
Which feature is characteristic of glass sponges in class Hexactinellida?Answer: Many body cells form a multinucleate syncytium, and the mesohyl is absent.
Where does digestion take place in sponges?Answer: Within individual cells.
What does it mean for a sponge to be monoecious?Answer: One individual can produce both eggs and sperm.
Based on Biology 2e by Mary Ann Clark, Matthew Douglas, Jung Choi (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.