Unit 5 Notes #2 - PHYLUM PORIFERA –Sponges ("pore-bearers")
-The most ancient and primitive of all animals alive today.
-Live in the sea, some live in fresh water, lakes and streams.
-Inhabit most areas of the sea (polar regions to tropics, low-tide to hundreds of meters deep).
-"Pore-bearers" (tiny openings all over multicellular body)
-No cell walls.
-Contain special cell types that live together, but show no specialized tissues or organs working together.
- Show no movement (Non-motile / Sessile)
B) Body Plan:
-A wall around a central cavity, like radially-symmetrical vases.
-Body consists of thousands of pores called Incurrent Pores. (Ostia)
-Water enters the sponge pores because of the action of flagellated collar cells, these cells create an incurrent.
-Water exits through a large opening called the Osculum (Excurrent pore).
-The body wall consists of two layers:
a) 1 layer (inside) is made up of special cells called Collar Cells (Choanocytes), this layer is called the Endoderm.
-Each collar cell has a fringe collar surrounded by a large flagellum.
-Separating the two layers of cells is a layer of non-living jelly-like material called Mesoglea.
-Mesoglea contains some amoeboid cells (amebocytes) which build spicules.
-These Spicules are branched needles of either calcium carbonate or silica which support the bodies (act as a skeleton) of some sponges. Other sponges produce softer skeletons made of spongin-protein.
b) Second layer (found to the outside) is called the Ectoderm.
C) Reproduction : Both Asexual and Sexual
-Some cells in the Mesoglea can become Eggs or Sperm.
-Sperm cells reach the egg by water currents.
-Each fertilized egg becomes a flagellated larva, which swims to a new location and becomes attached to some object.
2) Asexual Reproduction
-When conditions deteriorate, a resting/dormant stage called a GEMMULE is produced. When conditions are favorable, it germinates into a new sponge.
-The sponge can also use budding: (the budding out and breaking off of certain cells that go onto regenerate, the result is a new miniature sponge that is a clone of its parent)
D) The Process of Filter Feeding:
- Sponges are filter feeders that sift microscopic particles of food from water that passes through them.
-Tiny food particles stick to the collar cells, where they are digested.
- Whatever particles are not digested by the collar cells, are passed on to the amebocytes. The amebocytes can then deliver this food to other cells of the sponge.
- Water flowing through a sponge, simultaneously serves as its respiratory, excretory, and internal transport system.
- As water passes through the body wall, sponge cells remove oxygen from it and give off carbon dioxide into it.
- Metabolic wastes/toxins produced by cellular respiration (like ammonia) are also released into the water.
E) Ecological Roles of Sponges:
1) Many other marine animals live on, in and under sponges.
Example: shrimp, snails, and starfish
2) Sponges are an important part of the diets of certain snails, starfish and fish.
3) Special amebocytes release chemicals that allow the sponges to bore/drill so that they can tunnel through old shells and pieces of coral.
4) Used in bathing. (Spongin protein)
5) To protect themselves from being overgrown by organisms; sponges use microbes to manufacture numerous compounds that are toxic to such organisms. Many of these chemicals are powerful antibiotics that can be used to fight bacteria and fungi that cause disease.