PHYLUM PORIFERA:


"The Sea's Quicker-Picker-Upper"


What is Phylum Porifera:

Phylum Porifera are the sponges and they are the simplest of all animals.  Although they are multicellular...they wouldn't be an animal if they weren't, they are organized on a cellular level only.  In other words, each cell functions independently from any other cell and no cells work together in a group (such as a tissue).  Because of this characteristic, sponges are often referred to as being Parazoan. Since sponges are only organized on a cellular level, they do not have any germ layers during development and have no coelom or pattern of development.

What do they look like:

The name Porifera means "to have pores", and sponges have a lot of them.  Basically, a sponge looks like a sack perforated with tiny holes.  Sponges may be a multitude of colors ranging from bright red, to drab gray.  They are generally asymmetrical (have no symmetry), but may be shaped like fans, balls, or vases. Because their shape and the fact that they are sessile (no movement), they are often confused as plants and fungi.

Important structures, mechanisms, and characteristics:

    Anatomy & Physiology:

General Shape & Structure:

Most sponges are basically a hollow cylinder surrounded by a wall two cell layers thick.

Ostia:
Many small pores that allow water to enter.

Oscula:
One or more large holes where the water exits the sponge

Spongocoel - Hollow center of sponge

Skeleton Made of:

Spicules:
A sponge's body is little more than masses of cells embedded in a matrix of spongin and spicules.  The spicules are generally hard structures made of calcium, silica, or both and may or may not be embedded in a matrix of spongin.

Spongin- A fibrous "soft" material that makes up the matrix of the skeleton

Types of Spicules

.........................................
         Spicule (SEM)                                 Spongin Fibers (SEM)                      Spongin and Spicules(SEM)

Feeding, Digestion & Excretion:

Sponges are filter feeders in that they collect microscopic food particles by using colar cells to create a water current through their body

Choanocytes: (Colar cells)
The working cells of a sponge are called choanocytes or collar cells.  They are flagellated and create water movement within the body of the sponge.  The collar of the choanocyte fitters the water for food particles.

Amebocytes- transport food from colar cells to other parts of the sponge

      Water movement:

Water outside --> Pores --> Ostia --> Incurrent canal --> Filtered by Choanocytes --> In Spongocoel --> Out Osculum

Dyed water being expelled out of the osculum of a tube sponge.

Respiration & Circulation:

Respiration by diffusion

Circulation is not necessary

Sensory & Movement:

No neural tissue - sensory ability limited

Movement only in larvae

Reproduction:

Asexual-

Budding

Gemules - spore-like structures produced during harsh conditions that allow the sponge to remain dormant

Regeneration - If you cut a sponge into many pieces they can grow into new sponges

Sexual

Hemaphroditic (have both sexes) but cant self fertilize

Larvae that is produced through fertilization can swim to uninhabitable areas

Notice the cloud above the osculum. This is a sponge releasing its sperm. Sperm will swim to another sponge to mate.

Types of canal systems:

        

      Characteristic:

Classification:
     Class Calcarea
     Class Hexactinellida
     Class Demospongiae


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