Porifera Sponges

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Porifera - Sponges
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Introduction

• Sponges are considered the oldest of all animal
  phyla evolving over 500 million years ago.
• They are very simple animals that live
  permanently attached to a location in the water -
  they are sessile as adults.
• They are almost plant-like in their simplicity
  and are often confused as being plants.

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Introduction

• There are 5,000 to 10,000 known species of
  sponges living today.
• Most sponges live in salt water - only about 150
  species live in fresh water.
• Many sponges are asymmetrical, but some exhibit
  radial symmetry.
• The name Porifera means "pore bearer" in Latin.
  

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Anatomy of a Sponge

• Sponges are covered in a thin layer of cells that
  serve as an epidermis.
• Water enters numerous small pores called ostia.
• The ostia are surrounded by donut-shaped cells
  called porocytes that open and close to control
  water flow.
• Water flows directly into an open chamber called
  the spongocoel
• Water leaves the spongocoel by a larger opening
  (the osculum).

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Anatomy of a Sponge

• The interior of the spongocoel is lined with
  flagellated cells called choanocytes (or collar
  cells).
• They have a tubular collar facing the spongocoel.
  A flagellum extends from the center, the movement
  of which creates currents that force water
  through the sponge's.
• Suspended food particles (plankton) in the water
  are drawn through the collar, trapped on the
  outside, and then phagocytized.

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Anatomy of a Sponge

• The collar cells do not digest the captured food
  by themselves instead it is passed to a second
  cell (an amoebocyte) waiting in the mesohyl (the
  acellular portion of the sponge).
• Amoebocytes carry the food to other cells that
  require nutrition and thus partly compensate for
  the sponge's lack of a circulatory system.

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Anatomy of a Sponge

• Amoebocytes can also undergo developmental
  changes to turn into any other cell type that may
  be required. This allows for growth, repair, and
  reproduction of the sponge.
• In addition, they are responsible for producing
  the sponge's skeleton (a network of fibers
  flexible protein (spongin) and needle-like
  spicules).
• Spicules are usually made of calcium carbonate or
  oxides of silicon and the shape of the spicules
  is important in classification

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Anatomy of a Sponge
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Spicules

• Spicules are usually made of calcium carbonate or
  oxides of silicon and the shape of the spicules
  is important in classification

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Classification of Sponges

• There are three classes of porifera
• Class Demospongae
• Class Hexactinellida
• Class Calcarea

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Class Demospongae

• This is the largest of the sponge classes
• Consist of spongin, which accounts for their
  flexibility
• Bath Sponges

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Class Hexactinellida

• These sponges have their skeletons formed from
  silicon oxides which gives them a glassy
  appearance (their common name is "glass
  sponges").
• Nearly all are deep-water forms, living at depths
  between 200 and 1000 m.

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Class Hexactinellida

• Venus'-flower-basket (Euplectella) is an
  interesting specimen. Inside, two shrimp can be
  found (one is male, the other female). Numerous
  larval shrimp entered the sponge through the
  sieve plate at the top. The first pair to reach
  sexual maturity killed off other immature shrimp
  that had entered with them. In Japan
  Venus'-flower-baskets are given as wedding
  presents to symbolize lifelong devotion and
  fidelity (this tradition ignores, of course, the
  carnage as they reached maturity and the fact
  that the shrimp are trapped and can't escape).

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Class Calcarea

• Memebers of the group Calcarea possess spicules
  composed of calcium carbonate
• Commonly referred to as rock sponges
• Their diversity is greatest in the tropics. They
  are predominantly found in shallow waters, though
  at least one species is known from a depth of
  4,000 meters.

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Reproduction

• Sponges reproduce through both asexual (budding
  and fragmentation) and sexual reproduction.
• Sexual reproduction is timed to environmental
  cues such as water temperature, tides, and the
  phase of the moon.
• During the mating season sperm are released into
  the water and eventually enter the porocytes of
  the female sponge. The sperm are later taken up
  by choanocytes, and then passed on to amoebocytes
  which carry them to egg cells located in the
  mesohyl.

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Sponges are too Important!!!

• Sponges provide a home for a number of small
  marine plants, which live in and around their
  pore systems.
• Some of the chemicals contained in sponges have
  been found to have beneficial pharmaceutical
  effects for humans, including compounds with
  respiratory, cardiovascular, gastrointestinal,
  anti-inflammatory, antitumor, and antibiotic
  activities.

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What to see