Introduction to Porifera

Question 1

Sponges are ‘basal’ animals. what does this mean?

Answer 1

• it means that they branched off the earliest/ at the base of the ‘evolutionary tree’

Question 2

What are sponges?

Answer 2

• Phylum Porifera
• they are stiffened, perforated, asymmetrical sacs lined with flagellated cells
• they are motile as larvae but sessile as adults
• they are suspension feeders
• only 2% are freshwater, 98% are marine

Question 3

Why are sponges important for our environment

Answer 3

• along with corals, they are major reef building organisms

Question 4

Sponges lack ____ ____ layers, meaning they have no ectoderm, endoderm, or mesoderm

Answer 4

LACK EMBRYONIC GERM LAYERS

Question 5

Sponges have poorly defined tissues and dedifferentiation of cells. What does this mean?

Answer 5

• specialized cells (like a choanocyte) can morph or dedifferentiate into amoebocytes

Question 6

What are the major 4 different cell types for sponges?

Answer 6

• choanocytes
• archaeocytes
• pinacocytes
• porocytes

Question 7

What are choanocytes?
its functions?

Answer 7

• cells that line the lineside of the hollow cavity of a sponge (kinda look like sperm)
• creates a feeding current, flagellum are used to draw water into the sponge
• they also trap food particles in their ‘collars’
• collars also are used to trap sperm cells during reproduction

Question 8

What are archeocytes?
its functions?

Answer 8

• they are amoeboid cells in sponges
• they are used to digest food and distribute the nutrients throughout the sponge
• also builds spicules and secrete spongin (structural features of the sponge)

Question 9

What are pinacocytes?

Answer 9

• cells within sponges
• they are the outer most cell layer, which provides a protective surface for the sponge, and chemical defense

Question 10

What are porocytes?

Answer 10

• cells within sponges
• “pores” connecting outside environment and inner sponge (“spongocoel”)
• provides a channel for water to be brought into the sponge, to allow water to reach choanocytes

Question 11

What are spicules? Spongin?

Answer 11

• both support structures for sponges
• spicules are calcareous or siliceous defensive structures that can be found in a variety of shapes
• spongin is a collagenous protein

Question 12

What is the route of water as it passes through a sponges body?

Answer 12

• water enters via the ostia (opening) in the porocyte
• water passes by the choanocytes, arranged into chambers
• nutrients collected/trapped by collars of choanocytes
• waste water passes out the osculum (hole at the top of a sponge)

Question 13

Caloric intake of sponges is dependent on what factors?

Answer 13

• the nutrient concentration in water
• the rate at which water passes through the sponge
• the contact time water has with the choanocytes