Phylum Porifera

General Characteristics SPONGES!

Simplest of all animals Cellular level organization

Specialized cells, but no tissues (bodies are a loose aggregation of cells)

No true tissues or organs Radial or asymmetrical Marine and Freshwater

Saltwater are colorfulFreshwater are dull green color

General Characteristics Cont.• Sponges are sessile (not free moving) as

adults • Free swimming larval stage called dipleurula • Porifera means pore-bearing• Water enters through pores (ostia) bringing

in food and oxygen• Sexual & Asexual Reproduction• Osculum- large opening at the top where

excess water leaves

Water Flow Through the

Sponge

WATER IN

WATER OUT

Osculum

3 Basic Cell Types

1. Pinacocytes

2. Mesenchyme Cells

3. Choanocytes

3 Basic Cell Types• 1. Pinacocytes- flat cells that line the

outer surface of the sponge.–May be slightly contractile–Porocyte: a specialized type of

pinacocyte; are tube-like in shape; contractile; and can regulate water circulation.

2. Mesenchyme Cells- move around in the mesohyl layer; are specialized for reproduction, secreting the skeleton, transporting/storing food.Amoebocyte: jelly-like layer just

underneath the pinacocyte layer. (makes spicules – skeletal)

• 3. Choanocytes- flagellated cells that line the inner chamber of the sponge; called collar cells.–Flagellum: flagella spins to create

water currents to pull in water and food–Collar: “trap” plankton and other fine

particles from the water

Choanocyte

Choanocyte

Structural Skeleton Consists of either one or all of the

following:Spicule: microscopic needle-like

spikes that are made of Calcium carbonate (CaCO3) or silica (glass).

Spongin: a fibrous protein made of collagen

Sponge Skeletons

SPONGIN

Silica Spicules

Limestone Spicules

Sponge Body Types

• 3 Kinds-–Ascon– Sycon–Leucon

Ascon• Simple tube perforated by pores• Open internal part of tube is called the spongocoel

(coel = gut)• Are vase-like• Least common type of sponge• Single opening to the outside called the osculum

Sycon

• Sponge wall is folded into canals• Choanocytes line the

radial canals to move water

osculum

Leucon• Have an extensively branched canal system.• Multiple canals lined with flagellated cells• Multiple ostia

for water to exit• Increased surface

area means more water can move through sponge

Body Forms Summary

Reproduction Sexual Reproduction- sponges are

monoecious (male and female in the same body)Release sperm and eggs into the water

from the OsculumCross-Fertilization takes place in the

oceanFertilized eggs form larvae which swim off looking for a place to settle

ReproductionSponge

Releasing Eggs & Sperm

Reproduction Cont’

oSponges can regenerate (regrow) lost body parts through mitotic cell division (asexual)

oSponges also reproduce asexually by (budding)

Reproduction Cont’d

Asexual Reproduction- involves the formation of gemmulesgemmules: resistant capsules that

sponges release to survive unfavorable conditions.When conditions become favorable, the

gemmules sprout into sponges.

gemmule

CLASSES

• Phylum Porifera–3 Classes•Class Calcarea•Class Hexactinellida•Class Demospongiae

Class Calcarea

• Spicules made of Calcium Carbonate • Can have all three body forms• Most primative• Ex. Grantia

Class Hexactinellida

• Deep sea sponges• Can have syncon or leucon body

forms–Often fused into an intricate lattice–Glass sponges (silica)

Class Demospongiae• Spicules made of silica, spongin, or both.• Most common (fresh (green) & salt)• All are Leuconoid• Ex: bath sponge