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 colorful Freshwater 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 OUT Water Flow Through the Sponge WATER IN Osculum

3 Basic Cell Types Pinacocytes Mesenchyme Cells 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 Silica Spicules Limestone Spicules SPONGIN

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 Osculum Cross-Fertilization takes place in the ocean Fertilized eggs form larvae which swim off looking for a place to settle

Sponge Releasing Eggs & Sperm Reproduction Sponge Releasing Eggs & Sperm

Reproduction Cont’ Sponges can regenerate (regrow) lost body parts through mitotic cell division (asexual) Sponges also reproduce asexually by (budding)

Reproduction Cont’d gemmule Asexual Reproduction- involves the formation of gemmules gemmules: resistant capsules that sponges release to survive unfavorable conditions. When conditions become favorable, the gemmules sprout into sponges.

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