Overview of Invertebrate Phyla and Classes

Phylum Porifera

A phylum of simple aquatic animals known as sponges.

Class Demospongiae

A class of sponges characterized by a skeleton made of spongin and/or silica.

Class Calcarea

A class of sponges that have a skeleton made of calcium carbonate.

Class Hexactinellida

A class of sponges known as glass sponges, characterized by a siliceous skeleton.

Class Holoscleromorpha

A class of sponges with a skeleton that lacks the typical spicules found in other classes.

sessile

Organisms that are fixed in one place and do not move.

filter feeders

Organisms that obtain food by filtering small particles from water.

radial symmetry

A body plan in which body parts are arranged around a central axis.

Spicules

Small, needle-like structures found in the skeleton of sponges.

Spongin

A fibrous protein that makes up the skeleton of some sponges.

Pinacocytes

Flat cells that make up the outer layer of a sponge.

Pinacoderm

The outer layer of cells in sponges.

Mesohyl

The gelatinous matrix found between the outer and inner layers of a sponge.

spongocoel

The central cavity of a sponge where water flows through.

Choanocytes

Flagellated cells in sponges that help in water circulation and food capture.

Choanoderm

The inner layer of cells in sponges, composed of choanocytes.

Archaeocytes

Totipotent cells in sponges that can differentiate into various cell types.

Sclerocytes

Cells in sponges that produce spicules.

Asconoid

The simplest body form of sponges, characterized by a tubular shape.

Syconoid

A more complex body form of sponges with a folded body wall.

Leuconoid

The most complex body form of sponges, with multiple chambers.

stolon

A horizontal stem that connects individual sponges.

Osculum

The opening at the top of a sponge through which water exits.

Ostia

Small openings in a sponge's body through which water enters.

Radial canal

Canals in sponges that lead from the ostia to the spongocoel.

Incurrent canal

Canals that allow water to flow into the sponge.