Sclerocytes (Sponge Spike Makers)

Tiny builders

Sponges are animals that live in water and stay stuck in one spot. Many of them have a skeleton made of tiny hard pieces called spicules (say "SPIK-yools").

Spicules are built by cells called sclerocytes (say "SKLAIR-oh-sites"). Some sclerocytes build a spicule inside themselves. Others team up to build one together.

Spicules come in lots of shapes: straight needles, stars with three or four points, and even little hooks and anchors.

Building a skeleton

Sclerocytes take things from the seawater and use them to build spicules. Some sponges make spicules out of glass. Others make them out of chalk, the same kind of stuff as seashells.

Thousands of spicules hold the sponge up and help keep its shape. Their sharp points may also make the sponge a prickly, less tasty meal for fish.

Your bones are made by bone cells in a similar way: cells build a hard skeleton out of minerals.

Sclerocyte quiz