GENERAL HISTOLOGY

Detailed explanation-1: -The urchins have been particularly devastating for bull kelp, the main species off Northern California. The plants only last a year, re-growing every spring. But as soon as the adult plants release spores to seed new kelp, urchins stand ready to devour them before they have a chance to grow.

Detailed explanation-2: -When kelp is abundant and underwater forests are rich with nutrients and sea-life, urchins most often dwell in crevices, mainly eating loose bits of kelp that drift within their reach. In fact the only reason these animals venture out of their favored hiding places is if food becomes scarce.

Detailed explanation-3: -Sea urchins use their sensory tube feet to catch drifting kelp and carry it to its mouth on the underside. Its five-part jaw efficiently cuts off pieces to eat.

Detailed explanation-4: -These animals feed on the holdfasts that keep kelp anchored to the bottom of the ocean and algae that are abundant in kelp forests. Sea urchins will often completely remove kelp plants by eating through their holdfasts.

Detailed explanation-5: -Sea urchins feed upon kelp and often eat the stems of the plant found near the rocky ocean floor. This effectively kills the entire kelp plant. It is often sea otter predation on the sea urchins that keeps sea urchin populations in check and preserves the kelp forests.