Patella pellucida "Fucus serratus" on the lower shore, down to about 30 m. The larvae of this limpet species settle and metamorphose on the algal frond. Here it feeds on its host’s tissue using its radula, leaving small depressions in the frond. As the limpets grow larger, they move down the stipe of the seaweed towards the holdfast, where they establish themselves by excavating a depression. This can weaken the holdfast, eventually resulting in the seaweed being dislodged by storms. The seaweed is often washed ashore, with the blue-rayed limpets still in place. Patella pellucida Patella pellucida, common name the blue-rayed limpet,
Composition of the human body Not all elements which are found in the human body in trace quantities play a role in life. Some of these elements are thought to be simple bystander contaminants without function (examples: caesium, titanium), while many others are thought to be active toxics, depending on amount (cadmium, mercury, radioactives). The possible utility and toxicity of a few elements at levels normally found in the body (aluminium) is debated. Functions have been proposed for trace amounts of cadmium and lead, although these are almost certainly toxic in amounts very much larger than normally found in the body. There is evidence that