In some parts of the world bigger aquatic worms exist. These worms do not gain all of their oxygen through their skin. Suggest a reason for this.

Question

Thanx kim xxx

Big suggests a higher activity level, so perhaps the rate of oxygen absorbtion through the skin cannot support the higher level of activity.

Exactly, transpiration is inefficent, only a certan thickness (mass/skin aerea) of creature can be supported by it