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.

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

That's a good point, Kim! Usually, smaller aquatic worms are able to obtain enough oxygen through their skin because they have a larger surface area relative to their body volume. This allows for sufficient oxygen diffusion to meet their lower activity levels.

However, bigger aquatic worms have a greater mass and require more oxygen to support their higher activity levels. The rate of oxygen absorption through the skin may not be enough to meet this increased demand. As a result, these worms have evolved alternative mechanisms to obtain oxygen more efficiently.

One possible reason for this is that the rate of oxygen diffusion through the skin becomes less efficient as the size of the worm increases. This is because the thickness of the skin increases with the size, limiting the availability of oxygen to reach the inner cells effectively.

To compensate for this limitation, bigger aquatic worms have developed specialized adaptations, such as gills or respiratory structures, that allow for more efficient gas exchange. These adaptations provide a larger surface area for oxygen absorption and a higher capacity to transport oxygen to the cells throughout the worm's body.

By evolving these additional respiratory structures, bigger aquatic worms can support their larger size and higher activity levels by obtaining oxygen more effectively, ensuring their survival in their respective environments.