The main function of the phorphyrin pigment present in earthworms is to provide protection from the adverse effects of the sun.

Protection from Adverse Effects of the Sun:

- The phorphyrin pigment acts as a natural sunscreen for the earthworms. It absorbs and dissipates the harmful ultraviolet (UV) radiation from the sun, preventing damage to the worm's tissues and DNA.

- UV radiation can cause various harmful effects such as DNA mutations, cell damage, and even cell death. By absorbing UV radiation, the phorphyrin pigment reduces the amount of radiation that reaches the earthworm's cells, minimizing the risk of these harmful effects.

- Earthworms spend a significant amount of time on the surface of the soil, where they are exposed to sunlight. Without protection, prolonged exposure to UV radiation could be detrimental to their survival and overall health.

- The phorphyrin pigment not only absorbs UV radiation but also helps in dissipating the absorbed energy. This prevents the energy from being converted into heat, which could further damage the worm's tissues.

- In addition to protecting the earthworms from the sun, the phorphyrin pigment may also play a role in regulating their body temperature. By absorbing sunlight, the pigment helps to warm up the earthworm's body, allowing them to maintain their optimal temperature for various physiological processes.

- The presence of the phorphyrin pigment in earthworms is an adaptation that allows them to thrive in their environment. It provides them with the necessary protection to survive and carry out essential functions such as feeding, reproduction, and locomotion.

In conclusion, the main function of the phorphyrin pigment in earthworms is to provide protection from the adverse effects of the sun, primarily by absorbing and dissipating harmful UV radiation. This adaptation allows earthworms to survive and thrive in their environment.