Specialized cells that detect and transduce light. They are classified into two types
based on their light reception structure, the ciliary photoreceptors and the rhabdomeric
photoreceptors with MICROVILLI. Ciliary photoreceptor cells use OPSINS that activate
a PHOSPHODIESTERASE phosphodiesterase cascade. Rhabdomeric photoreceptor cells use
opsins that activate a PHOSPHOLIPASE C cascade