During mating rituals, mantis shrimp actively fluoresce, and the wavelength of this fluorescence was shown to match the wavelengths detected by their eye pigments . Females are only fertile during certain phases of the tidal cycle; the ability to perceive the phase of the moon may therefore help prevent wasted mating efforts. It may also give mantis shrimp information about the size of the tide, which is important for species living in shallow water near the shore. Mantis shrimp appear to be highly intelligent, are long-lived and exhibit complex behaviour, such as ritualised fighting. In a lifetime, they can have as many as 20 or 30 breeding episodes. In the monogamous species, the mantis shrimp remain with the same partner for up to 20 years.