Encephalic photoreception and phototactic response in the troglobiont Somalian blind cavefish Phreatichthys andruzzii.

Many physiological and behavioural responses to changes in environmental lighting conditions are mediated by extraocular photoreceptors. Here we investigate encephalic photoreception in Phreatichthys andruzzii, a typical cave-dwelling fish showing an extreme phenotype with complete anophthalmy and a reduction in size of associated brain structures. We firstly identified two P.

A blind circadian clock in cavefish reveals that opsins mediate peripheral clock photoreception.

The circadian clock is synchronized with the day-night cycle primarily by light. Fish represent fascinating models for deciphering the light input pathway to the vertebrate clock since fish cell clocks are regulated by direct light exposure. Here we have performed a comparative, functional analysis of the circadian clock involving the zebrafish that is normally exposed to the day-night cycle and a cavefish species that has evolved in perpetual darkness.

Ultrastructure and distribution of superficial neuromasts of blind cavefish, Phreatichthys andruzzii, juveniles.

Transmission and scanning electron microscopy (TEM, SEM) were used to study the ultrastructure of superficial neuromasts in 15 six-month old blind cavefish juveniles, Phreatichthys andruzzii (Cyprinidae). In five specimens examined with SEM, the number of superficial neuromasts over the fish body (480-538) was recorded. They were localized mainly on the head (362-410), including the dorsal surface, the mentomandibular region, and laterally from the mouth to the posterior edge of the operculum.

The lateral line system in larvae of the blind cyprinid cavefish, Phreatichthys andruzzii.

Scanning and transmission electron microscopic observations were made on the anterior and posterior lateral line system of larvae of the blind cavefish, Phreatichthys andruzzii. The investigations were conducted on 36 specimens belonging to three different ages of juvenile: 7, 14, and 28 days posthatching. The basic sensory unit of the mechanoreceptive system is a superficial "neuromast," which is composed of sensory hair cells (HCs) embedded in nonsensory support cells (SCs) frequently covered with a cupula.