Morphology and Response to Light Ofbarbopsis Devecchiidi Caporiacco (Cyprinidae), Microphthalmic Phreatic Fish From Somalia

SUMMARY Barbopsis devecchii Di Caporiacco, microphthalmia phreatic fish from Somalia, has markedly reduced optic lobes in comparison to a systematically close epigean species with normally developed eyes (Barbus macrolepidotus Cuvier & Valenciennes). Chiasma, optic nerves and retina are always found. Slightly microphthalmic fish show the typical retinal layers and have both cones and rods. In extremely microphthalmic fish, the typical retinal layers are not always recognizable. In response to achromatic light, Barbopsis accustomed to complete darkness proved to be totally photophobic while those accustomed to a periodic cycle proved to be substantially photoindifferent. In response to four wavelengths of monochromatic light, Barbopsis accustomed to periodic cycle with shadow zones in the aquarium proved to be completely photophobic.