Non visual discrimination of shapes in the blind cave cyprinid Phreatichthys andruzzii Vinciguerra 1924

Vision is precluded in the darkness of hypogean environment, which is the reason why cave fish have to direct their locomotor activity using information only acquired through alternative sensory channels. The aim of the present study was to evaluate whether the presence of an object or its morphological features can be used as landmark in orienting the swimming activity of the blind cave cyprinid Phreatichthys andruzzii Vinciguerra 1924. We could verify, by means of a food conditioning procedure, that Phreatichthys is capable of (a) recognising and memorising the presence/absence of an object, (b) discriminating between different shapes and (c) utilising such an information to orient its locomotion in space. The results of our tests show that morphological cues can act as landmarks for Phreatichthys, thus supporting the hypothesis that an orienting mechanism based on such type of information can operate in the permanent darkness of cave habitats.