Abstract
Disoriented human beings and animals, the latter both sighted and blind, are able to use spatial geometric information (metric and sense properties) to guide their reorientation behaviour in a rectangular environment. Here we aimed to investigate reorientation spatial skills in three fish species (Danio rerio, Xenotoca eiseni, Carassius auratus) in an attempt to discover the possible involvement of extra-visual senses during geometric navigation. We observed the fish’s behaviour under different experimental procedures (spontaneous social cued task and rewarded exit task), providing them different temporal opportunities to experience the environmental shape (no experience, short and prolonged experience). Results showed that by using spontaneous social cued memory tasks, fishes were not able to take advantage of extra-visual senses to encode the spatial geometry, neither allowing them short time-periods of environmental exploration. Contrariwise, by using a reference memory procedure, during the rewarded exit tasks, thus providing a prolonged extra-visual experience, fishes solved the geometric task, showing also differences in terms of learning times among species.
Highlights
Disoriented human beings and animals, the latter both sighted and blind, are able to use spatial geometric information to guide their reorientation behaviour in a rectangular environment
The difference among species was due to the high number of choices, for each trial over the five sessions, made by zebrafish (D. rerio), if compared to the other two species (D. rerio: mean ± SEM C-R = 263.5 ± 49.22 and N-F = 260.83 ± 49.66; X. eiseni: C-R = 86.8 ± 10.75 and N-F = 85.8 ± 9.66; C. auratus: C-R = 90 ± 40.67 and N-F = 87.2 ± 39.09)
Since the Species variable was not significant, the Wilcoxon test applied to the overall data could clarify the significant interaction Time x Geometry
Summary
Disoriented human beings and animals, the latter both sighted and blind, are able to use spatial geometric information (metric and sense properties) to guide their reorientation behaviour in a rectangular environment. Results showed that by using spontaneous social cued memory tasks, fishes were not able to take advantage of extra-visual senses to encode the spatial geometry, neither allowing them short time-periods of environmental exploration. The correct solution to this spatial problem involves searching in correspondence of the correct corner and its geometric equivalent diagonally located with respect to the goal. Since these two corners have the same metric and sense characteristics (e.g., a long wall on the right and a short wall on the left), they are indistinguishable. The morphological patterns of the lateral line systems and the number of neuromasts differ among fish species and probably represent an adaptation to various hydrodynamic environments[23,31,32]
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