Colour vision in sengis (Macroscelidea, Afrotheria, Mammalia): choice experiments indicate dichromatism

摘要

Little research has been conducted on the senses of sengis (elephant-shrews, Macroscelidea, Afrotheria, Mammalia); behavioural investigations about the animals' vision are completely missing. Other Afrotheria (manatees, elephants, ten recs, rock hyraxes) are dichmmats, having two types of cone photoreceptors in the retina. We tested the hypotheses of dichromatic colour vision in sengis. With choice experiments, we examined the potential of two sengi species to discriminate between trained colours (blue, green, red) and different shades of grey, and to differentiate between trained UV-reflecting (high UV reflectance) and UV-absorbing (low UV reflectance) plates. Both sengi species recognised blue and green and could distinguish them from all shades of grey. The ability to perceive red and ultraviolet could not be proven. Thus, the sengis are most likely dichromats based on green and blue sensitive receptor types. We discuss protective mechanisms in the lens as a UV filter explaining maximum sensitivity in the UV suggested for another sengi species after in vitro expression assays.