Ocular Morphology of the Japanese Special Natural Monument, the Amami Rabbit (Pentalagus furnessi), an Endemic Species in Amami Oshima

Pentalagus furnessi (Amami rabbit) is an endemic rabbit only reside in the southern districts of Japan, and designated as a special natural monument in Japan. While conserving those animals is necessary, basic knowledge regarding their unique features remains unknown. In this study, we analyzed morphological and histological characteristics of the eyes which were obtained from an Amami rabbit died accidentally by a traffic accident. In the Amami rabbit, not tapetum-like structures but both pigmented and non-pigmented areas were observed. In addition, the non-pigmented area was much larger in the Amami rabbit compared to that in the laboratory rabbits (Oryctolagus cuniculus). In the histological analysis, layers of retina were corresponded to the standard vertebrate arrangement, though the sizes of cell nuclei in both the inner and outer granular layers were larger in the Amami rabbit compared to laboratory rabbits. While characteristics of eyes are highly conserved in the family Leporidae, smaller pigmented area in Amami rabbits may reflect the natural selection resulting from their nocturnal lifestyle. Understanding their characteristics further is necessary for conserving the unique and endangered hare in Japan.