Rojas L M, McNeil R, Cabana T, Lachapelle P
Département de sciences biologiques, Université de Montréal, Montréal, Canada.
Brain Behav Evol. 1999 May-Jun;53(5-6):227-42. doi: 10.1159/000006596.
We examined in selected wading bird species if diurnal or nocturnal foraging and the use of visual or tactile feeding strategies could be correlated with retinal structure and function. The selected species were the Yellow-crowned Night Heron (Nycticorax violaceus), a crepuscular and nocturnal forager, the Great Blue Heron (Ardea herodias), a mainly crepuscular, but also diurnal and nocturnal feeder, the Roseate Spoonbill (Ajaia ajaja), a mainly crepuscular feeder which forages more at night than during the day, the Cattle (Bubulcus ibis) and Tricolored (Egretta tricolor) egrets and the American White Ibis (Eudocimus ruber) which forage only during daytime. Herons and egrets are visual foragers; ibises and spoonbills are tactile feeders. Electroretinograms were obtained from anesthetized birds in photopic and scotopic conditions to a wide range of light intensities, following which the retinae were processed for histological analysis. Based on rod densities and rods:cones ratios, nocturnal vision capability is greater in the Yellow-crowned Night Heron, followed by the Great Blue Heron and the spoonbill, then by the egrets and the ibis. Visual feeders that forage near dawn or dusk or at night have a higher rods:cones ratio, and consequently a greater night vision capability, than visual feeding species which forage only during daytime. Visual nocturnal feeders have a night vision capability greater than tactile diurnal as well as tactile nocturnal feeders. However, based on maximum scotopic b-wave amplitudes, all species studied have roughly comparable night vision capability. The factor that best discriminates between wading bird species appears to be the daytime visual capabilities. Indeed, the diurnal ibis and egrets have similar cone densities, cones:rods ratios, and photopic a-wave amplitudes, values which are greater than those measured in the two nocturnally active heron species.
我们研究了特定涉禽物种的昼夜觅食习性以及视觉或触觉觅食策略的运用是否与视网膜结构和功能相关。所选物种包括黄冠夜鹭（Nycticorax violaceus），一种晨昏性和夜行性觅食者；大蓝鹭（Ardea herodias），主要为晨昏性觅食者，但也在白天和夜间觅食；玫瑰琵鹭（Ajaia ajaja），主要是晨昏性觅食者，夜间觅食比白天更多；牛背鹭（Bubulcus ibis）和三色鹭（Egretta tricolor）以及美洲白鹮（Eudocimus ruber），它们仅在白天觅食。鹭类和白鹭是视觉觅食者；鹮类和琵鹭是触觉觅食者。在明视和暗视条件下，对麻醉的鸟类施加一系列光强度后获取视网膜电图，随后对视网膜进行组织学分析。基于视杆细胞密度和视杆细胞与视锥细胞的比例，黄冠夜鹭的夜间视觉能力最强，其次是大蓝鹭和琵鹭，然后是白鹭和鹮。在黎明或黄昏附近或夜间觅食的视觉觅食者比仅在白天觅食的视觉觅食物种具有更高的视杆细胞与视锥细胞比例，因此夜间视觉能力更强。视觉夜行性觅食者的夜间视觉能力比触觉昼行性以及触觉夜行性觅食者更强。然而，基于最大暗视b波振幅，所有研究的物种夜间视觉能力大致相当。最能区分涉禽物种的因素似乎是白天的视觉能力。实际上，昼行性的鹮和白鹭具有相似的视锥细胞密度、视锥细胞与视杆细胞比例以及明视a波振幅，这些值大于在两种夜间活动的鹭类物种中测得的值。
