Hart Nathan S
Vision, Touch and Hearing Research Centre, School of Biomedical Sciences, University of Queensland, Brisbane, Queensland 4072, Australia.
J Exp Biol. 2004 Mar;207(Pt 7):1229-40. doi: 10.1242/jeb.00857.
Microspectrophotometric examination of the retina of a procellariiform marine bird, the wedge-tailed shearwater Puffinus pacificus, revealed the presence of five different types of vitamin A(1)-based visual pigment in seven different types of photoreceptor. A single class of rod contained a medium-wavelength sensitive visual pigment with a wavelength of maximum absorbance (lambda(max)) at 502 nm. Four different types of single cone contained visual pigments maximally sensitive in either the violet (VS, lambda(max) 406 nm), short (SWS, lambda(max) 450 nm), medium (MWS, lambda(max) 503 nm) or long (LWS, lambda(max) 566 nm) spectral ranges. In the peripheral retina, the SWS, MWS and LWS single cones contained pigmented oil droplets in their inner segments with cut-off wavelengths (lambda(cut)) at 445 (C-type), 506 (Y-type) and 562 nm (R-type), respectively. The VS visual pigment was paired with a transparent (T-type) oil droplet that displayed no significant absorption above at least 370 nm. Both the principal and accessory members of the double cone pair contained the same 566 nm lambda(max) visual pigment as the LWS single cones but only the principal member contained an oil droplet, which had a lambda(cut) at 413 nm. The retina had a horizontal band or 'visual streak' of increased photoreceptor density running across the retina approximately 1.5 mm dorsal to the top of the pecten. Cones in the centre of the horizontal streak were smaller and had oil droplets that were either transparent/colourless or much less pigmented than at the periphery. It is proposed that the reduction in cone oil droplet pigmentation in retinal areas associated with high visual acuity is an adaptation to compensate for the reduced photon capture ability of the narrower photoreceptors found there. Measurements of the spectral transmittance of the ocular media reveal that wavelengths down to at least 300 nm would be transmitted to the retina.
对一种鹱形目海鸟——楔尾鹱（Puffinus pacificus）的视网膜进行显微分光光度检查发现，在七种不同类型的光感受器中存在五种不同类型的基于维生素A（1）的视觉色素。一类视杆细胞含有一种中波敏感视觉色素，其最大吸收波长（λmax）为502纳米。四种不同类型的单锥细胞含有在紫光（VS，λmax 406纳米）、短波（SWS，λmax 450纳米）、中波（MWS，λmax 503纳米）或长波（LWS，λmax 566纳米）光谱范围内具有最大敏感性的视觉色素。在周边视网膜中，SWS、MWS和LWS单锥细胞在其内部节段含有色素油滴，其截止波长（λcut）分别为445（C型）、506（Y型）和562纳米（R型）。VS视觉色素与一个透明（T型）油滴配对，该油滴在至少370纳米以上没有明显吸收。双锥细胞对的主细胞和辅助细胞都含有与LWS单锥细胞相同的λmax为566纳米的视觉色素，但只有主细胞含有一个油滴，其λcut为413纳米。视网膜有一条水平带或“视觉条纹”，光感受器密度增加，横跨视网膜，位于栉膜顶部背侧约1.5毫米处。水平条纹中心的锥细胞较小，其油滴要么是透明/无色的，要么色素比周边少得多。有人提出，与高视力相关的视网膜区域中锥细胞油滴色素沉着的减少是一种适应性变化，以补偿该区域中较窄光感受器降低的光子捕获能力。眼介质光谱透射率的测量表明，至少300纳米的波长会传输到视网膜。
