School of Animal Biology, University of Western Australia, Crawley, WA 6009, Australia.
J Comp Neurol. 2012 Apr 15;520(6):1246-61. doi: 10.1002/cne.22784.
Sea snakes have evolved numerous anatomical, physiological, and behavioral adaptations to suit their wholly aquatic lifestyle. However, although sea snakes use vision for foraging and mate selection, little is known about their visual abilities. We used microspectrophotometry, light microscopy, and scanning electron microscopy to characterize the retinal photoreceptors of spine-bellied (Lapemis curtus) and horned (Acalyptophis peronii) sea snakes. Both species have three types of visual pigment sensitive to short (SWS; wavelength of maximum absorbance, λmax 428-430 nm), medium (MWS; λmax 496 nm), and long wavelengths of light (LWS; λmax 555-559 nm) in each of three different subtypes of cone-like single photoreceptor. They also possess a cone-like double photoreceptor subtype, both the principal and accessory member of which contain the LWS visual pigment. Conventional rods were not observed, although the MWS photoreceptor may be a "transmuted" rod. We also used stereology to measure the total number and topographic distribution of neurons in the ganglion cell layer of L. curtus, the olive sea snake (Aipysurus laevis), and the olive-headed sea snake (Disteira major). All species have a horizontal visual streak with specialized areas in the nasal and temporal retina. Both L. curtus and D. major also have a specialized area in the ventral retina, which may reflect differences in habitat usage and/or foraging behavior compared to A. laevis. Maximal spatial resolution was estimated at 1.1, 1.6, and 2.3 cycles deg⁻¹ in D. major, L. curtus, and A. laevis, respectively; the superior value for A. laevis may reflect its specialized crevice-foraging hunting technique.
海蛇已经进化出许多解剖学、生理学和行为适应性，以适应其完全水生的生活方式。然而，尽管海蛇在觅食和选择配偶时使用视觉，但对它们的视觉能力知之甚少。我们使用微分光光度法、光镜和扫描电子显微镜来描述刺腹海蛇（Lapemis curtus）和角海蛇（Acalyptophis peronii）的视网膜光感受器。这两个物种都有三种类型的视觉色素，对短（SWS；最大吸收波长，λmax 428-430nm）、中（MWS；λmax 496nm）和长波长的光（LWS；λmax 555-559nm）敏感，每种类型都有三种不同的锥状单光感受器亚型。它们还具有一种锥状双光感受器亚型，主感受器和辅助感受器都含有 LWS 视觉色素。虽然没有观察到常规的棒状细胞，但 MWS 光感受器可能是一种“转化”的棒状细胞。我们还使用体视学来测量刺腹海蛇、橄榄海蛇（Aipysurus laevis）和大头海蛇（Disteira major）的神经节细胞层中的神经元总数和拓扑分布。所有物种的水平视觉条纹都有专门的鼻侧和颞侧视网膜区域。刺腹海蛇和大头海蛇在腹侧视网膜也有一个专门的区域，这可能反映了与橄榄海蛇相比，它们在栖息地利用和/或觅食行为上的差异。大头海蛇、刺腹海蛇和橄榄海蛇的最大空间分辨率分别估计为 1.1、1.6 和 2.3 个周期 deg⁻¹；橄榄海蛇的较高值可能反映了其专门的缝隙觅食狩猎技术。
