Eguchi E, Dezawa M, Meyer-Rochow V B
Biol Bull. 1997 Apr;192(2):300-308. doi: 10.2307/1542723.
Fully grown, unsexed specimens of the anomuran half-crab Paralomis multispina Benedict were obtained from a depth of 1200 m, and the eyes of three individuals were prepared for light and electron microscopy. In their outer appearance the compound eyes of Paralomis resemble those of common shallow-water half-crabs (e.g., Petrolisthes), but facets in Paralomis were about 3 times larger in diameter (i.e., 60 {mu}m) and at least twice as long. Interommatidial angles ranged from 3{deg} to 5{deg}. The proximal width of the crystalline cone in Paralomis was 10 times that of its equivalent in the Petrolisthes eye, and the rhabdom--although only twice as long--had a radius that was 7 times greater distally and 4 times greater proximally. A clear-zone between cones and rhabdom was not developed, and cross sections of crystalline cones revealed rounded rather than square profiles. A distal retinula cell (R8) was absent, and all regular retinula cells (R1-R7) protruded microvilli of about 0.11 {mu}m diameter in many (and not only two) directions. A maximum rhabdom occupation ratio of 85% was found in the Paralomis retinula, whereas in the shallow-water half-crabs the comparable figure was 35%. Paralomis featured a wide, rhabdomless space between basement membrane and proximal rhabdom ends; the space was occupied by reflecting cells. Primary screening pigment cells and their dark granules were present; secondary screening pigment cells, however, were replaced by reflecting cells. The anatomical modifications in the Paralomis eye are consistent with habitat-related adaptations seen in the eyes of other benthic and slow-moving deep-water crustaceans, but not with those of euphausiids. We conclude that the eye of Paralomis functions as an apposition eye, designed to maximize photon capture, especially from point sources (i.e., bioluminescence) rather than extended sources. We estimate that the Paralomis eye is at least 150 times more sensitive to light than the eye of shallow-water Petrolisthes.
从1200米深处采集到了成年的、未区分性别的异尾类半蟹多刺拟石蟹标本，并对三只个体的眼睛进行了光学显微镜和电子显微镜观察准备。多刺拟石蟹的复眼外观与常见的浅水半蟹（如岩瓷蟹属）相似，但多刺拟石蟹的小眼直径约为其3倍（即60微米），长度至少为其2倍。小眼间角度在3°至5°之间。多刺拟石蟹晶状体圆锥体的近端宽度是岩瓷蟹属眼睛中相应部分的10倍，视杆——尽管长度仅为其2倍——其远端半径大7倍，近端半径大4倍。圆锥体和视杆之间未形成透明区，晶状体圆锥体的横截面显示为圆形而非方形。没有远端小网膜细胞（R8），所有规则的小网膜细胞（R1 - R7）在许多（而非仅两个）方向上伸出直径约0.11微米的微绒毛。在多刺拟石蟹的小网膜中发现视杆占据率最高为85%，而在浅水半蟹中这一可比数字为35%。多刺拟石蟹在基底膜和近端视杆末端之间有一个宽阔的、无视杆的空间；该空间被反光细胞占据。存在初级遮光色素细胞及其深色颗粒；然而，次级遮光色素细胞被反光细胞取代。多刺拟石蟹眼睛的解剖学变化与其他底栖和行动缓慢的深水甲壳类动物眼睛中所见的与栖息地相关的适应性一致，但与磷虾的不同。我们得出结论，多刺拟石蟹的眼睛作为并列像眼发挥作用，旨在最大限度地捕获光子，尤其是来自点光源（即生物发光）而非扩展光源的光子。我们估计，多刺拟石蟹的眼睛对光的敏感度至少是浅水岩瓷蟹眼睛的150倍。
