The eye of Orchomene sp. cf. O. rossi , an amphipod living under the Ross Ice Shelf (Antarctica)

• Published in: Proceedings of the Royal Society of London. Series B. Biological Sciences
• Format: Article in Journal/Newspaper
• Language: English
• Published: The Royal Society 1981
• Subjects: Ross Ice Shelf; Antarc*; Antarctica; Ice Shelf
• Online Access: http://dx.doi.org/10.1098/rspb.1981.0027; https://royalsocietypublishing.org/doi/pdf/10.1098/rspb.1981.0027

The structural organization of the eye of freshly caught Orchomene sp. cf. O. rossi is described and compared with that of individuals that were exposed to sunlight for 2 h, or were kept in complete darkness for 2 and 7 days. Orchomene sp. cf. O. rossi occurs under the 400 m thick Ross Ice Shelf in water of — 2 °C. Its eyes, containing 360 ommatidia, are relatively large and of orange colour. External facets are not developed, but the dioptric structures, consisting of a cornea 30 μm thick and the bipartite crystalline cones (ca. 65 μm long and 55 μm wide), are transparent and allow one to see the underlying ommatidial organization and retinula. Rhabdoms, comprising rhabdomeres of five retinula cells per omma, are voluminous (up to 50 μm in diameter and 160 μm in length) and surround the proximal ends of the crystalline cones. There are a few black screening pigment granules in the retinula cell plasma, but their number is too small to effectively shield and insulate neighbouring ommatidia from each other. Interstitial cells, containing vesicles of 0.3 μm diameter, occupy the spaces between adjacent ommatidial groups of retinula cells, but do not extend into the layer of retinula cell nuclei. Based on the anatomy, the eye of Orchomene sp. cf. O. rossi seems to be adapted to maximize photon capture at the expense of acuity.