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The eyes of suckermouth armoured catfish (Loricariidae, subfamily Hypostomus): pupil response, lenticular longitudinal spherical aberration and retinal topography

Ron H. Douglas^1,*, Shaun P. Collin^2,3 and Julie Corrigan¹

¹ Applied Vision Research Centre, Department of Optometry & Visual Science, City University, Northampton Square, London EC1V 0HB, UK
² Department of Anatomy & Developmental Science, School of Biomedical Science, The University of Queensland, Brisbane 4072, Queensland, Australia
³ Anatomisches Institut, Universität Tübingen, Österbergstrasse 3, Tübingen, 72074, Germany

View larger version (21K): [in a new window]   Fig. 1. Pupil response of a Liposarcus pardalis individual during 60 min exposure to different intensities of white light.

View larger version (10K): [in a new window]   Fig. 2. Minimum pupil area in response to different intensities of white light. Corneal irradiance is measured in µW cm-2. The different symbols represent data from three individual Liposarcus pardalis.

View larger version (13K): [in a new window]   Fig. 3. Pupil response of a Liposarcus pardalis individual to 60 min exposure to white light at an intensity of 5.6x103 µW cm-2. The three curves represent normalized lines for area of irideal operculum (squares), pupil area (crosses) and horizontal pupil diameter at its widest point (triangles).

View larger version (101K): [in a new window]   Fig. 4. Infra-red video images of the eye of Liposarcus pardalis (standard length 14 cm) in (A) the absence of any visible light and (B) after 60 min exposure to 5.6x103 µW cm-2 white light. Illumination resulted both in a decrease of pupil diameter and the outgrowth of an iris flap, such that overall pupil area following illumination in this example is 34% of the dark-adapted value. Scale bar, 2 mm.

View larger version (13K): [in a new window]   Fig. 5. Back vertex distance (BVD) as a function of entry position of an He—Ne laser beam into the (A) right (1.65 mmx1.88 mm diameter) and (B) left (1.63 mmx1.85 mm diameter) lens of a Pterygoplichthys etentaculus individual. The triangles represent individual data points, and the solid lines represent fitted non-linear regression lines [(A) x=2.50-0.92y2+0.80y4; (B) x=2.44-0.68y2+0.55y4]. The beam-entry positions have been normalised so that the edges of the lens represent 1 and -1.

View larger version (75K): [in a new window]   Fig. 6. Transverse section of a Liposarcus pardalis retina. The arrow indicates the position of the external limiting membrane. The only photoreceptors seen throughout the retina are large rods and small single cones. Abbreviations: RPE, retinal pigment epithelium; ROS, rod outer segment; RIS, rod inner segment; COS, cone outer segment; CIS, cone inner segment. Scale bar, 50 µm.

View larger version (155K): [in a new window]   Fig. 7. Optic axon fasciculation. Ganglion cell axon fascicles labelled with fluorescein-tagged dextran (A) entering the dorsal region of the optic nerve head and (B) along the embryonic fissure in the retina of Liposarcus multiradiatus. (C) Low- and (D) high-power micrographs of retrogradely labelled ganglion cells lying in between axon fascicles. The embryonic fissure lies to the left in (C). Scale bars, 100 µm.

View larger version (63K): [in a new window]   Fig. 8. Retinal ganglion cell labelling. (A,B) Retrogradely labelled retinal ganglion cells in the relatively high-density regions of the retina in Liposarcus multiradiatus. Note the heterogeneous cell soma size. Scale bars, 50 µm.

View larger version (42K): [in a new window]   Fig. 9. Iso-density contour map of the distribution of retrogradely labelled retinal ganglion cells in the right eye of Liposarcus pardalis (standard length 158 mm). The elongated optic nerve head is depicted in black. All densities are x102 cells mm-2. T, temporal; V, ventral.