UV responses in the retina of the turtle

Abstract

To study processing of UV stimuli in the retina of the turtle, Trachemys dorbignii, we recorded intracellular responses to spectral light from 89 cells: 54 horizontal (47 monophasic, five (R/G) biphasic and two (Y/B) triphasic), 14 bipolar, 12 amacrine, and nine ganglion cells. Spectral sensitivities were measured with monochromatic flashes or with the dynamic constant response method in dark or chromatic adapted states. Stray light and second-order harmonics were also measured. (1) All cells responded to UV stimuli, although none had maximum sensitivity in the UV. (2) Most horizontal, bipolar, and amacrine cells had red-peaked spectral sensitivities. (3) Red adaptation of all monophasic horizontal cells indicated a single red input, except one that had additional peaks in the blue and UV. (4) Responses of biphasic and triphasic horizontal cells to UV light were always hyperpolarizing. Opposition between hyperpolarizing and depolarizing responses at long wavelengths indicates that UV responses were not due to the beta band of red receptors. (5) An unstained spectrally opponent bipolar cell hyperpolarized in the center to green light and antagonistically depolarized in the surround to UV, blue, and green flashes, but hyperpolarized to red. (6) All dark-adapted amacrine cells were red-peaked monophasic cells, but red adaptation broadened their spectral-sensitivity curves or displaced their peaks. An A15, an A18, and an A24 wide-field amacrine cell were stained. (7) A G15 bistratified ganglion cell is shown here for the first time to be spectrally opponent. This UVB/RG cell depolarized to UV and blue and hyperpolarized to red and green. It differs from previously reported turtle ganglion cells in being color opponent in the entire field, not only in the surround, and in showing spatial opponency.

Pharmacological evidence is consistent with a prominent role of spatial memory in complex navigation

“…Indeed, there are certain aspects of motivation and perception that are difficult, if not impossible, to control, particularly under natural conditions in the field. Nevertheless, given the similarity in behaviour between juveniles and adults in this study and our previous work [22,23], the body of work on sensory reception in this species [22][23][24][25][26][27][28][29][30], and the previous literature demonstrating the effects of mAChR-blocking drugs on cognition in this and other species [31,32,[41][42][43], we find it unlikely that an age-by-scopolamine interaction underlies the observed pattern of behaviour, yet remain open to the possibility that such a complex interaction exists.…”

“…The precision of the routes suggests that turtles use a fine-scale, ground-based cue when learning to navigate [22,23]. Although the information used to learn navigation routes is probably multimodal, previous studies in reptiles suggest vision or olfaction as possibilities [24][25][26][27][28][29][30], and our own work suggests that aspects of UV vision might facilitate learning the navigational routes [22].…”

“…The vast majority of sensory studies are conducted on adults (e.g. [24,25,29,31,32,35,37]) including studies of UV vision [27,28,47], suggesting that adults can indeed detect the cues probably important for juvenile navigation.…”

Spectral Responses in Zebrafish Horizontal Cells Include a Tetraphasic Response and a Novel UV-Dominated Triphasic Response

“…In turtle, all horizontal cells are hyperpolarized by UV light stimulation (Ammermuller et al 1998;Ventura et al 1999), but only the triphasic cells receive direct UV cone excitation Zana et al 2001). In fish, triphasic horizontal cells also receive inputs from UV cones (Hashimoto et al 1988), and, in some species of cyprinids, a tetraphasic response-hyperpolarized to red, depolarized to green, hyperpolarized to blue, depolarized to UV-has been reported (De Aguiar et al 2006;Fukurotani and Hashimoto 1984;Harosi and Fukurotani 1986;Hashimoto et al 1988).…”

Ultraviolet vision in lacertid lizards: evidence from retinal structure, eye transmittance, SWS1 visual pigment genes, and behaviour

“…Carleton et al, 2000;Siebeck and Marshall, 2001;Siebeck and Marshall, 2007;Siebeck et al, 2010), data on other vertebrate linages are relatively scant and encompass few species [e.g. amphibians (Govardovskiĭ and Zueva, 1974;Perry and McNaughton, 1991;Takahashi and Yokoyama, 2005), mammals (Jacobs et al, 1991;Winter et al, 2003;Wang et al, 2004;Palacios et al, 2010;Carvalho et al, 2012), turtles (Ventura et al, 1999;Loew and Govardovskiĭ, 2001), crocodiles (Sillman et al, 1991) and Squamata, i.e. lizards and snakes (Fleishman et al, 1997;Fleishman et al, 2011;Sillman et al, 1999;Sillman et al, 2001;Loew et al, 2002)].…”