November 1999
Volume 40, Issue 12
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Physiology and Pharmacology  |   November 1999
Effects of Abnormal Light-rearing Conditions on Retinal Physiology in Larvae Zebrafish
Author Affiliations
  • Shannon Saszik
    From the Department of Psychology, Western Kentucky University, Bowling Green; and
    College of Optometry, University of Houston, Texas.
  • Joseph Bilotta
    From the Department of Psychology, Western Kentucky University, Bowling Green; and
Investigative Ophthalmology & Visual Science November 1999, Vol.40, 3026-3031. doi:
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      Shannon Saszik, Joseph Bilotta; Effects of Abnormal Light-rearing Conditions on Retinal Physiology in Larvae Zebrafish. Invest. Ophthalmol. Vis. Sci. 1999;40(12):3026-3031.

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Abstract

purpose. Anatomic studies have found that zebrafish retinal neurons develop in a sequential fashion. In addition, exposure to abnormal light-rearing conditions produces deficits in visual behavior of larvae zebrafish, even though there appears to be little effect of the light-rearing conditions on the gross morphology of the retina. The purpose of this study was to assess the effects of abnormal light-rearing conditions on larvae zebrafish retinal physiology.

methods. Larvae zebrafish (Danio rerio) were exposed to constant light (LL), constant dark (DD), or normal cyclic light (LD) from fertilization to 6 days postfertilization (dpf). After 6 days, the animals were placed into normal cyclic light and tested at 6 to 8, 13 to 15, and 21 to 24 dpf. Electroretinogram (ERG) responses to visual stimuli, consisting of various wavelengths and irradiances, were recorded. Comparisons were made across the three age groups and the three light-rearing conditions.

results. Deficits from the light-rearing conditions were seen immediately after exposure (6–8 dpf). The LL-condition subjects showed the greatest deficit in the UV and short-wavelength areas and the DD-condition subjects showed a slight deficit across the entire spectrum. At 13 to 15 dpf, the LL and DD groups showed an increase in sensitivity and by 21 to 24 dpf, the groups no longer differed from controls.

conclusions. Abnormal lighting environments can adversely influence the physiological development of the larvae zebrafish retina. The pattern of damage that was seen in zebrafish is similar to that found in other vertebrates, including higher vertebrates. However, unlike higher vertebrates, the zebrafish appears to be capable of regeneration. This suggests that the zebrafish would be a viable model for light environment effects and neural regeneration.

In both lower and higher vertebrates there are many examples of the effects of abnormal light environments on the retina. For example, Harwerth and Sperling 1 found a decrease in the sensitivity of M-cones and L-cones when adult primates were exposed to middle- and long-wavelength light, although the damage did not appear to be permanent. However, they also found that the S-cones showed a permanent decrease in sensitivity after exposure to short-wavelength light. Interestingly, when monkeys were raised in constant dark for up to 2 months, no anatomic differences were found at the retinal level or the dorsal lateral geniculate nucleus. 2  
The effects of different light-rearing environments on developing zebrafish have been assessed using behavioral and anatomic methods. Studies using pigmented zebrafish found no differences in retinal anatomy, including outer segment size and retinal layer lamination, among subjects raised in constant light, 3 constant dark, 3 4 and normal cyclic light. However, the anatomic work does not agree with behavioral data from zebrafish raised under similar lighting conditions. Larvae zebrafish exposed to constant light from fertilization to 6 days postfertilization (dpf) had a visual acuity below that of constant dark and normal subjects when measured using the optomotor response 5 ; however, zebrafish raised from fertilization to 6 dpf in constant dark had only a slight deficit in acuity compared to normal subjects. 
The purpose of the present study was to examine light-rearing effects on visual physiology, as measured with the electroretinogram (ERG). This study used light-rearing conditions similar to those used in the previously mentioned anatomic 3 and behavioral 5 studies. It was hypothesized that animals reared in constant light would show deficits in sensitivity in the UV and short-wavelength areas of the spectrum. Zebrafish S-cones are similar qualitatively in structure to the S-cones in primates, and primate S-cones appear to be the most susceptible to light damage. 1 Also, studies with other fish species have shown that the U-cones are very susceptible to environmental factors. 6 Finally, it is anticipated that animals reared in constant dark should show some visual deficits, but these should not be as severe as those for animals reared in constant light. 
Methods
Participants
Larvae zebrafish (Danio rerio), bred in-house, 7 were maintained until 6 dpf in one of three light-rearing conditions: constant light (LL), constant dark (DD), or a 14-hour lights on–10-hour lights off cycle (LD). Light levels in LL and LD conditions were approximately 500 lux (F40/D fluorescent lights; Sylvania, Danvers, MA). These conditions correspond to those used in past work that showed differences in visual behavior. 5 All procedures were in accordance with the ARVO Statement for the Use of Animals in Ophthalmic and Vision Research. 
Apparatus
A two-channel optical system was used to present the visual stimuli (see Ref. 8) . Monochromatic light was presented to the subjects through one channel, which had a 150 W xenon arc lamp as its light source (model LH 150; Spectral Energy, Westwood, NJ). The second channel had a 250 W tungsten-halogen bulb (model 6334; Oriel, Stratford, CT) light source that provided a 5μ W/cm2 broadband background. The two channels were combined optically and focused onto one end of a liquid light guide (model 77556; Oriel); the other end was placed in front of the subject’s eye. Stimulus wavelength and irradiance were controlled using interference and neutral density filters. 
Testing Procedures
Testing began on day 6 when the fish were removed from the light-rearing environment. Detailed procedures have been described elsewhere. 9 Briefly, the subject was anesthetized with tricaine methanesulfonate; the dose (0.01%, 0.02%, or 0.04%) varied according to age (6–8, 13–15, and 21–24 dpf, respectively). The subject was placed on a piece of cotton in a Petri dish; the cotton was moistened with an anesthetic solution. The recording and reference electrodes, glass pipettes with a 10-μm tip diameter, were filled with teleost saline solution and housed 36-gauge chlorided silver wires. The recording electrode was placed on the subject’s eye, and the reference electrode was placed on the body. For the 21 to 24 dpf group, the recording electrode was inserted into the vitreal chamber. This was done to make the procedures of this age group more comparable to previously published adult data. 8 Electrical signals were differentially amplified (AC amplifier with a bandpass of 0.1–100 Hz) and recorded by the laboratory computer at a rate of 250 Hz. The animal adapted to the broadband background for 5 minutes before trials began. The irradiance at any given wavelength began below threshold and was increased until the desired response was obtained. Each trial consisted of three 200-ms stimulus presentations. The order of wavelength presentation was staggered in 40-nm steps; the remaining wavelengths were then filled in, such that 20-nm steps existed in the final set of data. 
Results
ERG waveforms were digitally filtered for 60-Hz noise and averaged across the three stimulus presentations. 8 Spectral sensitivity functions were calculated for both the a- and b-wave ERG components when they were apparent. Spectral sensitivities of the 6 to 8 dpf subjects from the LD, DD, and LL conditions were calculated using the a-wave component from responses to 320- to 440-nm stimuli; after 440 nm, the a-wave was no longer evident in the subjects’ waveforms. 9 The a-wave was measured from baseline (response before stimulus onset) to the first negative peak. For the b-wave component, spectral sensitivity was calculated from 320 to 640 nm for all age groups and all conditions. The b-wave was measured from baseline or the first negative peak to the first positive peak. There were no apparent differences in the subjects’ ERG waveforms across all rearing conditions, including normal subjects (LD). The young subjects’ ERG waveforms had strong a- and b-waves in response to UV stimuli, as opposed to being dominated by the b- and d-waves as found in adult responses across wavelengths. 8 9 To obtain sensitivity to each stimulus wavelength, the reciprocal of the log stimulus irradiance (quanta s−1 cm−2), which produced a criterion response, was calculated from the log irradiance-response function. 9  
To make comparisons across the lighting conditions, the data were first normalized to values at 640 nm. This is because, based on previous research, it was hypothesized that the deficits due to light-rearing conditions would be found in the UV and short-wavelength areas of the spectrum. Thus, normalizing the data to the peak in the UV area, which is where larvae zebrafish are normally most sensitive, 9 would be inappropriate because that is where the deficits were expected. The decision to normalize the curves at the long wavelengths was supported empirically by attempting to normalize the functions at other parts of the spectrum. For example, normalizing at the UV wavelengths (which was the most sensitive portion of all the functions) gave the impression that the 6 to 8 dpf subjects in the three rearing conditions were identical in sensitivity to UV wavelengths and that the LL group was more sensitive to middle and long wavelength stimuli when compared to normal subjects. This interpretation is inconsistent with normal zebrafish ERG development. 9 Therefore, the data were normalized to values at 640 nm. The data were renormalized to the peak sensitivity of the LD-condition subjects for each age group. Normalizing the data to the peak sensitivity of the LD-condition subjects was done so the sensitivity of the DD- and LL-condition functions could be compared, relative to the normal LD-condition function. After calculating the relative spectral sensitivities for the three conditions and the three age groups, a quantitative assessment of the cone contributions to the spectral sensitivity function was performed. A multiple mechanism model was used to derive the cone inputs (λmax = 362, 415, 480, and 570 nm; U-, S-, M-, and L-cones, respectively 10 ) to the spectral sensitivity data (see Ref. 8 for details). 
Figure 1 shows the spectral sensitivity functions of the 6 to 8 dpf subjects from the LD (squares), DD (circles), and LL (triangles) conditions. The lines represent the best-fit models and the error bars indicate ±1 SEM. As expected, compared to the LD-condition subjects, the LL-condition subjects showed the greatest deficit in sensitivity, especially to UV and short-wavelength stimuli. There were differences between the LL- and the LD-condition subjects in the middle- and long-wavelength areas, but they were relatively small. The subjects in the DD condition also showed a deficit in sensitivity when compared to the LD-condition subjects, but it was not as large as the deficit of the LL-condition subjects. Unlike the LL-condition function, there was a uniform sensitivity deficit of a half log unit in DD-condition subjects’ relative sensitivity compared to the sensitivity of the LD-condition subjects. Figure 2 A shows the spectral sensitivity of the 13 to 15 dpf subjects from the LD (squares), DD (circles), and LL (triangles) conditions. In general, all three spectral sensitivities are similar in shape. At this age, the difference in the spectral sensitivities that was apparent in the 6 to 8 dpf subjects has disappeared. Interestingly, there are no sensitivity differences for the three groups in the UV area. The LL- and the DD-condition subjects appear to show only a slight deficit in sensitivity to the short- and middle-wavelength areas of the spectrum when compared to the LD-condition subjects. Figure 2B shows the spectral sensitivity functions of the 21 to 24 dpf subjects in the LD (squares), DD (circles), and LL (triangles) conditions. The damage seen initially in the 6 to 8 dpf subjects raised in the LL and DD conditions gradually disappeared and by 24 dpf, the sensitivity of the LL- and DD-condition subjects returned to normal. 
To assess whether photoreceptor function was responsible for the differences seen in the LD, LL, and DD conditions, a-wave spectral sensitivity functions were calculated. Figure 3 A shows the spectral sensitivity functions of the a-wave component of the ERG response from 6 to 8 dpf subjects in the LD (squares), DD (circles), and LL (triangles) conditions. The data are shown in absolute sensitivity values (quanta s−1 cm−2). The curves from the three groups are very similar in shape and absolute sensitivity. There do not appear to be any differences in the a-wave spectral sensitivity functions of the 6 to 8 dpf subjects exposed to the LL and DD conditions when compared to the LD condition, suggesting no problems with photoreceptor function. 
Because the functions across the three conditions were similar, the data were averaged and modeled. In Figure 3B , the points represent the data and the line represents the model. Because the spectrum range was limited to primarily UV wavelengths, only the U-cone spectra were used in the model. There appears to be a good fit between the model and the data, suggesting that this spectral sensitivity function reflects U-cone activity in the retina. Because the function is derived from the a-wave component of the ERG response, it suggests normal U-cone function. 
Discussion
The main objective of the present study was to examine the effects of abnormal light-rearing conditions on early retinal development. On the basis of work done in primates, 1 it was anticipated that after exposure to constant light, there would be deficits in the UV and short-wavelength areas of the spectrum. Also, subjects exposed to constant dark conditions were expected to show some deficits, but these deficits would not be as severe as those observed in the constant light condition and would not be limited to the UV and short-wavelength areas. 
The immature system of the larvae zebrafish appears to be affected by abnormal light-rearing environments. The abnormal conditions (LL and DD) used in this study altered the b-wave spectral sensitivity of subjects compared to those raised in normal cyclic light. These physiological deficits are similar to the behavioral deficits that have been reported, 5 even though anatomic studies report no gross deficits. 3 4 The discrepancy between approaches may be explained by possible anatomic deficits that may be located only in the synaptic connections between the cells. 
The only differences seen in the b-wave spectral sensitivity functions across the conditions were immediately after exposure (6–8 dpf). In the UV and short-wavelength areas of the spectrum, subjects in both LL and DD conditions showed deficits in sensitivity, suggesting problems with the U- and S-cones and/or their connections. In the UV and short-wavelength areas of the spectrum, both the LL and the DD subjects were found to have lower sensitivity when compared to normal subjects of the same age. However, subjects raised in constant light showed the greatest deficit in sensitivity, and the constant dark subjects’ sensitivity fell between that of the LL and LD subjects. 
These findings are consistent with those reported in primates, 1 where subjects raised in constant light displayed a large deficit in sensitivity to short-wavelength stimuli. As expected, the results show that the U- and S-cones’ contribution to the b-wave response are more susceptible to light damage than the other cone types. Interestingly, there was no difference in a-wave spectral sensitivity at the UV wavelengths. This suggests there is no problem with the U-cones, and the functional deficits found must be the result of either direct damage to the bipolar cells or damage to the synaptic connections between the U-cones and bipolar cells. At the middle- and long-wavelength areas of the spectrum, the deficits seen in the b-wave responses of subjects across the two conditions were similar. Subjects from both abnormal light-rearing conditions showed deficits in sensitivity, although the deficits in the middle- and long-wavelength areas of the spectrum were not as severe as those in the UV area of the spectrum. These findings also support studies of other fish species that have shown the U-cones to be labile and susceptible to environmental factors. For example, trout lose their U-cones with age and the presence of U-cones may be altered by exposure to the hormone thyroxine. 6  
The fact that the two abnormal lighting conditions had differential effects on spectral sensitivity suggests that there may be two separate phenomena being observed for the LL and DD conditions. One possible explanation for this phenomenon in the LL group may be the result of damage to the system, whereas deficits found in the DD group may be due to a developmental delay. In the constant light condition, the system may develop normally and then begin to degenerate because of the overexposure to light. However, in the constant dark condition, the deficits may not be due to damage from the environment, but rather because of the lack of light stimulation, the visual system may fail to develop normally. Thus, subjects exposed to constant light conditions may have resulting damage to synaptic connections, but constant dark subjects are simply at an earlier developmental level. The possibility of a delay in visual development for the DD subjects is supported by the findings that many of the DD larvae, when removed from the DD condition at 6 dpf, were still not hatched. Zebrafish normally hatch at 3 dpf. 
Unlike those seen in higher vertebrates, the deficits seen in the b-wave spectral sensitivity of zebrafish subjects were not permanent. Once the subjects were returned to the normal environment, the differences found in the 6 to 8 dpf subjects were no longer evident at 13 to 15 and 21 to 24 dpf. By 21 dpf, all subjects appeared to have regained normal spectral sensitivity functions. There were no apparent differences across the three conditions. This is significant because it suggests that the zebrafish may be a good model for studying neural regeneration. 
Further work in this area should investigate the specific relationship between the light environment and visual function. The light environment used in the present study consisted of “daylight” fluorescent lights. Thus, the spectral emission of this source most likely contained energy spikes at certain wavelengths. This lighting condition was chosen because it was similar to the lighting used in past work that showed differences in zebrafish visual behavior 5 and because fluorescent lighting is often used in phototherapy. 11  
Summary and Conclusions
Like primates, the zebrafish is affected by constant light-rearing. The pattern seen in primates appears to be replicated in the zebrafish, with a severe deficit in the UV and short-wavelength areas and only a slight deficit in the middle- and long-wavelength areas. Interestingly, the effects found with constant dark rearing were different. These subjects showed a slight deficit across their entire visible spectrum. The difference between the zebrafish and primates is that the deficits were not permanent in the zebrafish. 
In conclusion, this study has established the viability of the zebrafish as a model for studying the effects of abnormal light-rearing conditions on retinal development. The unique features of early zebrafish retinal development offer avenues of research that have not previously been found in other species. For example, the high degree of retinal immaturity, in addition to its rapid development and its transparent shell, allow researchers to assess the effects of an abnormal environment in a short period without interrupting development. 
 
Figure 1.
 
b-Wave spectral sensitivity functions of 6 to 8 dpf subjects raised in LD (squares, n = 15), DD (circles, n = 11), and LL (triangles, n = 15) conditions. The lines represent the best-fit model to the data. Log relative sensitivity is defined as the reciprocal of the log irradiance that yielded a criterion response. Error bars, ±1 SEM.
Figure 1.
 
b-Wave spectral sensitivity functions of 6 to 8 dpf subjects raised in LD (squares, n = 15), DD (circles, n = 11), and LL (triangles, n = 15) conditions. The lines represent the best-fit model to the data. Log relative sensitivity is defined as the reciprocal of the log irradiance that yielded a criterion response. Error bars, ±1 SEM.
Figure 2.
 
(A) b-Wave spectral sensitivity functions of 13 to 15 dpf subjects raised in LD (squares, n = 16), DD (circles, n = 14), and LL (triangles, n = 16) conditions. The lines represent the best-fit model to the data. Log relative sensitivity is defined as the reciprocal of the log irradiance that yielded a criterion response. (B) b-Wave spectral sensitivity functions of 21 to 24 dpf subjects raised in LD (squares, n = 10), DD (circles, n = 16), and LL (triangles, n = 18) conditions. The lines represent the best-fit model to the data. Log relative sensitivity is defined as the reciprocal of the log irradiance that yielded a criterion response. (A and B) Error bars, ±1 SEM.
Figure 2.
 
(A) b-Wave spectral sensitivity functions of 13 to 15 dpf subjects raised in LD (squares, n = 16), DD (circles, n = 14), and LL (triangles, n = 16) conditions. The lines represent the best-fit model to the data. Log relative sensitivity is defined as the reciprocal of the log irradiance that yielded a criterion response. (B) b-Wave spectral sensitivity functions of 21 to 24 dpf subjects raised in LD (squares, n = 10), DD (circles, n = 16), and LL (triangles, n = 18) conditions. The lines represent the best-fit model to the data. Log relative sensitivity is defined as the reciprocal of the log irradiance that yielded a criterion response. (A and B) Error bars, ±1 SEM.
Figure 3.
 
a-Wave spectral sensitivity functions of the 6 to 8 dpf subjects. (A) Triangles, LL data (n = 11); circles, DD data (n = 9); and squares, LD data (n = 11). Log absolute sensitivity (quanta s−1 cm−2) is defined as the reciprocal of the log stimulus irradiance that yielded a criterion response. (B) Average spectral sensitivity function of the 6 to 8 dpf subjects raised in the three lighting conditions. The circles represent the data, and the line represents the best-fit model to the data. Log relative sensitivity is defined as the reciprocal of the log stimulus irradiance the yielded a criterion response. (A and B) Error bars, ±1 SEM.
Figure 3.
 
a-Wave spectral sensitivity functions of the 6 to 8 dpf subjects. (A) Triangles, LL data (n = 11); circles, DD data (n = 9); and squares, LD data (n = 11). Log absolute sensitivity (quanta s−1 cm−2) is defined as the reciprocal of the log stimulus irradiance that yielded a criterion response. (B) Average spectral sensitivity function of the 6 to 8 dpf subjects raised in the three lighting conditions. The circles represent the data, and the line represents the best-fit model to the data. Log relative sensitivity is defined as the reciprocal of the log stimulus irradiance the yielded a criterion response. (A and B) Error bars, ±1 SEM.
This work is based on a thesis by Shannon Saszik in partial fulfillment of the requirements for the M.A. degree from Western Kentucky University, Bowling Green Kentucky. The authors thank Paul J. DeMarco, Ph.D., J. Farley Norman, Ph.D., Jonathan D. Nussdorf, M.D., and Daniel Roenker, Ph.D., for their comments and Carla Givin and Christopher Harrison for assistance in data analysis. 
Harwerth RS, Sperling HG. Effects of intense visible radiation on the increment-threshold spectral sensitivity of the rhesus monkey eye. Vision Res. 1975;15:1193–1204. [CrossRef] [PubMed]
Hendrickson A, Boothe R. Morphology of the retina and dorsal lateral geniculate nucleus in dark-reared monkeys (Macaca nemestrina). Vision Res. 1976;16:517–521. [CrossRef] [PubMed]
Robinson J, Dowling JE. Light rearing and retinal development in zebrafish (Brachydanio rerio) [ARVO Abstract]. Invest Ophthalmol Vis Sci. 1994;35((4))S1512.Abstract nr 1199
Easter SS, Jr, Nicola GN. The development of vision in the zebrafish (Danio rerio). Dev Biol. 1996;180:646–663. [CrossRef] [PubMed]
Bilotta J, Dobis WT, Googe MD, Nunley WR, DeLorenzo AS. The effects of abnormal light rearing conditions on zebrafish visual development [ARVO Abstract]. Invest Ophthalmol Vis Sci. 1996;37((4))S631.Abstract nr 2920
Browman HI, Hawryshyn CW. Thyroxine induces a precocial loss of ultraviolet photosensitivity in rainbow trout (Oncorhynchus mykiss, Teleostei). Vision Res. 1992;32:2303–2312. [CrossRef] [PubMed]
Bilotta J, Saszik S, DeLorenzo AS, Hardesty HR. Establishing and maintaining a low-cost zebrafish breeding and behavioral research facility. Behav Res Methods Instr Comp. 1999;31:178–184. [CrossRef]
Hughes A, Saszik S, Bilotta J, DeMarco PJ, Jr, Patterson WF, II. Cone contributions to the photopic spectral sensitivity of the zebrafish ERG. Vis Neurosci. 1998;15:1029–1037. [CrossRef] [PubMed]
Saszik S, Bilotta J, Givin CM. ERG assessment of zebrafish retinal development. Vis Neurosci. In press.
Robinson J, Schmitt EA, Harosi FI, Reece RJ, Dowling JE. Zebrafish ultraviolet visual pigment: absorption spectrum, sequence, and localization. Proc Natl Acad Sci USA. 1993;90:6009–6012. [CrossRef] [PubMed]
Abramov I, Hainline L. Light and the developing visual system. Marshall J eds. The Susceptible Visual Apparatus. 1991;Vol 16 London, Macmillan
Figure 1.
 
b-Wave spectral sensitivity functions of 6 to 8 dpf subjects raised in LD (squares, n = 15), DD (circles, n = 11), and LL (triangles, n = 15) conditions. The lines represent the best-fit model to the data. Log relative sensitivity is defined as the reciprocal of the log irradiance that yielded a criterion response. Error bars, ±1 SEM.
Figure 1.
 
b-Wave spectral sensitivity functions of 6 to 8 dpf subjects raised in LD (squares, n = 15), DD (circles, n = 11), and LL (triangles, n = 15) conditions. The lines represent the best-fit model to the data. Log relative sensitivity is defined as the reciprocal of the log irradiance that yielded a criterion response. Error bars, ±1 SEM.
Figure 2.
 
(A) b-Wave spectral sensitivity functions of 13 to 15 dpf subjects raised in LD (squares, n = 16), DD (circles, n = 14), and LL (triangles, n = 16) conditions. The lines represent the best-fit model to the data. Log relative sensitivity is defined as the reciprocal of the log irradiance that yielded a criterion response. (B) b-Wave spectral sensitivity functions of 21 to 24 dpf subjects raised in LD (squares, n = 10), DD (circles, n = 16), and LL (triangles, n = 18) conditions. The lines represent the best-fit model to the data. Log relative sensitivity is defined as the reciprocal of the log irradiance that yielded a criterion response. (A and B) Error bars, ±1 SEM.
Figure 2.
 
(A) b-Wave spectral sensitivity functions of 13 to 15 dpf subjects raised in LD (squares, n = 16), DD (circles, n = 14), and LL (triangles, n = 16) conditions. The lines represent the best-fit model to the data. Log relative sensitivity is defined as the reciprocal of the log irradiance that yielded a criterion response. (B) b-Wave spectral sensitivity functions of 21 to 24 dpf subjects raised in LD (squares, n = 10), DD (circles, n = 16), and LL (triangles, n = 18) conditions. The lines represent the best-fit model to the data. Log relative sensitivity is defined as the reciprocal of the log irradiance that yielded a criterion response. (A and B) Error bars, ±1 SEM.
Figure 3.
 
a-Wave spectral sensitivity functions of the 6 to 8 dpf subjects. (A) Triangles, LL data (n = 11); circles, DD data (n = 9); and squares, LD data (n = 11). Log absolute sensitivity (quanta s−1 cm−2) is defined as the reciprocal of the log stimulus irradiance that yielded a criterion response. (B) Average spectral sensitivity function of the 6 to 8 dpf subjects raised in the three lighting conditions. The circles represent the data, and the line represents the best-fit model to the data. Log relative sensitivity is defined as the reciprocal of the log stimulus irradiance the yielded a criterion response. (A and B) Error bars, ±1 SEM.
Figure 3.
 
a-Wave spectral sensitivity functions of the 6 to 8 dpf subjects. (A) Triangles, LL data (n = 11); circles, DD data (n = 9); and squares, LD data (n = 11). Log absolute sensitivity (quanta s−1 cm−2) is defined as the reciprocal of the log stimulus irradiance that yielded a criterion response. (B) Average spectral sensitivity function of the 6 to 8 dpf subjects raised in the three lighting conditions. The circles represent the data, and the line represents the best-fit model to the data. Log relative sensitivity is defined as the reciprocal of the log stimulus irradiance the yielded a criterion response. (A and B) Error bars, ±1 SEM.
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