scholarly journals Distance-dependent aposematism and camouflage in the cinnabar moth caterpillar ( Tyria jacobaeae , Erebidae)

2018 ◽  
Vol 5 (2) ◽  
pp. 171396 ◽  
Author(s):  
James B. Barnett ◽  
Innes C. Cuthill ◽  
Nicholas E. Scott-Samuel
Keyword(s):  
Visual Acuity ◽  
Avoidance Learning ◽  
Predator Avoidance ◽  
High Contrast ◽  
Warning Signals ◽  
Tyria Jacobaeae ◽  
Dependent Signal ◽  
Close Range ◽  
Cinnabar Moth ◽  
Speed And Accuracy

Defended prey often use distinctive, conspicuous, colours to advertise their unprofitability to potential predators (aposematism). These warning signals are frequently made up of salient, high contrast, stripes which have been hypothesized to increase the speed and accuracy of predator avoidance learning. Limitations in predator visual acuity, however, mean that these patterns cannot be resolved when viewed from a distance, and adjacent patches of colour will blend together (pattern blending). We investigated how saliency changes at different viewing distances in the toxic and brightly coloured cinnabar moth caterpillar ( Tyria jacobaeae ). We found that although the caterpillars' orange-and-black stripes are highly salient at close range, when viewed from a distance the colours blend together to match closely those of the background. Cinnabar caterpillars therefore produce a distance-dependent signal combining salient aposematism with targeted background matching camouflage, without necessarily compromising the size or saturation of their aposematic signal.

scholarly journals Minimum Detectable Change of Visual Acuity Measurements Using ETDRS Charts (Early Treatment Diabetic Retinopathy Study)

2021 ◽  
Vol 18 (15) ◽  
pp. 7876
Author(s):  
María Carmen Sánchez-González ◽  
Raquel García-Oliver ◽  
José-María Sánchez-González ◽  
María-José Bautista-Llamas ◽  
José-Jesús Jiménez-Rejano ◽  
...  
Keyword(s):  
Visual Acuity ◽  
Diabetic Retinopathy ◽  
Early Treatment ◽  
High Reliability ◽  
Minimal Detectable Change ◽  
High Contrast ◽  
Detectable Change ◽  
Low Contrast ◽  
Minimum Detectable Change ◽  
The Mean

In our work, we determined the value of visual acuity (VA) with ETDRS charts (Early Treatment Diabetic Retinopathy Study). The purpose of the study was to determine the measurement reliabilities, calculating the correlation coefficient interclass (ICC), the value of the error associated with the measure (SEM), and the minimal detectable change (MDC). Forty healthy subjects took part. The mean age was 23.5 ± 3.1 (19 to 26) years. Visual acuities were measured with ETDRS charts (96% ETDRS chart nº 2140) and (10% SLOAN Contrast Eye Test chart nº 2153). The measurements were made (at 4 m) under four conditions: Firstly, photopic conditions with high contrast (HC) and low contrast (LC) and after 15 min of visual rest, mesopic conditions with high and low contrast. Under photopic conditions and high contrast, the ICC = 0.866 and decreased to 0.580 when the luminosity and contrast decreased. The % MDC in the four conditions was always less than 10%. It was minor under photopic conditions and HC (5.83) and maximum in mesopic conditions and LC (9.70). Our results conclude a high reliability of the ETDRS test, which is higher in photopic and high contrast conditions and lower when the luminosity and contrast decreases.

Predator Interference with the Cinnabar Moth (Tyria jacobaeae) for the Biological Control of Tansy Ragwort (Senecio jacobaea)

2011 ◽  
Vol 4 (3) ◽  
pp. 332-340 ◽  
Author(s):  
Kimberly K. Crider
Keyword(s):  
Biological Control ◽  
Invasive Plant ◽  
Abiotic Factors ◽  
Biological Control Agents ◽  
Moth Population ◽  
Tyria Jacobaeae ◽  
Carpenter Ants ◽  
Ant Predation ◽  
Cinnabar Moth ◽  
Tansy Ragwort

AbstractQuantification of interference with biological control agents can provide support for anecdotal claims of success or failure of agent establishment and efficacy. This study was initiated because of observed predation of cinnabar moth larvae by carpenter ants when releasing larvae for the control of tansy ragwort, an invasive plant in Montana. Biotic and abiotic factors were compared among three sites with historically variable moth population establishment. Two experiments were developed to (1) observe and document insect activity, predation, or disappearance on tansy ragwort stems either protected or accessible to ants; and (2) quantify the effects of ant exclusion on herbivory of tansy ragwort. Site comparisons indicated that ant colony density was highest at the driest of three sites, and, interestingly, no ant colonies were detected at the site with higher observed numbers of moth larvae and adults and lower densities of tansy ragwort. Available substrate (logs and stumps) for ant colonization did not differ between the three sites. In the ant exclusion experiments, a larger number of larvae were missing on plants accessible to ants (63%) compared with plants where ants were excluded (39%) after 36 h. Direct observation of predation of larvae by carpenter ants accounted for 9% of missing larvae on stems accessible to ants. Larvae were able to consume 81% of original flowers or buds on ant-excluded stems, compared with 18% consumption on ant-accessible stems, suggesting that ant predation could limit the efficacy of cinnabar moth larvae. These results provide one of many possible explanations for the anecdotal observations of large, persistent populations of cinnabar moths in moist areas. This work emphasizes the importance of post-release observation and monitoring to detect and, ideally, quantify factors to support anecdotal perceptions regarding the fate and subsequent efficacy of insect biological-control agents.

scholarly journals Distance-dependent defensive coloration in the poison frog Dendrobates tinctorius, Dendrobatidae

2018 ◽  
Vol 115 (25) ◽  
pp. 6416-6421 ◽  
Author(s):  
James B. Barnett ◽  
Constantine Michalis ◽  
Nicholas E. Scott-Samuel ◽  
Innes C. Cuthill
Keyword(s):  
Computational Modeling ◽  
In Situ Experiment ◽  
Warning Signals ◽  
Detection Experiment ◽  
Poison Frog ◽  
Bright Yellow ◽  
Close Range ◽  
Black Color

Poison dart frogs provide classic examples of warning signals: potent toxins signaled by distinctive, conspicuous coloration. We show that, counterintuitively, the bright yellow and blue-black color of Dendrobates tinctorius (Dendrobatidae) also provides camouflage. Through computational modeling of predator vision, and a screen-based detection experiment presenting frogs at different spatial resolutions, we demonstrate that at close range the frog is highly detectable, but from a distance the colors blend together, forming effective camouflage. This result was corroborated with an in situ experiment, which found survival to be background-dependent, a feature more associated with camouflage than aposematism. Our results suggest that in D. tinctorius the distribution of pattern elements, and the particular colors expressed, act as a highly salient close range aposematic signal, while simultaneously minimizing detectability to distant observers.

Sickle cell maculopathy: prevalence, associations and impact on visual acuity

2020 ◽  
Author(s):  
Haroen Sahak ◽  
Mohammed Saqalain ◽  
Pooi Lott ◽  
Martin Mckibbin
Keyword(s):  
Visual Acuity ◽  
Sickle Cell Disease ◽  
Visual Impairment ◽  
Sickle Cell ◽  
Consecutive Series ◽  
High Contrast ◽  
Cell Disease ◽  
Spectral Domain Oct ◽  
Frequent Finding ◽  
The Impact

Aims: To investigate the prevalence of sickle cell maculopathy (SCM), associations with age, sex, genotype and proliferative sickle cell retinopathy (PSR) stage and the impact on visual acuity Methods: Age, sex and visual acuity were recorded and spectral domain OCT and ultra-widefield images of the macula and retina were reviewed for a consecutive series of 74 adults with sickle cell disease Results: The median age was 37 years (range 19-73 years) and 36 cases (48.6%) were male. SCM was present in at least one eye of 40 cases (54.1%) or in 67 of all eyes (42.3%). SCM prevalence was 54.8%, 62.5% and 25% for HbSS, HbSC and HbS/BThal or other genotypes respectively. SCM was observed in 41 (39.4%) of the eyes with PSR stages 0,1,2 and 21 (51.2%) of the eyes with PSR stages 3,4,5. Mild visual impairment or worse was present in 3 eyes (4.8%) with SCM but this was secondary to other pathology. Conclusion: SCM is a frequent finding in eyes of adults with sickle cell disease. The prevalence is similar for both HbSS and HbSC genotypes and is not related to the PSR stage. High-contrast distance visual acuity is typically preserved.

Meridional Variation in Visual Acuity of Hooded Rats Reared in a Carpentered Environment

Perception ◽  
1981 ◽  
Vol 10 (4) ◽  
pp. 423-430 ◽  
Author(s):  
Paul Dean ◽  
Phillip Horlock ◽  
Ian M Strachan
Keyword(s):  
Animal Model ◽  
Visual Acuity ◽  
Visual Cortex ◽  
Low Frequency ◽  
Oblique Effect ◽  
Neural Mechanisms ◽  
High Contrast ◽  
Square Wave ◽  
Laboratory Rats ◽  
Good Animal Model

Resolution acuity in people is frequently better for horizontal and vertical gratings than for obliques. An animal model of this oblique effect might be of help in elucidating its underlying neural mechanisms. Rats were chosen because laboratory rats are reared in a ‘carpentered environment’ apparently similar to those proposed to cause the oblique effect in people, and because electrophysiological experiments suggest that orientation selective units in rats' visual cortex may prefer horizontal and vertical stimuli. The acuity of eight laboratory-reared hooded rats was measured with high-contrast horizontal, vertical, and oblique gratings. The animals learned to detect low-frequency square-wave gratings with slightly fewer errors if they were horizontal or vertical than if they were oblique, but the effects of grating orientation on acuity were not significant. Refraction of the rats' eyes gave no evidence of astigmatism. These results suggest that the rat may not be a good animal model for studying the mechanisms that underlie meridional variations in acuity in people, and raise questions concerning both the neural bases of resolution acuity, and the validity of the ‘carpentered environment’ hypothesis.

Sign in / Sign up

Export Citation Format

Share Document