Color signaling in conspicuous red sticklebacks: do ultraviolet signals surpass others?

<p>Abstract</p> <p>Background</p> <p>The use of ultraviolet (UV) signals for communication tasks is widespread in vertebrates. For instance, there is a UV component to mate choice in several species. Nevertheless, it remains unclear how the signal value of the UV wave band compares to that of other regions of the animal's visible spectrum. We investigated the relative importance of UV signals compared with signals of longer wavelengths in the threespine stickleback (<it>Gasterosteus aculeatus</it>), a species using UV wavelengths in female and male mate choice as well as in shoaling behavior. In a choice experiment, female sticklebacks were simultaneously presented with four male visual appearances manipulated by optical filters. Each male lacked one wavelength range of the stickleback's visible spectrum corresponding to the spectral sensitivities of the four cone types. The resulting male appearances thus had no UV (UV-), no short-wave (SW-), no medium-wave (MW-) or no long-wave (LW-) body reflectance.</p> <p>Results</p> <p>Males without UV wavelengths and long wavelengths ("red") were least preferred. In contrast, the removal of medium and most notably short wavelengths left male attractiveness to females rather unaffected. Using color metrics, the effects of the four optical filters on stickleback perception of three male body regions were illustrated as quantal catches calculated for the four single cones.</p> <p>Conclusion</p> <p>The removal of UV light (UV-) considerably reduced visual attractiveness of courting males to female three-spined sticklebacks particularly in comparison to the removal of short-wave light (SW-). We thus report first experimental evidence that the UV wave band clearly outranks at least one other part of an animal's visible spectrum (SW-) in the context of communication. In addition, females were also less attracted to males presented without long wavelengths (LW-) which supports the traditionally considered strong influence of the red color component on stickleback mate choice. Overall, the removal of medium wavelengths (MW-) and especially short (SW-) left male attractiveness for females rather unaffected. Our work suggests that, in addition to long wavelengths ("red"), the UV wave band contains important information for visual mate choice in sticklebacks. Hence, the previously suggested exclusive role of the characteristic red nuptial coloration in visual interactions between reproductively active stickleback conspecifics may be overestimated with UV wavelengths playing a more important role than previously suggested.</p

Male Red Ornamentation Is Associated with Female Red Sensitivity in Sticklebacks

Sexual selection theory proposes correlated evolutionary changes in mating preferences and secondary sexual characters based on a positive genetic correlation between preference and the preferred trait. Empirical work has provided support for a genetic covariation between female preference and male attractiveness in several taxa. Here, we study parent and offspring visual traits in threespine sticklebacks, Gasterosteus aculeatus. While focusing on the proximate basis of mating preferences, we compare the red breeding coloration of males, which strongly contributes to female choice, with their daughters' red sensitivity measured by optomotor response thresholds. We show that the red color expression of fathers correlates well with their daughters' red sensitivity. Given that a within-population genetic correlation between signal and preference was experimentally confirmed for the red coloration in sticklebacks, our results indicate a proximate mechanism in terms of perceptual sensitivity being involved in the co-evolution of female preferences and male mating signals

Design and baseline characteristics of the finerenone in reducing cardiovascular mortality and morbidity in diabetic kidney disease trial

Background: Among people with diabetes, those with kidney disease have exceptionally high rates of cardiovascular (CV) morbidity and mortality and progression of their underlying kidney disease. Finerenone is a novel, nonsteroidal, selective mineralocorticoid receptor antagonist that has shown to reduce albuminuria in type 2 diabetes (T2D) patients with chronic kidney disease (CKD) while revealing only a low risk of hyperkalemia. However, the effect of finerenone on CV and renal outcomes has not yet been investigated in long-term trials. Patients and Methods: The Finerenone in Reducing CV Mortality and Morbidity in Diabetic Kidney Disease (FIGARO-DKD) trial aims to assess the efficacy and safety of finerenone compared to placebo at reducing clinically important CV and renal outcomes in T2D patients with CKD. FIGARO-DKD is a randomized, double-blind, placebo-controlled, parallel-group, event-driven trial running in 47 countries with an expected duration of approximately 6 years. FIGARO-DKD randomized 7,437 patients with an estimated glomerular filtration rate >= 25 mL/min/1.73 m(2) and albuminuria (urinary albumin-to-creatinine ratio >= 30 to <= 5,000 mg/g). The study has at least 90% power to detect a 20% reduction in the risk of the primary outcome (overall two-sided significance level alpha = 0.05), the composite of time to first occurrence of CV death, nonfatal myocardial infarction, nonfatal stroke, or hospitalization for heart failure. Conclusions: FIGARO-DKD will determine whether an optimally treated cohort of T2D patients with CKD at high risk of CV and renal events will experience cardiorenal benefits with the addition of finerenone to their treatment regimen. Trial Registration: EudraCT number: 2015-000950-39; ClinicalTrials.gov identifier: NCT02545049

UV matters in shoaling decisions

Shoaling behaviour in fish is influenced by numerous factors, such as familiarity, kinship, group size and shoal composition. Grouping decisions are based on both olfactory and visual cues. The visual system of many vertebrates is extended into the ultraviolet (UV) wave range as in three-spined sticklebacks (Gasterosteus aculeatus, L.). We investigated whether the presence or absence of UV wavelengths has an influence on shoaling behaviour in this species. Reproductively non-active three-spined sticklebacks were given the choice between two shoals, equal in numbers of individuals, which could be seen either through a UV-transmitting [UV(+)] or a UV-blocking [UV(−)] filter. Test fish preferred to join the shoal seen under UV(+) conditions. Due to differences in quantal flux between the UV(+) and UV(−) filters used, control experiments with neutral-density optical filters were performed in order to clarify the role of luminance. Here, test fish spent significantly more time near shoals that were seen in a darker environment, suggesting a potential trade-off between UV radiation and lower brightness during shoal choice. To our knowledge, these results demonstrate for the first time that shoaling decisions are influenced by UV wavelengths

Ultraviolet reflection enhances the risk of predation in a vertebrate

Many animals are sensitive to ultraviolet light and also possess UV-reflective regions on their body surface. Individuals reflecting UV have been shown to be preferred during social interactions such as mate choice or shoaling decisions. However, whether those body UV-reflections enhance also the conspicuousness to UV-sensitive predators and therefore entail costs for its bearer is less well documented. Two size-matched three-spined sticklebacks Gasterosteus aculeatus, one enclosed in a UV-transmitting (UV+) and another in a UV-blocking (UV-) chamber, were simultaneously presented to individual brown trout Salmo trutta. “yearlings”. Brown trout of this age are sensitive to the UV part of the electromagnetic spectrum and are natural predators of three-spined sticklebacks. The stickleback that was attacked first as well as the subsequent number of attacks was recorded. Sticklebacks enclosed in the UV-transmitting chamber were attacked first significantly more often compared to sticklebacks enclosed in the UV-blocking chamber. Control experiments using neutral density filters revealed that this was more likely due to UV having an influence on hue perception rather than brightness discrimination. The difference in attack probability corresponded to the difference in chromatic contrasts between sticklebacks and the experimental background calculated for both the UV+ and UV- conditions in a physiological model of trout colour vision. UV reflections seem to be costly by enhancing the risk of predation due to an increased conspicuousness of prey. This is the first study in a vertebrate, to our knowledge, demonstrating direct predation risk due to UV wavelengths [Current Zoology 59 (2): 151-159, 2013]

Color signaling in conspicuous red sticklebacks: do ultraviolet signals surpass others?-1

A) the ventral spine of male sticklebacks. (B-B) Relative quantal catches calculated for the four stickleback cone classes (UV, S, M, L) affected by the reflectance of the experimental background and each male body region under fullspectrum illumination (Natural) and under the four treatment filters (UV-, SW-, MW-, LW-). Quantal catches are calculated relative to the excitation of the four cone types by the stimulus background under unfiltered light (C) Relative irradiance (log quantal flux) of the True Light tubes used in the experiment and visual modelling. Irradiance was measured with an Avantes AVS-USB2000 connected to an Avantes CC-UV/VIS cosine corrector located in the stimulus tank centre with filters removed. Irradiance calibration was performed versus an Avantes NIST traceable irradiance application standard.<p><b>Copyright information:</b></p><p>Taken from "Color signaling in conspicuous red sticklebacks: do ultraviolet signals surpass others?"</p><p>http://www.biomedcentral.com/1471-2148/8/189</p><p>BMC Evolutionary Biology 2008;8():189-189.</p><p>Published online 1 Jul 2008</p><p>PMCID:PMC2453139.</p><p></p

Color signaling in conspicuous red sticklebacks: do ultraviolet signals surpass others?-2

F males under the ultraviolet-blocking (UV-), short-wave-blocking (SW-), medium-wave-blocking (MW-) and long-wave-blocking (LW-) treatment filters during the 10 min test phase of the stimulus experiment. (B) Mean relative time ± SEM spent by eight females within the preference zones in front of empty tanks under the UV-, SW-, MW- and LW- treatment filters during the 10 min test phase of the control experiment.<p><b>Copyright information:</b></p><p>Taken from "Color signaling in conspicuous red sticklebacks: do ultraviolet signals surpass others?"</p><p>http://www.biomedcentral.com/1471-2148/8/189</p><p>BMC Evolutionary Biology 2008;8():189-189.</p><p>Published online 1 Jul 2008</p><p>PMCID:PMC2453139.</p><p></p

Color signaling in conspicuous red sticklebacks: do ultraviolet signals surpass others?-0

F males under the ultraviolet-blocking (UV-), short-wave-blocking (SW-), medium-wave-blocking (MW-) and long-wave-blocking (LW-) treatment filters during the 10 min test phase of the stimulus experiment. (B) Mean relative time ± SEM spent by eight females within the preference zones in front of empty tanks under the UV-, SW-, MW- and LW- treatment filters during the 10 min test phase of the control experiment.<p><b>Copyright information:</b></p><p>Taken from "Color signaling in conspicuous red sticklebacks: do ultraviolet signals surpass others?"</p><p>http://www.biomedcentral.com/1471-2148/8/189</p><p>BMC Evolutionary Biology 2008;8():189-189.</p><p>Published online 1 Jul 2008</p><p>PMCID:PMC2453139.</p><p></p