TADPOLES RESPOND TO BACKGROUND COLOUR UNDER THREAT PAULA CABRAL ETEROVICK , IZABELA SANTOS MENDES, JÉSSICA STEPHANIE KLOH, LUAN TAVARES PINHEIRO, AMADEUS BICALHO HORTA PORTELA VÁCLAV, THIAGO SANTOS & ANA SOFA BUZA GONTIJO 06 MARCH 2018 BLISS D’SOUZA 03 CAMOUFLAGE IN FROGS AND TADPOLES Ø Some animals use camouflage to hide in their environment in plain sight. Ø Camouflage is when an organism matches its color or shape to its environment, blending in seamlessly. Many animals use camouflage to add an element of surprise to their attack or to hide from their enemies. Ø Frogs are masters of the art of camouflage. Ø In the American bullfrog bumpy skin looks like piles of moss or algae on the surface of ponds. Their dark green and brown patches help them blend in perfectly with the murky water in their homes. Ø Similarly in the African clawed frog , it camouflage with the green algae, mud, and rocks in the stagnant pools in which it lives. The belly of the African clawed frog is light yellow to white, like many other aquatic animals. When viewed from below, their white underside blends in with the glare of the sun on the water, keeping them hidden from above and below. African clawed frog American bullfrog Tadpole Predators Ø Similarly Tadpoles or frogspawn is also subjected to predators . Ø Therefore these Juvenile form of frogs also developed certain ways of dodging predators. Ø The tadpoles either avoid being preyed by the predator by releasing certain chemicals (PHEROMONES) or by simply locomoting to a region similar to their outer morphology and hide in plain sight taking advantage of their similar colour scheme with the environment. DRAGONFLY EATING TADPOLE WOOD FROG TADPOLE CAMOUFLAGING INTRODUCTION • The ability to respond to background colour is an important feature of species that might benefit from background matching camouflage. Tadpole colour patterns vary and could be associated with several functions, including defense. Because tadpoles are exposed to a wide array of visually oriented predators, they represent good models to study defensive colouration and associated behaviours • Here they tested whether a potentially disruptively camouflaged tadpole with a dark body crossed by yellow bars (Ololygon machadoi) is able to respond differently to matching light and dark natural background colours and an artifcial blue contrasting background. • We used a syntopic contrasting black tadpole (Bokermannohyla martinsi) as a control, expecting it not to respond to background colour in search for camouflage. A O.machadoi tadpoles O.machadoi in between B. martinsi tadpoles for background contrast for comparison . B B. Martinsi Tadpoles • Ololygon machadoi tadpoles chose light over blue backgrounds under threat, as expected, however they did not show preferential use of dark vs. blue backgrounds. • Bokermannohyla martinsi did not respond to any combination of background colours. • Our results suggest that O. machadoi tadpoles are able to respond to background colour, and may favor matching backgrounds under some circumstances. • The potentially disruptive colouration of O. machadoi tadpoles may increase their repertoire of escape strategies, background matching being one of the options to escape predation. • Knowledge on the functions of tadpole colourations is incipient compared to other organisms such as birds and fishes . For instance, there is a scarcity of quantitative data on predator avoidance via decreased detection probability promoted by tadpole colouration hence the experiment was carried out to understand Comparison of escape strategies among tadpoles with varied colour patterns will be interesting to further understand the role of tadpole defensive colourations in tropical habitats with a great array of potential predators. METHODOLOGY • The study was conducted at the Reserva Particular do Patrimônio Natural (RPPN) Santuário do Caraça (20°05′S, 43°29′W; 750–2,072m alt.). This private reserve encompasses 12,403ha in the southern portion of the Espinhaço Mountain Range, southeastern Brazil. • The climate has a rainy season from October to March and a dry season from April to September, with mean monthly temperatures varying from 13 to 29 °c. The reserve has several permanent streams where tadpoles of Bokermannohyla martinsi (Bokermann, 1964) and Ololygon machadoi are the most abundant and can be found year-round. • In order to replicate the environment of the stream other than the colour an actual picture of the stream was used • These experimental backgrounds were created by using photographs area under the stream ,these pictures were laminated. • The yellow background was a picture of an actual stream bed light background • The blue background consisted in the same picture digitally manipulated to resemble the colour of an artifcial blue background intended to make the tadpoles easily detectable. They chose blue because tadpoles are sensitive to this colour and it is far from the yellow spectrum of natural backgrounds and tadpole bodies. • The dark background was also made from the same picture digitally manipulated to resemble the colours of a real dark stream background. • They considered as dark backgrounds that were actually dark and not just more shaded. They made all experimental backgrounds based on the same picture to standardize texture because visual complexity is also likely to influence background choice for improved concealment. • They used Adobe Photoshop CS6, version 13.0×64 (Adobe Photoshop 1990–2012, Adobe Systems we compared reflectance of tadpole’s yellow and dark body parts with reflectance of printed yellow and dark backgrounds respectively, and also measured reflectance of rocks from the stream bottom. • They investigated the correspondence among tadpole, natural background and picture considering different visual systems of the species involved not only in this experiment, but also in the evolution of background colour choice as a defensive behavior in O. machadoi. They used a spectrophotometer USB2000+UV-VIS-ES (Ocean Optics Inc.) calibrated between 250 and 750 nm with a deuterium/tungsten light source. • They taped printed laminated pictures of yellow, dark and blue backgrounds to the bottom of six plastic trays (Two trays per treatment) (43 cm length, 30 cm width, 9 cm height). These backgrounds were combined in pairs (each colour covering half the tray bottom. The test run for both tadpoles was carried out simultaneously. • Resulting in three treatments: q DARK/YELLOW q BLUE/YELLOW q BLUE/DARK Laminated pictures of experimental Backgrounds 3 trays for O. machadoi 3 trays for B.martinsi • Total 324 tadpoles of both B .martinsi and o. machadoi were tested in span of 3 days. • Total 54 runs were done for both tadpoles of O.machadoi and B. martinsi simultaneously; in batches of 6 every run. DISTURBING THE TADPOLES • The tadpoles were exposed in the trays and waited until 3 minutes after the settle and choose preferential background after 3 minutes the were disturbed with a stick to induce their defensive mechanism and observe which area of tray the swim ;whether it will be the its original location or the other end of the tray with different colour. TRAY WITH TWO BACKGROUNDS RESULT • In the treatment with yellow/dark backgrounds, O. machadoi tadpoles preferred yellow over dark backgrounds initially after disturbance, the ones on yellow background stay at the same place and the ones on black travel to yellow background. • As for B.martinsi no certain change was observed as expected. • In the treatment with yellow/ blue backgrounds, O. machadoi tadpoles that chose yellow backgrounds initially were more likely to choose them again after disturbance whereas tadpoles that chose blue backgrounds initially were more likely to change to yellow backgrounds after disturbance. • As for B.martinsi no certain change was observed as expected. • In the treatment with blue/dark backgrounds, tadpoles did not choose any colour initially or favor any behavior in general or depending on initial colour. • As for B.martinsi no certain change was observed as expected. Discussion • Ololygon machadoi tadpoles used yellow backgrounds preferentially compared to dark backgrounds before an imposed aversive stimulus, possibly indicating an innate (or learnt) preference. preference • They were also likely to remain on yellow backgrounds or move towards them after being exposed to an aversive stimulus in dark/yellow treatments. • When exposed to blue/yellow backgrounds, tadpoles were not hesitant to explore the unfamiliar blue background initially, but once disturbed on blue backgrounds most of them promptly moved to yellow backgrounds. • We expected a significant decrease in use of blue backgrounds after the aversive stimulus also in the blue/dark treatment, which did not happen. In the natural habitat, O. machadoi tadpoles, when disturbed, move short distances and then stop motionless. • Reduced movement is a known strategy to reduce predation risk by tadpoles hence here they used the first strategy to go motionless to reduce chances of predation. • As far as B. martinsi tadpoles, used as a control, did not show any significant change in use of background colours before or after the aversive stimulus in any treatment, as expected. After disturbance, most B. martinsi tadpoles positioned themselves on the same colour chosen initially in two of the three treatments (dark/yellow and blue/yellow), what may have been a fortuitous consequence of the higher activity levels of this species. However, there were no interactions between this behavior and colour, different from O. machadoi. https://www.nature.com/articles/s41598-018 -22315-8 THANK YOU!
