Morphological data of toad brain, eye, and body

In this study, we explored the size variation of optic tectum of the Asiatic toads (Bufo gargarizans) along altitudinal gradients, with a focus on its covariation with eye size.MeasurementToads were breeding adults collected during the breeding seasons (2018 and 2019) near breeding ponds in the Hengduan Mountains. The collection sites were along three altitudinal transects, ranging from 785 m to 3239 m above sea level. All animals were euthanized immediately at the collection sites by being submerged in a 0.25% MS-222 solution for 10 to 25 minutes. Death was confirmed when the toads' eyes closed and they stopped moving. All procedures adhered to approved protocols (Chengdu Institute of Biology, number 20171205).The calculated volume was used to represent the size of the optic tectum. Whole brains were dissected, and the cranial nerves, pineal organ, meninx, and pituitary glands were removed, though the pituitary infundibulum was retained. We took photographs of the brains from both top and side views, ensuring that the coronal and sagittal planes were parallel to the camera sensor. The length (L), width (W), and height (H) of the whole brain and right optic tectum were measured to the nearest 0.001 mm using ImageJ. Each optic tectum was measured three times by the same person (ZY), and the average value was used. Volume of brain was calculated using the modified ellipsoid formula: V = (L × H × W)π / (6 × 1.43), calibrated based on the Cavalieri method for amphibian brains. While volume of optic tectum was calculated using the ellipsoid formula: V = (L × H × W)π / 6. Finally, the total size of the optic tectum was obtained by doubling the calculated volume.The transverse cornea diameter was used as a measure of eye size. We photographed the right eyes from the side, controlling head position and angle to ensure that the plane containing the eye was parallel to the camera sensor. The length of the cornea along the major body axis was measured three times by the same person (ZY), and the average value was used. A similar method was applied to measure the snout-vent length (SVL) of the body using photos taken from the top view.Damaged organs were excluded from measurements. In total, data from 324 specimens across 14 sites (populations) were collected.DeclarationThis dataset consists of multiple files. One CSV file, named braineye, contains the data used for statistical analysis in this study.One R script file, named OT vs eye, includes all the analysis code for statistical analysis conducted on the R platform.One compressed folder, named photos of brain, contains the brain sample photographs used in this study. The brain morphology data were obtained from measurements made on these photos. The photos include sample identifiers and were taken in a sequence starting with top-view images, followed by side-view images. For some side-view photos where the sample identifier is not visible, the identifier corresponds to the preceding top-view photo.Another compressed folder, named photos of SVL and eye, contains the individual body size and eye photos used in this study. The body size photos are used to measure the snout-vent length (SVL), and the identifiers are visible in these photos. The eye photos are used to measure eye diameter, and the photos are arranged in the order of first capturing the identifier and then the eye.