DOI: 10.5061/dryad.931zcrjnv
title: Size of brain, heart, liver, alimentary tract, and kidneys along altitudinal gradients in Asiatic toad

description: Brain size variation is frequently linked to energetic trade-offs with
 other metabolically demanding tissues or organs, a concept central to the
 expensive brain hypothesis (EBH). In this study, we investigate Asiatic
 toads (Bufo gargarizans) along altitudinal gradients, focusing on the
 trade-offs in size between the brain and four key visceral organs: the
 heart, liver, alimentary tract, and kidney. We estimated brain volume by
 measurement. We measured the dry weight of four organs: the
 heart, liver, alimentary tract, and kidneys. Additionally, we measured the
 snout-vent length and body weight of individuals. Our results indicate
 that both body size and scaled mass index—an indicator of total energy
 intake—decrease at higher altitudes, suggesting increased energetic
 constraints in high altitudinal environments. As altitude rises, we
 observe a reduction in relative brain size, while the relative sizes of
 visceral organs tend to increase. Through structural equation modeling, we
 identify a significant negative correlation between brain size and a
 latent variable termed "budget," which reflects energy
 allocation to the four visceral organs in high-altitude toads. Notably,
 the heart shows the most pronounced and consistent response to variations
 in energy distribution. In contrast, no such relationships are observed in
 toads at mid- and low-altitudes, where higher energy intake may enable
 individuals to bypass these trade-offs. When considering EBH in
 poikilothermic species, it is essential to emphasize total energy intake
 alongside energy allocation strategies. Future research on EBH should
 focus on intra-specific comparisons and explore the fitness implications
 that extend beyond mere energy constraints.
description: A total
 of 434 individuals from 15 sites of 3 transects were sampled from west of
 the Sichuan Basin in 2018 and 2019. All toads were sampled in the breeding
 season and were breeding adults. All transects were controlled within a
 straight-line distance of 85 km, which reduces confounding ecological
 background variables. Snout vent length (SVL) was used for body size
 and was measured from photos that were taken from a dorsal view with a
 ruler as a reference. We measured SVL three times using ImageJ version
 1.53g, and used the
 average value. The scaled mass index (SMI) was used to assess body
 condition and was calculated by an equation which was described in the
 related article.  Brains were
 dissected out; the cranial nerves, pineal organs, meninx, and pituitary
 glands (but not the pituitary infundibulum) were removed. Photographs of
 brains were taken from dorsal, side, and ventral views with a ruler as a
 reference. The coronal plane and sagittal plane were placed parallel to
 the camera sensor. The length, width, and height of the brain were
 measured to the nearest 0.001 mm from the photographs. All measurements were conducted three times by
 the same investigator (ZY) and the average value was used. The volume of
 each brain region was calculated using the ellipsoid model as V= (L×H×W)
 π/ (6×1.43). To obtain
 the dry mass of the heart, liver, alimentary tract, and kidneys, we use
 the dissection method. The liver included the overall liver and excluded
 the gall bladder. The alimentary tract includes the stomach and small and
 large intestine. The contents in the alimentary tract were softly
 eliminated before drying. Kidneys included the pair, and the heart
 included the overall heart. These organs were then washed by tap water
 overnight, and dried in a baking oven (55 ℃) until their weights
 stabilized. All dried organs were weighted to the nearest 0.0001 g by an
 electronic balance (STP2004). Organs that were damaged during the
 dissection process were
 excluded.
description: # Size of brain, heart, liver, alimentary tract, and kidneys along
 altitudinal gradients in Asiatic toad We have submitted our raw data
 (totalmassdata.csv), R script (totalmassdata.R).  **Data File:
 totalmassdata.csv** ID: Identification of each specimen used in this
 project transect: Sampling altitudinal gradient along the river valley,
 which consists of 4 to 6 sampling populations site: Sampling population,
 which consists of individuals captured near the same breeding pond sex:
 Determining the sex of individuals through nuptial pads, in which m
 represents male and f represents female ALT: Sampling altitude of
 individuals (km) ELE: Altitudinal group, which is determined by
 unpublished principle analysis results with bioclimate data of sampling
 location. L represents the low altitudinal group, M is the middle
 altitudinal group, and H is the high altitudinal group bodymass:
 Individual’s body weight that was measured by an electronic balance
 accurate to 0.1 g heart: Dry weight of heart (g) liver: Dry weight of
 liver (g) digest: Dry weight of alimentary tract (g) kidney: Dry weight of
 paired kidneys (g) SVL: Snout-vent-length which was measured by photo (mm)
 BRA: Whole brain volume which was calculated from measured length, width,
 and height (mm3) SMI: Scaled body-mass index, which was calculated
 according to an equation with body mass and SVL In the file, the null
 padding indicates that the observation for this sample is unavailable due
 to anatomical damage or other reasons. **Code/Software: totalmassdata.R**
 R is required to run totalmassdata.R Script; the script was created using
 version 4.2.2. Annotations are provided throughout the script through 1)
 library loading, 2) dataset loading and cleaning, 3) analyses, and 4)
 figure creation.