Flight is the key to postprandial blood glucose balance in the fruit bats Eonycteris spelaea and Cynopterus sphinx.

Xingwen Peng,Zhen Peng,Qi Liu,Qin Zhang,Xiangyang He,Libiao Zhang,Hui Liu,Yunxiao Sun,Zhixiao Liu,Jie Liang

doi:10.1002/ece3.3416

Abstract

Excessive sugar consumption could lead to high blood glucose levels that are harmful to mammalian health and life. Despite consuming large amounts of sugar‐rich food, fruit bats have a longer lifespan, raising the question of how these bats overcome potential hyperglycemia. We investigated the change of blood glucose level in nectar‐feeding bats (Eonycteris spelaea) and fruit‐eating bats (Cynopterus sphinx) via adjusting their sugar intake and time of flight. We found that the maximum blood glucose level of C. sphinx was higher than 24 mmol/L that is considered to be pathological in other mammals. After C. sphinx bats spent approximately 75% of their time to fly, their blood glucose levels dropped markedly, and the blood glucose of E. spelaea fell to the fast levels after they spent 70% time of fly. Thus, the level of blood glucose elevated with the quantity of sugar intake but declined with the time of flight. Our results indicate that high‐intensive flight is a key regulator for blood glucose homeostasis during foraging. High‐intensive flight may confer benefits to the fruit bats in foraging success and behavioral interactions and increases the efficiency of pollen and seed disposal mediated by bats.

Highlights

Flight is the most economical patterns of animal location according to the energy consumption per unit of distance travelled
We found that C. sphinx and E. spelaea showed highly variable blood glucose levels after ingestion of different quantity of sucrose
When the blood glucose had reached a high level, E. spelaea was able to reduce it to their fasting values through sustained, high intensive flight, such as flight for approximately 60%–75% of the time

Summary

| INTRODUCTION

Flight is the most economical patterns of animal location according to the energy consumption per unit of distance travelled. The rate of flight metabolism is eightfold to 15-fold higher than that of basal metabolism (Speakman & Thomas, 2003) and the energy consumption during flight is 10-to 12-fold higher than that during rest (Voigt & Winter, 1999) These are metabolic patterns for nectar-feeding bats (Phyllostomidae: Glossophaginae). | 8805 large amounts of sugar in daily diet; whether they overcome potential hyperglycemia after feeding is not known Fruit bats, such as Glossophagine bat, a small bat (approximately 10 g) in the family Phyllostomidae may consume nearly a 1.5-fold of its body mass in nectar or a quarter of its body mass in sugar each night (Helversen & Reyer, 1984; Kelm et al, 2008; Voigt, Kelm, & Visser, 2006). As Eonycteris spelaea (nectarivorous) and Cynopterus sphinx (frugivorous) of the family Pteropodidae are fruit bats commonly found in Southern China, in this study, these bats were used to explore whether Kelm’s hypothesis is applicable to Pteropodidae bats and to examine our hypotheses: The level of postprandial blood glucose is (1) positively correlated to the amount of sugar intake, but it is (2) negatively correlated to the flight duration

| MATERIALS AND METHODS

| DISCUSSION

Findings

CONFLICT OF INTEREST