Ultrasound Imaging Reveals Accelerated In-utero Development of a Sensory Apparatus in Echolocating Bats

Eran Amichai,Smadar Tal,Arjan Boonman,Yossi Yovel

doi:10.1038/s41598-019-41715-y

Abstract

Organ development, both in-utero and after birth, follows a different path for every organ depending upon how early the newborn will use it. Perception of the environment using echolocation occurs very early in the life of neonatal bats. In nostril-emitting echolocating bats of the families Hipposideridae and Rhinolophidae, the shape and area of the nasal-horseshoe is crucial for echolocation emission. We therefore hypothesized that most of this organ’s ontogeny will be completed in-utero while skull and wings will develop slower and continue their growth after birth. We used intrauterine ultrasonography of pregnant females, and measured newborn Asellia tridens (Hipposideridae) to test our hypothesis at different stages of ontogeny. We found that horseshoe development is completed in-utero and neonates begin emitting precursor echolocation calls already two days after birth. In contrast, skull and forearm only develop to 70% and 40% of adult size (respectively), and continue development after birth.

Highlights

Precocial species, on the other hand, are self-reliant at an early stage and must possess a fullyfunctional sensory system soon after birth
We used B-mode ultrasound-imaging to measure horseshoe and skull sizes in-utero along the gestation in trident leaf-nosed bats (Asellia tridens). We found that their emission related apparatus approaches an adult size prior to parturition, in contrast to skull width and forelimbs that lag behind
To quantify the horseshoe’s development, we measured the distance between the base of the trident and the opposite edge of the horseshoe

Summary

Introduction

On the other hand, are self-reliant at an early stage and must possess a fullyfunctional sensory system soon after birth. Lesser horseshoe bats (Rhinolophus hipposideros), for example, are able to fly within 18–20 days from birth[10] and the trident leaf-nosed bat (Asellia tridens) is volant at three weeks[11] This is especially rapid when considering the general longevity of bats[12]. Their need to detect minute frequency changes drove the evolution of the so-called ‘acoustic fovea’[15,16] which is a dramatic over-representation of the bat’s specific emission frequency, in both the cochlea and brain Bats in these two families have evolved special facial appendages which surround their nostrils and are essential for forming their echolocation beam and crucial for spatial sensing[17,18,19] We found that their emission related apparatus approaches an adult size prior to parturition, in contrast to skull width and forelimbs that lag behind

Methods

Results

Conclusion