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Imaging Metamorphosis in Lepidoptera with Magnetic Resonance Imaging
Gavin D. Merrifield1, James Mullin1 and William. M. Holmes1
1. Glasgow Experimental MRI Centre, University of Glasgow
Introduction
Abrupt transitions between life stages occur across many different animals groups. However none has the broad public awareness that the metamorphosis of Lepidoptera
species (moths and butterflies) has. Despite our casual familiarity with this activity the process itself has not been studied extensively using modern non-invasive in vivo
imaging techniques. These techniques would enable serial non-destructive imaging of individual specimens, allowing changes in anatomy to be tracked over time and for
environmental pressures on development to be quantified. Of the many techniques available today Magnetic Resonance Imaging (MRI) provides the best soft-tissue
contrast, adjustable acquisition contrast settings and a pre-existing body of literature and advanced techniques that could be rapidly utilised to study these process in vivo.
Methods
We scanned example subjects of the Atlas moth caterpillar (Attacus atlas) at the larva/pupa crossover stage and
into the subsequent developmental period. We also scanned examples from a Papilionidae species prior to final
emergence as a butterfly.
MRI scans were performed on a 7T preclinical MRI scanner equipped with a range of different commercially
available MRI coils as suited the various species and time points being scanned. A Gradient Echo 3D sequence
scan was finalised and images were processed in variety of ways to highlight appropriate features. The finalised 3D
scan protocol had a total scan acquisition time of ~10mins.
Subjects were placed unrestrained in plastic carriages or tubes as required in order to limit gross movement and to
hold subjects safely in position within the scanner. Atlas examples were left fixed to the branches of a privet plant
that they had attached themselves to upon pupation in order to minimise disturbance to the subject.
Initially subjects were chilled for short periods (<30mins) in an attempt to limit subject motion and resulting image
artefacts. Scan times however were shortened to ~10 minutes which non-chilled subjects seemed to tolerate.
Additionally relaxation of the chilled subjects typically resulted in more motion artefacts than in non-chilled subjects.
We suggest that MRI is a highly suitable technique for experimental studies of the metamorphic process in Lepidoptera species. In a controlled environment the technique
can be used to easily and directly visualise and quantify underlying genetic and environmental influences on development during metamorphosis.
Conclusions
A10.82
Contact Author: gavin.merrifield@glasgow.ac.uk
Imaging Results
Gross internal and external morphological changes could be easily discerned in resultant images. The inherent soft-tissue contrast of MRI allows for different structures to
be visualised in image post-processing. Note that these images are not to scale. The length of the subject shortens considerably when changing from the larvae to adult
form.
Photo Image GE3D FLASH MRI Surface Render Max. Intensity Projection
DEVELOPMENT
Attacus atlas specimen positioned
ready for scanning.
Papilionidae specimen contained in
plastic syringe for scanning.
Papilionidae
Attacus atlas
W = wings
W
W W
W
W
W
Funding and support from the BBC gratefully acknowledged.
Eye