Longitudinal in vivo MR imaging of live earthworms

Abstract

Earthworm (Oligochaeta, Lumbricidae) species are used widely in eco-toxicological tests especially with contaminated soils. These long-term tests are reliable, but a high sample size is needed. Magnetic resonance imaging (MRI) can produce fast, robust, sensitive, and longitudinal morphological results using a small sample size. Performing longitudinal in vivo examinations of earthworms using MRI requires the need for anesthetics to completely avoid earthworm's moving. Our goal was to develop a simple and non-invasive method to anesthetize earthworms for in vivo longitudinal imaging studies. We investigated a number of different anesthesia methods and found that propan-2-ol and its vapor was optimal. We used a commercial sequential nanoScan® PET/MRI system (Mediso Ltd, Hungary, Budapest) to explore feasibility of MR imaging in immobilized earthworms. It was possible to visualize via micro MRI the brain, gastrointestinal tract, seminal vesicles, calciferous gland (Morren gland), and main blood vessels of the circulatory system. Our findings show the possibilities to examine changes in morphology using MRI of certain organs using a reversible, long-term immobilization method.

The orientation of earthworms is influenced by magnetic fields

“…Earthworms are a key invertebrate, having a function in the ecosystem as ecosystem engineers building large and resistant organomineral structures which affect the environment of smaller organisms in the soil (Giller et al, 1997). Due to their ecological importance as key organisms in soil ecology, the dispersion and movement of earthworms has interested many researchers, in addition to their effects on abiotic entities, such as soil moisture and temperature, soil organic matter content, soil texture, bulk density, pH values, and soil moisture content (Cannavacciuolo et al, 1998;Whalen and Costa, 2003;Decaëns and Rossi, 2008;Valckx et al, 2010), biotic factors such as individual behavior and food consumption (Shipitalo et al, 1988), and the combination of these factors influencing the movement of earthworms (Martin and Lavelle, 1992;Palm et al, 2013;Budán et al, 2014;Wetzel et al, 2016). Their distribution patterns have also been well-defined by agroecosystem models (Palm et al, 2013).…”