ABSTRACT
We investigated extracellular and intracellular digestion in bivalves, employing magnetic resonance imaging (MRI). Ruditapes philippinarum clams and Mytilus galloprovincialis mussels were incubated in seawater containing a contrast reagent [gadolinium-diethylenetriamine pentaacetic acid (GdDTPA)] at 20°C. The digestive systems, from the esophagus to the rectum, were visualized at a high signal intensity by the T1-weighted MRI. The crystalline style of the clam was also identified, which turned counterclockwise when viewed from a ventral–posterior position at a rate of 16 revolutions min−1. Determined using the T1 relaxation rate, the uptake and excretion rates of the GdDTPA in the mussel's digestive glands were 2.9 and 0.25 day−1, respectively, indicating that intracellular digestion in the gland acinar cells is slower than extracellular digestion. These results demonstrate that MRI with contrast reagents is useful to study the activity of the digestive system in bivalves, and that this technique could be applied to study other invertebrates.
Footnotes
Author contributions
Conceptualization: E.S., Y.S.; Data curation: E.S., Y.S.; Funding acquisition: E.S., Y.S.; Investigation: E.S., Y.S.; Methodology: E.S., Y.S.; Resources: E.S., Y.S.; Validation: E.S., Y.S.; Writing – original draft: E.S., Y.S.; Writing – review & editing: E.S., Y.S.
Funding
This work was supported by the National Institute for Basic Biology Collaborative Research Program (23NIBB521 and 24NIBB518 to E.S. and Y.S.) and Japan Society for the Promotion of Science KAKENHI (JP24659102 to Y.S.).
Data and resource availability
All relevant data and details of resources can be found within the article and its supplementary information. The 3D MR images are also available from the corresponding author on request.
Special Issue
This article is part of the special issue ‘The Integrative Biology of the Gut’, guest edited by Carol Bucking, Matt Regan and John Terblanche. See related articles at https://journals.biologists.com/jeb/issue/228/14.
