A tarantula's small beating heart has been imaged for the first time and revealed in real time with the help of a specialized MRI. Edinburgh University researchers used scanners built for medical research on rodents at the Glasgow Experimental MRI Centre to see into the living arachnid's gut as well.

The team colored the MRI images to highlight the tarantula's ticker, visible as lighter colors in the posterior part of the body. The image was acquired one slice at a time moving up the length of the spider's heart. In some of the slices—about five to 10 percent—the heart seemed to beat twice instead of once, suggesting that the tarantula might experience sudden unpredictable fluctuations in its heart rate at times, or "double beating."

This finding could result from a post-processing image reconstruction error, researcher Gavin Merrifield says, or it could be a real effect. Tests of the technique on cardiac function in rodents and in developing chicks inside eggs have yielded sensible results, however, he says, so the team is fairly sure that the former explanation is incorrect.

Merrifield presented the research at the Society for Experimental Biology annual conference in Glasgow on July 1.

The short video below shows the heart beating, with darker areas showing muscle or cardiac tissue and brighter areas showing blood.

—Ann Chin