Finding traces of food and guts in 588 million years old Ediacaran-type critters

Guts, gut contents, and feeding strategies of Ediacaran animals.

Summarized by Nilmani Perera, a graduate student in the PhD program at the Geological Sciences program at the University of South Florida. She’s studying evolutionary patterns of Paleozoic (542–251 million years ago) echinoderms with Dr. Sarah Sheffield. She’s also interested in looking into their paleoecology and how it could have played a role in their diversification during this time. 

What was the hypothesis being tested (if no hypothesis, what was the question or point of the paper)?  This study focuses on understanding how Ediacaran animals fed, using three 558-million-year-old fossils from the White Sea area in Russia.

What data were used? Three different fossilized animals were used in this study; Kimberella, Calyptrina and Dickinsonia; Figure1). Rocks containing fossils and surrounding sediment from White Sea area in Russia were analyzed for the presence of fat molecules (lipid biomarkers) that came from their diet.

Methods: Fossils  and sediment collected in the field were prepared and then analyzed using Gas chromatography–mass spectrometry (GC-MS). This is a method used to separate components in a mixture at very fine level, basically at the molecular level. Fat particles in the samples were separated based on their differences in chemistry. Researchers looked for the presence of specific combination of lipid molecules in these samples, which can indicate the origin of the molecules. Comparing the ratios of the different types of molecules allowed them to figure out whether the signal came from the actual organisms or from the surrounding rock. This also allowed researchers to determine if the organism had a digestive tract (also referred to as gut) inside its body

Results: There were several significant findings that came out of this study. First, researchers discovered that the lipid breakdown process in Kimberella and Calyptrina is the same as in modern invertebrates, such as mollusks (like clams) and worms. Secondly, they were able to point out that Kimberella grazed on microbial mats and Calyptrina fed on particles in the sea water or in the marine sediment, like modern day tube worms would do. Thirdly, it was shown that both these organisms had a gut in which their food was digested. Interestingly, none of the specimens of Dickinsonia studied indicated that they possessed a gut, so they either took in food particles by osmosis (where particles move across a membrane) or could have possessed an external digestive system in which they secreted enzymes into the environment to breakdown food and then absorb it through their body. 

The figure contains three Ediacaran animals preserved in rock as fossilized impressions. A. The first figure is of Kimberella, preserved in a light gray color rock and is roughly half an inch long. It is pear-shaped, flat and has a couple of layers to it. B. The second figure is of Dickinsonia, preserved in a light brown color rock. It is leaf-like with ridges radiating from a central axis and about 3.5 inches along its length. C. The third figure is of Calyptrina, preserved on the surface of a beige color rock. It is flat, long, and worm-like with some dark color patches along its length.
Figure 1; Ediacaran fossils used in this study. A. Kimberella, B. Dickinsonia, C, Calyptrina (Scale bar used in Figures A, 5mm; B, 10mm and C, 5mm)

Why is this study important? The findings of this study are important because there’s a lot of research going on to understand how earliest animals evolved and how similar they were to animals we see today. Ediacaran- age animals represent an important turning point in the study of how animal bodies came about and how similar they are to major animal groups we see today. In this study, the lipid molecules preserved with the fossils  allowed researchers to compare them to modern animals with similar life modes. 

Broader Implications beyond this study: This method of biomarker identification can be applied to learn more about the trophic structure in ecosystems that are hundreds of millions of years old. The beauty of it is that this method can be used even when the gut is not preserved, because the method is only using the lipid molecules derived from the diet. 

Citation: Bobrovskiy, I., Nagovitsyn, A., Hope, J.M., Luzhnaya, E., & Brocks,J.J.,  (2022). Guts, gut contents, and feeding strategies of Ediacaran animals. Current Biology, 32, 5382–5389.