Rare and early evidence of a kleptoparasite

Palaeontologists say they have uncovered the oldest known record of a parasite/host relationship.

While analysing a fossil population of the Cambrian brachiopod Neobolus wulongqingensis discovered in Yunnan, China, and dating from around 512 million years ago, they found many covered with a tube-dwelling organism.

Those that were encrusted were significantly smaller than the others, and the tubes were aligned with the brachiopod’s own feeding currents, but there was no evidence of boring into the interior of the brachiopod.

In addition, the tubes are not found attached to any other hosts or substrates, and there was no evidence to suggest the organisms could adopt a free-living lifestyle in the absence of their host.

This led the researchers to suggest – in a paper in the journal Nature Communications – that the organism was a kleptoparasite that reduced its host’s fitness by stealing its food. 

That makes it a rare find, as parasitic interactions are difficult to document in the fossil record because most inferences have to be made based on appearance.

The study was led by Zhifei Zhang from China’s Northwest University and involved researchers from China, Sweden and Australia. 

“Our analyses demonstrate that the tube-dwelling organism directly impinges upon the biological fitness of the host, supporting the assertion that the encrusting tube-dwelling organisms are parasitic, rather than being either mutualistic or commensal with the brachiopod host,” they write in their paper.

“A reduction in host biomass or growth rate has been directly attributed to the presence of a parasite in a variety of extant symbiotic relationships.

“Parasites typically increase the energetic requirements of infected organisms, as the host must generate sufficient energy to not only maintain its own requirements but also the needs of the parasite. This commonly leads to hosts with decreased biomass when compared with uninfected individuals.

“This result represents the first definitive and statistically supported instance of parasitism from the Cambrian…”

Brachiopods are small shell-like marine animals that resemble bivalve molluscs. There are about 450 living species, but more than 12,000 are known from the fossil record.