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. 2013;8(1):e55007.
doi: 10.1371/journal.pone.0055007. Epub 2013 Jan 30.

Tapeworm Eggs in a 270 Million-Year-Old Shark Coprolite

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Free PMC article

Tapeworm Eggs in a 270 Million-Year-Old Shark Coprolite

Paula C Dentzien-Dias et al. PLoS One. .
Free PMC article

Abstract

Remains of parasites in vertebrates are rare from the Mesozoic and Paleozoic. Once most parasites that live in - or pass through - the gastrointestinal tract of vertebrates, fossil feces (coprolites) or even intestinal contents (enterolites) can eventually preserve their remains. Here we announce the discovery of a spiral shark coprolite from the Paleozoic bearing a cluster of 93 small oval-elliptical smooth-shelled structures, interpreted as eggs of a tapeworm.The eggs were found in a thin section of an elasmobranch coprolite. Most of the eggs are filled by pyrite and some have a special polar swelling (operculum), suggesting they are non-erupted eggs. One of the eggs contains a probable developing larva. The eggs are approximately 145-155 µm in length and 88-100 µm in width and vary little in size within the cluster. The depositional and morphological features of the eggs closely resemble those of cestodes. Not only do the individual eggs have features of extant tapeworms, but their deposition all together in an elongate segment is typical to modern tapeworm eggs deposited in mature segments (proglottids). This is the earliest fossil record of tapeworm parasitism of vertebrates and establishes a timeline for the evolution of cestodes. This discovery shows that the fossil record of vertebrate intestinal parasites is much older than was hitherto known and that the interaction between tapeworms and vertebrates occurred at least since the Middle-Late Permian.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Spiral heteropolar coprolite with cestode eggs.
Figure 2
Figure 2. Parasite eggs in a shark coprolite.
A - Thin section of the coprolite part containing clustered parasite eggs. B – Cestode eggs, the perfect oval shape hole were formed after the filling were reaped out from the coprolite during the lamination, the arrows show the operculum.
Figure 3
Figure 3. Cestode egg.
A - (photo) Cestode egg with a developing embryophore. B - (drawing) Partial reconstruction of egg in A. Abbreviations: C =  capsule or shell; E =  embryophore (ochosphere); H =  putative developing hooklets; I = inner envelope; M = oncospheral membrane; O = outer envelope; P = putative polar thickening; Op = operculum; S = somatic cells.

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Grant support

Financial support was provided by the Conselho Nacional de Desenvolvimento Científico e Tecnológico - Brazil (CNPq) through a study grant (PCD-D, AEQF and BH) and the Project 478914/2006-7 (Edital MCT/CNPq 02/2006 - Universal). This work was also partially funded by the Conselho Nacional de Desenvolvimento Científico e Tecnológico (http://www.cnpq.br/) through scholarships granted to AEQF, BH and CLS. The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

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