Parasites in micromammal fecal pellets throughout the Late Holocene (“Cueva Peligro” paleontological site, Patagonia, Argentina)
Graphical abstract
Introduction
Micromammals perform vital ecosystems services and occupy an important place in food webs [[1], [2], [3]]. They are also one of the main components in the diet of predators [[4], [5], [6], [7], [8]]. Understanding the factors that influence the dynamic of populations and communities of micromammals is necessary to conserve biodiversity. Parasites are one of these factors that have interacted with the small mammals during their co-evolutionary history. One of the ways of revealing this history is through paleontological studies [9].
Micromammals are considered good bioindicators to perform inferences of paleoenvironmental conditions. In Patagonia Argentina there is some early background on this topic such as Pearson [10] and Pearson and Pearson [11,12]. In the last decades, there was an increase in the knowledge of Holocene micromammal fauna and their environmental significance [[13], [14], [15], [16], [17]]. Throughout most of the Holocene, micromammal communities from Patagonia have remained relatively stable. In contrast, dramatic changes in assemblage composition have been recorded during the last centuries. These changes can be due to anthropic impact and other variables such as climatic changes [[18], [19], [20]].
Hosts, parasites and the environment are in a state of constant flux, since a variation in one of them can affect any of the others [21]. The knowledge of the parasitic fauna present in the Holocene and how they varied throughout time helps to understand parasite and host ancient communities and the possible environmental factors that could have influenced this dynamic. Paleoparasitology is the discipline whose main objective is to study the origin and evolution of parasitic infections through archaeological and paleontological material [21]. Parasites remains can be detected in dried or mineralized coprolites, among others ancient materials [22]. There are some studies regarding parasite assemblages in micromammals in current times and, particularly in the fossil record. From paleontological and archaeological sites of South America, micromammal paleoparasitological studies were done exclusively in rodent species[23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33]. Therefore, the objective of the current study is to increase the knowledge about micromammal parasite assemblages and parasite-micrommamal relationship history in species from the paleontological site named “Cueva Peligro” from Patagonia, throughout the last 1200 years (Late Holocene).
Section snippets
Study area
The paleontological site “Cueva Peligro” (CP; 43°40′18”S, 66°24′52”W) is located near the southern margin of the Chubut River, about 6 km downstream of the Villa Dique Florentino Ameghino, Chubut Province, Argentina (Fig. 1A). The site is a cave emplaced on a rocky front of approximately 35 m of height (Marifil Formation, Jurassic), with a single entrance (4.57 m wide, Fig. 1B) and a single long gallery (ca. 30 m). The general dip of the floor of the cave is towards the outside, with some
Materials and methods
Fecal pellets belonging to 28 layers from CP were examined for paleoparasitological studies (13 layers belong to G1 and 15 layers to G2). The 14C dated of layers are shown in Table 1. The examination consisted of the external observation of faeces (color, texture, inclusions and measurements) according to Chame [38]. Five to ten coprolites were pooled in each sample depending on material availability. The coprolites were fully processed by rehydration in a 0.5% water solution of tris‑sodium
Results
Fecal pellets examined were cylindrical, dark brown, smooth and present a round extremity and the other one slightly tapered (Fig. 1D). The measurements were 5.15 ± 0.88 mm in length by 2.06 ± 0.31 mm in wide (n = 20) (Table 2). Microscopic analysis of the fecal material revealed an omnivorous to insectivorous diets. The diet varied between samples, possibly due to variation on item consumption or because they belong to different host species.
Eleven species of helminthes were recorded, eight
Discussion and conclusions
A previous paleoparasitological study of mountain viscacha fecal pellets over the last 1200 years was done in CP paleontological site [33]. In the present study, fecal pellets belonging to another micromammal species were studied for the first time. The microscopic observation of samples suggests an omnivore to insectivore diet of the host. According to the morphology of the samples, the host is restricted to rodent species [38]. Taking into consideration the small mammal species present in the
Funding
This research was founded by CONICET and ANPCyT (PICT – 2008-0547 and 2016-0316).
Acknowledgements
The site CP was detected by Analía Andrade and Daniel Udrizar Sauthier. Fieldwork was done with Pablo Teta, Julio Torres, Ulyses Pardiñas and Erica Cuellar assistance. We thank Claudio Iglesias, Piedra Grande S.A. and the Secretaría de Cultura de la Provincia de Chubut for permits to work in the area.
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