Composition and Function of Haemolymphatic Tissues in the European Common Shrew

Abstract

BackgroundStudies of wild animals responding to their native parasites are essential if we are to understand how the immune system functions in the natural environment. While immune defence may bring increased survival, this may come at a resource cost to other physiological traits, including reproduction. Here, we tested the hypothesis that wild common shrews (Sorex araneus), which produce large numbers of offspring during the one breeding season of their short life span, forgo investment in immunity and immune system maintenance, as increased longevity is unlikely to bring further opportunities for mating. In particular, we predicted that adult shrews, with shorter expected lifespans, would not respond as effectively as young animals to infection.Methodology/Principal FindingsWe examined haemolymphatic tissues from wild-caught common shrews using light and transmission electron microscopy, applied in conjunction with immunohistology. We compared composition and function of these tissues in shrews of different ages, and the extent and type of inflammatory reactions observed in response to natural parasitic infections. All ages seemed able to mount systemic, specific immune responses, but adult shrews showed some signs of lymphatic tissue exhaustion: lymphatic follicles in adults (n = 21) were both smaller than those in sub-adults (n = 18; Wald = 11.1, p<0.05) and exhibited greater levels of depletion (Wald = 13.3, p<0.05).Conclusions/SignificanceContrary to our expectations, shrews respond effectively to their natural parasites, and show little indication of immunosenescence as adults. The pancreas of Aselli, a unique lymphoid organ, may aid in providing efficient immune responses through the storage of large numbers of plasma cells. This may allow older animals to react effectively to previously encountered parasites, but infection by novel agents, and eventual depletion of plasma cell reserves, could both still be factors in the near-synchronous mortality of adult shrews observed shortly after breeding.

Storage of Blood in the Mammalian Spleen: an Evolutionary Perspective

“…The presence of this highly concentrated blood in this organ was then co-opted in mammals for a new function: release of blood cells into the circulation in response to a sudden demand of oxygen. Crile and Quiring 1940;de Oliveira et al 2013 Dasyprocta azarae 0.13 n/a n/a n/a no Herre et al 1996 Hydrochoerus hydrochaeris 0.20 n/a n/a n/a no Eberhardt et al 2015 Lagostomus maximus 0.10 n/a n/a n/a no Herre et al 1996 Microcavia australis 0.22 n/a n/a n/a no Herre et al 1996 Myocastor coypus 0.13 n/a n/a n/a no Mertin et al 2003 Sciuromorpha Eliomys quercinus 0.12 n/a n/a n/a Dicrostonyx groenlandicus 0.19 n/a n/a n/a yes Mallory et al 1986 Cricetulus migratorius 0.14 n/a n/a n/a Franceschi et al 1972;Cirri Borghi 1974 Soricomorpha Suncus etruscus 0.82 n/a n/a n/a no Bartels et al 1979 Suncus murinus 0.55 1 1 yes no Fukuta et al 1982;Tanaka 1990 Sorex araneus n/a 1 1 yes no Bray et al 2008 Sorex caecutiens 0.49 n/a n/a n/a no Kiselev et al 2014 Sorex isodon 0.53 n/a n/a n/a no Kiselev et al 2014 Sorex minutus 0.34 n/a n/a n/a no Nedosekina et al 2007 Crocidura russula 0.74 n/a n/a n/a no Bartels et al 1979;Sánchez-Chardi et al 2007 J RSW Relative splenic weight, n/a not available a splenic type follo...…”

Bioinformatic analysis of the spike protein cleavage sites of coronaviruses in the mammalian order Eulipotyphla

“…However, there are far fewer studies focusing on the Eulipotyphla mammals compared to the other insectivores like bats, which might cause the gap in understanding these small mammal host species. These small mammals, always living in a complex and densely populated community with rich species, also share similar biological characteristics of high metabolic rates (Bray et al, 2008; Han et al, 2016).…”