Abstract
Although capacity to mount an efficient immune response plays a critical role in individuals’ survival, its dynamics across ontogenetic stages is still largely unexplored. Life stage-dependent variation in the encountered diversity and prevalence of parasites were proposed to contribute to stage-dependent changes in immunity, but differences in life history objectives between developmental stages may also lead to stage-specific changes in efficiency of given immune mechanisms. The reason for this is that juveniles and subadults are unable to reproduce, therefore they invest resources mainly into survival, while adults have to partition their resources between survival and reproduction. The general trade-off between somatic maintenance and reproductive effort is expected to impair immune function. Especially so in semelparous organisms that only reproduce once throughout their lifetime, hence they do not face the trade-off between current and future reproduction. We hypothesised that in a semelparous species individuals would be characterised by decreased investment into somatic maintenance after maturation, in order to maximise their reproductive output. Accordingly, we predicted that (1) elements of somatic maintenance, such as immunity, should be relatively weaker in adults in comparison to subadults, and (2) increased reproductive investment in adults should be associated with lower immune efficiency. We quantified two markers of immunity in subadult and adult individuals of the semelparous wolf spider Pardosa agrestis (Westring, 1861), namely bacterial growth inhibition power and bacterial cell wall lytic activity. We found that subadults showed significantly higher cell wall lytic activity than adults, but the two life stages did not differ in their capacity to inhibit bacterial growth. Also, we found weaker immune measures in mated females compared to virgins. Furthermore, in mated females bacterial growth inhibition power was negatively associated with fecundity.
Highlights
The capacity to effectively respond to antigens to minimize fitness costs of infection (Owens & Wilson, 1999) is a critically important element of somatic maintenance
Using the above described assays we investigated whether subadult and adult individuals of P. agrestis differ in the bacterial growth inhibition power and cell wall lytic activity, i.e. in the maintained capacity to mount either a complex, or a simpler, immediate immune response against microbial infection
Our results show that in a semelparous species adults are characterised by lower cell wall lytic activity in comparison with subadults, but we found no evidence for subadults and adults to differ in their bacterial growth inhibition power
Summary
The capacity to effectively respond to antigens to minimize fitness costs of infection (Owens & Wilson, 1999) is a critically important element of somatic maintenance. 2005), considerable variation persists in the efficacy of immune functions in natural populations (Brinkhof et al, 1999; Norris & Evans, 2000; Calsbeek, Bonneaud & Smith, 2008). Until recently numerous studies were carried out in this subject (reviewed in: Sheldon & Verhulst, 1996; Lochmiller & Deerenberg, 2000; Harshman & Zera, 2007; Cotter et al, 2008; Sadd & Schmid-Hempel, 2009; Crino et al, 2013; Palacios, Cunnick & Bronikowski, 2013; Park & Stanley, 2015), mainly focusing on the variability of adult immunocompetence, and the effects of juvenile-experiences (such as immune-challenge or nutritional deficiency) on adult immunocompetence (Norris & Evans, 2000; Ricklefs & Wikelski, 2002; Jacot et al, 2005; Stoehr & Kokko, 2006; Martin, Weil & Nelson, 2007; DeBlock & Stoks, 2008; Kriengwatana et al, 2013; Gilbert, Karp & Uetz, 2016). Still surprisingly little is known about how the baseline efficiency of the immune system changes through the different life stages
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