The effects of food and parasitism on reproductive performance of a wild rodent

Abstract

Food and parasitism can have complex effects on small mammal reproduction. In this study, we tested the effects of sex, food, and parasitism on reproductive performance of the Taiwan field mouse (Apodemus semotus). In a field experiment, we increased food availability for a portion of the mice in the population by providing sorghum seeds to a set of food stations. We reduced parasite intensity of randomly chosen mice through ivermectin treatment. We determined the number and quality of offspring for the mice using paternity analysis. We quantified seed consumption with stable carbon isotope values of mouse plasma and parasite intensity with fecal egg counts of intestinal nematodes and cestodes (FEC). In a laboratory experiment, we reduced parasite intensity of randomly chosen mice through ivermectin treatment. We quantified their immune functions by total white blood cell count, percent granulocyte count, and percent lymphocyte count through hematological analyses. We measured the FEC and energy intake of the mice. From the field experiment, the number of offspring in A. semotus increased with increasing seed consumption. Due to the trade‐off between number and quality of offspring, the offspring quality decreased with increasing seed consumption for the females. The ivermectin treatment did not affect offspring number or quality. However, the FEC was positively correlated with number of offspring. In the laboratory experiment, the percent lymphocyte/granulocyte count changed with parasite intensity at low energy intake, which was relaxed at high energy intake. This study demonstrated positive effects of food availability and neutral effects of parasitism on A. semotus reproduction. However, the benefits of food availability for the females need to take into account the offspring number–quality trade‐off, and at high infection intensity, parasitism might negatively affect offspring quality for the males. We suggest that food availability could mediate the relationships between parasite intensity and immune responses.

Supplemented nutrition decreases helminth burden and increases drug efficacy in a natural host–helminth system

“…Increased resource availability can improve host condition and immunity resulting in reduced infection, but may also alter host behaviour and aggregation around food sources such that transmission is increased [ 33 ]. Although supplementation experiments have also been investigated in wild mouse models [ 7 , 34 , 35 ], these studies augmented resources of the same type as was available in the environment (e.g. seeds) rather than introducing supplemental food with additional micro- and macronutrients.…”

Neutral Forces and Balancing Selection Interplay to Shape the Major Histocompatibility Complex Spatial Patterns in the Striped Hamster in Inner Mongolia: Suggestive of Broad-Scale Local Adaptation

“…However, parasites can engender significant ecological and evolutionary interactions with both hosts and host populations [7]. Parasites thrive at the expense of other organisms by extracting energy from their hosts, potentially leading to reduced host condition and reproductive success [8,9]. Specifically, infections can initiate and facilitate local immunogenic adaptation, which relies on dissimilarities within the parasite community [10].…”

Embracing nature’s complexity: Immunoparasitology in the wild

“…While several wild rodent studies utilize anthelminthic treatment in order to understand the consequences of (co-)infection for host fitness, the interaction amongst parasites, or within-population transmission [ [78] , [79] , [80] , [81] , [82] ], the immune response has rarely been described in these studies. This is a clear opportunity for further immunological research, as anthelminthic treatment is the main and often only intervention for people living in parasite endemic areas.…”