Dynamic spleen mass in wild and domestic American mink

Abstract

The immune system is considered to be an energetically expensive component of an individual's life history. Investment in the immune system can depend on the environment that an individual finds itself in. The American mink, Neovison vison, exists in the natural environment and on fur farms. The natural environment and mink farm differ in many ways, such as wild mink being exposed to many parasites that are less prevalent and less abundant in the domestic environment because of veterinary care. We collected free‐ranging mink from commercial trappers and domestic mink from fur farmers in Ontario and Nova Scotia, Canada, and examined relative spleen mass. Wild male mink had larger spleens than domestic mink in Nova Scotia, with a similar trend in Ontario. Female mink that escaped from farms (feral) in Nova Scotia had significantly larger spleens than their domestic counterparts on the farms. Both of these results are consistent with the prediction that the natural environment contains parasites and pathogens that require enhanced investment in the immune system. In Nova Scotia, females had larger spleens than males, whether considering wild or domestic populations. Finally, wild mink showed greater condition dependence of spleen mass than domestic populations. Further investigations should include experimental approaches such as providing veterinary care to wild populations to assess the effects of parasites and pathogens on the immune system. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 107, 624–631.

Aleutian Mink Disease Virus in Free-Ranging Mink from Sweden

“…A difference in relative spleen weight between the sexes was found in this study. This has been reported earlier [ 37 ] and the reason for the difference is not clear. In the male mink in this study, the relative spleen weight was associated with being AMDV positive and having AMDV antibodies, but not in the female mink (possibly due to a smaller sample size).…”

Stress and immunity at the invasion front: a comparison across cane toad (Rhinella marina) populations

“…Studies through time at a Northern Territory site showed higher rates of food intake and larger fat bodies in toads at the invasion front compared to the same site a few years later when density was higher (Brown et al ., ). The observed shift in spleen size could result either from a positive association with body condition or a negative association with parasite exposure (Vicente, Pérez‐Rodríguez & Gortazar, ; Schulte‐Hostedde, Bowman & Nituch, ). Although relative spleen size is often used as a gross measure of immunocompetence (Morand & Poulin, ; Corbin et al ., ; Koprivnikar & Leung, ), the causes and effects of mass variation are difficult to disentangle in an organ with such a multitude of functions (Smith & Hunt, ; Vicente et al ., ; Koprivnikar & Leung, ).…”

Assessment of Aleutian mink disease virus (AMDV) prevalence in feral American mink in Iceland. Case study of a pending epizootiological concern in Europe

“…Additionally, regardless of the infection females had higher spleen weight to body weight ratio than males. The difference of relative spleen weight between sexes has been reported elsewhere ( Schulte-Hostedde, Bowman & Nituch, 2012 ; Persson et al, 2015 ), but the reason for sexual disparity remains unclear. Moore & Wilson (2002) suggested a shift of energy resources towards reproduction and/or growth over the immune system in male mammals and immunosuppressive side effects of androgenic hormones.…”

“…The size of immune organs ( i.e., spleen, performing important immune functions) has been commonly used to describe animals’ investment in immunological response to various factors ( John, 1994 ; Schulte-Hostedde, Bowman & Nituch, 2012 ). In the study AMDV infected mink had significantly higher spleen weight to body weight ratio.…”