Differences between sub-adults and adults were also evident in the so-called ''marginal'' or ''intermediate zone'' of the spleen, the variably distinct rim of macrophages, lymphocytes, neutrophils and erythrocytes surrounding follicles and follicle groups seen in S. araneus and previously described in other species, including the musk shrew [43, 47] . This zone is considered to be the site of most intensive blood filtration in the spleen [43, 47] , and its loss of integrity/intensity in older animals may indicate a reduction in filtration capacity. This might however be counterbalanced by an increase in the capacity of the peripheral phagocytic response, as represented by an increase in neutrophil numbers within both the spleen (as observed here) and the peripheral blood [46] .