Azurocytes in Wild Field Voles: Factors Associated with Their Occurrence

Abstract

The occurrence of azurocytes (AZ), a type of leukocyte unique to voles and previously described for three Microtus species, is now reported in Microtus agrestis. The goal of this study was to shed new light on the possible function and significance of these cells and on how they play a role in the natural history of rodent species. Individuals from three vole populations were sampled monthly for 2 years. A hemogram was produced for each individual, and AZ counts estimated. The counts of AZ were much higher in pregnant females, and these levels were higher the higher the past vole density. Males had low prevalences and counts, both for breeding and nonbreeding individuals, but they showed a seasonality that varied with age, body condition, and current and past vole density. Also, the occurrence of AZ in males was more likely after they had had low levels of indicators of condition, suggesting that azurocytes may result from a response to infection. Hence, overall our results suggest that, in females, these cells may be important for reproduction and may have a role in inducing abortion when conditions are not favorable, while in males they might be a response to infection.

Dynamics of health of wild capybaras: biochemical and physiological parameters

“…Again, this is coincident with the findings of azurocytes in field voles (Beldomenico et al 2008b). This suggests that in males, KCs may play a role in the protection against infections as their levels could be raised by antigenic stimulation (Revell 1977).…”

“…Another particular lymphoid cell, the azurocyte, was found in the blood of microtine rodents (voles) (Beldomenico et al 2009, Mihok et al 1987). Azurocytes were found in much higher levels in pregnant female voles than in nonpregnant females and males (Beldomenico et al 2008b). This similar behavior suggests that KCs and azurocytes may be functionally related, carrying out a specific task during pregnancy.…”

“…If KCs play a role in resorption, this could explain why female KC levels were much higher in cold and dry months (autumn-winter) than in spring-summer. Beldomenico et al (2008b) also proposed that azurocytes might be implicated in embryo resorption during times of hardship. Although specific functions of KCs in capybaras should be investigated, our results hint that KCs might play a major role in innate immunity during capybara pregnancy, particularly at the advanced stages.…”

Host–parasite biology in the real world: the field voles of Kielder

“…They are particularly common in late pregnancy and inducible by progestins both in males and females (Mihok et al 1987; Mihok and Schwartz, 1991). Beldomenico et al (2008 c ) found that the counts of AZ were indeed much higher in pregnant females, and that these counts were positively correlated with past vole density. Males had low prevalences and counts, both for breeding and non-breeding individuals, but they showed a seasonality that varied with age, body condition, and current and past vole density.…”

In This Issue

“…This conclusion was further supported by changes identified in caterpillar abundance and the diet of nestlings along the pollution gradient. Beldomenico et al (2008) report on their longitudinal study of three populations of wild field voles (Microtus agrestis) to ascertain the factors associated with the occurrence of a type of white blood cells unique to voles, azurocytes. Their findings clarify the functional significance of these cells and their role in the natural history of rodent species.…”