Phagocytosis by invertebrate hemocytes: Causes of individual variation in Panorpa vulgaris scorpionflies

Abstract

An in vitro phagocytosis assay, adjusted to as little as 1 microL of insect hemolymph, enables the microscopic determination of phagocytosis for single individuals of small insects. Even repeated determination over the lifetime of individuals is possible. This method makes it feasible to study individual variation in invertebrate phagocytic capacity. Possible sources of such variation are reviewed in this article: genetic differences, development, aging, reproduction, presence of parasites, and diverse environmental influences are natural sources of individual variation in phagocytosis. However, the methods used for phagocytosis and microscopic evaluation are also (unwelcome) sources of variation. To optimize incubation time for in vitro phagocytosis, time courses were determined. Furthermore, the reliability of visual counting and image analysis for the microscopic quantification of phagocytosis are compared. The influences of larval development and adult aging on phagocytosis by Panorpa vulgaris hemocytes are subsequently demonstrated. During development, a decrease in hemocyte numbers but a simultaneous increase in the proportion of phagocytosing hemocytes was observed when larvae reached pupation. On the other hand, adults showed a dramatic decrease in phagocytic capacity with age, while cell numbers remained fairly constant. The results show that individual variation in phagocytosis can be determined accurately in small invertebrates and related to its causes. This might be especially interesting in the context of studies relating individual immunocompetence to ecology, life history variation, and behavior.

The development of pathogen resistance in Daphnia magna: implications for disease spread in age-structured populations

“…For example, our data highlight that there is extensive genetic variation for a late-life decline in defensive ability, which might reflect immunosenescence. Studies on other organisms have supported the theory that immunocompetence generally decreases with advanced age in invertebrates (Adamo et al, 2001;Doums et al, 2002;Kurtz, 2002;Laws et al, 2004;Prasai and Karlsson, 2012;Whitehorn et al, 2011;Zerofsky et al, 2005), but, as with the current results, there also exist examples of genetic variation for immunosenescence or where immunocompetence increases with age (Felix et al, 2012;Khan and Prasad, 2013;Lesser et al, 2006). Assuming that, in the wild, different strategies might be favoured at different times, or in different locations, this genotype × age interaction indicates a mechanism by which genetic variation may be maintained in natural populations.…”

“…What has been little studied, however, is the basic ontogeny of immunity early in the life of invertebrates. Changes in the immune system later in life (and immunosenescence in particular) have received considerable attention (Adamo et al, 2001;Doums et al, 2002;Eleftherianos et al, 2008;Felix et al, 2012;Kurtz, 2002;Laws et al, 2004;Lesser et al, 2006;Piñera et al, 2013;Prasai and Karlsson, 2012;Sorrentino et al, 2002;Whitehorn et al, 2011;Zerofsky et al, 2005), but few studies have included the first days of an invertebrate's life. The main aim of the present study was to shed light on the development of the defence system of an invertebrate, the crustacean Daphnia magna Straus, under tight experimental control.…”

Adult honeybees (Apis mellifera L.) abandon hemocytic, but not phenoloxidase-based immunity

“…Kurtz (2002) considered the changes of hemocyte numbers and phagocytic capacity in the scorpionfly Panorpa vulgaris. During larval development, total hemocyte number decreased, while number of phagocytosing hemocytes increased.…”

A summer heat wave decreases the immunocompetence of the mesograzer, Idotea baltica

“…About 2 l of the outXowing hemolymph was collected into a 2-l microcapillary, Xushed into a 0.2-l Eppendorf tube and immediately frozen in liquid nitrogen. Thereafter, 2 l of heat-killed Bacillus thuringiensis (concentration: 10 8 cells/ml) dissolved in insect Ringer saline solution and labelled with FITC after standard protocols (Kurtz 2002) were injected into the animals using the same hole that was already punctured for taking hemolymph, to perform an in vivo phagocytosis assay. After injection of bacteria, the animals were immediately put back into the vials that were then placed into the aquaria facilities for 2 h (beforehand, lid was punctured with a needle to allow water exchange).…”