The innate immune system in insects is composed of a large variety of specific and non-specific responses that are activated in response to the presence of foreign agents. One important element in such responses is the enzyme phenoloxidase (PO). Here, we review recent progress in PO research and discuss new applications in the emerging field of ecological immunology. Phenoloxidase produces indole groups, which are subsequently polymerized to melanin. The enzymatic reactions in turn produce a set of intermediate products such as quinones, diphenols, superoxide, hydrogen peroxide, and reactive nitrogen intermediates, which are important during defense against bacterial (gram+ and )), fungal, and viral agents. Phenoloxidase requires a complex system of activation and inhibition that involves various cell types, PO zymogens, inhibitor enzymes, and signaling molecules. Finally, research in evolutionary ecology has studied the costs of PO in terms of resource use and pleiotropic relations with other key traits and functions. These studies indicate that PO is a costly trait, whose production and maintenance have fitness costs for hosts. Phenoloxidase does not seem to be an indicator of resistance but rather of host condition. Finally, we put forward some basic directions for future investigation of PO aimed at explaining its activating system, its substrates, its coordination with other immune components to fight off pathogens, and variation in PO in relation to gender, life stages, seasonality, and across different host species.

Over the last ten years, Oosterhof and Todorov's valence-dominance model has emerged as the most prominent account of how people evaluate faces on social dimensions. In this model, two dimensions (valence and dominance) underpin social judgments of faces. Because this model has primarily been developed and tested in Western regions, it is unclear whether these findings apply to other regions. We addressed this question by replicating Oosterhof and Todorov's methodology across 11 world regions, 41 countries, and 11,570 participants. When we used Oosterhof and Todorov's original analysis strategy, the valence-dominance model generalized across regions. When we used an alternative methodology to allow for correlated dimensions we observed much less generalization. Collectively, these results suggest that, while the valence-dominance model generalizes very well across regions when dimensions are forced to be orthogonal, regional differences are revealed when we use different extraction methods, correlate and rotate the dimension reduction solution.

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Summary1. The terminal investment hypothesis has two predictions: in the face of an infection (i) mature males will increase investment to traits that increase mating success, while such investments will occur to a less extent in young males; and (ii) physiological costs of resource reallocation will be more severe for infected mature males than for infected young males. 2. Although these predictions have been tested in long-lived vertebrates, prior studies have not examined actual resource allocation conflicts. Here, we have tested the above predictions and have investigated the energetic costs of increased mating by old males, using a short-lived invertebrate, the damselfly Hetaerina americana. Males of this species defend territories as the main way to obtain access to females. 3. Using groups of infected vs. noninfected males of two different ages, we found that compared to young infected males, mature infected males defended territories for longer, had higher mating success and directed agonistic behaviour to conspecific males more frequently. Despite similar immune responses by mature and young males, infected mature males ended up with less fat reserves compared to infected young males. This suggests that resource allocation conflicts are more severe for mature than for young males. 4. In general, these results suggest that the terminal investment hypothesis applies in males of short-lived invertebrates and that a cause of increased mating success for males of advanced ages is reduced energetic stores.

Adaptive immunity allows vertebrates to gain protection against repeated pathogenic infections. Analogous responses (priming) have been recently uncovered in invertebrates. However, whether such responses are widespread is not known. The present study investigated the presence of immunological priming in males of a species whose phylogenetic position places it in one of the less derived insect orders. It is hypothesized that the efficiency of such a response could be related to animal condition, as assessed by the expression of a sexually selected ornament. Hetaerina americana Fabricius (Odonata: Calopterygidae) males bear a conspicuous ornament (a red wing spot), which is evolutionarily maintained via male territorial competition. Using field-collected animals, a group of males is challenged with bacteria before exposure to a higher dose of the same or a different bacteria, and survival is compared with that of infected males not previously challenged, as well as control groups. Grampositive and Gram-negative bacteria are used. To explore how long priming may take to work, the second exposure is carried out either after 1 or 5 days. Red spot and body size are entered in the analysis as predictors of survival within and between groups. There is no difference in survival among groups, which suggests no priming effect. Overall, red spot and body size are not consistent in explaining survival.

The immunocompetence handicap hypothesis (ICHH) states that hormones enhance sexual trait expression but impair immunity.Previous tests of the ICHH have been hampered by experimental design problems. Here, we report on an experimental test of the ICHH that includes manipulations of both hormones and infections in males of the territorial damselfly, Hetaerina americana, with accurate survival measurements. We conducted a fully factorial experiment subjecting each individual to one of three topical treatments: methoprene (a juvenile hormone analog), acetone, or control, and one of three injection treatments: bacteria, PBS, or control. We measured survival of manipulated males in both the wild and in captivity. As predicted, survival was most heavily impaired in methoprene-bacteria males than in the other groups in the wild, and no survival differences emerged in captive animals. This result confirms that survival is one cost an animal pays for increased hormonal levels. This corroborates theoretical predictions of the ICHH. K E Y W O R D S :Infection, insect, juvenile hormone analog, mark-recapture, Odonata, survival, sexual selection, trade-off.

if you think you are in control of your behavior, think again. evidence suggests that behavioral modifications, as development and persistence of depression, maybe the consequence of a complex network of communication between macro and micro-organisms capable of modifying the physiological axis of the host. Some parasites cause significant nutritional deficiencies for the host and impair the effectiveness of cognitive processes such as memory, teaching or non-verbal intelligence. Bacterial communities mediate the establishment of parasites and vice versa but this complexity approach remains little explored. We study the gut microbiota-parasite interactions using novel techniques of network analysis using data of individuals from two indigenous communities in Guerrero, Mexico. Our results suggest that Ascaris lumbricoides induce a gut microbiota perturbation affecting its network properties and also subnetworks of key species related to depression, translating in a loss of emergence. Studying these network properties changes is particularly important because recent research has shown that human health is characterized by a dynamic trade-off between emergence and self-organization, called criticality. emergence allows the systems to generate novel information meanwhile selforganization is related to the system's order and structure. in this way, the loss of emergence means a depart from criticality and ultimately loss of health.

Over the last ten years, Oosterhof and Todorov’s valence-dominance model has emerged as the most prominent account of how people evaluate faces on social dimensions. In this model, two dimensions (valence and dominance) underpin social judgments of faces. Because this model has primarily been developed and tested in Western regions, it is unclear whether these findings apply to other regions. We addressed this question by replicating Oosterhof and Todorov’s methodology across 11 world regions, 41 countries, and 11,570 participants. When we used Oosterhof and Todorov’s original analysis strategy, the valence-dominance model generalized across regions. When we used an alternative methodology to allow for correlated dimensions we observed much less generalization. Collectively, these results suggest that, while the valence-dominance model generalizes very well across regions when dimensions are forced to be orthogonal, regional differences are revealed when we use different extraction methods, correlate and rotate the dimension reduction solution.