Aggression inTilapia affects immunocompetent leucocytes

A short note on how tied fights affect cortisol levels

Previous work exploring the interrelationships between sex steroids (e.g. androgens, testosterones and 11-ketotestosterones) and social behavior in teleosts suggest that mirror-elicited aggression in cichlid fish may not trigger a hormonal response. Using the Mozambique tilapia (Oreochromis mossambicus) to analyze immune responses as a result of social stress, we measured levels of cortisol and melatonin using Enzyme-Linked Immunosorbent Assay (ELISA) assays. In this work, we demonstrated that cortisol concentrations are significantly lower yet the levels of melatonin remain unchanged in tilapia that are fighting their mirror image. Our results suggested that in tied fights, certain hormone levels remain unchanged (e.g. androgens) due to the lack of melatonin induction.

Social status-dependent nest choice of territorial males under reproductive parasitism in a Lake Tanganyika cichlid Telmatochromis vittatus

Field and laboratory studies were conducted to examine how territorial males of a Lake Tanganyika cichlid Telmatochromis vittatus balance the conflicting demands on nest choice between occupying large nests with more females and avoiding reproductive parasitism (nest piracy, which is adopted by the largest males in the population). Pirates less frequently intruded the nests farther from neighbours, perhaps due to the costs associated with travelling between nests. The field experiment showed that territorial male T. vittatus sacrificed the fitness benefits that large nests offer and instead prioritized occupying the nests farther from neighbours on which fewer pirates intruded. The field observations suggested that they adopt different strategies for nest choice according to their relative competitive ability to pirates; the large territorial males, who are size-matched to pirates and can defend their nests against them, compete for larger nests among the more-isolated nests, whereas subordinate territorial males, which are smaller than pirates and thus inferior to them, compete for the more-isolated nests among the less-isolated nests. These findings suggest that the territorial male T. vittatus chooses the more-isolated nests to avoid pirate males at the expense of occupying large nests.

Interaction between endocrine and immune systems in fish

Diseases in fish are serious problems for the development of aquaculture. The outbreak of fish disease is largely dependent on environmental and endogenous factors resulting in opportunistic infection. Recent studies, particularly on stress response, have revealed that bidirectional communication between the endocrine and immune systems via hormones and cytokines exists at the level of teleost fish. Recently information on such messengers and receptors has accumulated in fish research particularly at the molecular level. Furthermore, it has become apparent in fish that cells of the immune system produce or express hormones and their receptors and vice versa to exchange information between the two systems. This review summarizes and updates the knowledge on endocrine-immune interactions in fish with special emphasis on the roles of such mediators or receptors for their interactions.

Cell adhesion and the immune system: a case study using earthworms

In the earthworm's immune system, cell adhesion, which occurs by putative receptors on leukocytes, is essential after recognition of self vs. non-self. Confrontation with foreign antigens is a normal event in the environment, replete with microbial pathogens that pose a threat to survival. To better understand what happens when an effector cell first recognizes a foreign target followed by its adhesion to it, isolated leukocytes, in sufficient quantities to be subjected to various analyses, have been extremely beneficial. In vitro approaches when accompanied by biochemical, immunological, and molecular technologies, have opened up new vistas concerning the immune response of earthworms and other invertebrates. The most recent discovery includes the preliminary identification of cell differentiation (CD) markers that play vital roles in recognitive and adhesive events. Certain leukocyte effectors show characteristics of natural killer (NK) cells that may act differently depending upon their source, whether autogeneic, allogeneic, xenogeneic, or expressed under normal or varying environmental conditions including exposure to xenobiotics. At the level of earthworm evolution, there is apparently a dissociation of phagocytosis from the process of killing by NK-like effectors. There are at least three future challenges. First, it is essential to determine the precise nature of the CD markers with respect to their molecular structure. Second, once their molecular and biochemical characteristics have been defined, the role of these markers in cellular and humoral mechanisms must be clarified in order to define effector cell products and resulting immune responses. Third, there is a need to differentiate between the several lytic factors that have been found in earthworms with respect to molecular structure, and biochemical and functional characterization.