Arthropod hemocyanins and phenoloxidases serve different physiological functions as oxygen transporters and enzymes involved in defense reactions, respectively. However, they are equipped with a structurally similar oxygen-binding center. We have shown that the clotting enzyme of the horseshoe crab, Tachypleus tridentatus, functionally converts hemocyanin to phenoloxidase by forming a complex w...

Toxic metals, such as tributyltin (TBT), contribute substantially to anthropogenic pollution in many estuarine environments. Animals that live in those environments, particularly invertebrate filter feeders like tunicates, are likely to be exposed to substantial metal contamination. This study investigates the effects of TBT and other metals on the phenoloxidase activity of the estuarine tunica...

Insect immune defenses include encapsulation and the production of lysozymes and phenoloxidase. However, the highly mobile larvae of parasitoid Ormiine flies (Ormia ochracea) can evade initial encapsulation, and instead co-opt host immune responses to form a critical respiratory funnel connecting them to outside oxygen. Here we ask how field crickets (Teleogryllus oceanicus) respond immunologic...

In this study the cellular and humoral immune reactions of the Greater wax moth Galleria mellonella have been investigated during bacterial infection caused by oral administration of Bacillus thuringiensis. Two different dose strengths were investigated to assess the contribution of immune parameters to induced Bt resistance. Low-dose (sublethal LC15) infection resulted in significantly elevate...

Using microtitration method, the relationship between Phenoloxidase activity and the resistance of the diamondback moth Plutella xylostella (Linnaeus) to the novel insecticide butane-fipronil was determined in vitro. After selection of the tenth-generation by butane-fipronil, the resistance of the fourth instar larvae was increased 83.80-fold as compared to the susceptible strain. Phenoloxidase...

Latent phenoloxidase activity of hemocyanin (Hc) in whiteleg shrimp Penaeus vannamei was assayed to determine its potential involvement in postmortem melanosis. Conversion of pure 12-mer, but not 6-mer, hemocyanin to phenoloxidase by endogenous (serine proteinases) and exogenous (SDS) effectors demonstrated the need of complex aggregation for displaying enzyme activity. Because Hc was converted...

Contact reaction is the morphological expression of allogeneic recognition by hemocytes in the ascidian, Halocynthia roretzi; namely they undergo an exocytotic burst upon contact with non-self (allogeneic) hemocytes in vitro. We have found that contact reaction is accompanied by a burst of cyanide-insensitive oxygen consumption that, unlike exocytotic events of mammalian phagocytes, is Ca(2+)-d...

In Locusta migratoria, activation of phenoloxidase in the haemolymph in response to injection of laminarin is age-dependent: being absent in fifth instar nymphs and newly emerged adults, and only becoming evident four days after the final moult. This pattern of change in phenoloxidase activation correlates with the pattern of change in the concentration of apolipophorin-III (apoLp-III) in the h...

The melanization reaction induced by activated phenoloxidase in arthropods must be tightly controlled because of excessive formation of quinones and excessive systemic melanization damage to the hosts. However, the molecular mechanism by which phenoloxidase-induced melanin synthesis is regulated in vivo is largely unknown. It is known that the Spätzle-processing enzyme is a key enzyme in the pr...

To improve thermoregulation in colder environments, insects are expected to darken their cuticles with melanin via the phenoloxidase cascade, a phenomenon predicted by the thermal melanin hypothesis. However, the phenoloxidase cascade also plays a significant role in insect immunity, leading to the additional hypothesis that the thermal environment indirectly shapes immune function via direct s...