Immune Defense Reduces Respiratory Fitness inCallinectes sapidus,the Atlantic Blue Crab

Abstract

Crustacean gills function in gas exchange, ion transport, and immune defense against microbial pathogens. Hemocyte aggregates that form in response to microbial pathogens become trapped in the fine vasculature of the gill, leading to the suggestion by others that respiration and ion regulation might by impaired during the course of an immune response. In the present study, injection of the pathogenic bacterium Vibrio campbellii into Callinectes sapidus, the Atlantic blue crab, caused a dramatic decline in oxygen uptake from 4.53 to 2.56 micromol g-1 h-1. This decline in oxygen uptake is associated with a large decrease in postbranchial PO2, from 16.2 (+/-0.46 SEM, n=7) to 13.1 kPa (+/-0.77 SEM, n=9), while prebranchial PO2 remains unchanged. In addition, injection of Vibrio results in the disappearance of a pH change across the gills, an indication of reduced CO2 excretion. The hemolymph hydrostatic pressure change across the gill circulation increases nearly 2-fold in Vibrio-injected crabs compared with a negligible change in pressure across the gill circulation in saline-injected, control crabs. This change, in combination with stability of heart rate and branchial chamber pressure, is indicative of a significant increase in vascular resistance across the gills that is induced by hemocyte nodule formation. A healthy, active blue crab can eliminate most invading bacteria, but the respiratory function of the gills is impaired. Thus, when blue crabs are engaged in the immune response, they are less equipped to engage in oxygen-fueled activities such as predator avoidance, prey capture, and migration. Furthermore, crabs are less fit to invade environments that are hypoxic.

Energy metabolism and metabolic depression during exercise inCallinectes sapidus, the Atlantic blue crab: effects of the bacterial pathogenVibrio campbellii

“…Despite having efficient mechanisms to enhance oxygen uptake during increased activity, crabs infected with Vibrio did not increase oxygen uptake to levels measured in control animals (Fig.4). These results are consistent with the idea that bacterial exposure impairs respiratory function in the blue crab because of the formation of hemocyte aggregates or nodules that become trapped in the gills (Johnson, 1976;Smith and Ratcliffe, 1980a;Martin et al, 2000;Burnett et al, 2006;Scholnick et al, 2006).…”

Effect of the copepod parasite Nicothoë astaci on haemolymph chemistry of the European lobster Homarus gammarus

“…Indeed, hypoxia can trigger elevated haemocyanin levels in several crustacean species (Hagerman & Pihl Baden 1988, Hagerman et al 1990). Moreover, in other crustacean species such as the blue crab Callinectes sapidus, injection of the pathogenic bacterium Vibrio campbellii results in haemocytes aggregating in the gill lamellae, thus restricting haemo lymph circulation and oxygen uptake through these narrow channels (Burnett et al 2006). Hence the cellular defence response (aggregation of haemocytes) caused by parasites and pathogens may cause temporary or permanent damage to the capacity of gaseous exchange in the gills, which the lobster attempts to compensate for by producing increased amounts of haemocyanin.…”

Shell disease of Neoepisesarma mederi crabs and its associated secondary infections

“…Circulating hemocytes play an extremely important role in the defense reactions by phagocytosis, hemocyte clumping, the production of reactive oxygen metabolites and the release of microbicidal proteins Chisholm, 1992, 2001;Smith et al, 2003). In addition, gills serve another important role in the immune response (Johnson, 1976a, b;White et al, 1985;Martin et al, 2000;Burnett et al, 2006). Johnson (1976a) provided histological evidence that nodule formation in response to stress-induced bacteremia in blue crabs might have adverse effects on gill function, including distention of gill lamellae and disruption of haemolymph flow.…”