Respiratory Responses of the Blue Crab Callinectes sapidus to Long-Term Hypoxia

Abstract

Blue crabs (Callinectes sapidus) were held in hypoxic (50-55 mm Hg) water for 7-25 days. Postbranchial blood PO2 fell by about 80% within 24 h and then remained unchanged. Postbranchial blood total CO2 increased within 24 h and remained elevated for the duration of the experiment. There was no change in postbranchial blood pH, osmolality, or Cl. Lactate, urate, and Ca+2 all raise the O2 affinity of blue crab hemocyanin; by 25 days, blood lactate and urate had risen slightly, but Ca+2 had increased dramatically. Hemocyanin concentration had also increased by 25 days. At both 7 and 25 days there was an intrinsic increase in hemocyanin-O2 affinity and a change in subunit composition. The highly adaptive homotropic change is believed to be due to an attendant shift in the proportions of two of the three variable monomeric hemocyanin subunits. Thus, both heterotropic and homotropic adaptations enhance blood oxygenation at the gill during long-term hypoxia.

Effects of pot fishing on the physical condition of snow crab (Chionoecetes opilio) and southern Tanner crab (Chionoecetes bairdi)

“…The [Hc] in the hemolymph of individual crabs was estimated with an established spectrophotometric method (Nickerson and Van Holde, 1971;deFur et al, 1990). An aliquot of serum was diluted by 50 mmol L -1 Tris HCl, containing 10 mmol L -1 EDTA, pH 8.9…”

“…Halftimes for clearance of 125 I-labeled Hc have been reported to be 25.5 and 36 days in American lobster (Homarus americanus) and Caribbean spiny lobster (Panulirus argus) (Senkbeil and Wriston, 1981). A more rapid synthesis of Hc can be induced by various environmental factors, such as changes of ambient salinity (Gilles, 1977;Péqueux et al, 1979) and by moderate chronic hypoxia (Hagerman and Baden, 1988;deFur et al, 1990;Spicer and Baden, 2001).…”

The molecular heterogeneity of hemocyanin: Its role in the adaptive plasticity of Crustacea

“…Numerous studies have shown that different sets of subunits determine distinct oxygen-binding affinities as evidence of the extensive functional variability (Mangum and Rainer, 1988;DeFur et al, 1990;Mangum, 1994;Spicer and Hodgson, 2003a,b). Also a plastic regulation of cooperative transition is provided by subunit heterogeneity as shown in P. interruptus.…”

“…Moreover, while variations in Hc concentration are common to almost all Crustacea, the regulation of expression of individual monomers appears to be strictly species-related, and it conclusively accounts for the intra-specific Hc heterogeneity. In particular, it has been demonstrated that a change in Hc phenotype by means of differential expression of one or more subunits are a consequence of a defined physico-chemical stimuli and produces a shift in O 2 -binding affinity (Mason et al, 1983;Mangum and Rainer, 1988;DeFur et al, 1990;Mangum, 1994;Spicer and Hodgson, 2003b). This phenomenon has been intensely investigated in two species: the blue crab C. sapidus and the amphipod C. marinus.…”

“…Exposure to different salinity regimes, both in field and in laboratory, have been proved to modify the subunit composition in C. sapidus (Mason et al, 1983) and C. marinus (Spicer and Hodgson, 2003b), respectively. Further studies on C. sapidus, have pointed out the effect of environmental hypoxia as determinant of Hc phenotype (DeFur et al, 1990;Mangum et al, 1991;Mangum, 1994;Brouwer et al, 2004). However, in addition to the clear evidences on the individual effect of salinity and hypoxia, a possible synergic effect of the two environmental parameters, as well as the influence of other factors (e.g.…”