Structural and functional heterogeneity of hemocyanin: intra- and inter-specific comparison in four species of portunid crabs (Crustacea: Portunidae)

Abstract

This work is focused on hemocyanin (Hc) heterogeneity at population level and on the biochemical characterization of the different subunit patterns. Two different approaches have been used: we have characterized Hc subunit composition to describe the subunit polymorphism. Then, we have measured the Hc oxygen-binding affinity to disclose the physiological implications of such heterogeneity. In order to evaluate the intra-and inter-specific variability, different populations of Liocarcinus depurator, Liocarcinus marmoreus, Liocarcinus holsatus, Necora puber (Crustacea: Portunidae), from British Isles and Adriatic Sea, have been sampled. Results indicate that Hc polymorphism normally occurs at both intra-and interspecific levels and involves the protein subunit type.These evidences extend to the portunid Hc the concept of molecular heterogeneity within species that have been previously reported for other decapod and amphipod crustaceans. Besides, the results support the view that subunit composition of crustacean Hcs is almost species-specific, but also that closely related species share a common pattern. Furthermore, this heterogeneity corresponds to different stability of the native oligomers quaternary structure and different oxygen affinity. The results are discussed in relation with the environmental regimes that characterize the different sampling areas. In addition to Hc, the hemolymph collected in specimens from different sampling areas contained also a non-respiratory pseudo-Hc. This paper reports for the first time the occurrence of pseudo-Hc at the level of population.

Onset of and recovery from physiological stress in Liocarcinus depurator after trawling and air exposure under different seasonal conditions

“…Exposure to air at high temperature does not appear to be sustainable for this species, though some mechanism of adaptation to hypoxic stress may exist, at least at the population level. For instance, heterogeneity in the composition of the subunits of haemocyanin, the oxygen transport protein, has been described in different populations of Liocarcinus spp., resulting in different oxygen binding properties (Giomi et al, 2007). All of this could play an important role at the population level in determining the abundance of this species within its main fishing grounds.…”

Coping with cyclic oxygen availability: evolutionary aspects

“…1) and, while atmospheric oxygen has remained near present atmospheric levels (21%) for the past 600-700 million years, there were prolonged episodes of both atmospheric hypoxia and hyperoxia in the Late Paleozoic (Ward et al 2006;Berner et al 2007). The evolutionary significance of both the initial rise in oxygen, as well as the Late Paleozoic fluctuations, holds increasing scientific interest, particularly when viewed in the context of the numerous and diverse examples of respiratory adaptations to periodic hypoxia that have been documented for extant species as a result of either changes in activity level or in habitat conditions (Lee et al 2005;Gerlach et al 2006;Giomi et al 2007;Fig. 2).…”

“…The plasticity of their respiratory system, with particular reference to the modulation of oxygen transport, allows crustaceans to sustain selective pressures of extremely variable environments (Bridges 2001). Recent biochemical investigations on ''respiratory plasticity'' in portunid crabs, imply a distinct respiratory role for the oxygen-transporting molecule hemocyanin (Giomi et al 2007). Subunit changes in this copper-containing respiratory pigment have been previously linked to alterations in oxygen transport and to gene regulation (Terwilliger and Dumler 2001).…”

“…Subunit changes in this copper-containing respiratory pigment have been previously linked to alterations in oxygen transport and to gene regulation (Terwilliger and Dumler 2001). Also, electrophoretic and chromatographic data for the crabs Carcinus aestuarii and Liocarcinus depurator in the North Adriatic sea demonstrate marked, population-level differences in the composition of hemocyanin subunits and these in turn correlate with seasonal effects on, and regional differences in, environmental oxygen level and thus point to the plasticity of respiratory responses that may occur among distinct populations (Giomi et al 2007). Finally, experimental emersion of the semi-terrestrial species Carcinus aestuarii reveals the integration of molecular traits such as the allosteric modulation of hemocyanin for air breathing and morphological features such as gill structure (Giomi et al 2007).…”

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

“…The species specificity of subunit pattern is differently evident among crustacean families. As an example, a recent comparative analysis performed on portunid crabs shows that closely related species share a common subunit pattern (Giomi et al, 2007).…”