Asymmetric hemoglobins, their thiol content, and blood glutathione of the scalloped hammerhead shark, Sphyrna lewini

Hematologic, plasma biochemistry, and select nutrient values in captive smooth dogfish (Mustelus canis)

The Indianapolis Zoo maintains a large collection of smooth dogfish (Mustelus canis). During the first several years of captivity, there was a period of high mortality in adult, wild-caught sharks in the collection. Smooth dogfish with superficial abrasions would rapidly succumb to infection and death, regardless of the treatment approach. Although the sharks did successfully produce viable offspring, there was an elevated pup mortality rate, with 0% of the pups reaching 1 yr of age during the same period of high mortality in adult sharks. This poor response to captivity prompted interest in the physiologic response of these animals to illness. The objective of this investigation was to establish a preliminary data set of hematologic and plasma chemistry reference intervals, along with select nutrient parameters specific to wild-caught adults maintained in prolonged captivity (i.e., greater than 22 mo). Blood samples were collected from 20 clinically healthy, male (n = 10) and female (n = 10) dogfish sharks at the Oceans facility at the Indianapolis Zoo. Although gender differences in mortality rate were not apparent, complete blood cell counts, plasma biochemical profiles, and select nutrient analyses were performed and analyzed accordingly. Statistically significant differences (P < or = 0.05) specific to sex were determined for parameters including packed cell volume (PCV), absolute and relative fine eosinophilic granulocytes, relative percentage of coarse eosinophilic granulocytes, globulins, the albumin/globulin ratio, total protein, phosphorus, iron, selenium and copper. White blood cell counts appear to be lower in this species compared to other captive elasmobranchs. Further research into appropriate hematology standards including nutritional parameters appears warranted.

Whole-genome duplication and the functional diversification of teleost fish hemoglobins

Subsequent to the two rounds of whole-genome duplication that occurred in the common ancestor of vertebrates, a third genome duplication occurred in the stem lineage of teleost fishes. This teleost-specific genome duplication (TGD) is thought to have provided genetic raw materials for the physiological, morphological, and behavioral diversification of this highly speciose group. The extreme physiological versatility of teleost fish is manifest in their diversity of blood–gas transport traits, which reflects the myriad solutions that have evolved to maintain tissue O₂ delivery in the face of changing metabolic demands and environmental O₂ availability during different ontogenetic stages. During the course of development, regulatory changes in blood–O₂ transport are mediated by the expression of multiple, functionally distinct hemoglobin (Hb) isoforms that meet the particular O₂-transport challenges encountered by the developing embryo or fetus (in viviparous or oviparous species) and in free-swimming larvae and adults. The main objective of the present study was to assess the relative contributions of whole-genome duplication, large-scale segmental duplication, and small-scale gene duplication in producing the extraordinary functional diversity of teleost Hbs. To accomplish this, we integrated phylogenetic reconstructions with analyses of conserved synteny to characterize the genomic organization and evolutionary history of the globin gene clusters of teleosts. These results were then integrated with available experimental data on functional properties and developmental patterns of stage-specific gene expression. Our results indicate that multiple α- and β-globin genes were present in the common ancestor of gars (order Lepisoteiformes) and teleosts. The comparative genomic analysis revealed that teleosts possess a dual set of TGD-derived globin gene clusters, each of which has undergone lineage-specific changes in gene content via repeated duplication and deletion events. Phylogenetic reconstructions revealed that paralogous genes convergently evolved similar functional properties in different teleost lineages. Consistent with other recent studies of globin gene family evolution in vertebrates, our results revealed evidence for repeated evolutionary transitions in the developmental regulation of Hb synthesis.

Forecasting elasmobranch survival following exposure to severe stressors

Current fishing practices and habitat degradation in most of the world's oceans pose significant threats to marine fish including elasmobranchs. The accurate prediction of survival probability for elasmobranchs subjected to prolonged immobilisation and diminished oxygen availability during capture and a vulnerable state post-release, is reliant on selecting a reliable set of biomarkers to profile as well as using them to design pre-release interventions which minimise elasmobranch death. The purpose of this review is: i) to make a case for the need to develop new biomarkers to use in conjunction with blood chemistry; ii) to briefly present the survival strategies used by other vertebrates subjected to diminished oxygen iii) to discuss new approaches to forecasting the effect that altered physiological and biochemical markers have on long-term survival with a particular emphasis on oxidative stress, the adenylate energy charge, heat shock protein expression and the capacity for repair, so that a more detailed profile of the qualities of elasmobranch survivorship can be constructed. In addition, the review will discuss the relevance of biomarkers to field samples as well as their incorporation into laboratory based research, aimed at providing physiological and biochemical data to inform conservation management.

Distribution, adaptation and physiological meaning of thiols from vertebrate hemoglobins

In the present review, the sequences of hemoglobins (Hb) of 267 adult vertebrate species belonging to eight major vertebrate taxa are examined for the presence and location of cysteinyl residues in an attempt at correlation with their ecophysiology. Essentially, all vertebrates have surface cysteinyl residues in Hb molecules whereby their thiol groups may become highly reactive. Thiol-rich Hbs may display eight or more thiols per tetramer. In vertebrates so far examined, the cysteinyl residues occur in 44 different sequence positions in alpha chains and 41 positions in beta chains. Most of them are conservatively located and occur in only a few positions in Teleostei, Aves and Mammalia, whereas they are dispersed in Amphibia. The internal cysteinyl residue alpha104 is ubiquitous in vertebrates. Residue beta93 is highly conserved in reptiles, birds and mammals. The number of cysteine residues per tetramer with solvent access varies in vertebrates, mammalians and bony fish having the lowest number of external residues, whereas nearly all external cysteine residues in Aves and Lepidosauria are of the surface crevice type. In cartilaginous fish, amphibians, Crocodylidae and fresh water turtles, a substantial portion of the solvent accessible thiols are of the totally external type. Recent evidence shows that some Hb thiol groups are highly reactive and undergo extensive and reversible S-thiolation, and that they may be implicated in interorgan redox equilibrium processes. Participation of thiol groups in nitric oxide ((*)NO) metabolism has also been proved. The evidence argues for a new physiologically relevant role for Hb via involvement in free radical and antioxidant metabolism.

Fish hemoglobins

Vertebrate hemoglobin, contained in erythrocytes, is a globular protein with a quaternary structure composed of 4 globin chains (2 alpha and 2 beta) and a prosthetic group named heme bound to each one. Having myoglobin as an ancestor, hemoglobin acquired the capacity to respond to chemical stimuli that modulate its function according to tissue requirements for oxygen. Fish are generally submitted to spatial and temporal O2 variations and have developed anatomical, physiological and biochemical strategies to adapt to the changing environmental gas availability. Structurally, most fish hemoglobins are tetrameric; however, those from some species such as lamprey and hagfish dissociate, being monomeric when oxygenated and oligomeric when deoxygenated. Fish blood frequently possesses several hemoglobins; the primary origin of this finding lies in the polymorphism that occurs in the globin loci, an aspect that may occasionally confer advantages to its carriers or even be a harmless evolutionary remnant. On the other hand, the functional properties exhibit different behaviors, ranging from a total absence of responses to allosteric regulation to drastic ones, such as the Root effect.