Hagfish Eptatretus Cirrhatus Research Articles

Morpho-structural adaptations of the integument in different aquatic organisms

The integument acts as a barrier to protect the body from harmful pathogenic infectious agents, parasites, UV rays, trauma, and germs. The integument of invertebrates and vertebrates are structurally different: while invertebrates usually have a simple monolayer epidermis frequently covered by mucus, cuticles, or mineralized structures, vertebrates possess a multilayered epidermis with several specialized cells. This study aims to describe by morphological, histological, and immunohistochemical analyses, the morpho-structural adaptations throughout evolution of the integument of gastropod Aplysia depilans (Gmelin, 1791), ascidian Styela plicata (Lesuer, 1823), myxine hagfish Eptatretus cirrhatus (Forster, 1801) and teleost Heteropneustes fossilis (Bloch, 1794) for the first time, with special reference to sensory epidermal cells. Different types of cells could be identified that varied according to the species; including mucous cells, serous glandular cells, clavate cells, club cells, thread cells, and support cells. In all integuments of the specimens analyzed, sensory solitary cells were identified in the epidermis, immunoreactive to serotonin and calbindin. Our study provided an essential comparison of integuments, adding new information about sensory epidermal cells phylogenetic conservation and on the structural changes that invertebrates and vertebrates have undergone during evolution.

Evolution of Vertebrate Phototransduction: Cascade Activation.

We applied high-throughput sequencing to eye tissue from several species of basal vertebrates (a hagfish, two species of lamprey, and five species of gnathostome fish), and we analyzed the mRNA sequences for the proteins underlying activation of the phototransduction cascade. The molecular phylogenies that we constructed from these sequences are consistent with the 2R WGD model of two rounds of whole genome duplication. Our analysis suggests that agnathans retain an additional representative (that has been lost in gnathostomes) in each of the gene families we studied; the evidence is strong for the G-protein α subunit (GNAT) and the cGMP phosphodiesterase (PDE6), and indicative for the cyclic nucleotide-gated channels (CNGA and CNGB). Two of the species (the hagfish Eptatretus cirrhatus and the lamprey Mordacia mordax) possess only a single class of photoreceptor, simplifying deductions about the composition of cascade protein isoforms utilized in their photoreceptors. For the other lamprey, Geotria australis, analysis of the ratios of transcript levels in downstream and upstream migrant animals permits tentative conclusions to be drawn about the isoforms used in four of the five spectral classes of photoreceptor. Overall, our results suggest that agnathan rod-like photoreceptors utilize the same GNAT1 as gnathostomes, together with a homodimeric PDE6 that may be agnathan-specific, whereas agnathan cone-like photoreceptors utilize a GNAT that may be agnathan-specific, together with the same PDE6C as gnathostomes. These findings help elucidate the evolution of the vertebrate phototransduction cascade from an ancestral chordate phototransduction cascade that existed prior to the vertebrate radiation.

Morphometics and Gonadal Development of the Hagfish Eptatretus cirrhatus in New Zealand

Hagfishes have been the target of commercial fisheries in many areas of the world, with the catch processed for leather and for human consumption. A fishery has been operating in New Zealand waters for the last six years, harvesting the bearded hagfish, Eptatretus cirrhatus. The fishery has thus far been unregulated. Based on samples collected dockside over a two-year period, this report expands the morphometric database for this species, provides information on the size and weight of the harvested animals, determines the sizes at the onset of gonadal development and the minimum sizes at sexual maturation for males and females, and indicates that E. cirrhatus, like most other hagfish species, has no specific breeding season. Although females appear in the population at smaller sizes, the sex ratio for mature animals is 1:1 and the sizes of the largest males and females are comparable. The changes observed in sex ratio as a function of TL suggest differences in the timing and rates of gonadal development in females versus males rather than protogyny. Based on the size of the eggs, the number of eggs per female, the proportion of the population that contains large eggs, and the number of postovulatory females, it is clear that E. cirrhatus, like other hagfish species, are potentially vulnerable to overexploitation.

Structure and function of the velar muscle in the New Zealand hagfish Eptatretus cirrhatus: response to temperature change and hypoxia

The rate of velar movement in Eptatretus cirrhatus, as determined by electromyography, increased with Q(10) 3·2 during exposure to temperatures between 7 and 19° C and increased 3·9 fold during exposure to hypoxia (oxygen partial pressure = 6·67 kPa). This confirms the role of the velum in generating respiratory currents and modification of its activity in response to changes in metabolic demand or environmental oxygen availability. The maximum velar rate observed was 168 beats min(-1) , higher than that recorded in any hagfish species to date. Fibres of musculus craniovelaris were exclusively small, red (slow-twitch) fibres, consistent with a high aerobic capacity required by fibres involved in rhythmic, ongoing activity.

Importance of local production versus pelagic subsidies in the diet of an isolated population of bottlenose dolphins Tursiops sp.

Isolated populations can be strongly influenced by patterns in the local production of food, and by subsidies from outside sources. We used stable-isotope analysis to investigate the rela- tive importance of autochthonous food resources versus pelagic subsidies in the diet of the isolated population of bottlenose dolphins Tursiops sp. inhabiting Doubtful Sound, New Zealand. Samples of the primary carbon sources (macroalgae, phytoplankton and chemoautotrophs) as well as potential food sources (fish and squid) were collected from Doubtful Sound and analysed for δ 13 C and δ 15 N. Iso- topic signatures of fishes fell along a gradient from very depleted values for deep benthic species, particularly hagfish Eptatretus cirrhatus (δ 13 C -23.6, δ 15 N 6.3), to intermediate values for pelagic spe- cies (δ 13 C -18.1, δ 15 N 11.3) and more enriched values for reef-associated species (δ 13 C -16.1, δ 15 N 14.4). Exfoliated skin tissue was collected from live dolphins (n = 11) and used to estimate the isotopic signature of dolphin diet (δ 13 C -15.4, δ 15 N 14.2). The position of this estimate at the most enriched end of the range of isotopic signatures indicated that there was likely minimal mixing of resources from different habitats and that a majority of the dolphin population's diet came from rocky reef and dem- ersal habitats. Estimates of δ 13 C and δ 15 N for dolphin diet were compared with isotopic signatures of the different primary carbon sources using a multiple-source mixing model. Both results suggest that the diet of this population was primarily made up of autochthonous carbon production with a large contribution from benthic macroalgae, rather than pelagic subsidies from outside of the Sound.

Changes in plasma catecholamine concentration during salinity manipulation and anaesthesia in the hagfish Eptatretus cirrhatus

Plasma catecholamines were measured following surgery under anaesthesia and after exposing hagfish to 90 and 110% sea water (SW). Plasma noradrenaline (NA) concentration increased from a resting value of 7 to 818 nM l(-1) on anaesthesia. Plasma adrenaline (AD) did not change. NA concentrations also increased during volume depletion (110% SW), but to much lower values (26 nM l(-1 )at 100 min). AD concentrations were increased at 20 min, then fell. During volume loading (90% SW) NA fell, and AD increased to a maximum concentration of 511 nM l(-1) at 40 min (resting concentration 24 nM l(-1)). The data are consistent with a vasoconstrictory role for NA on central veins when venous pressures fall and a vasodilatory role for AD on volume expansion.

Evidence of a guanylyl cyclase natriuretic peptide receptor in the gills of the new zealand hagfish Eptatretus cirrhatus (Class Agnatha).

Natriuretic peptide binding sites were examined in the gills of the hagfish Eptatretus cirrhatus (Class Agnatha, subfamily Eptatretinae) using radio-ligand binding techniques, molecular cloning and guanylyl cyclase assays. Iodinated rat atrial natriuretic peptide ((125)I-rANP) and iodinated porcine C-type natriuretic peptide ((125)I-pCNP) bound specifically to the lamellar folds and cavernous tissue of E. cirrhatus gills, and 0.3 nmol l(-1) rat ANP competed for 50 % of specific (125)I-rANP binding sites. Affinity cross-linking of (125)I-rANP to gill membranes followed by sodium dodecylsulphate-polyacrylamide gel electrophoresis revealed a single binding site of 150 kDa. In the presence of Mn(2+), 0.1 nmol l(-1) rANP inhibited cGMP production, whereas 1 micromol l(-1) rANP stimulated cGMP production rates. At 1 micromol l(-1), pCNP also stimulated cGMP production. The production of cGMP was also measured in the presence and absence of ATP with either Mn(2+) or Mg(2+). Reverse transcriptase polymerase chain reaction (RT-PCR) of hagfish gill RNA, followed by cloning and sequencing of PCR products, produced a partial cDNA sequence of a natriuretic peptide guanylyl cyclase receptor. The deduced amino acid sequence indicated 87-91 % homology with other natriuretic peptide guanylyl cyclase receptors. This study indicates the presence of a natriuretic peptide guanylyl cyclase receptor in the gills of E. cirrhatus that is similar to the natriuretic peptide guanylyl cyclase receptors in higher vertebrates. These observations demonstrate that the coupling of natriuretic peptide receptors with guanylyl cyclase has a long evolutionary history.

Effects of preload and afterload on the performance of the in situ perfused portal heart of the New Zealand hagfish Eptatretus cirrhatus

The portal heart of the New Zealand hagfish (Eptatretus cirrhatus) was perfused in situ. Stroke volume, cardiac output and power output increased in response to increased preload, in accordance with Starling's law of the heart. A positive chronotropic effect was found when the input pressure increased from 0.05 to 0.1 kPa. Increased afterload decreased stroke volume and cardiac output. Power output peaked at an output pressure of 0.22 kPa, after which it decreased. There was no change in heart rate in response to increased afterload. In unanaesthetized resting animals, the pressure in the supraintestinal vein, which supplies the portal heart, ranged from 0.025 to 0.07 kPa (mean 0.040±0.005 kPa). The beta-adrenoceptor antagonist sotalol did not affect the response to different input and output pressures. Sotalol produced a significant decrease in heart rate and abolished the pressure-sensitive increase in heart rate. Bolus injections of adrenaline produced a transient increase in portal heart rate. The negative chronotropic response to sotalol and the response to adrenaline indicate the presence of an endogenous beta-adrenergic tonus on the portal heart.

Stimulation of Calcium Efflux from the Hagfish, Eptatretus cirrhatus, Gill Pouch by an Extract of Corpuscles of Stannius from an Eel (Anguilla dieffenbachii): Teleostei

A factor present in the homogenate of the corpuscles of Stannius from a teleost, the longfin eel Anguilla dieffenbachii, showed calcitropic effects in an agnathan, the hagfish Eptatretus cirrhatus. This factor greatly increased calcium efflux from an isolated perfused gill pouch preparation and had no effect on calcium influx. Hagfish regulated plasma total calcium at a concentration which was about 50% of that of the ambient seawater. Intact hagfish had rates of calcium influx and efflux which were similar to those recorded in teleosts. Hagfish are thus similar to teleosts to the extent that they can and do maintain a plasma calcium concentration which is quite different from that of the ambient medium. They also resemble teleosts in that transepithelial calcium fluxes across the hagfish gill pouches respond to extracts of Stannius corpuscles. Hagfish, however, are quite unlike teleosts in that the Stannius corpuscle extract stimulates calcium efflux rather than inhibiting calcium influx.

Anaerobic glycolysis in the dental plate retractor muscles of the New Zealand hagfish Eptatretus cirrhatus during feeding

AbstractHagfish lack jaws, and the teeth are carried on a cartilagenous dental plate associated with the large longitudinal and tubular retractor muscles. Previous studies had shown that the retractors had intracellular pH buffering capacities among the highest reported for vertebrate muscle, and as these animals indulge in bursts of feeding within the hypoxic body cavity of dead fish it was of interest to examine the role of anaerobic glycolysis in powering the dental plate retractor muscles. Both retractors of the New Zealand hagfish Eptatretus cirrhatus contain only large diameter white muscle fibres (X = 200μm), and show low capillary:fibre ratios relative to the red and pink fibres of the general body musculature. These white fibres are characterized by sparsely distributed small mitochondria with poorly developed inner membranes, low activities of enzymes unique to aerobic ATP production, and moderate activities of glycolytic enzymes. During bursts of continuous feeding for periods of from 1.5 to 6.45 min there was a linear increase in lactate concentration at rates of 19.6 and 17.4 μmol lactate min−1 g−1 wet wt muscle, respectively, for the longitudinal and tubular retractors, reaching a maximum of 132 μmol lactate g−1 wet wt muscle. While the glycolytic flux in the hagfish retractors during feeding may not reach levels encountered in white muscle of burst swimming tuna, the actual lactate concentrations achieved are among the highest ever reported for normal muscle work by unrestrained animals.

Properties of the muscle and heart lactate dehydrogenases of the New Zealand hagfish, Eptatretus cirrhatus: Functional and evolutionary implications

AbstractHagfish possess two lactate dehydrogenase (LDH) subunit types that combine to form only the two homotetramers LDHA4 and LDHB4. Similarities in the kinetic properties of these isozymes from Myxine glutinosa have been attributed to the anaerobic nature of the hagfish heart and the failure of LDHB4 to diverge in function since the ancient A‐B gene duplication. The LDHA4 and LDHB4 isozymes purified from the New Zealand hagfish Eptatretus cirrhatus display more divergent properties which are consistent with the more efficient oxygen delivery system and aerobic lifestyle of this species. This, together with recent reinterpretations of LDH subunit evolution, leads to the conclusion that the unusual properties of hagfish LDH isozymes can be attributed to metabolic adaptation rather than to the conservation of features present in the ancestral LDH of vertebrates.

Blood pressures and heart rates in swimming hagfish

1. 1. Ventral and dorsal aortic pressures and heart rates were measured in the New Zealand hagfish Eptatretus cirrhatus at rest, during forced exercise and on recovery from swimming. 2. 4. Blood pressures were higher than those reported for the Atlantic hagfish, Myxine glutinosa, but were considerably lower than equivalent pressures found in teleost and elasmobranch fish. 3. 3. The ventricular pressure pulse was always transmitted to the dorsal aorta and our evidence contradicts the view that branchial resistance is high in myxinoids. 4. 4. Heart rates and ventral aortic pressures were higher after 10 min swimming, but the changes were not marked. 5. 5. The tachycardia was continued into recovery. 6. 6. The absence of bradycardia when the fish was disturbed (startle reflex) and the smooth increases and falls in heart rates and pressures suggest that neural regulation of the heart is not important in swimming and that venous return may be the major factor determining cardiac function.

Characterization of the changes in the state of aggregation induced by ligand binding in the hemoglobin system of a primitive vertebrate, the hagfish Eptatretus cirrhatus

1. 1. Hemoglobin (Hb) from the hagfish, Eptatretus cirrhatus, is composed of subunits of approx. 20,000 mol. wt. 2. 2. Aggregation of the deoxy subunits occurred, particularly at low pH and at high protein concentration. 3. 3. Oxygen equilibrium studies indicated slight cooperativity and the presence of a small, phosphateindependent Bohr effect. 4. 4. Equilibrium properties were protein concentration dependent indicating an oxygen-linked dissociation in the millimolar concentration range. 5. 5. Kinetic studies indicated a dimer to monomer transition in the micromolar concentration range. 6. 6. The ligand-binding character of hagfish Hb was similar to that of lampreys, but was governed by different kinetic and equilibrium parameters.