A unique selenoprotein isolated from yellowfin tuna (Thunnus albacares) liver

A selenoprotein, with an approximate molecular weight of 2000, was isolated from yellowfin tuna (Thunnus albacares) liver. The selenium (Se) content of this selenoprotein fraction represented greater than 50% of the Se in the original liver extract. Most of the unrecovered Se was left in the pellet following homogenization. Although the protein was very sensitive to oxidizing conditions, it remained stable in the presence of reducing agents such as glutathione and dithiothreitol under a nitrogen atmosphere. After preparative isoelectric focusing of the purified selenoprotein, selenium was detected in three distinct bands, with the predominant band occurring at pH 6.2.     

Isolation and characterization of metmyoglobin reductase from yellowfin tuna (Thunnus albacares)

The isolation, purification, and characterization of metmyoglobin reductase from yellowfin tuna (Thunnus albacares) is described. The enzyme has been purified 120-fold. Characterization of the enzyme includes molecular weight, isoelectric point, substrate specificity, enzyme kinetics, chromatographic behavior, and sensitivity to inhibitors. The physical and catalytic properties of the tuna enzyme are compared to those of bovine and blue-white dolphin metmyoglobin reductase.     

Turning radius of yellowfin tuna (Thunnus albacares) in unsteady swimming manoeuvres

The specific turning radius of yellowfin tuna Thunnus albacares Cuvier is large relative to that of other fish (0.47 total body length ± 0.18, mean ± 2 s.e .). We argue that specializations for efficient steady swimming compromise performance in transient turning manoeuvres.     

Preparation and structural analysis of actinidain-processed atelocollagen of yellowfin tuna (Thunnus albacares)

Pepsin-hydrolyzed collagen (atelocollagen) is a trimer, consisting of alpha 1 and alpha 2 monomers, and shows molecular species corresponding to a monomer, dimer (beta chain), and trimer (gamma chain) by SDS-polyacrylamide gel electrophoresis. Atelocollagen was purified from yellowfin tuna (Thunnus albacares) by salt precipitation and cation-exchange chromatography. Enzymatic hydrolysis of the atelocollagen by actinidain, a cysteine protease purified from kiwifruit, was analyzed by SDS-polyacrylamide gel electrophoresis. The triple helical structure unique to collagen was retained in the atelocollagen as judged by circular dichroism spectra. The actinidain-processed atelocollagen showed only monomeric alpha 1 and alpha 2 chains, with no beta and gamma chains, by SDS-polyacrylamide gel electrophoresis; nevertheless, it retained the typical triple helical structure. It is suggested that actinidain cleaved the atelocollagen molecule at specific sites on the inside of the inter-strand cross-linking peptides.     

Detection and characterization of Kudoa thunni from uncooked yellowfin tuna (Thunnus albacares) in Southeast Asia

Myxosporean parasites Kudoa spp. have been reported in several marine fish species worldwide. However, little is known about the contamination of these parasites in raw fish in Southeast Asia, where the consumption demand of uncooked fish is increasing. In 2019, the occurrence of several cases of raw yellowfin tuna (Thunnus albacares) obtained from retail shops with the presence of unknown white, nodular cysts within the musculature have raised public health concerns for the consumption of raw marine fish in Vietnam. Microscopic examination revealed numerous myxospores with the quadratic shape of the Kudoidae. Morphologically, stained spores detected in this study are suspected to Kudoa thunni. To confirm the suspected Kudoa species, further examination of the 18S small-subunit (SSU) was conducted and the results of nucleotide sequence analysis obtained from nodular cysts revealed 99.18–100% identity to that of Kudoa thunni sequences available in GenBank. Detection of K. thunni infection in tuna in Southeast Asia highlights the need for appropriate surveillance and control measures to ensure high quality standards and safety on raw fish production and consumption.     

Food consumption of yellowfin tuna,Thunnus albacares, in Sri Lankan waters

Synopsis A total of 4181 stomachs of yellowfin tuna,Thunnus albacares (22–164 cm FL), mainly caught by gillnets in the period from July 1984 to June 1986 were analyzed. Food consumption of yellowfin tuna in nature was determined using the values of the average stomach content, incorporating laboratory measurements of gastric evacuation rates in a feeding model. The diet of yellowfin tuna around Sri Lanka comprised a variety of macro zooplanktonic and nektonic organisms. Juveniles < 39 cm FL, are planktivores. Tuna > 40 cm FL gradually increase their consumption of fishes with increasing size. Among fish speciesAuxis sp. are the most important. The daily food consumption of juvenile yellowfin tuna (22–59 cm FL) range from 1.8 g to 136.2 g, increasing to about 284.7 g to 551.9 g for the medium size tuna (60–99 cm FL). The adult tuna (100–>130 em FL) consume around 513 g to 538.8 g of prey per day. Daily ration estimates increase from 2.1% to 5.5% of body weight with increasing size up to 70 cm FL, beyond which it decreases. The predatory pressure of yellowfin tuna on commercially important fishes and other species is discussed.     

Diet composition of bigeye tuna (Thunnus obesus) and yellowfin tuna (Thunnus albacares) caught on aggregated schools in the western equatorial Atlantic Ocean

The present study aims to characterize and compare the diet of bigeye and yellowfin tunas caught on aggregated schools in the western equatorial Atlantic Ocean. The samples were collected from January 2011 to June 2016. The tunas were measured on board and the stomachs were removed after evisceration. The stomachs were analyzed regarding their Index of Fullness and the importance of each prey in the diet was estimated by the Index of Relative Importance (IRI). The diet overlap was assessed by the Morisita‐Horn's Index, Non‐Metric Multidimensional Scale (NMDS), and Analysis of Similarity (ANOSIM). The feeding strategy was determined by the Costello's Diagram. The 195 bigeye and 212 yellowfin tunas ranged in fork length from 51 to 137 cm and 43 to 174 cm, respectively. The diet of bigeye tuna was composed of 10 families of fish, three cephalopod families, and four crustacean orders. The diet of yellowfin tuna was composed of 11 families of fish, three cephalopod families, and three crustacean orders. The yellowfin tuna seems to feed upon more abundant prey species near the surface like flying fish, which have the concentration enhanced by the light attractors on the boat, and occasionally on other prey from deeper habitats like lanternfish, squids, and pomfret. Bigeye tuna feed mainly at prey that commonly occurs in deeper habitats like squids, drift fish, lanternfish, and pomfret.     

Proteolysis of skeletal muscle in yellowfin tuna (Thunnus albacares): Evidence of calpain activation

• 1.1. White muscle of yellowfin tuna is subject to a form of deterioration known as “burnt tuna”.
• 2.2. TEM and SDS-PAGE were used to quantify cellular differences in deteriorated white muscle of yellowfin tuna.
• 3.3. Electron micrographs showed a significant loss of Z-disc integrity and an increase in intracellular edema in burnt tuna.
• 4.4. Electrophoresis established that a specific doublet of proteins, 42 kD and 46 kD was lost.
• 5.5. Proteolysis of isolated myofibrils incubated in calpain (EC 3.4.22.17) was greatest at pH 7.5 and was selective for intermediate molecular weight proteins.
• 6.6. This evidence suggests that burnt tuna is a specific and limited proteolysis of myofibrillar structural proteins characteristic of calpain proteolysis.

     

Responses of the red blood cells from two high-energy-demand teleosts, yellowfin tuna (Thunnus albacares) and skipjack tuna (Katsuwonus pelamis), to catecholamines

In fishes, catecholamines increase red blood cell intracellular pH through stimulation of a sodium/proton (Na⁺/H⁺) antiporter. This response can counteract potential reductions in blood O₂ carrying capacity (due to Bohr and Root effects) when plasma pH and intracellular pH decrease during hypoxia, hypercapnia, or following exhaustive exercise. Tuna physiology and behavior dictate exceptionally high rates of O₂ delivery to the tissues often under adverse conditions, but especially during recovery from exhaustive exercise when plasma pH may be reduced by as much as 0.4 pH units. We hypothesize that blood O₂ transport during periods of metabolic acidosis could be especially critical in tunas and the response of rbc to catecholamines elevated to an extreme. We therefore investigated the in vitro response of red blood cells from yellowfin tuna (Thunnus albacares) and skipjack tuna (Katsuwonus pelamis) to catecholamines. Tuna red blood cells had a typical response to catecholamines, indicated by a rapid decrease in plasma pH. Amiloride reduced the response, whereas 4,4′diisothiocyanatostilbene-2,2′-disulphonic acid enhanced both the decrease in plasma pH and the increase in intracellular pH. Changes in plasma [Na⁺], [Cl⁻], and [K⁺] were consistent with the hypothesis that tuna red blood cells have a Na⁺/H⁺ antiporter similar to that described for other teleost red blood cells. Red blood cells from both tuna species were more responsive to noradrenaline than adrenaline. At identical catecholamine concentrations, the decrease in plasma pH was greater in skipjack tuna blood, the more active of the two tuna species. Based on changes in plasma pH, the response of red blood cells to catecholamines from both tuna species was less than that of rainbow trout (Oncorhynchus mykiss) red blood cells, but greater than that of cod (Gadus morhua) red blood cells. Noradrenaline had no measurable influence on the O₂ affinity of skipjack tuna blood and only slightly increased the O₂ affinity of yellowfin tuna blood. Our results, therefore, do not support our original hypothesis. The catecholamine response of red blood cells from high-energy-demand teleosts (i.e., tunas) is not enhanced compared to other teleosts. There are data on changes in cardio-respiratory function in tunas caused by acute hypoxia and modest increases in activity, but there are no data on the changes in cardio-respiratory function in tunas accompanying the large increases in metabolic rate seen during recovery from exhaustive exercise. However, we conclude that during those instances where high rates of O₂ delivery to the tissues are needed, tunas' ability to increase cardiac output, ventilation volume, blood O₂ carrying capacity, and effective respiratory (i.e., gill) surface area are probably more important than are the responses of red blood cells to catecholamines. We also use our data to investigate the extent of the Haldane effect and its relationship to blood O₂ and CO₂ transport in yellowfin tuna. Yellowfin tuna blood shows a large Haldane effect; intracellular pH increases 0.20 units during oxygenation. The largest change in intracellular pH occurs between 40–100% O₂ saturation, indicating that yellowfin tuna, like other teleosts, fully exploit the Haldane effect over the normal physiological range of blood O₂ saturation. Accepted: 27 March 1998     

Oxygen transport and cardiovascular responses in skipjack tuna (Katsuwonus pelamis) and yellowfin tuna (Thunnus albacares) exposed to acute hypoxia

Summary Responses to acute hypoxia were measured in skipjack tuna (Katsuwonus pelamis) and yellowfin tuna (Thunnus albacares) (1–3 kg body weight). Fish were prevented from making swimming movements by a spinal injection of lidocaine and were placed in front of a seawater delivery pipe to provide ram ventilation of the gills. Fish could set their own ventilation volumes by adjusting mouth gape. Heart rate, dorsal and ventral aortic blood pressures, and cardiac output were continuously monitored during normoxia (inhalant water (PO ₂>150 mmHg) and three levels of hypoxia (inhalant water PO ₂130, 90, and 50 mmHg). Water and blood samples were taken for oxygen measurements in fluids afferent and efferent to the gills. From these data, various measures of the effectiveness of oxygen transfer, and branchial and systemic vascular resistance were calculated. Despite high ventilation volumes (4–71·min^-1·kg^-1), tunas extract approximately 50% of the oxygen from the inhalant water, in part because high cardiac outputs (115–132 ml·min^-1·kg^-1) result in ventilation/perfusion conductance ratios (0.75–1.1) close to the theoretically ideal value of 1.0. Therefore, tunas have oxygen transfer factors (ml O₂·min^-1·mmHg^-1·kg^-1) that are 10–50 times greater than those of other fishes. The efficiency of oxygen transfer from water in tunas (65%) matches that measured in teleosts with ventilation volumes and order of magnitude lower. The high oxygen transfer factors of tunas are made possible, in part, by a large gill surface area; however, this appears to carry a considerable osmoregulatory cost as the metabolic rate of gills may account for up 70% of the total metabolism in spinally blocked (i.e., non-swimming) fish. During hypoxia, skipjack and yellowfin tunas show a decrease in heart rate and increase in ventilation volume, as do other teleosts. However, in tunas hypoxic bradycardia is not accompanied by equivalent increases, in stroke volume, and cardiac output falls as HR decreases. In both tuna species, oxygen consumption eventually must be maintained by drawing on substantial venous oxygen reserves. This occurs at a higher inhalant water PO₂ (between 130 and 90 mmHg) in skipjack tuna than in yellowfin tuna (between 90 and 50 mmHg). The need to draw on venous oxygen reserves would make it difficult to meet the oxygen demand of increasing swimming speed, which is a common response to hypoxia in both species. Because yellowfin tuna can maintain oxygen consumption at a seawater oxygen tension of 90 mmHg without drawing on venous oxygen reserves, they could probably survive for extended periods at this level of hypoxia.Abbreviations BP_da, BP_va dorsal, ventral aortic blood pressure - C _aO₂, C _vO₂ oxygen content of arterial, venous blood - DO₂ diffusion capacity - E_b, E_w effectiveness of O₂ uptake by blood, and from water, respectively - Hct hematocrit - HR heart rate - PCO₂ carbon dioxide tension - P _aCO₂, P _vCO₂ carbon dioxide tension of arterial and venous blood, respectively - PO₂ oxygen tension - P _aO₂, P _vO₂, P _iO₂, P _cO₂ oxygen tension of arterial blood, venous blood, and inspired and expired water, respectively - pHa, pHv pH of arterial and venous blood, respectively - P_w—b effective water to blood oxygen partial pressure difference - Pg partial pressure (tension) gradient - cardiac output - R vascular resistance - SV stroke volume - SEM standard error of mean - TO₂ transfer factor - U utilization - _g ventilation volume - O₂ oxygen consumption     

The effect of stimulation frequency on the transmural ventricular monophasic action potential in yellowfin tuna Thunnus albacares

Monophasic action potentials (MAPs) were recorded from the spongy and compact layers of the yellowfin tuna Thunnus albacares ventricle as stimulation frequency was increased. MAP duration decreased with increase in stimulation frequency in both the spongy and compact myocardial layers, but no significant difference in MAP duration was observed between the layers.     

Mitochondrial DNA analysis reveals three stocks of yellowfin tuna Thunnus albacares (Bonnaterre, 1788) in Indian waters

Yellowfin tuna (Thunnus albacares) is an epipelagic, oceanic species of family Scombridae found in tropical and subtropical region of Pacific, Indian and Atlantic Ocean. It is commercially important fish and accounts for 19 % of total tuna catches in Indian waters. In present study, population structure of yellowfin tuna was examined using sequence analysis of mitochondrial DNA from seven geographically distinct locations along the Indian coast. A 500 bp segment of D-loop region was sequenced and analysed for 321 yellowfin samples. Hierarchical analysis of molecular variance showed significant genetic differentiation among three groups (VE); (AG); (KO, TU, PO, VI, PB) analyzed (Φ _ST  = 0.03844, P ≤ 0.001). In addition, spatial analysis of molecular variance identified three genetically heterogeneous groups of yellowfin tuna in Indian waters. Results were further corroborated by significant value of nearest neighbour statistic (S _nn = 0.261, P ≤ 0.001). Thus finding of this study rejects the null hypothesis of single panmictic population of yellowfin tuna in Indian waters.     

Autoxidation of myoglobin from bigeye tuna fish (Thunnus obesus)

Native oxymyoglobin (MbO2) was isolated directly from the skeletal muscle of bigeye tuna (Thunnus obesus) with complete separation from metmyoglobin (metMb) on a CM-cellulose column. It was examined for its stability properties over a wide range of pH values (pH 5-12) in 0.1 M buffer at 25 degrees C. When compared with sperm whale MbO2 as a reference, the tuna MbO2 was found to be much more susceptible to autoxidation. Kinetic analysis has revealed that the rate constant for a nucleophilic displacement of O2- from MbO2 by an entering water molecule is 10-times higher than the corresponding value for sperm whale MbO2. The magnitude of the circular dichroism of bigeye tuna myoglobin at 222 nm was comparable to that of sperm whale myoglobin, but its hydropathy profile revealed the region corresponding to the distal side of the heme iron to be apparently less hydrophobic. The kinetic simulation also demonstrated that accessibility of the solvent water molecule to the heme pocket is clearly a key factor in the stability properties of the bound dioxygen.     

Habitat and behaviour of yellowfin tuna Thunnus albacares in the Gulf of Mexico determined using pop-up satellite archival tags

This study presents the first data on movement, habitat use and behaviour for yellowfin tuna Thunnus albacares in the Atlantic Basin. Six individuals were tracked in the Gulf of Mexico using pop-up satellite archival tags. Records up to 80 days in length were obtained, providing information on depth and temperature preferences as well as horizontal movements. Thunnus albacares in the Gulf of Mexico showed a strong preference for the mixed layer and thermocline, consistent with findings for this species in other ocean basins. Fish showed a diel pattern in depth distribution, remaining in surface and mixed layer waters at night and diving to deeper waters during the day. The vertical extent of T. albacares habitat appeared to be temperature limited, with fish generally avoiding waters that were >6° C cooler than surface waters. The vertical and thermal habitat usage of T. albacares differs from that of bigeye Thunnus obesus and bluefin Thunnus thynnus , Thunnus orientalis and Thunnus maccoyii tunas. These results are consistent with the results of earlier studies conducted on T. albacares in other oceans.     

Variations in the age and growth of yellowfin tuna larvae,Thunnus albacares,collected about the Mississippi River plume

Synopsis Eight hundred and one yellowfin tuna larvae ranging from 2.57–7.48 mm SL were collected near the Mississippi River discharge plume in the Gulf of Mexico during July and September, 1987. Larvae were most abundant at intermediate salinities (i.e. frontal waters) where chlorophylla and macrozooplankton displacement values were also highest. Using sagittal otolith microstructure, we estimated larval ages ranging from 3–14 d. These ages were used to back calculate spawning dates from 13–24 July and 22–31 August. Mean absolute individual growth rate (length age^–1) was 0.47 mm d^–1, with the least squares linear regression SL = 1.67 + 0.47 AGE (r² = 0.60, Pr> F = 0.0001) representing the best growth curve. Highest growth occurred at intermediate salinities near 31%, and temperatures near 29° C. There was significant temporal variation in growth, with larvae collected in July growing slower than those from September (0.37 and 0.48 mm d^–1, respectively). The pooled instantaneous daily mortality rate (Z) of the larvae was estimated to be 0.33 d^–1 (0.16 d^–1 in July and 0.41 d^–1 in September). These results show that significant spawning of yellowfin tuna may occur in the northern Gulf of Mexico in the vicinity of the Mississippi River discharge plume, and suggest that larval growth and survival may be enhanced in the plume frontal waters.     

Trypsins from yellowfin tuna (Thunnus albacores) spleen: purification and characterization

Two anionic trypsins (A and B) were purified to homogeneity from yellowfin tuna (Thunnus albacores) spleen by a series of column chromatographies including Sephacryl S-200, Sephadex G-50 and DEAE-cellulose. Purity was increased to 70.6- and 91.5-fold with approximately 2.8% and 15.6% yield for trypsin A and B, respectively. The apparent molecular weight of both trypsins was estimated to be 24 kDa by size exclusion chromatography and SDS-PAGE. Both trypsin A and B appeared as a single band on native-PAGE. Trypsin A and B exhibited the maximal activity at 55 and 65 degrees C, respectively, and had the same optimal pH at 8.5 using TAME as a substrate. Both trypsins were stable to heat treatment up to 50 degrees C and in the pH range of 6.0 to 11.0. Both trypsin A and B were stabilized by calcium ion. The activities were inhibited effectively by soybean trypsin inhibitor, TLCK and partially inhibited by EDTA, but were not inhibited by E-64, N-ethylmaleimide, iodoacetic acid, TPCK and pepstatin A. Activity of both trypsins continuously decreased with increasing NaCl concentration (0-30%). Apparent Km and Kcat of trypsin A and B for TAME were 0.2-0.33 mM and 66.7-80 S(-1), respectively. The N-terminal amino acid sequences of trypsin A, IVGGYECQAHSQPHQVSLNA, and trypsin B, IVGGYECQAHSQPPQVSLNA, indicated the high homology between both enzymes.