Psammomys Obesus

Top PDF Psammomys Obesus:

Impact of glucotoxicity induced in vivo and in vitro in Psammomys obesus

Impact of glucotoxicity induced in vivo and in vitro in Psammomys obesus

Objective: Chronic hyperglycemia characteristic of type diabetes 2 is responsible for the accel- erated atherosclerosis with increased cardio- vascular risk. In this study, we will propose to analyze the effect of a long-term of glucotoxicity in vivo in Psammomys obesus by addition of sucrose to 30% for 11 months and in vitro study of adventitial fibroblasts in the presence of D-glucose 0.6% for 7 days. Materials and meth- ods: Evaluation of plasma biochemical parame- ters was carried out at the initial time and at the end of experiment. At autopsy, a morphological study of the aorta was performed after fixation in aqueous Bouin and staining with Masson’s trichrome. The experimental glucotoxicity is in- duced by incubation of fibroblasts in DMEM en- riched with D-glucose at 0.6% for 7 days. The impact of glucotoxicity is assessed in the intra- cellular compartments through dosage of total nitrite and malondialdehyde, a product of lipid peroxidation, and thanks to a morphological assay after fixation of cells with aqueous bouin and blood staining with May Grünwald Giemsa. The evaluation of cell proliferation is accom- plished by cell counting. Collagens I and III of the extracellular compartment are characterized by SDS-PAGE. Results: Animals subjected to sucrose showed hyperglycemia associated with hyperinsulinemia, dyslipidemia, hyperproteine- mia, increased CPK and VLDL-LDL and de- creased HDL. Histology of aortas revealed en- dothelial cells hypertrophy, severe disorganiza- tion of intima and media. In the presence of glu- cose, the proliferation of fibroblasts increases very significantly (P = 2.34 × 10 −5 ), the rate of

13 Read more

Atherosclerosis and atherosensitivity in two southwest Algerian desert rodents, <em>Psammomys obesus</em> and <em>Gerbillus gerbillus</em>, and in <em>Rattus norvegicus</em>

Atherosclerosis and atherosensitivity in two southwest Algerian desert rodents, <em>Psammomys obesus</em> and <em>Gerbillus gerbillus</em>, and in <em>Rattus norvegicus</em>

histoenzymologic type. The very low pyroninophilicity of the myocyte cytoplasm reflects its low content of ribonucleoproteins. The activities of some oxidoreductases were higher in these arteries than in the aorta. This differ- ence must reflect the greater cell density in the media of the muscular artery, but may also induce a better contractility. Finally, the arterial metabolism of Psammomys appears closer to that of Gerbillus than to that of Wistar rats. In our precedent contribution, we show that histological charac- terization demonstrates the typical alterations observed in atherosclerosis and that Psammomys obesus is an excellent animal model in which to study the progression of T2D and the development of atherosclerosis. 36 The observations

9 Read more

Psammomys Obesus Diet, Tank of the Cutaneous Leishmaniose, Zoonotic Disease of arid and Semi-arid Areas

Psammomys Obesus Diet, Tank of the Cutaneous Leishmaniose, Zoonotic Disease of arid and Semi-arid Areas

The calculation of the frequency of occurrence (A.Butet 1985) provides us with information about the presence of each of the three species representative of the diet of Psammomys obesus at Dzira. This non-invasive method that does not require sacrificing the animal, applied in natural condition is entirely adapted to the study of gerbil Psammomys obesus protected by law and therefore forbidden of sampling.

12 Read more

Patterns of the tapeworm Raillietina trapezoides infection in the fat sand rat Psammomys obesus in Tunisia: season, climatic conditions, host age and crowding effects

Patterns of the tapeworm Raillietina trapezoides infection in the fat sand rat Psammomys obesus in Tunisia: season, climatic conditions, host age and crowding effects

The tapeworm Raillietina trapezoides was studied in a Tunisian population of the fat sand rat Psammomys obesus. Seasonal changes in the abundance of parasite and host were monitored in a longitudinal field survey lasting 20 months. In total 582 intestinal samples were collected during 10 trapping sessions between May 1995 and January 1997 and examined. The impact of abiotic and biotic factors on the prevalence and parasite burden were explored, using generalized linear models. R. trapezoides showed a seasonal pattern with most transmission occurring in summer and autumn. In August–September when the rodents were at low density and most adult (90–100 %) were infected. In winter, infections with R. trapezoides were highly prevalent in the cohort of adults only. The worm burden by number was also high in late summer and autumn. Prevalence and parasite burden by number or by biomass were highly age dependent. Season and age act in synergy so that the rodents were highly infected in late summer and autumn. Unusually dry conditions in winter seemed to increase prevalence and to reduce the number of worms. There was no difference between males and females in prevalence or parasite burden (by number or by biomass). Prevalence was not correlated with the relative density of the hosts whereas parasite burden depended upon their densities. The more numerous the worms were, the smaller they were individually, reflecting a crowding effect. The possibility of an immune response regulating P. obesus is discussed, in regard to the very high natural prevalence and the variation in worm burden, and compared with other parasite–host systems.

12 Read more

Microscopic anatomy of ocular globe in diurnal desert rodent Psammomys obesus (Cretzschmar, 1828)

Microscopic anatomy of ocular globe in diurnal desert rodent Psammomys obesus (Cretzschmar, 1828)

retinas are thicker because they contain a greater num- ber of long and slender rods in the external layers of the neuroretina to increase its sensitivity to light. In addition, previous experiments by Saidi, Chaouacha- Chekir, and Hicks (2012) have shown the retinal pheno- type of a diurnal rodent Psammomys obesus , with a spe- cial emphasis on cone and horizontal cells. The large numbers, size and expression patterns of these two pop- ulations indicate the visual system is adapted to diurnal activity, like man.

6 Read more

&beta;-glycosphingolipids ameliorated non-alcoholic steatohepatitis in the <em>Psammomys obesus</em> model

&beta;-glycosphingolipids ameliorated non-alcoholic steatohepatitis in the <em>Psammomys obesus</em> model

Abstract: Liver steatosis is a common characteristic of obesity and type 2 diabetes, and fatty liver disease is increasingly recognized as a major health burden. Accumulating evidence suggests that β-glycosphingolipids play an important role in insulin sensitivity and thus could affect hepatic steatosis. To determine the effect associated with β-glycosphingolipid-mediated amelioration of liver injury, seven groups of Psammomys obesus on a high-energy diet were studied. Animals were treated with daily injections of β-glucosylceramide, β-lactosylceramide, or a combination of both. β-glycosphingolipids ameliorated the hepatic injury manifested by decreased liver enzymes, liver weight, and hepatic fat, and improved liver histology. Administration of both β-glucosylceramide and β-lactosylceramide also decreased interferon (IFN)-γ serum levels. These effects were associated with improved serum cholesterol and triglyceride levels. These data suggest that β-glycosphingolipids ameliorate liver injury in an animal model of nonalcoholic steatohepatitis.

8 Read more

The small leucine-rich proteoglycan, <em>biglycan</em>, is highly expressed in adipose tissue of <em>Psammomys obesus</em> and is associated with obesity and type 2 diabetes

The small leucine-rich proteoglycan, <em>biglycan</em>, is highly expressed in adipose tissue of <em>Psammomys obesus</em> and is associated with obesity and type 2 diabetes

Abstract: We have previously demonstrated that the small leucine-rich proteoglycan decorin may play a role in adipose tissue homeostasis and the pathophysiology of obesity. Biglycan is highly similar in structure to decorin, therefore we hypothesized it would have a similar expres- sion profile and role to decorin in adipose tissue. Real time polymerase chain reaction was used to measure biglycan mRNA levels in adipose tissue from normal glucose tolerant and impaired glucose tolerant and type 2 diabetic (T2D) Psammomys obesus. Biglycan mRNA was found to be highly expressed in adipose tissue, and gene expression was significantly higher in visceral compared to subcutaneous adipose tissue, with elevated levels in obese, T2D compared to lean normal glucose tolerant P. obesus (P , 0.04). Biglycan mRNA was predominantly expressed by stromal/vascular cells of fractionated adipose tissue (P = 0.023). Biglycan expression in adipose tissue, particularly in the obese state, was markedly upregulated. Collectively, our data suggest that the small leucine-rich proteoglycan family proteins biglycan and decorin may play a role in the development of obesity and T2D, possibly by facilitating expansion of adipose tissue mass.

6 Read more

A high oleic sunflower oil fatty acid esters of plant sterols mixed with dietary diacylglycerol reduces plasma insulin and body fat accumulation in Psammomys obesus

A high oleic sunflower oil fatty acid esters of plant sterols mixed with dietary diacylglycerol reduces plasma insulin and body fat accumulation in Psammomys obesus

Background: Metabolic syndrome is associated with subsequent development of cardiovascular diseases and type 2 diabetes. It is characterized by reduced response to insulin, central obesity, and dyslipidemia. Intake of plant sterols (PS) has been shown to confer a healthier lipid profile and ameliorate cardiovascular disease risk factors in experimental animals and humans. In this study we used an animal model of type 2 diabetes to assess the effects of a preparation of PS esterified to high oleic sunflower oil fatty acids mixed with dietary diacylglycerol (PS-HOSO) on diabetic related metabolic parameters. Psammomys obesus (P. obesus) were fed high energy (HE) diet supplemented by either PS-HOSO or control oil. Following 4.5 weeks of intervention, animals were divided into fasting and non-fasting modes prior to outcome measurements. Glucose and insulin levels as well as blood lipid profile, body weight, and fat accumulation were evaluated in fasting and non-fasting modes.

8 Read more

Rapid Development of Non-Alcoholic Steatohepatitis in Psammomys obesus (Israeli Sand Rat)

Rapid Development of Non-Alcoholic Steatohepatitis in Psammomys obesus (Israeli Sand Rat)

Psammomys obesus (Israeli sand rat) is a gerbil that is a unique animal model of the Metabolic Syndrome. In its native desert environment, P. obesus remain lean and healthy. However, when housed under laboratory conditions and fed a standard rodent diet (20% kcal/fat), a proportion of P. obesus become obese and type 2 diabetic, while others remain lean and healthy [10–14]. Previous studies have shown P. obesus to be susceptible to steatosis when fed a standard rodent diet with added fibre (30% wheat straw), however key features of human NASH such as fibrosis, hepatocyte injury and inflammation were absent [15]. The majority of previously reported rodent models of NAFLD/NASH utilize diets high in fat and/or supplemented with cholesterol. As P. obesus will not consume highly palatable energy-rich diets, we tested whether NASH could be induced in P. obesus via addition of cholesterol (2% w/w) to their standard rodent diet (20% kcal/fat). In this study we show that dietary cholesterol supplementation for 4 weeks induces NASH in P. obesus with a profile similar to that seen in patients.

7 Read more

Mitochondrial metabolism reveals a functional architecture in intact islets of Langerhans from normal and diabetic Psammomys obesus

Mitochondrial metabolism reveals a functional architecture in intact islets of Langerhans from normal and diabetic Psammomys obesus

Katzman, S. M., M. A. Messerli, D. T. Barry, A. Grossman, T. Harel, J. D. Wikstrom, B. E. Corkey, P. J. S. Smith, and O. S. Shirihai. Mitochondrial metabolism reveals a functional architecture in intact islets of Langerhans from normal and diabetic Psammomys obesus. Am J Physiol Endocrinol Metab 287: E1090 –E1099, 2004; doi:10.1152/ajpendo.00044.2004.—The cells within the intact islet of Langerhans function as a metabolic syncytium, secreting insulin in a coordinated and oscillatory manner in response to external fuel. With increased glucose, the oscillatory amplitude is enhanced, leading to the hypothesis that cells within the islet are secreting with greater synchronization. Consequently, non-insulin-dependent diabetes mel- litus (NIDDM; type 2 diabetes)-induced irregularities in insulin se- cretion oscillations may be attributed to decreased intercellular coor- dination. The purpose of the present study was to determine whether the degree of metabolic coordination within the intact islet was enhanced by increased glucose and compromised by NIDDM. Exper- iments were performed with isolated islets from normal and diabetic Psammomys obesus. Using confocal microscopy and the mitochon- drial potentiometric dye rhodamine 123, we measured mitochondrial membrane potential oscillations in individual cells within intact islets. When mitochondrial membrane potential was averaged from all the cells in a single islet, the resultant waveform demonstrated clear sinusoidal oscillations. Cells within islets were heterogeneous in terms of cellular synchronicity (similarity in phase and period), sinusoidal regularity, and frequency of oscillation. Cells within normal islets oscillated with greater synchronicity compared with cells within diabetic islets. The range of oscillatory frequencies was unchanged by glucose or diabetes. Cells within diabetic (but not normal) islets increased oscillatory regularity in response to glucose. These data support the hypothesis that glucose enhances metabolic coupling in normal islets and that the dampening of oscillatory insulin secretion in NIDDM may result from disrupted metabolic coupling.

11 Read more

Islet protection and amelioration of diabetes type 2 in Psammomys obesus by treatment with cannabidiol

Islet protection and amelioration of diabetes type 2 in Psammomys obesus by treatment with cannabidiol

We decided to examine the effects of CBD in the Psam- momys obesus, a model of type 2 diabetes, since CBD inhibits the production of IL-1b, TNF-α and IFN-γ, cyto- kines that are involved in the beta cells destruction lead- ing to diabetes. The Psammomys obesus in nature feeds on salt bush, which supply most of its nutrients and water. When they are fed a high-energy (HE) diet, they develop diabetes. The Jerusalem colony of Psammomys obesus was established from animals from the Dead Sea region. Generally four stages of consecutive progression to dia- betes in this species are defined, namely Stage A: Basal normoglycemia and normoinsulinemia. Stage B: Hyper- insulinemia (ranging from 120 to 300 mU/L), while ani- mals remain normoglycemic and gain weight. Stage C: Documentation which entails a marked hyperglycemia together with both hyperinsulinemia and hyperproinsu- linemia and further obesity. Stage D: (6 - 12 weeks after stage C) Low plasma insulin, increase of blood glucose, hyperlipidemia, and body weight loss [14].

8 Read more

Comparative Toxicity of Methanolic Extracts of some Indigenous and Exotic Flowers against Subterranean Termites Odontotermes obesus (Isoptera: Termitidae)

Comparative Toxicity of Methanolic Extracts of some Indigenous and Exotic Flowers against Subterranean Termites Odontotermes obesus (Isoptera: Termitidae)

Subterranean termites (O. obesus) are destructive urban and agricultural pests being primarily controlled by persistent synthetic insecticides. The present study was aimed to evaluate the toxicity potential of methanolic extracts of eight different flowers against these termites. Results revealed that among all treatments the extracts of O. basilicum (basil) and T. stans (tecoma) flowers exhibited maximum mortality for treatment after 72 hours of application was exhibited by basil extract (55.5%) followed by tecoma (50.00%), calendula (48.00%) and others with decreased mortality. LC 50 values were inversely proportional to time interval while LT 50 values were found minimum at 40% concentrations for all treatments. Basil and tecoma found to be most effective floral extracts among all the utilized treatments.

6 Read more

Biology and Morphometrics of Cashew Stem and Root Borers (CSRB) Plocaederus Ferrugenius and Plocaederus Obesus (Coleoptera: Cerambycidae) Reared on Cashew Bark

Biology and Morphometrics of Cashew Stem and Root Borers (CSRB) Plocaederus Ferrugenius and Plocaederus Obesus (Coleoptera: Cerambycidae) Reared on Cashew Bark

The adult beetles of P. obesus were dull grey brown coloured longicorn beetles, males had the antenna more than double of the length of the body (mean 57.62±6.80 mm) whereas, in case of females, the antenna was more or less of same length as that of the body (mean 35.39±7.67mm). The antenna was filiform with scape, in antennifer, pedicel comprising of nine antennomeres with dark bands at the junction of antennomeres. The antennal segments contributed variously for the length of the flagellum. (Table 6) The beetles, when disturbed produced sound by scraping of the back edge of the pronotum against a file on the mesonotum. The beetles displayed high level of aggregation .The longevity of male beetles was statistically significantly different from P,ferrugenius (LSD=2.739@ p=0.05) but females were on par in longevity. The female adults had a higher mean body weight (1.76 g ± 0.07) than the males (1.46 g± 0.22).The duration of developmental stages were found to vary (Table 5) and percentage contribution of each stage of development was different and dominance of grub stage was observed (Fig 5) .The adult female and male beetles of two species of Plocaederus had shown statistically significant difference in the antennal morphometric details (LSD=1.795@p=0.05). The other parameters viz. body length, body weight were on par in both the sexes of both the species.

7 Read more

Effect of Sub Lethal Concentrations on Population Size
of Termites Odontotermes Obesus (Rambur) and
Coptotermes Heimi (Wasmann) Under Laboratory
and Field Conditions

Effect of Sub Lethal Concentrations on Population Size of Termites Odontotermes Obesus (Rambur) and Coptotermes Heimi (Wasmann) Under Laboratory and Field Conditions

In Pakistan this species has also been recorded to damage woodwork in buildings in various ecological areas. It attacks houses in villages more commonly than in urban areas Akhtar [14,15]. Termites become economically important pests when they started to destroy the wood and wooden products of human homes, building materials, forests, agriculture crops and other commercial products (Monica et al 2009). The major mound building termite species like Odontotermes obesus Rambur, O. redemanni Wasmann, O. wallonesis Wasmann , O. horni Wasmann, Heterotermes indicola Wasmann, Coptotermes kishori, C. heimi Wasmann, Microtermes obesi Holmgren, Trinervitermes biformis Wasmann and Microcerotermes beesoni Snyder attack the bark and heart wood of standing trees such as Butea monosperma (Lam.) Taub., Dipterocarpus indicus Bedd., Eucalyptus sp., Pterocarpus marsurpium Roxburgh, Santalum album L., Shorea robusta Roth., Terminalia bellirica (Gaertn.) Roxb. Swietenia macrophylla King., Dalbergia sissoo Roxb., Pinus wallichiana A. B. Jacks., Tectona grandis Linn.,Toona cilita M. Rome. Haldina cordifolia (Roxb.) Ridsdale etc. Rajagopal [16], Remadevi et al. [17,18] reported the possibility of CSI bait eliminating or suppressing the higher termite if the test colonies could pick up adequate lethal dose by installing more bait stations and prolonging the baiting period.

7 Read more

Histophathological Protocol To Find Out The Mode Of Action Of Fungus Beauveria bassiana (Balsamo) Vuillemin Preparation On Cuticle Of Termite Worker of Odontotermes obesus (R.)

Histophathological Protocol To Find Out The Mode Of Action Of Fungus Beauveria bassiana (Balsamo) Vuillemin Preparation On Cuticle Of Termite Worker of Odontotermes obesus (R.)

Odontotermes obesus (Rambur) (Isoptera: Termitidae) is a common termite pest found in almost all crop plants including cash crops such as maize, wheat, groundnut, rice etc. in South East part of Rajasthan (India). Presently, the control methods mostly swing towards chemical that has led to high cost, persistence and adverse effects to the environment. Biological control with pathogenic fungi is a promising alternative to chemical control against the subterranean termite. Beauveria bassiana (Balsamo) is one of the several natural agents for controlling the subterranean termite by direct penetration of the insect cuticle. Workers of the termite Odontotermes spp. (Isoptera: Termitidae) were inoculated with the entomopathogenic fungus, Beauveria bassiana by exposing the termite to viable conidia in a petri dish. The most effective dose 4.5X10 8 conidia/ml against worker was used to see its effect on cuticle. It was done by using standard histopathological protocol. Termite workers were sacrificed after 48 hrs. treating with highest dose of 4.5X10 8 conidia/ml. Transverse sections of body revealed marked changes in various insect tissues including cuticle . The target of fungus was of course the cuticular part, which was well evident by damaged exocuticle, endocuticle and deposition of conidia in large amount on the external surfaces. The analysis of the colonized termites provided an overview of the infection, showing that the hydrophobic conidia were able to adhere all over the external surface of body wall with a preference for surfaces containing spines.

12 Read more

Form and function of the bulbus arteriosus in yellowfin tuna (Thunnus
albacares), bigeye tuna (Thunnus obesus) and blue marlin
(Makaira nigricans): static properties

Form and function of the bulbus arteriosus in yellowfin tuna (Thunnus albacares), bigeye tuna (Thunnus obesus) and blue marlin (Makaira nigricans): static properties

Strips of tissue were dissected from the bulbi of freshly killed yellowfin tuna and bigeye (Thunnus obesus L.) tuna. The bulbi were obtained from small (<3 kg) yellowfin and bigeye tuna held in large outdoor tanks at the National Marine Fisheries Service Kewalo Research Facility in Honolulu, HI, USA. The tissue was cut into a rectangular shape, and the dimensions were measured using calipers to an accuracy of ±0.2·mm. One end was glued transversely to a piece of metal attached to a micromanipulator. The other end of the tissue was attached to a Grass force transducer (model FT03; Grass- Telefactor, West Warwick, RI, USA) to record forces produced as the material was stretched. The internal longitudinal elements were tested as intact structures. Complete strips of the wall were stretched in both longitudinal and transverse directions. The outer, adventitial layer of the wall and the inner, medial layer were dissected free and tested individually. Extensions of the strips occurred in steps and the length was measured with calipers. Once force and extension had been recorded, the values of stress, strain and modulus were calculated as described below.

16 Read more

Production of simulated caviar using Bigeye Tuna (Thunnus obesus) roe: Pilot scale study to promote fish roe based value addition sector in Sri Lanka

Production of simulated caviar using Bigeye Tuna (Thunnus obesus) roe: Pilot scale study to promote fish roe based value addition sector in Sri Lanka

Abstract - Simulated caviar also named as imitation caviar, is defined as salted roe that comes from a fish except sturgeon fish. Fish roe is removed as a by-product from processing plants and doesn’t have a high demand in Sri Lanka at present. It is essential to add value to fish roe which is of low demand at present and enhance the income of fish processing industries and suppliers. Since Bigeye tuna (Thunnus obesus) is one of the most commercially important tuna fishery resources in Sri Lanka, Bigeye tuna was used as the resource species for the present study. Fish roe samples were subjected to “dry salting” method for different treatments with salt (g): fish roe (g) ratios as Treatment 01 - 0.25: 1.00, Treatment 02 - 0.50: 1.00 and Treatment 03 - 0.75: 1.00. Most appropriate treatment was assessed using sensory evaluation, proximate analysis, pH test and microbiological analysis. Highest average ash content ( 6.95 % ± 0.06) and maximum lipid content ( 11.89 % ± 0.88) were recorded for Treatment 03, while greatest protein value ( 25.65 % ± 0.11) was indicated by Treatment 01. Initial average pH values of the 03 treatments varied between 6.00 - 6.39 with significant difference for all 03 treatments. Treatment 03 (0.75 salt: 1.00 fish roe) has recorded lowest Total Plate Count (TPC) value for a period of 02 months with significant difference for all treatments (P < 0.05). Results of the sensory evaluation showed that best consumer preference for all parameters (color, texture, aroma, overall acceptability, mouth feel, and saltiness) were for treatment 01. Present study implicated that “dry salting” method with 0.25 salt: 1.00 fish roe by weight (Treatment 01), with proper nutritional quality (highest protein content: 25.65% / lowest lipid level: 11.50%) is most suitable processing method for simulated / imitation caviar production using roe samples of Bigeye tuna. Since Treatment 01 requires lowest salt level to process product, production cost is also minimum compare to other two treatments. Popularization of this edible source is useful to prevent mal-nutrition as nutritional rich source in rural and urban community of Sri Lanka.

6 Read more

Residency and spatial use by reef sharks of an isolated seamount and its implications for conservation

Residency and spatial use by reef sharks of an isolated seamount and its implications for conservation

In the initial proposed multi-use model, our study location, Osprey Reef (a seamount) is listed as a Habitat Protection Zone that would allow limited commercial fishing (handline/rod and reel, hand collection for the aquarium and sea cucumber trade) and recreational fishing. As with other isolated atolls and seamounts in the Indo-Pacific region, the shark assemblage at Osprey Reef is dominated by a few species [32,33]. Grey reef sharks Carcharhinus amblyrhynchos, whitetip reef sharks Triaenodon obesus and silvertip sharks Carcharhinus albimarginatus are the most common species observed [34–36]. All three species are widely distributed across the Indo-Pacific, and whitetip and grey reef sharks are the most abundant shark species on many coral reefs [37]. However, due to their slow growth and low fecundity, all three species are believed to be vulnerable to exploitation and there is some evidence of population declines over parts of their distribution range [20,37–42]. It is estimated that each year, live- aboard dive boats are directly responsible for generating at least AU$16 M worth of income to the Cairns/Port Douglas region (North Queensland) [34]. Of all the Coral Sea reef systems, Osprey Reef has the highest visitation rate by tourism operators, primarily to conduct shark dives [34]. So, the depletion of reef sharks at Osprey Reef would have financial ramifications for

12 Read more

Differential heating and cooling rates in bigeye tuna (Thunnus
obesus Lowe): a model of non steady state heat exchange

Differential heating and cooling rates in bigeye tuna (Thunnus obesus Lowe): a model of non steady state heat exchange

A detailed account of the capture and tagging procedure, size of the fish, etc. have been reported elsewhere (Musyl et al., 2003) and only brief descriptions will be given here. Adult bigeye tuna Thunnus obesus Lowe were captured using conventional longline and recreational fishing gear. On board the ship, archival tags (Wildlife Computers, Redmond, Washington, USA) were placed into the visceral cavity through a 1–1.5·cm incision, which was closed with one or two sutures and veterinary surgical adhesive. The fish were then released. The tags recorded four channels of data: internal (i.e. visceral cavity) temperature, water temperature, ambient light and depth. All channels were sampled and data stored by the archival tags once every minute.

9 Read more

Testing the Sensitivity of the Length-Converted Catch Method Using the Bigeye Tuna Thunnus obesus (Scombridae) Population Parameters

Testing the Sensitivity of the Length-Converted Catch Method Using the Bigeye Tuna Thunnus obesus (Scombridae) Population Parameters

The present study investigates how sample size, length interval size, recruitment variation, and mortality over time influence total mortality, which is estimated by applying the length-converted catch method to the bigeye tuna (Thunnus obesus) population. Given the assumption of fish dynamics under an equilibrium state, an increasing sample size and decreasing length interval size can raise the accuracy of total mortality estimates, with a sample size of 3000 individuals and length class interval of 5 cm generally producing the most accurate estimates. When fish dynamics follow a non-equilibrium state, randomly varied recruitment does not affect the estimation of total mortality. However, recruitment that varies with increasing or decreasing trends would affect total mortality remarkably. Therefore, total mortality that varies by time influences estimated total mortality, and in this situation, fish stocks that undergo stable total mortality for four successive years could produce an accurate total mortality figure. Finally, we suggest that the non-equilibrium state of fish dynamics should be considered before applying the length-converted catch method to estimate Z.

10 Read more

Show all 27 documents...