Deep-sea Sharks Research Articles

Washing formaldehyde from fixed spirit specimens: a mechanism for the preservation of Megamouth III

The discovery in August 1988 of a rare and massive deep-sea dwelling shark, megachasma pelagios, or megamouth presented the Western Australian Museum with a unique opportunity to study and exhibit the massive 5.2 m, 700 kg shark. In order to ensure that the formalin-preserved specimen was safe to handle and install in a custom-made polyester and fibreglass exhibition tank, it was essential to establish how long it would take to reduce the amount of formaldehyde in the shark to a safe level. Tests on a small shark established that formaldehyde diffuses from the preserved specimen in accordance with the logarithm of the washing time. The same mechanism controlled the release of formaldehyde on Megamouth III and this facilitated a compliant installation procedure. Hazards associated with the exhibition of more than 10,000 L of 70% aqueous ethanol and methods for purification of old storage solutions are reported. The extended washing resulted in a safe amount of formaldehyde being found in the storage solution even after 13 years on exhibition. Conservation challenges and proposed new display methods are also discussed.

Mitochondrial cytochrome b variation in sleeper sharks (Squaliformes: Somniosidae)

Sleeper sharks are a poorly studied group of deep-sea sharks. The subgenus, Somniosus, contains three morphologically similar species: S. microcephalus found in the Arctic and North Atlantic; S. pacificus in the North Pacific; and S. antarcticus in the Southern Ocean. These sharks have been reported mainly in temperate to polar waters and occasionally in subtropical locations. They have not been recorded in tropical waters. This study investigates the relationships among the accepted species of Somniosus through analysis of mitochondrial cytochrome b sequence variation. Seventy-five samples were examined from four sampling locations in the North Pacific, Southern Ocean and North Atlantic. Twenty-one haplotypes were found. A minimum spanning parsimony network separated these haplotypes into two divergent clades, an S. microcephalus and an S. pacificus/antarcticus clade, strongly supporting the distinction of S. microcephalus as a separate species from the Pacific sleeper shark species. Analysis of genetic structure within the S. pacificus/antarcticus clade (analysis of molecular variance, allele frequency comparisons, and a nested clade analysis) showed limited or no differences amongst three populations. Further examination of genetic variation at more variable mtDNA and nuclear markers is needed to examine the species status of S. pacificus and S. antarcticus.

A deep-sea shark assemblage from the Miocene in, southwest of Gunma Prefecture, central Japan and the biogeographical significance

A deep-sea shark assemblage from the Miocene in, southwest of Gunma Prefecture, central Japan and the biogeographical significance

Occurrence of polybrominated diphenyl ethers and polychlorinated biphenyls in shark liver oil supplements

Results are reported of a pilot survey of concentrations of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) in shark liver oil supplements. Eleven brands of dietary supplements were analysed using an isotope dilution GC/MS method. Total concentrations of 10 PBDE congeners (BDE-28, −47, −49, −66, −99, −100, −153, −154, −155 and −183) ranged from 0.1 to 53 ng g−1 oil weight and total concentrations of six PCB congeners (CB-28/31, −52, −118, −153 and −180) in the samples ranged from 16 to 340 ng g−1 oil weight (undetected values are not included). Two brands of Japanese deep-sea shark liver oil contained the highest levels of PBDEs (49–53 ng g−1 oil weight) and PCBs (290–340 ng g−1 oil weight). These results indicate that PBDEs may have entered Japanese deep-sea waters.

Gilquiniid cestodes (Trypanorhyncha) from elasmobranch fishes off New Caledonia with descriptions of two new genera and a new species

Cestodes were collected from deep-sea sharks caught off New Caledonia, South Pacific. Vittirhynchus squali n. g., n. sp. (Trypanorhyncha: Gilquiniidae) is described from the spiral valve of Squalus melanurus Fourmanoir & Rivaton. The new genus possesses four bothria and a typical heteroacanthous metabasal armature but has a file of three macrohooks forming a short chainette on the internal surface of the basal armature. Sagittirhynchus aculeatus n. g., n. sp., from the spiral valve of Centrophorus sp. (undescribed), also has four bothria and a typical heteroacanthous armature but lacks a distinctive basal swelling and has the final hooks of each principal row prominently enlarged. Gilquinia minor n. sp., from the spiral valve of Centrophorus sp. (undescribed), is distinguished by the presence of only five hooks per principal row compared with eight in congeners. Gilquinia sp. is reported from Squalus melanurus. G. robertsoni Beveridge, 1990 is reported from S. megalops (Macleay).

Vitellogenesis in the deep-sea shark Centroscymnus coelolepis

At present, information on the reproductive physiology of Centroscymnus coelolepis, which is one of most important and widespread deep-sea shark species, is completely lacking. In this study, we investigated vitellogenesis, a key step in the reproduction biology of fishes. Specimens of C. coelolepis were collected at 2850 m depth in the Western Mediterranean Sea. The size of the collected sharks (range: 35.5–65.0 cm TL) was much lower than those typically reported for the Atlantic and Pacific Oceans. The marked distinctiveness of Mediterranean and Atlantic/Pacific populations was reflected by the achievement of sexual maturity at a smaller size in Mediterranean specimens. The examination of cytoplasmatic components of oocytes indicated that vitellogenin uptake in the ovary started when oocytes reached 14 mm in diameter. Only reproductive females displayed a significant relationship between plasmatic vitellogenin and gonadal development, suggesting that vitellogenesis in C. coelolepis is a discontinuous process. Oestradiol levels were tightly coupled with gonadal development, underlining the importance of this hormone in controlling vitellogenesis. All these findings suggest that vitellogenesis in this yolk-sac viviparous shark might occur with similar mechanisms of oviparous vertebrates.

Pregnancy in Squaliolus laticaudus (Elasmobranch: Dalatiidae) from Brazil

A pregnant female of the Dwarf deep-sea shark, Squaliolus laticaudus with four embryos was caught by the nocturnal longline vessel “Progressao” from southern Brazil, on September 1999. It was donated by the fishermen. Embryos ranged in size 105 – 100 mm of total length. The aim of this article is to contribute to the knowledge of the Dwarf deep-sea shark reproduction and distribution on the Brazilian coast. It is been considered the first record to know about pregnant Dwarf deep-sea shark in the world.

Lipid content and fatty acid distribution in tissues from Portuguese dogfish, leafscale gulper shark and black dogfish

The lipid characterization in tissues from the three deep-sea sharks leafscale gulper shark ( Centrophorus squamosus), Portuguese dogfish ( Centroscymnus coelolepis) and black dogfish ( Centrocyllium fabricii) captured at Hatton Bank in the North Atlantic were examined. The objective was to determine the lipid content and the fatty acid composition in different tissues. In addition, the fatty acid composition in tissues and species was compared. The tissues examined were pancreas, heart, kidney, stomach, spleen and liver. The lipid content was high in liver (40–50%) and ranged from 1% to 5% in the other tissues. The dominant fatty acids were C16:0, C18:1 (n-9), C18:1 (n-7) and C22:6 (n-3) in all tissues. All tissues had a high content of unsaturated fatty acids.

Chemical characterisation of eggs from deep-sea sharks

The chemical characterisation and nutritional value of eggs from the five deep-sea sharks leafscale gulper shark ( Centrophorus squamosus), greater lantern shark ( Etmopterus princeps), longnose velvet dogfish ( Centroscymnus crepidater), Portuguese dogfish ( Centroscymnus coelolepis) and black dogfish ( Centrocyllium fabricii) captured at Hatton Bank in the North Atlantic were examined. The chemical composition was quite similar for all the eggs studied. The dominant fatty acid in all the eggs was the monounsaturated fatty acid C18:1, which varied from 27–39%. The eggs had a relatively high content of C16:0 (13.0–18.5%) and C22:6n-3 (10.3–15.1%). The two main lipid classes in the eggs were triacylglycerols (36–55%) and phospholipids (34–41%). The eggs had high amounts of vitamin A and E. The shark eggs were particularly rich in the amino acids aspartic acid, glutamic acid, leucine and arginine.

Utilization of Deep-sea Sharks at Hatton Bank in the North Atlantic

Utilization of Deep-sea Sharks at Hatton Bank in the North Atlantic

Reduction of elasmobranch by-catch in the hake semipelagicnear-bottom longline fishery in the Algarve (Southern Portugal)

: Elasmobranch fish, particularly deep-sea sharks, are the mostimportant component of the by-catch of the hake semipelagic near-bottom ‘pedra-e-bola’ longlinefishery in the Algarve (South Portugal) and most of these fish arediscarded. The effects of the removal of the lower hooks were evaluated,in terms of target and by-catch reductions, by quantifying the catchesof each hook relative to the distance from the bottom. The analysisshowed that most European hake (Merluccius merluccius), thetarget species of this fishery, were caught in the middle rangeof the hooks, with very few individuals caught near the bottom,whereas for sharks the situation was the opposite, with most hookednear the bottom. The removal of the lower three pairs of hooks wouldresult in a small reduction in the catch of the target species,but a much more significant reduction in elasmobranch by-catch.In the specific case of the blackmouth catshark (Galeus melastomus),discard mortality would be further minimized due to the fact thatthe lower hooks capture significantly smaller animals that are alwaysdiscarded compared with hooks that are more distant from the bottom.

Sex difference in liver-oil concentration in the deep-sea shark, Centroscymnus coelolepis

Percentages of liver oil, squalene in oil and squalene in liver from fifty-seven individuals of Centroscymnus coelolepis, a deep-sea shark from the North African Atlantic Ocean near Tenerife (Canary Island), were measured. The percentages were in the range of 46.9–93.9 for liver oil, 35.5–62.2 for squalene in oil and 21.5–48.5 for squalene in liver. The liver-oil and squalene contents were related to the sex, maturity, size and catch depth of the sharks. Sex had a clear influence on the concentration of squalene levels found. Samples separated into two groups, according to their sex, when principal component analysis (PCA) was applied. Centroscymnus coelolepis males have greater economic value than females because they are easier to capture and have the highest squalene content.Resumen. Se han medido los porcentajes de aceite y escualeno contenidos en el hígado de 57 tiburones del género Centroscymnus coelolepis, capturados en aguas profundas del Océano Atlántico, cerca de Tenerife (Islas Canarias). Los porcentajes oscilaron entre 46.9 y 83.9 de aceite en hígado; 37.5 y 62.2 de escualeno en aceite y 21.5 y 48.5 de escualeno en hígado. Se ha relacionado el sexo, la madurez, tama�o y profundidad de pesca de los tiburones con el contenido en aceite y escualeno. Los resultados han mostrado que el sexo tiene una clara influencia en la proporción de este último. Cuando se aplicó el análisis de componentes principales (PCA), las muestras se separaron en dos grupos de acuerdo con su sexo.

Fractionation of Lipid Mixtures by Subcritical R134a in a Packed Column

Deep-sea shark liver oil was fractionated by subcritical R134a in a pilot-scale continuous packed column with the aim of evaluating the potential of R134a as a near-critical solvent for extracting valuable substances from lipid mixtures. Fractionation was carried out at 6.0 MPa and in the temperature range of 333−353 K. The solvent-to-oil flow ratio was varied in the range 25−100, and its influence on the fractionation efficiency was evaluated. A high separation factor between squalene and the triglyceride fraction was achieved. The R134a solvent was regenerated in two consecutive separation vessels, held at the same pressure but different temperatures, which gave a relative enrichment in squalene content in the second separation product. A model mixture of oleic acid and squalene was also fractionated by subcritical R134a at 6.0 MPa and in the temperature range of 333−353 K. Minimal separation was achieved between these two compounds, which correlates with the almost identical solubilities of the two pure substances in subcritical R134a. Mass transfer models with different hydrodynamic considerations were used to model the shark liver oil fractionation behavior in the pilot-scale column. Both models overpredicted the mass transfer coefficients as compared with the experimental values. A model based on laminar film flow of the dispersed phase gave the closest agreement to the experimental mass transfer coefficients and holdups.

Changes in Composition During Embryo Development of the Gulper Shark, Centrophorus Granulosus (Elasmobranchii, Centrophoridae): An Assessment of Maternal-embryonic Nutritional Relationships

Centrophorus granulosus is a deep sea shark that reproduces through aplacental viviparity. Its fecundity is one of the lowest described with only one embryo in a pregnancy lasting about two years. Its mature ovarian egg reaches one of the largest cellular sizes (> 350 g) described for any animal species. A previous report suggested a loss of organic matter during development of about 50% (Ranzi 1932), the highest rate reported for any elasmobranch. We measured the amounts of water, organic and inorganic matter in a complete series of embryos, by drying and later incinerating separately the external yolksac, eviscerated body, internal yolksac, liver and digestive tract. Wet weight of uterine ova ranged from 143.2–370.4 g, was positively and significantly correlated with maternal size, and the size of full-term embryos increased with maternal size. A graphical method was developed to allow weight comparison between uterine ova and full-term embryos while taking into account the initial variability in uterine ova size. Total wet weight of the embryo system increased during development by +31/+34%. Changes in percentage composition (from initial values) were: water +99/+101%; organic matter −18/−25%; inorganic matter +114/+170%. The rate of decrease of organic matter was much lower than previously suggested, and was similar to values described for oviparous species. These results suggest that C. granulosus is a strictly lecithotrophic species, with no maternal contribution of organic matter during development, although the female does provide both water and inorganic material. Other factors that might influence the accuracy of this assessment are discussed.

Solubility of Squalene, Oleic Acid, Soya Oil, and Deep Sea Shark Liver Oil in Subcritical R134a from 303 to 353 K

The solubilities of lipids typically found in marine oils and seed oil refining byproducts were measured in subcritical R134a to determine whether R134a could be a viable, low-pressure alternative to supercritical CO2. The solubilities of squalene, oleic acid, soya oil, and deep sea shark liver oil in subcritical R134a were measured in a countercurrent packed column apparatus over the temperature range 303 to 353 K at 60 bar. Solubility measurements were also made over the pressure range 40−200 bar at 343 K for shark liver oil and oleic acid. The solubilities of all solutes in R134a were low, ranging from 0.8 to 10 g of solute per kg of solvent. The solubilities increased almost linearly with increasing temperature at fixed pressure and increased logarithmically with increasing pressure at fixed temperature. The measurements show that R134a can be used as an alternative to supercritical CO2. The strong temperature dependence of the solubility allows for two-stage fractionation of extracts. Solubility as a function of individual solute type increased with decreasing polarity and decreasing molecular weight. The fractionation of deep sea shark liver oil and technical-grade oleic acid was observed in the solubility determinations. Lower-molecular-weight components were concentrated in the extract (R134a-rich phase), and high-molecular-weight components in the raffinate (lipid-rich phase). A linear solvation energy relationship approach was used to correlate the enhancement factors of the solutes as a function of the solvent polarity/dipolarizability factor. Linear relationships were obtained, but the dependence of the enhancement factor on other solute−solvent parameters could not be determined.

Trace metals in vertebral columns of deep-sea teleost fish.

Deep-sea teleost fish were collected from the Sagami Bay near a deep fissure in the Pacific Ocean. Fish were identified as Chlorophthalmis albatrosis, Engyprosopan xystrias, Satyrichthys hians, Ventrifossa garmani, and Halieutaea stellata. The Etmopterus lucifer is not a teleost, but a deep-sea shark. Just after being caught and fixed in neutral 20% formol, the vertebral column was resected and prepared for measurement by inductively coupled plasma-atomic emission spectrometry. Trace elements were found to be Al, Si, Ti, Fe, Cu, Cd, Zn, and Hg at micrograms per gram levels. Major elements were Mg, Ca, P, and S at the milligram per gram level. Some of trace elements, Zn and Hg, were also usually found at this level.

Fractionation of fish oils using supercritical CO 2 and CO 2+ethanol mixtures

This work reports the countercurrent extraction and fractionation of a range of crude fish oils using supercritical carbon dioxide and carbon dioxide+ethanol mixtures. Vitamin A palmitate was extracted from model Cod liver oil/vitamin mixtures using pure CO 2. The separation factor was low, due to similar solubilities of the vitamin ester and the oil. Vitamin A was also recovered from Cod liver oil ethyl esters\\vitamin A mixtures. The separation factor was substantially improved over the non-esterified oil, due to large differences in the solubilities of the esters and vitamin A in supercritical CO 2. Solubilities of fish oils and squalene are reported using CO 2+ethanol mixtures at 333 K, ethanol concentrations from 0 to 12% by mass and pressures from 200–300 bar. Solubilities of all oils and squalene increased exponentially with linear increases in the ethanol concentration. The solubility of polar components increased more rapidly than non-polar components. Pilot scale removal of fatty acids from Orange Roughy oil and squalene from deep sea shark liver oil was carried out using CO 2+ethanol as the solvent. The extent of fatty acid removal from Orange Roughy oil was superior to pure CO 2, whereas the degree of separation of squalene from shark liver oil was inferior. Throughput was substantially increased relative to pure CO 2 in both cases. Mass transfer behaviour and product purity results are also presented for the demonstration scale production of squalene and diacyglycerylether fractions from deep sea shark liver oil using pure CO 2. Fractionation results are compared with previous experimental results obtained at a laboratory and pilot scale to obtain the height of a transfer unit (HTU) and packed height required as a function of scale. Modelling of flooding at supercritical conditions was carried out to enable optimal design of the packed column. A liquid–liquid flooding model gave reasonable correlation of literature flooding data, obtained at a laboratory and pilot scale.

Lipid composition of the liver oil of deep-sea sharks from the Chatham Rise, New Zealand

Deep-sea sharks approach neutral buoyancy by means of a large liver that contains large amounts of low-density lipids, primarily squalene and diacyl glyceryl ether (DAGE). As an animal increases in size and matures sexually, many biochemical changes take place within the animal. It was hypothesized that maintenance of neutral buoyancy in deep-sea sharks involves fine-scale changes in the chemical composition of the liver oil as individual sharks grow and develop. To test this hypothesis, the lipid composition of liver oil for individuals of different size and sex of deep-sea sharks from the Chatham Rise, New Zealand was compared. The composition of liver oil varied within and among species. Several species contained large amounts of squalene and DAGE, whereas only traces of these lipids were present in other species. The amounts of squalene and DAGE in liver oil were inversely related, and squalene content tended to decrease as sharks increased in size. Species with high squalene levels (>80%) in liver oil were not abundant on the Chatham Rise, although levels of DAGE (a lipid of increasing commercial interest) were elevated in many species. Maintenance of neutral buoyancy in deep-sea sharks appears to involve changes in the composition of low-density liver lipids as the sharks increase in size and mature.

Reproductive biology of two deep-water sharks from the British Isles, Centroscymnus coelolepis and Centrophorus squamosus (Chondrichthyes: Squalidae)

The reproductive biology of two aplacental viviparous deep sea sharks, Centroscymnus coelolepis and Centrophorus squamosus has been studied from 1735 and 675 specimens respectively, collected with bottom trawls between 600 and 1400 m depth off the west coast of the British Isles. A macroscopic maturity scale indicates that for both species, size at first maturity is greater in females than in males. In Centroscymnus coelolepis, genital maturity occurs at an average length of ∼86 cm for males and ∼102 cm for females. In Centrophorus squamosus, males are mature near 98 cm and females near 124 cm total length (TL). Smallest juveniles of both species are absent from catches: no specimens of Centroscymnus coelolepis shorter than 58 cm, nor specimens of Centrophorus squamosus shorter than 84 cm have been recorded. Ovarian fecundity is higher in Centroscymnus coelolepis than in Centrophorus squamosus. A maternal supply has been demonstrated for Centroscymnus coelolepis. Litter size has been estimated only in C. coelolepis because no pregnant females of Centrophorus squamosus were recovered. A dwarf embryo and a pair of twins have been observed. Segregation by sexual stage of development shows that immatures are generally found at greater depths than adults.

Buoyancy in Marine Fishes: Direct and Indirect Role of Lipids

SYNOPSIS. The major lipids that have a direct role in buoyancy of marine fish are wax esters, squalene, and alkyldiacylglycerols. Wax esters are stored extracellularly in certain fishes, such as the orange roughy ( Hoplostethus atlanticus ), and therefore buoyancy appears to be their sole function. Some myctophid fishes have wax-invested swimbladders, where the non-compressible wax esters may aid in diurnal vertical migration, by replacing compressible swimbladder gases. Squalene is metabolically inert in the livers of certain sharks, and therefore probably has buoyancy as its only function. Alkyldiacylglycerols (DAGE) are abundant components of liver oil of certain deep sea sharks and holocephalans, where they may have an important role in buoyancy. Triacylglycerols and cholesterol are lipids that have an indirect role in buoyancy of marine fish. Many fishes in the ocean have oil-filled bones (mostly triacylglycerols). Although this oil aids buoyancy, its major function is as an energy storage lipid which can be utilized during starvation. Cholesterol, which is found in high amounts in the lipid-rich membranes of the swimbladder of deep sea fishes, may aid buoyancy by combining with oxygen gas in the swimbladder membranes to facilitate gas secretion in fish at great depths in the ocean. Further research is needed to understand the physical state of lipids, such as wax esters at deep sea temperatures and pressures, and more evidence is needed to clarify the role of cholesterol-rich membranes in swimbladders of deep sea fishes.