ALBERT

Beschreibung: We describe a new and efficient technique to grow aggregates of pure methane hydrate in quantities suitable for physical and material properties testing. Test specimens were grown under static conditions by combining cold, pressurized CH4 gas with granulated H2O ice, and then warming the reactants to promote the reaction CH4(g) + 6H2O(s→l) → CH4·6H2O (methane hydrate). Hydrate formation evidently occurs at the nascent ice/liquid water interface on ice grain surfaces, and complete reaction was achieved by warming the system above the ice melting point and up to 290 K, at 25−30 MPa, for approximately 8 h. The resulting material is pure, cohesive, polycrystalline methane hydrate with controlled grain size and random orientation. Synthesis conditions placed the H2O ice well above its melting temperature while reaction progressed, yet samples and run records showed no evidence for bulk melting of the unreacted portions of ice grains. Control experiments using Ne, a non-hydrate-forming gas, showed that under otherwise identical conditions, the pressure reduction and latent heat associated with ice melting are easily detectable in our fabrication apparatus. These results suggest that under hydrate-forming conditions, H2O ice can persist metastably to temperatures well above its ordinary melting point while reacting to form hydrate. Direct observations of the hydrate growth process in a small, high-pressure optical cell verified these conclusions and revealed additional details of the hydrate growth process. Methane hydrate samples were then tested in constant-strain-rate deformation experiments at T = 140−200 K, Pc = 50−100 MPa, and ε = 10-4−10-6 s-1. Measurements in both the brittle and ductile fields showed that methane hydrate has measurably different strength than H2O ice, and work hardens to an unusually high degree compared to other ices as well as to most metals and ceramics at high homologous temperatures. This work hardening may be related to a changing stoichiometry under pressure during plastic deformation; X-ray analyses showed that methane hydrate undergoes a process of solid-state disproportionation or exsolution during deformation at conditions well within its conventional stability field.

Beschreibung: The use of stable isotope analysis in ecological and wildlife studies is rapidly increasing. Studies include evaluating flow of nutrients in ecosystems and studying dietary composition of individual animals. Several mixing models have been developed to evaluate the relative contribution of different foods to the diet of consumers. All these mixing models require that all prey types will be significantly different in bivariate space. This requirement usually poses a problem in analyzing data of stable isotope ratios because sample sizes in most studies are small and seldom normally distributed. We propose a randomization test that we based on the K nearest-neighbor approach. Results from our simulations of power revealed that the K nearest-neighbor test appears to have high power even with small sample sizes and comparatively low displacement. The K nearest-neighbor test described here provides the preliminary statistical analysis necessary for the use of the mixing models, and therefore is a new, powerful tool for analyzing stable isotope data. In evaluating the test performance on data collected from American martens (Martes americana) and their prey on Chichagof Island, Southeast Alaska, we were able to reject our null hypothesis that all samples of prey were drawn from identical populations (P = 0.05). A program written in Pascal or S-Plus is available from the authors to evaluate the K nearest-neighbor statistic for several groups.

Beschreibung: A total of 57 comparative hauls using a rectangular midwater trawl with a fishing mouth area of 50 m2 (RMT 50) were carried out along the sides of an imaginary triangle south of Madeira in 1986. A total of 1258 cephalopods were caught, giving a mean of 22 per haul with a range from 0 to 67. The nets were used with a diver's light on the top bar which was either switched off or was operated with a 20, 70 or 150 W bulb, powered by a car battery. A significantly greater number of individuals per haul was caught with lights on than without lights, increasing from a mean of 13·5–25·1, a factor of 1·8. Similarly, the number of species caught was increased from a mean of 7 to 10·4, a factor of 1·5 and the volume of cephalopods was increased from a mean of 41·1–162·3ml, a factor of 3·9. Similar comparisons made for catches during day or night separately and on the three courses separately also showed marked increases with the lights. Samples show that increase in power of the lights increased the total number of cephalopod individuals caught. In the 12 species with more than ten individuals, in 33 of the 36 comparisons (of number of individuals, species and volumes) there is an increase with the light. The most influenced species was Taonius pavo which increased in numbers by a mean factor of 3·9 times with 20W, 4·0 times with 70W and 6·1 times with 150W when compared with the numbers caught with no light.

Beschreibung: An overview is provided of time-independent physical/chemical properties as related to crystal structures. The following two points are illustrated in this review:  (1) Physical and chemical properties of structure I (sI) and structure II (sII) hydrates are well-defined; measurements have begun on sH. Properties of sI and sII are determined by the molecular structures, described by three heuristics:  (i) Mechanical properties approximate those of ice, perhaps because hydrates are 85 mol % water. Yet each volume of hydrate may contain as much as 180 volumes (STP) of the hydrate-forming species. (ii) Phase equilibrium is set by the size ratio of guest molecules within host cages, and three-phase (Lw−H−V) equilibrium pressure depends exponentially upon temperature. (iii) Heats of formation are set by the hydrogen-bonded crystals and are reasonably constant within a range of guest sizes. (2) Fundamental research challenges are (a) to routinely measure the hydrate phase (via diffraction, NMR, Raman, etc.), and (b) to formulate an acceptable model for hydrate formation kinetics. The reader may wish to investigate details of this review further, via references contained in several recent monographs.

Beschreibung: Octopuses ( Eledone cirrhosa (Octopoda: Cephalopoda)) held in an aquarium were subjected to varying conditions of feeding and starvation to evaluate putative indices of feeding and growth. Specific growth rate (%d −1 ) was linearly related to feeding rate (% of the body mass d −1 ) in animals with a mean body mass of 250 g at 15°C. Maximum growth rates varied between 〉 2% d −1 (body weights 〈 300 g) to 〈 1% d −1 (body weights ≤ 900 g) but specific growth rates were not related to body weight. Growth rates became negative (weight loss) after one week without food. The digestive gland index (DGI) was significantly correlated with short and long-term feeding and specific growth rates, and with body weight. Muscle RNA concentration was linearly correlated with growth rate during the previous 1–3 weeks but not with feeding rate. RNA:protein ratios were not different between mid-arm and mantle sample sites but arm tip values were significantly higher. RNA:protein ratio was related to body weight only in feeding animals. It is concluded that DGI is an index of feeding rate and that RNA:protein ratio can be used as an index of recent (~ 4 weeks) growth rate.

Beschreibung: Growth in Loliolus noctiluca (Myopsida: Loliginidae) in Western Port, Victoria, Australia was studied from statolith growth increments. Tetracycline staining experiments verified previous work on tropical forms of this species that showed growth increments to be deposited daily. A logistic growth function described the relationship between length and increment number. There appear to be major differences in the form of growth, longevity and life history pattern between tropical and temperate forms of this species. These are probably attributable to differences in environmental conditions.

Beschreibung: Two large (dorsal mantle length 42.5 and 47.5 cm), mated spent females of circum‐Antarctic bathypelagic cranchiid squid Galiteuthis glacialis were caught early in March 1992 at the surface of the ice hole in the western Weddell Sea over depths 1915‐1920 m by the team of the U.S.A.‐Russian Ice Station Weddell‐I. The structure of the reproductive system of adult females is described for the first time in detail. Both were gelatinous, devoid of tentacles, with empty or almost empty stomachs. The empty spermatangia (sperm reservoirs of spermatophores) 30‐35 mm in length were distributed in the mantle tissues parallel to the mantle surface and to each other in the dorso‐anterior part of the mantle: 13 in one female, parallel to the body axis, and 20 in the other, parallel (13) or perpendicular (7) to the body axis. In the latter case, they represented probably two mating events. The spermatangia lay nearer to the inner than the outer mantle side and opened by a round window on the inner side; the skin with chromatophores above them remained intact. The spermatozoa had one flagellum and rod‐like heads, length 5.0‐5.3 μm, width 1.2‐1.5 μm. The most characteristic features are: a very simple type of blood vessel branching making each micro‐gonad currant‐like, not grape‐like; a very compact disposition of oviducal, nidamental glands and gill, forming a united complex located on both sides of the mantle cavity; and an ovary connected by mesentery along all its length with the continuation of the stomach from the caecum to the end of the gastrogenital ligament. Only immature degenerating trophoplasmatic oocytes, length 0.9‐1.4, av. 1.0‐1.2 mm, were contained in ovaries; only one mature egg (length 3.3 mm, width 2.4‐2.5 mm) was found in each female. The absence of oocytes 〈0.9 mm and 1.5‐3.2 mm indicates that the maturation of oocytes proceeds rather synchronously, one large portion of eggs (some tens of thousands) matures in a short time while others degenerate. The residual fecundity is assessed to be approximately 20,000 eggs. It is hypothesized that mating occurs shortly before spawning and that mature males do not undergo gelatinous degeneration and do not lose tentacles. Spermatophores are placed on the inner side of the female's mantle with the aid of the male's tentacles and/or arms (less probably by the penis), but the exact mode of implantation is unclear. Spawning probably occurs at depths of adult habitat (approx. 500–2500m), may be multiportional but short; the exhausted female loses neutral buoyancy, rises to the surface and dies. Rising to the surface after spawning is a common feature of females of many meso‐ and bathypelagic squids undergoing gelatinous degeneration during maturation (Onychoteuthidae, Gonatidae, Histio‐teuthidae, Cranchiidae, etc.) and may explain the common occurrence of large deep‐water squids in the stomachs of seabirds, including those incapable of diving, and marine mammals.

Beschreibung: A total of 57 comparative hauls using a rectangular midwater trawl with a fishing mouth area of 50 m 2 (RMT 50) were carried out along the sides of an imaginary triangle south of Madeira in 1986. A total of 1258 cephalopods were caught, giving a mean of 22 per haul with a range from 0 to 67. The nets were used with a diver's light on the top bar which was either switched off or was operated with a 20, 70 or 150 W bulb, powered by a car battery. A significantly greater number of individuals per haul was caught with lights on than without lights, increasing from a mean of 13·5–25·1, a factor of 1·8. Similarly, the number of species caught was increased from a mean of 7 to 10·4, a factor of 1·5 and the volume of cephalopods was increased from a mean of 41·1–162·3ml, a factor of 3·9. Similar comparisons made for catches during day or night separately and on the three courses separately also showed marked increases with the lights. Samples show that increase in power of the lights increased the total number of cephalopod individuals caught. In the 12 species with more than ten individuals, in 33 of the 36 comparisons (of number of individuals, species and volumes) there is an increase with the light. The most influenced species was Taonius pavo which increased in numbers by a mean factor of 3·9 times with 20W, 4·0 times with 70W and 6·1 times with 150W when compared with the numbers caught with no light.

Beschreibung: A specimen of Chaunoteuthis mollis (Cephalopoda: Onychoteuthidae), a mature mated female, from the Straits of Messina was examined. Measurements and indices were compared with those of Onychoteuthis banksii reported by previous authors. The differences found were attributed to the degeneration of the C. mollis specimen, due to sexual maturation. Two subocular (one under each eye) and two visceral photophores, similar to those of O. banksii , were present in the C. mollis specimen. The size of the posterior visceral photophore of C. mollis fit the regression line correlating posterior photophore diameter to mantle length in O. banksii. These results corroborate the hypothesis, put forward by other authors, that C. mollis represents the mature female of O. banksii.