Search

It is difficult to keep a large number of cultured octopuses together in the same holding tank due to the high incidence of cannibalism. Appropriate shelters within which the octopuses can more readily avoid their peers are expected to ameliorate this problem. Shelters can be constructed from square plates assembled with appropriate spacing (gap) between them. The purpose of this study was to ascertain the optimum plate orientation and gap width between plates for shelters to maximize the accommodation of octopuses. It was found that the number of shelter occupants increased with the number of gaps available, such that more than half of the individuals in the experimental tank used the same shelter simultaneously. Octopuses tested singly to determine preferences for shelters placed vertically or horizontally preferred the vertical arrangement. Octopuses of more than 300 g tested singly in aquaria given shelters with different gap widths (20–100 mm) were found to not enter shelters with gap widths of 20 or 40 mm. It is concluded that octopus shelters constructed from square vertical plates spaced with gap widths suitable for octopuses are a useful contribution towards maximizing the number of octopuses that can be maintained in culture conditions.

Shear experiments on mortise and tenon joints with top and bottom notches in the beam end were conducted with the length of the tenon as a variable. In addition, material experiments were performed to investigate the structural performance of the fracture modes of the joint. The experimental results show that when the lower notch at the beam end experiences splitting, the shear forces were identical for different tenon lengths and did not decrease. In addition, the deformation performance of the joint up to yielding was largely due to the compressive deformation perpendicular to the grain of the wood on the sides of the tenon. Based on the theory of the calculation method of the splitting strength of a notched beam, a formula for the splitting strength when the end of the beam is moment-resisting was proposed. It was confirmed that the proposed formula could estimate the shear force that caused the splitting fracture of the lower notch. In addition, the increase in shear force after the lower notch experienced splitting fracture was due to the increase in clamping force of the beam end due to rotational deformation.

Three-point bending tests were performed on specimens of glued laminated timber with different specimen heights to failure to determine the relationship between specimen height and bending strength under tension perpendicular to the grain. For the three-point bending tests, two types of glued laminated timber composed of homogeneous grade timber, as specified in the Japanese Agricultural Standard, were used. The laminae used for the glued laminated timber were L80 grade Scots pine and L110 grade Scots pine. The specimens used in the three-point bending tests had dimensions of 105 mm (width) and 10–300 mm (height). The experimental results showed that the bending strength decreased as the specimen height increased, but the rate of decrease in the bending strength decreased with increasing specimen height when the specimen height exceeded 100 mm. From the relationship between the bending strength and specimen height, parameters that fit Bažant’s size-effect law were derived, and for a specimen height of approximately 100 mm, the bending strength was equal to the perpendicular-to-the-grain tensile strength.

To promote the development of cross-laminated timber (CLT) structures, the Japanese Government Notifications on Structural Design of CLT Buildings (GN 611) was issued in 2016. In GN 611, th...

Various design codes and design proposals have been proposed for glued laminated timber beams with round holes, assuming that the entire beam is composed of homogeneous-grade timber. However, in Japan, glued laminated timber composed of homogeneous-grade timber is rarely used for beams. In this study, the difference in the load-bearing capacity of glued laminated beams composed of homogeneous-grade timber and heterogeneous-grade timber with round holes when fractured by cracking was investigated experimentally and analytically. The materials used in the tests were glued laminated beams composed of homogeneous-grade Scots pine timber with a strength grade of E105-F345 and heterogeneous-grade Scots pine timber with a strength grade of E105-F300. Experiments confirmed that although the glued laminated beams composed of heterogeneous-grade timber have a lower material strength in the lamina with holes, its resistance to fracturing due to cracks associated with the holes is almost the same as that of the glued laminated beams composed of homogeneous-grade timber. The stresses acting on the holes in the laminated timber with holes of less than half the beam height were lower in the glued laminated beams composed of heterogeneous-grade timber than in the glued laminated beams composed of homogeneous-grade timber. The ratio of the stresses was found to be approximately equal to the ratio of the maximum bending stress or the maximum shear stress acting on the inner layer lamina, as determined by Bernoulli–Euler theory.

To elucidate the possibility of long chain, alkyl mid-chain diols (hereafter, mid-chain diols) in Lake Baikal sediments over the past 28 ka being paleoproxies, we studied their: (i) bound forms and compositional features, (ii) major sources and (iii) diagenesis during sedimentation. Of the seven bound forms investigated, i.e. free form (free type), three base-hydrolysable types (base-1, base-2, and base-3) and acid-hydrolysable type (acid-1 type) in solvent extractable lipids and base hydrolysable (NB) and acid hydrolysable (NA) types in non-solvent extractable (NONEX) lipids, only three, viz. free, NB, and base-3 types, were found. The relative compositions of the three types were 70–100%, 0–30% and 0–8%, respectively. The most abundant component of the free-type diols was the C 32 1,15-diol, whereas that of the base-3 and NB types was the C 30 1,13-diol. The average chain length, ratio of total amount of even chain lengths to that of odd chain lengths, the relative composition of positional isomers for each carbon number, and the diol index, obtained using the equation [C 30 1,15-diol]/([C 30 1,15-diol] + [C 32 1,15-diol]) × 100, hardly responded to reported major paleoenvironmental changes around the Lake Baikal region over the last 28 ka. Comparison of mid-chain diol compositions and their bound forms with those in possible sources suggested that the major biological source of all mid-chain diols in the sediments might be the Eustigmatophyceae class of algae. In the alga, the occurrence of mid-chain diols in the five bound forms, free, base-3, acid-1, NB and NA types, was suggested, while the acid-1 and NA types were not found in the sediments. Under the oxic depositional conditions of Lake Baikal, most of the acid-1 and NA type diols and part of the base-3 and NB type diols might be degraded and/or released free-type diols. In the anoxic sediments of the lake, the base-3 and NB diols seem to be resistant to diagenesis. All investigated parameters for the free, base-3 and NB diols in the sediments did not provide any information on paleoenvironments around the lake. On the other hand, among the fluxes of the three diol types, the base-3 type diol flux seems to have responded to the climatic events around the lake, especially over the last 15 ka. Hence, this flux might be a potential paleoproxy for the productivity of the biological source(s) and associated environmental factors.

Small heat-shock proteins (sHsps) bind and stabilize proteins denatured by heat or other stresses in order to prevent unfavourable protein aggregation. StHsp14.0 is an sHsp found in the acidothermophilic archaeon Sulfolobus tokodaii. A variant of StHsp14.0 was crystallized by the sitting-drop vapour-diffusion method. The crystals diffracted X-rays to 1.85 A resolution and belonged to space group P2(1)2(1)2, with unit-cell parameters a = 40.4, b = 61.1, c = 96.1 A. The V(M) value was estimated to be 2.1 A(3) Da(-1), assuming the presence of two molecules in the asymmetric unit. Heavy-atom derivative crystals were prepared successfully by the cocrystallization method and are isomorphic to native crystals.

Females of the swimming crab Portunus trituberculatus were cultured under natural temperature and high temperature (21°C) conditions to examine ovarian development and oviposition from autumn (October) to the beginning of breeding season in the following spring (May). Ovaries developed because of vitellogenesis of oocytes from October to December and their developmental state did not change during the overwintering period from December to March. In spring, from late March to mid May, some ovaries reached prematuration and maturation stages and ovipositions began from mid–late April under natural temperature conditions. Females reared in tanks of high temperature regimes oviposited earlier than those reared in tanks of natural temperatures. The number of days to oviposition tended to decrease with advancement of the beginning times (early February to late April) of culture of females under high temperature regimes; induced ovipositions were achieved more easily with increasing photoperiod from c. 12 h in early February to c. 14 h in late April. Therefore, it is inferred that the temperature and photoperiod are important environmental factors controlling ovarian development and oviposition.

The present study was undertaken to examine the antibacterial abilities of intestinal bacteria isolated from juveniles and larvae of Japanese flounder Paralichthys olivaceus. Newly hatched larvae of flounder were held in a 100 L plastic circular tank and fed rotifiers, Artemia nauplii and commercial feeds, depending on the developmental stage of the fish. Genera Aeromonas, Moraxella and Vibrio were predominantly isolated from the intestinal tracts of Japanese flounder at larval and juvenile stages, whereas Aeromonas, Bacillus, coryneforms, Moraxella, Pseudomonas and Vibrio were detected at high densities in live diets and artificial feeds. Antibacterial bacteria accounted for 1.7–24.3% of the intestinal isolates against Lactococcus garvieae, Pasteurella piscicida, Vibrio anguillarum and V. vulnificus. In particular, as much as 53.3% of Vibrio spp. other than Vibrio-swarmer isolated from 197-day-old juveniles inhibited the growth of P. piscicida. These results suggest that intestinal bacteria having antibacterial activity play a role in the prevention of infectious diseases.

A series of normal stages for the embryonic development of the ice goby (shiro-uo), Leucopsarion petersii, which belongs to the Perciformes, is described. Stages are based on morphological features, by utilizing the optical transparency of live embryos from the first cleavage to the hatching stage. Fertilized eggs were obtained by artificial insemination and normal embryogenesis was accomplished in a defined medium in plastic petri dishes at 19°C. Shiro-uo eggs were surrounded by a very thin and clear chorion and could be dechorionated with forceps very easily. Developmental stages were mostly comparable to those of other fish embryos described so far, but several differences were indicated, such as the third cleavage plane being horizontal, and that the length of the cleavage cycle increased gradually from the very early stages. Also, there were differences in the relative rates of organogenesis of the brain, eyes, otic vesicles, and somites when compared to the zebrafish and medaka.

The highly diverse Perciformes are the most numerous and most advanced group of the teleosts, but experimental embryology has almost completely neglected them. The ice goby (shiro-uo), Leucopsarion petersii, deserves attention as a useful species for this purpose. It is readily available commercially from fishermen, and their mature adults can be easily kept and bred in the laboratory. Its totally transparent eggs and embryos develop swiftly and easily under simple culture conditions. Cleavage is finished in 17 hr at 20°C and most organs are established in 3 days. Main stages of embryonic development and methods of handling are described.

SummarySmall heat shock proteins (sHsps) play a role in preventing the fatal aggregation of denatured proteins in the presence of stresses. The sHsps exist as monodisperse oligomers in their resting state. Because the hydrophobic N-terminal regions of sHsps are possible interaction sites for denatured proteins, the manner of assembly of the oligomer is critical for the activation and inactivation mechanisms. Here, we report the oligomer architecture of SpHsp16.0 from Schizosaccharomyces pombe determined with X-ray crystallography and small angle X-ray scattering. Both results indicate that eight dimers of SpHsp16.0 form an elongated sphere with 422 symmetry. The monomers show nonequivalence in the interaction with neighboring monomers and conformations of the N- and C-terminal regions. Variants for the N-terminal phenylalanine residues indicate that the oligomer formation ability is highly correlated with chaperone activity. Structural and biophysical results are discussed in terms of their possible relevance to the activation mechanism of SpHsp16.0.

Lactate is utilized in many biological processes, and its transport across biological membranes is mediated with various types of transporters. Here, we report the crystal structures of a lactate-binding protein of a TRAP (tripartite ATP-independent periplasmic) secondary transporter from Thermus thermophilus HB8. The folding of the protein is typical for a type II periplasmic solute-binding protein and forms a dimer in a back-to-back manner. One molecule of l-lactate is clearly identified in a cleft of the protein as a complex with a calcium ion. Detailed crystallographic and biochemical analyses revealed that the calcium ion can be removed from the protein and replaced with other divalent cations. This characterization of the structure of a protein binding with calcium lactate makes a significant contribution to our understanding of the mechanisms by which calcium and lactate are accommodated in cells.

From June 2000 to September 2001, we investigated the presence of eggs spawned in Margaritifera laevis and the seasonal changes in the gonads of Tanakia tanago. Eggs were observed from mid-March to mid-September. In females with a shrunken ovipositor, as the GSI gradually increased, most ovaries were in the prespawning phase (Oct-Mar). As the GSI increased further, most ovaries were in the early spawning phase (Mar-Jun). As the GSI gradually deceased, ovaries in the late spawning phase appeared (Jun-Sep). When the GSI was very low, most ovaries were in the postspawning phase (Sep-Oct). In males, when the GSI was low, most testes were in the early prespawning phase from Oct-Dec. As the GSI gradually increased, most testes were in the late prespawning phase (Dec-Jan). As the GSI increased further, testes were in the early spawning phase (Jan-Jun). As the GSI gradually decreased, amost testes were in the late spawning phase (Jun-Sep). When the GSI was very low, most testes were in the postspawning phase (Sep-Oct). These results indicate that T. tanago has a distinct annual reproductive cycle and is a spring-autumn spawner. Based on the relationship between reproductive activity and environmental factors, the spawning season of T. tanago appears to be initiated by increasing temperature and / or longer days in spring and to be terminated by shorter days in autumn.