Fecal metabolite analysis of Japanese macaques in Yakushima by LC-MS/MS and LC-QTOF-MS

We performed a comprehensive fecal metabolite analysis using LC-MS/MS and LC-QTOF-MS approaches as a preliminary study. Feces of Japanese macaques on Yakushima Island were collected from five monkeys at two separate locations. Using the former methodology, 59 substances such as free amino acids, nucleotides, nucleosides and nucleic acid bases, and organic acids in the citrate cycle were quantitatively detected and successfully differentiated in two different monkey groups by the concentrations of nucleic acid metabolites and free amino acids. In the latter, around 12,000 substances were detected both by positive and negative mode in each sample. Differences in signal intensities were observed between two monkey groups in the concentrations of plant secondary metabolites such as cyanogenic glycosides, flavonoids, and phenolics.     

Taste effects of oligopeptides in a Vietnamese fish sauce

ABSTRACT: A Vietnamese fish sauce Nuoc mam used in the present study was rich in oligopeptides of which nitrogen content accounted for 20% of total nitrogen. The high-molecular-weight peptide fractions fractionated by ion-exchange chromatographies and ultrafiltration enhanced sweetness and umami as well as sourness and bitterness of the fish sauce, and increased several flavor characteristics including continuity, first taste and aftertaste. Thus, it is apparent that large amounts of peptides produced during the long-term fermentation of fish sauce are responsible for the complicated taste of the sauce. From each fraction, 17 peptides in total were isolated and determined for their amino acid sequences. These di-, tri- and tetra-peptides synthesized by solid- or liquid-phase method gave any one of bitter, sour, umami taste, or practically no taste in the absence of salt. In the presence of 0.3% NaCl, however, almost all peptides showed sweet and umami tastes. Other than these 17 peptides, there existed many other kinds of peptides in the fish sauce. Thus, these peptides are thought to contribute to the overall taste of the fish sauce.     

Effects of temperature and food availability on growth rate during late larval stage of Japanese anchovy (Engraulis japonicus) in the Kuroshio–Oyashio transition region

During periods when the population size of Japanese anchovy Engraulis japonicus is large, the abundance of 1‐yr olds has been considered to be dependent on the growth and survival processes in the late larval and early juvenile stages in the Kuroshio–Oyashio transition region off northern Japan. Recent growth rates for 10 days before capture of larval and early juvenile E. japonicus were estimated and examined in relation to the surface water temperature and the available copepod density in 1997, 1998 and 1999. Late larval and early juvenile E. japonicus were distributed in the waters with temperature from 15 to 19°C and available prey density from 10 to 1000 mg dry weight (DW) m^?2 in the transition region. The late larval growth rates were found to be regulated more strongly by water temperature than by copepod density in the waters <16°C, and more strongly by copepod density than water temperature in the waters <100 mg DW m^?2 in the Kuroshio–Oyashio transition region. The recent growth rates decreased from the western waters to the eastern waters in the survey area 140–170°E in 1998, correlating with decreases of food availability to 50–100 mg DW m^?2. While in 1999, the recent growth rates were faster in the waters east of 150°E, resulting from eastward expansion of warm water ranges and high available prey density 100–400 mg DW m^?2. The key environmental factors regulating late larval growth rate of E. japonicus in the transition region seem to be spatially different between years.     

Interdecadal variations in Japanese sardine and ocean/climate

Relations between the long-term variations in numbers of Japanese sardine and in ocean/climate were studied. We examined long-term records of the spring air temperature on the north-western coast of North America (ATNA; 40–50°N, 130–110°W) reconstructed from tree rings, and the sardine catch records inferred from documents dating from 1600 to 1990. High sardine catches occurred eight times in this period, and each high catch continued for 7–45 years. We found a significant difference in mean ATNAs between the abundant and poor catch periods: high (low) catch occurred in periods of high (low) ATNA. ATNA was negatively correlated with spring sea-surface temperature east of Japan (SSTJ; 36–40°N, 150–160°E), where the sardine possibly migrate north-eastward, a relation which was confirmed from 1940 to 1990. In years when the Aleutian Low Pressure System (AL) shifted south-east and intensified, the westerly wind was strong east of Japan along the south-western edge of the AL, resulting in low SSTJ; a warm south-westerly wind blows in the west coast of North America along the south-eastern edge of the AL. If we assume that this relation between ATNA and SSTJ can be extended back to the 1600s, high (low) catches occur in the period when SSTJ is low (high). This relation between sardine catch and SSTJ is consistent with previous studies based on data from after 1900. The present results suggest that long-term variations in Japanese sardine are related to interdecadal North Pacific ocean/climate variability.     

Diel vertical migration of myctophid fishes (Family Myctophidae) in the transitional waters of the western North Pacific

The diel vertical migration patterns of adult myctophid fishes were determined in the transitional waters of the western North Pacific off Japan, using day–night sampling from 20 to 700 m depths with a commercial otter trawl in the summer of 1995. A total of 12 species belonging to 9 genera were collected. Four patterns were recognized in the diel vertical migration of 11 of the 12 species. (1) Migrants showing clear day–night habitat separation with peak abundance above 200 m at night: Symbolophorus californiensis, Tarletonbeania taylori, Notoscopelus japonicus, Diaphus theta, Ceratoscopelus warmingi, and Diaphus gigas. (2) Semi-migrants, in which part of the population often remains in the daytime habitat at night. The distribution depths of migratory and nonmigratory individuals do not overlap: Stenobrachius leucopsarus . (3) Passive-migrants, in which there is no separation of day–night habitats, but the upper limit of daytime distribution depth shifts to a shallower layer at night, probably as the fish follow migratory prey: Lampanyctus jordani . (4) Nonmigrants: Stenobrachius nannochir, Lampanyctus regalis (> 140 mm SL), and Protomyctophum thompsoni . The day–night habitat temperature ranges are also given for the 11 species. No remarkable east–west differences were seen in the vertical migration patterns compared with previous knowledge of eight of these species in the eastern Pacific. The diel migration patterns are newly described for three other species endemic to the western Pacific. The standing stock of myctophids in the study area was conservatively estimated at 18.5 ± 4.7 g m⁻² (avg. ± SD).