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The distribution of all larval stages of the Japanese eel, Anguilla japonica, were examined using historical catch records and original data in the western North Pacific (WNP) to evaluate existing information about the larval distribution and migration of this species. A total of 148 preleptocephali, 2547 leptocephali, 6 metamorphosing larvae, and 21 glass eels were collected during 37 cruises over a 52-year period . Sampling effort was spatio-temporally biased in latitude/longitude among seasons with sampling effort being concentrated near the western margin of the subtropical gyre near Taiwan in the winter season and extensive effort occurring near the spawning area to the east near the seamount chain of the West Mariana Ridge in summer during the spawning season. The distribution of preleptocephali (4.2-8.7 mm) was limited to a narrow area around 14°N, 142°E just west of the southern part of the seamount chain, while leptocephali (7.7-62.0 mm) were widely distributed at increasing size westward in the North Equatorial Current (NEC) to the region east of Taiwan. Metamorphosing larvae (52.7-61.2 mm) were collected only in the area 21-26°N, 121-129°E to the east of Taiwan, while glass eels (51.3-61.2 mm) occurred only within or west of the Kuroshio. These distributions suggest that leptocephali begin to

Accurate quantification of plasma glucagon levels in humans is necessary for understanding the physiological and pathological importance of glucagon. Although several immunoassays for glucagon are available, they provide inconsistent glucagon values owing to cross-reactivity of the antibodies with peptides other than glucagon. To overcome this limitation, we developed a novel method to measure glucagon levels by a liquid chromatography (LC)-high-resolution mass spectrometry (HRMS) assay via parallel reaction monitoring (PRM) without immunoaffinity enrichment. Using stable isotope-labeled glucagon as an internal standard and 200 μL of plasma, the lower limit of quantification was 0.5 pM. This method was applied to measure plasma glucagon levels during the oral glucose tolerance test (OGTT) and meal tolerance test (MTT) in healthy volunteers, and its results were compared with those of sandwich enzyme-linked immunosorbent assay (ELISA) and radioimmunoassay (RIA). During the OGTT, this method showed significant suppression of plasma glucagon levels, and similar patterns were observed with sandwich ELISA and RIA. In contrast, during the MTT, plasma glucagon levels were slightly elevated according to the LC-MS/MS and sandwich ELISA results and were reduced according to RIA results. Our newly developed LC-MS/MS method overcomes a lack of specificity among currently available immunoassays for glucagon and may contribute to a better understanding of the importance of glucagon. Graphical abstract Flowchart for the extraction and quantification of glucagon in human plasma, and plasma glucagon responses in healthy volunteers quantified by the present LC-MS/MS, sandwich ELISA, and RIA during OGTT and MTT.

The location and timing of spawning of the Japanese eel Anguilla japonica was studied during two research cruises of the R/V Hakuho Maru and R/V Suruga Maru in the North Equatorial Current of the western North Pacific Ocean during June–September 1998. There were 38 A. japonica leptocephali (10.0–43.2 mm in total length (TL)) collected in three areas: 24 specimens around the Arakane and Pathfinder Seamounts in June (approx. 16°N and 143°E) and five specimens at the southernmost station (13°N) and nine specimens at the northernmost station (17°N) of a transect along 137°E in September. The average total lengths of the leptocephali were significantly different among the three areas, with those around the seamount being smallest, those at the northern station being largest, and none being collected along the easternmost 144°E transect. This and the currents in the region suggested that spawning of A. japonica occurred near some of the seamounts in the West Mariana Ridge. Back calculated spawning dates indicated that most leptocephali were born during the new moon, supporting the hypothesis that A. japonica spawns around the new moon. Analysis of otolith daily rings found a strong correlation between total length and age (r = 0.97), and the average daily growth rate was about 0.5 mm/day.

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