Early life history of tropical Anguilla leptocephali in the western Pacific Ocean

In order to examine the early life-history characteristics of tropical eels, otolith microstructure and microchemistry were examined in leptocephali of Anguilla bicolor pacifica (27.6-54.1 mm TL, n=20) and A. marmorata (22.0-47.3 mm TL, n=8) collected during a cruise in the western Pacific. A. bicolor pacifica occurred between 10°N and 15°N in the west and between 5°S and 10°N farther to the east. A. marmorata also occurred in two different latitudinal ranges in the Northern (15-16°N) and Southern Hemispheres (3-15°S) of the western Pacific. The increment widths in the otoliths of these leptocephali increased between the hatch check (0 days) and about an age of 30 days in both species, and then gradually decreased toward the otolith edge. Otolith Sr:Ca ratios showed a gradual increase from the otolith center to the edge. The ages of A. bicolor pacifica and A. marmorata leptocephali ranged from 40 to 128 days and from 38 to 99 days, respectively. Growth rates of A. bicolor pacifica and A. marmorata leptocephali ranged from 0.33 to 0.71 mm day^-1 and from 0.45 to 0.63 mm day^-1, respectively. These leptocephali had estimated growth rates that were spread out throughout most of the reported range of growth rates of the leptocephali of the temperate species, the Japanese eel and the Atlantic eels. Differences in the spatial distribution in relation to current systems, and the age and size compositions of the leptocephali of A. bicolor pacifica and A. marmorata suggested different spawning locations for these two species.     

Evidence of a spawning area of <Emphasis Type="Italic">Anguilla</Emphasis><Emphasis Type="Italic">marmorata</Emphasis> in the western North Pacific

Leptocephali of the tropical eel Anguilla marmorata have been consistently collected in the same area of the North Equatorial Current (NEC) in the western North Pacific during three consecutive cruises in June and July of 1991 (N=28) and 1994 (N=20), and July and September of 1995 (N=27), indicating that this is a spawning area of this species. These leptocephali were collected from 130°E to 142°E and 12°N to 20°N, to the west of the Mariana Islands, in 20 tows in 1991, in 13 tows in 1994 and in 17 tows in 1995, indicating a widespread presence, but a relatively low abundance. Six of these specimens (16.3-36.0 mm total length) from the 1995 cruise, which were of the typical size range of these leptocephali, were genetically confirmed to be A. marmorata in a previous study. The consistent presence of recently spawned A. marmorata leptocephali (9-20 mm) in all 3 years, suggests that the western region of the NEC is the spawning area of the northern population of A. marmorata that was identified in a recent population genetics study. These leptocephali would thus be transported westward by the NEC and then transported north into the Kuroshio Current and toward Taiwan and Japan, or south toward the southern Philippines and into the Celebes Sea by the Mindanao Current. Available evidence indicates that A. marmorata may have potentially year-round spawning, and the presence of a spawning area of this species in the same region as that of Anguilla japonica suggests that the northern population of A. marmorata has evolved a spawning migration from East Asia, the Philippines and the Celebes Sea region to the NEC area, but differs from A. japonica by having some individuals that recruit to more southern areas.     

Techniques to separate metal from waste printed circuit boards from discarded personal computers

Waste printed circuit boards contain valuable metals such as Au, Pd, Ag, and Cu that can be reutilized and harmful elements such as Pb, Br, and Cr that must be removed from the viewpoint of environmental conservation. In this research, we examined a method that separates the materials from printed circuit boards contained in discarded personal computers. After cutting the printed circuit boards to a size of 20 × 20 mm, they were heated at 873 K under an Ar atmosphere to remove organic resins containing elements such as C, H, and N. After heat treatment, the printed circuit boards were crushed using a planetary ball mill and the pulverized powders were filtered. The fraction with a granularity of greater than 250 μm was separated into magnetic and nonmagnetic materials by a magnetic field. Because the fraction with a granularity of less than 250 μm contained 39 mass% of C, it was heated at 1273 K in an atmosphere of 95% Ar and 5% O₂ to allow carbon combustion to take place, followed by metal reduction processing at the same temperature in an atmosphere of 97% Ar and 3% H₂. The basicity of the resulting powder was adjusted and the powder was heated at 1773 K under an Ar atmosphere. The proposed method separated the slag and metal, and 80% of the valuable metals contained in printed circuit boards could be collected.     

Growth history and inshore migration of the tropical eel, Anguilla marmorata, in the Pacific

A comparative study of the otolith microstructure and microchemistry of Anguilla marmorata glass eels in the western North Pacific (Japan, Taiwan, the Philippines, Indonesia) determined the timing of metamorphosis and age at recruitment to freshwater habitats with a view to learning about the early life history and recruitment of this species of tropical anguillid eel, which has a wide range throughout much of the western Pacific and parts of the Indian Ocean. Three new samples (from Japan, Taiwan, Indonesia) were analyzed and statistically compared along with two other previously published samples that were analyzed using the same techniques. Ages at metamorphosis and recruitment, respectively, were 123ᆡ.4 days (mean-SD) and 154ᆥ.0 days in specimens from Japan, 116ᆢ.6 days and 145ᆣ.6 days in those from Taiwan, 120ᆡ.0 days and 154ᆡ.5 days in the Philippines stock and 132Nj.7 days and 159ᆟ.7 days, and 120ᆣ.6 days and 152ᆣ.2 days in the Indonesian stock. The average duration of the period of metamorphosis estimated from otolith microstructure was very similar (15-17 days) in the specimens from all locations. A close linear relationship was found between the ages at metamorphosis and recruitment at all locations, suggesting that individuals that metamorphosed earlier were recruited to freshwater habitats at a younger age. Back-calculated hatching dates ranged over about 6 months of the year, suggesting that this species may spawn throughout much of the year. It is hypothesized that specimens from all four sites are from the same spawning population originating in a spawning area in the North Equatorial Current of the western North Pacific.     

New clues for freshwater eels (<Emphasis Type="Italic">Anguilla</Emphasis> spp.) migration routes to eastern Madagascar and surrounding islands

A total of 4,172 freshwater eels have been collected by electrofishing in upper estuaries from Madagascar (East coast), Mascarene (Réunion and Mauritius Is.), Comoros (Mayotte Is.) and Seychelles (Mahé and Praslin Is.) Archipelagos, between October 2003 and February 2006. Eel species composition in the sampling stations was contrasted between eastern Madagascar (Anguilla mossambica 96.0%, A. marmorata 3.9% and A. bicolor bicolor 0.2%), the Comoros (A. marmorata 56.1% and A. bicolor bicolor 43.9%), the Mascarene (A. marmorata 91.4%, A. bicolor bicolor 5.4% and A. mossambica 3.2%) and the Seychelles Archipelagos (A. bicolor bicolor 100.0%). This gradient in species composition, even concerning the short time-range of our sampling, argued for separate migration routes between species. A total of 168 eels were aged by reading their otolith microstructure, and otolith growth rates were calculated from pre-leptocephalus stage (post-hatching) to metamorphosis, until freshwater check. For all species, mean otolith growth rate (OGR) was related to specific migration routes: A. bicolor bicolor is distributed in the lowest latitudes and showed the highest OGR during leptocephalus stage, whereas A. mossambica, endemic of the Malagasy area, has the most southern distribution and showed the lowest OGR. OGR during leptocephalus stage was negatively correlated to the leptocephalus stage duration, showing a decrease of global metabolism with time, classical in leptocephali. This relationship was found significant for A. marmorata and A. mossambica, probably because all these larvae crossed successively the same environments, but not for A. bicolor bicolor, probably because their larvae crossed different pelagic environments, opening the hypothesis of larvae from different origins.     

Phylogeny and biogeography of Sicydiinae (Teleostei: Gobiidae) inferred from mitochondrial and nuclear genes

In the Indo-Pacific area, the Caribbean region and West Africa, insular systems are colonised by particular Gobiids of the Sicydiinae subfamily. These species spawn in freshwater, the free embryos drift downstream to the sea where they undergo a planktonic phase, before returning to rivers to grow and reproduce; an amphidromous lifestyle. These gobies are the biggest contributors to the diversity of fish communities in insular systems and have the highest levels of endemism, yet their phylogeny has not been explored before with molecular data. To understand the phylogeny and the biogeography of this subfamily, sequences from the mitochondrial 16S rDNA and cytochrome oxidase I and from the nuclear rhodopsin gene were obtained for 50 Sicydiinae specimens of seven genera. Our results support the monophyly of the subfamily and of all the genera except Sicyopus, which is polyphyletic. Five major clades were identified within this subfamily. One clade clusters Sicyopterus and Sicydium as sister genera, one contains the genus Stiphodon split into two different groups, two other clades include only Sicyopus (Smilosicyopus) and Cotylopus, respectively, and the last clade groups Akihito, Lentipes and Sicyopus (Sicyopus). As a result, the subgenus Smilosicyopus is elevated herein as a genus. A molecular dating approach helps the interpretation of these phylogenetic results in terms of amphidromy and biogeographical events that have allowed the Sicydiinae to colonise the Indo-Pacific, West African and Caribbean islands.     

Dramatic effect of pop-up satellite tags on eel swimming

The journey of the European eel to the spawning area in the Sargasso Sea is still a mystery. Several trials have been carried out to follow migrating eels with pop-up satellite tags (PSATs), without much success. As eels are very efficient swimmers, tags likely interfere with their high swimming efficiency. Here we report a more than twofold increase in swimming cost caused by a regular small satellite tag. The impact was determined at a range of swimming speeds with and without tag in a 2-m swimming tunnel. These results help to explain why the previous use of PSATs to identify spawning sites in the Sargasso Sea was thus far unsuccessful.     

Variation in migratory history of Japanese eels,<Emphasis Type="Italic"> Anguilla japonica</Emphasis>, collected in coastal waters of the Amakusa Islands,Japan, inferred from otolith Sr/Ca ratios

In order to examine the variation in migratory history of the Japanese eel, Anguilla japonica, we measured otolith strontium (Sr) and calcium (Ca) concentrations by X-ray electron microprobe analysis in 5 yellow eels and 20 silver eels collected in the coastal waters of the Amakusa Islands during the spawning migration season. Three migratory types categorized as river eels, estuarine eels and sea eels were found. Estuarine eels were dominant (52%), sea eels were the second most abundant (28%), followed by river eels (20%). The low proportion of river eels from the spawning migration season suggested that the estuarine and sea eels that inhabit the nearby coastal areas might make a larger reproductive contribution to the next generation in this area, although similar analyses should be made over the wide-range geographic distribution of this species, to provide better estimates of the reproductive contributions by different migratory patterns of the population.     

Studies on transitory laxative effects of sorbitol and maltitol: II: Differences in laxative effects among various foods containing the sweetening agents

We studied the laxative effect of sweetening agents, hydrogenated glucose syrup (HGS) containing 88–92% maltitol, and sorbitol contained in various foods. The subjects were 89 volunteers (64 males and 25 females). Foods used in the study were tablets, bevarages, chewing gum, jelly, adzuki-bean jelly, chocolate and candies which contained one of the two sweetening agents.The doses of the sweetening agents were 0.4 g/kg for sweets in tablet form and 20 g for the other foods. Approximately 10% of the subjects exhibited diarrhea after taking tablets as a control; approximately 20% did so after taking HGS except for adzuki-bean jelly; and approximately 30% did so after taking sorbitol. There was no significant difference between HGS and the control substance. The incidence of diarrhea tended to be higher with the two sweetening agents only when contained in adzuki-bean jelly. The length of time between the ingestion of test substances and the first onset of diarrheal stool varied widely from less than one hour to 23 hours among individuals. However, adzuki-bean jelly diarrhea was induced within 5 hours in all subjects. Soft stool accounted for 60 – 90% of the macroscopic findings of diarrheal stool. Chief complaints of abdominal symptoms were gurgling, flatus and lower abdominal pain.