<p>Based on eel descent and ascent timings in the morning and evening, sunrise and sunset t... more <p>Based on eel descent and ascent timings in the morning and evening, sunrise and sunset times were estimated and used for calculating latitude (A) and longitude (B) positions of ten wild eels. Actual eels’ position is shown by red triangle. Eel positions estimated by average and equation methods (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0121801#sec008" target="_blank">Results and Discussion</a>) are shown by yellow and black circles, respectively.</p
<p>The colors and contours indicate the water temperature. No temperature data was availabl... more <p>The colors and contours indicate the water temperature. No temperature data was available for gray area. See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0121801#pone.0121801.t001" target="_blank">Table 1</a> for individual information. Midnight (inverted closed triangle).</p
<p>A to F correspond to DST1 to 6 (see <a href="http://www.plosone.org/article/info... more <p>A to F correspond to DST1 to 6 (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0102376#pone-0102376-t001" target="_blank">Table 1</a>). Note conspicuous white spots on the median naked interambulacral areas, and light colored periproctal cone with orange or red ring.</p
Recent molecular analyses revealed Palaemon paucidens De Haan, 1844 to be species complex, since ... more Recent molecular analyses revealed Palaemon paucidens De Haan, 1844 to be species complex, since three genetically distinct types (designated by types A, B and C) were detected. A mitochondrial 16S rDNA sequence of the lectotype specimen collected by P. F. von Siebold nearly two centuries ago in Japan and held in Naturalis Biodiversity Center (formerly Rijksmuseum van Natuurlijke Historie), Leiden, The Netherlands, was successfully determined to be haplotype JA1 of type A. JA1 is the most predominant haplotype mainly observed from central to southern part of Japan and would be the most accessible type to Von Siebold whose activity range was limited around Nagasaki.
Eel larvae apparently feed on marine snow, but many aspects of their feeding ecology remain unkno... more Eel larvae apparently feed on marine snow, but many aspects of their feeding ecology remain unknown. The eukaryotic 18S rRNA gene sequence compositions in the gut contents of four taxa of anguilliform eel larvae were compared with the sequence compositions of vertically sampled seawater particulate organic matter (POM) in the oligotrophic western North Pacific Ocean. Both gut contents and POM were mainly composed of dinoflagellates as well as other phytoplankton (cryptophytes and diatoms) and zooplankton (ciliophoran and copepod) sequences. Gut contents also contained cryptophyte and ciliophoran genera and a few other taxa. Dinoflagellates (family Gymnodiniaceae) may be an important food source and these phytoplankton were predominant in gut contents and POM as evidenced by DNA analysis and phytoplankton cell counting. The compositions of the gut contents were not specific to the species of eel larvae or the different sampling areas, and they were most similar to POM at the chloroph...
The widely distributed East Asian Japanese eel Anguilla japonica constitutes a single genetically... more The widely distributed East Asian Japanese eel Anguilla japonica constitutes a single genetically homogeneous population with a single spawning area near the West Mariana Ridge. Otolith 87 Sr/ 86 Sr ratios of adults (categorized as "river", "estuarine" or "sea" eels, according to their habitat use history determined from otolith Sr:Ca ratio analysis) collected from the spawning area in 2008 and 2009 were examined in an attempt to determine their juvenile growth areas. In addition, 87 Sr/ 86 Sr ratios of water samples from rivers in China, Taiwan, Korea, and Japan were determined. Otolith 87 Sr/ 86 Sr ratios of the "river", "estuarine" and "sea" eels were 0.707793, 0.708580-0.709944 and 0.709068, respectively, and water sample ratios from China, Korea, Taiwan, and Japan were 0.
Microsatellite loci were isolated from a size-selected genomic library of Pacific northern tuna T... more Microsatellite loci were isolated from a size-selected genomic library of Pacific northern tuna Thun nus thynnus orientalis, and PCR primer sets to amplify four loci were designed. Investigation on genet ic polymorphism at these loci in the Pacific northern bluefin tuna sample (n=35-40) revealed high degree of length polymorphisms in all loci, in which number of alleles per locus ranged from 8 to 23 and observed heterozygosity from 0.533 to 1. These primer sets were applied to Atlantic northern bluefin tuna T. t. thynnus, albacore T. alalunga, bigeye tuna T. obesus and yellowfin tuna T. albacares, detect ing polymorphism in all loci comparable with those of Pacific northern bluefin tuna. Significant differ ences in the allele frequency were observed between Pacific and Atlantic northern bluefin tuna samples. These primer sets developed for Pacific northern bluefin tuna appeared to be useful for amplifying homologous microsatellite loci in the other Thunnus tuna species, and may have great potential as indi cators for genetic variability within and between samples of tuna species of the genus Thunnus.
Relatively conserved exon sequences among distant aquatic animal taxa (Copepoda, Echinodermata, a... more Relatively conserved exon sequences among distant aquatic animal taxa (Copepoda, Echinodermata, and Teleostei) were determined for 12 ribosomal protein genes, and 19 primer pairs were designed for an exon-primed intron-crossing polymerase chain reaction strategy. The universal utility of these primers was evaluated in distant animal species (sea urchin, squid, crab, shark, and tuna). Fragment amplification was confirmed for at least three species for all primer pairs, and single fragment amplification was observed for at least one species in 16 primer pairs. Primer sets presented here may serve as an initial step for isolating singlecopy nuclear DNA sequences in a wide variety of marine animals.
Anguilliform leptocephali of the genus Thalassenchelys Castle and Raju 1975 are remarkably large ... more Anguilliform leptocephali of the genus Thalassenchelys Castle and Raju 1975 are remarkably large and peculiarly shaped eel larvae, whose adult form has been unknown since the discovery of the larvae in the 1950s. We found bigmouth conger Congriscusmegastomus (Günther 1877) collected off the Pacific coasts of Japan to have mitochondrial DNA sequences (16S rDNA and COI) nearly identical to those of Thalassenchelys coheni Castle and Raju 1975 published to date and collected recently in the north Pacific. Vertebrae counts of C.megastomus were consistent with the myomere counts of T. coheni. We conclude that T.coheni, so-called larval species described by Castle and Raju (1975), is a junior synonym of C.megastomus. Therefore, the family to which the leptocephali belong must be Congridae.
The lipid and fatty acid composition of the muscle of the wild Japanese freshwater eel, Anguilla ... more The lipid and fatty acid composition of the muscle of the wild Japanese freshwater eel, Anguilla japonica, was analyzed between the initial and terminal stages of spawning migration to clarify the relationship between lipid physiology and maturation. Triacylglycerols were the only major component in the initial-phase eels, which contained high levels of lipids, while comparatively low triacylglycerol levels were observed in terminal-phase eels (Mariana silvers) at spawning area. Significant levels of plasmalogens were found in its phosphatidylethanolamine, different from other common fish species, which have their little levels. The major fatty acids in A. japonica depot triacylglycerols were 14:0, 16:0, 18:0, 16:1n-7, 18:1n-7, 18:1n-9, and 18:2n-6. Noticeable levels of 20:4n-6, EPA, 22:5n-3, and DHA were also found in initial-phase sample TAG at the yellow and initial silver stages. High 18:2n-6 levels in all A. japonica lipids were similar to those in other common freshwater fishe...
Journal of Experimental Marine Biology and Ecology, 2013
Better understanding the diet of small marine predators such as the planktonic larvae of spiny lo... more Better understanding the diet of small marine predators such as the planktonic larvae of spiny lobsters is important for our awareness of interactions within marine assemblages and for species commercialisation. In DNA-based diet studies of small organisms there is a risk that any DNA contaminating the outside of an organism will be detected and falsely assumed to originate from the gut. Experiments with terrestrial predators have overcome the problem of exogenous contamination by treating the exterior of the predator with bleach (sodium hypochlorite). However, the use of bleach is a risky strategy when treating either a rare predator or aquatic predators, which are generally more permeable than terrestrial animals. Many plankton studies have not reported how they dealt with exogenous contamination, or do not use a control during PCR to detect false positives due to exogenous contamination. One approach is to wash the predator with MilliQ filtered water or ethanol and to use the final wash as a PCR template to detect residual DNA. In the present study we report that washing has variable success at removing exogenous contaminants and that using the final wash as a control for exogenous contamination consistently fails. Based on our results we recommend using DNA extracted from a swab of the exterior of the predator as a control for exogenous contamination. We also report on the benefit of using a novel syringe technique to obtain gut content that minimises contact with the predator surface, and therefore the risk of exogenous contamination.
<p>Based on eel descent and ascent timings in the morning and evening, sunrise and sunset t... more <p>Based on eel descent and ascent timings in the morning and evening, sunrise and sunset times were estimated and used for calculating latitude (A) and longitude (B) positions of ten wild eels. Actual eels’ position is shown by red triangle. Eel positions estimated by average and equation methods (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0121801#sec008" target="_blank">Results and Discussion</a>) are shown by yellow and black circles, respectively.</p
<p>The colors and contours indicate the water temperature. No temperature data was availabl... more <p>The colors and contours indicate the water temperature. No temperature data was available for gray area. See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0121801#pone.0121801.t001" target="_blank">Table 1</a> for individual information. Midnight (inverted closed triangle).</p
<p>A to F correspond to DST1 to 6 (see <a href="http://www.plosone.org/article/info... more <p>A to F correspond to DST1 to 6 (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0102376#pone-0102376-t001" target="_blank">Table 1</a>). Note conspicuous white spots on the median naked interambulacral areas, and light colored periproctal cone with orange or red ring.</p
Recent molecular analyses revealed Palaemon paucidens De Haan, 1844 to be species complex, since ... more Recent molecular analyses revealed Palaemon paucidens De Haan, 1844 to be species complex, since three genetically distinct types (designated by types A, B and C) were detected. A mitochondrial 16S rDNA sequence of the lectotype specimen collected by P. F. von Siebold nearly two centuries ago in Japan and held in Naturalis Biodiversity Center (formerly Rijksmuseum van Natuurlijke Historie), Leiden, The Netherlands, was successfully determined to be haplotype JA1 of type A. JA1 is the most predominant haplotype mainly observed from central to southern part of Japan and would be the most accessible type to Von Siebold whose activity range was limited around Nagasaki.
Eel larvae apparently feed on marine snow, but many aspects of their feeding ecology remain unkno... more Eel larvae apparently feed on marine snow, but many aspects of their feeding ecology remain unknown. The eukaryotic 18S rRNA gene sequence compositions in the gut contents of four taxa of anguilliform eel larvae were compared with the sequence compositions of vertically sampled seawater particulate organic matter (POM) in the oligotrophic western North Pacific Ocean. Both gut contents and POM were mainly composed of dinoflagellates as well as other phytoplankton (cryptophytes and diatoms) and zooplankton (ciliophoran and copepod) sequences. Gut contents also contained cryptophyte and ciliophoran genera and a few other taxa. Dinoflagellates (family Gymnodiniaceae) may be an important food source and these phytoplankton were predominant in gut contents and POM as evidenced by DNA analysis and phytoplankton cell counting. The compositions of the gut contents were not specific to the species of eel larvae or the different sampling areas, and they were most similar to POM at the chloroph...
The widely distributed East Asian Japanese eel Anguilla japonica constitutes a single genetically... more The widely distributed East Asian Japanese eel Anguilla japonica constitutes a single genetically homogeneous population with a single spawning area near the West Mariana Ridge. Otolith 87 Sr/ 86 Sr ratios of adults (categorized as "river", "estuarine" or "sea" eels, according to their habitat use history determined from otolith Sr:Ca ratio analysis) collected from the spawning area in 2008 and 2009 were examined in an attempt to determine their juvenile growth areas. In addition, 87 Sr/ 86 Sr ratios of water samples from rivers in China, Taiwan, Korea, and Japan were determined. Otolith 87 Sr/ 86 Sr ratios of the "river", "estuarine" and "sea" eels were 0.707793, 0.708580-0.709944 and 0.709068, respectively, and water sample ratios from China, Korea, Taiwan, and Japan were 0.
Microsatellite loci were isolated from a size-selected genomic library of Pacific northern tuna T... more Microsatellite loci were isolated from a size-selected genomic library of Pacific northern tuna Thun nus thynnus orientalis, and PCR primer sets to amplify four loci were designed. Investigation on genet ic polymorphism at these loci in the Pacific northern bluefin tuna sample (n=35-40) revealed high degree of length polymorphisms in all loci, in which number of alleles per locus ranged from 8 to 23 and observed heterozygosity from 0.533 to 1. These primer sets were applied to Atlantic northern bluefin tuna T. t. thynnus, albacore T. alalunga, bigeye tuna T. obesus and yellowfin tuna T. albacares, detect ing polymorphism in all loci comparable with those of Pacific northern bluefin tuna. Significant differ ences in the allele frequency were observed between Pacific and Atlantic northern bluefin tuna samples. These primer sets developed for Pacific northern bluefin tuna appeared to be useful for amplifying homologous microsatellite loci in the other Thunnus tuna species, and may have great potential as indi cators for genetic variability within and between samples of tuna species of the genus Thunnus.
Relatively conserved exon sequences among distant aquatic animal taxa (Copepoda, Echinodermata, a... more Relatively conserved exon sequences among distant aquatic animal taxa (Copepoda, Echinodermata, and Teleostei) were determined for 12 ribosomal protein genes, and 19 primer pairs were designed for an exon-primed intron-crossing polymerase chain reaction strategy. The universal utility of these primers was evaluated in distant animal species (sea urchin, squid, crab, shark, and tuna). Fragment amplification was confirmed for at least three species for all primer pairs, and single fragment amplification was observed for at least one species in 16 primer pairs. Primer sets presented here may serve as an initial step for isolating singlecopy nuclear DNA sequences in a wide variety of marine animals.
Anguilliform leptocephali of the genus Thalassenchelys Castle and Raju 1975 are remarkably large ... more Anguilliform leptocephali of the genus Thalassenchelys Castle and Raju 1975 are remarkably large and peculiarly shaped eel larvae, whose adult form has been unknown since the discovery of the larvae in the 1950s. We found bigmouth conger Congriscusmegastomus (Günther 1877) collected off the Pacific coasts of Japan to have mitochondrial DNA sequences (16S rDNA and COI) nearly identical to those of Thalassenchelys coheni Castle and Raju 1975 published to date and collected recently in the north Pacific. Vertebrae counts of C.megastomus were consistent with the myomere counts of T. coheni. We conclude that T.coheni, so-called larval species described by Castle and Raju (1975), is a junior synonym of C.megastomus. Therefore, the family to which the leptocephali belong must be Congridae.
The lipid and fatty acid composition of the muscle of the wild Japanese freshwater eel, Anguilla ... more The lipid and fatty acid composition of the muscle of the wild Japanese freshwater eel, Anguilla japonica, was analyzed between the initial and terminal stages of spawning migration to clarify the relationship between lipid physiology and maturation. Triacylglycerols were the only major component in the initial-phase eels, which contained high levels of lipids, while comparatively low triacylglycerol levels were observed in terminal-phase eels (Mariana silvers) at spawning area. Significant levels of plasmalogens were found in its phosphatidylethanolamine, different from other common fish species, which have their little levels. The major fatty acids in A. japonica depot triacylglycerols were 14:0, 16:0, 18:0, 16:1n-7, 18:1n-7, 18:1n-9, and 18:2n-6. Noticeable levels of 20:4n-6, EPA, 22:5n-3, and DHA were also found in initial-phase sample TAG at the yellow and initial silver stages. High 18:2n-6 levels in all A. japonica lipids were similar to those in other common freshwater fishe...
Journal of Experimental Marine Biology and Ecology, 2013
Better understanding the diet of small marine predators such as the planktonic larvae of spiny lo... more Better understanding the diet of small marine predators such as the planktonic larvae of spiny lobsters is important for our awareness of interactions within marine assemblages and for species commercialisation. In DNA-based diet studies of small organisms there is a risk that any DNA contaminating the outside of an organism will be detected and falsely assumed to originate from the gut. Experiments with terrestrial predators have overcome the problem of exogenous contamination by treating the exterior of the predator with bleach (sodium hypochlorite). However, the use of bleach is a risky strategy when treating either a rare predator or aquatic predators, which are generally more permeable than terrestrial animals. Many plankton studies have not reported how they dealt with exogenous contamination, or do not use a control during PCR to detect false positives due to exogenous contamination. One approach is to wash the predator with MilliQ filtered water or ethanol and to use the final wash as a PCR template to detect residual DNA. In the present study we report that washing has variable success at removing exogenous contaminants and that using the final wash as a control for exogenous contamination consistently fails. Based on our results we recommend using DNA extracted from a swab of the exterior of the predator as a control for exogenous contamination. We also report on the benefit of using a novel syringe technique to obtain gut content that minimises contact with the predator surface, and therefore the risk of exogenous contamination.
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