Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER FISHERIES SOC  

Sicyopterus japonicus is unique because it is the only temperate amphidromous goby of the subfamily Sicydiinae. Life history and migration characteristics of S. japonicus, including seasonal changes of condition factor, spawning season, hatching size, oceanic larval duration, recruitment season, and size at recruitment, were examined in the temperate region of western Japan and were compared with those of other Sicydiinae species, all of which inhabit the tropics and subtropics. The condition factor varied seasonally, with peaks in July and November. The spawning season of S. japonicus ranged front July to September, with a peak in July-August, and was shorter than that of other species that normally spawn from 7 to 12 months/year. The hatching size (1.5 mm total length) was similar to other Sicydiinae, but oceanic larval duration (range: 173-253 d) was longer than most other species. The long larval duration and single annual reproduction period Suggest that it is adapted to long-distance oceanic dispersal. The recruitment season (about 4 months) is the shortest known among the Sicydiinae, but its size at river entry (mean: 26.3 mm standard length) was similar to other species. The shorter reproductive and recruitment seasons for S. japonicus probably indicate that its migration strategy is determined by seasonal changes in the temperate region. Sicydiinae species have larger Clutch sizes and smaller hatching sizes compared to other temperate amphidromous families such as the Galaxiidae, Osmeridae, and Cottidae. Sicydiinae species have no nondiadromous forms, suggesting that they may have a migration strategy with a high oceanic dependency that facilitates oceanic dispersion.

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.26028/cybium/2023-019

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Company of Biologists  

Colonisation of freshwater habitats by marine animals is a remarkable evolutionary event that has enriched biodiversity in freshwater ecosystems. The acquisition of the tolerance to hypotonic stress during the early life stages is presumed to be essential for their successful freshwater colonisation, but very little empirical evidence has been obtained to support this idea. This study aimed to comprehend the evolutionary changes of osmoregulatory mechanisms that enhance the larval freshwater tolerance in amphidromous fishes, which typically spend their larval period in marine (ancestral) habitats and the rest of life history stages in freshwater (derived) habitats. We compared the life history patterns and changes in larval survivorship and gene expression depending on salinity among three congeneric marine-originated amphidromous goby species (Gymnogobius), which had been suggested to differ in their larval dependence on freshwater habitats. An otolith microchemical analysis and laboratory-rearing experiment confirmed the presence of freshwater residents only in G. urotaenia and higher larval survivorship of this species in the freshwater condition than the obligate amphidromous G. petschiliensis and G. opperiens. Larval whole-body transcriptome analysis revealed that G. urotaenia from both amphidromous and freshwater-resident populations exhibited the greatest differences in expression levels of several osmoregulatory genes, including aqp3, which is critical for water discharge from their body during early fish development. The present results consistently support the importance of enhanced freshwater tolerance and osmoregulatory plasticity in larval fish to establish freshwater forms, and further identified key candidate genes for larval freshwater adaptation and colonisation in the goby group.

DOI： 10.1242/jeb.246110

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Publishing type：Research paper (scientific journal)   Publisher：Authorea, Inc.  

<p id="p1">Colonisation of freshwater habitats by marine animals is a remarkableevolutionary event that has enriched biodiversity in freshwaterecosystems. For successful freshwater colonisation, high physiologicalplasticity is presumed to be necessary, but its evolutionary basis hasnot been detailed. Marine-originated amphidromous species, whichregularly migrate between freshwater and marine environments, haverepeatedly lost migratory behaviour in many lineages, which sometimestriggered species radiation in freshwater habitats. Since amphidromousspecies typically visit the sea during the larval period, the difficultyin the evolution of larval freshwater tolerance is a bottleneck forfreshwater colonisation. To elucidate the key evolutionary changes thatenhance the physiological plasticity for freshwater colonisation, wecompared larval gene expression changes depending on salinity conditionsamong three congeneric amphidromous goby species (Gymnogobius) withvarying dependences on freshwater habitats. First, an otolithmicrochemical analysis and rearing experiment under laboratoryconditions confirmed the presence of freshwater residents only in G.urotaenia and higher larval survivorship of this species both inseawater and freshwater conditions than the obligate amphidromous G.petschiliensis and G. opperiens. Larval whole-body transcriptomeanalysis revealed that G. urotaenia exhibited the greatest differencesin the expression levels of several osmoregulatory genes, includingaqp3, which is critical for water discharge from their body during earlyfish development. Thus, we obtained the results that consistentlysupport the importance of enhanced osmoregulatory plasticity forestablishing freshwater forms, and further identified some importantevolutionary changes for larval freshwater adaptation and colonisationin the goby group.</p>

DOI： 10.22541/au.165777854.44197862/v1

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Language：English  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Cambridge University Press (CUP)  

<title>Abstract</title>The silver pomfret (<italic>Pampus argenteus</italic>) is one of the most commercially important marine fish species in the Bay of Bengal, Indian Ocean. However, detailed information on the reproductive biology of silver pomfret is limited for the Bay of Bengal, Bangladesh. To understand their reproductive biology, especially the gonadal developmental cycle and spawning season, a total of 373 individuals were collected monthly from February 2016 to January 2018 and examined. The total length (TL) and weight (TW) of <italic>P. argenteus</italic> ranged from 18.82–35.73 cm and 89.26–617.60 g, respectively. The highest gonadosomatic index (GSI) values were observed from April–June with a second (smaller) peak in October. The highest oocyte diameter was observed in May (630.50 ± 96.70 μm), when the fish reached full maturity, and the lowest was observed in July (35.10 ± 7.12 μm), when new eggs began their development for the next spawning season. The maximum number of eggs in the ovary were found in the yolk granule stage in May with a number of post-ovulatory follicles, which indicated that the ovaries developed to a peak leading up to the spawning season. A number of spermatids were also seen in males in April–June along with females. From these detailed observations, it may be concluded that <italic>P. argenteus</italic> shows two spawning peaks, in May–June and October. This observation will be helpful for the artificial breeding, sustainable management and conservation of this species in the study area.

DOI： 10.1017/s0025315420000922

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1017/S0025315417002053

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY  

Mochizuki and Fukui (Jpn J Ichthyol 30 () 27-36) studied the development and replacement of the upper jaw teeth in a Japanese fish species, Sicyopterus japonicus (Gobioidei: Sicydiinae), and they reported that worn-out functional teeth in the upper jaw were not shed outside the skin but were taken into the soft tissue of the upper jaw and completely resorbed there. To date, however, this phenomenon appears poorly documented. Furthermore, the mechanism for the resorption of these teeth remains to be determined. In this study, we examined this phenomenon by using 3D microcomputed tomography (m-CT), scanning electron microscopy (SEM), and various techniques of light (LM) and electron (EM) microcopy. This study demonstrated that the upper jaw dentition of this fish was more or less simultaneously replaced with the replacement occurring during short time periods and that the lingual movement of the replacement teeth to the functional tooth position advanced simultaneously in a given row. Furthermore, our study also revealed that many worn-out functional teeth were engulfed by the oral epithelium, invaginated into the lingual shallow ditch of the premaxilla, and were resorbed/degraded completely by numerous foreign body giant cells rather than by odontoclasts during periods of at least three intervals of tooth replacement. The complete resorption/degradation of worn-out functional teeth in the soft tissue of the upper jaw suggests the possibility of the reuse of their components (minerals such as Ca and P, including Fe) for rapid and successional production of new replacement teeth in the upper jaw of adult S. japonicus. Anat Rec, 2017. (c) 2017 Wiley Periodicals, Inc. Anat Rec, 301:111-124, 2018. (c) 2017 Wiley Periodicals, Inc.

DOI： 10.1002/ar.23685

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

The ayu (Plecoglossus altivelis) is an annual, amphidromous, plecoglossid fish, distributed in Vietnam, China, Taiwan, Korea, and Japan. To date, ayu have been found only in two rivers in northern Vietnam, where little is known about their life history. The Tien Yen River is believed to be the most southwestern habitat for this species. To determine whether newly hatched ayu larvae drift and to understand their downstream migration, intensive surveys were conducted in the Tien Yen River from October to March of 2013-2016. In total, 529 drifting ayu larvae were collected from four of six sampling stations along the river. Thus, ayu reproduction has been confirmed in this river for the first time, where only adult fish had been found previously. However, we did not successfully collect larvae in the eastern branch of the river, which has a hydroelectric dam, suggesting that ayu do not inhabit this branch or else do not reproduce there. The presence of drifting larvae in the western branch from mid-December to late January implies that they spawn from late November to mid-January. Drifting larvae were captured primarily at night, but peak occurrences varied depending upon the day and the sampling station. With the range of body sizes and variable diel abundance patterns, ayu in the Tien Yen River probably employ multiple spawning grounds. This study provides fundamental life history data for the vulnerable ayu populations in northern Vietnam.

DOI： 10.1007/s10641-017-0646-6

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：SOC FRANCAISE D ICHTYOLOGIE  

Recruitment from the sea to freshwater is a turning point in the life history of amphidromous fish. The amphidromous gobioid subfamily Sicydiinae is distributed widely in Indo-Pacific regions. To understand their ecology at recruitment, which is poorly known for this subfamily, underwater observations of recruiting post-larvae of Sicyopterus japonicus were conducted and their swimming depth was measured in the estuary of the Ota River of Wakayama, Japan. During 16 observation periods from April to July in 2006,2007 and 2008, newly recruiting post-larvae were observed swimming in shoals in the middle layer of the lower half of the water column near the river banks in the upper area of study site and in the upper half of the water column near the river mouth. Although the estuary appears to be a temporary transit area for newly recruiting post-larvae, it may be an important place for them to adapt to their later benthic herbivorous life in freshwater.

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Language：Japanese   Publisher：生物研究社  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Objective: The present study was aimed at elucidating the time and order of eruption of first functional teeth in the upper jaw of post-larval life of Sicyopterus japonicus (S. japonicus) during cranial metamorphosis at the time of river recruitment.
Design: Fishes were caught at the post-larval stage at a river mouth and maintained for 7 days in a water tank. Each of 10 specimens was evaluated every day for 7 days by using microcomputed tomography, scanning electron microscopy, and light microscopy with peculiar attention to the development of the upper jaw teeth.
Results: Fishes caught at the river mouth were mostly transparent, with a rostral terminal mouth, and no teeth could be found in either the upper or lower jaw. At 2 days after collection, the mouth position changed from terminal to subterminal, resulting from a change in head shape. The initial eruption of first functional teeth was detected at the anterior two-thirds region of each upper jaw. These teeth erupted in adjacent positions, most had a tricuspid crown, and they represented miniature versions of adult teeth. At 5 days, the position of the mouth became further relocated from terminal rostral to ventral. The number of erupted teeth increased, followed by spreading of them anteriorly and posteriorly. At 7 days, they formed a single row of close-set tricuspid teeth along the entire length of each upper jaw.
Conclusions: The present study demonstrated that even under laboratory conditions a rapid and drastic cranial metamorphosis took place within a week after the time of collection of post-larval S. japonicus from a river. The eruption of first functional teeth in the upper jaw of S. japonicus, which teeth are adapted to scraping algae off the substrate, was initially detected at 2 days after collection, and first functional dentition of the upper jaw was set up within 7 days after it. (C) 2016 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.archoralbio.2016.02.005

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© 2014, The Ichthyological Society of Japan. The distribution of fluvial fish was surveyed at 55 sites on Yakushima Island, Japan, which has precipitous mountains and waterfalls (below- or no-waterfall sites: 31; above-waterfall sites: 24). Eleven diadromous and one river resident (introduced Oncorhynchus masou masou) species were found, but absolutely no fish were detected at the 18 above-waterfall sites. Statistical analyses revealed that the presence of waterfalls (> 5 m in height) below the sites had a significant negative effect on fish distribution, suggesting that waterfalls prevent migration of diadromous fishes. We found Rhinogobius brunneus populations above high waterfalls such as Nunobiki Falls (50 m) and Ohko Falls (88 m). Otolith Sr:Ca ratios and mitochondrial DNA (cyt-b region) were examined to determine the migratory history and genetic properties of these populations; the Sr:Ca ratios indicated that the populations had a landlocked life cycle, whereas the genetic endemism/isolation of landlocked populations was unexpectedly absent. There is no clear explanation for this phenomenon, but fairly infrequent individuals of nonlandlocked type might have migrated beyond the waterfalls with their sucker-like organ and mated with landlocked populations, disrupting the genetic isolation of landlocked populations.

DOI： 10.1007/s10228-014-0400-4

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Language：English   Publisher：SPRINGER  

Amphidromy is a distinctive form of diadromy, but differences in the life histories of tropical and temperate amphidromous fishes suggest that there are two types of freshwater amphidromy. The life histories of Sicydiinae gobies, ayu (Plecoglossus altivelis), Japanese sculpins (Cottus) and galaxiids (Galaxiidae), suggest that the Sicydiinae are representatives of tropical freshwater amphidromy, whereas ayu, sculpins and galaxiids are representatives of temperate freshwater amphidromy. The Sicydiine larval stage may be required to occur in the ocean for all species, but ayu, sculpins and galaxiids have landlocked or fluvial forms with larvae that do not need to enter the ocean for larval feeding and growth. This suggests that Sicydiine larvae have a high oceanic dependency whereas ayu, sculpins and galaxiid larvae have a low oceanic dependency. Freshwater amphidromous fish in tropical and temperate zones appear to have developed two different strategies in the evolution of their life histories. It is likely that the evolutionary direction of the larval stage of tropical amphidromy is to remain in the sea and that of temperate amphidromy is towards having the ability to remain in freshwater if needed. Tropical and temperate amphidromy appear to be biologically informative categories and evaluations of this hypothesis will facilitate better understanding of the various forms of amphidromy in the future.

DOI： 10.1007/s11160-013-9316-8

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CSIRO PUBLISHING  

Even if amphidromous fish species contribute most to the diversity of fish communities in the tropical insular rivers, their biological cycle remain poorly known. For the first time, the otolith elemental composition and microstructure of two ancestral gobioids, Rhyacichthys guilberti and Protogobius attiti, were investigated to describe their biological cycle and pelagic larval duration (PLD). The otolith analysis using a femtosecond laser ablation coupled to an inductively coupled plasma-mass spectrometer (fs-LA-ICP-MS) revealed an amphidromous life history for R. guilberti and it suggested a progressive habitat shift from a marine habitat to a freshwater environment for P. attiti. For the first time, an endemic species, P. attiti, showed longer and more variable PLD (55.2 +/- 13.5 days) than did a widespread one (R. guilberti: similar to 30 days). These results need to be confirmed by analysing more samples but suggest that factors other than the PLD control endemism and dispersal processes. In association with this first description of the biological cycle for both species, such an approach is a prerequisite for the management and conservation of both patrimonial species.

DOI： 10.1071/MF13146

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

Sicyopterus japonicus (Teleostei, Gobiidae), a hill-stream herbivorous gobiid fish, possesses an unusual oral dentition among teleost fishes on account of its feeding habitat. By using scanning electron microscopy, light microscopy, and transmission electron microscopy, including vital staining with tetracycline, we examined the development of the attachment tissues of the upper jaw teeth in this fish. The functional teeth of S. japonicus had an asymmetrical dentine shaft. The dentine shaft attached to the underlying uniquely shaped pedicel by means of two different attachment mechanisms. At the lingual base, collagen fiber bundles connected the dentine shaft with the pedicel (hinged attachment), whereas the labial base articulated with an oval-shaped projection of the pedicel (articulate attachment). The pedicel bases were firmly ankylosed to the crest of the thin flange of porous spongy bone on the premaxillary bone, which afforded a flange-groove system on the labial surface of the premaxillary bone. Developmentally, the pedicel and thin flange of spongy bone were completely different mineralized attachment tissues. The pedicel had a dual origin, i.e., the dental papilla cells, which differentiated into odontoblasts that constructed the internal surface of the pedicel, and the mesenchymal cells, which differentiated into osteoblasts that formed the outer face of the pedicel. A thin flange of spongy bone was deposited on the superficial resorbed labial side of the premaxillary bone proper, and later rapid bone remodeling proceeded toward the pedicel base. These unique features of pedicellate tooth attachment for the upper jaw teeth in the adult S. japonicus are highly modified teeth for enhancing the ability of individual functional teeth to move closely over irregularities in the rock surfaces during the scraping of algae. J. Morphol., 2013. (c) 2012 Wiley Periodicals, Inc.

DOI： 10.1002/jmor.20111

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SOC FRANCAISE D ICHTYOLOGIE  

The oceanic early life of Sicydiinae gobies has remained mysterious although considerable knowledge has been accumulated about their freshwater life. Two marine post-larvae of Sicyopterus japonicus. were collected by otter trawl in the ocean off Shikoku. Japan on 18 July and 22 August 2007. These specimens were identified as S. japonicus using meristic characters and the 16S ribosomal RNA mitochondrial gene, which were compared to S. japonicus adults and two other species of Sicydiinae gobies. Morphological observations documented that S. japonicus post-larval characters were the presence of a red pigment at the bases of the second dorsal and caudal fins in fresh samples, as well as the presence of melanophores on the upper jaw, caudal fin base and the lateral body posterior to the anal fin base. Otolith analysis showed that their post-larval durations were 278 and 286 days, and their birth dates were 13 October and 9 November 2006. It is likely that these two post-larvae may have been transported by the Kuroshio Current from the southern part of their geographic species range such as from Okinawa or Taiwan and may have had recruited to a river around Kochi.

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：SOC FRANCAISE D ICHTYOLOGIE  

To understand the reproductive biology of the amphidromous goby, Sicyopterus japonicus, juvenile and adult gobies of this species were sampled in the Ota River, Wakayama, Japan. Sampling was conducted monthly from June 2003 to October 2004, and once each season from April 2005 to March 2006 at 7 sampling stations from the estuary to the upper reaches of the river. The gonadosomatic index values of females (N = 171) ranged from 0.0 to 20.8 and showed high values in July and August (summer, mean: 6.5) that indicated they have a short spawning season. There were no relationships between gonadosomatic index and standard length, age, or distance from the river mouth. This indicated that they do not have a spawning aggregation in a certain area in the river. 30 randomly selected oocytes from each ovary of 48 females were measured to observe the monthly changes of oocyte diameters. "Small oocytes" of 5-100 mu m diameters were observed all year round, while "large oocytes" &gt; 200 mu m were only observed in July and August. Only specimens collected in July and August were classified as being mature by histological examination. Potential batch fecundities calculated by the percentage of large oocytes in the gonads were estimated to be 10,800-52,500 (N = 10), and standard length was correlated with potential batch fecundity. Egg clutches of S. japonicus were observed throughout the sampling sites except in the upper-and lower-most reaches in August 2004 to 2008. Spawning places were found in rapids and egg clutches were attached to the undersides of stones. Although S. japonicus in the Ota River had similar characteristics with tropical Sicychinae species, such as large clutches deposited on the undersurface of the stones, their spawning season was shorter than that of tropical species that have almost year-round spawning.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Sicyopterus japonicus (Teleostei, Gobiidae) possesses a unique upper jaw dentition different from that known for any other teleosts. In the adults, many (up to 30) replacement teeth, from initiation to attachment, are arranged orderly in a semicircular-like strand within a capsule of connective tissue on the labial side of each premaxillary bone. We have applied histological, ultrastructural, and three-dimensional imaging from serial sections to obtain insights into the distribution and morphological features of the dental lamina in the upper jaw dentition of adult S. japonicus. The adult fish has numerous permanent dental laminae, each of which is an infolding of the oral epithelium at the labial side of the functional tooth and forms a thin plate-like structure with a wavy contour. All replacement teeth of a semicircular-like strand are connected to the plate-like dental lamina by the outer dental epithelium and form a tooth family; neighboring tooth families are completely separated from each other. The new tooth germ directly buds off from the ventro-labial margin of the dental lamina, whereas no distinct free end of the dental lamina is present, even adjacent to this region. Cell proliferation concentrated at the ventro-labial margin of the dental lamina suggests that this region is the site for repeated tooth initiation. During tooth development, the replacement tooth migrates along a semicircular-like strand and eventually erupts through the dental lamina into the oral epithelium at the labial side of the functional tooth. This unique thin plate-like permanent dental lamina and the semicircular-like strand of replacement teeth in the upper jaw dentition of adult S. japonicus probably evolved as a dental adaptation related to the rapid replacement of teeth dictated by the specialized feeding habit of this algae-scraping fish.

DOI： 10.1007/s00441-010-0935-2

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：International Coastal Research Center, Atmosphere and Ocean Research Institute, the University of Tokyo  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：International Coastal Research Center, Atmosphere and Ocean Research Institute, the University of Tokyo  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SOC FRANCAISE D ICHTYOLOGIE  

Sicyopterus lagocephalus is an amphidromous fish: adults live in rivers, but after hatching larvae are carried to the sea (dispersion stage). After a certain time spent at sea, post-larvae return to rivers to grow and reproduce. Sicyopterus lagocephalus post-larvae recruiting to Reunion Island rivers (Mascarene Archipelago), provide an important food source to local populations and this fishing activity has a significant socio-economic impact. A better understanding of the early life traits of this species and the characterisation of larval stages should improve the biological and physiological knowledge needed to understand the processes involved in the dispersion stage and help managers to implement conservation measures. In Reunion Island, we characterised the development of larvae from hatching to migration to the sea. The results show that larvae do not undergo any development in freshwater, and that it is the arrival at sea that triggers the morphological transformations. Our results have also revealed that development is quicker when the temperature is high and that development varies according to water depth during the downstream migration. In natural temperature conditions, the maximum survival rate in freshwater is four days. This suggests that when the downstream migration takes too long because of anthropogenic or hydraulic factors, the free embryos would die before they reach the sea.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japanese Association for Oral Biology  

Using micro-computed tomography (micro-CT), scanning electron microscopy, contact microradiography, and light microscopy, we investigated the morphological characteristics of the upper dentition of the gobiid fish Sicyopterus japonicus. Three-dimensional (3-D) micro-CT reconstruction demonstrated many close-set densely packed rows of replacement teeth within the dental sac behind a row of functional teeth located on the labial margin of the premaxillae. Cross-slices of the 3-D micro-CT image revealed that functional teeth and numerous replacement teeth were arranged in a semicircular-like strand. In ground as well as histological cross-sections made in a similar plane as seen in the micro-CT image, each tooth family consisted of about 35 replacement teeth in the fish, ranging in standard length (SL) from 50.8 to 60.5 mm, and a tooth germ was initiated at the most disto-labial end of a tooth family, with the functional tooth situated at the opposite end. Between them, many replacement teeth were arranged in orderly fashion, with each replacement tooth being a little less developed than its proximal neighbor.The present study demonstrates that in the upper jaw dentition of adult S. japonicus, consecutive development of replacement teeth in a tooth family can be monitored simultaneously in the same section by appropriate histological sectioning. These results suggest that the upper jaw dentition of this fish provides a suitable as well as unique system for the study of consecutive development of replacement teeth in adult fish.

DOI： 10.2330/joralbiosci.51.81

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Language：Japanese   Publisher：南紀生物同好会  

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Ecological aspects of recruitment in the amphidromous goby, Sicyopterus japonicus, were studied from larval collections made with a set net in the estuary of the Ota River, Wakayama, Japan. The abundance patterns of the 12,766 larvae collected from 18 April to 26 August 2006 showed several peaks during the recruitment season. Their body sizes at recruitment ranged from 23.5 to 30.0 mm standard length (mean +/- SD, 26.3 +/- 1.1 mm), 0.11 to 0.49 g body weight (0.22 +/- 0.05 g), and 8 to 20 condition factor (11 +/- 2). The standard length of the goby larvae tended to decrease with the season, while their body weight slightly increased and resulted in an increase in condition factor. The recruitment of larvae occurred mainly during the daytime. Otolith growth increment analysis of 30 larvae collected by a square lift net on 30 April 2005 revealed that the oceanic larval duration after downstream migration ranged from 173 to 253 days (208 +/- 22) after hatching. A limited time of recruitment in early summer and a considerably long duration of oceanic life (about a half year) appeared to be unique characteristics of this Sicyopterus species that lives in a temperate region in comparison to other tropical species of the genus Sicyopterus that all have year-round recruitment.

DOI： 10.1007/s10641-008-9345-7

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Language：Japanese   Publisher：南紀生物同好会  

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Language：Japanese   Publisher：南紀生物同好会  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The University of Tokyo  

To examine the genetic diversity of Sicyopterus japonicus, 448 sites of the control region of the mitochondrial DNA were analyzed in 77 specimens from the four localities of Okinawa, Kochi, Wakayama, and Shizuoka in Japan. A total of 74 haplotypes were found in the individuals examined. The same haplotypes occurred in Okinawa and Kochi, Kochi and Wakayama, and two specimens in Wakayama. The average sequence in genetic characteristics within localities varied from 1.7% in Kochi, 1.6% in Wakayama to 1.4% in Okinawa. There was no significant difference in genetic characteristics among the three locations of Wakayama, Kochi, and Okinawa (10,000 times permutation test, P>0.05). The number of specimens from Shizuoka was too small to compare to the other three locations. The neighbor-joining tree of the mitochondrial DNA haplotypes for all specimens constructed from the Kimura's two-parameter distances suggested no evidence of genetic subdivision of S. japonicus. These results suggested that this species has a single panmictic population and their larvae probably have a high dispersal ability during their oceanic stage.

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