• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2001.05a
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• pp.605-607
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• 2001

서해비단고둥(Umbonium (Suchinm) thomasi Crosse, 1863)은 비단고둥(U. (S.) costatum), 큰비단고둥(U. (S.) giganteum), 흑비단고둥(U. (S.) thomasi) 등과 함께 모래둥아과(Umboninae)에 속하는 종으로서, 우리나라 서해안에 다산하고 있으며, 최근 들어 그 수가 증가하고 있는 우점종의 하나로 표생저서동물(epifauna)로 침전물 및 현탁물식자(deposit and suspension feeder)이다(Fretter, 1975). (중략)

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2002.10a
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• pp.247-248
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• 2002

원시복족목 (Archaeogastropoda) 밤고둥과 (Trochidae)에 속하는 서해비단고둥(Umbonium thomasi)은 우리나라의 서해안과 중국연안에만 서식한다. 비단고둥 (U. costatum)보다 소형으로 낮은 원추형이고, 조간대의 모래사장에 살며 간조 때에는 모래 속으로 파고 들어간다. 껍질은 약간 푸르스름하고 꾸불꾸불한 회색 무되가 방사상으로 덮여 있으며 내부는 진주층으로 광택이 있다 (Yoo, 1976; Kwon et al., 1993). (중략)

• Proceedings of the Malacological Society of Korea Conference
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• 2000.11a
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• pp.47-48
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• 2000

• Proceedings of the Malacological Society of Korea Conference
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• 2000.11a
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• pp.49-51
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• 2000

• Korean Journal of Fisheries and Aquatic Sciences
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• v.35 no.6
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• pp.702-708
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• 2002

Although Umboniunm thomasi is one of marine mollusc (Archaeogastropoda: Trochidae) inhabiting the sands in the intertidal zone of the west coast of Korea, aspects of its reproductive biology are still not too well known. Reproductive cycle, gametogenesis, and first sexual maturity of U. thomasi collected at the west coast of Buan-gun, Jeollabuk-do, Korea were investigated monthly from January to December 1999. U. thomasi was dioecious, and an oviparous. The gonad was placed in the rear of the flesh part in the spiral shell. The external colors of the ripe ovary and testis appeared to be green and milk-white or yellowish white, respectively. Meat weigh rate peaked in July ($37.5\%$). And then the value sharply decreased in September ($28.3\%$), thereafter, gradually increased in November ($31.7\%$). Fully ripe oocytes were approximately 100$\~$110 $/mu$m in diameter, and their cytoplasm contained a great number of yolk Branules. Based on the monthly changes of the Bonadal development, gametogenesis, and meat weight rate, the reproductive cycle of U. thomasi could be devided into five successive stages: early active (November to April), late active (February to May), ripe (April to August), spawning (July to October), and recovery (September to February). Gonadal development and spawning were closely related to the seawater temperature, the main spawning occurred in September when the temperature reached above 24.2$^{\circ}C$. Individuals of 4.4 mm and less in shell height could not take part in reproduction in both sexes. Percentages of first sexual maturity of female and male shells ranging from 5.5 to 6.4 mm were $55.0\%$ and $61.9\%$, respectively, and $100\%$ of those over 7.5 mm in shell heights in both sexes participated in the reproduction.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.37 no.4
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• pp.295-306
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• 2004

Spatial patterns in the macrobenthic community structure in the inter- and subtidal zones in front of the Iwon Dike and environmental variables were examined in August 2001, In total, 156 macrobenthic species(123 intertidal species and 90 subtidal species) were recorded during this study, predominately polychaetes $(40{\%})$, bivalves $(22{\%})$, and crustaceans $(22{\%})$. Polychaetes made up less than $40{\%}$ of the intertidal communitr, but more than $50{\%}$ of the subtidal community. The mean density during this study was $1,456ind./m^{2}.$ Multivariate analysis (multidimensional scaling) revealed significant differences in community structure among four regions: near the Iwon dike (B1), the high and middle intertidal zone (B2), low intertidal zone (Al), and subtidal zone (A2). The number of species, total density, and diversity (H') varied significantly among the four regions. The distribution of macrobenthic community was affected by environmental variables, such as ${\%}$ silt/clay content, total sulfide, lose of ignition, and chemical oxygen demand. These environmental variables were negatively correlated with the dominant species (Nephtys polybranchia, Umbonium thomasi, and Scoloplos armiger) in the intertidal area, but positively correlated with the dominant species (Lumbrineris cruzensis, Notomastus latericeus, and Moerella sp.) in the subtidal area. Environmental variables $({\%}\;silt/clay content and total sulfide)$ were positively correlated with the dominant species (Heteromastus filiformis) in region Bl, but negatively correlated with the dominant species (Umbonium thomasi and Scoloplos koreanus) in region B2. Amphipods Urothoe spp. and Monoculodes koreanus were the dominant species in region Al. Umbonium thomasi, the dominant species in region B2, was not found in regions Bl or Al. We suggest that the inter-specific competition for territory and exposure to seawater may be important factors controlling the macrobenthic community structure in the inter- and subtidal zones in front of the Iwon Dike.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.36 no.6
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• pp.708-715
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• 2003

Species composition and distribution patterns of shellfish were investigated in Eoeun and Geojeon tidal flat located in the Saemangeum area on the west coast of Korea from May to October 2000. Nineteen species of shellfish were collected in Geojeon tidal flat. The samples in number of individuals included Umbonium thomasi $(90.0\%)$ and Mactra veneriformis $(5.0\%).$ In Eoeun tidal flat, ten species of shellfish were collected and the dominant species in number of individuals were Potamocorbula amurensis $(55.0\%)$ and U. thomasi $(18.6\%).$ These results were compared with previous studies conducted before the beginning of reclamation in Saemangeum. Compared with the results from 1988, a change In species composition was observed. Laternula flexuosa and Nuttallia olivacea appeared, while Mactra chinensis and Coelomactra antiquata disappeared in the deposition area in Geojeon tidal flat. In the erosion area of Eoeun tidal flat, M. veneriformis and Meretrix lusoria appeared, while Cyclina sinensis disappeared. Based on a cluster analysis, the shellfish community in Eoeun tidal flat was classified into three station groups based on sediment types. Geojeon tidal flat was also classified into three station groups. The distribution of shellfish in the Saemangeum area was closely related to the sediment types.

• Journal of Wetlands Research
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• v.6 no.1
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• pp.57-72
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• 2004

Macrobenthic fauna were studied on a tidal flat in Garolim Bay in July 2002, in order to understand their spatial distribution with the surface sediment types. Forty-nine stations were set on the tidal flat. A total of 147 species was sampled with the mean density of $1,140ind./m^2$ and the mean biomass of $157.2g/m^2$. The polychaetes were speices- and density-dominant faunal group with 64 species and the mean density of $791ind./m^2$. Mollusks were biomass-dominant faunal group with $132.0g/m^2$. Major dominant species were two polychaetes, Mediomastus californiensis with the mean density of $374ind./m^2$ and Heteromastus filiformis with $224ind./m^2$. Also mollusks such as Umbonium thomasi, Batillaria cumingi and Ruditapes philippinarum was relatively high in the mean density, showing the density of 45, 42, $32ind./m^2$ respectively. Especially, U. thomas was distributed in the mouth of the bay, where sediment grain size is rather coarse, and R. philippinarum at near tidal channel. Based on the cluster analysis, the macrobenthic community on the tidal flat was classified into seven station groups depending on the benthic environmental parameters(sediment types). Compared with other Korean tidal flats, species richness of Garolim tidal flats is more and less low.

• Korean Journal of Environmental Biology
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• v.37 no.4
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• pp.483-492
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• 2019

During the breeding season, both adults and immature Eurasian Oystercatchers (Haematopus ostralegus osculans) were observed to feed on prey, such as gastropods (Umbonium thomasi) and bivalves, at the tide water line around Yubu island in Korea. To determine differences in the foraging efficiency between the adult and immature birds, we recorded the feeding behavior using digiscoping with a telescope and a smartphone. We compared the pace, the prey search rate, the proportion of prey search techniques, the feeding success rate, the handling time, and the heads-up rate between the adult and immature birds. There were significant differences in the proportion of prey search techniques when gastropods were consumed and in the prey search rate and heads-up rate when bivalves were consumed but there were no significant differences in feeding success rates. Therefore, although the immature birds on Yubu Island were inferior to adults during the breeding season and they lacked the proficiency to locate prey, their overall foraging efficiency was similar to adults. This was considered to be due to the continuous eating of bivalves during the wintering season, which requires a high level of foraging efficiency.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.39 no.spc1
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• pp.132-141
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• 2006

Artificial structures have been designed as pilot structures to promote the creation and restoration of tidal flats. However, little information is available as to whether such artificial construction affects the macrobenthic community structure. We monitored the variation of the macrobenthic community structure and species composition near natural and artificial structures (seaweed and a timber fence) on the tidal flats near the Iwon Dike, Korea. In total, 137 macrobenthic species were recorded during this study, predominantly crustaceans (47%), polychaetes (18%), and molluscs (27%). Polychaetes comprised over 50% of the total density, followed by gastropods (38%) and crustaceans (11%). Macrobenthic species composition in the artificial and natural areas, was initially similar, but it differed after 7 months. The gastropod Umbonium thomasi, the most dominant species, was present at both sites in the first month after the start of the experiment, but disappeared at the artificial sites within 7 months, suggesting disturbance by the environmental factors. The number of species and diversity (H') varied significantly within sites at the beginning of the experiment, but no difference was observed after 7 months. Multivariate analysis (multidimensional scaling) revealed significant differences in community structure between the artificial and the natural areas from 7 months after the start of the experiment, except from 18 to 21 months. The community structures were mainly influenced by U. thomasi. Community structure at the artificial sites was affected by environmental variables, such as carbon, COD/IL sulfide, loss of ignition, kurtosis and silt, which changed over time. We observed no significant correlations between environmental variables and the dominant species, except in the case of Spio sp. and Macrophthalmus dilatatus, suggesting that the biological interactions and temporary disturbances such as typhoon, as well as the effects of artificial structures may also be important regulating factors in this system.