• Animal Systematics, Evolution and Diversity
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• v.27 no.1
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• pp.1-17
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• 2011

Thais Roding, 1798, commonly known as rock-shell, is among the most frequently found gastropod genera worldwide on intertidal rocky shores including those of Japan, China, Taiwan and Korea. This group contains important species in many marine environmental studies but species-level taxonomy of the group is quite complicated due to the morphological variations in shell characters. This study examined the genetic variations and relationships among three Korean Thais species based on the partial nucleotide sequences of mitochondrial cox1 gene fragments. Phylogenetic trees from different analytic methods (maximum parsimony, neighbor-joining, and maximum likelihood) showed that T. bronni and T. luteostoma are closely related, indicating the most recent common ancestry. The low sequence divergence found between T. luteostoma and T. bronni, ranging from 1.53% to 3.19%, also corroborates this idea. Further molecular survey using different molecular marker is required to fully understand a detailed picture of the origin for their low level of interspecific sequence divergence. Sequence comparisons among conspecific individuals revealed extensive sequence variations within the three species with maximum values of 2.43% in T. clavigera and 1.37% in both T. bronni and T. luteostoma. In addition, there is an unexpectedly high level of mitochondrial genotypic diversity within each of the three Korean Thais species. The high genetic diversity revealed in Korean Thais species is likely to reflect genetic diversity introduced from potential source populations with diverse geographic origins, such as Taiwan, Hong Kong, and a variety of different coastal regions in South China and Japan. Additional sequence analysis with comprehensive taxon sampling from unstudied potential source populations will be also needed to address the origin and key factors for the high level of genetic diversity discovered within the three Korean Thais species studied.

• The Korean Journal of Malacology
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• v.26 no.1
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• pp.97-105
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• 2010

Annual gonad development of the rock shell, Thais clavigera distributed in Jeju Port was investigated over a 12 month period from March 1998 to February 1999. Monthly change in gonad development was examined using histology. Gametogenesis of T. clavigera in the study area initiated as early as in October and fully ripe eggs could be observed from May to July. Percent gonad area (PGA) also increased rapidly from May to July then dropped in August when the water temperature remained $22.6-24.5^{\circ}C$, suggesting that rock shell released their eggs during this period. All female rock shell collected during the course of study exhibited pseudo-penis in the head, indicating that a certain level of imposex had progressed in the study site. Relative penis size index (RPSI), an indicator of level of imposex phenomenon varied 59.5-173.4% and this value was relatively higher than the index reported from elsewhere. It was believed that such imposex phenomenon observed in T. clavigera was caused by endocrine disruption by chemical contaminants such as TBTs released from biocidal paints in the port environment.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.36 no.6
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• pp.632-640
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• 2003

Geographic variation in shell morphology of Thais clavigera $(K\"{u}ster)$ (Gastropoda: Muricidae) was investigated using samples collected from 24 sites along the Korean coast. Multivariate statistical analysis was applied to 9 morphometric and 4 categorical variables. The shells of T. clavigera were classified into two distinct morph types (Type-W and -E). Temperature and salinity of the sampling sites were significantly correlated with the incidence of morph types. Relative abundance of Type-W (thin, yellowish brown shell with triangular nodules) was positively correlated with temperature and negatively correlated with salinity. In contrast, relative abundance of Type-E (thick, dark purple shell with round nodules) was negatively correlated with temperature and positively correlated with salinity. Possible correlation between environmental factors (temperature and salinity) and morphological variations in the shells were discussed.

• The Journal of Advanced Prosthodontics
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• v.3 no.3
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• pp.132-135
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• 2011

PURPOSE. To study the distribution of various occlusal schemes as well as associated static occlusal relationship among Thais. MATERIALS AND METHODS. The subjects'occlusal schemes on the left and right sides were classified as canine protected occlusion, group function, or unclassified according to the definition from Glossary of Prosthodontic Terms ($8^{th}$ edition). In addition, the presence of occlusal interferences during mandibular excursions were recorded. The measurement of the horizontal overlap and vertical overlap was also performed. Chi-square, One-way ANAVA and Mann-Whitney U statistical tests were used with level of significance set at P=.05. RESULTS. Total of 104 subjects were included in this study. The ratio for male to female was 1.8 to 1. Average age of the population was $25.01{\pm}6.87$ years old. The mean vertical overlap and horizontal overlap were $1.94{\pm}1.20$ and $2.41{\pm}1.32$ mm respectively. The majority of the populations (68.3%) possessed group function occlusal scheme. For the remaining, 17.3% possess canine protected occlusion and 12.5% possess combination of both occlusal schemes. We also found that occlusal interference was presented in 20.2% of the population. The most common was protrusive interference (57.14%), the second was balancing interference (38.1%) and the third was working interference (4.1%). CONCLUSION. Among Thais, the most common occlusal scheme was group function, however there were no significant occlusal factors related to any particular occlusal scheme.

• Proceedings of the Zoological Society Korea Conference
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• 1999.10b
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• pp.172.1-172
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• 1999

No Abstract, See Full Text

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2000.05a
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• pp.375-376
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• 2000

Sex ratio of a population is a key factor to determine reproductive rate of the population. If the population has skewed sex ratio to the male, the population size may decline gradually at an area which it inhabits, and, furthermore, if a species plays an ecologically important role in its community (e.g., a keystone species in Paine, 1966), its potential reproductive rate will be to form a characterized community because community structure is strongly influenced by the abundance of the ecologically important species (Hughes, 1986). A number of workers (e.g., Bryan et al., 1986 in Nucella lapillus; Spence et al., 1990 in Thais haemastoma) suggested that high frequency and/or late stage of imposex might affect the female mortality and normal reproduction adversely. Consequently, the imposex could affect sex ratio of natural population of some neogastropod including thaisid species. (omitted)

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2000.05a
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• pp.533-534
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• 2000

In general, intertidal gastropods display a considerable amount of intraspecific shell variation (De Wolf et al., 1998). Particularly, thaisid species, including Thais clavigera(=T.c.), have been shown a variety of shell variation in the world ocean (e.g. T, emerginata in Kitching, 1976). Nomura (1926) noted local variation of shell morphology based on five Japanese populations. Ahe (1985) classified Japanese T.c. into two forms (Form-C ＆. -P). In the Korean waters, a strong variation in nodule shape of T.c, shell has also been noted by Choe ＆ Park (1997). Taxonomy of T.c. is controversial so far. (omitted)

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 1997.06a
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• pp.305-306
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• 1997

• Asian Pacific Journal of Cancer Prevention
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• v.17 no.2
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• pp.845-849
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• 2016

Background: Worldwide, the incidence of cancers is increasing and is becoming a major public health issue, including those in the Asia Pacific region. South-East Asia is a region with diverse populations with different disease spectra. This study looked at the spectrum of cancers among South-East Asians working in Brunei Darussalam. Materials and Methods: The cancer registry from 1994 to 2012 maintained by the State Laboratory was retrospectively reviewed. Crude incidence rates were calculated based on the population census of 2010. Results: Altogether, there was a total of 418 cancer cases diagnosed among South-East Asians, giving an incidence of 5.1% (n=418/8,253). The affected nationals in decreasing frequency were Malaysians (53.1%), followed by Filipinos (25.8%), Indonesians (15.3%), Thais (3.8%), Myanmese (1.7%) and Vietnamese (0.2%) with no recorded cases for Singapore and the People's Republic of Laos. The overall mean age of diagnosis was $46.1{\pm}4.2$ years old, with an increasing trend over the years (p<0.05 ANOVA). The overall gender ratio was 42.3:57.7 (male:female), more females among the Filipinos and Indonesians, more males among the Thais, and equal representation among the Malaysians and the Myanmese. The most common were cancers of the digestive system (19.9%), followed by female reproductive/gynecologic system (16.0%), breast (15.6%), hematological/lymphatic (12.0%) and head/neck (8.1%). There were differences in the prevalence of cancers among the various nationalities with highest crude incidence rate among the Myanmese (141.2/100,000), followed by the Malaysian (88.5/100,000), and the Filipinos (40.6/100,000) and the lowest among the Thais (18.4/100,000), Indonesians (10.5/100,000) and the Vietnamese (6.3/100,000). Conclusions: Cancers among South-East Asian residing in Brunei Darussalam accounted for 5.1% of all cancers. The most common cancers were cancers of the digestive, gynecologic/female reproductive system and breast with certain types slowly increasing in proportions. There mean age of diagnoses was increasing.

• Proceedings of the Korea Society of Environmental Toocicology Conference
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• 2002.05a
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• pp.69-70
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• 2002