The distribution and the infestation rates of metacercariae in fishes from the Kum-Ho river were observed from June 1965 to August l967. The results obtained are as follows: The Fourteen kinds of metacercariae; Exorchis oviformis, Metorchis orientalis, Cyathocotyle species, Metacercaria hasegawai, Clonorchis sinensis, Metagonimus species, Pseudexorchis major, Echinochasmus species, Centrocestus species, Prosorhpynchus species, and four kinds of unidentified species, A, B, C and D were detected from 12 kinds of fishes. Clonorchis sinensis, Metagonimus species, Echinochasmus species, and Centrocestus species of the detected 14 kinds of flukes were noted to be parasited in man; Metorchis orientalis and Cyathocotyle species in avian species; and Exorchis ovifomis and Pseudexorchis major in wels, but the definite host of the other 6 kinds of flukes were not identified. Exorchis oviformis was found in 64.5 percent, of all kinds of fishes, Cyathocotyle species in 36.8 percent of 7 kinds of fishes, Metacercaria hasegawai in 36.3 percent of 8 kinds, Clonorchis sinensis in 95.0 percent of 6 kinds and Metagonimus species in 47.9 percent of 10 kinds. Concerning the infested rates of metacercaria and the length of fishes, Exorchis oviformis and Clonorchis sinensis showed increased rate by the length of fishes but the rest of fishes showed no relationship between them. The infested degree of metacercaria of Clonorchis sinensis was highest in Pseudorasbora parva with 34.3 parasites per cubic cm of flesh, of Exorchis oviformis in Carassius carassius with 7.3, of Cyathocotyle species in Acheilognathus with 6.0, and of Metacercaria hasegawai in Pseudogobio esocinus with 5.7 but Prosorhpynchus etc. were very few in all kinds of fishes. The infested rates of metacercaria in the four kinds of fishes, Pseudorasbora parva, Pungtungia herzi, Pseudogobio esocinus and Gnathopogon coreanus seemed not to be influenced by season, Spring and Autumn. In the infested rates of metacercariae by parts of fishes, Exorchis oviformis was chiefly infested in scales and fins; Metorchis orientalis, Cyathocotyle species, Clonorchis sinensis, Pseudexorchis major, Centrocestus species and Prosorhpynchus ecinatus were chiefly infested in muscle; Metacercaria hasegawai in muscle and fins; Metagonimus species chiefly in scales; and Echinochasmus chiefly in gills.
Citations
Citations to this article as recorded by
Infection characteristics of Metagonimus species (Digenea: Heterophyidae) metacercariae in fish from major rivers of Korea Woon-Mok Sohn Parasites, Hosts and Diseases.2024; 62(1): 1. CrossRef
Current status of Clonorchis sinensis and clonorchiasis in Korea: epidemiological perspectives integrating the data from human and intermediate hosts Won Gi Yoo, Woon-Mok Sohn, Byoung-Kuk Na Parasitology.2022; 149(10): 1296. CrossRef
Investigation of Reportable Communicable Diseases and Parasites in Aquatic Organisms Living in the Estuary of the Han River. Jin Hui Kim, Jun Young Song, Jung-Ho Lee, Jun Wook Hur, Se Ryun Kwon, Joon Yeong Kwon Korean Journal of Ecology and Environment.2019; 52(4): 306. CrossRef
Infection Status with Digenetic Trematode Metacercariae in Fishes from Coastal Lakes in Gangwon-do, Republic of Korea Woon-Mok Sohn, Byoung-Kuk Na, Shin-Hyeong Cho, Soon-Won Lee The Korean Journal of Parasitology.2019; 57(6): 681. CrossRef
Infections with Centrocestus armatus Metacercariae in Fishes from Water Systems of Major Rivers in Republic of Korea Woon-Mok Sohn, Byoung-Kuk Na, Shin-Hyeong Cho, Jung-Won Ju, Cheon-Hyeon Kim, Ki-Bok Yoon, Jai-Dong Kim, Dong Cheol Son, Soon-Won Lee The Korean Journal of Parasitology.2018; 56(4): 341. CrossRef
War on Two Fronts: The Fight against Parasites in Korea and Vietnam Mark Harrison, Sung Vin Yim Medical History.2017; 61(3): 401. CrossRef
Trematode Metacercariae in Freshwater Fish from Water Systems of Hantangang and Imjingang in Republic of Korea Woon-Mok Sohn, Byoung-Kuk Na, Shin-Hyeong Cho, Soon-Won Lee, Seung-Bong Choi, Won-Seok Seok The Korean Journal of Parasitology.2015; 53(3): 289. CrossRef
Fish-borne Zoonotic Trematode Metacercariae in the Republic of Korea Woon-Mok Sohn The Korean Journal of Parasitology.2009; 47(Suppl): S103. CrossRef
Infection status with trematode metacercariae in the fresh-water fish from Chunamchosuchi (pond), Uichang-gun, Kyongsangnam-do, Korea W M Sohn, Y S Choi The Korean Journal of Parasitology.1997; 35(3): 165. CrossRef
Trematode infections in the small intestine of Egretta alba modesta in Kangwon-do Y S Ryang, Y K Ahn, M B Yoon The Korean Journal of Parasitology.1991; 29(3): 227. CrossRef
Infection status of Pseudorasbora parva collected from the Sunam stream with metacercariae of Metorchis orientalis W M Sohn The Korean Journal of Parasitology.1991; 29(3): 311. CrossRef
Study on Centrocestus armatus in Korea. I. Infection status of Zacco platypus and Z. temminckii with the metacercariae of C. armatus S J Hong, H C Woo, I T Kim The Korean Journal of Parasitology.1989; 27(1): 41. CrossRef
Changing patterns of infection with digenetic larval trematodes from fresh-water fish in river Taewha, Kyongnam province Chong Yoon Joo The Korean Journal of Parasitology.1988; 26(4): 263. CrossRef
Studies on the Metagonimus fluke in the Daecheong reservoir and the upper stream of Geum river, Korea Chong Hwan Kim, Nam Man Kim, Chan Hyun Lee, Jin Suk Park The Korean Journal of Parasitology.1987; 25(1): 69. CrossRef
Studies on the intestinal fluke, Metagonimus yokogawai Katsurada, 1912 in Korea Geographical distribution of sweetfish and infection status with Metagonimus metacercaria in south-eastern area of Korea Chul Yong Song, Soon Hyung Lee, Sang Rin Jeon The Korean Journal of Parasitology.1985; 23(1): 123. CrossRef
Seasonal variations of metacercarial density of Clonorchis sinensis in fish intermediate host, Pseudorasbora parva Shin Yong Kang, Suk Il Kim, Seung Yull Cho The Korean Journal of Parasitology.1985; 23(1): 87. CrossRef
Metacercariae of Echinochasmus japonicus encysted in a fresh water fish, Pseudorasbora parva, and their development in experimental mice Jong Yil Chai, Song Jong Hong, Dong Woo Son, Soon Hyung Lee, Byong Seol Seo The Korean Journal of Parasitology.1985; 23(2): 221. CrossRef
Studies on intestinal trematodes in Korea XX. Four cases of natural human infection by Echinochasmus japonicus Byong Seol Seo, Soon Hyung Lee, Jong Yil Chai, Sung Jong Hong The Korean Journal of Parasitology.1985; 23(2): 214. CrossRef
Survey on encysted cercaria of trematodes from fresh-water fishes in Tongjin riverside areas in Korea Jae Ku Rhee, Moon Ho Rim, Byeong Kirl Baek, Ho Il Lee The Korean Journal of Parasitology.1984; 22(2): 190. CrossRef
Infestation of larval trematodes from fresh-water fish and brackish-water fish in river Taechong, Kyungpook province, Korea Chong Yoon Joo, Moo Kil Park, Dong Wik Choi The Korean Journal of Parasitology.1983; 21(1): 6. CrossRef
Epidemiological studies on Clonorchis sinensis infection along the Nam-river in Gyeongnam province, Korea Kyoung Hoon Bae, Yung Kyum Ahn, Chin Thack Soh, Hiroshi Tsutsumi The Korean Journal of Parasitology.1983; 21(2): 167. CrossRef
Infestation with larval trematodes from fresh-water fish in natural and fish breeding ponds Jong Hwan Kim, Dong Wik Choi The Korean Journal of Parasitology.1981; 19(2): 157. CrossRef
Study on the Metagonimus sp. in Gum river basin, Chungchung-nam Do, Korea Chong Hwan Kim The Korean Journal of Parasitology.1980; 18(2): 215. CrossRef
Epidemiological studies of Clonorchis sinensis in vicinity of river Taewha, Kyungnam province, Korea Chong Yoon Joo The Korean Journal of Parasitology.1980; 18(2): 199. CrossRef
Demonstration of Metagonimus yokogawai metacercariae from Plecoglossus altivelis in river Ahnseong, Kyungpook province, Korea Jong Woo Suh, Dong Wik Choi The Korean Journal of Parasitology.1979; 17(1): 45. CrossRef
Metacercarial density of Metagonimus yokogawai in Plecoglossus altivelis in Kyungpook province, Korea Jae Taeck Hwang, Dong Wik Choi The Korean Journal of Parasitology.1977; 15(1): 30. CrossRef
Study on Metagonimus yokogawai(Katsurada, 1912) in Korea IV. An epidemiological investigation along Tamjin River basin, South Cholla Do, Korea Jong Yil Chai, Seung Yull Cho, Byong Seol Seo The Korean Journal of Parasitology.1977; 15(2): 115. CrossRef
Clonorchis sinensis in Kyungpook province, Korea 2. Demonstration of metacercaria of Clonorchis sinensis from fresh-water fish Dong Wik Choi The Korean Journal of Parasitology.1976; 14(1): 10. CrossRef
Study on Metagonimus yokogawai(Katsurada, 1912) in Korea[I. On the metacercaria, its distribution in the second intermediate host and the development in the final host Byong Seol Seo, Nam Tae Hong The Korean Journal of Parasitology.1969; 7(3): 129. CrossRef
It is well established that guinea pig, rabbit and rat are equally susceptible to experimental infection with the Chinese liver fluke, Clonorchis sinensis. However, little work has been done on the studies of the host-parasite relationships between the liver fluke and mouse host. The experiments were undertaken to investigate the susceptibility, development and sexual maturity of Clonorchis sinensis in mouse host. The metacercariae of C.
sinensis used in these experiments were isolated from the fish, Pseudorasbora parva by digestion technic. And in all these studies the mice weighing around 20 g were commercially purchased and infected with the metacercariae under slightly narcotized condition with ether. The animals were starved overnight before infection. The mature metacercariae, e.g. 5, 10, 20, 30, 50, 200 were given orally into stomach by means of the polyethylene tubing (intramedic, Clay Adams, Inc.PE-90/S12) respectively to each mouse of groups ranging 4 to l5. After various period of infection, the mouse liver was first opened along the common bile duct and cut into small pieces for collecting and counting the worms. For the histopathological examination of the liver, the tissue specimens were fixed in formalin, sectioned and stained with haematoxylin-eosin. Another experiment was separately set up for the study of egg laying capacity of C. sinensis in mice. The following results were obtained: Mice were successfully infected with metacercariae of C. sinensis in all cases of the groups except the group given 5 and 10 metacercariae, in which the infection was not established in one case of each group. Therefore it is assumed that mice are susceptible to infection with this worm. In an earlier period ot infection, the worms were found mostly in common bile duct and intrahepatic biliary passages with same rate, however in later period, they were seen rather in the intrahepatic biliary passages (73 percent) than in common bile duct and gall bladder. The recovery rate of fully matured adult worms (less than 10 percent) was lower than that of the average recovery rate of the worms in general (22.3 percent). Under same age of infection or even in same host, the size of collected worms showed the great variations. Oral sucker was smaller in size than ventral sucker in the early stage of infection. After 11 days of infection it reversed. The posterior part of body length began to elongate since 5 days after infection, and therefore the ratio of antero-posterior part became l to 3.
Fully matured adult worms were only collected after 30 days of infection. The first positive appearance of eggs in feces was on the 17th and 18th day after infection. However, the egg-laying capacity in mouse host seemed to be stabilized since 30 days after infection. Histopathologically, the cystic dilatation of medium to small biliary passages was noted and focal but diffusely scattered necrosis of the liver cells with scarce inflammatory cells was also observed as well as the hepatocellular degeneration, diffuse vascular congestions and adenomatous proliferationof bile duct.
Citations
Citations to this article as recorded by
Strain variation in the susceptibility and immune response to Clonorchis sinensis infection in mice Md. Hafiz Uddin, Shunyu Li, Young Mee Bae, Min-Ho Choi, Sung-Tae Hong Parasitology International.2012; 61(1): 118. CrossRef
Image analytical observation on the growth and development of Clonorchis sinensis in rats J Kim The Korean Journal of Parasitology.1995; 33(4): 281. CrossRef
Egg production of Clonorchis sinensis in different strains of inbred mice J I Kim, D I Chung, D W Choi The Korean Journal of Parasitology.1992; 30(3): 169. CrossRef
Intensity of infection and development of adult Clonorchis sinensis in hamsters Dong Il Chung, Dong Wik Choi The Korean Journal of Parasitology.1988; 26(1): 9. CrossRef
Studies on intestinal trematodes in Korea IX. Recovery rate and development of Fibricola seoulensis in experimental animals Sung Jong Hong, Soon Hyung Lee, Byong Seol Seo, Sung Tae Hong, Jong Yil Chai The Korean Journal of Parasitology.1983; 21(2): 224. CrossRef
Ultrastructural changes of the hepatocytes and biliary epithelia due to Clonorchis sinensis in guinea pigs Sun Yong Lee, Soon Hyung Lee, Je Geun Chi The Korean Journal of Parasitology.1978; 16(2): 88. CrossRef
Effects of prednisolone injection on the liver of the mouse inoculated with the adult worms of Clonorchis sinensis intraperitoneally Soon Hyung Lee, Chul Yong Song, Je Geun Chi The Korean Journal of Parasitology.1978; 16(2): 69. CrossRef
An experimental study on the mouse intraperitoneal inoculation of the adult worm of Clonorchis sinensis Chul Yong Song, Soon Hyung Lee, Je Geun Chi The Korean Journal of Parasitology.1977; 15(2): 75. CrossRef
Ultrastructural studies on the integument of digenetic trematodes were investigated by several workers (Senft et al., 1961; Bjorkman and Thorsell, 1964; Burton, l966; Erasmus, l968; Morris and Threadgold, 1967, l968).
Clonorchis sinensis is a common parasite of human beings in the Far East. But as far little has been written on ultrastructure of the integument of this parasite. This study was carried out systematically to elucidate the ultrastructure of the integument of adult C. sinensis, and the results are summarized as follows: The integument of C.
sinensis was organized in two parts; the epidermis and the muscular layer. The apical surface and basal surface of the epidermis were covered with typical plasma membrane and irregularly invaginated from the surface. Plasma membrane at perisuckers was extremely folded and appeared as if the epidermis might be divided with the layer. The syncytial epidermis contained mitochondria and numerous secretory bodies, and which was connected by cytoplasmic processes to nucleated epidermal cells lying in the parenchyma. The mitochondriae, the secretory bodies, the granular endoplasmic reticulum, the Golgi bodies and the free ribosomes were present in the perinuclear cytoplasm of epidermal cells, but no organelle was observed in processes of epidermal cell except some secretory bodies. The fibrous layer consists of argentophile fiber and collagenous fiber, in which the circular muscle bundles and longitudinal muscle bundles were embedded. Bundles of muscle fiber are weIl developed at the perisucker, and mitochondriae in this portion contain many cristae as compared with any other parts of C. sinensis.
Citations
Citations to this article as recorded by
Clonorchiasis in Korea H J Rim The Korean Journal of Parasitology.1990; 28(Suppl): 63. CrossRef
A Study on the structure of Clonorchis sinensis, a liver fluke IV. Probable functions of the Laurer's canal Kye Heon Jeong The Korean Journal of Parasitology.1983; 21(2): 209. CrossRef
A Study on the fine tegumental structures of the metacercaria and juvenile stages of Clonorchis sinensis Soon Hyung Lee, Sung Tae Hong, Byong Seol Seo The Korean Journal of Parasitology.1982; 20(2): 123. CrossRef
Morphological observations on Clonorchis sinensis obtained from rats treated with praziquantel Han Jong Rim, Hee Young Park, Soo Jin Kim, Sook Hee Lee The Korean Journal of Parasitology.1980; 18(2): 192. CrossRef
A study on the fine structure of Clonorchis sinensis, a liver fluke 1. The body wall and the nervous system Kye Heon Jeong, Han Jong Rim, Chang Whan Kim The Korean Journal of Parasitology.1978; 16(2): 156. CrossRef
A survey for nematode and cestode parasites of rodents in Korea has been carried out at the areas of Chulwon, Kumwha, Pochon, Paju and Chungpyong, Kyunggi-Do. A total of 300 rodents of seven species was examined, comprising of 219 A.
agrarius, 33 R. norvegicus, 8 R. alexandrinus, 14 Mus musculus yamashinai, Microtus fortis pellceus, 21 Crocidura russula and a Cricetulus trition nester. The following fifteen species belonging to thirteen genera were identified: NEMATODA: Heterakis spumosa, Syphacia obvelata, Nippostrongylus muris, Protospirura muris, Capillaria hepatica, Capillaria sp., Heligmosomum sp., Heligmosomoides sp., Rictularia sp. and Gongylonema sp. CESTODA: Hymenolepis nana, Hymenolepis diminuta, Raillietina coreensis, Paranoplocephala sp. and Cysticercus fasciolaris(the larva of Taenia taeniaeformis).
Citations
Citations to this article as recorded by
The Parasites that can be Found in the Mus musculus House Mice Dilara KARAMAN, Ahmet Onur GİRİŞGİN Commagene Journal of Biology.2022;[Epub] CrossRef
Metabarcoding of bacteria and parasites in the gut of Apodemus agrarius Soo Lim Kim, Jun Ho Choi, Myung-hee Yi, Seogwon Lee, Myungjun Kim, Singeun Oh, In-Yong Lee, Bo-Young Jeon, Tai-Soon Yong, Ju Yeong Kim Parasites & Vectors.2022;[Epub] CrossRef
Morphological Observation on Physaloptera Species (Nematoda: Spirurida: Physalopteridae) in Murine Rodents of Indonesia and East Asian Islands with Special Reference to Their Zoogeographical Features Hideo Hasegawa, Kartika Dewi, Mitsuhiko Asakawa Tropical Natural History.2022; 22: 119. CrossRef
Rictularia jiyeoni n. sp. (Nematoda: Rictulariidae) from the Striped Field Mouse, Apodemus agrarius, in Korea Bae Keun Park, Hyeon Cheol Kim, Eui Ju Hong, Si Yun Ryu, Joon Seok Chae Journal of Parasitology.2021;[Epub] CrossRef
Infections of Intestinal Helminth at Two Species of Field Mice, Apodemus agrarius and A. Peninsulae, in Gangwondo and Chungcheongnam-do, Korea Jae-Hyung Lee, Shuang Gong, Yung Chul Park, Hyun-Ju Kim, In-Wook Choi, Young-Ha Lee The Korean Journal of Parasitology.2018; 56(3): 301. CrossRef
Intestinal Helminthic Infections in Striped Field Mice,Apodemus agrarius, from Two Southern Regions of Korea Woon-Mok Sohn, Byoung-Kuk Na, Hyeon-Je Song, Chung-Mo Kim, Gi-Jin Nam The Korean Journal of Parasitology.2014; 52(4): 419. CrossRef
An overview of the host spectrum and distribution of Calodium hepaticum (syn. Capillaria hepatica): part 1—Muroidea Hans-Peter Fuehrer Parasitology Research.2014; 113(2): 619. CrossRef
Helminth fauna of Rattus norvegicus Berkenhout, 1769 from the Belgrade area, Serbia D. Kataranovski, Milena Kataranovski, Isidora Deljanin Archives of Biological Sciences.2010; 62(4): 1091. CrossRef
First record of Calodium hepaticum and Taenia taeniaeformis liver infection in wild Norway rats (Rattus norvegicus) in Serbia Milena Kataranovski, Lidija Zolotarevski, Sandra Belij, Ivana Mirkov, Jelena Stosic, Aleksandra Popov, D. Kataranovski Archives of Biological Sciences.2010; 62(2): 431. CrossRef
Helminths in Rattus norvegicus captured in Chunchon, Korea J K Seong, S Huh, J S Lee, Y S Oh The Korean Journal of Parasitology.1995; 33(3): 235. CrossRef
During 1964 to 1967, a survey of 30,534 persons for filariasis was made on all over the country with the following results: Among 24,816 draftees from all over the country in the army recruitment camp 155(0.63 %) were found infected with Brugia malayi. Cheju Do showed the highest microfilaria rate(3.5 %), North Kyongsang Do(1.4 %) the next and South Cholla Do(1.2 %) the third. Blood films from 2,308 inhabitants were examined and 407(17.6 %) showed microfilaria in Cheju Do. 30(3.1 %) out of 974 inhabitants in North Kyongsang Do were found to be infected. The microfilaria rates were 2.0 per cent for 400 inhabitants of Chindo island in South Cholla Do. However, no positive case of microfilaria was found in the inhabitants of Kokumdo among 1,820 persons examined in South Cholla Do and of Namhae island(among 165 persons examined) in South Kyongsang Do. The mean microfilarial density per 20 cu. mm of blood was 52.6 in the inhabitants of Cheju Do, 12.2 in North Kyongsang Do and 27.3 in Chindo island(South Cholla Do). Any distinct relationship between the incidence of positive cases of microfilariae and age or sex of the cases was not observed in Cheju Do. However, in Norh Kyongsang Do and South Cholla Do the microfilaria rate of the male group is higher than the one of the female group of the inhabitants.
From the above survey results it turned out that filariasis was found throughout Southern Korea except Kyonggi Do and South Kyongsang Do. A total 30,534 persons examined, 601(2.0 %) were found to be infected by Brugia malayi. Therefore, it seems that there are some endemic foci of malayian filariasis in three main areas such as North Kyongsang Do, South Cholla Do and Cheju Do.
Citations
Citations to this article as recorded by
Review of Zoonotic Parasites in Medical and Veterinary Fields in the Republic of Korea Heejeong Youn The Korean Journal of Parasitology.2009; 47(Suppl): S133. CrossRef
Successful Control of Lymphatic Filariasis in the Republic of Korea Hyeng-Il Cheun, Yoon Kong, Shin-Hyeong Cho, Jong-Soo Lee, Jong-Yil Chai, Joo-Shil Lee, Jong-Koo Lee, Tong-Soo Kim The Korean Journal of Parasitology.2009; 47(4): 323. CrossRef
New Records and Reference Collection of Mosquitoes (Diptera: Culicidae) on Jeju Island, Republic of Korea Heung Chul KIM, Richard C. WILKERSON, James E. PECOR, Won Ja LEE, John S. LEE, Monica L. O'Guinn, Terry A. KLEIN Entomological Research.2005; 35(1): 55. CrossRef
A survey of Brugia malayi infection on the Heugsan Islands, Korea Jong-Yil Chai, Soon-Hyung Lee, Sung-Yil Choi, Jong-Soo Lee, Tai-Soon Yong, Kyun-Jong Park, Kyeong-Ae Yang, Keon-Hoon Lee, Mi-Jeng Park, Hyung-Ran Park, Mi-Ja Kim, Han-Jong Rim The Korean Journal of Parasitology.2003; 41(1): 69. CrossRef
Studies on the current epidemiological situation of brugian filariasis in endemic areas of Korea Yung Han Paik, You Jung Cho, Do Seo Koo, Han Il Ree, Jae Chul Shim The Korean Journal of Parasitology.1988; 26(4): 255. CrossRef
Epidemiological studies on malayan filariasis in an inland area in Kyungpook, Korea 3. Ecological survey of vector mosquitoes of Brugia malayi Hewng Il Lee, Dong Wik Choi, Doo Hyun Baik, Chong Yoon Joo The Korean Journal of Parasitology.1986; 24(1): 15. CrossRef
Natural transition of endemicity of Malayan flariasis in inland Korea Pattern of change in microfilaria rate among inhabitants of Yongpung (former Yongju) area during the period of the last seven years Dong Chan Kim, On Young Lee, Eui Beom Jeong, Min Gyu Jeong The Korean Journal of Parasitology.1980; 18(2): 171. CrossRef
Morphology of the microfilaria of Brugia malayi in Cheju-Do, Korea Byong Seol Seo The Korean Journal of Parasitology.1976; 14(1): 41. CrossRef
Ecology of filariasis on Che Ju Island Joung Soon Kim, Won Young Lee, Suk Lak Chun The Korean Journal of Parasitology.1973; 11(1): 33. CrossRef
Effectiveness of diethylcarbamazine in the mass treatment of malayan filariasis with low dosage schedule Byong Seol Seo, Woo Jung Lee The Korean Journal of Parasitology.1973; 11(2): 61. CrossRef