Mactra veneriformis, an Intertidal Clam, as a New Second Intermediate Host for Acanthoparyphium marilae (Digenea: Echinostomatidae)

Abstract

The genus Acanthoparyphium (Digenea: Echinostomatidae) is a group of minute intestinal trematodes which parasitize the small intestine of aquatic birds in marine areas of the Republic of Korea, Japan, USA, the Philippines, Kuwait, India, Puerto Rico, and Australia [1][2][3][4][5][6][7][8]. Brackish water gastropods, bivalves, or oysters play the role of a first or second intermediate host, or both [1][2][3][4][5][6][7][8].In the Republic of Korea, Chai et al. [7] reported recently that Acanthoparyphium tyosenense Yamaguti, 1939 causes human infections. The complete life history of A. tyosenense has been previously elucidated; several species of brackish water mollusks have been demonstrated to harbor the metacercariae of A. tyosenense [7,9,10]. The adult parasite of A. tyosenense was identified originally in velvet scoters, Melanitta fusca stejnegeri, and common scoters, Melanitta nigra americana, as natural infections in Korea [11]. Its life cycle was suggested also in Japan [10].Acanthoparyphium marilae Yamaguti, 1934 was originally described in velvet scoters (Marila marila mariloides and M. fusca stejnegeri) in Japan [12], and thereafter in common scoters (M. nigra americana) in Korea [11], and greater scaups (Aythya marila mariloides) and great knots (Calidris tenirostris) in China [13]. Although intertidal mollusk species are generally known to harbor the metacercariae of Acanthoparyphium species, the intermediate host for A. marilae remained to be determined. In the present study, Mactra veneriformis, a common intertidal bivalve species in the Republic of Korea, was subjected to a search for Acanthoparyphium metacercariae in order to determine the intermediate host for A. marilae.The metacercariae of A. marilae, together with those of A. tyosenense and Himasthla alincia, were detected in the bivalve, M. veneriformis, which were purchased in a southwestern costal area, Buangun, Jeollabuk-do, the Republic of Korea (Table 1). The metacercariae were isolated from the muscles and gills of the bivalves with a sharp, pointed pin and a stereomicroscope. After placing them on glass slides, a cover slip was placed on the specimen and gentle pressure was applied. The metacercariae were then identified individually using a light microscope. The metacercariae of A. marilae were discriminated from those of A. tyosenense by their smaller cyst size, and average diameters of 305-330 m for A. marilae (this study) and 420-460 m for A. tyosenense [7].A total of 128 A. marilae metacercariae were recovered from 10 M. veneriformis, with an infection rate of 100% and an average number of 12.8 metacercariae per clam ( Abstract: Metacercariae of Acanthoparyphium marilae Yamaguti, 1934 (Digenea: Echinostomatidae) were discovered in an intertidal clam, Mactra veneriformis, in a southwestern coastal area of the Republic of Korea. A total of 128 metacercariae were detected from 10 clams examined. They were round, 320 m in average diameter, with 23 collar spines. They were fed experimentally to chicks, and 10 days later adult flukes ...

Prevalence and Density of Digenetic Trematode Metacercariae in Clams and Oysters from Western Coastal Regions of the Republic of Korea

“…However, A. tyosenense is a valid species, and it differs from A. kurogamo by its body shape and position of the acetabulum and testes [ 14 , 24 ]. Although another species, A. marilae , has been reported in Korea [ 15 ], the morphological characteristics of our specimens are well corresponded with those of A. tyosenense ( Fig. 2 ).…”

“…After then, Chai et al [ 14 ] discovered human infections with A. tyosenense , and they also investigated the metacercarial infections of this fluke in 5 species of bivalves, i.e., M. veneriformis, Solen grandis, Meretrix petechialis, C. sinensis , and Scapharca broughtonii , and a marine snail, Neverita bicolor , to survey on the sources of human infections. Han and Chai [ 15 ] reported for the first time that M. veneriformis act as the second intermediate host of Acanthoparyphium marilae .…”

Acanthoparyphium shinanense n. sp. (Digenea: Echinostomatidae) from Experimental Chicks Infected with Metacercariae Encysted in Brackish Water Clams in the Republic of Korea

“… a Based on the literature [ 5 – 7 , 11 , 14 , 18 , 19 , 25 , 39 – 41 ]. b Human infections were reported in Korea [ 9 ].…”

“…Flukes of the genus Acanthoparyphium Dietz, 1909 are parasitic in aquatic birds of marine or brackish water in Tunisia, the Republic of Korea (= Korea), Japan, Australia, New Zealand, USA, Taiwan, the Philippines, Kuwait, and Ukraine [4][5][6][7][8][9][10][11][12]. At least 19 species have been described in this genus (see Discussion), although 4 of them were suggested to be synonyms of Acanthoparyphium spinulosum Johnston, 1917, which was originally described from Australia [13].…”

“…In Korea, 2 species, Acanthoparyphium tyosenense Yamaguti, 1939 and Acanthoparyphium marilae Yamaguti, 1934, have been found [9,11]. In Japan, 6 species, including Acanthoparyphium charadrii Yamaguti, 1939 (synonymized with A. spinulosum by Soota et al [23]), Acanthoparyphium kurogamo Yamaguti, 1939, A. marilae, Acanthoparyphium melanittae Yamaguti, 1939, Acanthoparyphium spinulosum suzugamo Yamaguti, 1939 (synonymized with A. spinulosum by Skrjabin and Bashkirova [24]), and Acanthoparyphium squatarolae Yamaguti, 1934 have been described [4,5].…”