1.1. Vj tri cua san la da co trong he thong phan loai dong vat hoc
San la da co nlm trong ldp san la (Trematoda Rudolphi, 1808) thuoc nganh san dep
(Platheminthes Schneider, 1873). Nam 1754, Daubenton da phat hien san la da co diu
tien nhung chua dinh duoc loai. Sau do, Falk (1782) da phan loai san la da co dua vao vi tri ky sinh. Nam 1790, Schrank va Zeder deu tim ra mot loai san la trong da co huou va dat ten la Fasciola cervi va Festucaria cervi. Nam 1890, Rudolphi doi ten thanh gidng
Amphistoma.
Fischoeder (1901 - 1904) da phan loai nhieu loai mdi, thay ten gidng Amphistoma
Rudolphi, 1890 thanh gidng Paramphistomum, cac loai thuoc giong nay dugc xep vao
ho Paramphistomatidae.
Theo Skrjabin va cs (1977), Nguydn Thi Le va cs (1996), vi tri ciia nhung san la da co ky sinh d gia sue nhai lai Viet Nam trong he thong phan loai dong vat hoc nhu sau:
Nganh Plathelminthes Schneider, 1873 Phan nganh Platodes Leuckart, 1854
Ldp Trematoda Rudolphi, 1808
Phan ldp Prosostomadidea Skrjabin va Guschanskaja, 1962 Bo Paramphistomatida Szidat, 1936
Phan bo Paramphistomatata Skrjabin et Schulz, 1937
Ho Paramphistomatidae Fischoeder, 1901
Phan ho Paramphistomatinae Fischoeder, 1901 Gidng Paramphistomum Fischoeder, 1901
Loai Paramphistomum cervi (Zeder, 1970)
Loai Paramphistomum epiclitum (Fischoeder. 1904) Loai Paramphistomum gotoi (Fukui, 1922)
Loai Paramphistomum gracile (Fischoeder, 1901) Loai Paramphistomum iclukawai (Fukui, 1922)
Loai Paramphistomum liorchis (Fukui, 1922) Gidng GigantocotyleNasmark, 1937
Loai Gigantocotyle bathycotyl (Fischoeder, 1901) Loai Gigantocotyle siamense (Stiles et Goldberger, 1910)
Gidng Calicophoron Namark, 1937
Loai Calicophoron calicophorum(Fischoeder, 1901) Loai Calicophoron cauliorchis (Stiles et Goldberger, 1910)
Loai Calicophoron ijimai (Fukui, 1922)
Loai Calicophoron microbothrioides (Price et McIntosh, 1944)
Loai Calicophoron papillosum (Stiles et Goldberger, 1910)
Gidng CeylonocotyleNamark, 1937
Loai Ceylonocotyle scoliocoelium(Fischoeder, 1901) Loai Ceylonocotyle dicranocoelium (Fischoeder, 1901)
Loai Ceylonocotyle dinniki (Eduarko, 1982) Gidng Cotylophoron Stiles et Goldberger, 1910
Loai Cotylophoron cotylophorum(Fischoeder, 1901) Loai Cotylophoron indicum (Stiles et Goldberger, 1910)
Gidng Explanatum Namark, 1937
Loai Explanatum explanatum (Creplin, 1847)
Ho Gastrodiscidae, Stiles va Goldberger, 1910
Gidng HomalogasterPoirier, 1882
Loai Homalogasterpaloniae (Poirier, 1882) Gidng Gastrodiscoides Leiper, 1913
Loai Gastrodiscoides hominis (Leiper, 1913)
Ho Gastrothylacidae Stiles va Goldberger, 1910
Phan ho Gastrothylacinae Stiles va Goldberger, 1910 Gidng GastrothylaxPoirier, 1883
Gidng Carmyerius Stiles va Goldberger, 1910 Gidng Fischoederius Stiles va Goldberger, 1910
1.2. Hinh thai va cau tao cua san Ia da co
Cac san ia thuoc phan bo Paramphistomatata gom nhirng san la co than hinh khoi choi, mau do hong, dac biet co giac bung rat ldn d cuoi than san, 2 nhanh ruot phat trien manh va keo dai den cudi than, bit km a cudi. San co hai tinh hoan xep phia trudc buong triimg hoac co khi d sau buong trimg. San la da co lirdng tinh, thu tinh cheo va tu thu tinh.
Theo Nguydn Thi Le va cs (1996), Phan Luc (1997), tren be mat co the san la da co thudng co gai phan bd d phan trudc co the, d mat bung gai nhidu hon va ldn hon. He tieu hoa, bai tiet, than kinh va he sinh due ciia san la da co co nhirng dac didm sau:
Co quan tieu hoa bat dau tir 16 mieng d day giac mieng, hau, thuc quan, ruot. Can thurc an duoc thai ra ngoai qua 16 mieng.
Co quan bai tiet cau tao kieu nguyen don than, gom 2 ong chay doc co the va noi vdi nhau tao thanh tui bai tiet chinh md ra d mut sau co thd, m6i ong bai tiet co nhieu nhanh nho, tan ciing co te' bao ngon lira thuc hien chuc nang bai tiet.
He than kinh gom vong than kinh hau nam d phia trudc co thd, tir do co cac day than kinh chay doc vd mut trudc va mut sau co the, noi vdi nhau bdi cac cau noi ngang.
He sinh due rat phat tridn, chiem phan ldn ca thd, co cau tao phurc tap, co bo phan sinh due due va cai trdn m6i ca the.
Ve cau true vi hinh thai ciia san la da co, trudc nam 1980 chua co tac gia nao nghidn cuu. Eduardo S. L. (1983) da cong bo ket qua nghien cuu ve hinh thai va cau tao giac mieng, hau, thuc quan, gai sinh due va bd mat bieu bi ciia san la da co dudi kinh hien vi dien tir: be mat bieu bi, trdn mieng, phia trong giac bung va hau ciia san la da co co hang tram mau loi (gai thit) co tac dung h6 tro san la da co bam va lay dinh dudng. Theo Eduardo S. L., cau true vi hinh thai ciia giac bung, mieng, so lugng va sir phan bo gai thit la co sd bo sung cho viec phan loai san la da co.
Hinh 72. Mieng cua C. calicophoron (x 150)
Hinh 73. Giac bung ciia C. calicophoron (x 150)
1.3. Thanh phan loai san la da co d gia sue nhai lai
San la da co ky sinh O dong vat nhai lai g6m nhiiu loai thudc ldp Trematoda
Rudolphi, 1808. Trong cac san la ky sinh 6 loai nhai lai, c£c san la thudc ho
Paramphistomatidae duoc coi la quan trong nha't vi s6 luong ldn v i vai tro gay bdnh cua
chung (Phan Luc, 1997).
Theo Trinh Van Thinh (1963), co 7 loai san la ky sinh d da co thudc ho Paramphistomatidae: Paramphistomum cervi, Ceylonocotyle orthocoelium, Cotylophoron cotylophoron, Gastrothylax crumenifer, Fischoederius elongatus, F. cobboldi, Carmyerius spatiosus.
Dieu tra thanh ph£n loai san la da co ky sinh 6 gia sue nhai lai Vidt Nam, Drozdz J. va Malczewski A. (1967) da phat hien ra 8 giong gom 23 loai ky sinh a trau, b6, dd, ciru. Nguydn Thi Le va cs (1996) da xac dinh, ngoai cac gidng, loai ma cac tac gia trdn phat hien, gia sue nhai lai d nude ta con nhidm them 2 gidng: Explanatum Nasmark,