Studies on the geographical distribution and morphology of the oncomelaniid snails, intermediate hosts of Schistosoma japonicum in Hupeh Province, China.

The present paper deals with the geographical distribution and morphology of the Oncomelaniid snails, the molluscan intermediate host of Schistosoma japonicum in Hupeh province. Up to the time of writing, the Oncomelaniid snails have been discovered in some 36 districts and 3 cities of this province, namely, Itu(宜都), Y(?)anan(远安), Tangyan(當陽), Kiangling(江陵), Sungtze(松滋), Kungan(公安), Shihshow(石首), Kienli(监利), Hung Hu(洪湖), Mien yang(沔陽), Tsienkiang(潜江), Kingmen(荆门), Tienmen(天门), Kingshan(京山), Chungsiang(锺祥), Kucheng(穀城), Siangyang(襄阳), Nanchang(南漳), Hwangpei(黄陂), Siaokan(孝感), Y(?)nmeng(云夢), Yingcheng(应城), Hanchwan(汉川), Hanyang(汉阳), Kiayu(嘉鱼), Puchi(蒲圻), Tungshan(通山), Sinchow(新洲), Ungkung(黄岡), Ocheng(鄂城), Hsi Shui(浠水), Tayeh(大治), Yangh sin (阳新), Kichun(蘄春), Kwangtsi(广济), Hwangmei(黄梅), Shasi(沙市),Wuhan(武汉市), Hwangshih City(黄石市). All of these areas are the endemic regions of Schistosomiasis japonica. The natural conditions in these endemic areas, such as temperate climate, abundant rainfall, extensive irrigation and rich soil, favor the development of the intermediate host and facilitate the spread of this disease. With respect to topographic conditions,the high mountains stand in the northwest and the large lakes lie low in the southeast. Hence it appears that the smooth-shelled Oncomelania is limited to the middle of Han Kiang(汉江)and to the upper basin of Chu river(沮水), while the ribbed Oncomelania is widespread in the plain of the southeast portion of this province.A morphological study of Oncomelaniid snails from different localities in Hupeh province reveals that: (1) the shell characters of snails from one same area and from other areas are found to be very variable that may be the most important feature for separating species; (2) no distinct and valuable variations of the false "eye-brow", tentacles, mantle edge and nervous system are found; (3) the shell and head of ribbed Oncomelania are lighter-colored than those of smooth-shelled Oncomelania, both of them being under the influence of environment; (4) the verge's tip of male ribbed Oncomelania is colored rose (94.6％), light red (4.5％), and gray (0.9％), while that of smoothshelled Oncomelania is colored light red (75％), rose (19.44％), and gray brown(5.55％); (5) the radula denticle count which has often been regarded as one of the chief disti(?)uishing characters is sometimes found to be very variable from one snail to another and also within the same snail. We believe, therefore, that color of verge's tip and the radula denticle count are of no taxonomic significance.On the basis of internal morphological features, the taxonomic position of the various genera of this group has been discussed. The authors agree with the Annandale and Abbott to put the Schistosomophora Bartsch and Katayama Robson in the genus Oncomelania Gredler. On the basis of external morphological features, the classification for separating species has also been discussed. A short review is also made concerning the environment relating to the geographical distribution and morphology of the Oncomelaniid snails.