膀胱螺属中的某些种是埃及血吸虫的中间宿主,而另一些种则不感染埃及血吸虫。非洲撒哈拉沙漠以北和中东的埃及血吸虫的螺蛳媒介是截形膀胱螺(Bulinus truncatus),一种四倍体螺种,有72个染色体,在减数分裂时形成36个二倍体。四倍体膀胱螺也见于撒哈拉以南的埃塞俄比亚、肯尼亚、坦桑尼亚、加纳等国。它们的亲缘种热带膀胱螺 Certain species of the genus Blachia are intermediate hosts of S. schistosomes, while others do not infect S. schistosomes. The snail medium for S. japonicum in northern and sub-Saharan Africa is the Bulinus truncatus, a tetraploid spheroid with 72 chromosomes and 36 diploids at meiosis. Tetraploid bladder snails are also found in sub-Saharan Ethiopia, Kenya, Tanzania, Ghana and other countries. Their kinship is tropical cyst