Biomphalaria kuhniana (Clessin, 1883), planorbid mollusc from South America

the validity of biomphalaria kuhniana (clessin, 1883) is confirmed through morphological study of specimens from surinam (type locality) and the area of tucurui (tocantins river, state of pará, brazil) in comparison with b. straminea (dunker, 1848), and throught crossing experiments which revealed complete reproductive isolation between the two species. the full-grown shell of kuhniana is smaller (about 7.5 mm) than that of straminea (11 mm to 16.5 mm). anatomically they differ in the degree of corrugation of the vaginal wall (little developed in kuhniana, conspicuous in straminea), number and shape of prostatic diverticula (kuhniana 4 to 9, shorter and less branched; straminea 9 to 18, longer and more branched),number of muscle layers at the middle of the penis (two in kuhniana, three in straminea), distal segment of the spermiduct usually straight or slightly wavy in kuhniana, more or less curly in straminea. differences between b. kuhniana and b. intermedia (paraense & deslandes, 1962) are less marked. the latter has a shell up to about 12 mm in diameter, 7 to 15 prostatic diverticula, two muscle layers at the middle of the penis, and a vaginal wall with a combination of a more or less developed corrugation (or sometimes a mere swelling) on the left of the spermathecal duct and a rudimentary pouch on the right of the duct. a biomphalaria straminea complex is proposed to include that species as well as b. kuhniana and b. intermedia.