The ITS2 of the genus Bulinus: Novel secondary structure among freshwater snails and potential new taxonomic markers

▶ We have predicted the putative secondary structures of ITS2 in Bulinus. ▶ The B. reticulatus group possesses an additional large helix (DIIa) in ITS2. ▶ We have investigated the presence of compensatory base changes in ITS2 in Bulinus. ▶ CBCs might be a new tool in the investigation of Bulinus. ▶ The taxonomic ambiguities within Bulinus remain.

The freshwater snail genus Bulinus has been intensively investigated due to its role as intermediate host for trematode blood flukes that cause the debilitating disease schistosomiasis in man and livestock. Owing to taxonomic ambiguities within Bulinus, attention has often focused upon species delineation and several molecular methods have recently been used for identification and characterization purposes. Inspection of compensatory base changes (CBCs) in the secondary structure of the nuclear ribosomal internal transcribed spacer (ITS) has been used to differentiate species in other genera, and here we present a study investigating the presence of CBCs between species in the species groups within Bulinus. CBCs were present within B. forskalii and B. globosus indicating that these widely distributed taxa might constitute cryptic species complexes. However, other currently recognized species could not be distinguished by CBC analysis. The putative secondary structure of the very long ITS2 sequence of the B. reticulatus species group had an additional helix (DIIa) between DII and DIII not seen in other species groups of Bulinus. The accumulation and inspection of further ITS2 sequences will no doubt reveal additional variation between Bulinus populations, and CBCs should be incorporated in future taxonomic work in this group.

CBC analysis represents an additional tool in the arsenal of the taxonomist and might be able to assist in solving the taxonomic ambiguities within the genus.Figure optionsDownload as PowerPoint slide