The abundance, distribution and diversity of invasive and indigenous freshwater snails in a section of the Ogunpa River, southwest Nigeria

This study investigated the abundance, distribution and diversity of freshwater snails at four sites in the Ogunpa River, Nigeria from May 2018 to December 2018. A total of 2067 freshwater snails was collected, belonging to two sub-classes, four families, and seven species: <i>Physella acuta, Amerianna carinata</i>, <i>Melanoides tuberculata</i>, <i>Physa waterloti</i>, <i>Bulinus globosus</i>, <i>Bulinus senegalensis</i>, and <i>Lymnaea natalensis</i>. Invasive freshwater snails (82.15%) were more abundant than indigenous species (17.85%). <i>Physella acuta</i> (30.05%) and <i>P. waterloti</i> (20.61%) were the most abundant species, while <i>B. globosus</i> (4.35%) and <i>B. senegalensis</i> (3.92%) were the least abundant. The presence of <i>P. acuta</i>, <i>B. globosus</i>, <i>B. senegalensis</i>, and <i>M. tuberculata</i> constitute potential economic and health risks to animals and humans in contact with this waterbody. Freshwater snail numbers showed variation among sites, seasons, and site-season interactions. Water depth, turbidity, and pH correlated significantly with the numbers of freshwater snails, except that pH did not correlate with <i>P. waterloti.</i> There were strong positive correlations between the numbers of molluscs and the abundance of <i>Commelina diffusa</i>, <i>Amaranthus spinosus</i>, <i>Murdannia nudiflora</i>, and <i>Ipomoea aquatica</i>. Stepwise multiple regression showed that water depth, <i>C. diffusa</i>, and <i>Sacciolepis africana</i> were the primary variables affecting snail distribution and abundance in the Ogunpa River.