Aquatic macroinvertebrates of Nee Soon 
97 
Fig. 16. Distribution and abundance of order Basommatophora in the Nee Soon drainage. Solid 
circles indicate sites where representatives were collected and circle sizes are proportionate to 
abundance/numbers of individuals captured as reflected in the accompanying legend. 
Order Mesogastropoda 
The gastropods of the order Mesogastropoda possess gills which are directly attached 
to the mantle wall, as well as an operculum, features which the Basommatophora 
lack (Ruppert & Barnes, 1994). Representatives from two families from this order - 
Assimineidae and Thiaridae were found in the Nee Soon drainage, but again only in 
the northeast areas and nowhere else within the Nee Soon freshwater swamp forest. 
Snails from the family Thiaridae were the most commonly recorded, with 19 and 87 
individuals recorded at sites 31 and 32 respectively, while only one Assimineidae 
individual was recorded at site 40 (Fig. 17). 
