Morphological abnormalities in caddisfly larvae (Hydropsyche doctersi) as indicator of water quality in tropical rivers

Fluctuating asymmetry (FA) of Hydropsyche doctersi (Trichoptera: Hydropsychidae) and its relationship with physico-chemical parameters of four rivers, Kurau River and Ara River in Perak while Kob River and Sedim River in Kedah, Malaysia were studied. All investigated rivers experienced good water quality (Class II) according to water quality index (WQI), although the rivers were surrounded by different land uses. However, high values of BOD, COD and TSS of Kob River indicated that the river was highly polluted. The influence of several physicochemical parameters on H. doctersi anatomical structures such as 1st tarsal claw length, 1st tarsal length, 1st tibial length, 1st tibial width, 2nd tibial length, 2nd tibial width, 2nd femur length, 3rd tibial length, 3rd tibial width, 3rd femur length, 3rd trochanter length, mesonotum length and anal claw length were also investigated. However, only four structures (2nd tibial length, TBL and 3rd tibial width, TBW) exhibited FA in H. doctersi samples from the rivers and were further analyzed. Results revealed that the greatest numbers of traits exhibited FA was recorded at Ara River with eight traits and the greatest FA11 was recorded in third femur length, meanwhile only three traits exhibited FA in Kurau River. In 3rd TBW, AbsFA and FA index showed correlation with nitrate concentration in the rivers. The FA incidence was also reported in the 1st TBL based on correlation of AbsFA with temperature, TDS and orthophosphate. As a conclusion, FA occurrence at Hydropsyche doctersi has proved that river pollution contributed to deformities among the aquatic organisms.