Caudal bending was noticed in both the toxicant
concentrations with time and persisted even under
recovery periods, which greatly retarded the normal
swimming pattern. The extent of caudal bending was
pronounced in the highest toxicant concentration
(1/7th of 96 h LC50). Caudal bending may be a sort of
paralysis, which might be due to the inhibition of
muscular AChE activity resulting in blockage of
neural transmissions. This produces rapid twitching of
voluntary muscles followed by paralysis (Ware, 1989;
Habig and DiGiulio, 1991). Bending of caudal base is
owing to the fact that caudal portion is the thinnest
structure and hence can be conferred any sort of
orientation due to paralysis of caudal musculature
because of AChE activity inhibition. Thus,
chlorpyrifos reduced instinctive behavioural
responses and affected morphological features.