Study on predatory effect of Ischnura heterosticta larvae on Misgurnus anguillicaudatus larvae

To investigate the influence of the predator, Ischnura heterosticta larvae on survival rate of Misgurnus anguillicaudatus larvae, we studied the predatory effect of I. heterosticta larvae on M. anguillicaudatus larva based on the predator-prey relationship theory. Results of experiments showed that:the predation functional response of I. heterosticta larvae to M. anguillicaudatus larvae belonged to type Holling-Ⅱ. With the increase in daily age of M. anguillicaudatus larvae, the moment attack (a') and the largest preying amount per day (1/T_h) declined. The preying amount increased as prey density increased. The predatory function of different sizes of I. heterosticta larva to M. anguillicaudatus larva had significant differences. For I. heterosticta larvae with different body lengths (16.3±0.2), (13.1±0.3), (9.8±0.2) and (5.8±0.3) mm to 3-day-age larvae of M. anguillicaudatus, the moment attack and the largest preying amount per day were 0.8349, 0.5724, 0.2002, 0.0432, and 27.39, 18.99, 9.49, 3.14, respectively. With the density of I. heterosticta larvae increased, the mutual interference between the individuals led to reduction in the time of a single I. heterosticta larva looking for prey. Under intraspecific competition, predatory effect rate (E) as a function of density (P) was E=0.1403×P^-0.2361. With the increase of M. anguillicaudatus larvae and I. heterosticta larvae density, interference effect increases obviously, predatory efficiency rate (E) drops, but had little impact on preying amount, and the model of interspecific interference was Na=(0.7841×P^-0.1560×N)/(1+0.0305×N). The results demonstrated that I. heterosticta larva is important predator, which can remarkably reduce the survival rate of M. anguillicaudatus larvae.