Predation Experiment of Dragonfly Nymphs and Poecilia reticulata

The predation experiment of dragonfly nymphs towards mosquito larvae species with variation in number of predator, water volume and number of predators were presented in Figures 8.11 – 8.13. To investigate the efficiency of predatory of the selected 3 species of dragonfly nymph on 3 species of mosquito larvae, 3 types of variable were introduced: (i) the predator number was either 1 or 2, (ii) the water volume was either 1 or 2 liters and (iii) the prey density was either 100 or 200 in number of individuals. Three Odonata species were used in this experiment, they were N. fluctuans, O. sabina and O.

chrysis as a predator and three mosquito larvae species as a prey: Ae. albopictus, Ae.

aegypti and Cx. quinquefasciatus larvae.

Overall, the 3 species of dragonfly nymphs were consumed higher number of mosquito larvae in 2 conditions which is in (2 predators× 1 liter of water ×100 mosquito density) and in (1 predator × 1 liter of water × 200 mosquito density). However, dragonfly nymphs were consumed small number of mosquito larvae when exposed in 2 liters of water volume.

151 Figure 8.11 Variations in daily feeding rate of three Odonata nymph species on the fourth-instar Aedes albopictus larvae with variation in prey density, water volume and number of predator

Figure 8.12 Variations in daily feeding rate of three Odonate nymph species on the fourth-instar Aedes aegypti larvae with variation in prey density, water volume and number of predator

152 Figure 8.13 Variations in daily feeding rate of three Odonate nymph species on fourth-instar Cx. quinquefasciatus larvae with variation in prey density, water volume and number of predator

153 The predation experiment also observed in male and female guppy towards three species of mosquito larvae (Figures 8.14 – 8.16). In all three experiments it showed that female guppy consumed higher number of mosquito larvae than male guppy except in one condition when male guppy consumed more larvae of Cx. quinquefasciatus larvae in (2 predators × 1 liter of water × 200 mosquito density).

Female guppy consumed high number of mosquito larvae in (1 predator × 1 liter of water × 200 mosquito density) of Ae. albopictus, Ae. aegypti and Cx. quinquefasciatus larvae (Figures 8.14 – 8.16).

Male guppy consumed high number of mosquito larvae in different condition for example they consumed more Ae. albopictus and Cx. quinquefasciatus larvae in (2 predators × 1 liter of water × 100 mosquito density) but they consumed more Ae. aegypti larvae (1 predator × 1 liter of water × 200 mosquito density). In all three experiments, both male and female guppies consumed small number of mosquito larvae when exposed with (1 predator × 2 liter of water × 100 mosquito density), where the water volume was increased.

154 Figure 8.14 Variations in daily feeding rate of male and female guppies on

fourth-instar Aedes albopictus larvae with variation in prey density, water volume and number of predator

Figure 8.15 Variations in daily feeding rate of male and female guppies on fourth-instar Aedes aegypti larvae with variation in prey density, water volume and number of predator

155 Figure 8.16 Variations in daily feeding rate of male and female guppies on

fourth-instar Cx. quinquefasciatus larvae with variation in prey density, water volume and number of predator

156 Table 8.7 shows the regression equations provided by multiple regression analyses for predation on Ae. albopictus larvae by Odonata species. From the regression equation, it was observed that factors such as number of predator, water volume and prey density influenced the feeding consumption of Odonata species. For N. fluctuans prey density was significantly affected the predation activities. The feeding rate of N. fluctuans was higher when the prey density was low than when the prey density was high. The factor that influences predation activities for O. sabina was water volume. Its show negative relationship between feeding consumption and water volume; the feeding rate decreased with increased water volume. The feeding rate of O. chrysis increased when the number of predator increased.

Multiple regression analyses for predation of Ae. aegypti larvae by odonate species have been depicted in Table 8.8. Only water volume and prey density were influenced the predation activities. For N. fluctuans and O. chrysis the prey density was influenced the predation activity. The feeding rate was higher when the prey density was low than when the prey density was high. Water volume influenced the predation activities of O. chrysis.

The O. chrysis eat more larvae during water volume decreased.

Three factors such as number of predator (X1), water volume (X2) and prey density (X3) were influenced the predation activities(Table 8.9). For N. fluctuans, water volume was influenced the predation activities. Two factors influenced predation activities between O. sabina and Cx. quinquefasciatus larvae. When the number of predator increased the feeding rate also increased and they eat less when number of prey increased. However, for O. chrysis only one factor influenced the predation activity which is prey density.

157 Table 8.7 The regression equations of predation on Aedes albopictus larvae by different Odonate nymphs (Y) against the number of predator (X1), water volume (X2) and prey density (X3) as variables

Predators (Odonata species)

Regression equations R value

Neurothemis fluctuans Y = 96.444 – 31.556 X3 0.88 Orthetrum sabina Y = 106.111 – 35.889 X2 0.75 Orthetrum chrysis Y =11.444 – 26.44 X1 0.78

Table 8.8 The regression equations of predation on Aedes aegypti larvae by different Odonate nymphs (Y) against the number of predator (X1), water volume (X2) and prey density (X3) as variables

Predators (Odonata species) Regression equations R value Neurothemis fluctuans Y = 109.667 – 36.667 X3 0.87 Orthetrum sabina Y = 115.778 – 38.556 X2 0.78 Orthetrum chrysis Y = 84.222 – 22.778 X3 0.61

Table 8.9 The regression equations of predation on Cx. quinquefasciatus larvae by different Odonate nymphs (Y) against the number of predator (X1), water volume (X2) and prey density (X3) as variables

Predators (Odonata species)

Regression equations R value

Neurothemis fluctuans Y = 77.000 – 25.000 X2 0.84 Orthetrum sabina Y = 35.667+ 36.00 X1– 20.333 X3 0.89

Orthetrum chrysis Y = 114.000 – 35.667 X3 0.79

158 Table 8.10 shows the regression equations provided by multiple regression analyses for predation on Ae. albopictus larvae by male and female guppies. From the regression equation, it was observed that factors such as number of predator, and water volume influenced the feeding consumption of male guppy. Whereas for the female guppy only water volume significantly affected the predation activities. It showed negative relationship between feeding consumption and water volume; the feeding rate decreased with increased water volume. The feeding consumption increased when the numbers of predator increased.

Multiple regression analyses for predation of Ae. aegypti larvae by guppies have been depicted in Table 8.11. Only water volume and prey density influenced the predation activities. The feeding rate was higher when the prey density increases and feeding rate increases when water volume decreases.

Table 8.12 showed the factors that influenced the predation of both male and female guppies towards Cx. quinquefasciatus larvae. When the number of predator increased the feeding rate also increased and feeding rate decreased when search area was increased (water volume increased).

159 Table 8.10 The regression equations of predation on Aedes albopictus larvae by male and female guppy (Y) against the number of predator (X1), water volume (X2) and prey density (X3) as variables

Predators Regression equations R value

Male guppy Y = 16.67 + 48.67 X1 – 14.00 X2

0.99

Female guppy Y = 119.67 – 23.33 X2 0.66

Table 8.11 The regression equations of predation on Ae. aegypti larvae by male and female guppy (Y) against the number of predator (X1), water volume (X2) and prey density (X3) as variables

Predators Regression equations R value

Male guppy Y = 125.33 – 32.67 X2 0.75

Female guppy Y = 92.00 – 15.00 X2 + 23.00 X3 0.96

Table 8.12 The regression equations of predation on Cx. quinquefasciatus larvae by male and female guppy (Y) against the number of predator (X1), water volume (X2) and prey density (X3) as variables

Predators Regression equations R value

Male guppy Y = – 13.33 + 56.67 X1 0.92

Female guppy Y = 105.67– 20.33 X2 0.67

160

CHAPTER 9