Report – ZL2103 – Grasshoppers

Grasshoppers

Abstract

We collected a wide range of grasshoppers of different body sizes to find the best morphological predictor of jump distance by measuring total body length, total, proximal and distal leg length and compared it to jump distance. Food consumption was measured through fecal production over seven days to find the best morphological predictor of food consumption.

We found a strong significant relationship between both proximal leg length vs. body length and jump distance vs. body length, thus the question was raised if there also was a relationship between proximal leg length and jump distance. We could not statistically find a significant relationship between proximal leg length and jump distance.

Introduction

The profound effects of body temperature on many aspects of physiology and behavior for ectothermic animals, such as reptiles and insects has been investigated many times (Bennet, 1980; Forsman, 1999; Gilchrist, 1996; Harrison et al., 1991; Huey & Hertz, 1984; Huey & Kingsolver, 1989; 1993; Willmer, 1991). The individual fitness may be influenced indirectly through effects on dispersal, foraging, mating success, escape capability and egg production by any factor that influence body temperature, such as weather conditions, body size and colour patterns (Forsman & Appelquist, 1998; Huey & Kingsolver, 1989; Hinks & Erlandson, 1994; Willmer, 1991).

Our study was to test if large grasshoppers jumped as long as small ones, and if there was any morphological body part that could be used as a predictor for jump distance as well as food consumption.

AIMS:

To find the best morphological predictor of jump distance

To find the best morphological predictor of food consumption.

Materials and Methods.

We conducted the study between 9.30am to 10.30am, the 24th of August 2000, behind the aquaculture research facilities at James Cook University, Townsville, in tropical north Queensland, (146.80 E, 19.30 S).

The grasshoppers were collected with nets and were put into collecting nets during two one-hour periods. When collecting just a certain amount of each size were captured so a large range of grasshopper body sizes were captured. The temperature ranged from 22° C in the morning hours to about 30° C in the afternoon.

Back in the laboratory we identified the grasshoppers, measured and recorded body length, proximal and distal leg length and the weight was also recorded.

After allowing sufficient time for the grasshoppers to adopt to laboratory temperatures (about 15min) we jumped the grasshoppers and recorded the mean jump distance out of three jumps.

All but 10 grasshoppers were released while the remaining grasshoppers were put into separate holding cages with a pot of grass and a moist sponge for drinking. Each day, for seven days, the holding cages was cleaned on fecal material which was weighed and recorded. On the seventh and last day the grasshoppers where weighed as well.

The recorded data were put trough regression and residual analysis using Microsoft Excel -98.

Results.

Figure 1. Best relationship between body size and various parts of the legs (proximal, distal and total leg length) was found to be between body length and proximal leg length, with a significance value of 4.18216 E-23). Even body mass vs. proximal leg length showed a high significance (1.1586 E-20) and R2 value (0.6070).

Figure 2. Best relationship between body size and fecal production was found to be with body mass (log) that even with very few data points indicates a linear relationship, with a R2-value = 0.7912. Even body length vs. mean fecal production (log) indicated a high R2-value (0.7121).

Figure 3. Best relationship between body size and jump distance was found to be with body mass (log) that indicates a significant linear relationship (P = 3.88 E-5, R2 = 0.2057). Body length vs. jump distance (log) indicated a non-significant value (P = 0.063, R2 = 0.0459).

Table 1 shows found R2 values and the significant levels for different relationships. BL = Body Length, DLL = Distal Leg Length, TLL = Total Leg Length, BM = Body Mass and JD = Jump Distance. The only value found not to be significant was the body length vs. jump distance (log).

Table 1 – Relationship Significance.

Relationships R 2 Significance
BL vs. DLL 0.5873 7.1600 E-16
BL vs. TLL 0.6895 1.7837 E-20
BM vs. DLL 0.4388 7.1569 E-11
BM vs. TLL 0.5437 3.1058 E-14
BL vs. JD (Log) 0.0459 0.0630

Table 2 indicates the fecal production of the five grasshoppers we kept over a weeks time. It also shows the mass of the grasshoppers before we put them into the cages and again after the week had past.

Table 2 – Average daily fecal production of grasshoppers.

Grasshopper number: 1 2 3 4 5 Fecal prod. mean / day
Day 1 0.004 0.109 0.1 0.071
SAT 0.002 0.002 0.108 0.226 0.0845
SUN 0.002 0.002 0.002 0.09 0.2 0.0592
MON 0.002 0.001 0.003 0.075 0.08 0.0322
TUE 0.002 0.001 0.008 0.009 0.009 0.0058
WED 0.004 0 0.011 0.021 0.086 0.0244
THU 0 0.01 0.011 0.019 0.01
Mean fecal prod. / grasshopper 0.0027 0.001 0.0068 0.0604 0.1029
Initial Mass 0.081 0.184 0.36 0.76 6.18
Final Mass 0.07 0.11 0.38 0.778 6.18
Average mass 0.0755 0.147 0.37 0.769 6.18

Discussion

We found that body length versus proximal leg length was the best predictor between body size and various parts of the legs (proximal, distal and total leg length) (Fig 1.), (P = 4.18 E-23, R2 = 0.7361). Even body mass vs. proximal leg length showed a high significance (P = 1.1586 E-20, R2 = 0.6070).

In terms of the fecal production we found even with very few data points a fair indication of a strong linear relationship between both mean body mass (log) versus mean fecal production (log) (R2 = 0.7912) (Fig 2.), and body length versus mean fecal production (log) (R2-value = 0.7121). This linear relationship indicates a strong relationship that the size of the grasshopper follows a trend, the larger body size the more fecal waste it produce. In this experiment it was assumed that fecal waste was equal to food intake so it can therefore be assumed that the larger grasshopper more it eats.

A significant relationship was not found between jump distance (log) and body length (R2-value = 0.0459) but, in contrast, we found a significant relationship, as did Forsman (1999), between jump distance and mean body mass (log) (R2-value = 0.2057) (Fig 3.). This tend to indicate a allometric relationship between body mass and jump performance i.e. that small grasshoppers jump the same distance as the larger grasshoppers relatively to their individual body mass. Because we found a strong significant relationship between both proximal leg length vs. body length and jump distance vs. body length we were curious if there also was a relationship between proximal leg length and jump distance. Thus, to find out if there is a relationship between jump distance and proximal leg length a plot of the residuals of ‘jump distance (log) vs. body length’ against the residuals of ‘proximal leg length vs. body length’ and found that there was no relationship (R2 = 0.001).

References

Bennet, A.F. (1980) The thermal dependence of muscle function. Animal Behaviour, 28: 752-762.

Forsman, A. (1999) Temperature influence on escape behavior in two species of pygmy grasshoppers. Ecoscience, 6(1): 35-40.

Forsman, A. & Appelquist, S. (1998) Visual predators impose correlation selection on prey colour pattern and behaviour. Behavioural Ecology, 9: 409-413.

Gilchrist, G.W. (1996) A quantitative genetic analysis of thermal sensitivity in the locomotor performance curve of Aphidus ervi. Evolution, 50: 1560-1572.

Harrison, J.F., Phillips, J.E. & Gleeson, T.T. (1991) Activity physiology of the two-striped grasshopper, Melanoplus bivittatus: Gas exchange, hemolymph acid-base status, lactate production and the effect of temperature. Physiological Zoology, 64: 451-472.

Hinks, C.F. & Erlandson, M.A. (1994) Rearing grasshoppers and locusts: Review, rationale and update. Journal of Orthopteran Research, 3: 1-10.

Huey, R.B. & Hertz, P.E. (1984) Is a jack-of-all temperatures a master of none? Evolution, 38: 441-444.

Huey, R.B. & Kingsolver, J.G. (1989) Evolution of thermal sensitivity of ectotherm performance. Trends in Ecology and Evolution, 4: 131-135.

Huey, R.B. & Kingsolver, J.G. (1993) Evolution of resistance to high temperatures in ectotherms. American Naturalist, 42: 21-46.

Willmer, P.G. (1991) Thermal biology and mate acquisition in ectotherms. Trends in Ecology and Evolution, 6: 396-399

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