Camp. B&hem. Physiol., 1971, Vol. 38A, pp. 449 to 455. Pergamon Prers. Printed in Great Britain

ENERGY BALANCE IN PERIPLANETA AMERICANA L.

PREMA MICHAEL

Department of Biological Sciences, Madurai University, Madurai, S. India

(fieceizred 3 April 1970)

Abstract-l. Energy extraction and conversion efficiencies were investigated at 20”, 29” and 35°C with protein and carbohydrate diets in Periplaneta americana L.

2. Energy extraction efficiency was found to be independent of temperature and sex, but was dependent on quantity of food below a critical food level of 90 mg/g animal per day.

3. Conversion efficiency was temperature and food dependent. 4. While carbohydrate conversion showed positive relation to food input, a

negative relationship was recorded for protein conversion.

INTRODUCTION

ENERGY metabolism is involved in every body function and the study of it contri- butes to our knowledge of animal nutrition. A good deal of work has been done in the field of energy metabolism on farm animals (Maynard & Loosli, 1956) and lower vertebrates like fish (Ivlev, 1939a, b, c; Gerking, 1952; Job, 1960; Kinne, 1960; Davies, 1964; Mercy, 1967; Pandian, 1967a, b, c). Our knowledge on the energy relationships in invertebrates have been mainly through the works of Ivlev (1939d), T rama (1957) Richman (1958) Slobodkin and Richman (1961) and Paine (1965). However, it appears that relatively few studies have been made on the energy relationships in insects. The aim of the present work therefore was to investigate the energy exchanges in the common cockroach P~~pl~net~ americana at different temperatures using different nutrients with a view to draw up energy balance sheets and to determine whether acclimation to different temperature and nutrients has any energetic significance.

MATERIALS AND METHODS

Experimental animals were collected from underground sewage pipes. These were segregated sexwise and reared in wide-mouthed glass bottles. The test animals were set up in groups of l-4 animals so as to accumulate enough faecal pellets for caloric determinations. This grouping also served to even out individual variations as far as possible in those meta- bolic activities which are influenced by age, body weight and feeding rates. The average,dry weight of males and females were 0*3005 and 0.3849 g respectively. The duration of feeding varied from 4 to 8 days for these animals. Experiments were conducted at three different temperature Ievels of 20”, 29” and 35°C. At 20°C the animals were reared in an incubator, with a fluctuation of 1 “C.

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450 PREMA MICHAEL

Both carbohydrate (dried bread) and protein (dried lean meat) nutrients were given for the test animals at room temperature (29°C). Only carbohydrates were used in experiments at the other two temperature levels. The animals were always fed to repletion as the food was constantly made available to them. At the end of the experiment, the animals were dried to constant weight at 70°C. The faeces which were expelled both as pellets and smears were washed out with a small quantity of distilled water into small petri dishes of 2 in. diameter and then dried to constant weight at 70°C. An electrobalance having a sensitivity of O*OOOl g was used for all measurements of weights. For caloric determinations wet combustion method was employed as described by Karzinkin and Tarkovskaya (1964). Energy extraction efficiency (e.e.e.) and conversion efficiency (c.e.) were worked out following the equations given by Davies (1964).

Energy wasted Energy input = in faeces and -i- Energy lost as heat + Energy stored (1)

urine (A) @I 0 (0

Energy extraction efficiency (e.e.e.) may be calculated from the relation described in equation (1) :

(A-B)x 100 e.e.e. = - A *

Conversion efficiency (c.e.) may be calculated from the following equation derived from (1):

c.e. = % X 100. (3)

RESULTS

E.e.e. in negation to food uptake and n~tri~ts

A maximum of 99.67 per cent extraction efficiency occurred with a maximal carbohydrate food intake of 386.2 mg/g animal per day. The corresponding minimal values were 35.13 per cent with S-4 mgjg animal per day. The average efficiency with carbohydrate diet for females was 92.3 and 85.7 per cent for males.

E.e.e. in relation to temperature and nutrients

The highest extraction efficiency of 99.7 per cent with carbohydrate food occurred at 35°C. The average extraction efficiency with the same diet at 20, 29 and 35°C were 87.13, 94.04 and 95.42 per cent of food input per g animal per day respectively for the females and 8.5*94, 78.27 and 92.70 per cent for the males in that order of temperature. With protein food at room temperature, the efficiencies of females and males were 85.08 and 82.66 per cent respectively.

C.e. in relation to rate offood intake and nutrients

Average efficiencies in females were 68.32 per cent of food intake. Corres- ponding value for males was 4679 per cent. Regression coefficients with carbo- hydrate diets were Y = 0*0872X+ 1.5699. With protein food the percentage conversion values for females and males were 22.85 and 18.51 respectively. Regres- sion coefficient was Y = -0*3084X+ 1.9190 (Fig. 3).

451

Conversion efficiencies of the cockroaches at 20°C could not be calculated. At 29 and 35°C the efficiency was 68.34 and 6820 per cent of food input/g animal per day for females and corresponding values for males were 44.56 and 49.02 per cent. At 29°C with protein food the efficiency recorded for females and males were 22.85 and 18.5 1 per cent of food input/g animal per day.

Rate offood intake in relation to nutrients and temperature

The carbohydrate consumption of females at the three temperatures (20,29 and 35°C) ranged between a maximum of 157.9, 197.6 and 3862 mg/g animal per day to a minimum of 55.0, 88.7 and 119.2 mg/g animal per day dry weight respectively. corresponding values for the males were 168.2, 180.5 and 230.7 and 57*0,42+2 and 112.0 mg/g animal per day. Intake of protein food ranged between a m~imum of 212.4 mg/g animal per day and a minimum of 40.6 mg/g animal per day for the females and the corresponding range for males was between 161.6 and 14.7 mgjg animal per day. The rate of increase in food intake/g animal per day for females and males from 20” to 35°C was 88.7 and 78.3 per cent respectively.

DISCUSSION

In adult cockroaches the energy extraction efficiency is temperature independ- ent and quite high at all the three temperatures (ZOO, 29” and 35°C). This tempera- ture independence of e.e.e. in these animals may account for their successful world- wide distribution. There is also no difference in the performance of the two sexes in this function, thus establishing independence to these factors. However, extraction efficiency is dependent on the quantity of food. Consistently high e.e.e. is recorded with large quantities of food (Fig. 1). Studies on the energy transformations in other poikiiothe~s show that with increased food intake, the extraction efficiency falls (Ivlev, 1939~; Gerking, 1952; Richman, 1958; Kinne, 1960). The high

mg food intake/g animal per day

Fro. 1. Energy extraction efficiency of P. americana L. with carbohydrate diet at different temperatures. Data from Davies (1964) is superimposed for purposes of

comparison.

452 PREMA ~L~ICHAEL

extraction efficiency with large food input in the present study is comparable to that recorded in goldfish (Davies, 1964). However, even in this cockroach, fall in e.e.e. occurs, but only below the critical level of 90 mg/g animal per day of food (dry weight) supplied. This holds good for only 20 and 29°C. At the highest experimental temperature of 35°C however, the e.e.e. is uniformly high probably due to increased metabolic rate and activity leading to increased food intake, being the direct effect of temperature. This seems to imply, that at normal and lower levels of temperature, a particular range of food is necessary to permit the cock- roaches to extract the energy necessary just for maintenance. Below the critical level of 90 mg/g animal per day the cockroaches become less efficient in energy extraction.

Energy extraction efficiency is independent of the type of food as there is no significant difference in the e.e.e. with either starch or proteinaceous food (Fig. 2). However, with protein food there is a wider variation in the amount consumed since it is not utilized directly for adding more body tissue, these being adults with no further growth. Proteins are known to be degraded only in the absence of other energy producing reserves and when the demand for addition of new tissue is not exacting. It is not surprising therefore that the utilization of protein (84.33 per cent) in the present study is less than that of carbohydrates (91.86 per cent).

I I

120 240

mg food Intake/g animal per day

FIG. 2. Energy extraction efficiency of P. americana L. with protein and carbo- hydrate diets at 29°C.

Conversion efficiency in these cockroaches is low, due to lack of growth. Unlike e.e.e., c.e. is temperature dependent. Low temperature (20°C) lowers the efficiency due to a fall in the metabolic activities. It is also sex dependent. Females are better converters because of greater energy demands for their pronounced reproductive activities. In P. americana, c.e. is dependent upon the type of nutrients supplied. Conversion efficiency with carbohydrate food is high when compared with that of proteins. The inability of P. americana to convert the bulk of proteins is evident from Fig. 3 where the conversion efficiency with protein food shows a negative relationship. This clearly substantiates the view that though

ENERGY BALANCE IN PERIFLANETA AMERICANA L.

IOOr

50-

LAi ci .9

10 -

5- If

0 0

0 !3

00 _n_.---‘-‘

Carbohydrate _.C.--

D 0 0 0

Protein

-ttc,

5 d

I I I t 50 100 500

mg food intokelg onimol per doy

FIG. 3. Conversion efficiency of P. americana L. with protein and carbohydrate diets at 29%

Temperature, OC

FIG. 4. Rate of carbohydrate food intake in male and female P. americama L. at different temperatures.

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domestic cockroaches are omnivorous, they have a partiality for sugary and starchy food (Imms, 1963). The poor conversion of protein is probably because there is not that great need to utilize protein for growth.

The rate of food intake is a function of temperature, there being an increase of 83.5 per cent in food consumption from the lowest (ZO’C) to the highest (35°C) experimental temperatures (Fig. 4). The adult females apparently consume more than the males and the difference is most significant at 29°C.

Acknowledgements-1 am extremely grateful to Dr. S. V. Job, Department of Biological Sciences, Madurai University for suggesting this problem and guidance in this work. I also

wish to express my gratitude to Professor S. Krishnasamy, Department of Biological

Sciences, Madurai University for his keen interest in this work. This work was carried out as a partial fulfilment for the award of the M. Phil. degree in Madurai University, S. India.

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291.

ENERGY BALANCE IN PERIPLANETA AMERICANA L. 455

SLOBODKIN L. B. & RICHMAN S. (1961) Calories/gm in species of animals. Nature, Lond. 191,299.

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Key Word Index-Insect; Periplaneta americana L. ; energy metabolism ; energy extrac- tion efficiency; conversion efficiency; effect of diet and temperature.