Effect of temperature on food utilization, growth and egg production in the spider Cyrtophora cicatrosa

J. therm. Biol. Vol. 10. No. 2, pp. 63-70, 1985 Printed in Great Britain. All rights reserved

0306-4565/85 53.00 + 0.00 Copyright ~ 1985 Pergamon Press Ltd

EFFECT OF TEMPERATURE ON FOOD UTILIZATION, GROWTH AND EGG PRODUCTION IN THE SPIDER C Y R T O P H O R A CICATROSA S. PALANICHAMY

P.G. and Research Department of Zoology, A.P.A. College of Arts and Culture, Palani 624 602, Tamil Nadu, India (Received 30 August 1984; accepted in ret, ised form 23 January 1985)

Abstract--l. Effects of temperature on food utilization, growth and egg production were investigated in the spider C. cicatrosa. 2. The rise in temperature at 22, 27, 32 and 37~C. respectively, resulted in a telescoping of the life span in C. cicatrosa. 3. Almost all chosen parameters of food utilization and egg production displayed a positive relation with increasing temperature up to 32°C. A temperature of 37"C appears to be extreme. 4. Temperature fails to significantly alter the efficiency of energy utilization, conversion and egg production. 5. Temperature reduced total egg production, primarily affecting the adult period; but egg production/day increased with increasing temperature. Key Word Index--Temperature; growth; food utilization; egg production; mortality; life span; Cyrtophora cicatrosa; instar; energy extraction efficiency; conversion efficiency; feeding rate; interoviposition period; egg sac; egg number.

males much smaller than females (Palanichamy, 1980). The egg sacs of C. cicatrosa were collected from the field and incubated until hatching. Feeding experiments were commenced in freshly hatched second instar and continued until death. On maturity, females were mated with males. C. cicatrosa were reared individually in transparent plastic terraria. The spiderlings were reared in smaller containers (5 x 4 cm) and subadults and adults were grown in large terraria (10 x 7.5 cm). The methods described in Palanichamy (1984a) were adopted in the investigation. To study the food utilization, experimental individuals were fed ad libitum on freshly emerged Culex fatigans cultured in the laboratory at 27°C and 10 h/day light cycle. Individuals were fed daily in each instar/interoviposition and maintained at 22, 27, 32 and 37°C in B.O.D. incubators. The spider, exuvia, eggs, silk used to construct the egg sac, food and uneaten prey remains were weighed in a single pan balance (Mechaniki model) to an accuracy of 10 #g. The energy content (in joules) of the above materials was also determined in a semi° microbomb calorimeter (Parr Instrument Co.). Water content was estimated by weighing the test materials before and after drying at 90°C to weight constancy (Palanichamy and Pandian, 1983). The scheme of energy balance followed in this work is that of the modified form of the original I.B.P. formula (Petrusewicz and MacFadyen, 1970). Rates of feeding and conversion were calculated relating the amounts (J) of food energy consumed and converted to per unit live weight (g) of the spider per unit time (day). Metabolic rate (J/g.day) was calculated by subtracting the conversion rate (Pr) from the feeding rate (Cr).

INTRODUCTION

Spiders are important predators in terrestrial habitats. They can play a dominant role, as the insects constitute the principal prey (Turnbull, 1973), yet relatively little is known about the ecophysiological aspects of spiders. As growth and feeding of arachnids are usually temperature dependent, the effects of temperature on the metabolism and growth of each species must be investigated. Reports on the effects of temperature pertaining to food utilization of spiders are meagre (Jones, 1941; Hagstrum, 1970; Moulder and Reichle, 1972). Recently, Workman (1978) evaluated the individual energy budget of the temperate spider Trochosa terricola under constant and fluctuating temperature conditions. Prakash (1979) has studied the effects of temperature on the wandering tropical spider Pardosa birmanica and P. leucopalpis. Surprisingly, little is known about the effects of temperature on food utilization and egg production in spiders. However, studies on egg production in the field (Kessler, 1973; Anderson, 1978; Eberhard, 1979; Wise, 1979; Palanichamy, 1984b) as well as in the laboratory (Kessler, 1971; Valerio, 1976; Palanichamy, 1984a; Palanichamy and Baranikumar, 1984) are available. The present investigation reports the effects of temperature on food consumption, growth and egg production in the web-building spider Cyrtophora cicatrosa Stoliczka. MATERIALS AND METHODS

C. cicatrosa inhabits fences in the Palani region (10°23'N and 77°31'E) of India. It is dimorphic with t B

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S. PALANICHAMY

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AGE (doys) Fig. I. G r o w t h p a t t e r n o f C. cicatrosa females, as a f u n c t i o n o f age, fed ad libitum at different t e m p e r a t u r e s . R o m a n n u m e r a l s a d j a c e n t to the lines r e p r e s e n t the instar n u m b e r a n d the a r a b i c n u m e r a l s , the o v i p o s i t i o n f r e q u e n c y . F o r the sake o f clarity, d e v i a t i o n s are not s h o w n .

Conversion efficiency is expressed as the percentage of food converted in relation to food consumption. The amount of food ingested in relation to prey killed is considered as energy extraction efficiency (Palanichamy, 1980; Palanichamy and Baranikumar, 1984; Palanichamy, 1984a). Egg production efficiency was calculated by relating the eggs to consumption.

RESULTS

Food consumption and growth

The effects of temperature on mortality at different life stages of C. cicatrosa are presented in Table 1. The highest mortality was recorded in the individual at 37~C (93%), whereas it was lowest at 27 (80%) and 32~C (83%) when compared to the above.

Table 1. Effect of temperature on cumulative mortality (%) at different life stages of C. cwatrosa Temperature ( C ) Life stage

22

27

32

37

It II1 IV V VI VII VIII IX Adult Adult

48 57 64 72 72 79 81 81 80 85

48 56 59 63 76 76 80 80 80 80

53 53 58 65 68 75 75 78 80 83

58 68 75 80 80 90 90 90 92 93

The growth of C. cicatrosa is significantly influenced by temperature (Table 2). For instance, one female grew from 0.8 to 247J at the time of maturity in 76 days at 3 2 C , but a male attained only 59.5 J at the same temperature in 47 days (Table 3). In either sex, adults failed to display significant growth at any tested temperature. At all tested temperatures, adult females exhibited oscillation in growth (Fig. 1). The life span of C. cicatrosa is temperature dependent; it fell with increasing temperature. In one female it decreased from 375 days at 22 C to 180 days at 32:'C and then 89 days at 37C. Life span was shorter in males than in females. Temperature markedly influenced the duration of nymphal and adult stages. For example, at 22'C the duration of the nymphal or adult period of a female was the longest (218 or 157 days), but at 37"C they were shortest periods (69 or 22 days) (Tables 3 and 4). The magnitude of the reduction in life span with a change in temperature was of higher order in the adult than nymphal period, suggesting that the adults are more sensitive to thermal changes than the nymphs. Total food consumption of nymphal C. cicatrosa markedly increased from 22 to 32'C, but rapidly fell at 37"C. An analysis of total food consumption by an adult female showed that it is a temperaturedependent function (Table 4). At 2 2 C , a female consumed food equivalent to 2391 J in 157 days, whereas the 32"C it consumed 2742 J in 104 days. These values may be compared with those observed for the individual at 37'C, i.e. food consumption

Table 2. Bioenergetics of C. cicatrosa fed ad libitum on C. fatigans at different temperatures 22/C 27"C 32 C 37 C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Parameter Life span Food consumed (J.,spider} Energy extraction efficiency C.,) Food converted (growth, egg and silk) (J/spider) Metabolized (J/spider) Conversion effÉciency (K,) (",) Feeding rate (J/g.day) Conversion rate (J/g.day) Each value represents the average of about 6 individuals.

~

3

;

3

~

375 2940 73 958 1982 33 1017 218

185 243 72 23 22(1 9 1352 100

231 4244 75 942 3302 22 12t4 343

83 285 70 36 249 13 17(14 209

180 3672 7"~ 1048 2624 28 1499 414

;

64 525 77 59 466 1I 2085 26(I

:

89 1035 79 295 740 27 1829 452

53 127 75 16 11 I 13 1984 226

Effect o f t e m p e r a t u r e o n g r o w t h a n d m e t a b o l i s m in spiders

65

Table 3. Food utilization of C. cicatrosa fed ad libitum on C. fatigans at 22. 27, 32 and 37~C lnstar number

n

Duration (day)

Consumption (J)

Production (J)

Respiration (J)

II II1 IV V VI VII VIII IX Total nymph Total nymph Total adult

~ ~ ~" ~ ~ ~ ~ ~ '; 3 ,:7

3 :~ 3 S ,~

21 19 16 13 13 9 8 8

28_-+5.3 29_+3.6 274.3.1 254.4.9 35 4. 4.8 264.2.2 23 _ 3.7 25 4. 3.6 218 + 31.2 144+21.7 41 _+ 6.4

22:C 15.9+4.06 19.3+3.35 20.94.3.81 23.44.9.54 75.3 4. 10.96 92.5+_8.08 107.2 + 16.3 194.2 4. 23.10 548.7 4. 79.22 154.84.31.72 87.9 4. 15.06

0.8_+0.67 1.34.0.46 2.9_+ 1.38 7.2+2.51 10.5 4. 1.59 13.84.2.97 26.4 _+ 7.53 43.5 _+ 5.82 106.4 4. 22.93 22.7+6.61 --

15.1 18.0 18.0 16.3 64.9 78.7 80.8 150.7 442.5 132.3 87.9

II III IV V VI VII VIII IX Total nymph Total nymph Total adult

? 3 ~ 3 ~ 3 ~ 3 J 3 ~ ¼ '~ ~ `5 3

21 20 19 17 11 I1 9 9

124.2.4 124.3.0 11 + 3.2 104.2.9 10+2.6 10 4. 3.7 124.3.8 10 4. 3.5 87 4. 25.1 554. 14.1 28 + 3.5

27C 4.24. 1.42 7.54. 1.79 11.7 4. 2.64 29.3+8.79 73.7_+ 10.46 126.4 _+ 13.01 196.3_+28.13 255.3 + 31.64 704.4 4. 97.88 126.44.25.10 158.2 ___17.68

1.74.0.46 2.94.0.92 3.4 4. 0.46 7.5_+2.30 20.94.8.91 39.3 _+ 8.99 63.84. 13.94 61.9 _+ 14.94 200.4 4. 52.45 36.44. 13.05 --

2.5 4.6 8.3 21.8 52.8 87.1 133.5 193.4 504.0 90.0 158.2

I1 11I IV V VI VII VIII IX Total nymph Total nymph Total adult

~ '~~ ~ ~ ~ '~ ~ ~ 3' :~

3 o~ ,5 ,5 3

19 19 17 14 13 10 10 9

8+1.5 7 + 1.0 9 4. 1.4 1 0 + 1.7 134. 1.6 10 + 1.4 I1 4.3.0 8 _+ 2.5 76 4. 14. I 47 4. 7.2 17 + 4.2

2.1 + 0.46 2.9___0.67 6.3 4. 1.38 14.74.5.48 33.54.4.10 38.9 4. 11,42 47.74. 10,59 100.9 4. 30,43 246.9 4. 64,53 59.5 4. 12,09 --

2.1 5.5 45.2 90.8 119.7 117.2 137.7 164.5 683.5 264.1 200.9

II III IV V VI VII VIII IX Total nymph Total nymph Total adult

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3 ~ ~5 3 3

17 13 10 8 8 4 4 4

9_+2.2 84. 1.7 8 ___1.7 94.1.4 104. 1.5 10+2.1 8 4. 1.0 7 4. 1.5 69 4. 13.1 44 + 6.2 9 _+ 2.5

32C 5.04.1.04 8.4_+ 1.17 51.5 4. 15.94 105.5+21.64 153.2_+27.96 156.1 + 14.02 185.44.27.37 265.4 4. 34.33 930.5 4. 143.47 323.6 _+ 67.75 200.9 4. 25.95 3TC 3.74.0.79 6.7+0.96 16.3 4. 3.35 30.54.12.53 36.8_+ 11.89 73.74.15.70 45.2 4. 11.88 134.8 4. 19.71 347.7 4. 76.87 94.0 _+ 29.58 33.4 4. 4.6

0.84.0.20 2.94. 1.84 3.3 _+ 1.38 3.4+0.92 5.44.2.30 10.54.2.51 18.0 4. 3.18 29.7 4. 10.30 74.0 4. 22,63 15.8 + 6.65 --

2.93 3.77 12.98 27.2 31.4 63.2 27.2 105.1 273.8 72.3 33.5

For adult females see Table 4. All values (,~' + SD) are given in J/spider.

Table 4. Effects of temperature on food consumption and egg production in C. cicatrosa fed ad libitum on C. fatigans Parameter Adult period (day) Food consumed (J} Food converted (J) Energy allocated for egg production (J) Interoviposition period (day) Egg sacs produced (No.) Weight (wet) of an egg sac (rag) Number of eggs per sac (mean/sac) Eggs produced (No.) Eggs produced (J) Live weight of an egg (~ug) Calorific content of an egg (J) Water content of eggs ('~o) Silk used for egg sac construction (J) Egg production efficiency (%)

22 C

2T'C

32°C

37 C

157.2 _+ 35.1 2391.0 _+468.03 851.4 4. 234.66

143.5 + 32.67 3539.7 _ 494.4 741.3 4. 118.38

103.7 _+ 31.71 2741.8 + 580.2 794.1 4. 137.3

21.5 _+4.87 686.9 __ 31.02 205.5 + 67.06

843.9 4. 186.57 7.9 __ 1.71 20 4.1 + l.ll

803.3 4. 141.7 7.2 + 1.61 20 4.1 _+ 1.00

872.96 4. 137.8 6.5 4. 1.94 16 6.04. 1.01

220.6 + 62.79 4.3 4. 1.0 5 2.24.0.44

23.2 464.5 +_ 108.06 704.5 4. 149.5 162.0 _+ 11.22 1.51 4. 0.17 66

23. I 462.1 4. 57.47 671.2 ___91.97 149.0 + 10.41 1.47 +_ 0.126 60

29.6 479.2 4. 77.53 712.0 4. 121.18 188.0 4. 12.42 1.51 + 0.17 69

22.7 113.3 + 25.87 190.0 4. 58.19 85.0 + 8.9 1.67 4. 0.13 24

139.4 4. 37.08 29.4

132.2 _ 23.4 19.0

110.9 4. 16.62 26.0

30.56 4. 8.83 27.6

Each value represents the average ( ~ + SD) performance of 5-7 females.

S. PALAN1CHAMY

66

equivalent to 687 J in 22 days. The total consumption of an adult male was very low and decreased at 22 and 37°C (Table 3). During the entire life span of a female (231 days), the food consumption of C. cicatrosa was maximal (4244J) at 27°C and minimal at 37°C (1035J for 89 days). The values were 3672 and 2940 J at 32°C (180 days) and 22°C (375 days), respectively (Table 2). In comparison with the total female consumption, males consumed only 243,285, 525 or 127J at 22, 27, 32 or 3 7 C , respectively. With increasing temperature, the energy extraction efficiency of C. cicatrosa increased slightly. It was 73 and 79°o in the female at 32 and 37:C, respectively (Table 2). However, the difference observed in the efficiencies in the various temperature groups were not statistically significant (22 vs 37°C, t = 4.263, P < 0.05). Adult males also showed a similar marginal increase in energy extraction at the higher test temperatures. Temperature failed to significantly modify the energy extraction efficiency in C. cicatrosa.

Data obtained on mosquito food energy converted into body substance by C. cicatrosa as a function of temperature were almost doubled and redoubled, as the life stages advanced at 27 and 32:C: temperature levels of 22 and 37°C appear to be extreme and the least conversion was noted at 22 and 37~C (Table 3). Females were better converters than males. The total food energy converted by an adult female was 85t and 794 J at 22 and 3 2 C , respectively (Table 4): 741 or 206 J at 27 or 3 7 C , respectively. Except at 37 C, adult females converted a maximal amount at all the test temperatures. Adult males failed to sho~ significant conversion at the tested temperatures. C. cicatrosa females at 22 or 27 C oviposited 20 times; the individuals at 32 or 37 C laid 16 or 5 egg sacs: a female at 2 2 C drew nine times the reserve energy for the purpose of oviposition (Fig. 2). Thus overdrawing the reserve energy for oviposition appears to be a c o m m o n function in C. cicatrosa at different temperatures. On the whole, the average feeding rate o1"either sex

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Fig. 2. Each column represents the total food convers)on/oviposition into body substance, egg and silk by C. cicatrosa fed ad libitum at different temperatures at each oviposition. (Note: the energy allocated for silk production is more or less equal, while that apportioned between egg production and growth continuously fluctuated.)

Effect of temperature on growth and metabolism in spiders

67

alent to 705, 671,712 or 190 J, respectively (Table 4). Within the range of 22-32~C, C. cicatrosa expended more or less equal energy for egg production, though it significantly influenced food intake. In terms of oviposition, the relationship between consumption and egg production revealed that age considerably reduced egg production (Fig. 3). For instance, a female at 27°C produced 31 eggs during the 4th egg sac, the corresponding value for the 15th interoviposition period was 15 eggs. Temperature did not affect egg production efficiency and hence, no apparent trend was obtained. The average interoviposition period was 7.9 or 6.5 days in the individual at 22 or 32°C. With increasing temperature, the period became shorter and shorter (7.2 or 4.3 days at 27 or 37°C, respectively) (Table 4). Thus the interoviposition period is a temperaturedependent characteristic.

was lowest at 22°C (1017 or 1352 J/g.day for female or male, respectively) and highest at 37°C (1829 or 1984 J/g. day for female or male, respectively). Males showed higher feeding rates than females (Table 2). The food energy metabolized by the female was the highest at all test temperatures. Up to 32°C the conversion rate of C. cicatrosa increased with increasing temperature (Table 2). It was more or less twice as high at 32 and 37°C than at 22°C. The conversion efficiency of the female was higher than that of the male. At 22°C the female exhibited maximum efficiency (33%), whereas the individual at 27°C presented a low value (22%). Relation between consumption and egg production

Individuals at different temperatures (22, 27, 32 or 37°C) respectively consumed 2391, 3540, 2742 or 687 J and produced 465, 462, 479 or 113 eggs equiv-

37"C

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Fig. 3. Egg production in C. cicatrosa, as a function of age (since maturity), receiving food ad/ibitum at 22, 27, 32 and 37°C. Numbers represent the respective oviposition frequencies. While the vertical lines indicate the deviation of egg number, the horizontal ones represent the deviation of interoviposition period (day).

160

68

S, PALANICHAMY

With increasing temperature, the number of egg sacs produced by C. cicatrosa gradually decreased. A progressive decrease in egg sac production in C. cicatrosa reared at high temperature considerably reduced the adult duration: for instance, the duration was only 22 days at 37°C, as against 157 days at 22~C. Therefore, temperature affects egg production mainly by reducing the span of adulthood (Fig. 3). Correspondingly, the total number of eggs produced was dependent on temperature through the span of adulthood. For instance, C. cicatrosa produced 462 eggs during 144 days at 27°C as against 113 eggs (22 days) at 3 7 C . A comparison of the number of eggs produced per day showed a progressive increase with increasing temperature: the values were 2.9, 3.2, 4.6 or 5.3 eggs at 22, 27, 32 or 3T'C, respectively. However, the mean number of eggs contained per clutch did not significantly vary at 22, 27 or 37'-'C (23 eggs each): the female at 32-C produced larger clutches (with 30 eggs) (Table 4). Age affected egg production in C. cicatrosa at all the test temperatures (22, 27 and 32°C) and the capacity to produce eggs decreased with advancing age (Fig. 3). The weight of an egg at 3 7 C decreased considerably. The average weight of the egg was 162 or 188 #g at 22 or 32°C, respectively; at 37"C it was only 85 #g. The reduced weights of the egg sac and eggs at 3T'C were attributed to a lower water content, as it was lost to the environment. The energy content of a single egg did not significantly differ at the various test temperatures (22 vs 3 2 C , t = 1.82, P < 0.5:27 vs 37=C, t = 2.01, P < 0.5) (Table 4). The amount of silk produced by individuals at test temperatures varied significantly: 139, 132, 111 or 31 J at 22, 27. 32 or 37~C (Table 4), respectively. These quantities were about 15-20°; of the respective total conversion. However, the weight of a single egg sac did not differ in the successively oviposited sacs. DISCUSSION

A major problem in rearing C. cicatrosa is the frequent death of test individuals. Increased temperature results in high mortality, especially during moulting periods. Moulting is a critical event in the life of a spider and high temperature aggravates the situation, because of excessive loss of moulting fluid. It has been observed that the orb-weaving spider Archaearanea tepidariorum suffers 98','0 mortality in the juvenile stage (Valerio, 1975). The growth and developmental rates of poikilotherms are logarithmically temperature dependent. This has been shown for many arthropods as well as for spiders. The growth of C. cicatrosa is also significantly influenced by temperature. Workman (1978) has found that the growth of nymphal T. terricola was significant under fluctuating temperature. Valerio (1976) observed that adult A. tepidariorum fail to display significant growth. Like growth rates, the life span of C. cicatrosa is also associated with logarithmic temperature dependence. The duration of instars of T. terricola is found to be significantly reduced ~mder fluctuating temperature (Workman, 1978), suggesting that the associated high temperature shortened the instar

duration. When C. cicatrosa were fed with an increased food ration (Palanichamy. 1984a1, they exhibited a similar trend. The spiders exhibit a characteristic pattern of feeding under different environmental factors. When prey availability is restricted, the spider is likely to extract as much energy as possible from the offered prey (Palanichamy, 1984a: Palanichamy and Baranikumar 1984). Even though food was given ad libitum, the consumption of the spiders was also a temperature-dependent function, as has been observed in a number of arthropods (e.g. Richards, 1964). As a part of its genetic endowment, ever\ animal has a capacity to compensate for environmental change which is limited within a range of a given parameter. For example, total food consumption of nymphal C. cicatrosa increased from 22 to 32 C, but rapidly fell at 37 C. Hence, temperature between 27 and 3 2 C is considered optimum for this animal and consumption falls on either side: under certain temperature conditions, the spiders are restricted in their mobility and, in turn, their prey-catching capacit) (Kessler, 1971). It is probable that tropical spiders exhibit faster rates of consumption than temperate ones (Palanichamy, 1980). Among the wandering spiders, the rate of consumption in tropical P. birmanica is very high (3926J/g.day) (Prakash. 1979) when compared to temperate P. luguhris (293J/g.day) (Edgar, 1971b). The web-building spider C. cicatrosa exhibited increased feeding rate with increasing temperature. When compared to the tropical lycosid P. hirmanica, the consumption of web-building C. cicatrosa is tow. It has been shown that hunting spiders may be able to change their rate of attack more than web-building spiders, which are filter feeders and generally less mobile than hunting spiders (Palanichamy, 1983). It has been shown that with constant availability of prey, the body size is highly influenced by temperature (Palanichamy et al., 1982). The energy content of female C. cicatrosa in the final nymphal stage also exhibited a two-fold increase at 32 C as against the nymph at 22 C. This explains the variations in the maximum weights of different ecotypes of arthropods with seasonal and geographical distribution (Odum, 1971). However, size-related sexual dimorphism among spiders is not uncommon (e.g. Blanke. t974). C. cicatrosa is a sex dimorphic species, the female is the largest compared to the "'pigmy" male. The conversion efficiency of C. cicatrosa was higher than that of hunting spiders such as P. hirmanica (6-1Y),;) and P. leucopalpis ('4-~ ,,) (Prakash, 1979) and for the orb-weaving Linyphia trianguhlri~' (27",,) (Turnbull, 1962). Various species of meadow-living temperate web spiders exhibited a range of 5 lY',, (Kajak, 1971). But, C. citricola, a tropical webbuilding spider, fed ad lihitum showed an increased efficiency (Palanichamy and Baranikumar. 19841. It is likely that various environmental parameters like temperature affect the conversion eflicienc~ of spiders. Egg production As indicated previously, the literature pertaining to the effects of temperature on egg production in

Effect of temperature on growth and metabolism in spiders spiders is scanty. Analysis of food utilization and egg production reveals that C. cicatrosa expends in the range of 70-80~o of its food energy for metabolism, including web material, leaving the rest for egg production at tested temperatures in the laboratory. Relating the rates of prey capture by the spider (Turnbull, 1962; Hagstrum, 1970; Van Hook, 1971), Eberhard (1979) suggests 250/0 of the prey weight is converted into egg biomass. The present work generally confirms the above finding. The number of egg sacs produced by spiders is varied by many intrinsic and extrinsic factors (Palanichamy, 1984a). Under natural conditions, wandering spiders like P. lugubris normally produce 1 or 2 cocoons (Edgar, 1971a), but C. cicatrosa builds a range of 10-25 eggs sacs; it is likely that a genetically determined factor can be modified by environmental factors like temperature. In several species of spiders it has been observed that the number of eggs in successive clutches gradually decreases (e.g. Mikulska and Jacunski, 1968; Kessler, 1971, 1973; Taylor and Peck, 1974; Valerio, 1976; Palanichamy, 1984a). C. cicatrosa reared at different temperatures (22, 27 and 32°C) also produced a smaller number of eggs in the later clutches, which may contain infertile eggs owing to the exhaustion of sperms stored in spermathecae (Palanichamy and Pandian, 1983). An elevation in temperature resulted in shorter interoviposition periods. Kessler ( 1971) observed that the length of the egg-ripening period of Pardosa sp. was dependent on climatic conditions. The interoviposition period of C. cicatrosa was not of uniform duration throughout the egg laying term at any given temperature (see Fig. 3). At either test temperature (27 or 32°C), older C. cicatrosa extended the duration. No apparent difference in the interoviposition period of an individual was noted at the highest test temperature (3T~'C); perhaps it died at the peak of egg production. Valerio (1976) has observed that there is a trend in A. tepidariorum for the interval between sacs to increase as the female gets older. The total number of eggs produced by a spider depends on the span of adulthood at a particular temperature; the shorter the adult life, the fewer the number of eggs produced. On the contrary, egg production/day increased with increasing temperature, signifying that elevated temperature augmented the reproductive capacity of the spider. Large variations noted in the egg weight of C. cicatrosa were mainly attributed to experimental temperature; the egg lost weight at the highest temperature (37°C), mainly due to the loss of water. Studies of other spiders have also exhibited small variations in egg weights (Kessler, 1971, 1973: Wise, 1975), but studies on laboratory-reared L. triangularis showed large variations in egg weight (Turnbull, 1962). On the contrary, semi-captive Agelenopsis aperta responded to high feeding regimes with increased egg size (Riechert and Tracy, 1975). Since the web material produced by C. cicatrosa in the terraria was negligible (see also Palanichamy, 1984a; Palanichamy and Baranikumar, 1984), it was not considered in this analysis. But the amount of silk used by the individuals for egg sac construction was sufficient for estimation. It proved to be 3-5'~',, of the

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respective consumption. The thickness of the silk layer is not likely to differ within or between the temperature groups. SUMMARY

Aspects of food consumption, growth and egg production were studied in C. cicatrosa as a function of temperature (22, 27, 32 and 37°C). A C. cicatrosa female (fed ad libitura on C.fatigans) underwent nine instars and attained adulthood in 218, 144, 76 and 67 days at 22, 27, 32 and 37°C, respectively. But the male attained adulthood after six instars in 144, 55, 47 and 44 days at the respective test temperatures. Almost all chosen parameters of food utilization and egg production displayed a positive relation with increasing temperature up to 32°C. At 37°C, mortality was high (93~o). However, temperature fails to significantly alter the efficiency of energy extraction (75°0) conversion (around 27%) and egg production (around 250/0). But, it significantly reduced egg production (from 465 eggs at 22°C to 113 eggs at 37°C), primarily affecting the adult period, which decreased from 157 days at 22°C to 22 days at 37°C. However, an analysis of egg production/day increased with increasing temperature and this resulted in a shorter interoviposition period (8 days at 22°C, 4 days at 37°C). Acknowledgements--I thank Dr S. Arunachalam, Dr R. Ponnuchamy and K. Mantharam and P. Baskaran for their help. REFERENCES

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