Starvation

Willis and Lewis (1957) determined the mean survival times of 11 species of cockroaches deprived of food, water, or both (Table 4.3). When deprived of food and water, the insects can live from 5 days (male Blattella vaga) to 42 days (female P. americana). When given dry food

Table 4.2. Gut contents of cockroaches collected between 20:00 and 4:00 at La Selva Research Station, Costa Rica, between January and May 1992 (WJB and J. Aracena, unpub.data).

Cockroach species

n

Material in foregut

Blaberidae

Capucina rufa

Male

5

Epiphylls

Female

2

Epiphylls, bark scraps

Nymph

6

Epiphylls, bark scraps

Epilampra rothi

Male

64

Dead leaf chips

Female

20

Algae, green plant, dead leaf,

trichomes

Nymph

80

Dead leaf chips, insect parts

Blattellidae

Xestoblatta hamata

Male

16

Dead leaf, bird dung

Female

11

Inga bark chips,algae, dead

leaf chips, fruit, leaf debris

Nymph

25

Finely ground dead leaf,

insect parts

Cariblatta imitans

Male

16

Algae

Female

10

Algae

Nymph

4

Algae

ñ _I_I_I_I_I_I_I_1_I_I_I_I_I_I_I_ ro gO 2 4 6 8 10 12 14 16 3

Days of the Reproductive Cycle in Females of Parcoblatta fulvescens

ñ _I_I_I_I_I_I_I_1_I_I_I_I_I_I_I_ ro gO 2 4 6 8 10 12 14 16 3

Days of the Reproductive Cycle in Females of Parcoblatta fulvescens

Fig. 4.2 Feeding and drinking cycles in relation to the reproductive cycle of the wood cockroach Parcoblatta fulvescens. Filled circles, water consumption; open squares, food consumption; EC, egg case formation; ECD, egg case deposition. From Cochran (1986b), courtesy of Donald G. Cochran, with permission from Elsevier Press.

but no water, they lived for about the same period of time as those deprived of both. If they are provided with water, most lived longer. Some species can live for 2 to 3 mon on water alone, and others significantly longer. Virgin females of Eublaberusposticus live an average of 360 days on water alone, whereas starved but mated females can live an average of 8 mon and are even able to produce 1 or 2 litters, yielding about 26 young. One female mated at emergence was starved for 252 days, during which time she produced 2 litters totaling 50 nymphs. She was then given food on day 252 (and thereafter), mated again 4 days later, and lived an additional 525 days, producing 5 more oothecae from which 24, 18, 5, 1, and 0 nymphs hatched. Although this female had been starved for the first 8 mon of adult life, after food was made available she managed to give birth to a total of 98 offspring, which is about normal for this species (Roth, 1968c).

There is a significant difference in starvation resistance between males and females in cockroach species exhibiting sexual dimorphism in body size. In Table 4.3, males and females are of similar size only in Neostylopyga rhom-bifolia, Eurycotis floridana, and Nauphoeta cinerea; in these cases, survival of males and females is similar. In the remaining species males are significantly smaller than females and are more vulnerable to starvation. A larger body size is correlated with bigger fat bodies and their accumulations of carbohydrates, lipids, and uric acid; these reserves can be rapidly mobilized on demand (Mullins and Cochran, 1975b; Downer, 1982). The nutrients and water housed in developing oocytes are additional resources available to starving females. The strategy for a food-deprived female of P. americana seems to involve re sorption of yolk-filled eggs, storage of their yolk proteins, and then rapid incorporation of protein into eggs when feeding re-ensues (Roth and Stay, 1962b; Bell, 1971; Bell and Bohm, 1975).

A variety of digestive attributes help cockroaches buffer food shortages. The large crop allows an individual to consume a substantial quantity of food at one time. This bolus then acts as a reservoir during periods of fasting. When fully distended with food, the crop is a pear-shaped organ about 1.5 cm in length and 0.5 cm at its widest part (in Periplaneta australasiae). It extends back to the fourth or fifth abdominal segment, crowding the other organs and distending the intersegmental membranes. A meal may be retained in the crop for several days (Abbott, 1926; Cornwell, 1968). Solid food is also retained in the hindgut of starving P. americana for as long as 100 hr, although the normal transit time is about 20 hr (Bignell, 1981); this delay likely allows microbial biota to more thoroughly degrade some of the substrates present, particularly fiber. The functional significance of intestinal symbionts increases in times of food deficiency and helps to maintain a broad nutritional versatility (Zurek, 1997). A starving cockroach is thus indebted to its microbial partners on two counts: first, for eking out all possible nutrients in the hindgut, and second, for mobilizing uric acid stored in the fat body (Chapter 5). When food is again made available, starved P. americana binge. After starving for 13 days the amount of food consumed rose to five times the normal level, then leveled off after approximately 20 days. Greater consumption was accomplished by larger and longer meals, not by increasing the number of foraging trips (Rollo, 1984a).

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