Nutrition and Development

Cockroach development is closely attuned to nutritional status (Gordon, 1959; Mullins and Cochran, 1987). Poor food quality or deficient quantity results in a prolongation of juvenile development via additional molts and/or prolonged intermolts (Hafez and Afifi, 1956; Kunkel, 1966; Hintze-Podufal and Nierling, 1986; Cooper and Schal, 1992). Diets relatively high in protein produce the most rapid growth (Melampy and Maynard, 1937), and on diets lacking protein, nymphs survive for up to 8 mon, but eventually die without growing (Zabinski, 1929). The effect of nutrition on development is most apparent in early instars, corresponding to what is normally their period of maximum growth (Woodruff, 1938; Seamans and Woodruff, 1939).A nutrient deficiency in a juvenile cockroach results in a growth stasis, in which a semi-starved nymph "idles" until a more adequate diet is available. This plasticity in response to the nutritional environment is suggestive of the arrested development exhibited by workers (pseudergates) in lower termite colonies, and is hypothesized to be one of the key physiological responses underpinning the shift from subsocial to eusocial status in the termite lineage (Nalepa, 1994, discussed below).

Reproductive development is also closely regulated by the availability of food in cockroaches. Females stop or slow down reproduction until nutrients, particularly the amount and quality of ingested protein, is adequate (Weaver and Pratt, 1981; Durbin and Cochran, 1985; Pipa, 1985; Mullins and Cochran, 1987; Hamilton and Schal, 1988). In P. americana the initial response to lack of food is simply the slowing down of oocyte growth, but if starvation becomes chronic the corpora allata are turned off and reproduction effectively ceases. When food once again becomes available the endocrine system is rapidly reactivated and normal reproductive activity follows within a short time (Bell and Bohm, 1975). Kunkel (1966,1975) used feeding as an extrinsically controllable cue for synchronizing both the molting of nymphs and the oviposition of females in B. germanica and P. americana. There is substantial evidence, then, that domestic cockroaches tightly modulate "high demand" metabolic processes such as reproduction and development in response to changes in food intake, and that both physiological processes can be controlled in individuals by manipulating their food source.

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