Reduced Fecundity

One of the most significant costs exacted by carrying egg cases lies in terms of fecundity. Oviparous type A cockroaches have relatively high reproductive rates because the interval between successive oothecae is short, usually much shorter than the period of incubation. Females typically produce a second egg case long before the first laid hatches. Oviparous species with external egg retention as well as ovoviviparous females produce relatively few oothecae because oocytes do not mature in the ovaries while an ootheca is being carried. Viviparity is particularly expensive, in that female D. punctata have fewer eggs per oothecae, produce fewer oothecae per lifetime, and have a longer period of gestation than any other blaberid (Roth and Stay, 1961; Roth, 1967d). Consequently, the number of egg cases per lifetime decreases and the ovipo-sition interval increases in the order oviparous, ovovivip-arous, viviparous (Fig. 7.9) (Willis et al., 1958; Roth and Stay, 1959,1962a; Breed, 1983).

Fecundity also appears reduced in cockroach species that exhibit parental care, particularly if the care involves feeding young dependents on bodily fluids. Such pabulum may be demanding in terms of the structures involved in its manufacture, the nutrients incorporated into the secretions, and the energy required to produce them.

D. punctata

%_a_m_#_a_ P. surinamensis a ._i i_._•_•__ B. vaga

_a_«_i i_._a_a_ B. germanica a, ,,,. Sup. iongipaipa

Sym. paiiens

0 SO 100 150 200 250 300 350

DAYS

Fig. 7.9 Frequency of oviposition by individuals of different species of cockroach. Each dot represents the formation of an ootheca; the length of the line is the adult lifespan of the female. Symploce pallens (= hospes) and Supella longipalpa (Blattelli-dae) are oviparous and drop the ootheca shortly after it is formed. Blattella germanica and B. vaga (Blattellidae) carry their ootheca externally until the eggs hatch. The blaberids Pycnoscelus surinamensis (parthenogenetic) and Nauphoeta cinerea are ovoviviparous, and Diploptera punctata is viviparous. After Roth (1970a).

Fig 7.10 Post-oviposition provisioning in cockroaches. Oviposition refers to the release of eggs from the ovaries, while extrusion is the permanent expulsion of eggs from the body. Deposition is the disassociation of the egg case from the body. Independence is the ability of neonates to live apart from the parent(s). Modified from Nalepa and Bell (1997), with the permission of Cambridge University Press.

Fig 7.10 Post-oviposition provisioning in cockroaches. Oviposition refers to the release of eggs from the ovaries, while extrusion is the permanent expulsion of eggs from the body. Deposition is the disassociation of the egg case from the body. Independence is the ability of neonates to live apart from the parent(s). Modified from Nalepa and Bell (1997), with the permission of Cambridge University Press.

Perisphaerus sp. and Thoraxporcellana both exhibit a reduction in the number of offspring per clutch as compared to other ovoviviparous species (Roth, 1981b).

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