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281.
282.
We determined the age-specific fecundity and survival of the solitary parasstoid wasp,Aphidius ervi Haliday (Hymenoptera: Aphidiidae), under constant laboratory conditions. Wasps were reared in each of the four nymphal instars
of apterous pea aphids,Acyrthosiphon pisum (Harris) (Homoptera: Aphididae): L1 (age 24h), L2 (48 h), L3 (72 h), and L4 (120 h). Age-specific survival (lx) and fecundity (mx) differed between parasitoids developing in different aphid instars. The wasps’ life-time reproductive success, as indexed
by the intrinsic rate of population increase (rm), varied non-linearly with adult biomass and host size at parasitization. A close agreement between larval growth rates in
different host instars and adult reproductive performance suggests that, inA. ervi, fitness correlates may be significantly influenced by larval ontogeny and trade-offs in resource allocation. 相似文献
283.
Ana Neves Vera Sequeira Ana Rita Vieira Rafaela Paiva Leonel Serrano Gordo 《Hydrobiologia》2009,636(1):479-488
The importance of cephalopods in marine ecosystems is well recognized as they serve as important predators and prey in many
food chains. During a 1-year period, cuttlefish were monthly sampled in five areas throughout the Sado estuary, and the stomachs
of 445 individuals were examined. Significant changes in the diet according to their life stage were revealed, but similar
food habits were presented by males and females. Juvenile individuals (the smaller ones with no visible distinct gonads) preyed
mainly upon small crustaceans, while the immature ones (maturity stages I and II) had the most diverse diet with brachyurans
as the major prey group. The mature individuals (maturity stages III and IV) showed a clear preference for larger crabs and
fishes. Although the cuttlefish are known for their opportunistic feeding behaviour, a preference for some prey according
to length and behaviour could be perceived during this study. Seasonal differences in the diet were mostly due to the variation
of individuals according to their maturity stage during the year. 相似文献