Temporal changes in aphid abundance pose a considerable challenge to ovipositing aphidophagous ladybirds, as in order to maximize their fitness they need to synchronize their reproduction with the early development of aphid populations. Field census data and laboratory experiments were used to determine how ovipositing females of the two-spot ladybird, Adalia bipunctata (L.), assess whether an aphid population is suitable for exploitation. In the field, two-spot ladybirds usually laid eggs well before aphid populations peaked in abundance. In the laboratory they showed a marked reduction in their reproductive numerical response in the presence of larvae of their own species but not of other aphidophagous ladybirds. At the highest aphid density this was not a consequence of competition for food between larvae and ovipositing females. In the presence of conspecific larvae gravid females were very active and as a consequence more likely to leave an area, and when confined with other conspecific females or larvae laid fewer eggs and later than females kept on their own. The extent of the inhibition of egg laying is negatively correlated with the rate of encounter with larvae. Thus it is proposed that gravid females appear mainly to use the presence of conspecific larvae to assess the potential of an aphid colony for supporting the development of their offspring.
Microsatellite DNA fingerprinting has been recently applied to studies of relatedness in wild animals (Amos et al. 1993; McDonald Q Potts 1994; M O M et al. 1994; Craighead et al. 1995) and suggested to be ideal for studies of parentage and kinship (Queller ef al. 1993). In many aquatic animals, reproductive and behavioral ecology has been limited due to lack of proper genetic markers.
The cya-5 nuclear mutant of Neurosopora crassa was previously shown to be deficient in cytochrome aa3, cytochrome c oxidase activity, and the immunologically detectable COXI protein. We have now demonstrated that the mitochondria of this mutant contain mRNA for the COXI protein and that COXI cannot be detected during pulse-chase labeling experiments of mitochondrial translation products. Cloning and analysis of the cya-5 gene reveal a long open reading frame capable of encoding a 1136 amino-acid protein. Sequence analysis suggests that the potential CYA-5 protein contains a mitochondrial targeting sequence at its amino-terminus. The long open reading frame also contains a 200 amino-acid region with homology to the PET309 protein, which is required for the production or stability of intron-containing coxI mRNAs, as well as the translation of mature coxI mRNAs, in the yeast Saccharomyces cerevisiae. These data suggest that the CYA-5 protein of N. crassa is required in a post-transcriptional step for COXI expression, most probably for the efficient translation of coxI mRNA.
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