Quantification of intraoral pressures during nutritive sucking: methods with normal infants.

We report quantitative measurements of ten parameters of nutritive sucking behavior in 91 normal full-term infants obtained using a novel device (an Orometer) and a data collection/analytical system (Suck Editor). The sucking parameters assessed include the number of sucks, mean pressure amplitude of sucks, mean frequency of sucks per second, mean suck interval in seconds, sucking amplitude variability, suck interval variability, number of suck bursts, mean number of sucks per suck burst, mean suck burst duration, and mean interburst gap duration. For analyses, test sessions were divided into 4 × 2-min segments. In single-study tests, 36 of 60 possible comparisons of ten parameters over six pairs of 2-min time intervals showed a p value of 0.05 or less. In 15 paired tests in the same infants at different ages, 33 of 50 possible comparisons of ten parameters over five time intervals showed p values of 0.05 or less. Quantification of nutritive sucking is feasible, showing statistically valid results for ten parameters that change during a feed and with age. These findings suggest that further research, based on our approach, may show clinical value in feeding assessment, diagnosis, and clinical management.

Tests of search image and learning in the wild: Insights from sexual conflict in damselflies.

Search image formation, a proximal mechanism to maintain genetic polymorphisms by negative frequency-dependent selection, has rarely been tested under natural conditions. Females of many nonterritorial damselflies resemble either conspecific males or background vegetation. Mate-searching males are assumed to form search images of the majority female type, sexually harassing it at rates higher than expected from its frequency, thus selectively favoring the less common morph. We tested this and how morph coloration and behavior influenced male perception and intersexual encounters by following marked Ischnura elegans and noting their reactions to conspecifics. Contrary to search image formation and associative learning hypotheses, although males encountered the minority, male-like morph more often, sexual harassment and clutch size were similar for both morphs. Prior mating attempts or copula with morphs did not affect a male's subsequent reaction to them; males rarely attempted matings with immature females or males. Females mated early in the day, reducing the opportunity for males to learn their identity beforehand. Once encountered, the male-like morph was more readily noticed by males than the alternative morph, which once noticed was more likely to receive mating attempts. Flexible behavior gave morphs considerable control over their apparency to males, influencing intersexual encounters. Results suggested a more subtle proximal mechanism than male learning maintains these color polymorphisms and call for inferences of learning to be validated by behavior of wild receivers and their signalers.

Using comparative genomic hybridization to survey genomic sequence divergence across species: a proof-of-concept from Drosophila.

BACKGROUND: Genome-wide analysis of sequence divergence among species offers profound insights into the evolutionary processes that shape lineages. When full-genome sequencing is not feasible for a broad comparative study, we propose the use of array-based comparative genomic hybridization (aCGH) in order to identify orthologous genes with high sequence divergence. Here we discuss experimental design, statistical power, success rate, sources of variation and potential confounding factors. We used a spotted PCR product microarray platform from Drosophila melanogaster to assess sequence divergence on a gene-by-gene basis in three fully sequenced heterologous species (D. sechellia, D. simulans, and D. yakuba). Because complete genome assemblies are available for these species this study presents a powerful test for the use of aCGH as a tool to measure sequence divergence. RESULTS: We found a consistent and linear relationship between hybridization ratio and sequence divergence of the sample to the platform species. At higher levels of sequence divergence (< 92% sequence identity to D. melanogaster) approximately 84% of features had significantly less hybridization to the array in the heterologous species than the platform species, and thus could be identified as "diverged". At lower levels of divergence (>or= 97% identity), only 13% of genes were identified as diverged. While approximately 40% of the variation in hybridization ratio can be accounted for by variation in sequence identity of the heterologous sample relative to D. melanogaster, other individual characteristics of the DNA sequences, such as GC content, also contribute to variation in hybridization ratio, as does technical variation. CONCLUSIONS: Here we demonstrate that aCGH can accurately be used as a proxy to estimate genome-wide divergence, thus providing an efficient way to evaluate how evolutionary processes and genomic architecture can shape species diversity in non-model systems. Given the increased number of species for which microarray platforms are available, comparative studies can be conducted for many interesting lineages in order to identify highly diverged genes that may be the target of natural selection.