Segregation of colony odor in the desert ant Cataglyphis niger.

There are two separate, and presumably opposing, processes that affect colony odor in the desert ant Cataglyphis niger: (1) biosynthesis and turnover of these chemicals by individual ants, and (2) homogenization of colony odor through exchange of cues. The first increases signal variability; the latter decreases it. The impact of these factors was tested by splitting colonies and monitoring the profile changes occurring in the postpharyngeal glands (PPG) and cuticular hydrocarbons. From each of two polygynous nests four daughter colonies were formed, three monogynous and one queenless. Thereafter, 10 ants from each were randomly selected each month, for three successive months, for analyses of their PPG and cuticular hydrocarbons. From two colonies we also obtained ants from a known matriline. Over time, there was a shift in hydrocarbon profiles of both the PPG and cuticular washes in each of the tested colonies. Moreover, by subjecting selected hydrocarbon constituents to a discriminant analyses based on their relative proportions, all of the daughter colonies (queenright and queenless) were distinguishable from each other and from their respective mother colonies. In each of the queenright daughter colonies, the queen profile was indiscriminable from that of the workers and often was in the center of the group. Full sisters were clearly distinguishable from their nestmates, emphasizing the genetic versus environmental processes that govern colony odor. The effect of time was always superior to the separation effect in contributing to odor segregation. Comparison of the Mahalanobis distances indicated that the shift in hydrocarbon seems to proceed along parallel lines rather than in divergence. However, there was no overt aggression between ants that originated from the different subgroups in dyadic encounters. It appears that in this species a three-month separation pe riod is not sufficient to change the hydrocarbon profile beyond the recognition threshold.

A comparison of intakes of breast-fed and bottle-fed infants during the first two days of life.

OBJECTIVE: In the first days of life, breast-fed infants consume minimal amounts of milk; this may be explained by substrate limitation (limited milk output) and/or by self-limitation (through low appetite and/or suck-swallow competency). The spontaneous milk intake of unrestricted formula-fed infants has not been studied to date. We compared the spontaneous formula intake of unrestricted formula-fed infants to that of breast-fed infants over the first 48 hours of life. We hypothesized that 1) spontaneous formula intake of unrestricted infants is much higher than that of breast-fed infants and 2) spontaneous formula intake correlates positively with gestational age or birthweight. METHODS: We studied 43 healthy, term infants. By maternal choice, 15 infants were exclusively breast-fed and 28 were formula-fed ad libitum every four hours. Breast-fed infants were weighed before and one hour after initiation of feeding, and intake was calculated from the difference between the measurements and corrected individually for the infant's normal postnatal decrease in body weight. Bottles offered to formula-fed infants contained 60 cc, and the remainder was carefully measured. Intakes were expressed as cc/kg/d, and weight changes as % of birthweight. Statistical methods included Student's t tests and stepwise regression analysis. RESULTS: Breast feeding on Day I was 9.6 +/- 10.3 (mean +/- SD) vs. 18.5 +/- 9.6 cc/kg/d in formula-fed infants (p=0.011); on Day 2 it was 13.0 +/- 11.3 vs. 42.2 +/- 14.2 cc/kg/d (p<0.001). Breast-fed infants lost significantly more weight on Day 2 (p=0.015). In multiple regression, when the dependent variable was the second-day intake, the significant independent variables were group (higher intake in the formula-fed group), weight loss (the higher the weight loss, the lower the intake), and first-day intake (the higher the first-day intake, the higher the second-day intake). CONCLUSION: Newborn infants offered formula ad libitum every four hours consumed much larger amounts than breast-fed infants fed according to the same schedule. In addition, weight loss was more marked in breast-fed infants on Day 2 of life.

Precision of a new thermometer for rapid rectal temperature measurement in neonates.

The objective of this article is to evaluate the accuracy and reproducibility of a Penguin electronic thermometer compared with a mercury-in-glass thermometer for rectal thermometry in newborns. The mercury-in-glass thermometer is considered the "gold-standard" for rectal thermometry. Unfortunately, accurate measurement with a mercury-in-glass thermometer requires at least 4 minutes. Rectal temperature was obtained in 224 term and near-term infants using a mercury-in-glass and a Penguin thermometers. Paired t-test was used to test the difference between the means, and F-test was used to test the difference between the variances of the two instruments. One hundred and sixty-one of the temperature measurements (72%) taken with the Penguin thermometer were within +/-0.2 degrees C and 208 (93%) within +/-0.5 degrees C from the measurements made with the mercury-in-glass thermometer. The differences in means and in variances were not significantly different between the instruments. The Penguin thermometer is an accurate and reproducible tool for measuring rectal temperature in term and near-term infants compared with the mercury-in-glass thermometer.