Ecophysiology of Aufwuchs-eating cichlids in Lake Tanganyika: niche separation by trophic specialization

Synopsis The Aufwuchs-eating cichlids of Lake Tanganyika show clear trophic differences that are correlated to their morphology, physiology and foraging behaviour. The species are grouped into three categories of relative intestinal length according to their feeding habits. A correlation between the intestinal length and the diet could be demonstrated, ranging from around 2.5 for species ingesting more animal food, to 7.8 for detritivorous and microalgivorous species. The relative intestinal length of domesticTropheus moorii, raised in aquaria was significantly lower than that of wild individuals by a factor of 1.7, demonstrating a wide range of phenotypic adaptability. The activities of trypsin and amylase were at an equal level in four Aufwuchseating species, but the activity of laminarinase of a detritivorous-microalgivorous species (Petrochromis orthognathus) was 2.6 times higher than that of an algivorous species (Tropheus moorii). The laminarinase seems to be an excellent marker enzyme for detritivorous or microalgivorous feeding.     

The utilization of nitrogen from insect capture by different growth forms of Drosera from Southwest Australia

Summary Plants of Drosera species, neighbouring noncarnivorous plants, and arthropods on or near each Drosera sp. were collected at 11 contrasting habitat locations in SW Australia. At three of the sites clones of the rare glandless mutant form of D. erythrorhiza were collected alongside fully glandular counterparts. The ¹⁵N value (¹⁵N/¹⁴N natural isotope composition) of insect-free leaf and stem fractions was measured, and the data then used to estimate proportional dependence on insect N (%N_dI) for the respective species and growth forms of Drosera. The data indicated lower %N_dI values for rosette than for self-supporting erect or for climbing vine species. The latter two groups showed an average %N_dI value close to 50%. The %N_dI increased with length and biomass of climbing but not erect forms of Drosera. ¹⁵N values of stems were positively correlated with corresponding values for leaves of Drosera. Leaf material was on average significantly more ¹⁵N enriched than stems, possibly due to delayed transport of recent insect-derived N, or to discrimination against ¹⁵N in transfer from leaf to the rest of the plant. The comparison of ¹⁵N values of insects and arthropod prey, glandless and glandular plants of D. erythrorhiza indicated %N_dI values of 14.3, 12.2 and 32.2 at the respective sites, while matching comparisons based on ¹⁵N of insect, reference plants and glandular plants proved less definitive, with only one site recording a positive %N_dI (value of 10.4%) despite evidence at all sites of feeding on insects by the glandular plants. The use of the ¹⁵N technique for studying nutrition of carnivorous species and the ecological significance of insect feeding of different growth forms of Drosera growing in a large range of habitats is discussed.     

Are prealbumin plasma levels linked to amino acid supply from peripheral tissues in liver cirrhosis?

Summary Prealbumin plasma level is considered a good index of liver function in liver cirrhosis. However, plasma protein levels depend not only on liver function, but also on amino acid supply which is consequent to nutritional status.In 12 cirrhotics we measured prealbumin plasma levels and the lower limb venous-artero difference of amino acid plasma levels in blood samples taken from femoral vein and femoral artery in post-absorptive conditions considered as a direct index of protein release from peripheral tissues and an indirect index of protein nutritional status.In arterial and in venous plasma amino acid sum was 1.86±0.40 (mean + sd) and 2.00 ± 0.04 mMol/l respectively.Prealbumin plasma levels were found directly correlated with the venousartero difference of amino acid plasma levels (r = 0.57p < 0.05) and of glutamate + glutamine levels (r = 0.73p < 0.007).In conclusions, these data suggest that prealbumin plasma levels are linked to amino acid supply from peripheral tissues in cirrhotics.     

Effects of direct transfer from freshwater to seawater on respiratory and circulatory variables and acid-base status in rainbow trout

Summary The effects of increased ambient salinity (35 mg · ml^-1) were studied at 1, 6, and 24 h after direct transfer of rainbow trout from freshwater to seawater. Two series of experiments were carried out successively. The first series was designed to simultaneously study all the respiratory (except Hb affinity for O₂), circulatory, and acid-base variables in each fish. In this series, fish were fitted with catheters chronically inserted into the cardiac bulbus, the dorsal aorta, and the opercular and buccal cavities. In the second series, designed to study haemoglobin O₂ affinity, fish were fitted with only a dorsal aorta catheter. The ventilatory flow ( ) was markedly increased just after transfer (by 55% at 1 h), then more moderately (by 20% at 6 h and 32% at 24 h). The initial hyperventilation peak was associated with frequent couphing motions. These ventilatory changes resulted essentially from increase in ventilatory amplitude. Initially, standard oxygen consumption (MM}O₂) decreased slightly, the moderately increased (by 12% at 24 h), so that the oxygen convection requirement ( ) increased substantially. In spite of an increased ventilation, the partial pressure of oxygen in arterial blood (P _aO₂) decreased slightly at 1 h, prior to returning to control levels, while partial pressure of carbon dioxide in arterial blood (P _aCO₂) was not significantly decreased. Gill oxygen transfer factor decreased substantially at 1 h (by 35%) then more moderately (by 7% at 1 h and 12% at 24 h). These results suggest a decrease in gas diffusing capacity of the gills. As P _aCO₂ remained approximatively unchanged, the gradual decrease in arterial pH (pH_a) from 7.94 to 7.67 at 24 h must therefore be regarded as a metabolic acidosis. The strong ion difference decreased markedly because the concentration of plasma chloride increased more than that of sodium. Arterial O₂ content (C _aO₂) gradually decreased (by 38% at 24 h) simultaneously with the decrease in pH_a, while the ratio P _aO₂/C _aO₂ increased. In parallel, seawater exposure induced a marked decrease in affinity of haemoglobin for O₂, so that at 24 h, P₅₀ was increased by 26% above the value obtained in freshwater-adapted trout. The increase in could be ascribed initially (at 1 h) to the decrease of P _aO₂ and later to a stimulation of respiratory neurons resulting from the lowered medullary interstitial pH. The decrease in C _aO₂ could be interpreted mainly as a consequence of a decreased affinity of haemoglobin for O₂, likely to be due to the blood acidosis and a predictable increase in chloride concentration within erythrocytes. Cardiac output ( ) slightly decreased at 1 h, then progressively increased by 30% at 24 h. Branchial vascular resistance increased at 1 h by 28%, then decreased by 18% of the control value at 24 h. Systemic vascular resistance decreased markedly by 40% at 24 h. As heart rate (HR) remained significantly unchanged, the cardiac stroke volume initially decreased then increased in relation to the changes in . The increase of , allowing compensation for the effect of decreased C _aO₂ in tissue O₂ supply, was interpreted as a passive consequence of the decrease in total vascular resistance occurring during seawater exposure.Abbreviations a.u. arbitrary units - C _aO₂ arterial oxygen content - pH₅₀ arterial pH at P₅₀ - C _vO₂ venous oxygen content - Hb haemoglobin - HR heart rate - Hct hematocrit - n_Hill Hill coefficient - O₂ standard oxygen consumption - P _aCO₂ arterial partial pressure of carbon dioxide - P _aO₂ arterial partial pressure of oxygen - P _vO₂ oxygen partial pressure in mixed venous blood - P₅₀ oxygen tension at half saturation of haemoglobin - P _VA, P _DA blood pressure in ventral and dorsal aorta - pH_a arterial pH - PIO₂, PEO₂ oxygen partial pressure of inspired and expired water - PO₂ oxygen partial pressure - cardiac output - SEM standard error of mean - S.I.D. strong ion difference - SV cardiac stroke volume - TO₂ gill oxygen transfer factor - U oxygen extraction coefficient - VA ventilatory amplitude - VF ventilatory frequency - VR_G, VR_S branchial and systemic vascular resistances - ventilatory flow - ventilatory oxygen convection requirement     

Uptake and utilization of14C-glycine by embryos ofSebastes melanops

Synopsis The ability of embryos of the viviparous scorpaenidSebastes melanops to take up nutrients from an exogenous substrate was demonstrated by incubating embryos at various stages of development (18–30 days after fertilization) in¹⁴C-labeled glycine for 24 h. Uptake was highest for embryos at the latest stages (28–30 days) and increased at a linear rate during the incubation period. Nutrient uptake was not time dependent in embryos at the early stages (18–22 days). Nutrient utilization byS. melanops embryos was measured by the oxidation of¹⁴C-labeled glycine to¹⁴CO₂. The amount of respired¹⁴CO₂ by the oldest embryos increased significantly at a linear rate over the 24 h incubation period. There was no evidence of nutrient utilization by the youngest embryos. The developmental changes we observed in the uptake and utilization of exogenous glycine are supported by our previous findings that the oldest embryos have fully developed mouths and guts, and require additional nutrition from intraovarian sources at this stage of development.     

Stature variation in the British American Colonies: French and Indian War records, 1755-1763

Personnel records kept by military units of American colonials during the French and Indian War (1755-1763) are analyzed for relationships between environmental factors and stature. A robust American economy and direct access to high-quality food were apparently critical to tallness of this white American male sample. American-born men were taller at all ages than those who had migrated from Europe. January temperatures, rural versus urban birth, and ethnicity also showed stature relationships within the American-born group; thermal effects were by far the strongest of the non-nutritional factors.     

Phosphorus deficiency induced by nitrogen input in Douglas fir in the Netherlands

Summary A re-examination of earlier NPK fertilization experiments in Douglas fir stands on sandy soils shows the effects of high nitrogen input by air pollution during the last 10–15 years on plant nutrition at these sites. In 1960, experimental plots showed a positive growth reaction to nitrogen, phosphorus, and potassium fertilization. All suffered from severe phosphorus deficiency in 1984, low phosphorus in the needles was invariably accompanied by a high nitrogen content, with all N/P ratios between 20 and 30. The same conclusion emerges from an independent investigation of nutrient status of a selection of Douglas fir stands. Hence, if stand productivity and a balanced nutrient status of the trees is to be maintained, the increase in atmospheric input of nitrogen calls for supplementary fertilization. Given the current N/P ratios in the needles, a positive growth response to phosphorus fertilization is to be expected.     

Enhancement of water status by calcium pretreatment in groundnut and cowpea plants subjected to moisture stress

Summary The effect of calcium in the water relations and tolerance to moisture deficits was tested in groundnut and cowpea. In both species, enrichment of tissue with calcium resulted in maintenance of a higher water status under stress associated with low proline accumulation. The extent of membrane damage (as reflected by the absorbance at 273 nm) was lesser in leaves of plants fed with higher levels of Ca⁺⁺ when subjected to simulated stress. The rate of water loss from the leaves of Ca⁺⁺-enriched plants was also lower. The possible role of Ca⁺⁺ in inducing membrane stability and maintenance of higher water status is discussed.     

Growth status of disadvantaged urban Guatemalan children of a resettled community

This paper reports the physical growth and body composition from the first year of longitudinal study of 519 Guatemalan children, and their families, from a disadvantaged urban community consisting largely of refugees of the 1976 earthquake. Four cohorts are described, composed of children of 1,3,5, and 7 years at examination. The children are smaller, weigh less, and have reduced fat stores compared either to NCHS reference data or to upper SES Guatemalan children. Stature (or length) and head circumference deviate more from reference data than do triceps or upper arm muscle circumference. Greater deviations are found in the linear dimensions of males than of females. These children are the smallest yet described from Guatemala City, though they are slightly larger than available rural samples. This suggests a continuum of environmental effects acting upon the growth of children of differing socioeconomic levels.     

The influence of starvation and different diets on the hindgut of isopoda (Mesidotea entomon,Oniscus asellus,Porcellio scaber)

Summary Under conditions of food deprivation, the hindgut epithelium of the experimental animals (Mesidotea entomon, Oniscus asellus, Porcellio scaber) undergoes ultrastructural changes. After the application of different diets it was demonstrated that this part of the alimentary canal contains nutrients, though it is lined by a cuticle. Experimental evidence for the formation of glycogen from glucose offered as the only diet comes from autoradiographic experiments. Amino acids, too, were detected in the hindgut cells soon after refeeding. Lipids, on the other hand, which are first absorbed by the large cells of the midgut glands, were not found in the hindgut epithelium. The existence of lipid inclusions in the hindgut epithelium some weeks after refeeding, however, supports the hypothesis that lipids reach the epithelial cells of the hindgutvia midgut glands and hemolymph.