Rank-related partner choice in the fission–fusion society of the spotted hyena (<Emphasis Type="Italic">Crocuta crocuta</Emphasis>)

When social partners vary in their relative value, individuals should theoretically initiate partnerships with conspecifics of the highest value. Here, we tested this prediction in a wild population of spotted hyenas (Crocuta crocuta). Crocuta live in complex, fission–fusion societies structured by dominance hierarchies in which individuals vary greatly in their value as social companions. Because patterns of association among Crocuta reflect social preferences, we calculated association indices (AIs) to examine how social rank influences intrasexual partner choice among unrelated adults of both sexes. The highest-ranking individuals were generally most gregarious in both sexes. Females associated most often with dominant and adjacent-ranking females. Females joined subgroups based on the presence of particular conspecifics such that subordinates joined focal females at higher rates than did dominants. Dominants benefit from associations with subordinates by enjoying priority of access to resources obtained and defended by multiple group members, but the benefits of these associations to subordinates are unknown. To investigate this, we tested three hypotheses suggesting how subordinates might benefit from rank-related partner choice among unrelated females. We found that subordinates who initiated group formation benefited by gaining social and feeding tolerance from dominants. However, rates at which dominants provided coalitionary support to subordinates did not vary with AIs. Overall, our data resemble those documenting patterns of association among cercopithecine primates. We consider our results in light of optimal reproductive skew theory, Seyfarth’s rank attractiveness model, and biological market theory. Our data are more consistent with the predictions of Seyfarth’s model and of biological market theory than with those of skew theory.     

Present-day genetic composition suggests contrasting demographic histories of two dominant chaetognaths of the North-East Atlantic, <Emphasis Type="Italic">Sagitta elegans</Emphasis> and <Emphasis Type="Italic">S. setosa</Emphasis>

Sagitta elegans and S. setosa are the two dominant chaetognaths in the North-East (NE) Atlantic. They are closely related and have a similar ecology and life history, but differ in distributional ranges. Sagitta setosa is a typical neritic species occurring exclusively above shelf regions, whereas S. elegans is a more oceanic species with a widespread distribution. We hypothesised that neritic species, because of smaller and more fragmented populations, would have been more vulnerable to population bottlenecks resulting from range contractions during Pleistocene glaciations than oceanic species. To test this hypothesis we compared mitochondrial Cytochrome Oxidase II DNA sequences of S. elegans and S. setosa from sampling locations across the NE Atlantic. Both species displayed very high levels of genetic diversity with unique haplotypes for every sequenced individual and an approximately three times higher level of nucleotide diversity in S. elegans (0.061) compared to S. setosa (0.021). Sagitta setosa mitochondrial DNA (mtDNA) haplotypes produced a star-like phylogeny and a uni-modal mismatch distribution indicative of a bottleneck followed by population expansion. In contrast, S. elegans had a deeper mtDNA phylogeny and a multi-modal mismatch distribution as would be expected from a more stable population. Neutrality tests indicated that assumptions of the standard neutral model were violated for both species and results from the McDonald-Kreitman test suggested that selection played a role in the evolution of their mitochondrial DNA. Congruent with these results, both species had much smaller effective population sizes estimated from genetic data when compared to census population sizes estimated from abundance data, with a factor of ~10⁸–10⁹ difference. Assuming that selective effects are comparable for the two species, we conclude that the difference in genetic signature can only be explained by contrasting demographic histories. Our data are consistent with the hypothesis that in the NE Atlantic, the neritic S. setosa has been more severely affected by population bottlenecks resulting from Pleistocene range shifts than the more oceanic S. elegans.     

Amino acid metabolism and protein turnover in larval turbot (Scophthalmus maximus) fed natural zooplankton or Artemia

The present paper studied the influence of different food regimes on the free amino acid (FAA) pool, the rate of protein turnover, the flux of amino acids, and their relation to growth of larval turbot (Scophthalmus maximus L.) from first feeding until metamorphosis. The amino acid profile of protein was stable during the larval period although some small, but significant, differences were found. Turbot larvae had proteins which were rich in leucine and aspartate, and poor in glutamate, suggesting a high leucine requirement. The profile of the FAA pool was highly variable and quite different from the amino acid profile in protein. The proportion of essential FAA decreased with development. High contents of free tyrosine and phenylalanine were found on Day 3, while free taurine was present at high levels throughout the experimental period. Larval growth rates were positively correlated with taurine levels, suggesting a dietary dependency for taurine and/or sulphur amino acids. Reduced growth rates in Artemia-fed larvae were associated with lower levels of free methionine, indicating that this diet is deficient in methionine for turbot larvae. Leucine might also be limiting turbot growth as the different diet organisms had lower levels of this amino acid in the free pool than was found in the larval protein. A previously presented model was used to describe the flux of amino acids in growing turbot larvae. The FAA pool was found to be small and variable. It was estimated that the daily dietary amino acid intake might be up to ten times the larval FAA pool. In addition, protein synthesis and protein degradation might daily remove and return, respectively, the equivalent of up to 20 and 10 times the size of the FAA pool. In an early phase (Day 11) high growth rates were associated with a relatively low protein turnover, while at a later stage (Day 17), a much higher turnover was observed. Received: 19 March 1997 / Accepted: 14 April 1997     

Seasonal growth and composition of fronds of Macrocystis pyrifera in the Falkland Islands

Frond growth of Macrocystis pyrifera in the Falkland Islands was monitored in shallow coastal water from December 1985 to March 1987, and at a different site in deeper water from December 1985 to June 1986. Growth rates in the deeper bed were generally higher than those recorded in the coastal zone. At both sites, node initiation and elongation rate fluctuated according to the seasonal pattern of light or water temperature. In the shallow coastal area, nitrate was abundant in the winter and below detection levels during late spring and summer. Correlation analysis suggests that the production of the fronds of the giant kelp in this area was probably inhibited during the summer months by extremely low concentrations of nutrients. Internal nitrogen was exhausted approximately one month after a sharp decline in ambient nitrate concentration, and carbon reserves were formed. In the deeper bed of M. pyrifera, nitrogen was abundant all year round and the production of the fronds reflected the seasonal pattern of light or water temperature. The nitrogen content of the tissue probably did not drop below a level that limited production, and no internal carbon reserves were accumulated.     

Will the application of Ammonium-Ferric-Hexacyano-Ferrate enhance the vertical migration of radiocaesium?

The consideration of a possible enhanced vertical migration of radiocaesium with the application of ammonium-ferric-hexacyano-ferrate (AFCF) as countermeasure, due to the colloidal nature of AFCF, made us set up a series of migration experiments. For the study two soil types were considered, which were either left unplanted or cultivated with ryegrass. Two AFCF concentrations, 1 and 10 g m^-2, and an untreated control were applied. A simple diffusion–convection model was fitted to the data.The application of AFCF did not enhance the downward migration of radiocaesium in the profile. Moreover, for an unplanted sandy soil the application of AFCF significantly retarded the migration: 10 g AFCF m^-2 decreased the convection term, V, from 0·78 to 0·42 cm a^-1 and the diffusion component, D, from 0·21 to 0·09 cm² a^-1. For all other experimental conditions (unplanted loamy soil, ryegrass cultivated sandy and loamy soil), the application of AFCF did not have any effect on radiocaesium migration. Since AFCF does not promote the vertical migration of radiocaesium, enhanced groundwater contamination is improbable.     

Baselines for land-use change in the tropics: application to avoided deforestation projects

Although forest conservation activities, particularly in the tropics, offer significant potential for mitigating carbon (C) emissions, these types of activities have faced obstacles in the policy arena caused by the difficulty in determining key elements of the project cycle, particularly the baseline. A baseline for forest conservation has two main components: the projected land-use change and the corresponding carbon stocks in applicable pools in vegetation and soil, with land-use change being the most difficult to address analytically. In this paper we focus on developing and comparing three models, ranging from relatively simple extrapolations of past trends in land use based on simple drivers such as population growth to more complex extrapolations of past trends using spatially explicit models of land-use change driven by biophysical and socioeconomic factors. The three models used for making baseline projections of tropical deforestation at the regional scale are: the Forest Area Change (FAC) model, the Land Use and Carbon Sequestration (LUCS) model, and the Geographical Modeling (GEOMOD) model. The models were used to project deforestation in six tropical regions that featured different ecological and socioeconomic conditions, population dynamics, and uses of the land: (1) northern Belize; (2) Santa Cruz State, Bolivia; (3) Paraná State, Brazil; (4) Campeche, Mexico; (5) Chiapas, Mexico; and (6) Michoacán, Mexico. A comparison of all model outputs across all six regions shows that each model produced quite different deforestation baselines. In general, the simplest FAC model, applied at the national administrative-unit scale, projected the highest amount of forest loss (four out of six regions) and the LUCS model the least amount of loss (four out of five regions). Based on simulations of GEOMOD, we found that readily observable physical and biological factors as well as distance to areas of past disturbance were each about twice as important as either sociological/demographic or economic/infrastructure factors (less observable) in explaining empirical land-use patterns. We propose from the lessons learned, a methodology comprised of three main steps and six tasks can be used to begin developing credible baselines. We also propose that the baselines be projected over a 10-year period because, although projections beyond 10 years are feasible, they are likely to be unrealistic for policy purposes. In the first step, an historic land-use change and deforestation estimate is made by determining the analytic domain (size of the region relative to the size of proposed project), obtaining historic data, analyzing candidate baseline drivers, and identifying three to four major drivers. In the second step, a baseline of where deforestation is likely to occur–a potential land-use change (PLUC) map—is produced using a spatial model such as GEOMOD that uses the key drivers from step one. Then rates of deforestation are projected over a 10-year baseline period based on one of the three models. Using the PLUC maps, projected rates of deforestation, and carbon stock estimates, baseline projections are developed that can be used for project GHG accounting and crediting purposes: The final step proposes that, at agreed interval (e.g., about 10 years), the baseline assumptions about baseline drivers be re-assessed. This step reviews the viability of the 10-year baseline in light of changes in one or more key baseline drivers (e.g., new roads, new communities, new protected area, etc.). The potential land-use change map and estimates of rates of deforestation could be re-done at the agreed interval, allowing the deforestation rates and changes in spatial drivers to be incorporated into a defense of the existing baseline, or the derivation of a new baseline projection.     

Mosaicism for trisomy 12: Four cases with varying outcomes

Trisomy 12 observed in chorionic villus sampling (CVS) may reflect generalized mosaicism or indicate mosaicism confined to only the placenta. In this report, four cases of trisomy 12 observed in CVS or cultured placental biopsies with varying outcomes are presented. Seven dinucleotide repeat polymorphisms for chromosome 12 were used to determine the chromosome 12 origins in the fetus or child and to delineate the mechanism(s) that gave rise to the trisomy. In two cases (cases A and C), the mosaicism was confined to the placenta, resulting in normal liveborns. Although, in one case, the molecular results suggested an apparent duplication of one paternal chromosome 12 in the placenta, normal biparental inheritance was found in the diploid fetal cell line in both cases. In two other cases (cases B and D), trisomy 12 was observed in both extraembryonic and fetal tissues. In one of these pregnancies, a child was born by Caesarean section at 37 weeks because of intrauterine growth retardation and oligohydramnios, and resulted in neonatal death. Molecular markers and fluorescence in situ hybridization (FISH) revealed low-level trisomy 12 mosaicism in the spleen. In the fourth case, fetal abnormalities were detected on ultrasound and low-level trisomy 12 mosaicism was observed in amniotic fluid cells using conventional cytogenetics and FISH. Molecular markers revealed a maternal meiosis I non-disjunction of chromosome 12 in DNA from a cultured placental biopsy. Although predicting the outcomes of pregnancies involving confined placental mosaicism remains difficult, molecular techniques are valuable tools for distinguishing uniparental from biparental disomy and mechanisms of mosaicism.     

Molecular cytogenetic analysis of term placentae suspected of mosaicism using fluorescence in situ hybridization

In first-trimester chorionic villus sampling (CVS) for prenatal diagnosis, abnormal chromosomal findings, such as mosaicism, trisomies, or suspect abnormal karyotypes, are found more frequently than at amniocentesis. The fact that these chromosomal abnormalities do not always reflect the fetal karyotype but may be restricted to the placenta is a major problem in diagnosis and counselling. In this paper we present the results of fluorescence in situ hybridization (FISH) studies on interphase nuclei of three term placentae investigated because of false-positive findings at first-trimester CVS. The chorionic villi of the first case showed a mosaic chromosome pattern involving a trisomy 10 cell line and a normal cell line, those of the second case a total trisomy 8 cell line, while in the third case a complete monosomy X was found. Follow-up amniocentesis in each of these three cases revealed a normal karyotype. By using FISH, we were able to confirm the presence of the aberrant cell lines, which were all confined to one part of the placenta. FISH on interphase nuclei allows the investigation of large numbers of cells for the existence of numerical chromosome aberrations in a quick and reliable way.     

Prenatal diagnosis in advanced maternal age. Amniocentesis or CVS,a patient's choice or lack of information?

Ninety-six women of advanced maternal age were interviewed about the way they obtained information on prenatal diagnosis and about how the decision was made as to what procedure was to be performed (transabdominal chorionic villus sampling (TA-CVS) or amnio-centesis). In the CVS group, women visited their physician or midwife earlier in pregnancy (mean 7.1 weeks) than those in the amniocentesis group (mean 10.7 weeks). The availability of prenatal diagnosis was not mentioned during the first antenatal visit in 55 per cent of women from the amniocentesis group as opposed to 25 per cent from the TA-CVS group. Approximately 40 per cent of women eligible for prenatal diagnosis did not receive any information from the referring body prior to counselling at our centre. Only 29 per cent of women who underwent amniocentesis had actually chosen this procedure; 71 per cent were too late to undergo TA-CVS at 12 weeks. It is concluded that information to the patient must be improved in order to ensure early referral for prenatal diagnosis.