Does predation control adult sex ratios and longevities in marine pelagic copepods?

We assess the causes of adult sex ratio skew in marine pelagic copepods by examining changes in these ratios between the juveniles and adults, sexual differences in juvenile stage durations, and mortality rates of adults in the field and laboratory (when free from predators). In the field, late copepodite stages (CIV and CV) commonly have sex ratios that are either not significantly different from equity (1 : 1), or slightly male biased. By contrast, in adults, these ratios are commonly significantly biased toward female dominance. Sex ratio skews are therefore primarily attributable to processes in adults. Members of the non-Diaptomoidea have especially skewed adult ratios; in the members Oithonidae and Clausocalanidae this is not generated from differences between male and female adult physiological longevity (i.e., laboratory longevity when free of predators). In the genera Acartia, Oithona, and Pseudocalanus, we estimate that predation mortality contributed ≥ 69% of the field mortality rate in adult males, whereas in Acartia, Oithona, and Calanus adult females, this is ≥ 36%.We conclude that (1) adult sex ratio skew in pelagic copepods is primarily due to differential mortality of the sexes in the adult stage and not in juveniles, (2) mortality rates of adult Acartia, Pseudocalanus, and Oithona are dominated by predation mortality rather than physiological longevity (except under extreme food limitation), and (3) in Pseudocalanus and Oithona, elevated mortality rates in adult males to females is predominantly due to higher predation on males. Our work demonstrates that we now need to develop a more comprehensive understanding of the importance of feeding preferences in predators. Continue reading full article

Effect of supplementation silage ("Festuca dolichophylla, Avena sativa and Vicia sativa") on weight gain and mortality in adult alpacas ("Vicugna pacos")

This study was conducted in order to evaluate the effect of supplementation with silage (Festuca dolichophylla, Avena sativa and Vicia sativa) on weight gain and mortality in adult alpacas, during the months of dry season (June to August) in Huancavelica region. 300 female alpacas 3 and 4 years of age (physiological state: pregnant) were used, which were assigned to the following treatments: SP, grazing only PSE15, grazing plus supplementation of 1.5 kg of silage. Alpacas were supplemented once daily. In each alpaca they were recorded live weight at the beginning and end of the experiment. The weight gain was -0.02 y 2.05 kg for SP and PSE15 respectively (p <0.001) treatments. Mortality was 5.3% and 2.7% for SP and PSE15 respectively (p=0.073) treatments. It can be concluded under the conditions of this trial silage supplementation has effect on weight gain and maybe also on mortality in alpacas.

Vasoactive intestinal polypeptide (VIP) and VPAC1 receptor in adult human dental pulp in relation to caries

Objective: To quantitatively measure VIP levels and to qualitatively study the distribution of VIP fibres and demonstrate the presence of the VPAC1 receptor in human dental pulp from carious and non-carious adult human teeth. Design: Dental pulp samples were collected from non-carious, moderately carious and grossly carious adult human teeth. VIP levels were determined using radioimmunoassay. The distribution of VIP fibres was studied using immunohistochemistry. The VPAC1 receptor protein expression was determined by Western blotting. Results: VIP levels were found to be significantly elevated in the dental pulp of moderately carious compared with non-carious (p = 0.0032) or grossly carious teeth (p = 0.0029). The distribution of VIP fibres was similar in non-carious and carious teeth, except that nerve bundles appeared thicker in the pulp samples from carious compared with non-carious teeth. Western blotting indicated that the VPAC1 receptor proteins were detected in similar levels in pooled dental pulp samples from both carious and non-carious teeth. Conclusion: It is concluded that quantitative changes in the levels of VIP in human dental pulp during the caries process and the expression of VPAC1 receptor proteins in membrane extracts from carious and non-carious teeth suggests a role for VIP in modulating pulpal health and disease. © 2006 Elsevier Ltd. All rights reserved.