Ployandry versus polygyny versus parasites

Although social insect colonies are most easily conceptualized as consisting of a single, once-mated queen and her worker progeny, the number of queens per colony and the number of times queens mate varies broadly in ants and other social insects. Various hypotheses have been suggested for the resulting range of breeding systems and social organizations, respectively; one set of hypotheses relating to both queen number and mate number at the same time is a need for genetic variation, especially in relation to disease resistance. We here carry out a comparative analysis using phylogenetic information and, contrary to one non-phylogenetic previous study, we find that polyandry and polygyny are not significantly associated. However, the level of relatedness within colonies, a quantity affected by both polyandry and polygyny, is significantly associated with parasite loads: species with colonies with low relatedness levels have lower parasite loads. Given that, under the variance-reduction principle, selection on queens for mating frequency ought to continue even in polygynous colonies, we suggest that while parasite loads indeed seem to correlate with intra-colony genetic variability, the relationship to polyandry and polygyny may be complex and requires considerably more experimental investigation.     

Axial versus Appendicular: Constraint versus Selection

SYNOPSIS.Constraint theory has suffered from its many and varyingdefinitions and from repeated confusion with the action of selection.Constraints are difficult to isolate, more difficult to quantify,and their consequences may be simulated by the action of agentssuch as stabilizing selection. This paper presents an alternativemethod of constraint analysis using a simple one-dimensionalmeasurement. A total of 29 skeletal elements from 15 speciesrepresenting 11 orders of mammals were measured for length andnormalized for body mass, after which means, standard deviations,and variances were generated. A coefficient of variation analysiswas performed to normalize for mean element length. The axialskeleton was found to be less variable than the appendicular.The appendicular demonstrated a trend where the more distalelements were the most variable, and variation decreased withmore proximal positions. The three most variable of the 29 elementswere finger V, toe V, and metacarpal V. In summary, the axialskeleton was found to be more conservative in the lengths ofits elements, the more distal appendicular elements were lessconstrained than proximal ones and these constraints were probablythe results of genetic, developmental, and mechanical factors.It is also proposed that stabilizing selection played some rolein maintaining the curb on length variance in these structures,based on mechanical performance. The results of this study areintended to promote discussion of alternative methods of constraintanalysis.     

Lymphocytes apoptosis: young versus aged and humans versus rats

This paper deals with a comparative study of lymphocyte apoptosis in young versus aged and humans versus rats. Apoptotic rate achieved by the use of different apoptogenic inducers, acting at different cellular levels, and cell surface modifications were analyzed. The results showed that aged human lymphocytes and freshly isolated rat lymphocytes were more prone to undergo apoptosis. Therefore, the same apoptotic signal is recognized by human and rat lymphocytes, but the extent of the answer is related to the species, to the intensity of the apoptotic stimulus and to the metabolic/developmental condition of the cells. Surface modifications (lipids and glycans), typical of apoptosis, were observed. Our data showed that cell surface changes are species and age dependent. They are early events, progressively achieved in the course of the apoptotic process involving lateral membrane movements of molecules.