Does Distance Among Colonies and Resource Availability Explain the Intercolonial Aggressiveness in Nasutitermes aff. coxipoensis?

Aggressive behaviour can ensure animal access to local resources. To reduce constant costs in the defence of territories, species could save energy with conflicts avoiding aggression with neighbour or in situations with abundance of resources. In the present study, we analysed the effect of distance among colonies and resource availability on the aggression level and responses to chemical cues of Nasutitermes aff. coxipoensis (Holmgren) (Termitidae: Nasutitermitinae). Manipulation of resource offer was conducted in the field, where nests with different distances were kept without addition of baits (control), with addition of three or 16 sugarcane baits/nest. After 3 months, aggressiveness, linear and Y-shaped trail-following bioassays were carried out with all pairwise combinations of colonies in each treatment. Our results showed that aggressive index of N. aff. coxipoensis was affected by the resource availability. However, individuals from colonies with 0 and 3 baits/nest showed a higher number of fighting with neighbours than those from non-neighbours colonies. Termite workers from colonies without baits (control) followed shorter distance in the linear trails compared to those from colonies with addition of baits. In all treatments, there was no preference of workers in relation to the choice of chemical cues from own or other colonies. The response of intercolonial aggressiveness in N. aff. coxipoensis seems to be resource-dependent. These results may contribute to the comprehension of the use of space by N. aff. coxipoensis and could be useful to explain patterns of termite co-occurrence at different spatial scales, from local (inside the nest-e.g. cohabitation of nests by inquilines) to regional (e.g. around the nest).

[Prevalence of rubella virus antibodies in pregnant women in two zones of Valle de Mexico]. / Prevalencia de anticuerpos para el virus de rubéola en mujeres gestantes de dos zonas del Valle de México.

The aim of this study was to determine the prevalence of specific antibodies against rubella virus in pregnant women from Iztapalapa and Nezahualcóyotl areas of the valley of Mexico, in order to evaluate susceptibility to this virus in these areas. Serum samples collected from 5535 women between 15 and 44 years old were studied by the hemaglutination inhibition test. 92.6% of positivity was obtained and no significant difference was observed between different age groups. The prevalence of rubella antibodies in pregnant women was 92.4% for Iztapalapa zone and 92.8% for Nezahualcóyotl. The titles of antibodies against rubella virus more frecuently presented were 1:16 (36.3%) and 1:32 (29.6%). The data obtained in this study suggest that women attending Medical Services of the Mexican Institute of Social Segurity in reproductive age from the Iztapalapa and Nezahualcóyotl areas, do not need massive vaccination against rubella virus.