First evidence of gregarious denning in opossums (Didelphimorphia, Didelphidae), with notes on their social behaviour.

The Didelphidae are considered solitary opossums with few social interactions, usually limited to mating-related or mother-pouch young interactions. Anecdotal reports suggest that additional interactions occur, including den sharing by a few individuals, usually siblings. Here, we report novel observations that indicate opossums are more social than previously thought. These include nest sharing by males and females of Marmosa paraguayana, Gracilinanus microtarsus and Marmosops incanus prior to the onset of the breeding season and without signs of sexual activity; this is taken to indicate early pair-bonding matching and cooperative nest building. We also recorded den sharing among recently weaned siblings of Didelphis aurita and Caluromys philander. In addition, we observed 13 individuals of Didelphis albiventris representing three age classes resting without agonistic interactions in a communal den. These are the first reports of gregarious behaviour involving so many individuals, which are either unrelated or represent siblings from at least two litters, already weaned, sharing the same den with three adults. Sociality in opossums is probably more complex than previously established, and field experimental designs combining the use of artificial nests with camera traps or telemetry may help to gauge the frequency and extent of these phenomena.

IGF2/ApaI polymorphism associated with birth weight in children of the region of Petrolina-PE, Brazil.

Insulin-like growth factor 2 (IGF2) gene has an important role in fetal growth. It was investigated association of the IGF2/ApaI polymorphism with low birth weight and normal birth weight (as control) in children attended in Hospital Dom Malan Petrolina, PE-Brazil. The genotype frequencies did not differ statistically between low birth weight (AA = 16.22%, AG = 43.24%, GG = 40.54%) and control (AA = 20% AG = 35%, GG= 45% groups) and the allele frequencies were not significantly different (p > 0.05).The observed genotype frequencies in both groups did not deviate significantly from Hardy-Weinberg equilibrium. Then, no significant correlation was found for this polymorphism in the population studied.