Visual Navigation In The Neotropical Ant Odontomachus Hastatus (formicidae, Ponerinae), A Predominantly Nocturnal, Canopy-dwelling Predator Of The Atlantic Rainforest.

The arboreal ant Odontomachus hastatus nests among roots of epiphytic bromeliads in the sandy forest at Cardoso Island (Brazil). Crepuscular and nocturnal foragers travel up to 8m to search for arthropod prey in the canopy, where silhouettes of leaves and branches potentially provide directional information. We investigated the relevance of visual cues (canopy, horizon patterns) during navigation in O. hastatus. Laboratory experiments using a captive ant colony and a round foraging arena revealed that an artificial canopy pattern above the ants and horizon visual marks are effective orientation cues for homing O. hastatus. On the other hand, foragers that were only given a tridimensional landmark (cylinder) or chemical marks were unable to home correctly. Navigation by visual cues in O. hastatus is in accordance with other diurnal arboreal ants. Nocturnal luminosity (moon, stars) is apparently sufficient to produce contrasting silhouettes from the canopy and surrounding vegetation, thus providing orientation cues. Contrary to the plain floor of the round arena, chemical cues may be important for marking bifurcated arboreal routes. This experimental demonstration of the use of visual cues by a predominantly nocturnal arboreal ant provides important information for comparative studies on the evolution of spatial orientation behavior in ants. This article is part of a Special Issue entitled: Neotropical Behaviour.

Stromal Myofibroblasts In Squamous Cell Carcinoma Of The Tongue In Young Patients - A Multicenter Collaborative Study.

The purpose of this study was to evaluate the presence of myofibroblasts, frequently associated with a more aggressive neoplastic behavior, in oral tongue squamous cell carcinoma (TSCC) of young patients and to compare with the distribution observed in older patients. Tumor samples from 29 patients younger than 40 years old affected by TSCC were retrieved and investigated for the presence of stromal myofibroblasts by immunohistochemical reactions against α smooth muscle actin, and the results obtained were compared to TSCC cases affecting older patients. No positive reaction could be found in the stromal areas devoid of neoplastic tissue, whereas myofibroblasts were present in 58.6% of the lesions in young patients and in 75.9% of the older ones. No significant difference was found when comparing the invasive front and the overall stroma of both groups, and no correlation could be obtained with stromal α smooth muscle actin expression, higher tumor grades or clinical stage (P > .05). There was no significant difference between the presence of stromal myofibroblasts of TSCC affecting young and old individuals.