Mandibular morphology, task specialization and bite mechanics in Pheidole ants (Hymenoptera:Formicidae)

Ants show remarkable ecological and evolutionary success due to their social life history and division of labour among colony members. In some lineages, the worker force became subdivided into morphologically distinct individuals (i.e. minor versus major workers), allowing for the differential performance of particular roles in the colony. However, the functional and ecological significance of these morphological differences are not well understood. Here, we applied finite element analysis (FEA) to explore the biomechanical differences between major and minor ant worker mandibles. Analyses were carried out on mandibles of two Pheidole species, a dimorphic ant genus. We tested whether major mandibles evolved to minimize stress when compared to minors using combinations of the apical tooth and masticatory margin bites under strike and pressure conditions. Majors performed better in pressure conditions yet, contrary to our expectations, minors performed better in strike bite scenarios. Moreover, we demonstrated that even small morphological differences in ant mandibles might lead to substantial differences in biomechanical responses to bite loading. These results also underscore the potential of FEA to uncover biomechanical consequences of morphological differences within and between ant workers

Development and reproductive performance of beef heifers supplemented with brown rice meal and/or protected fat on temperate grasslands

The response of energy supplementation was evaluated on the development and reproductive performance of beef heifers on temperate grasslands. Twenty-eight Charolais × Nellore heifers, with initial average age of 18 months and initial live weight of 274.9 kg were utilized. The animals were maintained on oat + ryegrass pasture and distributed in the following treatments: no supplementation (NS): heifers kept exclusively on pasture; MEG: supplementation with protected fat Megalac®; BRM: supplementation with brown rice meal; BRM+MEG: supplementation with BRM + protected fat. The average final weight of the heifers was of 403.4 kg and corresponded to 89.5% of the adult weight. The body condition of heifers increased linearly with daily increase of 0.012 points, correlating positively with the final weight. There was interaction between treatment and period for average daily weight gain. The highest daily weight gain, 1.395 kg, occurred in the first period when the animals were supplemented with BRM+MEG. In the last period, the NS animals presented the lowest daily weight gain, 0.888 kg. Supplementation with brown rice meal and/or protected fat does not interfere in the intake of pasture by heifers or increase the total intake of dry matter, not changing, therefore, the average daily weight gain at the end of the period of grazing. The daily weight gain does not change during supplementation. The use of temperate pasture with and without supplementation promotes the proper development of the structure and reproductive tract of heifers, benefiting the animal performance indexes in the first mating at 25-27 months of age

The development and future of reconstructive and microvascular surgery of the hand.

The hand is often thought of as a key discriminator in what makes humans human. The hand is both intricate and fascinating in its design and function, allowing humans to interact with their surroundings, and each other. Due to its use in manipulation of the person's environment, injury to the hand is common. Devastating hand injuries have a profound, physical, psychological, financial and socially crippling effect on patients. Advances in operative techniques and improvements in microscopes and instruments allowed Malt &McKhann to perform the first successful arm replantation in 1962 [1]. This was followed by a myriad of autologous free flaps of varying composition, that were discovered after the mapping of the cutaneous blood circulation by Taylor and Palmer [2] and Mathes & Nahai's classification of muscle flaps [3] providing us with countless options to harvest and transfer healthy, well vascularised tissues into areas of injury. Since the late sixties, with the emerging subspecialty of microvascular reconstruction, surgeons have had the technical ability to salvage many amputated parts, even entire limbs. The measure of functional outcomemust incorporate the evaluation and severity ofthe initial injury and the subsequent reconstructive surgeries [4]