No abstract

Billfishes are large pelagic fishes that have an extreme elongation of the upper jaw bones forming the rostrum. Recent kinematic and biomechanical studies show the rostrum to be associated to feeding, however, it is less clear how the wide range of morphologies present among billfish may affect their striking behavior. In this study, we aim to assess the mechanical performance of different rostrum morphologies under loads that simulate feeding and to test existing hypotheses of species-specific feeding behaviors. We use finite element analysis (FEA)-a physics-based method that predicts patterns of stress and strain in morphologically complex structures under specified boundary conditions-to test hypotheses on the form and mechanical performance of billfish rostra. Patterns of von Mises stress and total strain energy suggest that distinct rostral morphologies may be functionally segregated. The rounder blue marlin rostrum may be better suited for a wide range of slashing motions to disable prey, whereas the more flattened swordfish rostrum appears to be more specialized for lateral swiping during prey capture. The almost homogenous stress distribution along each rostrum implies their possible use as a predatory weapon regardless of morphological differences between species. The mechanical implications of other less commonly reported behaviors such as spearing are discussed, as well as the potential impact of hydrodynamics in shaping the evolution of the rostrum in this lineage. Anat Rec, 303:44-52, 2020.

When observing children playing rhythm echoes with percussion instruments it was noticed that they can repeat a certain number of sounds accurately and that this number increases depending on the children's age and musical experience. It was thought likely that this number has a direct correlation not only with the children's stage of motor development, but also with the development of numeracy, which includes working memory capacity and conservation ability. Moreover, this raised the question of whether we can make an analogy between the children's ability to enumerate homogeneous and heterogeneous sets of objects and their ability to perceive and repeat rhythm patterns that could be made up of both similar and/or different sounds in terms of duration and intensity (accent), even if produced by the same instrument. To test this hypothesis, three groups made up of 10 children Á 2Á4-year-olds (N 030) Á were tested using a traditional task for early numeracy assessment and on their ability to perform a series of rhythm patterns by imitation. As expected, the study found a correlation between number concept development and the performing accuracy of rhythm patterns. Implications for music education strategies and materials are also discussed.