RESUMEN
The New World suboscines (Passeriformes and Tyrannides) are one of the biggest endemic vertebrate radiations in South America, including the families Furnariidae and Tyrannidae. Avian brain morphology is a reliable proxy to study their evolution. The aim of this work is to elucidate whether the brains of these families reflect the ecological differences (e.g., feeding behavior) and to clarify macroevolutionary aspects of their neuroanatomy. Our hypotheses are as follows: Brain size is similar between both families and with other Passeriformes; brain morphology in Tyrannides is the result of the pressure of ecological factors; and brain disparity is low since they share ecological traits. Skulls of Furnariidae and Tyrannidae were micro-computed tomography-scanned, and three-dimensional models of the endocast were generated. Regression analyses were performed between brain volume and body mass. Linear and surface measurements were used to build phylomorphospaces and to calculate the amount of phylogenetic signal. Tyrannidae showed a larger brain disparity than Furnariidae, although it is not shaped by phylogeny in the Tyrannides. Furnariidae present enlarged Wulsts (eminentiae sagittales) but smaller optic lobes, while in Tyrannidae, it is the opposite. This could indicate that in Tyrannides there is a trade-off between the size of these two visual-related brain structures.
Asunto(s)
Passeriformes , Animales , Humanos , Passeriformes/anatomía & histología , Filogenia , Microtomografía por Rayos X , Encéfalo/anatomía & histologíaRESUMEN
We used three-dimensional digital models to investigate the brain and endosseous labyrinth morphology of selected Neotropical Piciformes (Picidae, Ramphastidae, Galbulidae and Bucconidae). Remarkably, the brain morphology of Galbulidae clearly separates from species of other families. The eminentiae sagittales of Galbulidae and Bucconidae (insectivorous with high aerial maneuverability abilities) are smaller than those of the toucans (scansorial frugivores). Galbula showed the proportionally largest cerebellum, and Ramphastidae showed the least foliated one. Optic lobes ratio relative to the telencephalic hemispheres showed a strong phylogenetic signal. Three hypotheses were tested: (a) insectivorous taxa that need precise and fast movements to catch their prey, have well developed eminentiae sagittales compared to fruit eaters, (b) species that require high beak control would show larger cerebellum compared to other brain regions and higher number of visible folia and (c) there are marked differences between the brain shape of the four families studied here that bring valuable information of this interesting bird group. Hypotheses H1 and H2 are rejected, meanwhile H3 is accepted.
Asunto(s)
Aves/anatomía & histología , Encéfalo/anatomía & histología , Filogenia , Cráneo/anatomía & histología , Animales , Aves/fisiología , Oído Interno/anatomía & histología , Femenino , Masculino , Cráneo/fisiologíaRESUMEN
Here we address the morphology of the cranial musculoskeletal in the South American Band-winged nightjar (Systellura longirostris, Caprimulgiformes, Aves) with the focus upon in how the mouth closure and opening mechanism is. Bony characters such as the thinness of the interorbital septum and the reduction of the postorbital process co-assist the location of large eyes, although correlations between eye size brain mass and body mass revealed that the Band-winged nightjar's eye is bigger than expected. The reduction of the processus orbitalis of the os quadratum would allow the great mouth opening given by a large maxillary protraction. Systellura longirostris shows a zona flexoria intramandibularis with marked reduction in bone ossification that helps to the lateral opening of the jaws. In Systellura longirostris, the m. pseudotemporalis profundus, m. adductor mandibulae externus superficialis, and m. adductor mandibulae externus medialis are absent. The adductor muscles represent 66.614% of the total mandibular muscle mass. Physiological Cross Sectional Area (PCSA) values of the adductor muscles are high and the fibers are relatively long compared to other zoophagous birds, another condition that favors adduction. The m. adductor mandibulae externus profundus is the largest jaw muscle regarding its mass but its osteological correlate on the neurocranium, the fossa temporalis, is absent. In the absence of some muscles in charge of the bill closing, an elastic instability model for jaw closing is proposed.
Asunto(s)
Aves/anatomía & histología , Conducta Alimentaria/fisiología , Mandíbula/anatomía & histología , Músculo Esquelético/anatomía & histología , Cráneo/anatomía & histología , Animales , Pico , Aves/fisiología , Mandíbula/fisiología , Músculo Esquelético/fisiología , Cráneo/fisiologíaRESUMEN
The cranio-mandibular complex is an important structure involved in food capture and processing. Its morphology is related to the nature of the food item. Jaw muscles enable the motion of this complex and their study is essential for functional and evolutionary analysis. The present study compares available behavioral and dietary data obtained from the literature with novel results from functional morphological analyses of the cranio-mandibular complex of the Guira cuckoo (Guira guira) to understand its relationship with the zoophagous trophic habit of this species. The bite force was estimated based on muscle dissections, measurements of the physiological cross-sectional area, and biomechanical modeling of the skull. The results were compared with the available functional morphological data for other birds. The standardized bite force of G. guira is higher than predicted for exclusively zoophagous birds, but lower than for granivorous and/or omnivorous birds. Guira guira possesses the generalized jaw muscular system of neognathous birds, but some features can be related to its trophic habit. The external adductor muscles act mainly during food item processing and multiple aspects of this muscle group are interpreted to increase bite force, that is, their high values of muscle mass, their mechanical advantage (MA), and their perpendicular orientation when the beak is closed. The m. depressor mandibulae and the m. pterygoideus dorsalis et ventralis are interpreted to prioritize speed of action (low MA values), being most important during prey capture. The supposed ecological significance of these traits is the potential to widen the range of prey size that can be processed and the possibility of rapidly capturing agile prey through changes in the leverage of the muscles involved in opening and closing of the bill. This contributes to the trophic versatility of the species and its ability to thrive in different habitats, including urban areas.