Evolution of the secretoglobins: a genomic and proteomic view

Mouse salivary androgen-binding protein (ABP) is a member of the newly erected secretoglobin family, no member of which has yet been assigned an indisputable function. We have suggested a role for ABP in mate selection behaviour and sexual isolation. Although this has been a particularly attractive hypothesis given the evidence for strong positive selection on its alpha subunit gene, Abpa , we have held out the possibility that there might be an as-yet-undiscovered primary function for ABP. This is particularly important in light of its membership in the secretoglobin family, and we are pursuing the broader issue of shared functions of the secretoglobins with genomic and bioinformatic studies. Here we present as complete a comparison as possible of the secretoglobins in the genomes of three species of mammals: mouse, rat and human, and we compare the protein sequences and their potential evolutionary relationships. We suggest that the secretoglobins can be divided into at least five families. In rodent and human genomes, these gene families are found in two main clusters that are syntenic between rat and mouse. Humans have only the three families that are found within the uteroglobin/clara cluster, because no ABP-containing secretoglobin cluster has yet been identified.  © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 84 , 493–501.     

Scaling of sensorimotor control in terrestrial mammals

Sensorimotor control is greatly affected by two factors—the time it takes for an animal to sense and respond to stimuli (responsiveness), and the ability of an animal to distinguish between sensory stimuli and generate graded muscle forces (resolution). Here, we demonstrate that anatomical limitations force a necessary trade-off between responsiveness and resolution with increases in animal size. To determine whether responsiveness is prioritized over resolution, or resolution over responsiveness, we studied how size influences the physiological mechanisms underlying sensorimotor control. Using both new electrophysiological experiments and existing data, we determined the maximum axonal conduction velocity (CV) in animals ranging in size from shrews to elephants. Over the 100-fold increase in leg length, CV was nearly constant, increasing proportionally with mass to the 0.04 power. As a consequence, larger animals are burdened with relatively long physiological delays, which may have broad implications for their behaviour, ecology and evolution, including constraining agility and requiring prediction to help control movements.     

The evolution of the mammalian pharynx

Data derived from studies of comparative anatomy, development, neuroanatomy, behaviour and the reconstruction of fossils are combined to evaluate the evolution of the oral-pharyngeal region in mammals. An important event in the evolution of the mammalian feeding apparatus was the development of a novel neuromuscular apparatus, consisting of a large series of striated muscles. The most important of these muscles are the pharyngeal elevators and constrictors, which appear to be without homologues in other amniotes. In addition to considerable peripheral neural and muscular modifications, the motor nuclei of the brain stem in mammals exhibit significant differences from other amniotes. The morphological features characteristic of mammals are reflected in behavioural differences, most significantly during swallowing and suckling. The neuromuscular changes in the mammalian oral-pharyngeal apparatus are at least as extensive as those involving the masticatory system, and have importance far beyond the separation of the airway and foodway, the foci of most previous studies. The hypothesis of neuromuscular conservativism in the evolution of the mammalian feeding mechanism is considered and it is concluded that few data exist to support this hypothesis.     

FATTY ACID COMPOSITION OF FATS FROM THE URUGUAYAN FUR SEAL (ARCTOCEPHALUS AUSTRALIS ZIMMERMANN)

The composition and properties of commercial oil collected from Uruguayan fur seals ( Arctocephalus australis Zimmermann) during 1985, 1986 and 1987 are reported. Oil recovered from some organs (kidney, heart, liver) and blubber were also analyzed. All have compositions similar to oils from other marine animals in commercial use, containing high percentages of long chain and polyunsaturated fatty acids.