Joseph Groenke

Many developmental and metabolic effects of growth hormone (GH) on vertebrate life history traits have been widely studied in biological and biomedical contexts. The scope of alterations in GH/GH receptor (GHR) interactions has generally focused on molecular, cellular, histological, and physiological framing, leaving a gap in understanding of how the cumulative organism‐ and lifespan‐scale manifestations of morphological changes attributable to GH/GHR perturbations may both be influenced by and also influence smaller‐scale study results. The pilot study conducted herein used micro‐computed tomography (μCT) to survey and characterize the axial and appendicular skeletons of adult male and female bGH (transgenic overexpression of bovine GH) mice and to compare them with those of age‐ and sex‐matched wild‐type (WT) controls. Male and female bGH mice in our sample were larger (by linear measurements of skeletal elements) and leaner but not heavier than their WT counterparts. bGH mice exhibit thoracic kyphosis and radiographically detectable incipient sacralization of the last lumbar vertebra, as well as robust and altered muscle attachment sites in both girdle and long bones, re‐orientation of the acetabulum, and dysmorphology of the femur at both hip and knee joints. bGH mice generally lack clear, radiologically determinable differentiation of long bone growth plates and bear larger and differently proportioned sesamoids at the elbow and knee. They are also preferentially subject to the accumulation of inferred heterotopic calcification (IHC) and other radiodense soft tissue (RST) around joints and entheses. Female bGH mice exhibit variable and aberrant morphology in the humerus, innominate, and femur not seen in other groups, and show the most size and shape variation within the four genotype × sex groupings. Our survey illustrates widespread musculoskeletal impacts of excessive GH into adulthood in the model. These data provide an initial whole‐skeleton framework for further efforts characterizing molecular‐, cellular‐, and tissue‐scale alterations ultimately influencing the bGH mouse model skeletal phenotype. This pilot work serves to contextualize future preclinical studies as well as broader investigations into how GH and its metabolic cascade may affect vertebrate morphological and histological development, shape and size disparity, and dimorphism.

Postcranial skeletal pneumaticity is a phenomenon in birds in which epithelial extensions of the lung–air sac system aerate bones. Detailed development of this phenotype remains largely unknown. Here, we investigate changes in bone, soft tissue and air space volume in the developing humerus of turkeys using computed tomography and micro-computed tomography. Employing a two-phase approach, we first tracked humeral air space development in vivo in domesticated turkeys between week 10 (W10) and W18 post-hatch. In phase 2, we analysed air space and marrow volume change through the first 22 weeks of post-hatch development. Our results indicate that pneumatization of the humerus begins between W2 and W4 post-hatch, with air spaces expanding distally from the proximal humerus. Internal air space expands most rapidly between W7 and W9, with maximal volume reached at W15. Increased marrow growth occurs between W13 and W19, coincident with stabilization and a potential decline in relative air space volume. Our study highlights a dynamic relationship between bone, marrow and pneumatic epithelium, suggesting pneumaticity expression is likely impacted by both within-bone tissue growth dynamics and extrinsic factors related to forelimb function. This work provides the necessary gross anatomical framework for subsequent analyses of tissue-level and cellular mechanisms related to the pneumatization process.This article is part of the theme issue ‘The biology of the avian respiratory system’.

Fossils representing Cretaceous lineages of crown clade birds (Aves) are exceptionally rare but are crucial to elucidating major ecological shifts across early avian divergences. Among the earliest known putative crown birds is Vegavis iaai^1,2,3,4,5, a foot-propelled diver from the latest Cretaceous (69.2–68.4 million years ago)⁶ of Antarctica with controversial phylogenetic affinities^2,7,8,9,10. Initially recovered by phylogenetic analyses as a stem anatid (ducks and closely related species)^1,2,11, Vegavis has since been recovered as a stem member of Anseriformes (waterfowl)^7,8,9, or outside Aves altogether¹⁰. Here we report a new, nearly complete skull of Vegavis that provides new insight into its feeding ecology and exhibits morphologies that support placement among waterfowl within crown-group birds. Vegavis has an avian beak (absence of teeth and reduced maxilla) and brain shape (hyperinflated cerebrum and ventrally shifted optic lobes). The temporal fossa is well excavated and expansive, indicating that this bird had hypertrophied jaw musculature. The beak is narrow and pointed, and the mandible lacks retroarticular processes. Together, these features comprise a feeding apparatus unlike that of any other known anseriform but like that of other extant birds that capture prey underwater (for example, grebes and loons). The Cretaceous occurrence of Vegavis, with a feeding ecology unique among known Galloanserae (waterfowl and landfowl), is further indication that the earliest anseriform divergences were marked by evolutionary experiments unrepresented in the extant diversity^3,11,12,13.