Swim-Training Changes the Spatio-Temporal Dynamics of Skeletogenesis in Zebrafish Larvae (Danio rerio)

Fish larvae experience many environmental challenges during development such as variation in water velocity, food availability and predation. The rapid development of structures involved in feeding, respiration and swimming increases the chance of survival. It has been hypothesized that mechanical loading induced by muscle forces plays a role in prioritizing the development of these structures. Mechanical loading by muscle forces has been shown to affect larval and embryonic bone development in vertebrates, but these investigations were limited to the appendicular skeleton. To explore the role of mechanical load during chondrogenesis and osteogenesis of the cranial, axial and appendicular skeleton, we subjected zebrafish larvae to swim-training, which increases physical exercise levels and presumably also mechanical loads, from 5 until 14 days post fertilization. Here we show that an increased swimming activity accelerated growth, chondrogenesis and osteogenesis during larval development in zebrafish. Interestingly, swim-training accelerated both perichondral and intramembranous ossification. Furthermore, swim-training prioritized the formation of cartilage and bone structures in the head and tail region as well as the formation of elements in the anal and dorsal fins. This suggests that an increased swimming activity prioritized the development of structures which play an important role in swimming and thereby increasing the chance of survival in an environment where water velocity increases. Our study is the first to show that already during early zebrafish larval development, skeletal tissue in the cranial, axial and appendicular skeleton is competent to respond to swim-training due to increased water velocities. It demonstrates that changes in water flow conditions can result into significant spatio-temporal changes in skeletogenesis

Secrecy, Industry and Science. French Glassmaking in the Eighteenth Century

Glass has always played a crucial role in directing the investigation of natural phenomena onto revolutionary and innovative paths. Since antiquity philosophers of nature perceived the peculiar quality of this material and their increasing attention to the extraordinarily rich and varied productions made by craftsmen after the introduction of glassblowing techniques reveal the special status glass had in the economy and culture of the Roman Empire. Because of its chemical nature, large scale production of glass was a difficult technological process which required, in addition to dexterity, a broad knowledge of different operations and devices. The fusion of glass requires high temperatures that can only be obtained with the construction of special furnaces and crucibles, combined with the accurate use of salts, namely soda and potash, which enables to decrease the degree of glass\u2019 fusion