Malpighi, Swammerdam and the colourful silkworm: replication and visual representation in early modern science

Positioning Van Leeuwenhoek's microscopes in seventeenth-century microscopic practice

The self-made nature of Antoni van Leeuwenhoek's discoveries and microscopes tends to obscure the rich and dynamic seventeenth-century culture of microscopy that preceded his work. Rather than being limited by available magnifications, seventeenth-century microscopy was shaped by philosophical paradigms, visual and preparation techniques, and observation conditions. Taking into account new insights into his lens making methods, a comparison of Van Leeuwenhoek's methodology with seventeenth-century predecessors reveals, on the one hand, how his work was rooted in existing traditions, while on the other hand it makes us appreciate his innovations better. Van Leeuwenhoek elegantly turned the viewing practice associated with high-magnification microscopy into a convincing narrative. In doing so, he reaffirmed the central role of the microscope in the seventeenth-century inquiry of nature. This allowed him to open up new vistas and become the founder of microbiology.

Microfluidic Surgery in Single Cells and Multicellular Systems

Microscale surgery on single cells and small organisms has enabled major advances in fundamental biology and in engineering biological systems. Examples of applications range from wound healing and regeneration studies to the generation of hybridoma to produce monoclonal antibodies. Even today, these surgical operations are often performed manually, but they are labor intensive and lack reproducibility. Microfluidics has emerged as a powerful technology to control and manipulate cells and multicellular systems at the micro- and nanoscale with high precision. Here, we review the physical and chemical mechanisms of microscale surgery and the corresponding design principles, applications, and implementations in microfluidic systems. We consider four types of surgical operations: (1) sectioning, which splits a biological entity into multiple parts, (2) ablation, which destroys part of an entity, (3) biopsy, which extracts materials from within a living cell, and (4) fusion, which joins multiple entities into one. For each type of surgery, we summarize the motivating applications and the microfluidic devices developed. Throughout this review, we highlight existing challenges and opportunities. We hope that this review will inspire scientists and engineers to continue to explore and improve microfluidic surgical methods.

Revealing the respiratory system of the coffee berry borer (Hypothenemus hampei; Coleoptera: Curculionidae: Scolytinae) using micro-computed tomography

The coffee berry borer (Hypothenemus hampei) is the most economically important insect pest of coffee globally. Micro-computed tomography (micro-CT) was used to reconstruct the respiratory system of this species for the first time; this is the smallest insect (ca. 2 mm long) for which this has been done to date. Anatomical details of the spiracles and tracheal tubes are described, images presented, and new terms introduced. The total volume and the relationship between tracheal lumen diameter, length and volume are also presented. The total length of the tracheal tubes are seventy times the length of the entire animal. Videos and a 3D model for use with mobile devices are included as supplementary information; these could be useful for future research and for teaching insect anatomy to students and the public in general.

Cooking up the perfect insect: Aristotle's transformational idea about the complete metamorphosis of insects

Aristotle made important contributions to the study of developmental biology, including the complete metamorphosis of insects. One concept in particular, that of the perfect or complete state, underlies Aristotle's ideas about metamorphosis, the necessity of fertilization for embryonic development, and whether morphogenesis involves an autonomous process of self-assembly. Importantly, the philosopher erroneously views metamorphosis as a necessary developmental response to lack of previous fertilization of the female parent, a view that is intimately connected with his readiness to accept the idea of the spontaneous generation of life. Aristotle's work underpins that of the major seventeenth century students of metamorphosis, Harvey, Redi, Malpighi and Swammerdam, all of whom make frequent reference to Aristotle in their writings. Although both Aristotle and Harvey are often credited with inspiring the later prolonged debate between proponents of epigenesis and preformation, neither actually held firm views on the subject. Aristotle's idea of the perfect stage also underlies his proposal that the eggs of holometabolous insects hatch 'before their time', an idea that is the direct precursor of the much later proposals by Lubbock and Berlese that the larval stages of holometabolous insects are due to the 'premature hatching' from the egg of an imperfect embryonic stage. This article is part of the theme issue 'The evolution of complete metamorphosis'.

Fossils and the Evolution of the Arthropod Brain

The discovery of fossilized brains and ventral nerve cords in lower and mid-Cambrian arthropods has led to crucial insights about the evolution of their central nervous system, the segmental identity of head appendages and the early evolution of eyes and their underlying visual systems. Fundamental ground patterns of lower Cambrian arthropod brains and nervous systems correspond to the ground patterns of brains and nervous systems belonging to three of four major extant panarthropod lineages. These findings demonstrate the evolutionary stability of early neural arrangements over an immense time span. Here, we put these fossil discoveries in the context of evidence from cladistics, as well as developmental and comparative neuroanatomy, which together suggest that despite many evolved modifications of neuropil centers within arthropod brains and ganglia, highly conserved arrangements have been retained. Recent phylogenies of the arthropods, based on fossil and molecular evidence, and estimates of divergence dates, suggest that neural ground patterns characterizing onychophorans, chelicerates and mandibulates are likely to have diverged between the terminal Ediacaran and earliest Cambrian, heralding the exuberant diversification of body forms that account for the Cambrian Explosion.

Leibniz, the microscope and the concept of preformation

In recent years a certain emphasis has been put by some scholars on Leibniz's concern about empirical sciences and the relations between such concern and the development of his mature metaphysical system. In this paper I focus on Leibniz's interest for the microscope and the astonishing discoveries that such instrument made possible in the field of the life sciences during the last part of the Seventeenth century. The observation of physical bodies carried out by the "magnifying glasses" revealed a matter swarming everywhere with life and activity, contrary to the cartesian and atomistic view of matter as something sterile and passive. Moreover, the discovery of uncountable complete "animalcula" living in the smallest drop of water provided evidence for the idea of the preformation of every organism. During his lifetime, Leibniz was extremely watchful about the new microscopical discoveries and came into contact with some of the major "observers" of his time, such as Hooke, Leeuwenhoek, Swammerdam and Malpighi. Relying both on some passages in Leibniz's texts and on recent critical studies, I will argue that important aspects of his metaphysics have been strongly affected by the empirical observation of the "invisible world" which the microscope made possible. In the last part of the paper I show how the concept of "preformation", originally drawn from the context of the life sciences, comes to play in Leibniz's philosophy a very general role, going far beyond the scope of biology and shaping important aspects of his overall philosophical system.

Shaping up for action: the path to physiological maturation in the renal tubules of Drosophila

The Malpighian tubule is the main organ for excretion and osmoregulation in most insects. During a short period of embryonic development the tubules of Drosophila are shaped, undergo differentiation and become precisely positioned in the body cavity, so they become fully functional at the time of larval hatching a few hours later. In this review I explore three developmental events on the path to physiological maturation. First, I examine the molecular and cellular mechanisms that generate organ shape, focusing on the process of cell intercalation that drives tubule elongation, the roles of the cytoskeleton, the extracellular matrix and how intercalation is coordinated at the tissue level. Second, I look at the genetic networks that control the physiological differentiation of tubule cells and consider how distinctive physiological domains in the tubule are patterned. Finally, I explore how the organ is positioned within the body cavity and consider the relationship between organ position and function.

From Galvani to patch clamp: the development of electrophysiology

The development of electrophysiology is traced from the early beginnings represented by the work of the Dutch microscopist, Jan Swammerdam, in the 17th century through the first notion of an aqueous transmembrane pore as a substrate of excitability made by Luigi Galvani in late 18th century to the invention late in the 20th century of the patch-clamp technique by Erwin Neher and Bert Sakmann.

Timeline: exorcizing the animal spirits: Jan Swammerdam on nerve function

For more than 1,500 years, nerves were thought to function through the action of 'animal spirits'. In the seventeenth century, René Descartes conceived of these 'spirits' as liquids or gases, and used the idea to explain reflex action. But he was rapidly proven wrong by a young Dutchman, Jan Swammerdam. Swammerdam's elegant experiments pioneered the frog nerve muscle preparation and laid the foundation of our modern understanding of nerve function.