Ontogeny of the osteocranium in the African catfish, Clarias gariepinus burchell (1822) (Siluriformes: Clariidae): Ossification sequence as a response to functional demands

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Comparative developmental osteology of the seahorse skeleton reveals heterochrony amongst Hippocampus sp. and progressive caudal fin loss

Background: Seahorses are well known for their highly derived head shape, prehensile tail and armoured body. They belong to the family of teleosts known as Syngnathidae, which also includes the pipefishes, pipehorses and seadragons. Very few studies have investigated the development of the skeleton of seahorses because larvae are extremely difficult to obtain in the wild and breeding in captivity is rarely successful. Here we compare the developmental osteology of Hippocampus reidi over an ontogenetic series spanning the first 93 days after release from the brood pouch to that of a smaller series of Hippocampus; namely H. subelongatus. Results: We compare the osteology in these two species over growth to the published description of the dwarf species, H. zosterae. We show that ossification onset in H. subelongatus is earlier than in H. reidi, despite similar sizes at parturition. Interestingly, the timing of development of the bony skeleton in H. zosterae is similar to that of the larger species, H. subelongatus. Furthermore, we show that the growth rate of all three species is similar up until about 30 days post pouch release. From this stage onwards in the life history, the size of the dwarf species H. zosterae remains relatively constant whilst the other two species continue growing with an accelerated growth phase. Conclusion: This data together with a phylogenetic assessment suggests that there has been a heterochronic shift (a delay) in the timing of ossification in H. reidi and accelerated bonedevelopment in H. zosterae. That is, H. zosterae is not a developmentally truncated dwarf species but rather a smaller version of its larger ancestor, "a proportioned dwarf" species. Furthermore, we show that caudal fin loss is incomplete in Hippocampus seahorses. This study shows that these three species of Hippocampus seahorses have evolved (either directly or indirectly) different osteogenic strategies over the last 20-30 million years of seahorse evolution

Evomimetics : the biomimetic design thinking 2.0

The consensus is that nature is a tremendous source of ideas for innovative designs that can meet various specific functional needs, relevant to society. Designs rely on structural, constructional, process-based and behavioral traits that all result from a natural trial-and-error cycle: evolution. Being one of the pillars of biomimicry, through billion years of evolution, nature has experimented and found what works and lasts, and what does not. Evidently, this has attracted scientists, especially engineers, trying to understand working natural designs, and translate them into applicable, working synthetic designs. The 'Biomimetic Design Method' forms the underlying conceptual framework to analytically decode biologically functions and designs. However, even though the evolutionary process is considered key to all this, it is generally overlooked in this conceptual thinking. The general assumption is that particular functions in organisms result from a natural selection process that optimized the underlying design for a particular function, thereby overlooking that an organism actually represents the possibly best compromise between all its functions needed to survive, to reproduce and to produce fit offspring. Many evolutionary processes thus yield suboptimal design components that, when put together, provide an optimized organismal design that manages to perform as good as needed, within a given environment. Such evolutionary limitations thus create possible pitfalls for bio-inspired design thinking. But, when considering them as a structural part of the design thinking process ('evomimetics'), they actually create opportunities for an improved translation of biology into optimally functioning designs. Using specific examples from evolutionary biology, these processes are explained, and recommendations are formulated

Saving the European eel : how morphological research can help in effective conservation management

The European eel (Anguilla anguilla) is a critically endangered species, whose recruitment stocks have declined to nearly 1% compared to the late 70s. An amalgam of factors is responsible for this, among them migration barriers, pollution, habitat loss, parasite infection, and overfishing. A lot of recent studies focus on aspects that can increase the mature silver eel escapement rate, such as identifying migration barriers and developing passageways or addressing the impact of pollution on the eel’s health. However, little attention is given to the eel’s morphology in function of management measures. Worryingly, less than 50% of the currently installed management plans reach their goals, strongly indicating that more information is needed about the eel’s ecology and behavior. Functional morphological studies provide insights on how species perform behaviors crucial for survival, such as feeding and locomotion, but also in how environmental changes can affect or limit such behaviors. Consequently, functional morphology represents an important biotic component that should be taken into account when making conservation decisions. Hence, here, we provide an overview of studies on the eel’s morphology that do not only demonstrate its relation with ecology and behavior, but also provide information for developing and installing proper and more specific management measures