Evaluation of the functional capabilities of fins and limbs for moving on land: insights into the invasion of land by tetrapods

Transitions to novel habitats present different adaptive challenges, producing captivating examples of how functional innovations of the musculoskeletal system influence phenotypic divergence and adaptive radiations. One intriguing example is the transition from aquatic fishes to tetrapods. Recent technological advances and discoveries of critical fossils have catapulted our understanding on how fishes gave rise to terrestrial vertebrates. Considerable attention has been paid to legged locomotion on land, but given that the first tetrapods were aquatic, limbs did not evolve primarily for terrestriality. How, then, is the locomotor function of limbs different from fins? Extant amphibious fishes demonstrate that fins can be used on land, and anatomical analyses of the fish relatives of early stem tetrapods indicate that the appendicular bones of fishes could be quite robust. Consequently, there is a need to evaluate the ability of fins to withstand the physical challenges of terrestrial locomotion in order to shed light on how limbs conferred early stem tetrapods with an upper hand for becoming terrestrial. In the following papers, I have investigated the biomechanical capabilities of different musculoskeletal designs to understand the evolution of terrestrial locomotion in vertebrates. First, I compared the biomechanics of fins and limbs by measuring ground reaction force (GRF) production of mudskipper fishes (Periophthalmus barbarus) crutching and tiger salamanders (Ambystoma tigrinum) walking on level ground, two strategies for accomplishing terrestrial locomotion. Yet, tiger salamanders are already terrestrial. In order to understand how limbs function in a more habitually aquatic tetrapod, I conducted similar GRF analyses on a semi-aquatic newt (Pleurodeles waltl). Once tetrapods moved onto land, a major question is whether locomotion was primarily driven by the forelimbs or the hind limbs. Thus, I evaluated the ability of the forelimbs and hind limbs of A. tigrinum to withstand stresses during terrestrial locomotion. These data provided an opportunity to study whether the bones of different limbs possess different margins of safety against failure. Lastly, I synthesized how extant taxa can be used to model the biology of extinct taxa, advancing our knowledge about how functional innovation of the appendages contributed to one of the greatest revolutions in vertebrate history

Aquatic-terrestrial transitions of feeding systems in vertebrates : a mechanical perspective

Transitions to terrestrial environments confront ancestrally aquatic animals with several mechanical and physiological problems owing to the different physical properties of water and air. As aquatic feeders generally make use of flows of water relative to the head to capture, transport and swallow food, it follows that morphological and behavioral changes were inevitably needed for the aquatic animals to successfully perform these functions on land. Here, we summarize the mechanical requirements of successful aquatic-to-terrestrial transitions in food capture, transport and swallowing by vertebrates and review how different taxa managed to fulfill these requirements. Amphibious ray-finned fishes show a variety of strategies to stably lift the anterior trunk, as well as to grab ground-based food with their jaws. However, they still need to return to the water for the intra-oral transport and swallowing process. Using the same mechanical perspective, the potential capabilities of some of the earliest tetrapods to perform terrestrial feeding are evaluated. Within tetrapods, the appearance of a mobile neck and a muscular and movable tongue can safely be regarded as key factors in the colonization of land away from amphibious habitats. Comparative studies on taxa including salamanders, which change from aquatic feeders as larvae to terrestrial feeders as adults, illustrate remodeling patterns in the hyobranchial system that can be linked to its drastic change in function during feeding. Yet, the precise evolutionary history in form and function of the hyolingual system leading to the origin(s) of a muscular and adhesive tongue remains unknown

Trackways Produced by Lungfish During Terrestrial Locomotion

Some primarily aquatic vertebrates make brief forays onto land, creating traces as they do. A lack of studies on aquatic trackmakers raises the possibility that such traces may be ignored or misidentified in the fossil record. Several terrestrial Actinopterygian and Sarcopterygian species have previously been proposed as possible models for ancestral tetrapod locomotion, despite extant fishes being quite distinct from Devonian fishes, both morphologically and phylogenetically. Although locomotion has been well-studied in some of these taxa, trackway production has not. We recorded terrestrial locomotion of a 35 cm African lungfish (Protopterus annectens; Dipnoi: Sarcopterygii) on compliant sediment. Terrestrial movement in the lungfish is accomplished by planting the head and then pivoting the trunk. Impressions are formed where the head impacts the substrate, while the body and fins produce few traces. The head leaves a series of alternating left-right impressions, where each impact can appear as two separate semi-circular impressions created by the upper and lower jaws, bearing some similarity to fossil traces interpreted as footprints. Further studies of trackways of extant terrestrial fishes are necessary to understand the behavioural repertoire that may be represented in the fossil track record

Literatur Review: Ekologi Ikan Glodok Genus Boleophthalmus (Mudskipper)

Ikan glodok merupakan ikan yang hanya hidup pada kawasan pesisir dan bersubtrat lumpur. Ikan ini dapat berjalan dengan lincah diatas lumpur sehingga mendapat julukan mudskipper. Tulisan ini berisikan tentang ekologi ikan glodok pada genus Boleophthalmus. Pada genus tersebut terdapat 5 spesies, dimana secara morfologi terdapat perbedaan warna dan ukuran tubuh, dimana ukuran tubuh terbesar pada jenis P. schlosseri dan terkecil pada jenis P. takita. Ikan ini memiliki kebiasaan makan karnivora dan melakukan pemijahan secara serempak pada musim penghujan. Ikan glodok merupakan ikan yang mampu mentoleransi lingkungan dimana dia mampu hidup pada suhu 25 - 30,5 °C, pH 5,8 - 8,35, dan salinitas 17 ppt

Terrestrial capture of prey by the reedfish, a model species for stem tetrapods

Due to morphological resemblance, polypterid fishes are used as extant analogues of Late Devonian lobe‐finned sarcopterygians to identify the features that allowed the evolution of a terrestrial lifestyle in early tetrapods. Previous studies using polypterids showed how terrestrial locomotion capacity can develop, and how air ventilation for breathing was possible in extinct tetrapodomorphs. Interestingly, one polypterid species, the reedfish Erpetoichthys calabaricus, has been noted being capable of capturing prey on land. We now identified the mechanism of terrestrial prey‐capture in reedfish. We showed that this species uses a lifted trunk and downward inclined head to capture ground‐based prey, remarkably similar to the mechanism described earlier for eel‐catfish. Reedfish similarly use the ground support and flexibility of their elongated body to realize the trunk elevation and dorsoventral flexion of the anterior trunk region, without a role for the pectoral fins. However, curving of the body to lift the trunk may not have been an option for the Devonian tetrapodomorphs as they are significantly less elongated than reedfish and eel‐catfish. This would imply that, in contrast to the eel‐like extant species, evolution of the capacity to capture prey on land in early tetrapods may be linked to the evolution of the pectoral system to lift the anterior part of the body

Analisis Korelasi Kelimpahan Ikan Gelodok (Mudskipper) dengan Konsentrasi Karbon Organik Tanah pada Hutan Mangrove Desa Labuhan, Kecamatan Sepulu, Kabupaten Bangkalan, Madura

Hutan Mangrove merupakan salah satu jenis ekosistem lahan basah yang mampu menangkap karbon dioksida (CO2) di atmosfer dan menyimpan sebagian besar karbon dibawah permukaan tanah. Ekosistem mangrove merupakan habitat ikan gelodok yang menghabiskan sebagian besar waktunya di permukaan tanah, membuat sarang berupa lubang persembunyian di sekitar naungan mangrove, dan berperan sebagai bioindikator tanah atau kesuburan tanah yang baik untuk penanaman vegetasi mangrove. Hal ini mendasari tujuan penelitian untuk mengetahui kelimpahan ikan gelodok, konsentrasi karbon organik tanah serta korelasinya secara statistik pada vegetasi mangrove campuran di Hutan Mangrove Desa Labuhan Kecamatan Sepulu, Madura. Pengamatan kelimpahan dilakukan secara periodik sebanyak 3 kali selama 6 minggu pada 10 plot dalam hutan mangrove, pengambilan sampel tanah dilakukan pada tiap plot yang selanjutnya dilakukan uji gravimetri untuk mengetahui konsentrasi karbon organik tanah. Data parameter lingkungan juga diambil secara periodik sebagai data pendukung. Hasil penelitian didapatkan bahwa konsentrasi karbon organik tanah di lokasi penelitian sebesar 2,217±0,555%, kelimpahan fisik rata-rata ikan gelodok (mudkipper) 8±4.881 individu/100m2 dan kelimpahan non-fisik (lubang sarang) 10±3.281 sarang/100m2. Hasil uji korelasi Pearson antara karbon organik tanah dengan kelimpahan ikan gelodok (r = 0.193) dan lubang sarang (r = 0.083) p < 0.05, dinyatakan memiliki korelasi yang lemah, begitu pula parameter lingkungan seperti pH tanah, suhu tanah dan salinitas air terhadap karbon organik tanah

From cineradiography to biorobots: an approach for designing robots to emulate and study animal locomotion

Robots are increasingly used as scientific tools to investigate animal locomotion. However, designing a robot that properly emulates the kinematic and dynamic properties of an animal is difficult because of the complexity of musculoskeletal systems and the limitations of current robotics technology. Here we propose a design process that combines high-speed cineradiography, optimization, dynamic scaling, 3D printing, high-end servomotors, and a tailored dry-suit to construct Pleurobot: a salamander-like robot that closely mimics its biological counterpart, Pleurodeles waltl. Our previous robots helped us test and confirm hypotheses on the interaction between the locomotor neuronal networks of the limbs and the spine to generate basic swimming and walking gaits. With Pleurobot, we demonstrate a design process that will enable studies of richer motor skills in salamanders. In particular, we are interested in how these richer motor skills can be obtained by extending our spinal cord models with the addition of more descending pathways and more detailed limb central pattern generators (CPG) networks. Pleurobot is a dynamically-scaled amphibious salamander robot with a large number of actuated degrees of freedom (27 in total). Because of our design process, the robot can capture most of the animal’s degrees of freedom and range of motion, especially at the limbs. We demonstrate the robot’s abilities by imposing raw kinematic data, extracted from X-ray videos, to the robot’s joints for basic locomotor behaviors in water and on land. The robot closely matches the behavior of the animal in terms of relative forward speeds and lateral displacements. Ground reaction forces during walking also resemble those of the animal. Based on our results we anticipate that future studies on richer motor skills in salamanders will highly benefit from Pleurobot’s design

The Functional Significance of Structural Novelty in the Locomotor Apparatus of Turtles

The relationship between form and function can have profound impacts on the evolution and ecology of a lineage. Because of this relationship, variation in the morphology of a lineage has often been linked to adaptive radiations. However, form-function relationships are not linear, and variation in morphology does not necessarily predict variation in function due to the pervasive presence of mechanical equivalence in physiological systems. This possibility is often investigated through the lens of biomechanics, which uses physical principles to create a framework for comparing different systems with similar mechanical behaviors. Turtles represent an excellent system for studying how variation in structure might impact function. All extant turtles have descended from an aquatic common ancestor, and can be differentiated into two clades: cryptodires and pleurodires. These two clades can be distinguished by their pelvic girdle morphology. Cryptodires have an ancestral pelvic girdle morphology where the pelvis articulates with the sacral vertebrae at a joint, whereas pleurodires possess a derived morphology in which the pelvic girdle has been fused to the shell. My dissertation investigates the functional role of pelvic girdle fusion in pleurodire turtles by studying functional differences in the musculoskeletal system between pleurodires and cryptodires, and then by investigating how these functional differences might impact performance in water and on land. First, I evaluate differences in girdle movements between cryptodire and pleurodire turtles using X-ray Reconstruction of Moving Morphology. Next, I examine how pelvic girdle fusion impacts muscle function and use during walking and swimming. Third, I studied the potential for this novel structure to influence swimming performance. Finally, I compare the bone loading regimes of pleurodires with cryptodires during terrestrial locomotion. Data from these studies provide insight into the functional importance of novel structures and how they can impact the ecological and evolutionary history of lineages