Mechanosensory signal transmission in the arms and the nerve ring, an interarm connective, of .

Octopuses coordinate their arms in a range of complex behaviors. In addition to brain-based sensorimotor integration and control, interarm coordination also occurs through a nerve ring at the arms' base. Here, we examine responses to mechanosensory stimulation of the arms by recording neural activity in the stimulated arm, the nerve ring, and other arms in a preparation of only the ring and arms.

Multiple nerve cords connect the arms of octopuses, providing alternative paths for inter-arm signaling.

Octopuses are remarkable in their ability to use many arms together during behavior (e.g., see Levy et al.

Extraoral Taste Buds on the Paired Fins of Damselfishes.

Some fish species have taste buds on the surface of their bodies and fins, as well as in the oral cavity. The extraoral taste system of fish has traditionally been studied in species that inhabit environments and/or employ feeding strategies where vision is limited. Here we examined taste sensation in a new ecological context by investigating the paired fins of damselfish (Pomacentridae), a group of diurnal midwater fishes that inhabit the light-rich waters of coral reefs.

The Water to Land Transition Submerged: Multifunctional Design of Pectoral Fins for Use in Swimming and in Association with Underwater Substrate.

Fins of fishes provide many examples of structures that are beautifully designed to power and control movement in water; however, some species also use their fins for substrate-associated behaviors where interactions with solid surfaces are key. Here, we examine how the pectoral fins of ray-finned fish with these multifunctional behavioral demands, in water and on solid surfaces, are structured and function. We subdivide fins used in swimming and substrate contact into two general morphological categories, regionalized vs.

Evolution of touch and proprioception of the limbs: Insights from fish and humans.

The function of the hands is inextricably linked to cutaneous mechanosensation, both in touch and in how hand movement and posture (proprioception) are controlled. The structure and behavior of hands and distal forelimbs of other vertebrates have been evolutionarily shaped by these mechanosensory functions. The distal forelimb of tetrapod vertebrates is homologous to the pectoral fin rays and membrane of fishes.

Hindbrain and Spinal Cord Contributions to the Cutaneous Sensory Innervation of the Larval Zebrafish Pectoral Fin.

Vertebrate forelimbs contain arrays of sensory neuron fibers that transmit signals from the skin to the nervous system. We used the genetic toolkit and optical clarity of the larval zebrafish to conduct a live imaging study of the sensory neurons innervating the pectoral fin skin. Sensory neurons in both the hindbrain and the spinal cord innervate the fin, with most cells located in the hindbrain.

Sensing the structural characteristics of surfaces: texture encoding by a bottom-dwelling fish.

The texture of contacted surfaces influences our perception of the physical environment and modulates behavior. Texture perception and its neural encoding mechanisms have traditionally been studied in the primate hand, yet animals of all types live in richly textured environments and regularly interact with textured surfaces. Here we explore texture sensation in a different type of vertebrate limb by investigating touch and potential texture encoding mechanisms in the pectoral fins of fishes, the forelimb homologs.

DNA-based fluorescent probes of NOS2 activity in live brains.

Innate immune cells destroy pathogens within a transient organelle called the phagosome. When pathogen-associated molecular patterns (PAMPs) displayed on the pathogen are recognized by Toll-like receptors (TLRs) on the host cell, it activates inducible nitric oxide synthase (NOS2) which instantly fills the phagosome with nitric oxide (NO) to clear the pathogen. Selected pathogens avoid activating NOS2 by concealing key PAMPs from their cognate TLRs.

Pectoral fin kinematics and motor patterns are shaped by fin ray mechanosensation during steady swimming in .

For many fish species, rhythmic movement of the pectoral fins, or forelimbs, drives locomotion. In terrestrial vertebrates, normal limb-based rhythmic gaits require ongoing modulation with limb mechanosensors. Given the complexity of the fluid environment and dexterity of fish swimming through it, we hypothesize that mechanosensory modulation is also critical to normal fin-based swimming.

Escape responses of fish: a review of the diversity in motor control, kinematics and behaviour.

The study of fish escape responses has provided important insights into the accelerative motions and fast response times of these animals. In addition, the accessibility of the underlying neural circuits has made the escape response a fundamental model in neurobiology. Fish escape responses were originally viewed as highly stereotypic all-or-none behaviours.

Comparative Principles for Next-Generation Neuroscience.

Neuroscience is enjoying a renaissance of discovery due in large part to the implementation of next-generation molecular technologies. The advent of genetically encoded tools has complemented existing methods and provided researchers the opportunity to examine the nervous system with unprecedented precision and to reveal facets of neural function at multiple scales. The weight of these discoveries, however, has been technique-driven from a small number of species amenable to the most advanced gene-editing technologies.

Adipose fin development and its relation to the evolutionary origins of median fins.

The dorsal, anal and caudal fins of vertebrates are proposed to have originated by the partitioning and transformation of the continuous median fin fold that is plesiomorphic to chordates. Evaluating this hypothesis has been challenging, because it is unclear how the median fin fold relates to the adult median fins of vertebrates. To understand how new median fins originate, here we study the development and diversity of adipose fins.

Fins as Mechanosensors for Movement and Touch-Related Behaviors.

Mechanosensation is a universal feature of animals that is essential for behavior, allowing detection of animals' own body movement and position as well as physical characteristics of the environment. The extraordinary morphological and behavioral diversity that exists across fish species provide rich opportunities for comparative mechanosensory studies in fins. The fins of fishes have been found to function as proprioceptors, by providing feedback on fin ray position and movement, and as tactile sensors, by encoding pressures applied to the fin surface.

A comparison of pectoral fin ray morphology and its impact on fin ray flexural stiffness in labriform swimmers.

The organization of tissues in appendages often affects their mechanical properties and function. In the fish family Labridae, swimming behavior is associated with pectoral fin flexural stiffness and morphology, where fins range on a continuum from stiff to relatively flexible fins. Across this diversity, pectoral fin flexural stiffness decreases exponentially along the length of any given fin ray, and ray stiffness decreases along the chord of the fin from the leading to trailing edge.

The relationship between pectoral fin ray stiffness and swimming behavior in Labridae: insights into design, performance and ecology.

The functional capabilities of flexible, propulsive appendages are directly influenced by their mechanical properties. The fins of fishes have undergone extraordinary evolutionary diversification in structure and function, which raises questions of how fin mechanics relate to swimming behavior. In the fish family Labridae, pectoral fin swimming behavior ranges from rowing to flapping.

Mechanosensation is evolutionarily tuned to locomotor mechanics.

The biomechanics of animal limbs has evolved to meet the functional demands for movement associated with different behaviors and environments. Effective movement relies not only on limb mechanics but also on appropriate mechanosensory feedback. By comparing sensory ability and mechanics within a phylogenetic framework, we show that peripheral mechanosensation has evolved with limb biomechanics, evolutionarily tuning the neuromechanical system to its functional demands.

Local Spinal Cord Circuits and Bilateral Mauthner Cell Activity Function Together to Drive Alternative Startle Behaviors.

The reticulospinal Mauthner cells (M-cells) of the startle circuit have been considered to be dedicated to one basic motor output and the C-type startle response in fish. The neural circuit underlying the C-start, a startle behavior in which the fish forms a "C"-shaped body bend has been described in depth in goldfish and zebrafish [1, 2] and is thought to occur in other species [3, 4]. However, previous research has shown that some species can perform a second type of startle called the S-start [5-7].

Neural circuits that drive startle behavior, with a focus on the Mauthner cells and spiral fiber neurons of fishes.

Startle behaviors are rapid, high-performance motor responses to threatening stimuli. Startle responses have been identified in a broad range of species across animal diversity. For investigations of neural circuit structure and function, these behaviors offer a number of benefits, including that they are driven by large and identifiable neurons and their neural control is simple in comparison to other behaviors.

Mechanosensation in an adipose fin.

Adipose fins are found on approximately 20% of ray-finned fish species. The apparently rudimentary anatomy of adipose fins inspired a longstanding hypothesis that these fins are vestigial and lack function. However, adipose fins have evolved repeatedly within Teleostei, suggesting adaptive function.

A Large-Scale Pattern of Ontogenetic Shape Change in Ray-Finned Fishes.

Fishes exhibit a remarkable diversity of body shape as adults; however, it is unknown whether this diversity is reflected in larval stage morphology. Here we investigate the relationship between larval and adult body shape as expressed by body elongation. We surveyed a broad range of ray-finned fish species and compared body shape at larval and adult stages.

Touch sensation by pectoral fins of the catfish Pimelodus pictus.

Mechanosensation is fundamental to many tetrapod limb functions, yet it remains largely uninvestigated in the paired fins of fishes, limb homologues. Here we examine whether membranous fins may function as passive structures for touch sensation. We investigate the pectoral fins of the pictus catfish (Pimelodus pictus), a species that lives in close association with the benthic substrate and whose fins are positioned near its ventral margin.

Fin ray sensation participates in the generation of normal fin movement in the hovering behavior of the bluegill sunfish (Lepomis macrochirus).

For many fish species, the pectoral fins serve as important propulsors and stabilizers and are precisely controlled. Although it has been shown that mechanosensory feedback from the fin ray afferent nerves provides information on ray bending and position, the effects of this feedback on fin movement are not known. In other taxa, including insects and mammals, sensory feedback from the limbs has been shown to be important for control of limb-based behaviors and we hypothesized that this is also the case for the fishes.