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Many teleosts possess a unique set of respiratory characteristics allowing enhanced oxygen unloading to the tissues during stress. This system comprises three major components: highly pH sensitive haemoglobins (large Bohr and Root effects), rapid red blood cell (RBC) intracellular pH (pHi) protection, and a heterogeneous distribution of membrane-bound plasma-accessible carbonic anhydrase (paCA; absence in the gills). The first two components have received considerable research effort; however, the evolutionary loss of branchial paCA has received little attention. In the current study, we investigated the availability of branchial membrane-bound CA, along with several other CA-related characteristics in species belonging to three basal actinopterygian groups: the Lepisosteiformes, Acipenseriformes and Polypteriformes to assess the earlier hypothesis that Root effect haemoglobins constrain branchial paCA availability. We present the first evidence suggesting branchial membrane-bound CA presence in a basal actinopterygian species: the Senegal bichir (Polypterus senegalus) and show that like the teleosts, white sturgeon (Acipenser transmontanus) and alligator gar (Atractosteus spatula) do not possess branchial membrane-bound CA. We discuss the varying respiratory strategies for these species and propose that branchial paCA may have been lost much earlier than previously thought, likely in relation to the changes in haemoglobin buffer capacity associated with the increasing magnitude of the Bohr effect. The findings described here represent an important advancement in our understanding of the evolution of the unique system of enhanced oxygen unloading thought to be present in most teleosts, a group that encompasses half of all vertebrates. [ABSTRACT FROM AUTHOR]

Movement of fishes in the aquatic realm is fundamental to their ecology and survival. Movement can be driven by a variety of biological, physiological and environmental factors occurring across all spatial and temporal scales. The intrinsic capacity of movement to impact fish individually (e.g., foraging) with potential knock‐on effects throughout the ecosystem (e.g., food web dynamics) has garnered considerable interest in the field of movement ecology. The advancement of technology in recent decades, in combination with ever‐growing threats to freshwater and marine systems, has further spurred empirical research and theoretical considerations. Given the rapid expansion within the field of movement ecology and its significant role in informing management and conservation efforts, a contemporary and multidisciplinary review about the various components influencing movement is outstanding. Using an established conceptual framework for movement ecology as a guide (i.e., Nathan et al., 2008: 19052), we synthesized the environmental and individual factors that affect the movement of fishes. Specifically, internal (e.g., energy acquisition, endocrinology, and homeostasis) and external (biotic and abiotic) environmental elements are discussed, as well as the different processes that influence individual‐level (or population) decisions, such as navigation cues, motion capacity, propagation characteristics and group behaviours. In addition to environmental drivers and individual movement factors, we also explored how associated strategies help survival by optimizing physiological and other biological states. Next, we identified how movement ecology is increasingly being incorporated into management and conservation by highlighting the inherent benefits that spatio‐temporal fish behaviour imbues into policy, regulatory, and remediation planning. Finally, we considered the future of movement ecology by evaluating ongoing technological innovations and both the challenges and opportunities that these advancements create for scientists and managers. As aquatic ecosystems continue to face alarming climate (and other human‐driven) issues that impact animal movements, the comprehensive and multidisciplinary assessment of movement ecology will be instrumental in developing plans to guide research and promote sustainability measures for aquatic resources. [ABSTRACT FROM AUTHOR]

Sociality in animals depends on identification and recognition of conspecifics and social interactions can be a key driving force in ecological processes. We capitalized on the environmentally dependent sociality and unique reproductive strategy of the self-fertilizing mangrove rivulus (Kryptolebias marmoratus) to disentangle the influence of relatedness and familiarity on conspecific recognition. We also compared the importance of vision and chemosensation as primary phenotypic sensory cues in distinguishing individual fish and prey. Using lab-reared, isogenic rivulus, we presented a focal fish with the choice between two conspecifics (related and/or familiar). We determined that there was no clear impact of relatedness on short term association preferences in the two isogenic lineages we tested. Rather, rivulus preferentially associated with unrelated, familiar individuals over unrelated, unfamiliar individuals. Next, we used both isogenic lab lineages and wild-caught rivulus to determine the primary sensory modality involved in recognition by measuring aggressive behavior while manipulating the type of sensory information (visual and chemosensory) available during binary association trials. Our data indicate that this mangrove fish uses primarily visual cues and familiarity templates for mediating social interactions, contributing to the growing body of knowledge on recognition systems in fishes. Significance statement: Social relationships depend on the assessment of potential partners. We know that fishes can discriminate among individuals; however, how they recognize each other is more complex. We capitalized on the unique social behavior and reproductive strategy of a small mangrove fish to determine if they preferentially recognize related individuals, familiar individuals, or a combination of the two. We also asked if they used vision and/or smell as their primary mode of recognition. Here, we show that these fish prefer to associate with familiar yet unrelated individuals, possibly because there are more direct benefits associating with fish they have previously encountered. We also concluded that these fish use vision over smell to recognize other individuals even in murky mangrove water. Social behaviors are likely to change as a result of environmental change. Thus, understanding how fish recognize each other has important implications for their conservation and how they will respond to environmental challenges. [ABSTRACT FROM AUTHOR]

We modeled swimming kinematics and body mechanics of several fish species of varying habitat and body shape based on measurements of internal vertebral morphology. Synopsis One key evolutionary innovation that separates vertebrates from invertebrates is the notochord, a central element that provides the stiffness needed for powerful movements. Later, the notochord was further stiffened by the vertebrae, cartilaginous, and bony elements, surrounding the notochord. The ancestral notochord is retained in modern vertebrates as intervertebral material, but we know little about its mechanical interactions with surrounding vertebrae. In this study, the internal shape of the vertebrae—where this material is found—was quantified in 16 species of fishes with various body shapes, swimming modes, and habitats. We used micro-computed tomography to measure the internal shape. We then created and mechanically tested physical models of intervertebral joints. We also mechanically tested actual vertebrae of five species. Material testing shows that internal morphology of the centrum significantly affects bending and torsional stiffness. Finally, we performed swimming trials to gather kinematic data. Combining these data, we created a model that uses internal vertebral morphology to make predictions about swimming kinematics and mechanics. We used linear discriminant analysis (LDA) to assess the relationship between vertebral shape and our categorical traits. The analysis revealed that internal vertebral morphology is sufficient to predict habitat, body shape, and swimming mode in our fishes. This model can also be used to make predictions about swimming in fishes not easily studied in the laboratory, such as deep sea and extinct species, allowing the development of hypotheses about their natural behavior. [ABSTRACT FROM AUTHOR]

The present study assessed the aerial and aquatic visual abilities of juvenile grey bichir Polypterus senegalus, fish capable of terrestrial locomotion, by measuring the optokinetic response to stimuli of varying speed and spatial frequency. In water, fish tracked slow‐moving (2° s−1) stimuli moderately well and fast‐moving stimuli very poorly. Spatial acuity was very low compared with many other species, with maximum response observed at 0.05–0.075 stimulus cycles per degree of visual arc; however, it should be noted that adult fish, with their larger eyes, are likely to have somewhat improved spatial acuity. Low spatial acuity and limited stimulus tracking ability might be expected in a nocturnal ambush predator such as P. senegalus, where gaze stabilization may be less crucial and other sensory inputs may have greater importance in perception of the environment. In air, spatial and temporal acuity were both poorer by every measure, but some visual ability persisted. As the eye shows no anatomical specialization for aerial vision, poor vision was expected; however, the large decrease in saccade velocity observed in air trials was unexpected. Stimulus parameters typically have little effect on the characteristics of the saccade, so this finding may suggest that the function of the reflex system itself could be compromised in the aerial vision of some fishes capable of terrestrial locomotion. [ABSTRACT FROM AUTHOR]

The ability to modulate the function of muscle is integral to an animal's ability to function effectively in the face of widely disparate challenges. This modulation of function can manifest through short-term changes in neuromuscular control, but also through long-term changes in force profiles, fatigability, and architecture. However, the relative extent to which shorter-term modulation and longer-term plasticity govern locomotor flexibility remains unclear. Here, we obtain simultaneously-recorded kinematic and muscle activity data of fin and body musculature of an amphibious fish, Polypterus senegalus. After examining swimming and walking behaviour in aquatically-raised individuals, we show that walking behaviour is characterized by greater absolute duration of muscle activity in most muscles when compared with swimming, but that the magnitude of recruitment during walking is only increased in the secondary bursts of fin muscle and in the primary burst of the mid-body point. This localized increase in intensity suggests that walking in P. senegalus is powered in a few key locations on the fish, contrasting with the more distributed, low intensity muscle force that characterizes the stroke cycle during swimming. Finally, the increased intensity in secondary, but not primary, bursts of the fin muscles when walking likely underscores the importance of antagonistic muscle activity to prevent fin collapse, add stabilization, and increase body support. Understanding the principles that underlie the flexibility of muscle function can provide key insights into the sources of animal functional and behavioural diversity. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Zoology is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Muscle fiber types in the pectoral fins of fishes have rarely been examined, despite their morphological and functional diversity. Here, we describe the distribution of fast and slow muscle fibers in the pectoral fins of Polypterus senegalus, an amphibious, basal actinopterygian. Each of the four muscle groups examined using mATPase staining showed distinct fiber-type regionalization. Comparison between fish raised in aquatic and terrestrial environments revealed terrestrially reared fish possess 28% more fast muscle compared with aquatically reared fish. The pattern of proximal-distal variation in the abductors differed, with a relative decrease in fast muscle fibers near the pectoral girdle in aquatic fish compared with an increase in terrestrial fish. Terrestrially reared fish also possess a greater proportion of very small diameter fibers, suggesting that they undergo more growth via hyperplasia. These observations may be a further example of adaptive plasticity in Polypterus, allowing for greater bursts of power during terrestrial locomotion. [ABSTRACT FROM AUTHOR]

Polypterus, a member of the most primitive living group of ray-finned fishes, has demonstrated the ability to perform fin-assisted terrestrial locomotion, a behavior that indicates a complex pectoral musculoskeletal system. Review of the literature reveals that many aspects of the pectoral muscular anatomy of Polypterus are still unclear, with a number of conflicting descriptions. We provide a new interpretation of the pectoral musculature using soft tissue-enhanced microCT scanning and gross anatomical dissection. The results demonstrate a complex musculature, with six independent muscles crossing the glenoid-fin joint. Comparisons with other bony-fish (Osteichthyes), including both ray-finned (Actinopterygii) and lobed-fin (Sarcopterygii) fish, indicate the presence of novel muscles within Polypterus: coracometapterygialis I+II and the zonopropterygialis medialis. Examination of these muscular additions in the context of osteichthyan phylogeny indicates that this represents a previously unrecognized event in the evolution of pectoral musculature in Osteichthyes. Despite its phylogenetic position as a basal actinopterygian, the musculature of Polypterus has more similarities both anatomically and functionally with that of sarcopterygians. This anatomy, along with other features of Polypterus anatomy such as lobed fins, ventral paired lungs, and a large spiracle, may make it a good model for inferences of stem tetrapod locomotion. [ABSTRACT FROM AUTHOR]

The origin of tetrapods from their fish antecedents, approximately 400 million years ago, was coupled with the origin of terrestrial locomotion and the evolution of supporting limbs. Polypterus is a member of the basal-most group of ray-finned fish (actinopterygians) and has many plesiomorphic morphologies that are comparable to elpistostegid fishes, which are stem tetrapods. Polypterus therefore serves as an extant analogue of stem tetrapods, allowing us to examine how developmental plasticity affects the 'terrestrialization' of fish. We measured the developmental plasticity of anatomical and biomechanical responses in Polypterus reared on land. Here we show the remarkable correspondence between the environmentally induced phenotypes of terrestrialized Polypterus and the ancient anatomical changes in stem tetrapods, and we provide insight into stem tetrapod behavioural evolution. Our results raise the possibility that environmentally induced developmental plasticity facilitated the origin of the terrestrial traits that led to tetrapods. [ABSTRACT FROM AUTHOR]

Although kinematic analysis of individual fin rays provides valuable insight into the contribution of median fins to C-start performance, it paints an incomplete picture of the complex movements and deformation of the flexible fin surface. To expand our analysis of median fin function during the escape response of bluegill sunfish (Lepomis macrochirus), patterns of spanwise and chordwise curvature of the soft dorsal and anal fin surfaces were examined from the same video sequences previously used in analysis of fin-ray movement and orientation. We found that both the span and chord undergo undulation, starting in the anterior region of either fin. Initiated early in Stage 1 of the C-start, the undulation travels in a postero-distal direction, reaching the trailing edge of the fins during early Stage 2. Maximum spanwise curvature typically occurred among the more flexible posterior fin rays, though there was no consistent correlation between maximum curvature and fin-ray position. Undulatory patterns suggest different mechanisms of action for the fin regions. In the anterior fin region, where the fin rays are oriented dorsoventrally, undulation is directed primarily chordwise, initiating a transfer of momentum into the water to overcome the inertia of the flow and direct the water posteriorly. Within the posterior region, where the fin rays are oriented caudally, undulation is predominantly directed spanwise; thus, the posterior fin region acts to ultimately accelerate this water towards the tail to increase thrust forces. Treatment of median fins as appendages with uniform properties does not do justice to their complexity and effectiveness as control surfaces. [ABSTRACT FROM AUTHOR]

The fast-start escape response is critically important to avoid predation, and axial movements driving it have been studied intensively. Large median dorsal and anal fins located near the tail have been hypothesized to increase acceleration away from the threat, yet the contribution of flexible median fins remains undescribed. To investigate the role of median fins, C-start escape responses of bluegill sunfish (Lepomis macrochirus) were recorded by three high-speed, high-resolution cameras at 500framess"1 and the 3-D kinematics of individual dorsal and anal fin rays were analyzed. Movement and orientation of the fin rays relative to the body axis were calculated throughout the duration of the C-start. We found that: (1) timing and magnitude of angular displacement varied among fin rays based on position within the fin and (2) kinematic patterns support the prediction that fin rays are actively resisting hydrodynamlc forces and transmitting momentum into the water. We suggest that regions within the fins have different roles. Anterior regions of the fins are rapidly elevated to increase the volume of water that the fish may interact with and transmit force into, thus generating greater total momentum. The movement pattern of all the fin rays creates traveling waves that move posteriorly along the length of the fin, moving water as they do so. Flexible posterior regions ultimately act to accelerate this water towards the tail, potentially interacting with vortices generated by the caudal fin during the C-start. Despite their simple appearance, median fins are highly complex and versatile control surfaces that modulate locomotor performance. [ABSTRACT FROM AUTHOR]

Fish swimming has often been simplified into the motions of a two-dimensional slice through the horizontal midline, as though fishes live in a flat world devoid of a third dimension. While fish bodies do undulate primarily horizontally, this motion has important three-dimensional components, and fish fins can move in a complex three-dimensional manner. Recent results suggest that an understanding of the three-dimensional body shape and fin motions is vital for explaining the mechanics of swimming, and that two-dimensional representations of fish locomotion are misleading. In this study, we first examine axial swimming from the two-dimensional viewpoint, detailing the limitations of this view. Then we present data on the kinematics and hydrodynamics of the dorsal fin, the anal fin and the caudal fin during steady swimming and maneuvering in brook trout, Salvelinus fontinalis, bluegill sunfish, Lepomis macrochirus, and yellow perch, Perca flavescens. These fishes actively move the dorsal and anal fins during swimming, resulting in curvature along both anterio-posterior and dorso-ventral axes. The momentum imparted to the fluid by these fins comprises a substantial portion of total swimming force, adding to thrust and contributing to roll stability. While swimming, the caudal fin also actively curves dorso-ventrally, producing vortices separately from both its upper and lower lobes. This functional separation of the lobes may allow additional control of three-dimensional orientation, but probably reduces swimming efficiency. In contrast, fish may boost the caudal fin's efficiency by taking advantage of the flow from the dorsal and anal fins as it interacts with the flow around the caudal fin itself. During maneuvering, fish readily use their fins outside of the normal planes of motion. For example, the dorsal fin can flick laterally, orienting its surface perpendicular to the body, to help in turning and braking. These data demonstrate that, while fish do move primarily in the horizontal plane, neither their bodies nor their motions can accurately be simplified in a two-dimensional representation. To begin to appreciate the functional consequences of the diversity of fish body shapes and locomotor strategies, one must escape Flatland to examine all three dimensions. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Fisheries & Aquatic Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The locomotor performance of dogfish during escape responses was observed by means of high-speed video. Dogfish show C-type escape responses that are comparable with those shown previously in teleosts. Dogfish show high variability of turning rates of the anterior part of the body (head to centre of mass), i.e. with peak values from 434 to 1023 deg. s-1. We suggest that this variability may be due to the presence of two types of escape manoeuvres, i.e. responses with high and low turning rates, as previously found in a teleost species. Fast responses (i.e. with high maximum turning rates, ranging between 766 and 1023 deg. s-1) showed significantly higher locomotor performance than slow responses (i.e. with low maximum turning rates, ranging between 434 and 593 deg. s-1) in terms of distance covered, speed and acceleration, although no differences were found in the turning radius of the centre of mass during the escape manoeuvres. The existence of two types of escape responses would have implications in terms of both neural control and muscular activation patterns. When compared with literature data for the locomotor performance of bony fishes, dogfish showed relatively low speed and acceleration, comparable turning rates and a turning radius that is in the iow part of the range when compared with teleosts, indicating relatively high manoeuvrability. The locomotor performance observed in dogfish is consistent with their morphological characteristics: (1) low locomotor performance associated with low thrust developed by their relatively small posterior depth of section and (2) relatively high manoeuvrability associated with their high flexibility. [ABSTRACT FROM AUTHOR]

Adult Pacific salmon (Oncorhynchus spp.) depend on energy reserves to complete their upriver spawning migration. Little is known about how flow patterns and bank characteristics affect energetics or how species differ in reach-specific energy use. In 1999, electromyogram (EMG) radiotelemetry was used to describe activity levels and estimate energy use of 12 adult pink salmon (Oncorhynchus gorbuscha) during their upstream migration in a 7-km section of the Fraser River Canyon. Data collected previously on sockeye salmon (Oncorhynchus nerka) in the same study area provided a species comparison. We could not identify any strong differences in energetics between species. Although sex had some influence, reach characteristics were the primary factors affecting migration activity and energetics. Fish increased their activity levels when they migrated through reaches constricted by islands or gravel bars compared with nonconstricted reaches. The former contained higher velocity currents and more complex hydraulic conditions than the latter. Two behavioural responses, with similar energetic consequences, occurred in constricted reaches. Either fish swam slowly and took more time, presumably searching for lower velocity areas for migration thus increasing passage time, or they swam quickly through higher velocity flow fields. [ABSTRACT FROM AUTHOR]

Reports that little is known about the behavior patterns and swimming speed strategies of anadromous upriver migrating fish. Description of a study in which electromyogram telemetry was used to estimate instantaneous swimming speeds for individual sockeye (Oncorhynchus nerka) and pink salmon (O. gorbuscha) during their spawning migrations through reaches which spanned a gradient in river hydraulic features in the Fraser River, British Columbia; Objectives of the study was to describe patterns of individual-specific swim speeds and behaviors, identify swimming speed strategies and contrast these between sexes, species and reaches; Findings of no differences between sexes or species in the proportion of total time swimming in varying categories; Speculation that complex current patterns generated by river constrictions created confusing migration cues, which impeded a salmon's ability to locate appropriate pathways.

An introduction is presented in which the editor discusses articles in the issue on topics including systematics of sessile, irregularly coiled and suspension feeding snails, Biography, and Bibliography.

Amphibious animals adapt their body coordination to compensate for changing substrate properties as they transition between terrestrial and aquatic environments. Using behavioural experiments and mathematical modelling of the amphibious centipede Scolopendra subspinipes mutilans, we reveal an interplay between descending command (brain), local pattern generation, and sensory feedback that controls the leg and body motion during swimming and walking. The elongated and segmented centipede body exhibits a gradual transition in the locomotor patterns as the animal crosses between land and water. Changing environmental conditions elicit a mechano-sensory feedback mechanism, inducing a gait change at the local segment level. The body segments operating downstream of a severed nerve cord (no descending control) can generate walking with mechano-sensory inputs alone while swimming behaviour is not recovered. Integrating the descending control for swimming initiation with the sensory feedback control for walking in a mathematical model successfully generates the adaptive behaviour of centipede locomotion, capturing the possible mechanism for flexible motor control in animals. [ABSTRACT FROM AUTHOR]

Domestication research has largely focused on identification of morphological and genetic differences between extant populations of crops and their wild relatives. Little attention has been paid to the potential effects of environment despite substantial known changes in climate from the time of domestication to modern day. In recent research, the exposure of teosinte (i.e., wild maize) to environments similar to the time of domestication, resulted in a plastic induction of domesticated phenotypes in teosinte. These results suggest that early agriculturalists may have selected for genetic mechanisms that cemented domestication phenotypes initially induced by a plastic response of teosinte to environment, a process known as genetic assimilation. To better understand this phenomenon and the potential role of environment in maize domestication, we examined differential gene expression in maize (Zea mays ssp. mays) and teosinte (Zea mays ssp. parviglumis) between past and present conditions. We identified a gene set of over 2000 loci showing a change in expression across environmental conditions in teosinte and invariance in maize. In fact, overall we observed both greater plasticity in gene expression and more substantial changes in co-expressionnal networks in teosinte across environments when compared to maize. While these results suggest genetic assimilation played at least some role in domestication, genes showing expression patterns consistent with assimilation are not significantly enriched for previously identified domestication candidates, indicating assimilation did not have a genome-wide effect. [ABSTRACT FROM AUTHOR]

The article presents abstracts on vertebrate paleontology topics which includes ontogeny of the early Triassic Thrinaxodon liorhinus, vertebrate and geological signatures of the construction of Moghra formation in North Western Desert in Egypt and the encephalization and brain morphology of false sabertoothed cats.