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4 Muscle and tendon architecture in a thunniform swimmer, Isurus oxyrinchus. (A, B) Transverse sections through main anterior cone and adjacent hypaxial musculature, lateral to the left. (A) Fresh specimen illustrating the deep position of red muscles within the white muscles. (B) Histological section at 0.54 with 24 hypaxial lateral tendons visible (1 to 12 within red muscles, and 13 to 24 within white muscles). Dorso-and ventromedially, the red muscles are separated from the white muscles by a sheath of connective tissue. (C) Three-dimensional reconstruction of a posterior myoseptum. Notice the sections of hypaxial lateral tendons within the red muscle and the correspondence with the sections shown in A and B. (From Gemballa, S. et al., J. Morph., 267, 477-493, 2006. With permission.)

4 Muscle and tendon architecture in a thunniform swimmer, Isurus oxyrinchus. (A, B) Transverse sections through main anterior cone and adjacent hypaxial musculature, lateral to the left. (A) Fresh specimen illustrating the deep position of red muscles within the white muscles. (B) Histological section at 0.54 with 24 hypaxial lateral tendons visible (1 to 12 within red muscles, and 13 to 24 within white muscles). Dorso-and ventromedially, the red muscles are separated from the white muscles by a sheath of connective tissue. (C) Three-dimensional reconstruction of a posterior myoseptum. Notice the sections of hypaxial lateral tendons within the red muscle and the correspondence with the sections shown in A and B. (From Gemballa, S. et al., J. Morph., 267, 477-493, 2006. With permission.)

Citations

... Mechanical models have ignored segmentation and assumed homogenized properties for the hemitrichs (7,8) [except for the Geerlink and Videler model (6)]. Segmentation could be a way to increase the compliance of the hemitrichs to achieve the flexibility required for morphing, yet there are other, more direct ways to control stiffness in homogeneous structures: partial but uniform mineralization as seen in teleost fish bones (21) or fish scales (22) or cartilaginous tissues as in shark fins (23,24). Other possible functions for the segmentation of the hemitrichs may be related to growth and regeneration (25,26), damage tolerance (27), or hydrodynamic performance (28). ...
Article
Fish fins do not contain muscles, yet fish can change their shape with high precision and speed to produce large and complex hydrodynamic forces—a combination of high morphing efficiency and high flexural stiffness that is rare in modern morphing and robotic materials. These “flexo-morphing” capabilities are rare in modern morphing and robotic materials. The thin rays that stiffen the fins and transmit actuation include mineral segments, a prominent feature whose mechanics and function are not fully understood. Here, we use mechanical modeling and mechanical testing on 3D-printed ray models to show that the function of the segmentation is to provide combinations of high flexural stiffness and high morphing amplitude that are critical to the performance of the fins and would not be possible with rays made of a continuous material. Fish fin–inspired designs that combine very soft materials and very stiff segments can provide robotic materials with large morphing amplitudes and strong grasping forces.
... Across all plots, there is a clear pattern demonstrating that increasing size class is linked to larger prey items, from plankton to marine mammals (Figures 2 and 3). The FCAs for all traits, habitat use and feeding modality plots (Figures 2 and 3a locomotion, such as eels and rattails (grenadiers), and rajiform locomotion, the flatfish, skates and rays (Maia et al., 2012). ...
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Aim Functional diversity metrics inform how species’ traits relate to ecosystem functions, useful for quantifying how exploitation and disturbance impact ecosystems. We compare the functional diversity of entire fish communities in a shallow‐water region with a deep‐sea region for further insight into the differences between these ecosystem types. Location The regions compared in this study were selected to represent a shallow‐water coastal region, Tasman and Golden Bays (TBGB), and a deep‐sea region, Chatham Rise (CR), in New Zealand. Methods Functional diversity was assessed using four metrics: functional richness, evenness, divergence and dispersion. We compared these metrics across four key functions: habitat use, feeding, locomotion and life history. Results Our results showed that overall, the shallow‐water and deep‐sea ecosystems had equal diversity. When focusing on the four ecological functions, the two ecosystems exhibited equal diversity metrics across most analyses. Of the significantly different results, the deep‐sea had higher functional richness for habitat use and locomotion traits, lower functional dispersion for feeding and lower functional evenness for life history. Main conclusions Differences across the functions highlight higher diversity of habitat utilization by deep‐sea fish, while lower diversity in feeding suggests deep‐sea fish tend towards generalist diets, likely driven by low food availability. Deep‐sea fish displayed an increased range of locomotive traits in our analyses, but this conflicts with existing evidence and warrants further study. Life‐history results suggest deep‐sea fish exhibit higher clustering of traits, indicating potential under‐utilization of life‐history strategies in the deep‐sea. Our results demonstrate that although deep‐sea fish communities have similar levels of diversity to shallow‐water communities, the traits that structure this diversity differ, and therefore, the systems may respond to exploitation differently.
... Chafe Individual rolls to face one side of the body to the surface either in mid-water or to the bottom of the tank. Roll motion where dorsal side contacts surface or substrate in an effort to remove unwanted parasites or foreign bodies [19,36] Swim Typical swim behaviours with no burst or roll events, steady lateral undulatory locomotion [19,29]. 1500 s of swimming behaviour was allocated during periods where fish could be directly observed regularly swimming around the tank with no bursts in acceleration amplitude observed. ...
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Background Tri-axial accelerometers have been used to remotely describe and identify in situ behaviours of a range of animals without requiring direct observations. Datasets collected from these accelerometers (i.e. acceleration, body position) are often large, requiring development of semi-automated analyses to classify behaviours. Marine fishes exhibit many “burst” behaviours with high amplitude accelerations that are difficult to interpret and differentiate. This has constrained the development of accurate automated techniques to identify different “burst” behaviours occurring naturally, where direct observations are not possible. Methods We trained a random forest machine learning algorithm based on 624 h of accelerometer data from six captive yellowtail kingfish during spawning periods. We identified five distinct behaviours (swim, feed, chafe, escape, and courtship), which were used to train the model based on 58 predictive variables. Results Overall accuracy of the model was 94%. Classification of each behavioural class was variable; F 1 scores ranged from 0.48 (chafe) – 0.99 (swim). The model was subsequently applied to accelerometer data from eight free-ranging kingfish, and all behaviour classes described from captive fish were predicted by the model to occur, including 19 events of courtship behaviours ranging from 3 s to 108 min in duration. Conclusion Our findings provide a novel approach of applying a supervised machine learning model on free-ranging animals, which has previously been predominantly constrained to direct observations of behaviours and not predicted from an unseen dataset. Additionally, our findings identify typically ambiguous spawning and courtship behaviours of a large pelagic fish as they naturally occur.
... This may explain the robust condition of the bull shark despite its prolonged entanglement. Shark pectoral fins are moveable about the insertion, with musculature that allows them to be elevated, depressed and rotated relative to the body, and are critical for both vertical (rising and sinking) and horizontal (turning) manoeuvrability (Hoffmann et al., 2019;Maia et al., 2012;Wilga & Lauder, 2000), therefore the constant elevation of the pectoral fins caused by the apparatus would likely have affected swimming performance. Sharks have a high capacity for wound healing and recovery following injury (Bird, 1978;Chin et al., 2015;Kessel et al., 2017;Riley et al., 2009). ...
Article
A 193cm total length female bull shark Carcharhinus leucas was captured in Florida bearing intentionally attached materials which resembled a harness. Harness‐type live bait rigs are commonly used for small baitfish; some anglers use such devices with small sharks when targeting large sharks and bony fish. Biofouling on the apparatus and the extent of the injuries indicated the material had likely been on the shark for several years. This case highlights the dangers of using these types of devices on juveniles of long‐lived species that attain a large body size.
... Also, other startle responses have been reported involving a rapid withdrawal from a negative stimulus (e.g., Bierman et al., 2004;Currie & Carlsen, 1985), which resemble escape responses but are not caused by a predator-like threatening stimulus (i.e., escape-like response, Domenici & Hale, 2019). While studies on escape responses are common in teleost fish, studies focusing on chondrichthyans remain scarce (Maia et al., 2012). One exception is the pioneering work carried out by Domenici et al. (2004), in which the authors studied the locomotor performance of the spiny dogfish (Squalus acanthias) during escape responses. ...
... The species is characterized by primitive features such as seven paired gill openings and a single posterior-positioned dorsal fin, thus belonging to an ancient lineage of modern sharks (Hexanchiformes, Barnett et al., 2012;Naylor et al., 2012). Despite its unique body traits, sevengill sharks possess a body type that resembles other groups of epibenthic, benthic, and demersal sharks (i.e., body type 3, Maia et al., 2012; shallow-bodied/Group A, Sternes & Shimada, 2020). Body type 3, as described in Maia et al. (2012), have "relatively large heads, blunt snouts, more anterior pelvic fins, more posterior first dorsal fins, and a low heterocercal tail angle with a small to absent hypochordal lobe and a large subterminal lobe." ...
... Despite its unique body traits, sevengill sharks possess a body type that resembles other groups of epibenthic, benthic, and demersal sharks (i.e., body type 3, Maia et al., 2012; shallow-bodied/Group A, Sternes & Shimada, 2020). Body type 3, as described in Maia et al. (2012), have "relatively large heads, blunt snouts, more anterior pelvic fins, more posterior first dorsal fins, and a low heterocercal tail angle with a small to absent hypochordal lobe and a large subterminal lobe." These sharks also possess an anguilliform swimming mode, in which both trunk and tail participate in lateral motion to produce several waves that transmit through the body axis (Maia et al., 2012). ...
Article
Broadnose sevengill sharks (Notorynchus cepedianus) show great interest for bait and display a repertoire of movements while engaging with it. A novel back-thrust mechanism is described in wild sevengill sharks by which individuals back up from a negative stimulus while interacting with baited video stations. This mechanism initiates upon head contact with the device that functions as a negative stimulus eliciting a startle escape-like response. By heavily flipping pectoral fins and curving the body, sharks increase hydrodynamic resistance, backing up from the negative stimulus. Once backed up, sharks performed the common C-shaped double-bend escape maneuver described for sharks. Sharks also used the same back-thrust mechanism as a repositioning maneuver, but not as part of a startle response. The quantification of the turning rate indicated context-dependent variation in velocity and confirmed that the majority of withdrawals corresponded to slow escape-like motions. In general, an elongated body and individual flipping control of pectoral fins allowed for great maneuverability and lateral flexure. Sharks exhibited great tolerance to one another during double and triple encounters. The implications for grouping and social hunting of the species are briefly discussed based on past evidence and the movement behavior, gregarious interactions, and body markings observed in the present study. This work highlights the importance of studies in the natural environment and the use of complementary approaches to investigate the broader range of locomotor aspects of different shark species.
... Based on body form and fin shapes of sharks proposed by Wilga and Lauder (2004), body form of sharks of Turkish waters ranges from the anguilliform or eel-like, slow-swimming, demersal catsharks, Scyliorhinus sp. and Galeus melastomus, to the flattened ray-like angel sharks, Squatina sp. The fastswimming, predatory species, like thresher, Alopias sp., shortfin mako, Isurus oxyrinchus, great white, Carcharodon carcharias, or blue sharks, Prionace glauca, are all characterised with a torpedo-like streamlining body form. ...
... One of the reasons for their success has been attributed to the vast diversity of their locomotor designs (Lauder and Di Santo, 2016). Much of the work has focused on the morphology and function of their caudal fin referred to as a heterocercal tail characterized by the upward flexure of the notochordal axis (Thomson, 1976;Thomson and Simanek, 1977;Wilga and Lauder, 2002;Maia et al., 2012). One of the pioneer works on classifying sharks according to different body forms is that by Thomson and Simanek (1977). ...
... More recently, Irschick et al. (2017) examined eight shark species to determine if ecology influenced body form. Despite all these studies, the four body groups proposed by Thomson and Simanek (1977) have been assumed to capture the body form diversity in sharks (e.g., Maia et al., 2012;Shadwick and Goldbogen, 2012;Irschick and Hammerschlag, 2014;Lauder and Di Santo, 2016;Irschick et al., 2017) even though their study was based on only about one-tenth (56 different species) of all known shark species using simple morphometrics. ...
... Additionally, our analysis shows that each taxonomic order also differ in mean shape (ANOVA: df = 1, 452; F = 2.2; p < 0.05). Thomson and Simanek (1977) examined 56 species of sharks represented by a wide taxonomic range, where the four body form groups (Fig. 1B) have continued to be the basis of subsequent studies (e.g., Irschick and Hammerschlag, 2014;Irschick et al., 2017) and reviews on shark morphology and body mechanics (e.g., Maia et al., 2012;Shadwick and Goldbogen, 2012;Lauder and Di Santo, 2016). However, our landmark-based geometric morphometric analyses clearly show that there are two broad categories of body forms, rather than four, among extant sharks (Fig. 3B). ...
Article
Sharks are among the oldest vertebrate lineages in which their success has been attributed to their diversity in body shape and locomotor design. In this study, we investigated the diversity of body forms in extant sharks using landmark-based geometric morphometric analyses on nearly all the known (ca. 470) extant sharks. We ran three different analyses: the ‘full body,' ‘precaudal body,’ and ‘caudal fin' analyses. Our study suggests that there are two basic body forms in sharks, a ‘shallow-bodied’ form (Group A) and ‘deep-bodied’ form (Group B), where all sharks essentially have one basic caudal fin design of a heterocercal tail despite some specializations. We found that swimming modes in sharks are highly correlated with body forms where Group A sharks are predominantly anguilliform swimmers and Group B sharks are represented by carangiform and thunniform swimmers. The majority of Group A sharks are found to be benthic whereas pelagic forms are relatively common among Group B sharks. Each of the two superorders of sharks, Squalomorphii and Galeomorphii, must have gone through complex evolutionary history where each superorder contains both Group A sharks and Group B sharks, possibly involving parallel evolution from one group to the other or at least one episode of evolutionary reversal.
... This was supported by stomach content analysis on juvenile white sharks, which prey on nearshore pelagic and benthic fishes (Weng et al. 2007). In contrast, a more symmetric caudal fin enables adults to cruise steadily for long distances in search for large prey (e.g., marine mammals) (Lingham-Soliar 2005; Maia et al. 2012). Thereby, negative allometric growth may not only be an indication of differences in trophic niches, but possibly also of a higher predation pressure on juveniles than on adults (Carrier 1996;Irschick and Hammerschlag 2015). ...
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Many pelagic shark species change body and fin shape isometrically or by positive allometry during ontogeny. But some large apex predators such as the white shark Carcharodon carcharias or the tiger shark Galeocerdo cuvier show distinct negative allometry, especially in traits related to feeding (head) or propulsion (caudal fin). In particular, changes in propulsion are attributed to a shift in swimming mode. The more heterocercal caudal fin of younger individuals with its large caudal fin span seemingly aids in hunting small, agile prey. In contrast, the less heterocercal caudal fin with a larger fin area in larger individuals aids a long-distance slow swimming mode. We were interested if negative allometric effects can be observed in a planktivorous shark, the basking shark Cetorhinus maximus, a large species adapted to long-distance slow swimming. To address this question, we compared three size classes, specifically < 260 cm (juveniles), 299–490 cm (subadults), and from adults > 541 cm total length. Comparing literature data, we found negative allometric growth of the head and of the caudal fin, but a more rapid decrease of relative caudal fin size than of relative head length. Hereby, we provide the first evidence for early negative allometric growth of the caudal fin in a large pelagic filter-feeding shark. Our study further demonstrates that ecomorphological approaches may add valuable insight into the life history of animals that are challenging to study in their natural habitat, including large roving sharks such as the basking shark.
... In the adult malformed specimen of P. marquesi analyzed (NIVAJ 045, Figure 1) the right pelvic fin ventral musculature follows the pattern observed for other Myliobatiformes (Compagno & Roberts, 1982;Lucifora & Vassalo, 2002;Macesic & Kajiura, 2010;Maia, Wilga, & Lauder, 2012;Nishida, 1990). The most severe deformities are restricted to the left pelvic fin and mainly associated to the distal pelvic fin depressor (dfd) (Figure 4b). ...
Article
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We report deformities in the pelvic fin and clasper skeleton in specimens of Potamotrygon marquesi from Acre, Northwestern Brazil. The malformations involve skeletal deformities in the pelvic girdle, right clasper skeleton, and severe muscular and skeletal deformities in the left or right pelvic fin and clasper, including the loss of all of its terminal components. Descriptions of malformations dealing with elasmobranchs are extensive in the literature and are important for future studies dealing with their probable causes. Nevertheless, although the reasons of these deformities are herein possibly linked to malformation (as a result of stress or chemical contaminants) or predation, the anomalies in the muscular and skeletal components of the pelvic fin and clasper are described in detail and compared to a non‐deformed specimen.
... Draughtboard sharks (C. laticeps) were the least likely to get caught, and only one of the 68 observed individuals collided with trawl gear, probably due to the greater swimming efficiency of sharks (Lauder and Di Santo, 2015;Maia et al., 2012) and their larger relative size that would have allowed for greater burst swimming speeds away from the net. The locomotive response of other, more active species varies considerably, with Queirolo et al. (2012) observing Merluccius gayi gayi (South Pacific Hake) swimming forward (∼50%), whilst other small demersal fish species were observed in a motionless state (∼42%) or swimming towards the net (∼38%). ...
Article
Elasmobranchs make a large contribution to bycatch in commercial trawl fisheries, which reduces the efficiency (and thus profitability of those fisheries), results in injury and mortality of those elasmobranchs, and can lead to unsustainable rates of catches. The development of bycatch reduction devices (BRDs) for elasmobranchs has been hindered, among other things, by a lack of knowledge of their avoidance behaviours and thus their vulnerability to capture (catchability). This lack of knowledge potentially affects assessments of the impact of fishing on those bycatch species. Here we examined underwater behaviours, using video analysis, of three species of elasmobranchs (two stingarees, i.e. Urolophus cruciatus and U. paucimaculatus, and one draughtboard shark, Cephalocyllium laticeps) in response to an approaching demersal trawl to quantify behavioural factors that affect their catchability. The morphologically similar U.cruciatus and U. paucimaculatus were similarly abundant, i.e. 290 and 218 individuals, respectively, but displayed different net avoidance behaviours, with U. paucimaculatus being far more likely to enter the trawl. The greater catchability of U. paucimaculatus would falsely suggest this less common species was more abundant than U. cruciatus, which has implications for any assessments of the impacts of trawling on these two elasmobranchs. Collision with trawl gear was relatively common for both Urolophus spp., and this was shown to decrease their likelihood of capture. In contrast, only 1 of the 68 individuals of the morphologically-different C. laticeps collided with gear. These results will help inform future development of BRDs and highlight that understanding the behaviour of elasmobranchs in response to capture methods should form an integral component of assessments of the impacts of trawling on this highly affected group.