Shark Body Research Articles

The Biomimetic Shark Skin Optimization Design Method for Improving Lubrication Effect of Engineering Surface.

Nature has long been an important source of inspiration for mankind to develop artificial ways to mimic the remarkable properties of biological systems. In this work, a new method was explored to fabricate a biomimetic engineering surface comprising both the shark-skin, the shark body denticle, and rib morphology. It can help reduce water resistance and the friction contact area as well as accommodate lubricant. The lubrication theory model was established to predict the effect of geometric parameters of a biomimetic surface on tribological performance. The model has been proved to be feasible to predict tribological performance by the experimental results. The model was then used to investigate the effect of the grid textured surface on frictional performance of different geometries. The investigation was aimed at providing a rule for deriving the design parameters of a biomimetic surface with good lubrication characteristics. Results suggest that: (i) the increase in depression width ratio [Formula: see text] decreases its corresponding coefficient of friction, and (ii) the small coefficient of friction is achievable when [Formula: see text] is beyond 0.45. Superposition of depth ratio Γ and angle's couple under the condition of [Formula: see text] < 0.45 affects the value of friction coefficient. It shows the decrease in angle decreases with the increase in dimension depth [Formula: see text].

상어 표피 모사 리블렛 구조의 젖음성 평가

Shark skin has functionalities such as self-cleaning and antifouling; it also exhibits excellent drag reduction owing to a hierarchical structure of microgrooves and nanometer-long chain mucus drag reduction interfaces around the shark body. In this study, the wettability of a shark skin surface and its replicas are evaluated. First, a shark skin template is taken from a real shark. Then, shark skin replicas are produced directly from a shark skin template, using a micromolding technique. The quantitative replication precision of the shark skin replicas is evaluated by comparing the geometry of the shark skin template to the replica using 2D surface profiles. Contact angles at the solid-air-water interfaces are evaluated for the shark skin template and its replicas under two conditions: with and without hydrophobic coating. The results show that the microriblets on shark skin improve the hydrophobic feature and play a critical role in self-cleaning.

Three Dimensional Measurement of Shark Body Based on Monocular and Binocular Vision

To provide precise configuration reference for the engineering bionics, high accuracy detection in large field of view on the natural biological body is a prerequisite. Targeting the streamline body of carcharhinus brachyurous, 3D (three dimensional) measurement was carried out with monocular and binocular vision inspecting system based on sinusoidal structure light. By means of moving the vision sensor driven by a stepper motor, fringe patterns with variable fringe spacing were projected to every parts of the shark body, then the point clouds of different parts of the whole shark body were obtained. Using the quaternion method to joint the edges of these point clouds together, surface reconstruction was conducted. Finally the digital model of the low resistance body of shark was achieved. It would be useful reference for the configuration design of underwater vehicles, especially microminiature biomimetic underwater vehicles.

Scale morphology and flexibility in the shortfin mako Isurus oxyrinchus and the blacktip shark Carcharhinus limbatus

We quantified placoid scale morphology and flexibility in the shortfin mako Isurus oxyrinchus and the blacktip shark Carcharhinus limbatus. The shortfin mako shark has shorter scales than the blacktip shark. The majority of the shortfin mako shark scales have three longitudinal riblets with narrow spacing and shallow grooves. In comparison, the blacktip shark scales have five to seven longitudinal riblets with wider spacing and deeper grooves. Manual manipulation of the scales at 16 regions on the body and fins revealed a range of scale flexibility, from regions of nonerectable scales such as on the leading edge of the fins to highly erectable scales along the flank of the shortfin mako shark body. The flank scales of the shortfin mako shark can be erected to a greater angle than the flank scales of the blacktip shark. The shortfin mako shark has a region of highly flexible scales on the lateral flank that can be erected to at least 50°. The scales of the two species are anchored in the stratum laxum of the dermis. The attachment fibers of the scales in both species appear to be almost exclusively collagen, with elastin fibers visible in the stratum laxum of both species. The most erectable scales of the shortfin mako shark have long crowns and relatively short bases that are wider than long. The combination of a long crown length to short base length facilitates pivoting of the scales. Erection of flank scales and resulting drag reduction is hypothesized to be passively driven by localized flow patterns over the skin.

The characterization, replication and testing of dermal denticles of Scyliorhinus canicula for physical mechanisms of biofouling prevention

There is a current need to develop novel non-toxic antifouling materials. The mechanisms utilized by marine organisms to prevent fouling of external surfaces are of interest in this regard. Biomimicry of these mechanisms and the ability to transfer the antifouling characteristics of these surfaces to artificial surfaces are a highly attractive prospect to those developing antifouling technologies. In order to achieve this, the mechanisms responsible for any antifouling ability must be elucidated from the study of the natural organism and the critical surface parameters responsible for fouling reduction. Dermal denticles of members of the shark family have been speculated to possess some natural, as yet unidentified antifouling mechanism related to the physical presence of denticles. In this study, the dermal denticles of one particular member of the slow-swimming sharks, Scyliorhinus canicula were characterized and it was found that a significant natural variation in denticle dimensions exists in this species. The degree of denticle surface contamination was quantified on denticles at various locations and it was determined that the degree of contamination of the dorsal surface of denticles varies with the position on the shark body. In addition, we successfully produced synthetic sharkskin samples using the real skin as a template. Testing of the produced synthetic skin in field conditions resulted in significant differences in material attachment on surfaces exhibiting denticles of different dimensions.

Oceanic Sharks Clean at Coastal Seamount

Interactions between pelagic thresher sharks (Alopias pelagicus) and cleaner wrasse were investigated at a seamount in the Philippines. Cleaning associations between sharks and teleosts are poorly understood, but the observable interactions seen at this site may explain why these mainly oceanic sharks regularly venture into shallow coastal waters where they are vulnerable to disturbance from human activity. From 1,230 hours of observations recorded by remote video camera between July 2005 and December 2009, 97 cleaner-thresher shark events were analyzed, 19 of which were interrupted. Observations of pelagic thresher sharks interacting with cleaners at the seamount were recorded at all times of day but their frequency declined gradually from morning until evening. Cleaners showed preferences for foraging on specific areas of a thresher shark's body. For all events combined, cleaners were observed to conduct 2,757 inspections, of which 33.9% took place on the shark's pelvis, 23.3% on the pectoral fins, 22.3% on the caudal fin, 8.6% on the body, 8.3% on the head, 2.1% on the dorsal fin, and 1.5% on the gills respectively. Cleaners did not preferentially inspect thresher sharks by time of day or by shark sex, but there was a direct correlation between the amount of time a thresher shark spent at a cleaning station and the number of inspections it received. Thresher shark clients modified their behavior by “circular-stance-swimming,” presumably to facilitate cleaner inspections. The cleaner-thresher shark association reflected some of the known behavioral trends in the cleaner-reef teleost system since cleaners appeared to forage selectively on shark clients. Evidence is mounting that in addition to acting as social refuges and foraging grounds for large visiting marine predators, seamounts may also support pelagic ecology by functioning as cleaning stations for oceanic sharks and rays.

Genetic tools to support the conservation of the endangered smalltooth sawfish, Pristis pectinata

The smalltooth sawfish, Pristis pectinata, is protected under the US Endangered Species Act (ESA) and all forms of international trade of this species are prohibited under Appendix I of the Convention on International Trade in Endangered Species of Flora and Fauna (CITES). Although it is illegal to land or trade P. pectinata within the US or across its borders, it is difficult to enforce these regulations for some sawfish body parts because they resemble legally-traded shark body parts (e.g. dried fins). There is also a growing need for conservation genetics research on this species and its relatives, including assessments of population structure and genetic diversity. Given these pressing trade monitoring and research needs, we developed: (1) a rapid PCR-based test to identify P. pectinata body parts in trade in the US and western Atlantic, (2) a DNA-barcode based on 520 bp of cytochrome b that resolves P. pectinata and five other extant sawfish species and (3) a suite of 11 polymorphic P. pectinata microsatellite markers that can be used in a variety of conservation genetics applications for this and other sawfish species. We anticipate that this suite of genetic tools will contribute to the conservation of this critically endangered species and its relatives by reinforcing landings and trade restrictions and by enabling future conservation genetics research.

First record of albinism in the deep-water shark Dalatias licha

The first case of albinism in the kitefin shark, Dalatias licha, is reported here through the study of one specimen caught by professional bottom trawl in the Gulf of Genoa, Ligurian Sea. The albino surface was quantified and morphometric and meristic characteristics were compared with those of normal specimens of the same sex and equivalent length, caught within the same area. The shark body presented a partial reduction in pigmentation and no morphometric differences between the albino specimen and the normal individuals were observed.

Global-scale genetic identification of hammerhead sharks: Application to assessment of the international fin trade and law enforcement

The future status of sharks is an issue of widespread conservation concern due to declines in many species in the face of high levels of exploitation to satisfy market demands for products, especially fins. Substantial declines in the large-bodied hammerhead sharks, Sphyrna lewini, S. mokarran and S. zygaena, even in regions where some management occurs, indicate that informed conservation measures are warranted for these circumglobally distributed species. Despite the importance of assessing shark catch and trade on a species-specific basis to detect potential overexploitation of individual species, achieving this goal for hammerheads has proven elusive due to difficulties in identification of their products. Here, we present the development and application of a diagnostic, streamlined, five-primer multiplex polymerase chain reaction assay utilizing species-specific primers based on nuclear ribosomal ITS2 for the three hammerhead species throughout their global distribution. Application of this assay to investigations of the fin market confirmed the presence of hammerhead fins in the international trade. A study of the world’s largest fin market in Hong Kong revealed a high concordance between specific Chinese-name trade categories and fins from these three species (‘‘Bai Chun’’ with S. lewini, ‘‘Gui Chun’’ with S. zygaena and ‘‘Gu Pian’’ with S. mokarran), and clear species preferences. This concordance information allows the use of market records for monitoring species-specific trends in trade and exploitation rates. The assay is also proving useful for identification of shark body parts in U.S. fisheries law-enforcement activities. Screening of morphologically identified ‘‘ S. lewini’’ from globally distributed areas using this assay with subsequent whole ITS2 sequencing suggests a cryptic species closely related to S. lewini occurs off the SE USA coast.

Evaluation of shark cartilage in patients with advanced cancer

Shark cartilage has been a popular complementary or alternative medicine intervention. The basis for this popularity is the claim that sharks rarely get cancer because of the high proportion of cartilage in the shark's body. However, early studies were equivocal. Therefore, a clinical trial was conducted to look at the impact of shark cartilage in patients with advanced cancer. The primary goal of this trial was to determine whether a shark cartilage product improved overall survival for patients with advanced cancer who were getting standard care. Secondary research goals were to evaluate toxicities, tolerability, and quality of life associated with this shark cartilage product. The study was a two-arm, randomized, placebo-controlled, double-blind, clinical trial. Patients with incurable breast or colorectal carcinoma had to have good performance status and organ function. Patients could be receiving chemotherapy. Patients were all to receive standard care and then to be randomly selected to receive either a shark cartilage product or an identical-appearing and smelling placebo 3 to 4 times each day. Data on a total of 83 evaluable patients were analyzed. There was no difference in overall survival between patients receiving standard care plus a shark cartilage product versus standard care plus placebo. Likewise, there was no suggestion of improvement in quality of life for patients receiving the shark cartilage, compared with those receiving placebo. This trial was unable to demonstrate any suggestion of efficacy for this shark cartilage product in patients with advanced cancer.

A streamlined, bi-organelle, multiplex PCR approach to species identification: Application to global conservation and trade monitoring of the great white shark,Carcharodon carcharias

The great white shark, Carcharodoncarcharias, is the most widely protectedelasmobranch in the world, and is classified asVulnerable by the IUCN and listed on AppendixIII of CITES. Monitoring of trade in whiteshark products and enforcement of harvest andtrade prohibitions is problematic, however, inlarge part due to difficulties in identifyingmarketed shark parts (e.g., dried fins, meatand processed carcasses) to species level. Toaddress these conservation and managementproblems, we have developed a rapid, moleculardiagnostic assay based on species-specific PCRprimer design for accurate identification ofwhite shark body parts, including dried fins. The assay is novel in several respects: Itemploys a multiplex PCR assay utilizing bothnuclear (ribosomal internal transcribed spacer2) and mitochondrial (cytochrome b) locisimultaneously to achieve a highly robustmeasure of diagnostic accuracy; it is verysensitive, detecting the presence of whiteshark DNA in a mixture of genomic DNAs from upto ten different commercially fished sharkspecies pooled together in a single PCR tube;and it successfully identifies white shark DNAfrom globally distributed animals. Inaddition to its utility for white shark trademonitoring and conservation applications, thishighly streamlined, bi-organelle, multiplex PCRassay may prove useful as a general model forthe design of genetic assays aimed at detectingbody parts from other protected and threatenedspecies.

Function of the heterocercal tail in sharks: quantitative wake dynamics during steady horizontal swimming and vertical maneuvering.

The function of the heterocercal tail in sharks has long been debated in the literature. Previous kinematic data have supported the classical theory which proposes that the beating of the heterocercal caudal fin during steady horizontal locomotion pushes posteroventrally on the water, generating a reactive force directed anterodorsally and causing rotation around the center of mass. An alternative model suggests that the heterocercal shark tail functions to direct reaction forces through the center of mass. In this paper, we quantify the function of the tail in two species of shark and compare shark tail function with previous hydrodynamic data on the heterocercal tail of sturgeon Acipenser transmontanus. To address the two models of shark heterocercal tail function, we applied the technique of digital particle image velocimetry (DPIV) to quantify the wake of two species of shark swimming in a flow tank. Both steady horizontal locomotion and vertical maneuvering were analyzed. We used DPIV with both horizontal and vertical light sheet orientations to quantify patterns of wake velocity and vorticity behind the heterocercal tail of leopard sharks (Triakis semifasciata) and bamboo sharks (Chiloscyllium punctatum) swimming at 1.0Ls(-1), where L is total body length. Two synchronized high-speed video cameras allowed simultaneous measurement of shark body position and wake structure. We measured the orientation of tail vortices shed into the wake and the orientation of the central jet through the core of these vortices relative to body orientation. Analysis of flow geometry indicates that the tail of both leopard and bamboo shark generates strongly tilted vortex rings with a mean jet angle of approximately 30 degrees below horizontal during steady horizontal swimming. The corresponding angle of the reaction force is much greater than body angle (mean 11 degrees ) and the angle of the path of motion of the center of mass (mean approximately 0 degrees ), thus strongly supporting the classical model of heterocercal tail function for steady horizontal locomotion. Vortex jet angle varies significantly with body angle changes during vertical maneuvering, but sharks show no evidence of active reorientation of jet angle relative to body angle, as was seen in a previous study on the function of sturgeon tail. Vortex jet orientation is significantly more inclined than the relatively horizontal jet generated by sturgeon tail vortex rings, demonstrating substantial differences in function in the heterocercal tails of sharks and sturgeon. We present a summary of forces on a swimming shark integrating data obtained here on the tail with previous data on pectoral fin and body function. Body orientation plays a critical role in the overall force balance and compensates for torques generated by the tail. The pectoral fins do not generate lift during steady horizontal locomotion, but play an important hydrodynamic role during vertical maneuvering.

Genetic Identification of Pelagic Shark Body Parts for Conservation and Trade Monitoring

Abstract: The conservation and management of sharks on a species‐specific basis is a pressing need because of the escalating demand for shark fins and the recognition that individual shark species respond differently to exploitation. Difficulties with the identification of many commonly fished sharks and their body parts has resulted in a global dearth of catch and trade information, making reliable assessment of exploitation effects and conservation needs for individual species nearly impossible. We developed and tested a highly streamlined molecular genetic approach based on species‐specific, polymerase‐chain‐reaction primers in an eight‐primer multiplex format to discriminate simultaneously between body parts from six shark species common in worldwide pelagic fisheries. The species‐specific primers are based on DNA sequence differences among species in the nuclear ribosomal internal transcribed spacer 2 locus. The primers and multiplex format accurately and sensitively distinguished samples from each of three lamnid ( Isurus oxyrinchus, Isurus paucus, and Lamna nasus) and three carcharhinid ( Prionace glauca, Carcharhinus obscurus, and Carcharhinus falciformis) species from all but one other shark species encountered in the North Atlantic fishery. Furthermore, the three lamnid primers were robust enough in their discriminatory power to be useful for species diagnosis on a global scale. Preliminary testing of dried fins from Asian and Mediterranean commercial markets suggests that our genetic approach will be useful for determining the species of origin of detached fins, thus allowing the monitoring of trade in shark fins for conservation assessment. Our approach will also facilitate detection of products from protected and other at‐risk shark species and may prove useful as a model for development of the high‐throughput, genetic, species‐diagnosis methods typically required in conservation and management contexts.

Rapid and simultaneous identification of body parts from the morphologically similar sharks Carcharhinus obscurus and Carcharhinus plumbeus (Carcharhinidae) using multiplex PCR.

Many commercially exploited carcharhinid sharks are difficult to identify to species owing to extensive morphological similarities. This problem is severely exacerbated when it comes to identifying detached shark fins, and the finless and headless shark carasses typically sold in markets. To assist in the acquisition of urgently needed conservation and management data on shark catch and trade, we have developed a highly streamlined approach based on multiplex polymerase chain reaction (PCR) that uses species-specific primers derived from nuclear ribosomal ITS2 sequences to achieve rapid species identification of shark body parts. Here we demonstrate the utility of this approach for identifying fins and flesh from two globally distributed, morphologically very similar carcharhinid sharks (Carcharhinus obscurus and Carcharhinus plumbeus) intensively targeted in fisheries worldwide, and often confused for each other even as whole animals. The assay is conducted in a 4-primer multiplex format that is structured to simultaneously achieve the following efficiency and cost-reduction objectives: it requires only a single-tube amplification reaction for species diagnosis, it incorporates an internal positive control to allow detection of false-negative results, and it is novel in that it allows species identification even when DNAs from two species are combined in the same tube during the PCR reaction. The latter innovation reduces the required effort for screening a set of unknown samples by 50%. The streamlined approach illustrated here should be amenable for use in a shark conservation and management context where large numbers of samples typically need to be screened; the approach shown may also provide a model for a rapid diagnostic method applicable to species identification in general.

Analog VLSI system for active drag reduction

Drawing inspiration from the structure of shark skin, the authors are building a system to reduce drag along a surface. The entire question of active control of shark skin is speculative. Biologists hypothesize that sharks actively move their denticles. Indirect evidence of this is twofold. The denticles connect to muscles underneath the shark's skin. The total number of mechanoreceptive pressure sensors (pit organs) and their placement on a shark's body positively correlate with the speed of the species. For good active control, the shark may need many sensors to relay the current condition over its body. Although questions remain about sharks using active control, we concluded from this biological example that it may be beneficial to use controlled microscopic structures to reduce drag.

Body Form and Locomotion in Sharks

A revised interpretation of the mode of action of the heterocercal tail in sharks shows that the upturned tail axis tends to produce a thrust directed downwards behind the centre of balance of the fish and thus gives a moment turning the head upwards. This is countered in two ways—by the rotation of the tail along its longitudinal axis during each lateral beat, and through the action of the ventral hypochordal lobe. The shape of the tail and the mode of action of the tail in all sharks so far considered reflects a balance between these three factors, in all of them the net effect being the production of a forward thrust from the tail that passes directly through the centre of balance of the fiish. There is normally therefore no tendency for the fish to turn around the centre of balance in a sagittal plane but there is a net sinking effect that is countered by the planning effect of the pectoral fins and the ventral surface of the head. A study of 56 species of sharks shows that the tail is constructed according to a remarkably consistent common plan, the extremes being the high angled rather symmetrical tail of pelagic sharks such as hums, Lamna and Rhincodon and the straight tails of benthic sharks such as Ginglymostoma in which a ventral hypochordal lobe is absent. When the general body shape of sharks, including the position of insertion of the median and paired fins and the pattern of growth of fin surface areas is considered, the uniformity of the shark body plan and locomolor function is further emphasised. Four patterns of body form in sharks are recognised: 1) The fast swimming pelagic sharks and the whale sharks have a tail with a high aspect ratio, a conical head, a lateral fluke on the caudal peduncle. 2) The generalised sharks typified by the Carcharhinidae, have lower heterocercal angles, a flattened ventral surface on the head and lack the caudal fluke. 3) The demersal sharks typified by the catsharks (Scyliorhinidae) have a very low, almost straight tail. The ventral hypochordal lobe is absent and the first dorsal fin is posterior in position. 4) The squalomorph sharks are distinct in the absence of the anal fin, presence of a marked epicaudal lobe in the tail and often an elevated insertion of the pectorals. The anal and second dorsal fins are always the smallest fins and the pectorals grow at the fastest rate. In general there is an inverse relationship between size and rale of growth of all fins and the ventral surface of the head. In hammerheads the growth data confirms that the head has a significant planing action in swimming. The pectoral, second dorsal and anal fins show an extreme constancy of position of insertion in all sharks studied. The locomotor mechanism of sharks is adapted for an efficient cruising swimming but at the same time, the potential instability in the sagittal plan allows for the production of turning moments that are used in attack and feeding.

Morphologie und Ultrastruktur des Hai‐ “Schmelzes”

AbstractSharks at the cladodont and hybodont level (Paleozoic and Mesozoic) have blunt fangs and crushing teeth. These are covered by a thin sculptured uniform “enamel” cap, with a high compressive strength. The radiation of the modern sharks in the middle Mesozoic leads primarily to a broad spectrum of different sharks with a fang, or cutting tooth dentition. This radiation is accompanied by modifications of anatomical characters of the shark's body but also by the development of three new “enamel” types, which give the teeth bending and compressive strength.