Multi-fin kinematics and hydrodynamics in pufferfish steady swimming

Recent kinematic and hydrodynamic studies on fish median fins have shown that dorsal fins actively produce jets with large lateral forces. Because of the location of dorsal fins above the fish's rolling axis, these lateral forces, if unchecked, would cause fish to roll. In this paper we examine the hydrodynamics of trout anal fin function and hypothesize that anal fins, located below the fish's rolling axis, produce similar jets to the dorsal fin and help balance rolling torques during swimming. We simultaneously quantify the wake generated by dorsal and anal fins in brook trout by swimming fish in two horizontal light sheets filmed by two synchronized high speed cameras during steady swimming and manoeuvring. Six major conclusions emerge from these experiments. First, anal fins produce lateral jets to the same side as dorsal fins, confirming the hypothesis that anal fins produce fluid jets that balance those produced by dorsal fins. Second, in contrast to previous work on sunfish, neither dorsal nor anal fins produce significant thrust during steady swimming; flow leaves the dorsal and anal fins in the form of a shear layer that rolls up into vortices similar to those seen in steady swimming of eels. Third, dorsal and anal fin lateral jets are more coincident in time than would be predicted from simple kinematic expectations; shape, heave and pitch differences between fins, and incident flow conditions may account for the differences in timing of jet shedding. Fourth, relative force and torque magnitudes of the anal fin are larger than those of the dorsal fin; force differences may be due primarily to a larger span and a more squarely shaped trailing edge of the anal fin compared to the dorsal fin; torque differences are also strongly influenced by the location of each fin relative to the fish's centre of mass. Fifth, flow is actively modified by dorsal and anal fins resulting in complex flow patterns surrounding the caudal fin. The caudal fin does not encounter free-stream flow, but rather moves through incident flow greatly altered by the action of dorsal and anal fins. Sixth, trout anal fin function differs from dorsal fin function; although dorsal and anal fins appear to cooperate functionally, there are complex interactions between other fins and free stream perturbations that require independent dorsal and anal fin motion and torque production to maintain control of body position.

Four goldfish Carassius auratus morphotypes of similar length (50 mm): common (streamlined, full complement of paired and median fins, bifurcated caudal fin), comet ('common like' but with a long, deeply forked caudal fin), fantail (short, deep body with twinned caudal and anal fins) and eggfish (similar to the fantail but lacking a dorsal fin) were compared. Drag, steady swimming kinematics, energetics, fast-start performance, stability in yaw and roll and propulsive muscle ultrastructural characteristics were measured. A performance 'pairing' (common and comet; fantail and eggfish) was a recurrent theme for most performance variables. Fantail and eggfish drag were higher (requiring more thrust at any given velocity) than those for the more streamlined common and comet. This was reflected in kinematics; tailbeat frequency and stride length at any given velocity for the common and comet were lower and higher, respectively, than that of the fantail and eggfish. Common and comet fatigue times were not significantly different from those of their ancestor, crucian carp Carassius carassius, and higher than the fantail and eggfish. The cost of transport of the common and comet (c. 0. 6 mg O(2) kg(-1) m(-1)) was accurately predicted by the mass scaling relationship for fish, but values for the fantail and eggfish (c. 1. 3 mg O(2) kg(-1) m(-1)) were not. Rolling and yawing motions in eggfish (dorsal fin absent) during steady swimming were associated with significant energy losses. Eggfish maximum fast-start acceleration (c. 5 m s(-2)) was poor due to the absence of inertial and lifting contributions to thrust from the dorsal fin and energy wasting rolling motions. Common and comet fast-start performance (average velocity c. 0. 45 m s(-1), maximum velocity c. 1. 2 m s(-1), average acceleration c. 7. 5 m s(-2), maximum acceleration c. 35 m s(-2)) was similar to that of other locomotor generalists (e.g. rainbow trout Oncorhynchus mykiss). Artificially selected fishes can contribute to the understanding of form and movement in fishes and complement studies of the role of locomotor adaptations in natural systems.

A key evolutionary transformation of the locomotor system of ray-finned fishes is the morphological elaboration of the dorsal fin. Within Teleostei, the dorsal fin primitively is a single midline structure supported by soft, flexible fin rays. In its derived condition, the fin is made up of two anatomically distinct portions: an anterior section supported by spines, and a posterior section that is soft-rayed. We have a very limited understanding of the functional significance of this evolutionary variation in dorsal fin design. To initiate empirical hydrodynamic study of dorsal fin function in teleost fishes, we analyzed the wake created by the soft dorsal fin of bluegill sunfish (Lepomis macrochirus) during both steady swimming and unsteady turning maneuvers. Digital particle image velocimetry was used to visualize wake structures and to calculate in vivo locomotor forces. Study of the vortices generated simultaneously by the soft dorsal and caudal fins during locomotion allowed experimental characterization of median-fin wake interactions. During high-speed swimming (i.e. above the gait transition from pectoral- to median-fin locomotion), the soft dorsal fin undergoes regular oscillatory motion which, in comparison with analogous movement by the tail, is phase-advanced (by 30% of the cycle period) and of lower sweep amplitude (by 1.0 cm). Undulations of the soft dorsal fin during steady swimming at 1.1 bodylength s(-1) generate a reverse von Kármán vortex street wake that contributes 12% of total thrust. During low-speed turns, the soft dorsal fin produces discrete pairs of counterrotating vortices with a central region of high-velocity jet flow. This vortex wake, generated in the latter stage of the turn and posterior to the center of mass of the body, counteracts torque generated earlier in the turn by the anteriorly positioned pectoral fins and thereby corrects the heading of the fish as it begins to translate forward away from the turning stimulus. One-third of the laterally directed fluid force measured during turning is developed by the soft dorsal fin. For steady swimming, we present empirical evidence that vortex structures generated by the soft dorsal fin upstream can constructively interact with those produced by the caudal fin downstream. Reinforcement of circulation around the tail through interception of the dorsal fin's vortices is proposed as a mechanism for augmenting wake energy and enhancing thrust. Swimming in fishes involves the partitioning of locomotor force among several independent fin systems. Coordinated use of the pectoral fins, caudal fin and soft dorsal fin to increase wake momentum, as documented for L. macrochirus, highlights the ability of teleost fishes to employ multiple propulsors simultaneously for controlling complex swimming behaviors.

This study aims to characterize the charcoal from the fins waste of the Kerandang fish, namely from the dorsal (DF), pectoral (PF), ventral (VF), anal (AF), and caudal fin (CF). The charcoal as a source of hydroxyapatite. Qualitative characterization used a Scanning Electron Microscope (SEM), Fourier Transfer Infra-Red (FTIR), and X-Ray Diffraction (XRD). The charcoal’s chemical composition consists of Carbon, Oxygen, Sodium, Magnesium, Phosphor, Sulfur, and Chlorine, Potassium, and Calcium. The highest carbon element was 67.74% in the caudal fins. The lowest chemical element in the element sulfur is 0.197% in the dorsal fins. SEM photos show that the charcoal from the caudal fins has more pores than the other fins. The FTIR results show that the functional groups contained in the charcoal from the fins are NH, OH, CO, C=O, C=C, S1-O, and CH groups, with wave numbers 1032-1036 cm−1. The absorption area of the S1-O group (silica), where the silica group from charcoal, has the highest intensity. XRD results showed that the charcoal from fish fins of Kerandang contained 100% hydroxyapatite.

One of the most conspicuous characters of the ocean sunfishes, family Molidae, is the punctuation of the body by a deep, abbreviated, caudal fin-like structure extending vertically between the posterior ends of the dorsal and anal fins, termed the clavus by Fraser Brunner. Homology of the clavus has been a matter of debate since the first studies on molid anatomy in the early 1800s. Two hypotheses have been proposed: 1) It is a highly modified caudal fin; 2) It is formed by highly modified elements of the dorsal and anal fins. To resolve this homology issue, we studied the ontogeny of the molid vertebral column and median fins and compared it to that of a less morphologically derived gymnodont (see Part 1 of this study), a member of the family Tetraodontidae. We show that in molids the chorda never flexes during development, that the claval rays form from the posterior ends of the dorsal and anal fins toward the middle, thus closing the gap inward, and that elements of the molid clavus have an identical development and composition as the proximal-middle and distal radials of the regular dorsal and anal fins. We thus conclude that the molid clavus is unequivocally formed by modified elements of the dorsal and anal fin and that the caudal fin is lost in molids.

The thrust produced during an escape response (C-start) of a northern pike, Esox lucius (0.41 m total length, 0.398 kg), an acceleration specialist, is estimated using the Weihs model for fish fast-starts. High-speed cine film records (250 Hz) of pike C-starts were digitized and the angle of attack and displacement of all body sections determined. These parameters were incorporated into the model and thrust was calculated. A comparison of model predictions with values predicted from required forces found six of eight performance parameters to be within 22% for three fast-starts. A lack of significant difference between model estimates and required forces suggests that lift and acceleration forces are the major components of total thrust during C-type fast-starts. The caudal region, including the caudal, anal, and dorsal fins, contributes the most (>90%) to positive total thrust during the propulsive stage (stage 2). High velocities, large angles of attack, and large surface areas of these sections account for this. Approximately 77% of the positive total thrust during the propulsive stage is generated by the caudal fin and 28% by the anal and dorsal fins. Lift forces averaged over the fast-start are greater than average acceleration forces, but when positive acceleration forces of the propulsive stage only are considered, average lift and acceleration forces are similar (60 and 43% of total positive forces, respectively). Also, acceleration forces peak earlier than lift forces and contribute to an earlier escape response.

The ontogeny of the developmental stages of the hake Merluccius hubbsi is described. Fish larvae and post-transitional juveniles were collected in the Nor-Patagonian area from 1989 to 2004. The opening of the mouth and the pigmentation of the eyes are coincident with yolk resorption, finishing the yolk-sac stage. This species presents pigmentation on the head, trunk and tail typical of gadiform larvae. Pectoral fin development is completed during the transformation stage. The post-transitional juvenile stage begins when the fin-ray complements are complete and squamation begins. The fins become fully formed in the following sequence: pelvic fins, first dorsal fin, second dorsal and anal fins together, caudal fin and pectoral fins. The caudal complex is totally developed in larvae of 22.0-23.0 mm standard lengths (L(S)) and all vertebral elements are first observed in larvae of 8.5 mm L(S). The rate of development of M. hubbsi observed in this study could be faster than the rates reported for other species of Merluccius by different authors.

Acheilognathus nguyenvanhaoi Nguyen H. D., Tran D. H. & Ta T. T. sp. n. Holotype: MB-HNUE VI.1-F01; female, 51.4 mm SL; Vietnam: Quang Ninh Prov., Tien Yen River at Binh Lieu town; Nguyen Huu Duc et al., 14 March 2011. Paratype: 1 MB-HNUE VI.1-F02, male, 60.5 mm SL. Same data as holotype. Diagnosis: When Acheilognathus nguyenvanhaoi sp. n. is compared with closely related species of Acheilognathus, it is characteristic in the five following traits: a broad and dark longitudinal stripe on body (both sides) running from tip of snout to tip of middle caudal fin rays, not tapering anteriorly vs. a narrower and lighter one running most anteriorly behind operculum to caudal base, tapering anteriorly; pharyngeal teeth (5.1-0.5, vs. 5-5); spiny rays of dorsal and anal fins (III-IV, vs. III) and scales above lateral line (7, vs less than 6). The new species differed from A. meridianus and A. barbatus in number of predorsal scales; from A. meridianus, A. barbatulus and A. melanogaster in number of vertebrae; from A. melanogaster in lenght of barbel; from A. brevicaudatus and A. melanogaster in number of gill rackers on the outer side of the first gill arch and from A. barbatulus and A. melanogaster in proportion between anterior and posterior length of gas-bladder. Description: SL = 3.09-3.13 BD = 4.48-4.62 HL = 1.97-2.02 PDL = 4.05-4.84 LCP = 7.76-8.48 CPD; HL = 2.76-3.05 OD = 2.70-2.76 IOW. Body compressed. Mouth sub-inferior. Barbels present. Dorsal fin with 3-4 non-segmented spiny soft rays and 9 branched rays. Anal fin with 3-4 non-segmented spiny soft rays and 10-11 branched rays. Pectoral fin with one segmented spiny soft ray and 11 branched rays. Pelvic fin with one segmented spiny soft ray and 7 branched rays. Lateral line complete with 36-37 pored scales. Predorsal scales 13-14; Scales around caudal peduncle 14-15; Gill rakers on external side of first gill arch 9; Pharyngeal teeth 5.1-0.5. Vertebrae 37-38. Inserted position of first proximal pterygiophores in the dorsal and anal fins as 10th-11th and 18th, respectively. Colour in preservative: Body yellowish. A board longitudinal dark stripe on body running from the tip of snout to the tip of the middle caudal fin rays, not tapering anteriorly. Distribution: Presently known only from the Tien Yen river, Quang Ninh province, Northern Vietnam at Binh Lieu town. Etymology: Named for Nguyen Van Hao, a Vietnamese ichthyologist.

The objective of this study was to taxonomically revise the 41 nominal species found within the Brachirus species complex (Order Pleuronectiformes; Family Soleidae). This complex is recognizable by a combination of characters: the structure of the supracranial portion of the dorsal fin which lack pterigiophores with their proximal ends directly over the cranium, by the joined dorsal, anal and caudal fins, and by the anterior tip of the dorsal fin almost reaching the upper jaw. This revision is based on the morphological and meristic examination of 34 type and 717 non-type specimens for all available nominal species. The type material was examined for twenty species. The remaining species were assessed from the original type description. It was found that the Brachirus species complex is made up of four genera including 19 valid species: Brachirus (14), Achiroides (1), Dexillus (3), and Paradicula (1). Eight of the nominal species do not belong to the Brachirus species complex and have been removed from the scope of this study. Achiroides, characterized by the rudimentary pectoral fins, contains a single valid species, A. melanorhynchus (Bleeker 1851) and three synonyms (Synaptura aenea Smith 1931, Anisochirus harmandi Sauvage 1878, and Plagusia leucorhynchos Bleeker 1851). Dexillus , characterized by the close proximity of the eyes, contains three valid species: D. macrolepis (Bleeker 1858), D. megalepidoura (Fowler 1934), and D. muelleri (Steindachner 1879). D. muelleri is a senior synonym of the nominal species Synaptura arafurensis Gunther 1880. Paradicula, unique in having the gill openings restricted to the base of the pectoral fins, contains a single valid species, P. setifer Paradice & Whitley 1927. The remaining Brachirus species cannot yet be defined as being monophyletic. Brachirus contains 14 valid species: B. aspilos (Bleeker 1852) (synonyms: Synaptura heterolepis Bleeker 1856, S. marmorata Bleeker 1853, and S. sorsongonensis Evermann & Seale 1907), B. sundaicus (synonyms: Bleeker 1870--75) (Synaptura cinerea De Vis 1883 and S. nigra MacLeay,1880), B. selheimi (Macleay 1882) (synonyms: B. salinarum Ogilby 1910, and Synaptura villosus Weber 1907), B. foliacea (Gunther 1862) (synonym: Synaptura filamentosa Sauvage 1878), B. siamensis (Sauvage 1878) (synonyms: Synaptura krempfi Durand 1940 and Chabanaudetta smithi Joglekar 1971), B. breviceps Ogilby 1910, B. cinerascens (Gunther 1862), B. fitzroiensis (De Vis 1882), B. orientalis (Bloch & Schneider 1801), B. pan (Hamilton 1822), B. panoides (Bleeker 1851), B. dicholepis Peters 1877, B. swinhonis Steindachner 1867, and B. canus Gray 1854. An identification key of valid species belonging to the Brachirus species complex is provided.

Frontiers Events is a rapidly growing calendar management system dedicated to the scheduling of academic events. This includes announcements and invitations, participant listings and search functionality, abstract handling and publication, related events and post-event exchanges. Whether an organizer or participant, make your event a Frontiers Event!

Fast-start performance of eight groups of rainbow trout with various fin-rays removed was measured to test the hydromechanical theory (Weihs, 1973) that large fins are required for acceleration. A trend towards decreasing performance was found for the following sequence of fin-ray amputations: control (pelvic rays amputated); dorsal fin; anal fin; dorsal lobe of caudal fin and ventral lobe of caudal fin; ventral lobe of caudal fin and anal fin; dorsal and ventral lobes of caudal fin; both caudal-fin lobes and anal fin. The series represents progressive reduction in fin and body area, as well as reduction in these areas where lateral movements are largest. Effects of fin amputation on performance were statistically significant (P > 0·05) in comparison with controls only for the last three groups lacking the caudal fin. The results confirm the hydromechanical theory, and lead to the conclusion that mechanically optimum lateral body profiles for faststart and for steady (cruising and sprint) performance are mutually exclusive. This mechanical restriction can be circumvented only in bony fish, with the evolution of flexible, collapsible fins that permit major variation in lateral body profile.

Locomotion in tetraodontiform fishes (puffers and relatives) involves the use of multiple fins for propulsion during swimming. A variety of tertraodontiform swimming modes have been defined, but the contributions of pectoral, dorsal, anal, and caudal fins to the propulsion in these fish remain largely unknown. We used video analysis to study swimming behaviour of the striped burrfish ( Chilomycterus schoepfi ). Burrfish swam in a flow tank at speeds of 0.5–6.3 standard body lengths per second, during which all fins oscillated at all speeds. The oscillation frequency range of all fins was 2.1–9.2 Hz, increasing with velocity. Pectoral fins were always out of phase, usually by 180 degrees (alternate left and right beats). Reduced frequency parameters for all fins were high (0.65–12.1) indicating that acceleration reaction is the dominant mechanism of thrust. Phase lag between anal and caudal fins assumed three distinct states which suggests that burrfishes alter the patterns of fin motion in discrete stages analogous to gaits. Rapid oscillation of five fins in various degrees of asynchrony is a mechanism to produce relatively constant thrust from multiple periodic motions.

We have been successfully developing Artificial Intelligence (AI) models for automatically classifying fish species using neural networks over the last three years during the “Biology Guided Neural Network” (BGNN) project*1. We continue our efforts in another broader project, “Imageomics: A New Frontier of Biological Information Powered by Knowledge-Guided Machine Learning”*2. One of the main topics in the Imageomics Project is “Morphological Barcoding”. Within the Morphological Barcoding study, we are trying to build a gold standard method to identify species in different taxonomic groups based on their external morphology. This list of characters will contain, but not be limited to, landmarks, quantitative traits such as measurements of distances, areas, angles, proportions, colors, histograms, patterns, shapes, and outlines. The taxonomic groups will be limited by the data available, and we will be using fish as the topic of interest in this preliminary study. In this current study, we have focused on extracting morphological characters that are relying on anatomical features of fish, such as location of the eye, body length, and area of the head. We developed a schematic workflow to describe how we processed the data and extract the information (Fig. 1). We performed our analysis on the segmented images produced by Karpatne Team within the BGNN project (Bart et al. 2021). Segmentation analysis was performed using Artificial Neural Networks - Semantic Segmentation (Long et al. 2015); the list of segments to be detected were given as eye, head, trunk, caudal fin, pectoral fin, dorsal fin, anal fin, pelvic fin for fish. Segmented images, metadata and species lists were given as input to the workflow. During the cleaning and filtering subroutines, a subset of data was created by filtering down to the desired segmented images with corresponding metadata. In the validation step, segmented images were checked by comparing the number of specimens in the original image to the separate bounding-boxed specimen images, noting: violations in the segmentations, counts of segments, comparisons of relative positions of the segments among one another, traces of batch effect; comparisons according to their size and shape and finally based on these validation criteria each segmented image was assigned a score from 1 to 5 similar to Adobe XMP Basic namespace. The landmarks and the traits to be used in the study were extracted from the current literature, while mindful that some of the features may not be extracted successfully computationally. By using the landmark list, landmarks have been extracted by adapting the descriptions from the literature on to the segments, such as picking the left most point on the head as the tip of snout and top left point on the pelvic fin as base of the pelvic fin. These 2D vectors (coordinates), are then fine tuned by adjusting their positions to be on the outline of the fish, since most of the landmarks are located on the outline. Procrustes analysis*3 was performed to scale all of the measurements together and point clouds were generated. These vectors were stored as landmark data. Segment centroids were also treated as landmarks. Extracted landmarks were validated by comparing their relative position among each other, and then if available, compared with their manually captured position. A score was assigned based on these comparisons, similar to the segmentation validation score. Based on the trait list definitions, traits were extracted by measuring the distances between two landmarks, angles between three landmarks, areas between three or more landmarks, areas of the segments, ratios between two distances or areas and between a distance and a square rooted area and then stored as trait data. Finally these values were compared within their own species clusters for errors and whether the values were still within the bounds. Trait scores were calculated from these error calculations similar to segmentation scores aiming selecting good quality scores for further analysis such as Principal Component Analysis. Our work on extraction of features from segmented digital specimen images has shown that the accuracy of the traits such as measurements, areas, and angles depends on the accuracy of the landmarks. Accuracy of the landmarks is highly dependent on segmentation of the parts of the specimen. The landmarks that are located on the outline of the body (combination of head and trunk segments of the fish) are found to be more accurate comparing to the landmarks that represents inner features such as mouth and pectoral fin in some taxonomic groups. However, eye location is almost always accurate, since it is based on the centroid of the eye segment. In the remaining part of this study we will improve the score calculation for segments, images, landmarks and traits and calculate the accuracy of the scores by comparing the statistical results obtained by analysis of the landmark and trait data.

A new species of the characid genus Astyanax is described from a man-made small channel connected with the Rio Grande basin, in Jujuy Province, northwestern Argentina. This species can be distinguished from its congeners by the following combination of characters: body relatively high (39.2-45.3% SL); head short and heavy (24.0-26.7% SL); snout very short (16.1-20.8% HL); eye small (28.9-35.0% HL); interorbital very wide (38.8-44.1% HL); mouth sub-superior; maxilla short with 1-2 teeth; iii-v, 19-22 anal fin rays; 33-36 perforated scales on the lateral line, and a distinctive color pattern, consisting in a reticulated body, with dorsal, pelvic, anal, and caudal fins with dark margins. A very narrow lateral dark stripe ending in a caudal spot, and one large vertically elongated humeral spot. In addition the males of Astyanax tumbayaensis have bony hooks in the dorsal, pelvic, anal and caudal fins. A key for Argentinean species of Astyanax is provided. The primary traits of the distribution of species in the country are discussed, with reference to the main basins and some zoogeographically important localities.

Chondrostoma olisiponensis sp. nov. is described from the lower Rio Tejo Basin. It is a small species (all specimens examined less than 105mm SL) distinguished from the other species of Chondrostoma s.l. by the following combination of characters. Chondrostoma olisiponensis lacks a horny blade on the lower jaw, has a pronouncedly arched mouth, and lacks an intense reddish coloration at the base of the fins. It has elongated pelvic fins that reach the anus and often pass the anal-fin insertion in males, and dorsal, pelvic and anal fins usually have 8 branched rays. The new species has 36 to 43 scales in the lateral line, 7.0 to 8.5 scales above the lateral line, 13 to 16 circumpeduncular scales, denticulated (vs. smooth) grinding teeth surfaces, 6-5/5 pharyngeal teeth and 15 to 19 gill rakers. Chondrostoma olisiponensis is further distinguished from C. lusitanicum, a phylogenetically close species that lives in the same area, by having a higher body, a relatively longer head, and a larger eye. The origins of anal and pelvic fins are displaced anteriorly, while the origin of pectoral fins is displaced posteriorly. Pelvic and pectoral fins and last anal-fin ray are longer in the new species. Unlike the other species in the genus, C. olisiponensis shows external sexual dimorphism, with males having longer pelvic fins whose extremities pass the anus and often overlap with the anal fin. This description raises concerns on the recently proposed splitting of Chondrostoma s.l. since the morphological traits deemed characteristic of some genera are unsuitable for their diagnosis. The species should be considered Critically Endangered (CR) according to IUCN criteria B1ab(ii,iii,iv)c(iv)+2ab(ii,iii,iv)c(iv).