Caudal Fin Area Research Articles

Effects of caudal fin size on tail-flip jump performance

Fishes are generally considered to be fully aquatic, but some voluntarily strand themselves on land to escape poor water conditions, predators, or to exploit terrestrial niches. The tail-flip jump is a method of terrestrial locomotion performed by small fishes without apparent morphological specialization, but few studies have investigated the role the caudal fin has on the tail-flip jump. We hypothesized that fish with larger caudal fins would perform shorter individual tail-flip jumps and not be able to sustain jumping in extended terrestrial excursions. Zebrafish (Danio rerio) are an excellent model to investigate this because these fish perform the tail-flip jump and some strains have been selectively bred in the pet trade industry for larger fins. In this study, wildtype and longfin zebrafish were compared because of the larger caudal fins of the longfin zebrafish. Individuals of each strain performed three consecutive jump trials with 48 h between each trial: kinematic, voluntary, and exhaustion. The kinematic trial used a high-speed camera to measure kinematic variables of individual jumps. The voluntary trial recorded each fish’s voluntary response to stranding for three minutes. The exhaustion trial recorded the fish’s response to be constantly elicited to jump until exhaustion was reached. Despite differences in caudal fin area, there were no differences in the kinematic characteristics of individual jump performances, including jump distance. However, wildtype zebrafish performed more jumps, jumped more than they flopped, and moved a greater total distance in both voluntary and exhaustion trials despite moving for similar durations and reaching exhaustion at similar times. These findings imply that larger fins do not affect a fish’s ability to perform individual tail-flip jumps but does cause fish to employ different behavioral strategies when stranded for longer durations on land.

Scaling of fast-start performance and its thermal dependence in mummichog Fundulus heteroclitus.

Fast-start predator-escape performance and its sensitivity to temperature (24, 30, and 36°C) were evaluated in mummichog Fundulus heteroclitus across a range of body sizes spanning YOY to adult (35-68 mm standard length). Mummichogs exhibit isometry of body dimensions and areas of the dorsal and anal fins but negative allometry of the caudal fin area. These scaling relationships are consistent with observed decreases in fast-start angular velocities with increasing body size. Linear velocity, on the contrary, does not vary with size, and both large and small mummichogs are capable of traversing similar distances in a given amount of time. In addition, temperature influences fast-start performance in similar ways over the size range, though the magnitude of the effect varies with size for some performance measures. In general, fast-start performance increases with test temperature, but mummichogs acclimated to warmer temperatures exhibit lower performance at each test temperature. Altogether, our results suggest that mummichogs across the adult size range may suffer decreases in their predator-escape performance as increasing sea temperatures combine with short-term temperature fluctuations in the estuaries these fish occupy.

Hammer it out: shifts in habitat are associated with changes in fin and body shape in the scalloped hammerhead (Sphyrna lewini)

Abstract Major shifts in habitat often occur during life history and can have significant impacts on the morphology and function of an animal; however, little is known about how such ecological changes influence the locomotor system of large aquatic vertebrates. Scalloped hammerheads (Sphyrna lewini) are large sharks found in warm temperate and tropical waters. Smaller scalloped hammerheads are generally found in near-shore habitats, but as they grow larger, individuals spend time in deep-water, pelagic habitats. We measured a number of morphological traits of scalloped hammerheads, ranging from 32 to 130 cm, to determine whether there are allometric changes in morphology in association with this shift in habitat. We found that head morphology, caudal fin area and lateral span scaled with negative allometry, whereas the lengths of their pectoral, dorsal and caudal fins, and their pectoral and caudal fin aspect ratios, scaled with positive allometry. Furthermore, the largest shark in our dataset exhibited an optimal body fineness ratio for locomotor efficiency. This suggests that the changes in ecology have profound influences on the functional morphology of scalloped hammerheads. We discuss how these drastic morphological changes relate to potential changes in scalloped hammerhead swimming function and performance.

Phenotypic response of male and neomale of O. mykiss parr subjected to 8º and 16 ºC water temperature during early life stage

Water temperature is an important modulator of variation of phenotype in poikilothermic fish and therefore of body shape. The present study explores the phenotypic response of commercial O. mykiss parr when they are subjected to rearing temperatures of 8º and 16ºC under controlled conditions with the aim of demonstrating, with the use of Landmark-Based Geometric Morphometrics, the influence of rearing temperature on body shape. O. mykiss males and neomales from eggs to parr stages, belonging to the same family and strain, were reared at different temperatures (8ºC and 16ºC) and grouped according to: Group 16ºC/neomales (n = 15), Group 16ºC/males (n = 15), Group 8ºC/neomales (n = 15) and Group 8ºC/males (n = 15). Differences in body shape among sex and rearing temperatures were examined by geometric morphometrics and traditional morphometry. At 16 weeks, geometric morphometric analysis revealed a dimorphism, which was not detected by traditional morphometry, mainly in the dorsal and caudal fin area. This dimorphism was not observed in neomales. This difference may be the product of the potential for phenotypic plasticity and adaptation to genetically controlled environmental and local fluctuations, which affects to indicators of adaptation in unfavorable environmental conditions such a biomechanical action of swimming and propulsion. In conclusion, this study demonstrates the differential effect of 8º and 16ºC water temperature on lateral body shape in male O. mykiss parr during the early stages of body development and in controlled conditions.

Estimation of genetic parameters for body areas in Nile tilapia measured by digital image analysis.

Digital image analysis is a practical, non-invasive, and relatively low-cost tool that may assist in the evaluation of body traits in Nile tilapia, being particularly useful for assessing difficult-to-measure variables, such as body areas. In this study, we aimed to estimate variance components and genetic parameters for body areas of Nile tilapia obtained by digital images. The data set comprised body weight (BW) records of 1,917 pond-reared fish at 366days of age. Of this total, 656 animals were photographed and subjected to image analysis of trunk area (TA), head area (HA), caudal fin area (CFA) and fillet area (FA). Heritabilities and genetic correlations were estimated through multiple-trait models based on Bayesian inference. Heritability estimates for BW, TA, HA, CFA and FA were 0.25, 0.23, 0.26, 0.21 and 0.25, respectively. Genetic correlations between the traits were high and positive, ranging from 0.70 to 0.98. We highlight the genetic correlation between BW and TA (rG =0.98) and FA (rG =0.97). In view of the observed results, it can be concluded that trunk and fillet areas obtained by digital image analysis can lead to indirect genetic gains in weight and other body areas. In addition, the areas studied have potential as a selection criterion and may assist in studies on changes in the body shape in Nile tilapia.

Skeletal deformities and meristic trait variations are common in the intertidal fish Bathygobius cocosensis (Perciformes-Gobiidae).

Extreme environmental conditions, such as temperature, can lead to meristic trait variation and skeletal deformities, which may have major impacts on individual fitness. As intertidal ecosystems experience rapid temperature and physicochemical fluctuations, intertidal fish living and reproducing in these environmental conditions may have phenotypes influenced by such variable environments. The impact of intertidal variability on fish development, however, has not been previously investigated. Skeletal deformities and meristic traits were assessed for Bathygobius cocosensis, a common intertidal fish living across the Indo-Pacific region, using a clearing and staining method on 72 individuals. Over 87% of individuals presented meristic variation and over 70% exhibited at least one type of skeletal deformity, mostly recorded in the caudal fin area. The unexpected prevalence of skeletal deformities among this intertidal fish population suggests that such deformities may be suitable markers to evaluate an individual's stress exposure during development and the subsequent fitness effects.

First evidence of ganoin-scaled Halecomorphi (Neopterygii) in the Lower Jurassic of Holzmaden and Ohmden, Germany

The Posidonienschiefer Formation (lower Toarcian) of the Holzmaden region, Baden-Württemberg, in southwestern Germany is world- famous for its marine fossils, including excellently preserved fossil vertebrates, especially ichthyosaurs and plesiosaurs, but also fossil fishes. The study of the diversity and palaeoecology of fish within these deposits gives us further hints to understand the corresponding ecosystem. With Holzmadenfuro rebmanni new gen. et sp. and Ohmdenfuro bodmani new gen. et sp., both curated at the Urweltmuseum Hauff in Holzmaden, we now describe the first ganoin-scaled Halecomorphi from the Posidonienschiefer of Germany. These new taxa are characterized by a specific combination of features, including body shape; number of parietals, extrascapulars, infraorbitals, dorsal and caudal fin rays, and vertical scale rows; number and shape of maxillary teeth; number and arrangement of supraorbitals; ornamentation of skull bones; insertion of dorsal, pelvic, and anal fins; position of lateral line in caudal fin area; shape and distribution of scales; and number and shape of serrations on scales. The more basal Halecomorphi with ganoid scales (Parasemionoti- formes, Panxianichthyformes, and Ophiopsiformes) remain poorly known, compared with the more advanced halecomorph group of the Amiiformes (especially the Amiidae). Closer investigation of their taxonomic relationships is therefore important for understanding broader patterns of haleco- morph evolution, especially the origin of the Jurassic Ophiopsiformes.

Zandtfuro and Schernfeldfuro, new genera of Halecomorphi (Actinopterygii) from the Upper Jurassic Solnhofen Archipelago

ABSTRACTIn the Late Jurassic Plattenkalk deposits of the Solnhofen Archipelago and of Nusplingen (both southern Germany), there are a considerable number of as yet undescribed genera and species of ganoin-scaled Halecomorphi. Some species were preliminarily assigned to the genus ‘Furo’; however, as noted by previous authors, the taxon ‘Furo’ is not a monophyletic genus. A description of two new genera and species, Zandtfuro tischlingeri and Schernfeldfuro uweelleri is presented here, with further descriptions of new species to follow separately. These new taxa are characterized by a specific combination of features, including: body shape; number of suborbital bones, infraorbitals, extrascapulars, dorsal and caudal fin rays, and vertical scale rows; number and shape of maxillary teeth; presence or absence of sclerotic ring ossification; shape of the ventral postinfraorbital; insertion of dorsal, pelvic, and anal fins; position of lateral line in caudal fin area; and shape and distribution of scales. The more basal Halecomorphi with massive ganoin scales (Parasemionotiformes, Panxianichthyformes, and Ophiopsiformes) remain poorly known, compared with the more advanced halecomorph group of the Amiiformes (especially the Amiidae). Closer investigation of their taxonomic relationship is therefore important for understanding broader patterns of halecomorph evolution.

The ontogenetic scaling of form and function in the spotted ratfish, Hydrolagus colliei (Chondrichthyes: Chimaeriformes): Fins, muscles, and locomotion

The alteration of form and function through the life of a fish can have profound impacts on the ability to move through water. Although several studies have examined morphology and function in relation to body size, there is a paucity of data for chondrichthyans, an ancient group of fishes. Ratfishes are interesting in that they utilize flapping pectoral fins to drive movement, and they diverged from elasmobranchs early in the gnathostome phylogeny. Using the spotted ratfish, Hydrolagus colliei, we quantified the scaling of traits relevant for locomotion, including median and paired fin external anatomy, the musculature of the pectoral and pelvic fins, and the kinematics of the pectoral fins. Whereas pelvic fins scaled with either positive allometry (fin span and area) or isometry (fin chord length at the base of the fin), pectoral fin measurements either scaled with negative allometry (fin span and aspect ratio) or isometry (fin area and chord length). Correspondingly, all pelvic fin muscles exhibited positive allometry, whereas pectoral muscles exhibited a mix of isometric and positively allometric growth. Caudal fin area and body frontal area both scaled with positive allometry, whereas dorsal fin area and span scale with isometry. Pectoral fin amplitude during swimming exhibited isometry, and fin beat frequency decreased with body size. Our results highlight the complex changes in form and function throughout ontogeny. Finally, we highlight that hierarchical differentiation in morphology can occur during growth, potentially leading to complex changes in performance of a functional system.

Environmentally relevant concentrations of the flame retardant tris(1,3-dichloro-2-propyl) phosphate change morphology of female zebrafish

Tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) was considered as a re-emerging environmental pollutant, and accumulated evidences suggested that it was global distributed in various environmental media. However, effect of TDCIPP on fish morphology remained largely unknown. In this study, one-month old zebrafish (Danio rerio) were exposed to 0, 0.05, 0.5 or 5 μg/L TDCIPP for 120 days, and effects on fish morphology and expressions of genes included in the development of muscle and bone were examined. Using landmark-based geometric morphometrics, we found that environmentally relevant concentrations of TDCIPP altered morphology of female zebrafish. Furthermore, TDCIPP decreased the ratio of caudal fin area to whole body area and muscle density. These effects were possibly resulted from the alteration in the expression of genes included in the development of muscle (myf5 and myog) and bone (bmp2b and bmp4).

Body shape and robustness response to water flow during development of brown trout Salmo trutta parr.

Domesticated brown trout Salmo trutta parr were subjected to increased, variable flow under controlled experimental conditions. Using geometric morphometric analyses, K¯(a mass–length index) and caudal fin area–body length ratio, this study assessed morphological responses in lateral body depth, growth and robustness and propulsive potential, respectively, of parr over the course of 32 weeks. Geometric morphometric analyses did not reveal an effect of exercise on either lateral body depth or caudal fin area. However, improved overall robustness and growth trajectories in exercised parr showed a positive adaptive response to the enriched habitat. Exercise and habitat heterogeneity thus have the potential to improve survivability of domesticated salmonids in the wild.

Upstream range expansion by invasive round gobies: Is functional morphology important?

Range expansion by invasive taxa can be facilitated by a wide variety of life history traits, by behavioral repertoires, or via human-aided translocation. The round goby (Neogobius melanostomus) continues to expand its range in Europe and the Great Lakes watershed by moving upstream in tributary rivers and streams. It is not clear whether in-stream barriers (e.g., waterfalls, culverts, dams) will prevent further upstream expansion. Since other species within the Gobiidae are adept waterfall climbers, we investigated whether body scaling morphometrics, fused pelvic fin adhesion, or swimming patterns in round gobies were suggestive of climbing capability. Behaviorally, round gobies swam less frequently, limited their swimming mode to caudal thrusts, and sought shelter more as velocity increased. Attachment to the substrate via the fused pelvic fins was documented in a laboratory flume. Fish smaller than 5 cm or having a body mass less than 1.5 g had passive pelvic fin adhesion power sufficient to remain in place on a wetted, inclined plane, whereas larger fish did not. Small fish had significantly smaller pelvic fin area/length ratios relative to larger fish (P < 0.001), but significantly greater pelvic fin area/mass ratios (P < 0.001). Caudal fin area, but not fused pelvic fin area, exhibited an allometric growth pattern versus weight in large gobies, whereas neither caudal nor pelvic fin area showed allometric increases versus weight in small round gobies. Pelvic fin area in both large and small fish grew allometrically compared to length, whereas caudal fin area increased allometrically relative to length only in small fish. Fin morphometric results suggest, theoretically, that neither adults nor juveniles have pelvic fin areas large enough to support their weight against gravity forces, but the areas are sufficient to withstand hydraulic drag forces. Collectively, our results suggest that in-stream barriers which force fish to overcome gravity should be impassable, but that barriers allowing fish to remain submerged could be navigable.

尾鳍缺失和恢复生长对不同生境的两种鲤科鱼类快速启动游泳能力的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 尾鳍缺失和恢复生长对不同生境的两种鲤科鱼类快速启动游泳能力的影响 DOI: 10.5846/stxb201305171097 作者: 作者单位: 重庆师范大学 进化生理与行为学实验室 动物生物学重庆市重点实验室,重庆师范大学 进化生理与行为学实验室 动物生物学重庆市重点实验室,重庆师范大学 进化生理与行为学实验室 动物生物学重庆市重点实验室 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目(31172096);重庆市自然科学基金重点项目(cstc2013jjB20003);重庆市教委科研项目(KJ130624) The effects of caudal fin loss and regeneration on fast-start performance in juveniles of two cyprinid fish species Author: Affiliation: Laboratory of Evolutionary Physiology and Behaviour,Chongqing Key Laboratory of Animal Biology,Chongqing Normal University,Laboratory of Evolutionary Physiology and Behaviour,Chongqing Key Laboratory of Animal Biology,Chongqing Normal University,Laboratory of Evolutionary Physiology and Behaviour,Chongqing Key Laboratory of Animal Biology,Chongqing Normal University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为了考查尾鳍切除及其恢复生长对偏好静水环境的鲫鱼(Carassius auratus)与偏好激流环境的宽鳍鱲(Zacco platypus)两种鲤科鱼类快速启动游泳能力的影响,将鲫鱼幼鱼((6.34 ± 0.02) cm)和宽鳍鱲幼鱼((6.26 ± 0.12) cm)各16尾,其中8尾在(25.0 ± 0.5) ℃的条件下分别进行尾鳍切除、20 d恢复生长、再次切除处理,另外8尾作为对照组;测量计算两种实验鱼的相关形态参数并采用电刺激方式,通过高速摄像机获取实验鱼的影像资料,分析计算后获得快速启动相关参数。结果显示:鲫鱼的细度比(FR)显著小于宽鳍鱲(P < 0.01),尾鳍指数(FI)却显著大于宽鳍鱲(P < 0.01),两种实验鱼的快速启动最大线速度(Vmax)、移动距离(d)、相对旋转半径(RTr)和弯曲指数(BC)均无显著差异;尾鳍切除后,两种实验鱼快速启动的Vmax、d和RTr与正常组相比均呈现显著下降(P < 0.01),其中鲫鱼Vmax下降39%而宽鳍鱲下降24%;经过20 d的恢复生长,两种实验鱼的尾鳍面积均恢复至切除前的60%,而快速启动的Vmax、d、RTr和BC却与正常组(同样经过20 d生长)无显著差异;尾鳍再次切除后与正常组相比,鲫鱼和宽鳍鱲Vmax的下降幅度(17%和9%)与首次切除后的(39%和24%)相比均呈现降低的趋势,其中鲫鱼的下降幅度更大;尾鳍再次切除后与正常组相比,宽鳍鱲的BC显著增大(P = 0.046)。结果表明:(1)鲫鱼尾鳍对快速启动能力的作用大于宽鳍鱲;(2)而偏好急流环境的宽鳍鱲经过恢复生长表现出更加明显的功能补偿现象。 Abstract:Swimming performance is an important capacity for fish species because it is closely related to the ability to gain food, to predator avoidance and to other daily activities. As an important locomotive organ for most fish species, the caudal fin plays a crucial role in propelling and guiding fish during swimming and thus the shape, size and stiffness of the caudal fin are all expected to strongly affect swimming performance. In nature, the caudal fins of fish species are frequently lost to some extent by aggressive behaviour, predation and diseases. To investigate the effects of caudal fin loss and regeneration on fast-start performance of crucian carp (Carassius auratus, inhabiting in still water) and pale chub (Zacco platypus, inhabiting in rip current), 16 juveniles of both crucian carp (body length, (6.27 ± 0.04) cm) and pale chub (body length, (6.14 ± 0.12) cm) were allocated to two groups, respectively. One group (8 fish for each treatment) for the treatment of caudal-fin-amputation-regeneration (20 days) and re-amputation, the other group (8 fish for each treatment) for control. The movement of each fish was recorded by a high-speed camera after an electric stimulation for the analysis of fast-start parameter. Furthermore, the morphological parameters such as body length (L), body height (H), fitness ratio (FR), caudal fin aspect ratio (AR), relative caudal fin area ratio and caudal fin index (FI) in the two cyprinid fish species were measured. The experimental water temperature was maintained at (25.0 ± 0.5)℃. The results showed that the crucian carp showed a significant lower FR and higher FI than pale chub (P < 0.01), but the maximum linear velocity (Vmax), escape distance (d), relative turning radius (TRr) and bending coefficient (BC) showed no significant difference between the two cyprinid fish species. The Vmax, d and TRr during fast-start process of both fish species decreased significantly after caudal fin loss (P < 0.01), with the Vmax of crucian carp decreased by 39% while that of pale chub decreased by 24% after caudal fin loss. After 20 days' recovery, the areas of caudal fin of both fish species recovered about 60% those of the caudal-fin-intact fish. However, the Vmax, d, RTr and BC of both caudal-fin-regenerated crucian carp and pale chub showed no significant difference compared with those of the control groups, respectively. Compared to the caudal-fin-intact fish, the decrease of Vmax of crucian carp and pale chub after the second amputation (17% and 9%) was smaller than the first amputation (39% and 24%). The decrease ratio between the first and the second caudal fin amputation in crucian carp was larger than that of pale chub. However, the bending coefficient (BC) of pale chub increased significantly after the second caudal fin amputation compared with those of fin-intact group (P = 0.046). The results indicated that (1) the caudal fin of crucian carp played a more important role than that of pale chub during fast-start movement; and (2) the pale chub which prefer to rip current habitat showed more significant functional compensation after 20 days' recovery. 参考文献 相似文献 引证文献

Morphological scaling of body form in four shark species differing in ecology and life history

Body form can change across ontogeny, and can influence how animals of different sizes move and feed. Scaling data on live apex predatory sharks are rare and, therefore, we examined patterns of scaling in ontogenetic series of four sympatric shark species exhibiting a range of sizes, ecologies and life histories (tiger, bull, blacktip, and nurse shark). We evaluated 13 linear morphological variables and two areas (caudal and dorsal) that could influence both animal condition and locomotor performance. These measurements included dimensions of the dorsal, pectoral, and caudal fins, as well as several dimensions of body circumference, and of the head. For all four species, the body axis (eye-to-eye, lateral span, frontal span, proximal span) scaled close to isometry (expected slope of 1.0). The two largest sharks (tiger and bull sharks) also showed significant negative allometry for elements of the caudal fin. We found significant negative allometry in the lengths of the upper lobe of the caudal fin (caudal fin 1) and the overall height of the caudal fin (caudal fin 2) in tiger and bull sharks, with slopes ranging from about 0.60 to 0.73. Further, tiger sharks showed negative allometry in caudal fin area. These results suggest that in terms of overall body dimensions, small sharks are roughly geometrically similar to large sharks, at least within the species we examined. However, juvenile tiger (and to a lesser extent bull sharks) are notable in having proportionately larger caudal fins compared to adult sharks. As the caudal fin contributes to generating thrust during forward locomotion, this scaling implies differences among adult and juvenile sharks in locomotor ability. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 114, 126–135.

Aggression‐induced fin damage modulates trade‐offs in burst and endurance swimming performance of mosquitofish

Locomotor performance is crucial to survival in many species. Swimming performance in fish depends on fin shape and size, and swimming performance may change with fin damage. The aim of this study was to investigate the relationship between fin size and swimming performance in male Eastern mosquitofish Gambusia holbrooki either with undamaged fins, or with fins that have sustained damage as a consequence of aggressive encounters. We show that in fish with undamaged fins burst swimming speeds increase with an increasing caudal fin size, while sustained swimming speeds (Ucrit) decrease with increasing fin size. In fish with damaged fins, Ucrit increases with an increasing caudal fin area, demonstrating a measurable cost of fin damage. The relationship between fin size and Ucrit is not linear but is best described by a Gaussian curve, where Ucrit decreases as fin size either increases or decreases from a central optimal value. We suggest that fish with large fins benefit because they can withstand more fin damage resulting from intraspecific aggression before experiencing detrimental effects such as reduced Ucrit.

Small-scale morphological and genetic differentiation in the Mediterranean killifish Aphanius fasciatus (Cyprinodontidae) from a coastal brackish-water pond and an adjacent pool in northern Sardinia

Two samples of Aphanius fasciatus collected in the Pilo pond (northern Sardinia, Italy) and in an adjacent pool of small surface area were analysed morphologically (235 individuals) and genetically (a subsample of 58 individuals). The aims of the present study were (i) to test the hypothesis that different predation pressures may be associated with morphological and/or genetic differences between samples from each habitat and (ii) to assess the level of divergence between the two populations. Morphological analysis was based on the relative size of fins because it has been shown to be associated with predation pressure. The relative caudal fin area (caudal fin area/total body surface) was smaller in specimens from the pool, in both males and females, whereas no differences were found for the dorsal and anal fin areas. Caudal fins with higher aspect ratio (fin depth/fin length) were found in fish from the pool but not in the pond, due to a higher fin depth. We hypothesised that specimens from the pool would show smaller caudal fin area, since they are subject to lower predation pressure. Random amplification of polymorphic DNA (RAPD) analysis revealed a relatively high degree of both within- and between-sample genetic heterogeneity. The pond and pool samples exhibited heterozygosities, which did not differ significantly by t-test. Between-sample genetic divergence was highlighted by the coancestry coefficient (θ = 0.301 ± 0.059, P < 0.001) and analysis of molecular variance (AMOVA) (variance between sites = 41%, P < 0.001). Genetic divergence between sites with a relatively high genetic diversity within both samples suggested that the population in the pool did not originate from a single colonisation event with a small number of founders. The genetic divergence between the two populations is consistent with their differences in fin size.

Locomotion in scombrid fishes: morphology and kinematics of the finlets of the chub mackerel Scomber japonicus.

Finlets are small non-retractable fins located on the dorsal and ventral margins of the body between the second dorsal and anal fins and the tail of scombrid fishes. The morphology of the finlets, and finlet kinematics during swimming in a flow tank at speeds of 0.8-3. 0 fork lengths s(-1), were examined in the chub mackerel Scomber japonicus. Functionally, S. japonicus has five dorsal and anal triangular finlets (the fifth finlet is a pair of finlets acting in concert). Slips of muscle that insert onto the base of each finlet indicate the potential for active movement. In animals of similar mass, finlet length and area increased posteriorly. Finlet length, height and area show positive allometry in animals from 45 to 279 g body mass. Summed finlet area was approximately 15 % of caudal fin area. During steady swimming, the finlets typically oscillated symmetrically in the horizontal and vertical planes. Finlet excursions in the x, y and z directions ranged from 1 to 5 mm, increased posteriorly and were independent of speed. The timing of the maximum amplitude of oscillation was phased posteriorly; the phase lag of the maximum amplitude of oscillation was independent of speed. During some periods of gliding, a finlet occasionally moved independently of the body and the other finlets, which indicated active control of finlet movement. The angle of attack of the finlets averaged approximately 0 degrees over a tailbeat, indicating no net contribution to thrust production via classical lift-based mechanisms. However, the timing of finlet movement relative to that of the tail suggests that more posterior finlets may direct some flow longitudinally as the tail decelerates and thereby contribute flow to the developing caudal fin vortex.

Wing design and scaling of flying fish with regard to flight performance

Fin and body dimensions of six genera of flying fish (Exocoetidae) were examined to study variation in morphological parameters in relation to aerodynamics performance. The fins are modified as wings for gliding flight. Fin area and fin span increase with increasing body mass, whereas the percentage of wing area contributed by the pectoral fins and the percentage of the caudal fin area contributed by the hypocaudal lobe remain constant. The aerodynamic design of flying fish approximates the monoplane‐biplane classification proposed by Breder (1930). Scaling relationships for wing loading and aspect ratio indicate that wing morphology in the Exocoetidae is more similar to birds and bats than to other gliders. The flight performance of flying fish is a high‐speed glide with a relatively flat trajectory. The wing, as indicated by the aspect ratio, is designed for high lift with low drag characteristics.

Effects of Partial Caudal-Fin Amputation on the Kinematics and Metabolic Rate of Underyearling Sockeye Salmon (Oncorhynchus Nerka) At Steady Swimming Speeds

ABSTRACT Propulsive wavelength, tail-beat frequency, trailing-edge amplitude, critical swimming speed and oxygen consumption rates have been measured for sockeye salmon in which the trailing edge depth and caudal-fin area were variously reduced by partial caudal-fin amputation. The swimming mode was sub-carangiform. The 45 min critical swimming speed for intact fish was 61·6 cm/sec (3·0 l/sec). The critical speed was not significantly reduced by removal of either the epaxial or hypaxial caudal-fin lobes, but was reduced significantly (P &amp;lt; 0·05) to 51·8 cm/sec (2·5 l/sec) when both lobes were removed. The mean length of the propulsive wave was 1·00 body length, and was not affected by the caudal-fin surgery. Both tail-beat frequency and amplitude increased with speed, their product linearly so. Normalization of data in relation to the physiological maximum at the critical swimming speed showed no relative changes in frequency and amplitude. No significant differences were observed in standard or active metabolic rates. General equations describing thrust (Lighthill, 1969) and drag were compared. It was shown that the drag on the caudal fin was markedly increased by lateral propulsive movements as suggested by Bone ‘s boundary-layer thinning hypothesis (Lighthill, 1971). Drag coefficients for the caudal fin were one to two orders of magnitude higher than would be expected in the absence of lateral movements. It is considered that the principal function of the caudal fin is in manoeuvre and acceleration.

Aquatic animal propulsion of high hydromechanical efficiency

Aquatic animal propulsion of high hydromechanical efficiency