Functional morphology of the pectoral fins in bamboo sharks, Chiloscyllium plagiosum: benthic vs. pelagic station-holding

Bamboo sharks (Chiloscyllium plagiosum) are primarily benthic and use their relatively flexible pectoral and pelvic fins to rest on and move about the substrate. We examined the morphology of the pectoral fins and investigated their locomotory function to determine if pectoral fin function during both benthic station-holding and pelagic swimming differs from fin function described previously in leopard sharks, Triakis semifasciata. We used three-dimensional kinematics and digital particle image velocimetry (DPIV) to quantify pectoral fin function in five white-spotted bamboo sharks, C. plagiosum, during four behaviors: holding station on the substrate, steady horizontal swimming, and rising and sinking during swimming. During benthic station-holding in current flow, bamboo sharks decrease body angle and adjust pectoral fin angle to shed a clockwise fluid vortex. This vortex generates negative lift more than eight times that produced during open water vertical maneuvering and also results in an upstream flow that pushes against the posterior surface of the pectoral fin to oppose drag. In contrast, there is no evidence of significant lift force in the wake of the pectoral fin during steady horizontal swimming. The pectoral fin is held concave downward and at a negative dihedral angle during steady horizontal swimming, promoting maneuverability rather than stability, although this negative dihedral angle is much less than that observed previously in sturgeon and leopard sharks. During sinking, the pectoral fins are held concave upward and shed a clockwise vortex with a negative lift force, while in rising the pectoral fin is held concave downward and sheds a counterclockwise vortex with a positive lift force. Bamboo sharks appear to sacrifice maneuverability for stability when locomoting in the water column and use their relatively flexible fins to generate strong negative lift forces when holding position on the substrate and to enhance stability when swimming in the water column.     

Function of dorsal fins in bamboo shark during steady swimming

To gain insight into the function of the dorsal fins in white-spotted bamboo sharks (Orectolobiformes: Hemiscyillidae) during steady swimming, data on three-dimensional kinematics and electromyographic recordings were collected. Bamboo sharks were induced to swim at 0.5 and 0.75 body lengths per second in a laminar flow tank. Displacement, lag and angles were analyzed from high-speed video images. Onset, offset, duration, duty cycle and asynchrony index were calculated from three muscle implants on each side of each dorsal fin. The dorsal fins were displaced more laterally than the undulating body. In addition, the dorsal tips had larger lateral displacement than the trailing edges. Increased speed was accompanied by an increase in tail beat frequency with constant tail beat amplitude. However, lateral displacement of the fins and duration of muscle bursts remained relatively constant with increased speed. The range of lateral motion was greater for the second dorsal fin (mean 33.3°) than for the first dorsal fin (mean 28.4°). Bending within the fin was greater for the second dorsal fin (mean 43.8°) than for the first dorsal fin (mean 30.8°). Muscle onset and offset among implants on the same side of each dorsal fin was similar. Three-dimensional conformation of the dorsal fins was caused by interactions between muscle activity, material properties, and incident flow. Alternating bilateral activity occurred in both dorsal fins, further supporting the active role of these hydrofoils in thrust production during steady swimming. The dorsal fins in bamboo sharks are capable of thrust production during steady swimming and do not appear to function as stabilizing structures.     

实验室条件下唐鱼两性异形及其与游泳能力关系

为了解唐鱼两性异形及其与游泳能力关系,检测了性成熟阶段唐鱼躯干部和鱼鳍形态特征以及爆发游泳速度(U_burst)和临界游泳速度(U_crit)在雌雄之间的差异,旨在从形态适应角度探究长期进化中雌雄唐鱼各自面对选择压力所产生的游泳能力差异及其机制,从而为野生唐鱼保护提供基础数据.结果表明: 雌性唐鱼的体长、头高、头宽、尾鳍面积以及吻端至枕骨后末端、腹鳍起点至背鳍末端等长度均与雄性无显著差异.而体高、体宽、腹鳍起点至背鳍起点等反映腹腔大小的形态参数以及吻端至背鳍起点、吻端至臀鳍起点、枕骨后末端至背鳍起点等反映躯干部大小的形态参数均显示为雌性显著大于雄性,但头长以及胸鳍面积、腹鳍面积、背鳍面积和臀鳍面积均显示为雄性显著大于雌性.对所有数据进行主成分分析,结果显示第1主成分贡献率为74.2%,负载量较大的是体长、头长、头高、体高、头宽、体宽以及各鳍之间距离等主要反映唐鱼躯干整体特征的参数;第2主成分贡献率为15.7%,负载量较大的是胸鳍面积、腹鳍面积、背鳍面积和臀鳍面积等主要反映鱼鳍特征的参数.唐鱼性别在第1主成分上无法区分,但在第2主成分却可以明显区分.根据体宽、胸鳍面积、腹鳍面积、背鳍面积和臀鳍面积等建立的性别判别方程对雌雄判断准确率达到91.8%～92.5%.唐鱼游泳能力测定结果显示,雌性U_burst与雄性无显著差异,但U_crit显著小于雄性.以上结果表明,雌雄唐鱼两性异形主要集中在与游泳能力相关的鱼鳍特征上.相比雄性,雌性唐鱼虽然胸鳍等鱼鳍面积较小导致其U_crit小于雄性,却具有更长的躯干部以保证其同样具有较高的爆发游泳能力,从而有利于在流速波动很大的溪流中躲避捕食和进行其他应急活动;相比雌性,雄性唐鱼则具有较大的鱼鳍面积保证其U_crit高于雌性,以利于日常活动及在繁殖过程中追逐雌性等相对持久性游泳运动.     

Anatomy and muscle activity of the dorsal fins in bamboo sharks and spiny dogfish during turning maneuvers

Stability and procured instability characterize two opposing types of swimming, steady and maneuvering, respectively. Fins can be used to manipulate flow to adjust stability during swimming maneuvers either actively using muscle control or passively by structural control. The function of the dorsal fins during turning maneuvering in two shark species with different swimming modes is investigated here using musculoskeletal anatomy and muscle function. White‐spotted bamboo sharks are a benthic species that inhabits complex reef habitats and thus have high requirements for maneuverability. Spiny dogfish occupy a variety of coastal and continental shelf habitats and spend relatively more time cruising in open water. These species differ in dorsal fin morphology and fin position along the body. Bamboo sharks have a larger second dorsal fin area and proportionally more muscle insertion into both dorsal fins. The basal and radial pterygiophores are plate‐like structures in spiny dogfish and are nearly indistinguishable from one another. In contrast, bamboo sharks lack basal pterygiophores, while the radial pterygiophores form two rows of elongated rectangular elements that articulate with one another. The dorsal fin muscles are composed of a large muscle mass that extends over the ceratotrichia overlying the radials in spiny dogfish. However, in bamboo sharks, the muscle mass is divided into multiple distinct muscles that insert onto the ceratotrichia. During turning maneuvers, the dorsal fin muscles are active in both species with no differences in onset between fin sides. Spiny dogfish have longer burst durations on the outer fin side, which is consistent with opposing resistance to the medium. In bamboo sharks, bilateral activation of the dorsal in muscles could also be stiffening the fin throughout the turn. Thus, dogfish sharks passively stiffen the dorsal fin structurally and functionally, while bamboo sharks have more flexible dorsal fins, which result from a steady swimming trade off. J. Morphol. 274:1288–1298, 2013. © 2013 Wiley Periodicals, Inc.     

鲈鲤仔鱼的异速生长模式

采用实验生态学方法研究了鲈鲤(Percocypris pingi pingi)仔鱼(0～57日龄)的异速生长模式.结果显示:鲈鲤仔鱼全长由慢速生长到快速生长的转折点为25日龄;其多数外部器官均具有异速生长特点,头部和尾部的生长快于躯干部,均在22 ～ 27日龄出现生长拐点;眼径在14 ～ 15日龄较早出现生长拐点,促使眼睛充分发育,以提高早期仔鱼开口期摄食外源食物的能力;吻长在33～34日龄出现生长拐点,促进了口的充分发育,以适应不同的饵料环境;胸鳍、背鳍、尾鳍、臀鳍和腹鳍分别在13～14日龄、31～32日龄、32 ～33日龄、38 ～39日龄、43 ～ 44日龄出现生长拐点,除胸鳍和尾鳍外,其余各鳍的鳍条均在拐点处分化完全,即鲈鲤仔鱼的游泳能力已得到大幅提高.研究表明,鲈鲤仔鱼的异速生长模式,保证了各重要功能器官的充分发育,以适应多变的环境,有效地保障了其早期的生存,可为育苗生产和野生早期资源的保护提供技术支撑.     

Wake dynamics and locomotor function in fishes: interpreting evolutionary patterns in pectoral fin design

The great anatomical diversification of paired fins within theActinopterygii (ray-finned fishes) can be understood as a suiteof evolutionary transformations in design. At a broad taxonomicscale, two clear trends exist in the morphology of the anteriorlysituated pectoral fins. In comparing basal to more derived clades,there are general patterns of (i) reorientation of the pectoralfin base from a nearly horizontal to more vertical inclination,and (ii) migration of the pectoral fin from a ventral to mid-dorsalbody position. As yet, the functional significance of thesehistorical trends in pectoral fin design remains largely untestedby experiment. In this paper we test the proposal that variationin pectoral fin structure has an important influence on themagnitude and orientation of fluid forces generated during maneuveringlocomotion. Using digital particle image velocimetry for quantitativewake visualization, we measure swimming forces in ray-finnedfishes exhibiting the plesiomorphic and apomorphic pectoralfin anatomy. Our experiments focus on rainbow trout (Oncorhynchusmykiss), a lower teleost with pectoral fins positioned ventrallyand with nearly horizontally inclined fin bases, and bluegillsunfish (Lepomis macrochirus), a relatively derived perciformfish with more vertically oriented pectoral fins positionedmid-dorsally on the body. In support of hypotheses arising fromour prior wake studies and previously untested models in theliterature, we find that the pectoral fins of sunfish generatesignificantly higher forces for turning and direct braking forcescloser to the center of mass of the body than the pectoral finsof trout. These results provide insight into the hydrodynamicimportance of major evolutionary transformations in pectoralfin morphology within the Actinopterygii.     

Ontogeny of head and caudal fin shape of an apex marine predator: The tiger shark (Galeocerdo cuvier)

How morphology changes with size can have profound effects on the life history and ecology of an animal. For apex predators that can impact higher level ecosystem processes, such changes may have consequences for other species. Tiger sharks (Galeocerdo cuvier) are an apex predator in tropical seas, and, as adults, are highly migratory. However, little is known about ontogenetic changes in their body form, especially in relation to two aspects of shape that influence locomotion (caudal fin) and feeding (head shape). We captured digital images of the heads and caudal fins of live tiger sharks from Southern Florida and the Bahamas ranging in body size (hence age), and quantified shape of each using elliptical Fourier analysis. This revealed changes in the shape of the head and caudal fin of tiger sharks across ontogeny. Smaller juvenile tiger sharks show an asymmetrical tail with the dorsal (upper) lobe being substantially larger than the ventral (lower) lobe, and transition to more symmetrical tail in larger adults, although the upper lobe remains relatively larger in adults. The heads of juvenile tiger sharks are more conical, which transition to relatively broader heads over ontogeny. We interpret these changes as a result of two ecological transitions. First, adult tiger sharks can undertake extensive migrations and a more symmetrical tail could be more efficient for swimming longer distances, although we did not test this possibility. Second, adult tiger sharks expand their diet to consume larger and more diverse prey with age (turtles, mammals, and elasmobranchs), which requires substantially greater bite area and force to process. In contrast, juvenile tiger sharks consume smaller prey, such as fishes, crustaceans, and invertebrates. Our data reveal significant morphological shifts in an apex predator, which could have effects for other species that tiger sharks consume and interact with. J. Morphol. 277:556–564, 2016. © 2016 Wiley Periodicals, Inc.     

Functional Morphology of Aquatic Flight in Fishes: Kinematics, Electromyography, and Mechanical Modeling of Labriform Locomotion

Labriform locomotion is the primary swimming mode for many fishesthat use the pectoral fins to generate thrust across a broadrange of speeds. A review of the literature on hydrodynamics,kinematics, and morphology of pectoral fin mechanisms in fishesreveals that we lack several kinds of morphological and kinematicdata that are critical for understanding thrust generation inthis mode, particularly at higher velocities. Several needsinclude detailed three-dimensional kinematic data on speciesthat are pectoral fin swimmers across a broad range of speeds,data on the motor patterns of pectoral fin muscles, and thedevelopment of a mechanical model of pectoral fin functionalmorphology. New data are presented here on pectoral fin locomotionin Gomphosus varius, a labrid fish that uses the pectoral finsat speeds of 1 –6 total body lengths per second. Three-dimensionalkinematic data for the pectoral fins of G. varius show thata typical "drag-based" mechanism is not used in this species.Instead, the thrust mechanics of this fish are dominated bylift forces and acceleration reaction forces. The fin is twistedlike a propeller during the fin stroke, so that angles of attackare variable along the fin length. Electromyographic data onsix fin muscles indicate the sequence of muscle activity thatproduces antagonistic fin abduction and adduction and controlsthe leading edge of the fin. EMG activity in abductors and adductorsis synchronous with the start of abduction and adduction, respectively,so that muscle mechanics actuate the fin with positive work.A mechanical model of the pectoral fin is proposed in whichfin morphometrics and computer simulations allow predictionsof fin kinematics in three dimensions. The transmission of forceand motion to the leading edge of the fin depends on the mechanicaladvantage of fin ray levers. An integrative program of researchis suggested that will synthesize data on morphology, physiology,kinematics, and hydrodynamics to understand the mechanics ofpectoral fin swimming.     

中国NFDA2亚科金线NFDA2属鱼类一新种及其生态和适应(鲤形目：鲤科)

1999年11月在广西都安县下坳乡一岩洞地下水中采到1尾鱼类标本,经鉴定为金线NFDA2属一新种。新种与大鳞金线NFDA2S. macrolepis和陆良金线NFDA2S. macroscalus相近。但新种在背腹鳍相对位置以及背鳍末根不分枝鳍条后缘具锯齿等方面与上述两种存在明显差异;特别是该新种仅局限分布于洞穴中,就其生境来说也与上述两种更为不同。此外,新种头长与吻长和头长与眼径的比例是目前该属内已知最小的,眼明显偏大,反映出其对弱光生境条件的适应。     

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.     

How puffers (Teleostei: Tetraodontidae) swim

Two species of marine Indo-Pacific puffers, Arothron meleagris and A. nigropunctatus , were filmed with a high-speed motion picture camera while swimming in a Brett-type water tunnel at speeds of 1-3.5 body lengths (BL) s⁻¹. The puffers generated thrust by use of their pectoral fins in addition to their dorsal and anal fins; the long axis of the body tilted, mouth upwards, by 3–10) while the fishes swam; antero-ventral body profiles of the fishes changed as swimming speeds increased; pectoral fins undulated and moved 180) out of phase from each other, while dorsal and anal fins oscillated in phase with each other; frequencies of fin movements ( F ) increased linearly in relation to swimming speeds ( Uc(rel) ) and were described by the equation F =1.48 Uc(rel) +1.66; stride lengths also increased at higher Uc(rel) ; and, at swimming speeds above 3.0 BL s⁻¹ puffers began to move their tails in sub carangiform-like modes of burst swimming. These results modify significantly the accepted view of the tetraodonti form mode of median and paired fin swimming.     

Solitary chemoreceptor cells of Ciliata mustela (Gadidae, Teleostei) are tuned to mucoid stimuli

Summed potentials were recorded from the dorsal recurrent facialnerve innervating the solitary chemoreceptor cells on the anteriordorsal fin (ADF), from the ventral recurrent facial nerve innervatingboth taste buds and solitary chemoreceptor cells on the pectoral(PEC) and pelvic (PEL) fins, and from the anterior dorsal finmuscles in the rockling, Ciliata mustela. There is little overlapbetween the sumulus spectra of solitary chemoreceptor cellsand taste buds. The ADF solitary cells are particularly sensitiveto body mucus (skin water) of non-congeners like Gadus, Solea,Cottus, Mugil, Zoarces, Gaidropsarus, and Encheliopus, but insensitiveto amino acids and a variety of body fluids of fish, invertebrates,and extracts of potential stimuli like algae and sand. Pectoraland pelvic fins are particularly sensitive to amino acids, bodyfluids of fish and invertebrates, but less sensitive to skinmucus of fish, probably due to the abundance of taste buds.Active sampling by undulation of the anterior dorsal fin isessential for proper functioning; it induces disadaptation ofthe receptor elements. Solitary chemoreceptor cells provide,apparently, cues to discriminate between conspecifics and non-conspecifics.It is unlikely that they are involved in pheromone detection.     

A new approach to quantifying morphological variation in bluegill Lepomis macrochirus

Bluegill Lepomis macrochirus showed intraspecific morphological and behavioural differences dependent on the environment. Pelagic L. macrochirus had more fusiform bodies, a higher pectoral fin aspect ratio, a larger spiny dorsal fin area and pectoral fins located farther from the centre of mass than littoral L. macrochirus (P < 0·05). The shape of the body and pectoral fins, in particular, were suggestive of adaptation for sustained high-speed and economical labriform swimming. Littoral L. macrochirus had a deeper and wider body, deeper caudal fins and wider mouths than pelagic L. macrochirus (P < 0·05). Additionally, the soft dorsal, pelvic, anal and caudal fins of littoral L. macrochirus were positioned farther from the centre of mass (P < 0·05). The size and placement of these fins suggested that they will be effective in creating turning moments to facilitate manoeuvring in the macrophyte-dense littoral habitat.     

Morphological and histochemical characterization of the pectoral fin muscle of batoids

Batoids differ from other elasmobranch fishes in that they possess dorsoventrally flattened bodies with enlarged muscled pectoral fins. Most batoids also swim using either of two modes of locomotion: undulation or oscillation of the pectoral fins. In other elasmobranchs (e.g., sharks), the main locomotory muscle is located in the axial myotome; in contrast, the main locomotory muscle in batoids is found in the enlarged pectoral fins. The pectoral fin muscles of sharks have a simple structure, confined to the base of the fin; however, little to no data are available on the more complex musculature within the pectoral fins of batoids. Understanding the types of fibers and their arrangement within the pectoral fins may elucidate how batoid fishes are able to utilize such unique swimming modes. In the present study, histochemical methods including succinate dehydrogenase (SDH) and immunofluoresence were used to determine the different fiber types comprising these muscles in three batoid species: Atlantic stingray (Dasyatis sabina), ocellate river stingray (Potamotrygon motoro) and cownose ray (Rhinoptera bonasus). All three species had muscles comprised of two muscle fiber types (slow-red and fast-white). The undulatory species, D. sabina and P. motoro, had a larger proportion of fast-white muscle fibers compared to the oscillatory species, R. bonasus. The muscle fiber sizes were similar between each species, though generally smaller compared to the axial musculature in other elasmobranch fishes. These results suggest that batoid locomotion can be distinguished using muscle fiber type proportions. Undulatory species are more benthic with fast-white fibers allowing them to contract their muscles quickly, as a possible means of escape from potential predators. Oscillatory species are pelagic and are known to migrate long distances with muscles using slow-red fibers to aid in sustained swimming.     

The evolution of underwater flight: The redistribution of pectoral fin rays,in manta rays and their relatives (Myliobatidae)

Batoids are a diverse clade of flat cartilaginous fishes that occur primarily in benthic marine habitats. The skates and rays typically use their flexible pectoral fins for feeding and propulsion via undulatory swimming. However, two groups of rays have adopted a pelagic or bentho‐pelagic lifestyle and utilize oscillatory swimming—the Myliobatidae and Gymnuridae. The myliobatids have evolved cephalic lobes, anteriorly extended appendages that are optimized for feeding, while their pectoral fins exhibit several modifications that likely arose in association with functional optimization of pelagic cruising via oscillatory flight. Here, we examine variation in fin ray distribution and ontogenetic timing of fin ray development in batoid pectoral fins in an evolutionary context using the following methods: radiography, computed tomography, dissections, and cleared and stained specimens. We propose an index for characterizing variation in the distribution of pectoral fin rays. While undulatory swimmers exhibit symmetry or slight anterior bias, we found a posterior shift in the distribution of fin rays that arose in two distinct lineages in association with oscillatory swimming. Undulatory and oscillatory swimmers occupy nonoverlapping morphospace with respect to fin ray distribution illustrating significant remodeling of pectoral fins in oscillatory swimmers. Further, we describe a derived skeletal feature in anterior pectoral fins of the Myliobatidae that is likely associated with optimization of oscillatory swimming. By examining the distribution of fin rays with clearly defined articulation points, we were able to infer evolutionary trends and body plan remodeling associated with invasion of the pelagic environment. Finally, we found that the number and distribution of fin rays is set early in development in the little skate, round stingray, and cownose ray, suggesting that fin ray counts from specimens after birth or hatching are representative of adults and therefore comparable among species.     

Normal growth of the "see-through" medaka

The see-through stock in the medaka Oryzias latipes, causes pigments to be absent from the whole body and has a transparent body in the adult stage as well as during embryonic stages. To establish a standard table of growth stages for this model fish, morphological features were examined during the growing period from hatching to adulthood. The main observations were performed on morphological changes in external and internal organs that could be seen through the body wall of the living fish during growth. Finally, five growth stages from just after hatching to the adult stage were defined on the basis of synchronized or definite changes in morphology as follows: (1) stage 40 in which the nodes (joints) in bony rays of the caudal and pectoral fins first appear, (2) the stage 41 in which the ribs and the anal, dorsal and ventral fins are formed by degeneration of the membrane fin folds, as recognized by the first appearance of nodes in the fin rays of the anal, pectoral and dorsal fins, and the parallel distribution of the dorsal artery and ventral vein of the tail, (3) stage 42 in which the 2-spiral pattern of the gut, the ray nodes in the ventral fins, and the scales first appear, (4) stage 43 in which early secondary sexual characters such as urinogenital protruberances (female) and papillar processes (male) appear, (5) stage 44 in which the 3-spiral pattern of the gut and the papillar process on the 2nd ray of pectral fins (male) appear.     

颈斑尖猪鱼——中国南海隆头鱼科新纪录种

本文根据采自海南岛的标本描述了中国南海一新记录种:颈斑尖猪鱼(Leptojulis lambdastigma)。本种的主要形态特征为:体长形,体长为体高的3.7~4.0倍,为头长的3.1~3.6倍;头长为吻长的2.7~3.3倍,为胸鳍长的1.45~1.65倍;头裸露无鳞;两颌前端各具2对大犬齿,外侧1对犬齿弯向外后方;背鳍Ⅸ-12,臀鳍Ⅲ-12,胸鳍i(不分支)+11-12(分支);侧线完整,侧线鳞27;颈部具一个"V"形大黑斑,胸鳍后部的上方、侧线的下方具一小黑斑。新鲜标本头部具2条黄色纵带,沿体侧分别经眼和胸鳍基部向后达尾鳍基部;体侧背部具1条浅棕黄色条带;胸鳍基部棕红色,后部浅色;臀鳍浅蓝色;尾鳍下部淡蓝色,上部橙色。本种与尾斑尖猪鱼(L.urostigma)形态较为相似,主要差别在于颈斑尖猪鱼的颈部具有一显著的"V"形黑斑,尾鳍基部无黑斑(尾斑尖猪鱼具此黑斑)。     

How small puffers (Teleostei: Tetraodontidae) swim

 The tetraodontiform swimming mode has recently attracted attention because puffers swim very steadily and, unlike most of the other median and paired fin (MPF) swimmers, use more than one pair of fins to propel themselves through the water. To date, only one study presenting data concerning the swimming kinematics of puffers has been published, and this study dealt only with two species of large body size. In the present study, the swimming kinematics of small puffers (<6 cm TL) Tetraodon schoutedeni is described and compared to the swimming kinematics of larger puffers and boxfish. The results show that, generally, the swimming kinematics of small puffers is similar to that of larger puffers. The main differences that were found are in the synchronization of dorsal and anal fin motion, and in the motion of the pectoral fins, which complete their adduction before the dorsal and anal fins do. Maximum fin beat frequency was 18.4 Hz, much faster than that of larger puffers. At slow and median swimming speeds, dorsal fin beat amplitude increases with swimming speed and then remains constant between median and fast swimming speeds. The results confirm previous findings that puffers swim extremely steadily. Most of the differences in swimming kinematics between large and small puffers can be attributed to the size differences, but the difference in fin synchronization should be further studied to be completely understood. Received: September 27, 2002 / Revised: January 7, 2003 / Accepted: February 6, 2003     

红鳍笛鲷仔、稚鱼异速生长

运用生态学和传统理论生物学的研究方法,对孵化后红鳍笛鲷（Lutjanus erythropterus）仔、稚鱼在早期生存和环境适应上的异速生长及器官优先发育生态学意义进行了研究,以期为红鳍笛鲷人工繁殖、育苗提供参考资料。以17日龄为红鳍笛鲷仔、稚鱼的区分时期,结果表明,红鳍笛鲷仔、稚鱼的感觉、呼吸摄食和游泳等器官快速分化,均存在异速生长现象。在头部器官中,吻长、口宽、眼径和头高在仔鱼期均为正异速生长,稚鱼期吻长为等速生长,口宽、眼径和头高为负异速生长。在身体各部位中,仔鱼期头长和体高为正异速生长,躯干部和尾长为负异速生长;稚鱼期体高和躯干长为正异速生长,头长和尾长为等速生长;在游泳器官中,仔鱼期红鳍笛鲷背鳍、腹鳍、尾鳍为正异速生长,胸鳍为等速生长,稚鱼期臀鳍为正异速生长,腹鳍、胸鳍和尾鳍为等速生长,背鳍为负异速生长。红鳍笛鲷这些关键器官的快速发育,使外源性营养开始后以最小的代谢损耗获得了生存能力的显著提升,对挑战和适应纷繁变换的外界压力具有重要的生态学意义。     

Larval development of Argentine hake Merluccius hubbsi

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.