广西鱼类一新纪录:唐鱼(鲤形目:鲤科)

于2008年在广西一山涧小溪发现了国家Ⅱ级保护野生动物唐鱼(Tanichthys albonubes)种群,属、种均为广西新纪录.与广东从化野生唐鱼比较,广西唐鱼背鳍、腹鳍和臀鳍有明显黑色斑纹,尾柄较高,广西唐鱼种群在可量性状主成分分析上与广东从化唐鱼野生种群可以明显区分开来.我们还对唐鱼栖息地生境与环境进行了调查,栖...     

切鳍标记对唐鱼游泳能力的影响

本研究通过测定完全切除背鳍、臀鳍、尾鳍或双侧胸鳍后唐鱼（Tanichthys albonubes）临界游泳速度来评价切鳍标记对游泳能力的影响。研究结果表明,在速度增量（ΔU）为36 mm/s,持续时间（Δt）分别为5 min、10 min、15 min、20 min、25 min、30 min的条件下,唐鱼临界游泳速度会随着持续时间的延长而降低。鳍组织完整的唐鱼〔体长（24 ± 1）mm〕,在不同持续时间（Δt）条件下,其绝对临界游泳速度（Uacrit）为（251.98 ± 11.04）mm/s ~（333.78±12.44）mm/s;同等条件下,切除唐鱼的背鳍或臀鳍均不会对唐鱼的绝对临界游泳速度造成显著影响（P＞0.05）,但切除唐鱼的尾鳍或胸鳍后其临界游泳速度与对照组相比极显著降低（P＜0.01）,其中切除尾鳍后绝对临界游泳速度平均下降47.20%,切除胸鳍后平均下降22.98%,两者间存在极显著的差异（P＜0.01）(图2)。研究表明背鳍切除可作为野外唐鱼短期标记-重捕的手段之一。     

鲶鱼和胡子鲶的两性异形与雌性个体生育力

检测了鲶鱼(Silurus asotus)和胡子鲶(Clarias fuscus)繁殖期18个形态特征的两性异形以及雌性个体生育力。结果表明,鲶鱼和胡子鲶雌雄性别比例均符合1∶1。One-way ANOVA显示,鲶鱼雌雄个体体长差异不显著,胡子鲶雌性个体体长显著小于雄性个体(P0.05)。以体长为协变量的One-way ANCOVA显示,特定体长的鲶鱼雌性个体的眼间距和体高显著大于雄性个体(P0.05),两性间其它局部特征不存在显著的两性差异;特定体长的胡子鲶雌性个体的体高、腹鳍基前距和腹鳍臀鳍间距显著大于雄性个体,雌性个体的臀鳍基长、尾柄高和尾鳍长显著小于雄性个体(P0.05),两性间其它局部特征不存在显著的两性差异。Two-way ANOVA显示,胡子鲶体长显著大于鲶鱼(P0.05),性别及物种与性别两因素的相互作用对体长影响不显著。以体长为协变量的Two-way ANCOVA显示,胡子鲶的头长、头宽、吻长、眼间距、尾柄高、尾鳍长、背鳍基前距、背鳍基长、腹鳍基前距、腹鳍臀鳍间距、体重和去内脏体重显著大于鲶鱼,头高、体高、臀鳍基长显著小于鲶鱼(P0.05),物种间的其他形态特征变量差异不显著;雌性个体的体高、背鳍基前距、腹鳍基前距、腹鳍臀鳍间距显著大于雄性个体,臀鳍基长、尾柄高、尾鳍长、背鳍基长显著小于雄性个体(P0.05),两性间的其他形态特征变量差异不显著;物种与性别两因素的相互作用对体高、臀鳍基长、尾柄高、尾鳍长、背鳍基长和腹鳍臀鳍间距影响显著,对其余的形态特征变量影响不显著。15个形态特征变量的主成分分析(Eigenvalue≥1)发现,前2个主成分共解释68.4%的变异。头宽、眼间距、尾柄高、尾鳍长、背鳍基前距、背鳍基长、腹鳍基前距和腹鳍臀鳍间距在第一主成分有较高的正负载系数,臀鳍基长在第一主成分有较高的负负载系数(解释51.2%变异);眼后头长在第二主成分有较高的负负载系数(解释17.2%变异)。胡子鲶在第一主成分和第二主成分的分值均显著大于鲶鱼,雌雄两性的差异以及两因素的相互作用对分值的影响均不显著。实验检测的鲶鱼、胡子鲶的怀卵数量与体长和体重回归关系显著。One-way ANCOVA及矫正平均值Tukey's检验显示,特定体长的胡子鲶的产卵数量显著大于鲶鱼。性选择是胡子鲶大个体雄性形成的主要原因,同时影响与运动相关的尾部特征。生育力选择更多的影响与雌性胡子鲶较大腹腔容积相关的形态特征变异。环境因子、食物可得性和营养状况同时影响了个体大小两性异形的形成。     

中国广西盲鳅一新种——环江高原鳅(英文)

2007年4月,在广西壮族自治区环江县川山镇乐衣村附近一洞穴采集到一批盲鳅类标本。经鉴定,为高原鳅属(Triplophysa)鱼类一新种,被命名为环江高原鳅(Triplophysa huangjiangensis)。该新种以以下组合特征与高原鳅属的其他已知种类相区别:无眼;通体无鳞;尾鳍分叉;尾柄上、下叶具发达的软鳍褶;背鳍后缘平截;背鳍起点距尾鳍基的距离短于距吻端的距离;背鳍分枝鳍条数为8~9;胸鳍分枝鳍条数为10~11;腹鳍分枝鳍条数为6~7;臀鳍分枝鳍条数为6;尾鳍分枝数为13~14;胸鳍长为胸鳍起点至腹鳍起点间距的52.3%~70.7%;腹鳍起点位于背鳍起点之前下方;外侧吻须最长,为侧面头长的47.0%~73.8%;前鼻孔位于一短管中,末端延长呈须状;鳔后室发达,末端可伸达腹鳍起点。     

不同水系松潘裸鲤的形态特征分析

为了解岷江、大渡河、雅砻江和金沙江水系松潘裸鲤Gymnocypris potanini的形态差异,采用常规形态学和多变量形态度量学方法比较分析了采自这4个水系206尾样本的形态特征。结果显示,各水系间松潘裸鲤的第一鳃弓外侧鳃耙数和背鳍、胸鳍、腹鳍及臀鳍鳍条数之间的差异无统计学意义;主成分分析显示,头部(吻端至胸鳍起点/体长、吻端至头背部末端/体长、头长/体长)和尾部特征值(尾鳍背部起点至臀鳍起点/体长、臀鳍起点至尾鳍腹部起点/体长)对形态影响最大;判别分析发现,岷江和雅砻江安宁河种群与其他种群明显分开;聚类分析显示,岷江水系种群聚为一支,金沙江、大渡河、雅砻江水系种群聚为另一支,金沙江水系种群聚在一起,大渡河和雅砻江水系种群未按水系聚在一起,而其聚类关系与种群间的地理距离基本一致;形态差异系数分析显示,可根据臀鳞行列长进行亚种的区分。大渡河和雅砻江水系的松潘裸鲤为硬刺松潘裸鲤亚种。     

广西高原鳅属鱼类一穴居新种记述

2003年1月,在广西壮族自治区天峨县红水河水系地下河采集到一批盲鱼标本。经鉴定,为高原鳅属Triplophysa一未经发表的新种。新种天峨高原鳅Triplophysa tianeensis sp．nov．与个旧盲高原鳅T．gejiuensis、石林盲高原鳅T．shilinensis、阿庐高原鳅T．aluensis和南丹高原鳅T．nandanensis相似;本新种腹鳍末端不达肛门,尾鳍分枝鳍条16,可进一步与个旧盲高原鳅和石林盲高原鳅(腹鳍末端达到肛门,尾鳍分枝鳍条14-15)相区别;本新种背鳍起点位于体之中点、腹鳍起点之后,肛门紧靠臀鳍起点,可进一步与阿庐高原鳅(背鳍起点靠近吻端、位于腹鳍起点之前,肛门距臀鳍起点仍有一段距离)相区别。本新种与同分布于红水河水系的南丹高原鳅Triplophysa nandanensis Lan et al.较为相似;但二者区别明显：新种背鳍分枝鳍条7、胸鳍分枝鳍条9、腹鳍分枝鳍条6、背鳍外缘平截、背鳍起点位于腹鳍起点之后,后者背鳍分枝鳍条8、胸鳍分枝鳍条10～11、腹鳍分枝鳍条7、背鳍外缘凹入、背鳍起点位于腹鳍起点之前;此外,新种的穴居特征更为显著：眼极度退化、头长为眼径16．8—32．8(25．0)倍、部分个体无色素斑且各鳍无斑点,而南丹高原鳅眼小、头长为眼径4．7～9．0(7．5)倍、体和头背侧密布云状斑且各鳍均具点状斑。     

黄颡鱼的两性异形和雌性繁殖特征

测定了黄颡鱼成体的体长、头长、头宽、头高、吻长、眼径、眼间距、眼后头长、体高、尾柄高、背鳍基前距、背鳍基长、尾柄长、腹鳍基前距、背鳍脂鳍间距、腹鳍臀鳍间距、尾鳍长、体重、去内脏体重等形态指标以及雌体的怀卵数量。雌性成体的体长显著小于雄性成体。其它局部特征皆与体长呈正相关,回归剩余值的t—检验表明,雌性成体的眼径、头高、体高、腹鳍基前距、体重显著大于雄性成体,其它局部形态特征不存在显著的两性差异。黄颡鱼雌体通过个体大小的增加和腹部形态的改变增加腹腔容量,增加繁殖输出。     

丝背细鳞鲀外部形态特征

以黄海捕捞的丝背细鳞鲀(Stephanolepis cirrhifer)为实验样本,共100尾,体全长7.00~14.50 cm,体重7.96~136.54 g。对其外部形态进行观察绘图描述,分析其鱼体侧面和头部、第二背鳍鳍条和鳞片的形态特征。对可量性状与可数性状进行测量和线性回归分析。对背鳍鳍条、尾鳍鳍条、臀鳍鳍条和胸鳍鳍条数量进行统计。观察发现,(1)体表被形态多样的绒状鳞片,鳞片为形似盾鳞的骨鳞,由基板和骨质凸起组成;腹鳍棘与腹部之间具有一可收缩的皮质三角形结构,体表布满黑色条纹与黑色斑点,以眼部为中心向外延伸出6条主侧线(背侧线、框上线、框下线、前鳃盖线、下颌线、上颞线)为其外部形态的明显特征。(2)线性相关性最好的是全长(TL)/体长(SL),其比值变动范围最小,雌雄差异小,相关方程为:SL=0.8239TL﹣0.0471(R2=0.9763);线性相关性最差的是头长/吻长,其比值不仅变动最大,而且雌雄的差异最大。(3)体长(SL)与体重(W)的关系为:W=2.3743e0.2803SL(R2=0.96);雄性:W=2.5406e0.2737SL(R2=0.96),雌性:W=2.0328e0.2954SL(R2=0.95)。(4)鱼鳍鳍条数量:第一背鳍为两根背鳍棘,第二背鳍30~34;臀鳍29~34;胸鳍12;尾鳍13;腹鳍为一个腹鳍棘。雌雄第二背鳍的第二根鳍条长度存在差异,雄性长度比雌性长约1/6~1/5。丝背细鳞鲀在黄海的出现,说明该鱼种洄游分布范围已经扩大到黄海。     

嘉陵江下游蛇鮈的两性异形与雌性个体生殖力

为了解蛇鮈雌雄间是否存在显著的外部形态差异及雌性个体生殖力情况, 在繁殖期对嘉陵江下游(合川江段)共76尾蛇鮈样本的两性异形、性比及雌性个体生殖力进行分析.结果表明: 嘉陵江下游蛇鮈繁殖群体的性比接近1∶1,且蛇鮈两性的体型大小相同,但局部特征(如头部和躯干部等)呈现出显著的两性异形,如成体雄性蛇鮈的头部、胸鳍和腹鳍均较雌性蛇鮈大,而躯干部的体宽、体高和躯干长则是雌性蛇鮈大于雄性蛇鮈,这可能是性选择长期作用的结果.主成分分析显示,前3个主成分的累积贡献率达75.2%,但雌雄个体间形态特征相互重叠,无法将两者截然分开;利用判别函数对蛇鮈性别进行回判,综合判别准确率为92.1%.蛇鮈雌性个体绝对生殖力在979～19979粒;且与体长和去内脏体质量均呈显著正相关.同历史资料相比,本研究中嘉陵江蛇鮈的生殖力增大显著,这可能是蛇鮈对种群资源量下降和水环境变化主动适应的结果.     

西藏黑斑原繁殖群体两性异形研究

两性异形是指在同一种群内, 雌雄间的形态特征产生分化, 如在个体大小、局部形态构造、体色等方面呈现出差异的现象。为了解西藏黑斑原 (Glyptosternum maculatum) 雌雄间是否也存在两性异形, 在其繁殖期对性成熟个体进行了形态学测量及相关分析。结果表明: 西藏黑斑原繁殖群体间存在显著的雌雄异形, 一是雄性个体的体长、体重及特定体长下的尾长显著大于雌性个体; 二是在特定体长下, 雌性个体眼径、体高、躯干长以及背鳍、胸鳍、腹鳍、臀鳍、尾鳍长度均显著大于雄性。16个形态参数的主成分分析表明, 雌雄间的差异主要是由体型特征(包括身体各部分长度、各鳍长度等)及头部形态特征引起的, 贡献率达76.7%。对全长-体重方程中异速生长指数b的t检验表明, 繁殖期黑斑原雌性个体呈等速生长而雄性个体呈异速生长。     

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.     

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.     

Development of the pectoral, pelvic, dorsal and anal fins in cultured sea bream

The pectoral fin girdle was the first element of the fins to develop in Sparus aurata. By 3·1mm L _N (notochord length) the cleithrum was ossified and the cartilaginous caracoid-scapula was present. The fin was fully developed at 11·6 mm L _S (standard length) and by 16·0 mm L _S most elements of the fin were ossified. The pelvic fins were the last pair to develop and rudiments of these were first detected at 7·9 mm L _S. The pelvic fin and girdle were completely formed and ossified at 16·0 mm L _S. The development of dorsal and anal fins began at c. 6·5–7·0 mm L _S with the formation of 10 cartilaginous dorsal proximal radials and eight cartilaginous ventral proximal radials. The three cartilaginous predorsals (supraneurals) appeared at 7·7 mm L _S and the ossification of dorsal and anal proximal and distal radials began, respectively, at 10·5 mm L _S and 11·3 mm L _S. Ossified structures in the fins were also classified according to their origin, as being either dermal or endochondral. Finally the chronology of appearance of fin structures in S. aurata was compared with that reported for other Sparidae, Engraulidae and Haemulidae.     

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.     

Ecomorphology of Locomotion in Labrid Fishes

The Labridae is an ecologically diverse group of mostly reef associated marine fishes that swim primarily by oscillating their pectoral fins. To generate locomotor thrust, labrids employ the paired pectoral fins in motions that range from a fore-aft rowing stroke to a dorso-ventral flapping stroke. Species that emphasize one or the other behavior are expected to benefit from alternative fin shapes that maximize performance of their primary swimming behavior. We document the diversity of pectoral fin shape in 143 species of labrids from the Great Barrier Reef and the Caribbean. Pectoral fin aspect ratio ranged among species from 1.12 to 4.48 and showed a distribution with two peaks at about 2.0 and 3.0. Higher aspect ratio fins typically had a relatively long leading edge and were narrower distally. Body mass only explained 3% of the variation in fin aspect ratio in spite of four orders of magnitude range and an expectation that the advantages of high aspect ratio fins and flapping motion are greatest at large body sizes. Aspect ratio was correlated with the angle of attachment of the fin on the body (r = 0.65), indicating that the orientation of the pectoral girdle is rotated in high aspect ratio species to enable them to move their fin in a flapping motion. Field measures of routine swimming speed were made in 43 species from the Great Barrier Reef. Multiple regression revealed that fin aspect ratio explained 52% of the variation in size-corrected swimming speed, but the angle of attachment of the pectoral fin only explained an additional 2%. Labrid locomotor diversity appears to be related to a trade-off between efficiency of fast swimming and maneuverability in slow swimming species. Slow swimmers typically swim closer to the reef while fast swimmers dominate the water column and shallow, high-flow habitats. Planktivory was the most common trophic associate with high aspect ratio fins and fast swimming, apparently evolving six times.     

The locomotory function of the fins in the squid Loligo pealei

Kinematic data of high spatial and temporal resolution, acquired from image sequences of adult long-finned squid, Loligo pealei, during steady swimming in a flume, were used to examine the role of fins and the coordination between fin and jet propulsion in squid locomotion. Fin shape and body outlines were digitized and used to calculate fin wave speed, amplitude, frequency, angle of attack, body deformation, speed, and acceleration. L. pealei were observed to have two fin gait patterns with a transition at 1.4-1.8 mantle lengths per second (L_m s^-1) marked by alternation between the two patterns. Fin motion in L. pealei exhibited characteristics of both traveling waves and flapping wings. At low speeds, fin motion was more wave-like; at high speeds, fin motion was more flap-like and was marked by regular periods during which the fins were wrapped tightly against the mantle. Fin cycle frequencies were dependent on swimming speed and gait, and obvious coordination between the fins and jet were observed. Fin wave speed, angle of attack, and body acceleration confirmed the role of fins in thrust production and revealed a role of fins at all swimming speeds by a transition from drag-based to lift-based thrust when fin wave speed dropped below swimming speed. Estimates of peak fin thrust were as high as 0.44-0.96 times peak jet thrust in steady swimming over the range of swimming speeds observed. Fin downstrokes generally contributed more to thrust than did upstrokes, especially at high speeds.     

Gait transition and oxygen consumption in swimming striped surfperch Embiotoca lateralis Agassiz

A flow-through respirometer and swim tunnel was used to estimate the gait transition speed ( U _p-c) of striped surfperch Embiotoca lateralis , a labriform swimmer, and to investigate metabolic costs associated with gait transition. The U _p-c was defined as the lowest speed at which fish decrease the use of pectoral fins significantly. While the tail was first recruited for manoeuvring at relatively low swimming speeds, the use of the tail at these low speeds [as low as 0·75 body (fork) lengths s⁻¹, L _F s⁻¹) was rare (<10% of the total time). Tail movements at these low speeds appeared to be associated with occasional slow manoeuvres rather than providing power. As speed was increased beyond U _p-c, pectoral fin (PF) frequencies kept increasing when the tail was not used, while they did not when PF locomotion was aided by the tail. At these high speeds, the tail was employed for 40–50% of the time, either in addition to pectoral fins or during burst-and-coast mode. Oxygen consumption increased exponentially with swimming speeds up to gait transition, and then levelled off. Similarly, cost of transport ( C _T) decreased with increasing speed, and then levelled off near U _p-c. When speeds ≥ U _p-c are considered, C _T is higher than the theoretical curve extrapolated for PF swimming, suggesting that PF swimming appears to be higher energetically less costly than undulatory swimming using the tail.     

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.     

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     

Body Form and Locomotion in Sharks

A revised interpretation of the mode of action of the heterocercaltail in sharks shows that the upturned tail axis tends to producea thrust directed downwards behind the centre of balance ofthe fish and thus gives a moment turning the head upwards. Thisis countered in two ways—by the rotation of the tail alongits longitudinal axis during each lateral beat, and throughthe action of the ventral hypochordal lobe. The shape of thetail and the mode of action of the tail in all sharks so farconsidered reflects a balance between these three factors, inall of them the net effect being the production of a forwardthrust from the tail that passes directly through the centreof balance of the fiish. There is normally therefore no tendencyfor the fish to turn around the centre of balance in a sagittalplane but there is a net sinking effect that is countered bythe planning effect of the pectoral fins and the ventral surfaceof the head. A study of 56 species of sharks shows that the tail is constructedaccording to a remarkably consistent common plan, the extremesbeing the high angled rather symmetrical tail of pelagic sharkssuch as hums, Lamna and Rhincodon and the straight tails ofbenthic sharks such as Ginglymostoma in which a ventral hypochordallobe is absent. When the general body shape of sharks, includingthe position of insertion of the median and paired fins andthe pattern of growth of fin surface areas is considered, theuniformity of the shark body plan and locomolor function isfurther emphasised. Four patterns of body form in sharks are recognised: 1) Thefast swimming pelagic sharks and the whale sharks have a tailwith a high aspect ratio, a conical head, a lateral fluke onthe caudal peduncle. 2) The generalised sharks typified by theCarcharhinidae, have lower heterocercal angles, a flattenedventral surface on the head and lack the caudal fluke. 3) Thedemersal sharks typified by the catsharks (Scyliorhinidae) havea very low, almost straight tail. The ventral hypochordal lobeis absent and the first dorsal fin is posterior in position.4) The squalomorph sharks are distinct in the absence of theanal fin, presence of a marked epicaudal lobe in the tail andoften an elevated insertion of the pectorals. The anal and second dorsal fins are always the smallest finsand the pectorals grow at the fastest rate. In general thereis an inverse relationship between size and rale of growth ofall fins and the ventral surface of the head. In hammerheadsthe growth data confirms that the head has a significant planingaction in swimming. The pectoral, second dorsal and anal finsshow an extreme constancy of position of insertion in all sharksstudied. The locomotor mechanism of sharks is adapted for anefficient cruising swimming but at the same time, the potentialinstability in the sagittal plan allows for the production ofturning moments that are used in attack and feeding.