Dorsal fin in the white shark, Carcharodon carcharias: a dynamic stabilizer for fast swimming

Transverse sections of the skin in the dorsal fin of the white shark, Carcharodon carcharias, tiger shark, Galeocerdo cuvier, and spotted raggedtooth shark, Carcharias taurus, show large numbers of dermal fiber bundles, which extend from the body into the fin. The bundles are tightly grouped together in staggered formation (not arranged in a straight line or in rows). This arrangement of dermal fibers gives tensile strength without impeding fiber movement. Tangential sections indicate that the fibers in all three species are strained and lie at angles in excess of 60 degrees . Of the three species investigated the dermal fibers in C. carcharias are the most densely concentrated and extend furthest distally along the dorsal fin. The overall results indicate that the dorsal fin of C. carcharias functions as a dynamic stabilizer and that the dermal fibers are crucial to this role. The fibers work like riggings that stabilize a ship's mast. During fast swimming, when the problems of yaw and roll are greatest, hydrostatic pressure within the shark increases and the fibers around the body, including in the dorsal fin, become taut, thereby stiffening the fin. During slow swimming and feeding the hydrostatic pressure is reduced, the fibers are slackened, and the muscles are able to exert greater bending forces on the fin via the radials and ceratotrichia. In C. carcharias there is a trade-off for greater stiffness of the dorsal fin against flexibility.     

似鲇高原鳅皮肤与鳍的组织学观察

采用石蜡切片技术及H.E和AB-PAS染色方法,对似鲇高原鳅(Triplophysa siluroides)头部、腹部、背部、侧线部和尾部皮肤结构及胸鳍、腹鳍、背鳍、臀鳍和尾鳍的组织结构进行观察。各部位皮肤均由表皮和真皮构成,真皮包括疏松层和致密层,不同部位皮肤厚度不同。表皮层腹部最厚,为(84.62±10.82)μm,侧线部最薄,为(14.97±3.95)μm,各部位表皮厚度差异显著。表皮层分布着黏液细胞、棒状细胞及味蕾。疏松层头部最厚,为(282.71±70.56)μm,尾部最薄,为(29.07±4.88)μm,该层分布有黑色素细胞、空泡状细胞和颗粒腺,而黏液腺分布于致密层。各部位的鳍均由表皮层、胶原纤维层、胶原下层及鳍条构成,表皮层与皮肤表皮层组成相似,鳍条是矿化的结缔组织。     

A new loach, Cobitis shikokuensis (Teleostei: Cobitidae), from Shikoku Island, Japan

A new species of spinous loach, Cobitis shikokuensis, is described based on 297 specimens from Shikoku Island, Japan. The new species was formerly known as the Shikoku group of Cobitis takatsuensis. It can be distinguished from other species of Cobitis and closely related genera by a combination of the following characters: dorsal fin with 6 branched soft rays; anal fin with 5 branched soft rays; one brownish streak across eye from the tip of nose, no streak on cheek; a black spot smaller than eye diameter near the dorsal corner of the caudal fin base; 3–5 small brownish speckles on ventral side of caudal peduncle; high caudal peduncle with well-developed fleshy keels on dorsal and ventral side; a lamina circularis at base of dorsal part of pectoral fin absent; first branched soft ray of pectoral fin broad in males; pectoral soft rays widely branched from the approximate midpoint; last anal fin ray with 2 elements; interorbital width 11.2–17.1% of head length.     

The tail of the Ordovician fish Sacabambaspis

The tail of the earliest known articulated fully skeletonized vertebrate, the arandaspid Sacabambaspis from the Ordovician of Bolivia, is redescribed on the basis of further preparation of the only specimen in which it is most extensively preserved. The first, but soon discarded, reconstruction, which assumed the presence of a long horizontal notochordal lobe separating equal sized dorsal and ventral fin webs, appears to have considerable merit. Although the ventral web is significantly smaller than the dorsal one, the presence of a very long notochordal lobe bearing a small terminal web is confirmed. The discrepancy in the size of the ventral and dorsal webs rather suggests that the tail was hypocercal, a condition that would better accord with the caudal morphology of the living agnathans and the other jawless stem gnathostomes.     

A well defined spinocerebellar system in the weakly electric teleost fish Gnathonemus petersii. A tracing and immuno-histochemical study.

Long ascending fiber systems were investigated in the spinal cord of a teleost fish, Gnathonemus petersii. Concomitant results of Fink-Heimer degeneration tracing as well as CaBP28K immunohistochemical labelling demonstrate the existence of a well defined direct pathway from the very lowest spinal level to the caudal lobe of the cerebellum. HRP retrograde labelling shows that this pathway originates in a cellular column located in the most ventral part of the lateral column next to the lateral extremity of the ventral horn. From each spinal segment, the large axons of these cells gather and form a strip shaped tract at the periphery of the lateral column immediately dorsal to the cell column from which they originate. The spinal course of these fibers is ipsilateral; they give off a large number of collaterals to the lateral reticular nucleus. Bypassing the trigeminal motor nucleus, the lateral column tract courses dorsally to the paratrigeminal command associated nucleus between the lateral lemniscus and the nucleus preeminentialis and with a ventro-dorsally oriented large loop, turns in the caudal direction and penetrates into the cerebellar caudal lobe. Running caudally in the dorsal granular layer of the caudal lobe, it shifts more and more medially and crosses the midline whilst decussating with the contralateral tract on the dorsal margin of the molecular layer of the caudal lobe. Finally, the tract splits off and terminates throughout the granular layer of the caudal lobe. The main characteristics of this pathway are similar to those of the ventral spinocerebellar tract of higher vertebrates; it conveys information from all spinal levels directly to the contralateral cerebellum. However, it does not seem to receive direct synaptic input from the periphery, since projection of the dorsal root fibers appears to be limited to the dorsal ipsilateral half of the spinal cord. The appearance of such a pathway in a teleost fish is probably related to the existence of a well developed proprioceptive system in this species.     

Balitora eddsi,a new species of hillstream loach (Ostariophysi: Balitoridae) from Nepal

A new species of hillstream loach Balitora eddsi is described from the Karnali River drainage in south‐western Nepal. The new species is distinguished from all its congeners by possessing the following combination of characters: six to seven unbranched pectoral‐fin rays, pelvic‐fin length 12–14% standard length (L_S), dorsal surface without circular or irregular shaped dark blotches, snout pointed, median lobe between anterior rostral barbels pointed posteriorly, dorsal‐fin origin posterior to pelvic‐fin origin, lateral line scales 66–67, caudal peduncle length 22–23·2% L_S, caudal peduncle depth 4·1–4·2 times its length.     

The musculotendinous system of an anguilliform swimmer: Muscles, myosepta, dermis, and their interconnections in Anguilla rostrata

Eel locomotion is considered typical of the anguilliform swimming mode of elongate fishes and has received substantial attention from various perspectives such as swimming kinematics, hydrodynamics, muscle physiology, and computational modeling. In contrast to the extensive knowledge of swimming mechanics, there is limited knowledge of the internal body morphology, including the body components that contribute to this function. In this study, we conduct a morphological analysis of the collagenous connective tissue system, i.e., the myosepta and skin, and of the red muscle fibers that sustain steady swimming, focusing on the interconnections between these systems, such as the muscle-tendon and myosepta-skin connections. Our aim is twofold: (1) to identify the morphological features that distinguish this anguilliform swimmer from subcarangiform and carangiform swimmers, and (2) to reveal possible pathways of muscular force transmission by the connective tissue in eels. To detect gradual morphological changes along the trunk we investigated anterior (0.4L), midbody (0.6L), and posterior body positions (0.75L) using microdissections, histology, and three-dimensional reconstructions. We find that eel myosepta have a mediolaterally oriented tendon in each the epaxial and hypaxial regions (epineural or epipleural tendon) and two longitudinally oriented tendons (myorhabdoid and lateral). The latter two are relatively short (4.5-5% of body length) and remain uniform along a rostrocaudal gradient. The skin and its connections were additionally analyzed using scanning electron microscopy (SEM). The stratum compactum of the dermis consists of approximately 30 layers of highly ordered collagen fibers of alternating caudodorsal and caudoventral direction, with fiber angles of 60.51 +/- 7.05 degrees (n = 30) and 57.58 +/- 6.92 degrees (n = 30), respectively. Myosepta insert into the collagenous dermis via fiber bundles that pass through the loose connective tissue of the stratum spongiosum of the dermis and either weave into the layers of the stratum compactum (weaving fiber bundles) or traverse the stratum compactum (transverse fiber bundles). These fiber bundles are evenly distributed along the insertion line of the myoseptum. Red muscles insert into lateral and myorhabdoid myoseptal tendons but not into the horizontal septum or dermis. Thus, red muscle forces might be distributed along these tendons but will only be delivered indirectly into the dermis and horizontal septum. The myosepta-dermis connections, however, appear to be too slack for efficient force transmission and collagenous connections between the myosepta and the horizontal septum are at obtuse angles, a morphology that appears inadequate for efficient force transmission. Though the main modes of undulatory locomotion (anguilliform, subcarangiform, and carangiform) have recently been shown to be very similar with respect to their midline kinematics, we are able to distinguish two morphological classes with respect to the shape and tendon architecture of myosepta. Eels are similar to subcarangiform swimmers (e.g., trout) but are substantially different from carangiform swimmers (e.g., mackerel). This information, in addition to data from kinematic and hydrodynamic studies of swimming, shows that features other than midline kinematics (e.g., wake patterns, muscle activation patterns, and morphology) might be better for describing the different swimming modes of fishes.     

记比耶鱼(Birgeria)在中国的首次发现

记述了采自云南罗平晚三叠世法郎组竹杆坡段的比耶鱼一新种──刘氏比耶鱼（Ｂｉｒｇｅｒｉａ ｌｉｕｉ ｓｐ． ｎｏｖ．）,这是比耶鱼化石在中国的首次发现。刘氏比耶鱼与产自瑞士圣乔治山中三叠世边境沥青层的史氏比耶鱼最为相近,两者仅在尾柄长高之比、尾鳍长短与上下叶外缘交角、背鳍和臀鳍辐状支鳍骨的数目、臀鳍辐状骨骨板的大小、以及侧线管骨化与否等特征上略有差异。比耶鱼与软骨硬鳞鱼超目的鲟形目最为接近,两者共有一系列特征,如除尾上叶外体侧裸露,副蝶骨末端伸达头后,鳃盖骨退化;但比耶鱼同时也具有不少的特有特征,代表了软骨硬鳞鱼超目的另一类群──比耶鱼目（Ｂｉｒｇｅｒｉｉｆｏｒｍｅｓ　ｏｒｄ． ｎｏｖ．）。刘氏比耶鱼的发现进一步表明华南扬子区中、晚三叠世鱼类化石与特提斯西部的鱼群具有密切的动物地理关系。     

Loaches of the genus Lepidocephalichthys, from Manipur, with description of a new species

A new species Lepidocephalichthys manipurensis , is described, confined to the Chandel district of Manipur near the adjoining borderland areas of Manipur, India and Burma (Myanmar). It is distinguished by the following combination of characters: a sharp small black dot just above the upper base of the caudal fin; 8–9 dorsal short dark ashy brown bars from occiput to the base of the caudal fin; absence of scales on the vertex of head; caudal fin fork, pectoral, ventral and anal fins are non-immaculate; least depth of caudal peduncle 50·00–60·24% (mean 54·09) of its length and 7·69–8·11% L , S (mean 8·22); caudal fin with 4–5 W-shaped bands: a single dark black stripe from tip of snout to eye; 8–11 spots on the mid lateral line; and 30–31 vertebrae. A key to the identification of lepidocephalid loaches of Manipur is provided.     

中国贵州省穴居盲鳅一新种(鲤形目,爬鳅科)

记述了采集于贵州省荔波县佳荣镇水井湾溶洞(25°28’N,108°06’E)适应洞穴环境的鳅类1新种:佳荣盲高原鳅Triplophysa jiarongensis sp.nov.。新种与之前记录的7种分布于西江水系的高原鳅(阿庐高原鳅、个旧盲高原鳅、长须盲高原鳅、巨头高原鳅、邱北盲高原鳅、石林盲高原鳅和天峨高原鳅)同属典型洞穴鱼类,都具有一系列与洞穴环境有关的适应性特征。新种与本属其它种类的区别主要为:胸鳍长,后伸达腹鳍起点;尾鳍微凹形;体表色素退化,光滑裸露无鳞;背鳍截形,起点位于腹鳍起点略后方;腹鳍后伸盖过泄殖孔;臀鳍截形;尾柄上下缘存在脂状鳍褶;背鳍分支鳍条8;臀鳍分支鳍条6;胸鳍分支鳍条11;脊椎骨总数4+34;眼完全退化,外观无痕迹;鳔前室被骨质鳔囊包裹,后室发达膨大呈游离膜质鳔。此外还介绍了其栖息地概况和部分生态学信息。     

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。     

四川省条鳅亚科鱼类的研究——Ⅰ.副鳅、条鳅和山鳅属鱼类的整理(鲤形目:鳅科)

本文为四川省条鳅亚科鱼类分类研究的第一部分,对分布于四川省的副鳅属(Paracobitis)、条鳅属(Nemacheilus)和山鳅属(Oreias)鱼类进行了比较系统的整理,这3个属分布在四川共有5种和亚种,其中乌江副鳅(Paracobitis wujiangensis sp.nov.)为新种。     

Acanthodes bourbonensis n.sp., ein neuer Acanthodier (Acanthodii: Pisces) aus dem Autunium (Unterperm) von Bourbon l’Archambault (Allier,Frankreich)

WithAcanthodes bourbonensis n.sp. another acanthodian from Lower Permian basins of Europe is described. The new species is similar toAcanthodes gracilis (Beyrich) from Silesia (Poland), but it differs from this and all other species of the genus in the development of the pectoral fins, dorsal fin, anal fin and caudal fin. In pectoral fins, dorsal and anal fin there are different ceratotrichia as supporting elements and pectoral fins are attaching along a row of oblonged large scales. In the caudal fin there is an epichoral appendix first found byHeyler (1969).     

A new miniature species of the genus Triplophysa (Balitoridae: Nemacheilinae) from Yunnan, China

During a re-examination of museum specimens of Triplophysa species, some specimens that had been collected from the Jialonghe River in Yunnan Province, China, in April 1975, were identified as a new species. Triplophysa parvus n. sp. can be distinguished by the following combination of characters: dorsal fin rays 3, ; anal fin rays 3, ; pectoral fin rays 1, 11; scales absent; two saddle-like blotches with fuzzy borders cranial to the dorsal fin and four saddle-like blotches caudal to the dorsal fin; distal margin of the dorsal fin emarginate; pelvic fin reaching caudally almost to the anus; anus located immediately cranial to the origin of the anal fin; caudal fin forked; caudal chamber of air bladder reduced to a small free protuberance; head slightly laterally compressed, head deeper than wide at nape; length of caudal peduncle being 18.0–20.0% of standard length; depth of caudal peduncle being 7.8–8.4% of standard length; eye diameter 17.6–21.4% of head length; body depth being 60.7–70.2% of head length; caudal peduncle depth being 39.1–45.0% of caudal peduncle length; and body width at the base of caudal peduncle 59.0–68.0% of the body depth at the base of caudal peduncle. These characters allow a distinction from the similar species of T. nasobarbatula, T. nandanensis, and T. macromaculata.     

A new cave‐dwelling loach,Triplophysa xichouensis sp. nov. (Teleostei Nemacheilidae) from Yunnan,China

A new cave‐dwelling loach of the genus Triplophysa, T. xichouensis, is described from an outlet of a subterranean river in Xisa Town, Xichou County, Yunnan Province, China. It can be distinguished from its congeners by the following characters: dorsal‐fin rays iii, 8; anal‐fin rays ii, 6; pectoral‐fin rays i, 9 or 10; pelvic‐fin rays i, 5 or 6; branched caudal‐fin rays 16(8+8); eyes highly degenerated to a very tiny black dot; dorsal‐fin origin closer to snout tip than to caudal‐fin base and anterior to vertical line of pelvic‐fin origin; pectoral fin length about two‐thirds the distance between pectoral‐fin origin to pelvic‐fin origin; caudal peduncle slender, its length about three times its depth; caudal fin emarginate; body smooth and scaleless; lateral line complete and straight; anterior chamber of air bladder wrapped in dumbbell‐shaped bony capsule and the posterior one well developed, long, oval; intestine short, bending in zigzag shape behind stomach. A key for the cave‐dwelling species of Triplophysa is provided. urn:lsid:zoobank.org:pub:9162FFB1‐7911‐47C3‐AE50‐6A00E9590327     

乐山棒花鱼形态特征的两性异形和雌性个体生育力

测定了乐山棒花鱼(Abbottina kiatingensis)繁殖期形态特征包括体长、头长、头宽、头高、吻长、眼后头长、眼径、眼间距、体高、尾柄长、尾柄高、尾鳍长、背鳍基前距、背鳍基长、腹鳍基前距、腹臀间距、体重和去内脏体重的两性异形和雌性个体生育力。繁殖期雄性个体的数量显著多于雌性个体,雌雄两性个体的体长差异不显著。特定体长的雌性个体的头长、头宽、头高、吻长、眼后头长、尾柄高、背鳍基前距、背鳍基长和去内脏体重显著小于雄性个体,其余指标不存在明显的差异。回归分析表明,乐山棒花鱼的怀卵数量与体长和体重回归关系显著,雌性通过个体大小(体长和体重)的增加来提高个体生育力。     

Observations on the attachment by the monogenean, Anoplodiscus australis, to the caudal fin of Acanthopagrus australis

The unarmed haptor of Anoplodiscus australis erodes the epidermis and attaches to the basal lamina above the stratum compactum in the caudal fin of Acanthopagrus australis by an eosinophilic, weakly PAS-positive and strongly toluidine blue-positive secretion. Ultrastructural evidence shows that the adhesive secretion, in the form of rod-shaped bodies, is produced by subtegumentary cells that connect by ducts to the thin, ventral syncytial tegument of the haptor; these bodies pass into the tegument, then coalesce in the host-parasite interface. This means of attachment has developed by an enhancement and regional specialization of the subtegumentary secretory cells associated with a syncytial tegument in monogeneans and some other platyhelminths. The available evidence indicates that the adult parasite is permanently attached.     

Larval and juvenile Polymetme elongata (Stomiiformes: Phosichthyidae) collected from Suruga Bay and offshore waters, Japan

Two larvae [17.4 mm standard length: SL (postflexion stage)] and 26.1 mm SL (transformation stage)] and a juvenile (31.7 mm SL) of a phosichthyid, Polymetme elongata, from Suruga Bay and offshore waters, central Japan, are described. These specimens had an elongate body with relatively short preanal length (53–63% SL), long anal fin base (2.6–3.4 times dorsal fin base length), and anal fin origin below dorsal fin base, and were further characterized by a blackish flap on each eye and internal clusters of melanophores (e.g., along caudal myosepta around midlateral line and on ventral margin of caudal peduncle). The short preanal length and larval melanophore pattern were very similar to those of another phosichthyid, Yarrella blackfordi, from the Atlantic Ocean.     

Two new species of Hyphessobrycon (Characiformes: Characidae) from the headwaters of the Tapajós and Xingu River basins,Pará, Brazil

Two new species of Hyphessobrycon are described from the headwaters of the Tapajós and Xingu River basins, Pará, Brazil. Both new species can be distinguished from congeners by the presence of a vertically elongate humeral blotch, a conspicuous round to vertically oblong caudal‐peduncle blotch not extending onto the distal portions of the middle caudal‐fin rays, a conspicuous blotch on the central portion of the third infraorbital immediately ventral to the eye, the lack of a conspicuous longitudinal stripe and the lack of sexual dimorphism in the extension of the caudal‐peduncle blotch. Hyphessobrycon delimai n. sp. can be distinguished from Hyphessobrycon krenakore n. sp. by the extent of the caudal‐peduncle blotch which extends across most of the caudal‐peduncle depth (v. restricted to the middle portion of the caudal peduncle), the presence of dark chromatophores uniformly scattered along the length of the interradial membranes of the dorsal, anal and caudal fins (v. concentrated on the distal one‐half or one‐fourth of the interradial membranes) and the absence of small bony processes on the pelvic and anal fins of mature males (v. small bony processes present).