Is tilting behaviour at low swimming speeds unique to negatively buoyant fish? Observations on steelhead trout,Oncorhynchus mykiss,and bluegill,Lepomis macrochirus

When swimming at low speeds, steelhead trout and bluegill sunfish tilted the body at an angle to the mean swimming direction. Trout swam using continuous body/caudal fin undulation, with a positive (head-up) tilt angle ( 0 , degrees) that decreased with swimming speed ( u , cm s⁻¹) according to: 0 =(164±96).u^{(−1.14±0.41)} (regression coefficients; mean±2 s.e. ). Bluegill swimming gaits were more diverse and negative (head down) tilt angles were usual. Tilt angle was −3·0 ± 0.9° in pectoral fin swimming at speeds of approximately 0.2–1.7 body length s⁻¹ (Ls⁻¹; 3–24 cm s⁻¹), −4.5 ±2.6° during pectoral fin plus body/caudal fin swimming at 1·2–1·7 L s⁻¹ (17–24cm s⁻¹), and −5.0± 1.0° during continuous body/caudal fin swimming at 1.6 and 2.5 L s⁻¹ (22 and 35cm s⁻¹). At higher speeds, bluegill used burst-and-coast swimming for which the tilt angle was 0.1±0.6°. These observations suggest that tilting is a general phenomenon of low speed swimming at which stabilizers lose their effectiveness. Tilting is interpreted as an active compensatory mechanism associated with increased drag and concomitant increased propulsor velocities to provide better stabilizing forces. Increased drag associated with trimming also explains the well-known observation that the relationship between tail-beat frequency and swimming speed does not pass through the origin. Energy dissipated because of the drag increases at low swimming speeds is presumably smaller than that which would occur with unstable swimming.     

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。     

棒花鱼形态特征的两性异形和雌性个体生育力

测定了棒花鱼(Abbottina rivularis)繁殖期形态特征包括体长、头长、头宽、头高、眼间距、鼻间距、背鳍基长、胸鳍长、胸鳍腹鳍间距、尾柄长、尾鳍长和体重的两性异形和雌性个体生育力。结果表明,雄性个体的数量显著多于雌性个体,雄性个体的体长显著大于雌性个体。特定体长的雌性个体的胸鳍腹鳍间距显著大于雄性个体,头长、头宽、头高、眼间距、鼻间距、背鳍基长、胸鳍长、尾柄长和尾鳍长显著小于雄性个体,雌雄两性体重不存在显著差异。棒花鱼的怀卵数量与体长和体重回归关系显著。偏相关分析显示,当控制第三者恒定时,怀卵数量与体长和体重呈正相关但不显著。棒花鱼存在个体大小和其他局部特征显著的两性异形,雌性个体主要通过腹腔容积的增加提高个体生育力。棒花鱼形态特征的两性异形是性选择和生育力选择共同作用的结果。     

Does body and fin form affect the maneuverability of fish traversing vertical and horizontal slits?

Synopsis The purpose of this study was to determine if body and fin form affected the maneuverability of teleostean fishes as measured by their ability to negotiate simple obstacles. Obstacles were vertical and horizontal rectangular slits of different widths, for which width was defined as the minimum dimension of a slit irrespective of slit orientation. Performance was measured as the smallest slit width traversed. Three species with different body and fin patterns were induced to swim through slits. Species tested were; goldfish Carassius auratus with a fusiform body, anterio-ventral pectoral fins and posterio-ventral pelvic fins; silver dollars Metynnis hypsauchen with the same fin configurations but a gibbose body; angelfish Pterophyllum scalare with a gibbose body and anterio-lateral pectoral fins. Minimum slit widths negotiated were normalized with the length of various body dimensions: total length, maximum width, span at the pectoral fins, and volume^1/3 (numerically equal to mass^1/3). Goldfish had the poorest performance, requiring the largest slit widths relative to these body dimensions. No consistent patterns in performance were found for silver dollars vs. angelfish. There were no differences among species in the ratio of minimum vertical slit width negotiated to that for horizontal slits, indicating fish were equally able to control posture while swimming on their sides. There were also no consistent patterns in the times taken to transit slits. Although the deep-bodied fish were able to maneuver through smaller slits, the most striking result is the similarity of minimum slit widths traversed in spite of the large variation in body form. Body form and fin plan may be more important for maneuvering and posture control during sub-maximum routine activities.     

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。     

The swimming endurance of threespine sticklebacks, Gasterosteus aculeatus L., from the Afon Rheidol, Wales

The endurance of threespine sticklebacks, Gasterosteus aculeatus , swimming with pectoral fin locomotion at 20° C in a laboratory flume was measured. Each trial lasted a maximum of 480 min. At a speed of 4 body lengths per sec (L s⁻¹) all fish were still swimming at the end of the trial, but endurance decreased at higher speeds. At speeds of 5 or 6 L s⁻¹ (20–30 cm s⁻¹) a few fish still maintained labriform locomotion for the 480 min. However, at a speed of 7 L s⁻¹ all fish furled their pectoral fins and used body and caudal fin propulsion but fatigued rapidly. During sustained swimming, fish could cover distances of 6 km or more. No significant differences between males and females were found.     

中国平鳍鳅科鱼类一新纪录种

20 0 2年 6月于云南省河口瑶族自治县采集到鱼类标本 3尾 ,经鉴定为我国华吸鳅属鱼类之新纪录种———红河华吸鳅 (Sinogastromyzonchapaensis)。测量标本 3尾均保存在台湾清华大学。体长 35～ 5 0mm。背鳍iii,8;臀鳍ii,5 ;胸鳍xiv～xv ,14～ 16 ;腹鳍x～xi,11～ 12。侧线鳞 6 0～ 6 4。体长为体高的 7 0～ 7 2倍 ,为体宽的 4 3～ 4 6倍 ,为头长的 4 9～ 5 1倍 ,为尾柄长的 5 4～ 6 0倍 ,为尾柄高的 12 7～ 14 0倍 ,为背鳍前距的 2 2倍 ,为腹鳍前距的 2 4～ 2 7倍。头长为头高的 1 8～ 1 9倍 ,为头宽的 0 9～ 1 1倍 ,为吻长的 2 0～2 1倍 ,为眼径的 4 7～ 5 0倍 ,为眼间距的 2 0～ 2 3倍。尾柄长为尾柄高的 2 2～ 2 6倍。头宽为口宽的 3 7～4 6倍。     

Morphological variations in bluegill, Lepomis macrochirus, with particular emphasis on growth-related changes

Morphological variations in bluegill, Lepomis macrochirus, including growth-related changes, sexual dimorphism and morphological differences between populations in different habitats, were examined in samples from three reservoirs in Kagawa, Japan. Body measurements demonstrated frequent growth-related proportional changes, particularly in body depth, body width, caudal peduncle length and head length, which all showed relative increases, whereas first dorsal fin length, caudal fin length and orbital diameter became relatively shorter. Body weight increased relatively with growth, with relative growth coefficients of 3.339–3.454 for regressions between total length and body weight. Such body weight increases were likely due to the relative increases in body depth and width, and caudal peduncle depth. Although counts of fin spines, fin rays and gill rakers did not change with growth, those of scales tended to increase. Males were significantly larger than females in body depth, caudal peduncle length, head length and body weight. Sexual dimorphism was also apparent in body coloration during the breeding season. In addition, a number of morphological differences were observed between individuals from different habitats.     

广西发现版纳鱼螈白化幼体一例

2007年5月,在广西北流市六麻镇捕到一例雄性版纳鱼螈(Ichthyophis bannanicus)白化幼体。该个体完全白化。体重9.1 g,全长195 mm,尾长3.85 mm,体宽10.36 mm,吻长3.09 mm,尾鳍高5.71 mm,吻端至第一环沟9.47 mm,吻端至第二环沟13.41 mm,鼻间距2.42 mm,眼间距5.17 mm。与正常个体对比发现:该白化幼体的尾长、体宽、尾鳍高大于正常范围,吻端至第二环沟小于正常范围,其余数据均在正常范围内。     

A new deep‐water chimaerid species, Hydrolagus lusitanicus n. sp., from off mainland Portugal with a proposal of a new identification key for the genus Hydrolagus(Holocephali: Chimaeridae) in the north‐east Atlantic

A new chimaerid species closely related to Hydrolagus pallidus is described from 13 specimens captured on the Portuguese continental slope (north‐east Atlantic) by commercial longliners at depths of c . 1600 m. The new species is large‐bodied with a rose to light brown body colouration. Hydrolagus lusitanicus n.sp. presents a combination of external morphological characters that allow it to be clearly differentiated from its congeners, in particular, the ratios of pectoral fin length: pectoral fin width and pelvic fin length: pelvic fin width; in having a serrated posterior edge of the dorsal spine; a high number of ridges in the dental plates. Additionally in males, there are differences on the shape and number of hooks in the frontal tenacula, on the number of spines in the prepelvic tenacula and on the length of the pectoral fin margin.     

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。     

THERMAL INFRARED RADIATION FROM FREE LIVING WHALES

As part of a search for new detection techniques, and for obtaining information on whale surface temperatures, an Agema Thermovision 880 thermal imaging system was used to detect thermal infrared radiation from whales. The study took place along the northern coast of Norway and the northwest coast of Svalbard (68° to 80° N latitude). The emphasis of the study was on minke whales, but humpback, fin, blue and sperm whales were also observed. The apparent radiation temperature was strongly dependent on sea conditions, signal angle, and atmospheric interference; detection depended thus upon weather. During the study, sea surface temperatures varied as much as 7°C but the sea and minke whale body trunk surfaces were usually within 0.0° to 0.1°C of each other. The other species observed had temperature differences of 0.0° to 1.0°C relative to the sea surface. Temperature differences between sea water and whale appendages ranged from 0.0° to 6.0°C. The indicated maximum difference between sea water and blow (i.e., expired air) was 4.0°;C, while the maximum difference for the blowhole was 4.1°C. The results from all whales observed support the belief that the main body trunk is normally not a heat window, this function being reserved for the appendages. However, the results also indicate a regulated dermal blood flow determining heat loss from the body trunk. Detection of whales by thermal infrared radiation from the body trunk appears unreliable; in contrast, the blow and blowhole provided a consistent positive signal with apparent temperature differences to the surroundings ranging from 0.2° to 4.1°C.     

Tilting behaviour of the Atlantic mackerel, Scomber scombrus, at low swimming speeds

Negatively-buoyant Atlantic mackerel, Scomber scombrus L., (fork length 30–39 cm) tilt their bodies with the head up while swimming at speeds below 0.8 body length per second (B.L. s⁻¹). This behaviour is quantitatively described by the body attack angle and swimming speed measured from film records. The maximum recorded body attack angle was 27° in a 32 cm-long fish swimming at 0.45 B.L. s⁻¹ while its nose followed a course close to the horizontal. In general, larger body attack angles were shown at lower swimming speeds and were associated with denser bodies at each speed. We consider that this behaviour pattern allows the fish to maintain a chosen swimming depth while its body creates lift by acting as a hydrofoil. Lift from the fins is insufficient at low swimming speeds.     

Body build structure of neonates

The paper presents anthropometric data on 292 healthy neonates delivered of normal births at the Women's Hospital of Tartu University (150 boys and 142 girls). The parameters of the neonates' physical development measured included height, weight, sitting height, length of sternum and abdomen, shoulder width, upper and lower width and depth of thorax, width and depth of abdomen, D. cristarum, D. trochanterica, pelvic depth, 12 circumferences, foot length and two skinfolds (on abdomen and back). The mean weight of a neonate was 3620.5 g±448.7 g (minimum 2400 g and maximum 4854 g). Boys were somewhat heavier than girls (3684.7 g and 3551.3 g respectively). The average height of the infants was 49.9 cm±1.9 cm (minimum 44 cm and maximum 54.5 cm). Correlation analysis of the characteristics showed that body structure is a system of wellcorrelated anthropometric measurements where the leading role belongs to height and weight. The changes in the relation between height and weight (height-weight classification in 3×3SD classes) cause systemic changes in other measurements. Therefore, in further micropaediatric and clinical research, the height-weight classification could be used as the primary model of the body as a whole.     

Do body and fin form affect the abilities of fish to stabilize swimming during maneuvers through vertical and horizontal tubes?

Goldfish, Carassius auratus, silver dollar, Metynnis hypsauchen, and angelfish, Pterophyllum scalare were induced to swim through narrow vertical and horizontal tubes ranging in length from 0 to 20 cm (approximately 0 to 3 times total fish length, FL). The ability to stabilize the body while negotiating these confined spaces was quantified as (1) the minimum width of vertical (w_v) and horizontal (w_h) tubes traversed, where width is the smaller cross-sectional dimension of the tube, (2) the ratio w_v/w_h, and (3) transit speed through the tubes. Tube width was expressed as relative width, obtained by dividing tube width by fish length. Minimum relative widths traversed increased from 0.15 to 0.19 in the order silver dollar > angelfish > goldfish for vertical tubes and from 0.17 to 0.18 in the order goldfish=silver dollar > angelfish for horizontal tubes. w_v/w_h increased from 0.91 to 1.10 in the order silver dollar=angelfish > goldfish. Minimum tube widths generally increased with tube length for vertical tubes. Although significant differences in relative minimum widths among species were found, these were small. In contrast, for horizontal tubes, there was no significant effect of tube length on minimum tube width for any species. Large differences were found in transit speed. Transit speed generally decreased as the tube length increased. The slope of the relationship between transit speed and tube length varied among species generally increasing from – 0.41 to – 1.16 for horizontal tubes in the order goldfish > silver dollar > angelfish and from – 0.42 to – 1.07 in the order silver dollar > goldfish > angelfish for vertical tubes. As a result, goldfish usually took longest to traverse tubes of zero length but the shortest time to traverse the longest tubes. In contrast, angelfish traversed short tubes in the least time and long tubes in the greatest time. Deeper bodied angelfish swam slowly and traversed tubes with difficulty because they required experience during each trial to replace median and paired fin with body and caudal fin swimming. According to our data, goldfish were best able to swim in confined spaces.     

Sexual dimorphism and developmental patterns in the external morphology of the vaquita,Phocoena sinus

A total of 56 vaquitas (Phocoena sinus) were examined to evaluate their sexual dimorphism and isometric and/or allometric growth in 35 external characteristics. Absolute and relative (to total length) measurements and growth rates were compared between sexually immature and mature females and males. T‐tests and analysis of variance (ANOVA) and covariance (ANCOVA) were used to evaluate sexual dimorphism. Sexual dimorphism in the vaquita was detected in the total length, head region (from blowhole to tip of upper jaw), anterior section of the body (from dorsal fin to tip of upper jaw), dorsal fin and the genital and anal regions. Fluke width is relatively larger in mature males than immature males, but in females this relative metric does not change during their development. In addition, males present a higher dorsal fin. These somatic changes are probably related to the swimming capacity (speed, agility, maneuvering) during the breeding season and/or foraging activities. A linear model of growth was used to determine possible proportional changes with respect to total body length through the development of 33 external characteristics. The anterior region of the body and the flippers were relatively larger in immature individuals than in mature ones.     

河南省淮河流域鳑鲏亚科5种鱼形态差异分析

为进一步从可量性状比较中华鳑鲏(Rhodeus sinensis)、越南鱊(Acheilongnathus tonkinensis)、大鳍鱊(A. macropterus)、兴凯鱊(A. chankaensis)和斑条鱊(A. taenianalis)的种间形态差异, 丰富鳑鲏亚科鱼类的形态分类特征, 研究采用多变量形态度量学方法对河南省淮河流域这5种鱼的形态进行比较分析。结果表明: 这5种鱼在体宽/体长、头长/体长、吻长/体长、尾柄长/体长、背鳍基底长/体长、腹鳍长/体长、臀鳍长/体长和头长/吻长8个比值性状上存在极显著性差异(P< 0.01), 在全长/体长、体高/体长2个比值性状上存在显著性差异(P<0.05), 这些差异主要集中在鱼体的头部、尾部和鳍等部位。主成分分析、聚类分析和判别分析显示5种鱼存在显著性形态差异, 斑条鱊与越南鱊的差异程度最大, 与大鳍鱊差异程度最小。判别分析获得的判别准确率在82.35%—100.00%变化, 可以从一定的角度区分这5种鱼。     

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。     

Testis and gonopodium development in Anableps Dowi (Pisces: Anablepidae) correlated with pituitary gonadotropic zone area

Testicular development in the viviparous fish, Anableps dowi, is described from embryonic stages through sexual maturation and is correlated with development of the gonadotropic zone of the pituitary. Only isolated spermatogonia or cysts of early spermatogonia are found in embryos 1.8 to 4.4 cm in length and postnatal specimens 5.4 to 8.8 cm in length. Cysts with more advanced spermatogonia are seen in specimens from 7.9 to 10.8 cm in length. Spermatogenetic meioses are first observed in a 10.2 cm male. Specimens greater than 12.0 cm have mature spermatozoa (partial spermatozeugmata) within the main testicular ducts, indicating gonadal maturation. The morphological transformation of the anal fin into the intromittent gonopodium is also described, using both whole and cleared specimens. Even in the smallest postnatal male available (5.4 cm), the anal fin can be distinguished from that of an equivalent sized female. Anal fin changes proceed until the mature gonopodium is developed, when body lengths greater than 16 cm are reached. Testicular maturation, defined as the presence of partial spermatozeugmata in the main testicular ducts, precedes the completion of gonopodial development. Measurements of ventral gonadotropic zone area in pituitary mid-sagittal sections show a continuous increase from neonatal through sexually mature specimens. The results point to a role for testicular androgens in early testis development.