Endurance swimming of European eel

A long‐term swim trial was performed with five female silver eels Anguilla anguilla of 0·8–1·0 kg ( c . 80 cm total length, L _T) swimming at 0·5 body lengths (BL) s⁻¹, corresponding to the mean swimming speed during spawning migration. The design of the Blazka‐type swim tunnel was significantly improved, and for the first time the flow pattern of a swim tunnel for fish was evaluated with the Laser‐Doppler method. The velocity profile over three different cross‐sections was determined. It was observed that 80% of the water velocity drop‐off occurred over a boundary layer of 20 mm. Therefore, swim velocity errors were negligible as the eels always swam outside this layer. The fish were able to swim continuously day and night during a period of 3 months in the swim tunnel through which fresh water at 19° C was passed. The oxygen consumption rates remained stable at 36·9 ± 2·9 mg O₂ kg⁻¹ h⁻¹ over the 3 months swimming period for all tested eels. The mean cost of transportation was 28·2 mg O₂ kg⁻¹ km⁻¹. From the total energy consumption the calculated decline in fat content was 30%. When extrapolating to 6000 km this would have been 60%, leaving only 40% of the total energy reserves for reproduction after arriving at the spawning site. Therefore low cost of transport combined with high fat content are crucial for the capacity of the eel to cross the Atlantic Ocean and reproduce.     

Behavioural profiles of inbred mouse strains used as transgenic backgrounds. I: motor tests

One of the characteristic manifestations in several neurodegenarative diseases is the loss of voluntary motor control and the development of involuntary movements. In order to determine the suitability of six mouse strains as transgenic background strains we investigated performance on a variety of tasks designed to identify subtle changes in motor control. On both the accelerating and the staggered speed rotarod all six mouse strains performed well. However, latency to fall from the rod was sensitive to both rotarod speed and repeated exposure to the apparatus. Performance of the DBA/2 mouse strain was highly variable across the time points used. On the acoustic startle test CBA mice showed the greatest degree of reactivity to the acoustic startle stimuli with both the C57 and DBA showing the least. Complex strain differences were also identified on measures of habituation to the startle stimuli and variations in the prepulse noise level, and prepulse/startle delay. Gait analysis using the footprint test did not reveal strain differences on measures of base width, overlap or stride length but the 129S2/Sv strain took significantly longer to traverse the runway than the other mouse strains. Finally, the swim tank test detected complex strain differences in swim speed, and the number of fore- and hindpaw paddles required to swim the length of the tank. These data taken together suggest that choice of background strain is a crucial consideration for the repeated behavioural assessment of motor deficits in transgenic mouse models of disease.     

Testing ontogenetic patterns of sexual size dimorphism against expectations of the expensive tissue hypothesis,an intraspecific example using oyster toadfish (Opsanus tau)

Trade‐offs associated with sexual size dimorphism (SSD) are well documented across the Tree of Life. However, studies of SSD often do not consider potential investment trade‐offs between metabolically expensive structures under sexual selection and other morphological modules. Based on the expectations of the expensive tissue hypothesis, investment in one metabolically expensive structure should come at the direct cost of investment in another. Here, we examine allometric trends in the ontogeny of oyster toadfish (Opsanus tau) to test whether investment in structures known to have been influenced by strong sexual selection conform to these expectations. Despite recovering clear changes in the ontogeny of a sexually selected trait between males and females, we find no evidence for predicted ontogenetic trade‐offs with metabolically expensive organs. Our results are part of a growing body of work demonstrating that increased investment in one structure does not necessarily drive a wholesale loss of mass in one or more organs.     

Radio-transmitted electromyogram signals as indicators of physical activity in Atlantic salmon

Surgical methods developed to implant EMG (electromyogram) transmitters in Atlantic salmon Salmo salar were tested to calibrate electromyograms from axial red musculature to swimming speed in a swim speed chamber, and to compare electromyograms of fish from two stocks (Lone and Imsa). Ten Lone and eight Imsa salmon were equipped with internal EMG transmitters. Surgical procedures were acceptable, with 100% survival of all implanted fish during the study. It was possible to calibrate EMG pulse intervals to swimming speed in 14 of the 18 salmon run in the swim speed chamber ( r²= 0·35-0·76 for individuals, 0·63 for pooled data). Individuals differed in their EMG resting levels (EMGs recorded at 0·5 ms⁻¹), and so higher correlations were obtained between swimming speed and an activity index (EMG pulse intervals at different speeds/EMG resting levels) (pooled data, r² =0·75). The linear relationship between swimming speed and EMG pulse intervals differed significantly between the two stocks ( P <0·05). This successful calibration of EMGs to swimming speed opens the possibility of calibrating EMGs to oxygen consumption and the measurement of the metabolic costs of activity in field experiments.     

力竭性游泳对大鼠睾丸金属结合蛋白的诱导及其与睾酮和锌的关系

本研究通过观察大鼠力竭性游泳后睾丸金属结合蛋白（ＴＭＢＰ）、睾酮和锌含量的动态变化,探讨ＴＭＢＰ的被诱导性、诱导特点以及与睾酮合成和锌代谢的关系。结果显示：大鼠力竭性游泳后,ＴＭＢＰ呈一过性升高,峰值在游泳后６ｈ处,达安静时的１６倍;游后１２ｈ已降回原有水平。这表明ＴＭＢＰ可被力竭性游泳所诱导,半减期不到６ｈ。ＴＭＢＰ诱导性的发现对认识ＴＭＢＰ的功能具有重要的意义。大鼠睾丸睾酮在力竭性游泳后即刻急剧下降,以后逐渐恢复。此恢复过程伴有ＴＭＢＰ的升高。考虑睾酮合成中对锌的高度依赖性以及ＴＭＢＰ结合锌的功能,ＴＭＢＰ很可能在睾酮的合成中参与锌的摄取、转运和供给过程。大鼠ＴＭＢＰ在力竭性游泳后６ｈ处于高峰时,血清锌却处在低谷,这说明ＴＭＢＰ很可能从血清中摄取锌离子,参与应激后锌的再分配活动。     

Measuring Ucrit and endurance: equipment choice influences estimates of fish swimming performance

This study compared the critical swimming speed (U_crit) and endurance performance of three Australian freshwater fish species in different swim‐test apparatus. Estimates of U_crit measured in a large recirculating flume were greater for all species compared with estimates from a smaller model of the same recirculating flume. Large differences were also observed for estimates of endurance swimming performance between these recirculating flumes and a free‐surface swim tunnel. Differences in estimates of performance may be attributable to variation in flow conditions within different types of swim chambers. Variation in estimates of swimming performance between different types of flumes complicates the application of laboratory‐based measures to the design of fish passage infrastructure.     

Effects of telemetry transmitters on swimming performance of adult Atlantic salmon

Swimming performance and blood physiology of adult Atlantic salmon (1021–2338 g, total body length 45–59 cm) were not affected when equipped with external (two sizes) or body-implanted telemetry transmitters compared with untagged controls.     

Cullin3 deficiency shapes tumor microenvironment and promotes cholangiocarcinoma in liver-specific Smad4/Pten mutant mice

Cholangiocarcinoma (CC), the most lethal type of liver cancer, remains very difficult to treat due to an incomplete understanding of the cancer initiation and progression mechanisms and no effective therapeutic drugs. Thus, identification of genomic drivers and delineation of the underlying mechanisms are urgently needed. Here, we conducted a genome-wide CRISPR-Cas9 screening in liver-specific Smad4/Pten knockout mice (Smad4^co/co;Pten^co/co;Alb-Cre, abbreviated as SPC), and identified 15 putative tumor suppressor genes, including Cullin3 (Cul3), whose deficiency increases protein levels of Nrf2 and Cyclin D1 that accelerate cholangiocytes expansion leading to the initiation of CC. Meanwhile, Cul3 deficiency also increases the secretion of Cxcl9 in stromal cells to attract T cells infiltration, and increases the production of Amphiregulin (Areg) mediated by Nrf2, which paracrinely induces inflammation in the liver, and promotes accumulation of exhausted PD1^high CD8 T cells at the expenses of their cytotoxic activity, allowing CC progression. We demonstrate that the anti-PD1/PD-L1 blockade inhibits CC growth, and the effect is enhanced by combining with sorafenib selected from organoid mediated drug sensitive test. This model makes it possible to further identify more liver cancer suppressors, study molecular mechanisms, and develop effective therapeutic strategies.     

Histology and structural integration of the major morphologies of the Cypriniform Weberian apparatus

The Weberian apparatus, a diagnostic feature of otophysan fishes, is a novel hearing adaptation integrating several developmental and morphological systems (ear-vertebral column-swim bladder). Otophysan fishes are one of the largest and most successful freshwater clades, with over 10,000 species across most continents. The largest otophysan order, Cypriniformes, dominates the freshwaters of Asia, Europe, North America, and Africa. Spanning such a wide variety of environments, the Weberian apparatus undergoes morphological modifications to maintain functionality. Within Cypriniformes, we propose three distinct morphological classes of the Weberian apparatus based on the level of skeletal expansion around the swim bladder: simple (typical of most Cyprinidae), anterior plate (found in families such as Gyrinocheilidae, Catostomidae, and Botiidae), and encapsulated (either single-capsule as found, e.g., in Gobionidae and Cobitidae, or double-capsule as found, e.g., in Nemacheilidae and Balitoridae). Little ontological or comparative data exists regarding the construction or integration of these different morphologies, and less is known about the tissue level integration and variation within these morphologies. We used paraffin histology to document the hard and soft tissue anatomy of the Weberian apparatus in six species representing all morphological classes. We found sites of similarity across the morphologies including size and structure of the saccule, aspects of ossicle ossification, and swim bladder tunica composition, indicating potential sites of developmental and functional constraint. In contrast, we found differences across both auditory and nonauditory features in otic chamber size, ossification within ossicles and other vertebral elements, and composition of ligaments, indicating likely sites of adaptability. Some of these changes are likely evolutionary (taxonomic), but may be influenced by the environmental niche occupied by the clade. These results show a clear need for increased ontological and comparative study of the complete cypriniform Weberian apparatus, particularly histologically, as well as increased auditory studies across morphological types.