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Archaeocyaths are a group of extinct filter feeders that flourished in the early Cambrian period and occupied an important position in the evolution of basal fauna and the early marine ecosystem. However, the detailed morphological and anatomical information of this group are still unclear due to insufficient fossil material and limited experimental analyses. Here, we report exquisitely preserved phosphatized archaeocyathan fossil cups, ca. 515 million years old, from the top of the Shuijingtuo Formation (Series 2, Stage 3) and the Xiannüdong Formation (Series 2, Stage 3) of the Yangtze Platform, South China. Detailed observation of their external morphology via scanning electron microscopy (SEM) and micro-computed tomography (Micro-CT) analysis revealed detailed information of their internal structure. They have a typical double-walled cup, with the perforated inner and outer walls concentrically distributed, but the structure between the two walls differs. The inverted cone-shaped cups have radially distributed septa between the walls. Perforated septa connect the two walls. The low and columnar cups have canals between the two walls, forming the network. These pores and cavities constitute an important component of the water current system (pumping and filtering water with a network of canals and chambers) and influence the process of filtration in the cup. In comparison to traditional thin-section analysis, the combination of SEM and Micro-CT analysis on phosphatized archaeocyaths presented in this study further explored the detailed internal structure and finely reconstructed the microscopic overall morphology and anatomy, which provide important information to help us understand the systematic taxonomy, anatomy, and morphology of archaeocyaths during the Cambrian period.

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In this study, we investigated the effects of swimming activity and feed restriction on juvenile rainbow trout (Oncorhynchus mykiss) in decoupled aquaponic systems. Our focus was on assessing their impact on water quality parameters within the aquaponic setup and evaluating the growth performance of the fish, including final weight (FW), condition factor (K), coefficient of variation (c.v.) in weight, specific growth rate (SGR), total feed intake (g/fish), feed conversion rate (FCR), hepatosomatic index (HSI), and viscerosomatic index (VSI), as well as the growth of lettuce (Lactuca sativa L. var. elmaria). The study involved 108 juvenile rainbow trout with an average initial weight of 26.54 ± 0.36 g and 60 ten-day-old lettuce seedlings, over a period of 42 days. We designed four treatment groups, each with three fish tanks: static ad libitum (SA), where fish were in static water conditions and fed to satiation; static restriction (SR), with fish in static water and a 25% feed restriction; current ad libitum (CA), where fish experienced forced swimming at 1 BL s-1; and current restriction (CR), with swimming exercise at 1 BL s-1 and a 25% feed restriction. Using a flow rate of 1 BL s-1 in the tanks for rainbow trout yielded several benefits. Notably, the fish in the CA group exhibited increased feed intake (60 ± 1.78 g fish-1) and enhanced fish growth with an FW of 91.72 ± 0.91 g, compared to the SA group (55.88 ± 0.88 g fish-1 for feed intake and 89.26 ± 0.81 g for FW). In contrast, the CR group showed a reduced feed intake (39.02 ± 2.78 g fish-1) and a lower FW (67.85 ± 1.49 g) compared to the CA group. In addition, the CA group demonstrated positive contributions to fish development with a reduced HSI (1.26 ± 0.02) in comparison to the SA group (1.56 ± 0.14). Inadequate nutrient provisioning in the SR and CR groups negatively impacted fish growth and system efficiency. Our findings suggest that optimizing water flow and feed benefits fish and plants and enhances system sustainability.

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Water-current energy is an enormous and widely distributed clean energy in nature, with different scales from large ocean flow to small local turbulence. However, few effective technologies have been proposed to make use of different forms of water currents as a power source. Here, high-performance paired triboelectric nanogenerators (P-TENGs) capable of integrating massively into a thin flexible layer as a structured triboelectric surface (STS) are demonstrated for harvesting water-current energy. Novel gas packet exchange structure and rigid-flexible coupling deformation mechanism are introduced to ensure that the device can work very effectively even in deep water under high water pressure. The rationally designed TENG array in the STS enables highly efficient power take-off from the flow. Typically, the STS demonstrates a high-frequency output up to 57 Hz, largely superior to current TENG devices, and the power density is improved by over 100 times for triboelectric devices harvesting current energy. The flexible STS is capable of attaching to various surfaces or applying independently for self-powered sensing and underwater power supply, showing great potential for water-current energy utilization. Moreover, the work also initiates universal strategies to fabricate high-frequency devices under large environment pressure, which may profoundly enrich the design of TENGs.

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Measuring water currents in natural waters is limited by the cost of sensors. Standard sonar-based acoustic current Doppler profilers (ADCPs) are high cost, about $10-20 K per unit. Tilt current meters (TCMs) are much cheaper. They consist of a bottom-mounted subsurface float equipped with an inertial measurement unit (IMU) and data center that records the float's motion and attitude as a time series. The flow speed is measured by calculating the tilt angle of the float in response to the current. However, tilt-based measurements require the float system to be carefully engineered and its physical response optimized for good results. Even so, high-frequency flow-induced vibrations often dominate the motion and must be averaged and filtered out of the data and discarded. This represents the loss of potentially valuable information, but decoding the high-frequency components for such useful data is difficult. These experiments explored using an artificial neural network (ANN) approach to extract the ambient water current speed from that high-frequency data alone, after the displacement information was filtered out. The methods were informed by the ANN designs and data augmentation techniques used by neurologists to observe the tremors and other motions exhibited by patients experiencing symptoms of Parkinson's disease. Once the model was trained using carefully selected training and validation sets to prevent overfitting, the results of evaluating previously unseen data by the model are clear and promising. Water current speed was accurately calculated from the high-frequency components of the motion sensor data and agreed with corresponding current speeds measured by established methods. This novel approach could facilitate new sensor system designs that can be empirically or self-calibrated more efficiently and have a lower barrier to application than those currently available.

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The virulent nature of many suddenly evolved highly contagious pathogens is controlled by surroundings' environment and also by the population density in a particular biogeographical region. Worldwide, the white spot disease (WSD) caused by the contagious white spot syndrome virus (WSSV) has devastated the aquaculture of penaeid shrimp species. WSSV is a highly infectious waterborne pathogen. The black tiger shrimp or Penaeus monodon had developed resistance potential against WSD with no antibody-mediated immunity. Many environmental factors including oceanic water current often play a major role in the nourishment as well as species richness of indigenous marine species. Here, we reported that oceanic water current might influence the disease-resistance prevalence in P. monodon.

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The primary function of the gastropod shell is protection. However, shells that function well in one environment may be maladaptive in another. Upon infection, the snail shell protects internal parasites and it is to the parasite's advantage to optimize, or not interfere with, shell functionality. However, parasites, particularly trematodes, are often pathogenic and it is not clear if parasitism will induce environment-dependent or -independent changes to gastropod shells. We conducted a field study and a complementary laboratory experiment to examine the effects of trematode parasitism on shell characteristics (shape, size, and crush resistance) of Physa acuta snails in flow and nonflow environments using geometric morphometrics and crush assays. Field results indicate wetland (nonflow) snails had large, crush resistant shells with narrow apertures and tall spires. In contrast, stream (flow) snails had small, weak shells with wide apertures and short spires. Parasitism had no apparent effect on the crush resistance of wetland snails but significantly reduced the crush resistance of stream snails. Parasitism had no significant effect on overall shell shape in stream or wetland snails. Similar to the results of our field study, nonflow tank snails had significantly more crush resistant shells than flow tank snails. Additionally, the shapes of flow and nonflow tank snails significantly differed where nonflow tank snails resembled wetland snails and flow tank snails resembled stream snails. For laboratory snails, parasitism reduced crush resistance regardless of flow/nonflow treatment. Our results demonstrate that habitat and/or flow treatment was the primary factor affecting P. acuta shell morphology and that trematode parasitism played a secondary role.

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In this paper, the overall morphological differences between populations of Simulium subpallidum Lutz, 1909 are studied. Several studies found in the literature point to a relationship between the labral fans and body size and the habitat where blackfly larvae occur. However, other characteristics potentially related to the microhabitat, such as abdominal hook circlet morphology, which is used for larvae to fix themselves in the substratum, and thoracic prolegs morphology, which help larvae move in the substratum, were analyzed in three different populations of S. subpallidum, one of which occupied a faster flow. The results suggest phenotypic plasticity in S. subpallidum and a tendency toward larger structures in faster flows.

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Sustained swimming at moderate speeds is considered beneficial in terms of the productive performance of salmonids, but the causative mechanisms have yet to be unequivocally established. In the present study, the effects of moderate exercise on the bioenergetics of rainbow trout were assessed during a 15 week growth experiment, in which fish were reared at three different current speeds: 1 BL s(-1), 0.5 BL s(-1) and still water (≈ 0 BL s(-1)). Randomly selected groups of 100 fish were distributed among twelve 600 L tanks and maintained on a restricted diet regime. Specific growth rate (SGR) and feed conversion ratio (FCR) were calculated from weight and length measurements every 3 weeks. Routine metabolic rate (RMR) was measured every hour as rate of oxygen consumption in the tanks, and was positively correlated with swimming speed. Total ammonia nitrogen (TAN) excretion rates showed a tendency to decrease with increasing swimming speeds, yet neither they nor the resulting nitrogen quotients (NQ) indicated that swimming significantly reduced the fraction of dietary protein used to fuel metabolism. Energetic budgets revealed a positive correlation between energy expenditure and the current speed at which fish were reared, fish that were forced to swim and were fed restrictively consequentially had poorer growth and feed utilization. The results show that for rainbow trout, water current can negatively affect growth despite promoting minor positive changes in substrate utilization. We hypothesize that this may be the result of either a limited dietary energy supply from diet restriction being insufficient for both covering the extra costs of swimming and supporting enhanced growth.

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We describe the abiotic factors affecting the distribution of black flies at a microhabitat scale, rather than at the regional scale usually present in the literature on the Neotropics. Black fly larvae were sampled from the Tocantins River and three tributaries, located in the Brazilian savanna (state of Tocantins, Brazil) during six bi-monthly sampling periods from October 2004-August 2005. At each sampling site, 15 random quadrats (30 x 30 cm) were sampled each period and for each quadrat were determined mean water velocity, predominant substrate type (rocks, riffle litter or riparian vegetation) and depth detrended correspondence analysis (DCA) was used to determine associations with current velocity, whereas correspondence analysis (CA) was used to estimate site specific current velocity associations. Canonical correspondence analysis (CCA) was used to identify general microhabitat associations. The CCA showed that most species had a trend towards riffle litter, except for Simulium nigrimanum associated with rocky substrate and Simulium cuasiexiguum associated with riparian vegetation. The DCA showed a well defined pattern of water velocity associations. The CA revealed that the species showed different speed associations from one site to another, suggesting different competitive pressures resulting in the occurrence of different realized niches.

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