趋流行为下斑马鱼幼鱼的全脑成像

目的 趋流,意即在水中调整身体方向并逆流而上的能力,是一种在大多数鱼类与两栖类动物中存在的保守行为。虽然关于趋流的研究已有一段很长的历史,并且近年来斑马鱼幼鱼趋流行为的理论机制也被提出,但是分布式的神经环路是如何整合多感知信息、做出决策、并实现行为控制仍然是个未知数。对自由运动的斑马鱼进行全脑神经活动成像为理解这一困难的问题提供了特殊的机会。方法 本文开发了一种微流控装置精确控制环境水流并激发斑马鱼的趋流行为。将该微流控芯片与扩增视野光场显微镜以及追踪系统整合,从而记录自由行为下斑马鱼全脑的神经活动。结果 在整合的微流控装置中稳定观察到了斑马鱼在水流中保持自身位置不变、逆流而上等刻板的趋流行为现象。与此同时,实现了对斑马鱼幼鱼趋流行为过程中的全脑钙活动记录。本文初步发现了几个脑区的神经活动与趋流行为相关。结论 本研究第一次展示了在斑马鱼幼鱼趋流行为的同时记录全脑神经活动的技术。接下来对神经活动和行为数据的分析与建模将有助于更好地理解一种重要自然行为背后的感觉运动转换机制。     

Zebrafish “personality” influences sensitivity to magnetic fields

How animals integrate different sensory information for orientation is a complex process involving interactions between a variety of internal and external factors. Due to this complexity, each component of a suite of factors is typically studied in isolation. Here, we examine how an internal factor (personality of fish) influences the response of zebrafish (Danio rerio) to the magnetic field, while swimming in a flow chamber. Our previous work demonstrated that the orientation to the water current (rheotaxis) of zebrafish individuals is influenced by variations of the magnetic field only when fish are part of a shoal. In this study, we evaluated the rheotactic behavior of 20 fish, grouped in shoals of “proactive” or “reactive” individuals, under magnetic fields of different directions. We found that the magnetic field influenced at which water speed rheotaxis was elicited in zebrafish with “reactive” personality, but not in those with “proactive” personality. These results suggest that fish personality influences response to or weighing of sensory inputs and provides some insight on the variation in behavioral responses to environmental stimuli in both laboratory and natural settings.     

Numerical calculation and measurement of 60-Hz current densities induced in an upright grounded cylinder

Power-frequency electric fields are strongly perturbed in the vicinity of human beings and experimental animals. As a consequence, the extrapolation of biological data from laboratory animals to human-exposure situations cannot use the unperturbed exposure field strength as a common exposure parameter. Rather, comparisons between species must be based on the actual electric fields at the outer surfaces of and inside the bodies of the subjects. Experimental data have been published on surface and internal fields for a few exposure situations, but it is not feasible to characterize experimentally more than a small fraction of the diverse types of exposures which occur in the laboratory and in the field. A predictive numerical model is needed, one whose predictions have been verified in situations where experimental data are available, and one whose results can be used with confidence in new exposure situations. This paper describes a numerical technique which can be used to develop such a model, and it carries out this development for a test case, that of a homogeneous right-circular cylinder resting upright on-end on a ground plane and exposed to a vertical, uniform, 60-Hz electric field. The accuracy of the model is tested by comparing short-circuit currents and induced current densities predicted by it to measured values: Agreement is good.     

Resisting flow–laboratory study of rheotaxis of the estuarine copepod Pseudodiaptomus annandalei

Rheotaxis is a ubiquitous phenomenon among aquatic animals and thought to be an adaptation to maintain populations in flowing waters. While many estuarine copepods can retain their populations in estuaries with net seaward flow, rheotaxis of individual copepods has not been reported before. In this study, the behavior of a calanoid copepod Pseudodiaptomus annandalei in flow was examined in a recirculating laboratory flume. This estuarine copepod displayed different responses to ambient flow fields while swimming in the water column or attaching to the flume bed (walls). Copepods in the water column showed vigorous countercurrent swimming by occasional bounding when flow velocity was increased up to 2.1 cm s^?1, but none of the individuals in the water column were retained in the flume when flow speeds were higher than 4 cm s^?1. This indicates P. annandalei profits little from rheotaxis to withstand flow when they were swimming in the water column. Instead, more individuals attempted sinking downwards to the slow flow region near the flume bed (walls) and showed active substrate attachment to avoid being flushed out by the high-velocity channel flow. The results suggest that P. annandalei benefits from rheotaxis and association with the substrate which allows them to hold position well at ambient flow velocities up to 3 cm s^?1. These adaptive responses might be important for population maintenance.     

Rheotaxis In Uronychia Setigera (Ciliata, Hypotrichida)

ABSTRACT. The behavior of populations of Uronychia setigera (Ciliata, Hypotrichida) exposed to water currents flowing at increasing velocities (300, 400, 500, 900, 1,700 μm/s) was analyzed using two techniques: 1) the ethogram and 2) the numerical indices recently proposed to measure the development in space and time of tracks of ciliates. Beyond a certain threshold value of the water velocity (˜ 300 μm/s), this species shows a definite positive rheotaxis, only if it moves in a more or less direct contact with the substrate. No rheotactic swimming ever occurs. Rheotaxis is a gradual, adaptive behavior: the higher the velocity of the current, the stronger the degree of the rheotactic response, as demonstrated by the increasing significance of the polar distribution of the tracks. Beyond 500 μm/s the water flow is so strong that it affects the locomotion of U. setigera continuously and strongly inducing this species to perform a new behavioral pattern, the Fast Backward Bidimensional Swimming. Under stressing water currents it reacts at first by creeping along straighter trajectories and then with faster locomotion, in such a way that its reaction is to a certain extent proportional to the drag of the currents. the rheotaxis of U. setigera is discussed as an adaptive response.     

Rheotaxis in larval zebrafish is mediated by lateral line mechanosensory hair cells

The lateral line sensory system, found in fish and amphibians, is used in prey detection, predator avoidance and schooling behavior. This system includes cell clusters, called superficial neuromasts, located on the surface of head and trunk of developing larvae. Mechanosensory hair cells in the center of each neuromast respond to disturbances in the water and convey information to the brain via the lateral line ganglia. The convenient location of mechanosensory hair cells on the body surface has made the lateral line a valuable system in which to study hair cell damage and regeneration. One way to measure hair cell survival and recovery is to assay behaviors that depend on their function. We built a system in which orientation against constant water flow, positive rheotaxis, can be quantitatively assessed. We found that zebrafish larvae perform positive rheotaxis and that, similar to adult fish, larvae use both visual and lateral line input to perform this behavior. Disruption or damage of hair cells in the absence of vision leads to a marked decrease in rheotaxis that recovers upon hair cell repair or regeneration.     

Swimming activity and behaviour of European Anguilla anguilla glass eels in response to photoperiod and flow reversal and the role of energy status

To better understand migratory divergences among Anguilla anguilla glass eels, the behaviour of individuals caught at the time of their estuary entrance was studied through their response to a light:dark cycle and then to both water current reversal and light:dark cycle. In a first experiment, fish moving with the flow in response to dusk (M⁺ fish) and fish that had not exhibited any movement (M⁻ fish) were distinguished. Anguilla anguilla from these two groups were then individually marked and their response to water current reversal compared. M⁺ individuals mainly exhibited negative rheotaxis with a tidal periodicity, whereas positive rheotaxis was mainly exhibited by M⁻ individuals. Thus, M⁺ A. anguilla glass eels showing negative rheotaxis appear to have the strongest propensity to migrate, the converse applies to M⁻ ones showing positive rheotaxis. A small percentage of individuals (5%) were hyperactive, alternately swimming with and against the current with almost no resting phase. These fish lost c . 2 mg wet mass day⁻¹, whereas individuals which were almost inactive lost c . 1 mg day⁻¹. Wet and dry mass changes in relation to activity levels were compared with previous experiments and it was concluded that A. anguilla glass eel energy status might be involved in differences in migratory tendencies but other factors that might be important are discussed. It is proposed that any decrease in A. anguilla glass eel energy stores associated with global warming might lead to an increase in the proportion of sedentary individuals and thus be involved in the decrease in the recruitment to freshwater habitats.     

水流对草鱼幼鱼趋光行为的影响

为了探讨水流对鱼类趋光性的影响, 利用自制的循环水槽装置, 以草鱼(Ctenpharyngodon idellus)幼鱼为研究对象, 研究其在光照度为300 lx, 不同流速工况(0、0.1和0.2 m/s)下的趋光性行为, 同时设黑暗静水工况为对照组。结果表明: (1) 0.2 m/s的流速可完全激发草鱼幼鱼的趋流性, 使其游泳方向多数与顶流方向呈± 20°。(2)根据草鱼幼鱼在不同流速工况下随光照度衰减在水槽内的分布情况, 计算得其在3种流速工况下的光强期望值分别为: 52.45, 34.62和37.86 lx。(3)当照度为300 lx时, 静水工况下的实验鱼在水槽中呈现“两头高, 中间低”的分布情况, 并未表现出对某一光强范围的偏好行为; 在小于感应值的低流速下, 草鱼幼鱼的分布情况总体趋势与静水工况类似, 但在远离光源处的分布较多, 多呈“逆流后退”行为; 当流速值超过感应流速时, 在趋流性的作用下, 鱼类在尾部的聚集情况明显下降, 同时在水槽中的分布更加均匀, 其原有光环境的作用减弱。研究初步证明了略大于感应值的小流速所引发的草鱼趋流性即可对其光环境响应行为产生影响。     

Biological factors related to learning in the land snail (Helix aspersa Müller)

We have studied vertical progression behaviour in Helix and its modification by the animals' encountering either quinine or water on a thread tied at the top of vertically-placed glass rods. There is both short and long term memory of the aversive (quinine) experience, as well as habituation of climbing in snails encountering an apparently neutral (water) stimulus. Some of the factors which appear to influence climbing latencies and acquisition and retention of the nature of the goal stimulus are: length of laboratory housing, humidity and nutritional and reproductive condition.     

The sensory basis of rheotaxis in the blind Mexican cave fish, Astyanax fasciatus

The sensory basis of rheotaxis (orientation to currents) was investigated in the blind Mexican cave fish, Astyanax fasciatus. An unconditioned rheotactic response to uniform velocity flows was exhibited, with a threshold of less than 3 cm s⁻¹. Disabling the entire lateral line or the superficial neuromast receptor class increased the rheotactic threshold to greater than 9 cm s⁻¹. A pharmacological block of the lateral line canal system alone had no effect. These results demonstrate that the superficial lateral line system controls rheotaxis at low current velocities. The effect of pairing an odor stimulant with the water current dropped the rheotactic threshold to less than 0.4 cm s⁻¹. This study provides a clear behavioral role for the superficial neuromasts where none previously existed, and also establishes a link between the mechanosensory lateral line and olfactory systems in the olfactory search behavior of the cave fish. Accepted: 9 January 1999     

Physicochemical properties of functional surfaces in pitchers of the carnivorous plant Nepenthes alata Blanco (Nepenthaceae)

Pitchers of the carnivorous plant Nepenthes alata are highly specialized organs adapted to attract, capture, and digest animals, mostly insects. They consist of several well distinguishable zones, differing in macro-morphology, surface microstructure, and functions. Since physicochemical properties of these surfaces may influence insect adhesion, we measured contact angles of non-polar (diiodomethane) and polar liquids (water and ethylene glycol) and estimated the free surface energy of 1) the lid, 2) the peristome, 3) the waxy surface of the slippery zone, and 4) the glandular surface of the digestive zone in N. alata pitchers. As a control, the external surface of the pitcher, as well as abaxial and adaxial surfaces of the leaf blade, was measured. Both leaf surfaces, both lid surfaces, and the external pitcher surface showed similar contact angles and had rather high values of surface free energy with relatively high dispersion component. These surfaces are considered to support strong adhesion forces based on the capillary interaction, and by this, to promote successful attachment of insects. The waxy surface is almost unwettable, has extremely low surface energy, and therefore, must essentially decrease insect adhesion. Both the peristome and glandular surfaces are wetted readily with both non-polar and polar liquids and have very high surface energy with a predominating polar component. These properties result in the preclusion of insect adhesion due to the hydrophilic lubricating film covering the surfaces. The obtained results support field observations and laboratory experiments of previous authors that demonstrated the possible role of different pitcher surfaces in insect trapping and retention.     

“Going with the Flow” or Not: Evidence of Positive Rheotaxis in Oceanic Juvenile Loggerhead Turtles (Caretta caretta) in the South Pacific Ocean Using Satellite Tags and Ocean Circulation Data

The movement of juvenile loggerhead turtles (n = 42) out-fitted with satellite tags and released in oceanic waters off New Caledonia was examined and compared with ocean circulation data. Merging of the daily turtle movement data with drifter buoy movements, OSCAR (Ocean Surface Current Analyses - Real time) circulation data, and three different vertical strata (0–5 m, 0–40 m, 0–100 m) of HYCOM (HYbrid Coordinate Ocean Model) circulation data indicated the turtles were swimming against the prevailing current in a statistically significant pattern. This was not an artifact of prevailing directions of current and swimming, nor was it an artifact of frictional slippage. Generalized additive modeling was used to decompose the pattern of swimming into spatial and temporal components. The findings are indicative of a positive rheotaxis whereby an organism is able to detect the current flow and orient itself to swim into the current flow direction or otherwise slow down its movement. Potential mechanisms for the means and adaptive significance of rheotaxis in oceanic juvenile loggerhead turtles are discussed.     

Effects of fluoxetine on growth and behavior in the crayfish Orconectes rusticus

This laboratory study examined the effects of the specific serotonin reuptake inhibitor fluoxetine on growth following molting and on a range of behaviors in the crayfish Orconectes rusticus. For growth experiments, male Form I and Form II crayfish were weighed and measured and placed individually in water containing 0–500 μg/L of fluoxetine. They were held in fluoxetine or control water until they molted and were reweighed two weeks post-molt. In behavior experiments, juvenile and adult animals were held individually in 0, 2, 200, or 500 μg/L of fluoxetine for 10 days and tested in an open field arena to assess locomotion, thigmotaxis, sheltering, and habituation to a novel environment. Under our laboratory conditions, crayfish exposed to fluoxetine at 500 μg/L showed significantly enhanced growth: post-molt Form I animals had greater body weight and post-molt Form II animals had greater carapace length, relative to controls. In open field tests, juvenile crayfish exposed to 2 and 500 μg/L fluoxetine displayed significantly reduced locomotion compared to controls. The results indicate that crayfish growth and locomotion can be manipulated by short-term exposure to ambient fluoxetine, suggesting that this means of exposure may offer a useful and noninvasive way to examine drug effects in freely moving animals. However, effects were only observed at concentrations well above fluoxetine levels currently reported in the environment. This suggests that O. rusticus may be relatively resistant to this form of pharmaceutical pollution but whether effects would occur following long-term exposure to lower concentrations is unknown.     

Decision, sensation, and habituation: a multi-layer dynamic field model for Inhibition of Return

Inhibition of Return (IOR) is one of the most consistent and widely studied effects in experimental psychology. The effect refers to a delayed response to visual stimuli in a cued location after initial priming at that location. This article presents a dynamic field model for IOR. The model describes the evolution of three coupled activation fields. The decision field, inspired by the intermediate layer of the superior colliculus, receives endogenous input and input from a sensory field. The sensory field, inspired by earlier sensory processing, receives exogenous input. Habituation of the sensory field is implemented by a reciprocal coupling with a third field, the habituation field. The model generates IOR because, due to the habituation of the sensory field, the decision field receives a reduced target-induced input in cue-target-compatible situations. The model is consistent with single-unit recordings of neurons of monkeys that perform IOR tasks. Such recordings have revealed that IOR phenomena parallel the activity of neurons in the intermediate layer of the superior colliculus and that neurons in this layer receive reduced input in cue-target-compatible situations. The model is also consistent with behavioral data concerning temporal expectancy effects. In a discussion, the multi-layer dynamic field account of IOR is used to illustrate the broader view that behavior consists of a tuning of the organism to the environment that continuously and concurrently takes place at different spatiotemporal scales.     

Role of chemical and visual cues in food recognition by leatherback posthatchlings (Dermochelys coriacea L)

We raised leatherback posthatchlings in the laboratory for up to 7 weeks to study the role of visual and chemical cues in food recognition and food-seeking behavior. Turtles were reared on a formulated (artificial gelatinous) diet and had no contact with test materials until experiments began. Subjects were presented with visual cues (a plastic jellyfish; white plastic shapes [circle, square, diamond] similar in surface area to the plastic model), chemical cues (homogenates of lion's mane jellyfish, Cyanea capillata; moon jellyfish, Aurelia aurita; and a ctenophore, Ocyropsis sp., introduced through a water filter outflow), and visual and chemical cues presented simultaneously. Visual stimuli evoked an increase in swimming activity, biting, diving, and orientation toward the object. Chemical cues elicited an increase in biting, and orientation into water currents (rheotaxis). When chemical and visual stimuli were combined, turtles ignored currents and oriented toward the visual stimuli. We conclude that both cues are used to search for, and locate, food but that visual cues may be of primary importance. We hypothesize that under natural conditions turtles locate food visually, then, as a consequence of feeding, associate chemical with visual cues. Chemical cues then may function alone as a feeding attractant.     

Researchers' ethical concerns regarding habituating wild-nonhuman primates and perceived ethical duties to their subjects: Results of an online survey

While the process of habituation is essential for researchers to observe primates in their natural habitats, ethical dilemmas may arise from its consequences. We collected data from 286 participants via an online survey to investigate: (a) how primatologists perceive their ethical duties toward their subjects; (b) the extent to which primatologists are concerned about the potential ethical consequences of habituation; and (c) the methods primatologists use to reduce potential harms caused by habituation. Overall, primatologists felt an extremely strong duty to mitigate harms that they may cause (e.g., to not stress individuals during observation, treat injuries, and reunite separated individuals) and expressed very high concern for habituation's potential to increase the vulnerability of their subjects to poaching and disease transfer. Ratings for those items were so high that they could not be included in subsequent exploratory factor analyses that were designed to reveal constructs underlying respondents’ ratings of their ethical duties and concerns. Factor analysis of ratings of ethical duties revealed that primatologists reported a strong duty to mitigate harms caused by other humans and a lower perceived duty to mitigate naturally occurring harmful events. Factor analysis on ethical concern ratings revealed that respondents were concerned about harms during the habituation process, the presence of unhabituated behavior after habituation had been established, and indirect harms of habituation. Concerns for unhabituated behavior and indirect harms were rated slightly higher than concern for harms during the habituation process. To mitigate potential harms, primatologists primarily reported engaging in strategies to reduce stress in their subjects. Our findings reveal a disconnect between primatologists' ratings of their ethical concerns and their reported mitigation practices that may, in part, stem from gaps in knowledge about the true impacts of habituation. We suggest areas of discussion and research in the field necessary to address those gaps.     

Individual patterns of rhythmic swimming activity in Anguilla anguilla glass eels synchronised to water current reversal

The existence of distinct patterns of activity and swimming behaviour were tested in individual European glass eels by means of Bayesian inference mixture modelling. 36 glass eels were tagged using Visible Implant Elastomer and added to 36 untagged glass eels in February and April. Each group was presented with a change in water current direction every 6,2 h and videotaped during 2 weeks. Two hypotheses were tested: (i) all individuals display a similar pattern of behaviour within a tidal period, glass eels showing both positive and negative rheotaxis in opposite phase (M1 model) and (ii) individuals are distributed in two different groups, some glass eels swimming with and the others against the current (M2 model). Results showed that most glass eels displayed a positive or a negative rheotaxis and only a small number exhibited both behaviours. All swimming behaviours were synchronised to a change in current direction with a period close to the tidal one. Results are discussed in relation to synchronisation and migration behaviour.     

Experimental investigations of diel vertical movements by lotic mayflies over substrate surfaces

SUMMARY. 1. The vertical distribution within the substrate of three lotic mayflies (Rhithrogena sp., Paraleptophlebia sp. and Baetis tricaudalus Dodds) was examined in laboratory streams to determine if diel patterns of vertical movement across substrate surfaces existed and whether light intensity, temperature, substrate composition or food availability influenced the observed movement patterns.
2. Rhithrogena sp. and B. tricaudatus exhibited significant diel movement from lower substrate surfaces during the day to upper surfaces at night, although >64% of B. tricaudalus occupied the upper surfaces throughout the 24 h period. In contrast, Parakplophlebia sp. larvae did not change their vertical distribution over the 24 h period.
3. The proportion of mayflies occupying substrate surfaces was influenced by the amount of upper and lower surface area available in the substrate and, possibly, crevice sizes associated with lower surfaces.
4. The movement of Rhiihrogena sp. from lower surfaces during the day to the upper surfaces during the night was influenced by changes in light intensity, but not by changes in food availability or water temperature.
5. The diel patterns of vertical movement exhibited by lotic mayflies in this investigation raise the possibility that at least some biotic interactions may vary over a diel cycle. These could include competitive interactions or temporal cycling of prey availability to predators.     

Experiments on orientation of the intertidal barnacle Tesseropora rosea (Krauss)

The intertidal barnacle Tesseropora rosea (Krauss) exhibits very marked directionality of orientation on sloping and vertical surfaces. The barnacles are orientated so that their cirral fans face the water current; this pattern was found within 1 wk after settlement. Adults also showed similar orientation to the water current at each site.Three manipulative experiments were done in the field to determine the consequences of incorrect orientation by the barnacles. Correct orientation was necessary for T. rosea to maintain its tissue weight, but experimental rotation of barnacles through 90° or 180° made no difference to rates of shell growth, mortality or weight of egg masses. Furthermore, this species was unable to re-orientate once it had metamorphosed, and orientation of newly-settled barnacles was not influenced by that of adults.