Zebrafish cooperate while inspecting predators: experimental evidence for conditional approach

Different fish species employ a conditional approach strategy during predator inspection; the risk of approaching a predator is distributed across all inspectors, but is not shared with the animals which keep its distance. Zebrafish, a highly social fish, is increasingly being used in behavioural neuroscience, but it is not known whether it displays conditional approach. In the predator inspection task, animals are observed in a tank with a refuge in one extremity, and an animated image of a predator in the other extremity, with a mirror positioned in parallel to the tank, simulating a perfectly reciprocating conspecific. In Experiment 1, animals spent more time in an inspection zone when the image was turned on, but also displayed more erratic swimming, suggesting cooperation under fear. In Experiment 2, animals spent more time inspecting predators when the mirror was parallel to the tank ("cooperating mirror") than when the mirror was in an angle ("defecting mirror"), suggesting retaliatory behaviour; in both conditions, animals displayed more freezing and erratic swimming. In Experiment 3, no changes in behaviour were observed, regardless of mirror position, when the image was turned off, suggesting that the choice of specific zones in Experiment 2 was not due to shoaling tendencies. These results suggest that predator inspection is associated with conditional approach, while at the same time inducing fear-like behaviour in the animal.

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How do memory modules differentially contribute to familiarity and recollection?

Behavioral and Brain Sciences ◽

10.1017/s0140525x19001833 ◽

2019 ◽

Vol 42 ◽

Author(s):

Olya Hakobyan ◽

Sen Cheng

Keyword(s):

Recognition Memory ◽

Experimental Evidence ◽

Subjective Experience ◽

Target Article ◽

Memory Modules ◽

Familiarity And Recollection ◽

Memory Contents

Abstract We fully support dissociating the subjective experience from the memory contents in recognition memory, as Bastin et al. posit in the target article. However, having two generic memory modules with qualitatively different functions is not mandatory and is in fact inconsistent with experimental evidence. We propose that quantitative differences in the properties of the memory modules can account for the apparent dissociation of recollection and familiarity along anatomical lines.

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Redox Reactions in Lipid Membranes as a Model for Primordial Energy-Conserving Systems

International Astronomical Union Colloquium ◽

10.1017/s0252921100014950 ◽

1997 ◽

Vol 161 ◽

pp. 437-442

Author(s):

Salvatore Di Bernardo ◽

Romana Fato ◽

Giorgio Lenaz

Keyword(s):

Experimental Evidence ◽

Lipid Membranes ◽

Energy Supply ◽

Redox Reactions ◽

Living Systems ◽

Asymmetric Distribution ◽

Conservation Of Energy ◽

Asymmetrical Distribution ◽

Energy Conserving ◽

Living Organisms

AbstractOne of the peculiar aspects of living systems is the production and conservation of energy. This aspect is provided by specialized organelles, such as the mitochondria and chloroplasts, in developed living organisms. In primordial systems lacking specialized enzymatic complexes the energy supply was probably bound to the generation and maintenance of an asymmetric distribution of charged molecules in compartmentalized systems. On the basis of experimental evidence, we suggest that lipophilic quinones were involved in the generation of this asymmetrical distribution of charges through vectorial redox reactions across lipid membranes.

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A Method for Setting the Clearance Angle

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100095200 ◽

1972 ◽

Vol 30 ◽

pp. 388-389

Author(s):

Michael T. Bucek ◽

Howard J. Arnott

Keyword(s):

Experimental Evidence ◽

Light Source ◽

Black Spot ◽

Critical Factor ◽

Clearance Angle ◽

Crude Approximation ◽

Ultrathin Sections

It is believed by the authors, with supporting experimental evidence, that as little as 0.5°, or less, knife clearance angle may be a critical factor in obtaining optimum quality ultrathin sections. The degree increments located on the knife holder provides the investigator with only a crude approximation of the angle at which the holder is set. With the increments displayed on the holder one cannot set the clearance angle precisely and reproducibly. The ability to routinely set this angle precisely and without difficulty would obviously be of great assistance to the operator. A device has been contrived to aid the investigator in precisely setting the clearance angle. This device is relatively simple and is easily constructed. It consists of a light source and an optically flat, front surfaced mirror with a minute black spot in the center. The mirror is affixed to the knife by placing it permanently on top of the knife holder.

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Introductory Remarks

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s1431927600002646 ◽

1980 ◽

Vol 38 ◽

pp. 598-599

Author(s):

H. Mohri

Keyword(s):

Muscle Contraction ◽

Experimental Evidence ◽

Sea Urchin ◽

Constant Length ◽

Thin Filaments ◽

Bridge Formation ◽

Thick Filaments ◽

Sliding Mechanism ◽

Radial Spokes ◽

Cilia And Flagella

In 1959, Afzelius observed the presence of two rows of arms projecting from each outer doublet microtubule of the so-called 9 + 2 pattern of cilia and flagella, and suggested a possibility that the outer doublet microtubules slide with respect to each other with the aid of these arms during ciliary and flagellar movement. The identification of the arms as an ATPase, dynein, by Gibbons (1963)strengthened this hypothesis, since the ATPase-bearing heads of myosin molecules projecting from the thick filaments pull the thin filaments by cross-bridge formation during muscle contraction. The first experimental evidence for the sliding mechanism in cilia and flagella was obtained by examining the tip patterns of molluscan gill cilia by Satir (1965) who observed constant length of the microtubules during ciliary bending. Further evidence for the sliding-tubule mechanism was given by Summers and Gibbons (1971), using trypsin-treated axonemal fragments of sea urchin spermatozoa. Upon the addition of ATP, the outer doublets telescoped out from these fragments and the total length reached up to seven or more times that of the original fragment. Thus, the arms on a certain doublet microtubule can walk along the adjacent doublet when the doublet microtubules are disconnected by digestion of the interdoublet links which connect them with each other, or the radial spokes which connect them with the central pair-central sheath complex as illustrated in Fig. 1. On the basis of these pioneer works, the sliding-tubule mechanism has been established as one of the basic mechanisms for ciliary and flagellar movement.

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