The dynamics of pattern matching in camouflaging cuttlefish

Many cephalopods escape detection using camouflage. This behaviour relies on a visual assessment of the surroundings, on an interpretation of visual-texture statistics and on matching these statistics using millions of skin chromatophores that are controlled by motoneurons located in the brain. Analysis of cuttlefish images proposed that camouflage patterns are low dimensional and categorizable into three pattern classes, built from a small repertoire of components. Behavioural experiments also indicated that, although camouflage requires vision, its execution does not require feedback, suggesting that motion within skin-pattern space is stereotyped and lacks the possibility of correction. Here, using quantitative methods, we studied camouflage in the cuttlefish Sepia officinalis as behavioural motion towards background matching in skin-pattern space. An analysis of hundreds of thousands of images over natural and artificial backgrounds revealed that the space of skin patterns is high-dimensional and that pattern matching is not stereotyped-each search meanders through skin-pattern space, decelerating and accelerating repeatedly before stabilizing. Chromatophores could be grouped into pattern components on the basis of their covariation during camouflaging. These components varied in shapes and sizes, and overlay one another. However, their identities varied even across transitions between identical skin-pattern pairs, indicating flexibility of implementation and absence of stereotypy. Components could also be differentiated by their sensitivity to spatial frequency. Finally, we compared camouflage to blanching, a skin-lightening reaction to threatening stimuli. Pattern motion during blanching was direct and fast, consistent with open-loop motion in low-dimensional pattern space, in contrast to that observed during camouflage.journal articl

The dynamics of pattern matching in camouflaging cuttlefish

Many cephalopods escape detection using camouflage. This behaviour relies on a visual assessment of the surroundings, on an interpretation of visual-texture statistics and on matching these statistics using millions of skin chromatophores that are controlled by motoneurons located in the brain. Analysis of cuttlefish images proposed that camouflage patterns are low dimensional and categorizable into three pattern classes, built from a small repertoire of components. Behavioural experiments also indicated that, although camouflage requires vision, its execution does not require feedback, suggesting that motion within skin-pattern space is stereotyped and lacks the possibility of correction. Here, using quantitative methods, we studied camouflage in the cuttlefish Sepia officinalis as behavioural motion towards background matching in skin-pattern space. An analysis of hundreds of thousands of images over natural and artificial backgrounds revealed that the space of skin patterns is high-dimensional and that pattern matching is not stereotyped-each search meanders through skin-pattern space, decelerating and accelerating repeatedly before stabilizing. Chromatophores could be grouped into pattern components on the basis of their covariation during camouflaging. These components varied in shapes and sizes, and overlay one another. However, their identities varied even across transitions between identical skin-pattern pairs, indicating flexibility of implementation and absence of stereotypy. Components could also be differentiated by their sensitivity to spatial frequency. Finally, we compared camouflage to blanching, a skin-lightening reaction to threatening stimuli. Pattern motion during blanching was direct and fast, consistent with open-loop motion in low-dimensional pattern space, in contrast to that observed during camouflage

Plasma Membrane Mechanical Stress Activates TRPC5 Channels

<div><p>Mechanical forces exerted on cells impose stress on the plasma membrane. Cells sense this stress and elicit a mechanoelectric transduction cascade that initiates compensatory mechanisms. Mechanosensitive ion channels in the plasma membrane are responsible for transducing the mechanical signals to electrical signals. However, the mechanisms underlying channel activation in response to mechanical stress remain incompletely understood. Transient Receptor Potential (TRP) channels serve essential functions in several sensory modalities. These channels can also participate in mechanotransduction by either being autonomously sensitive to mechanical perturbation or by coupling to other mechanosensory components of the cell. Here, we investigated the response of a TRP family member, TRPC5, to mechanical stress. Hypoosmolarity triggers Ca²⁺ influx and cationic conductance through TRPC5. Importantly, for the first time we were able to record the stretch-activated TRPC5 current at single-channel level. The activation threshold for TRPC5 was found to be 240 mOsm for hypoosmotic stress and between −20 and −40 mmHg for pressure applied to membrane patch. In addition, we found that disruption of actin filaments suppresses TRPC5 response to hypoosmotic stress and patch pipette pressure, but does not prevent the activation of TRPC5 by stretch-independent mechanisms, indicating that actin cytoskeleton is an essential transduction component that confers mechanosensitivity to TRPC5. In summary, our findings establish that TRPC5 can be activated at the single-channel level when mechanical stress on the cell reaches a certain threshold.</p></div

Pipette pressure activates TRPC5 on single-channel membrane patch.

<p>(A) schematic diagram depicting single-channel current measurement in TRPC5-expressing CHO-K1 cells. Membrane stretch was elicited by applying suction through the patch pipette, as indicated by <i>red arrow</i>. (B) a representative cell-attached recording (n = 11) of TRPC5-expressing CHO-K1 cell showing changes in channel activity when -40 mmHg pipette pressure was applied (<i>suction</i>) and subsequently released (<i>release</i>). The pipette holding potential was -60 mV. (C) representative traces showing single-channel activities in vector transfected (<i>Vector</i>) and TRPC5-expressing (<i>TRPC5</i>) CHO-K1 cells at 0 mmHg and -40 mmHg pipette pressure with cell-attached configuration. Channel activities were also recorded in TRPC5-expressing cells pretreated with 10 μM BAPTA-AM to buffer cytosolic Ca²⁺ fluctuation (<i>TRPC5+BAPTA-AM</i>). The pipette holding potentials were -60 mV. (D) channel open probability (NPo) values over time for the stretch-activated channel under <i>0 mmHg</i> and <i>-40 mmHg</i>. Shown are analyses from the same cell-attached patch applied with the indicated pipette pressures for 90 seconds. (E) quantification of the single-channel open probabilities (NPo) of the channel activities recorded on TRPC5-expressing CHO-K1 cells as in (C). (F) single-channel <i>I-V</i> relationships of the stretch-activated channels in cell-attached configuration. The bath solution was 130 mM K⁺ solution (<i>High K</i>^<i>+</i>, <i>red circle</i>) for dissipating the membrane potential. The slope conductance is 39 ± 2 pS. (G) schematic diagram showing the two-step backfilling protocol. Patch pipettes were backfilled with T5E3 (15 μg/ml) using a two-step protocol. T5E3 eventually diffused to pipette tip to inhibit TRPC5. Only the patched membrane is depicted for simplicity. Recordings were performed with cell-attached configuration. (H) representative traces showing the stretch (-40 mmHg)-activated channel in the presence of preimmune IgG (15 μg/ml) or T5E3 (15 μg/ml) immediately (<i>0 min</i>) and 10 minutes (<i>10 min</i>) after gigaseal formation. The pipette holding potentials were -60 mV. (I) summary of single-channel open probabilities (NPo) as in (H).</p

Threshold of TRPC5 mechanosensitivity.

<p>(A) representative time-series traces showing [Ca²⁺]_i in TRPC5-expressing HEK293 cells in response to different osmolarities. Blue bar on top indicated duration of hypoosmolarity. (B) quantification of the [Ca²⁺]_i response at different osmolarities. *, <i>p<0</i>.<i>05</i> compared to <i>270 mOsm</i>. (C) representative traces showing the stretch-activated channel under different pipette pressures from a single cell-attached patch of TRPC5-expressing CHO-K1 cell. (D) quantification of single-channel open probabilities (NPo) of under different pipette pressure as in (C). *, <i>p<0</i>.<i>05</i> compared to <i>0 mmHg</i>.</p

Actin filament is essential to TRPC5 mechanosensitivity to hypoosmotic stress.

<p>(A) a representative time-series trace showing [Ca²⁺]_i responses to different osmolarities in TRPC5-expressing HEK293 cells that were pretreated with 25 μM cytochalasin D for 45 min. (B) summary showing effect of 25 μM cytochalasin D treatment on the [Ca²⁺]_i responses to hypoosmolarity. (C) representative time-series traces showing [Ca²⁺]_i responses to 100 μM LaCl₃ (La³⁺, <i>arrow</i> indicates time of addition) in cells that were treated with or without 25 μM cytochalasin D. (D) summary of the [Ca²⁺]_i responses to 100 μM carbachol (<i>Cch</i>) or 100 μM LaCl₃ (<i>La</i>^<i>3+</i>). <i>n</i>.<i>s</i>. denotes "not significant". E, a representative cell-attached patch of TRPC5-expressing CHO-K1 cells pretreated with 5 μM cytochalasin D at 0 mmHg and -40 mmHg pipette pressure. F, quantifications of channel open probability (NPo) from patches with or without cytochalasin D treatment. NPo of cytochalasin D treated patches is significantly lower compared to the untreated at -40 mmHg (*, <i>p<0</i>.<i>05</i>), and is significantly higher compared to that at 0 mmHg (<i>#</i>, <i>p<0</i>.<i>05</i>). (G) representative time-series trace showing [Ca²⁺]_i response to different osmolarities in HEK293 cells expressing ΔC-TRPC5, a truncated form lacking the C-terminal PDZ-binding motif. (H) summary of [Ca²⁺]_i responses to different osmolarities in ΔC-TRPC5-expressing HEK293 cells. *, <i>p<0</i>.<i>05</i> compared to <i>270 mOsm</i>.</p

Cephalopod biology and care, a COST FA1301 (CephsInAction) training school: anaesthesia and scientific procedures

Cephalopods are the sole invertebrates included in the list of regulated species following the Directive 2010/63/EU. According to the Directive, achieving competence through adequate training is a requisite for people having a role in the different functions (article 23) as such carrying out procedures on animals, designing procedures and projects, taking care of animals, killing animals. Cephalopod Biology and Care Training Program is specifically designed to comply with the requirements of the "working document on the development of a common education and training framework to fulfil the requirements under the Directive 2010/63/EU". The training event occurred at the ICM-CSIC in Barcelona (Spain) where people coming from Europe, America and Asia were instructed on how to cope with regulations for the use of cephalopod molluscs for scientific purposes. The training encompasses discussion on the guidelines for the use and care of animals and their welfare with particular reference to procedures that may be of interest for neuroscience. Intensive discussion has been carried out during the training sessions with focus on behavioural studies and paradigms, welfare assessment, levels of severity of scientific procedures, animal care, handling, transport, individual identification and marking, substance administration, anaesthesia, analgesia and humane killing