Journal of Experimental Biology - Latest Issue

• How visual information reaches the goldfish Mauthner neuron: from seeing to a fast-start decision in 35 ms

  ABSTRACT

  The two huge Mauthner neurons (MNs) form the center of the fast-start network in the hindbrain of fish. Their activation initiates a rapid turning maneuver, the so-called C-start, within milliseconds. Here, we recorded intracellularly from the MNs of goldfish to quantify the spatiotemporal flow of visual information from the two eyes, the optic nerves, and the ipsilateral and contralateral hemispheres of the optic tectum (OT) to each MN. Strong light flashes delivered to one eye induced postsynaptic potentials (PSPs) in both MNs after a delay of 35 ms. By directly stimulating the optic nerve, we show that most of this time (80%) is needed for transduction and processing in the retina. Visual stimulation of the eye and direct electrical stimulation of the optic nerve was effective regardless of which eye or which optic nerve was stimulated. Stimulating any region of the ipsilateral or contralateral OT caused PSPs in both MNs. Remarkably, the PSPs induced by our brief visual and electrical stimuli were of remarkably complex structure and long duration. The connectivity pattern and PSP durations we describe here suggest an arrangement that supports a high degree of flexibility in C-start directionality and the integration of sensory information that arrives with different delays in a natural encounter.

• Behavioral and physiological–biochemical responses of a polychaete ( Perinereis aibuhitensis ) under severe seawater acidification at different temperatures

  ABSTRACT

  The intertidal zone experiences significant fluctuations in temperature and pH, posing significant challenges to marine organisms. Perinereis aibuhitensis, a eurythermal and euryhaline polychaete inhabiting estuaries, where pH is often lower than in the open ocean and further reduced within sediments, has probably evolved robust adaptations to such stresses. We investigated its behavioral, physiological and metabolic responses under combined temperature (15°C, 20°C, 25°C) and seawater acidification (pH 5.5, 6.7, 8.0) conditions. Perinereis aibuhitensis exhibited stable behavioral performance and metabolic homeostasis under control conditions (20°C, pH 8.0). It maintained burrowing activity and activated physiological and metabolic regulation at pH 6.7. However, its motion significantly declined with failed behavioral regulation under pH 5.5: radial undulation duration decreased by 97.63% and pumping volume by 97.97%. Energy was reallocated toward antioxidant defense and maintenance of basic physiological functions, reflected in downregulation of the γ-aminobutyric acid (GABA) metabolic pathway alongside upregulation of ABC transporters and arachidonic acid metabolism. At 25°C, combined warming and acidification disrupted energy allocation under pH 5.5. This disruption was accompanied by enhanced motion, which further constrained energy allocation, leading to significant oxidative damage (malondialdehyde content increased by 94.54%) and concurrently impairing tryptophan metabolism, glycerophospholipid metabolism and ABC transporter function, with the entire cascade ultimately collapsing its adaptive mechanisms. This demonstrates that severe acidification, especially under warming, compromises bioturbation and metabolic stability in P. aibuhitensis, with potential negative impacts on polychaete communities and their vital ecological functions in intertidal ecosystems. Our findings provide critical insights for predicting climate change impacts on marine infauna.

• Energy availability influences the dynamics of thermal phenotypic plasticity

  ABSTRACT

  We tested whether food availability limits phenotypic plasticity in thermal tolerance in the amphipod Echinogammarus marinus. We shifted specimens from 10°C to an acclimation temperature of 20°C, and kept them there for different durations with and without food before measuring the time to immobilization at 30°C. Our results show that thermal tolerance increases with acclimation duration, but this response was about two times more pronounced in fed than in unfed individuals. We also decomposed the plastic response into a rate component (how fast the trait changes) and a capacity component (by how much it changes). This showed that the overall effect of food treatment on the temporal dynamics of thermal tolerance was primarily driven by the effect on capacity. We conclude that laboratory derived thermal tolerance data from experiments where ecological conditions are otherwise optimal may provide overly optimistic estimates of how well organisms deal with extreme events through phenotypic plasticity.

• Correction: Wing damage affects flight kinematics but not flower tracking performance in hummingbird hawkmoths

• Diet-induced transgenerational effects on Drosophila dormancy are not mediated by the microbiome

  ABSTRACT

  Environmental signals exert influences not only on the current generation, but also extend to subsequent generations, even when these signals no longer persist. These transgenerational effects can be mediated through several mechanisms, including epigenetic inheritance and composition of the gut microbiome. In this study, we investigated the contribution of the microbiome to diet-induced transgenerational effects on reproductive dormancy. Multiple strains of Drosophila simulans were subjected to a shift from a sugar-rich to a sugar-poor diet and the impact of this diet switch on dormancy was determined over multiple generations. Consistent with significant transgenerational effects, we observed a gradual reduction in dormancy incidence with an increasing number of generations exposed to the new, sugar-poor diet. Despite the variation in dormancy induced by the dietary shift, the microbiome composition remained largely stable. Consequently, we conclude that these transgenerational effects are not determined by changes in the bacterial microbiome composition.