Biology subjects

Tanimoto, M.

Publications and source records attributed to Tanimoto, M..

5 recordsLinked to original sources

bioRxiv2025

Head stabilization behavior and underlying circuit mechanisms in larval zebrafish

Head stabilization is essential for animal survival, enabling stable sensory input and effective motor coordination. Animals stabilize their heads in response to vestibular stimuli through the vestibulo-collic reflex (VCR). While the VCR has been characterized in tetrapod vertebrates, it remains unknown whether fish, which lack an anatomical neck, employ a comparable behavior. Here, we demonstrate that larval zebrafish exhibit VCR-like behaviors: they adjust their head orientation relative to the body by rostral body flexion during pitch tilts. The rostral body flexed ventrally during head-up posture, whereas it flexed dorsally during head-down posture. These flexions partially compensated for the head pitch changes, thereby contributing to head stabilization. We also identified the muscles and neural circuits responsible for these two types of body flexions. Both the dorsal and ventral flexions were mediated by the same vestibular nucleus, but neural signals were transmitted through distinct pathways, either involving or bypassing a class of reticulospinal neurons. The dorsal and ventral flexions were ultimately produced by specialized dorsal and ventral muscles in the rostral body, respectively. The neural circuits underlying these body flexions in fish share similarities with those underlying the mammalian VCR. Together, our results demonstrate that fish exhibit a VCR-like behavior through comparable circuit mechanisms, suggesting that the VCR is evolutionarily conserved across vertebrates.

neuroscience↗

bioRxiv2025

Biomechanics of static roll posture control by body flexion in adult zebrafish

Posture control is crucial for animals. Static posture control in fish remains poorly explored. Recent studies have shown that larval zebrafish perform body flexion during slight roll tilts: the body flexion displaces a gas-filled swim bladder, generating counter-rotation torque for postural recovery through misalignment of gravity and buoyancy forces. Swim bladder deflation impairs this postural recovery, suggesting its critical role. This static posture control strategy may be utilized by many fish species. However, adult fish differ from larvae in morphology and behavior, raising questions about the generality of this mechanism. Our behavioral analysis showed that adult zebrafish also flexed their body during roll tilts, with flexion persisting until recovery to an upright posture. Similarly to larvae, swim bladder deflation impaired postural recovery. These results demonstrate that adult fish employ static roll posture control through body flexion and suggest the generality of this mechanism in fish species.

zoology↗

bioRxiv2023

Anemonefish are better taxonomists than humans.

The symbiosis between giant sea anemones, photosynthetic algae of the family Symbiodiniaceae, and anemonefish is an iconic example of a mutualistic "menage a 3"1. Patterns of associations among 28 species of anemonefish and 10 species of giant sea anemone hosts are complex: Some anemonefish species are highly specialized to inhabit only one species of sea anemone (e.g., Amphiprion frenatus with Entacmaea quadricolor), whereas others are more generalist and can live in almost any host species (e.g., Amphiprion clarkii)1,2,3. Reasons for host preferences and the mechanisms involved are obscured, among other things, by the lack of resolution of giant sea anemone phylogeny. Recent molecular analyses have shown that giant sea anemones hosting anemonefish belong to three distinct clades: Entacmaea, Stichodactyla, and Heteractis4,5,6. Inside these clades, however, species delimitation has been impeded by morphological variability of the giant sea anemones and is poorly resolved with classical markers4,5. Here, we employed an extensive transcriptomic dataset from 55 sea anemones collected from southern Japan to build a robust phylogeny. With this dataset, we observed that the bubble-tip sea anemone E. quadricolor, currently considered to be a single species, can in fact be separated into at least four distinct cryptic lineages (A-D). Moreover, these lineages can be precisely distinguished by their association with anemonefish: A. frenatus is only found associated with lineage D, whereas A. clarkii lives in the other three lineages.

evolutionary biology↗

bioRxiv2022

Biomechanics and neural circuits for vestibular-induced fine postural control in larval zebrafish

Land-walking vertebrates maintain a desirable posture by finely controlling muscles. It is unclear whether fish also finely control posture in the water. Here, we showed that larval zebrafish have fine posture control. When roll-tilted, fish recovered their upright posture using a reflex behavior, which was a slight body bend near the swim bladder. The vestibular-induced body bend produces a misalignment between gravity and buoyancy, generating a moment of force that recovers the upright posture. We identified the neural circuits for the reflex, including the vestibular nucleus (tangential nucleus) through reticulospinal neurons (neurons in the nucleus of the medial longitudinal fasciculus) to the spinal cord, and finally to the posterior hypaxial muscles, a special class of muscles near the swim bladder. These results suggest that fish maintain a dorsal-up posture by frequently performing the body bend reflex and demonstrate that the reticulospinal pathway plays a critical role in fine postural control.

neuroscience↗

bioRxiv2020

A fast genetically encoded fluorescent sensor for faithful in vivo acetylcholine detection in mice, fish, worms and flies

Here we design and optimize a genetically encoded fluorescent indicator, iAChSnFR, for the ubiquitous neurotransmitter acetylcholine, based on a bacterial periplasmic binding protein. iAChSnFR shows large fluorescence changes, rapid rise and decay kinetics, and insensitivity to most cholinergic drugs. iAChSnFR revealed large transients in a variety of slice and in vivo preparations in mouse, fish, fly and worm. iAChSnFR will be useful for the study of acetylcholine in all animals.

neuroscience↗