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1. A biomechanical paradox in fish: swimming and suction feeding produce orthogonal strain gradients in the axial musculature

   https://doi.org/10.1038/s41598-021-88828-x  

   Jimenez, Yordano E.; Marsh, Richard L.; Brainerd, Elizabeth L. (May 2021, Scientific Reports)

   Abstract The axial musculature of fishes has historically been characterized as the powerhouse for explosive swimming behaviors. However, recent studies show that some fish also use their ‘swimming’ muscles to generate over 90% of the power for suction feeding. Can the axial musculature achieve high power output for these two mechanically distinct behaviors? Muscle power output is enhanced when all of the fibers within a muscle shorten at optimal velocity. Yet, axial locomotion produces a mediolateral gradient of muscle strain that should force some fibers to shorten too slowly and others too fast. This mechanical problem prompted research into the gearing of fish axial muscle and led to the discovery of helical fiber orientations that homogenize fiber velocities during swimming, but does such a strain gradient also exist and pose a problem for suction feeding? We measured muscle strain in bluegill sunfish,Lepomis macrochirus,and found that suction feeding produces a gradient of longitudinal strain that, unlike the mediolateral gradient for locomotion, occurs along the dorsoventral axis. A dorsoventral strain gradient within a muscle with fiber architecture shown to counteract a mediolateral gradient suggests that bluegill sunfish should not be able to generate high power outputs from the axial muscle during suction feeding—yet prior work shows that they do, up to 438 W kg⁻¹. Solving this biomechanical paradox may be critical to understanding how many fishes have co-opted ‘swimming’ muscles into a suction feeding powerhouse. 

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2. Proteome Dynamics Across the Blastogenic Cycle of Botryllus schlosseri Reveals Targets for Cell Immortalization

   https://doi.org/10.1101/2025.07.01.662660  

   Dong, Weizhen; Leprêtre, Maxime; Enriquez, Isabel; Luu, Brenda; Lin, Mandy; Hamar, Jens; Kültz, Dietmar (July 2025, bioRxiv)

   Abstract The colonial tunicateBotryllus schlosseriregenerates weekly through a cyclical process in which adult zooids are replaced by a new generation of buds. While this dynamic asexual development is a hallmark of the species, its molecular regulation remains poorly understood. This study presents the first comprehensive proteomic analysis ofB. schlosseriblastogenesis at the individual zooid level, using data-independent acquisition mass spectrometry to quantify protein abundance across developmental stages. The results reveal extensive proteome remodeling between proliferating buds and degenerating zooids. Co-expression analysis identified stage-specific protein modules enriched for biosynthesis and cell cycle pathways in buds, and for apoptosis, catabolism, and metabolic remodeling in zooids. A focused comparison between takeover buds and takeover zooids uncovered distinct regulatory programs controlling proliferation and senescence. Key proteins, including CDK1, CDK2, HDAC2, and PCNA, were identified as candidate regulators of cell cycle progression. These findings provide a molecular framework for understanding regeneration in a basal chordate and offer protein targets that may enable cell cycle re-entry and long-term culture of tunicate primary cells. Summary StatementThis study maps proteome dynamics during the blastogenic cycle inBotryllus schlosseri, identifying candidate proteins that regulate cell proliferation and offer targets for tunicate cell line development. 

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3. Biotemplated flagellar nanoswimmers

   https://doi.org/10.1063/1.5001777  

   Ali, Jamel; Cheang, U_Kei; Darvish, Armin; Kim, Hoyeon; Kim, Min_Jun (November 2017, APL Materials)

   In this article, a porous hollow biotemplated nanoscale helix that can serve as a low Reynolds number robotic swimmer is reported. The nanorobot utilizes repolymerized bacterial flagella from Salmonella typhimurium as a nanotemplate for biomineralization. We demonstrate the ability to generate templated nanotubes with distinct helical geometries by using specific alkaline pH values to fix the polymorphic form of flagellar templates. Using uniform rotating magnetic fields to mimic the motion of the flagellar motor, we explore the swimming characteristics of these silica templated flagella and demonstrate the ability to wirelessly control their trajectories. The results suggest that the biotemplated nanoswimmer can be a cost-effective alternative to the current top-down methods used to produce helical nanorobots. 

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4. Depth‐Dependent Azimuthal Anisotropy Beneath the Juan de Fuca Plate System

   https://doi.org/10.1029/2020JB019477  

   Eilon, Zachary C.; Forsyth, Donald W. (July 2020, Journal of Geophysical Research: Solid Earth)

   Abstract We use surface wave measurements to reveal anisotropy as a function of depth within the Juan de Fuca and Gorda plate system. Using a two‐plane wave method, we measure phase velocity and azimuthal anisotropy of fundamental mode Rayleigh waves, solving for anisotropic shear velocity. These surface wave measurements are jointly inverted with constraints fromSKSsplitting studies using a Markov chain approach. We show that the two data sets are consistent and present inversions that offer new constraints on the vertical distribution of strain beneath the plates and the processes at spreading centers. Anisotropy of the Juan de Fuca plate interior is strongest (~2.4%) in the low‐velocity zone between ~40‐ to 90‐km depth, with ENE direction driven by relative shear between plate motion and mantle return flow from the Cascadia subduction zone. In disagreement withPnmeasurements, weak (~1.1%) lithospheric anisotropy in Juan de Fuca is highly oblique to the expected ridge‐perpendicular direction, perhaps connoting complex intralithospheric fabrics associated with melt or off‐axis downwelling. In the Gorda microplate, strong shallow anisotropy (~1.9%) is consistent withPninversions and aligned with spreading and may be enhanced by edge‐driven internal strain. Weak anisotropy with ambiguous orientation in the low‐velocity zone can be explained by Gorda's youth and modest motion relative to the Pacific. Deeper (≥90 km) fabric appears controlled by regional flow fields modulated by the Farallon slab edge: anisotropy is strong (~1.8%) beneath Gorda, but absent beneath the Juan de Fuca, which is in the strain shadow of the slab. 

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5. Relative Timing of Off‐Axis Volcanism From Sediment Thickness Estimates on the 8°20’N Seamount Chain, East Pacific Rise

   https://doi.org/10.1029/2022GC010335  

   Fabbrizzi, Andrea; Parnell‐Turner, Ross; Gregg, Patricia M.; Fornari, Daniel J.; Perfit, Michael R.; Wanless, V. Dorsey; Anderson, Molly (September 2022, Geochemistry, Geophysics, Geosystems)

   Abstract Volcanic seamount chains on the flanks of mid‐ocean ridges record variability in magmatic processes associated with mantle melting over several millions of years. However, the relative timing of magmatism on individual seamounts along a chain can be difficult to estimate withoutin situsampling and is further hampered by Ar⁴⁰/Ar³⁹dating limitations. The 8°20’N seamount chain extends ∼170 km west from the fast‐spreading East Pacific Rise (EPR), north of and parallel to the western Siqueiros fracture zone. Here, we use multibeam bathymetric data to investigate relationships between abyssal hill formation and seamount volcanism, transform fault slip, and tectonic rotation. Near‐bottom compressed high‐intensity radiated pulse, bathymetric, and sidescan sonar data collected with the autonomous underwater vehicleSentryare used to test the hypothesis that seamount volcanism is age‐progressive along the seamount chain. Although sediment on seamount flanks is likely to be reworked by gravitational mass‐wasting and current activity, bathymetric relief andSentryvehicle heading analysis suggest that sedimentary accumulations on seamount summits are likely to be relatively pristine. Sediment thickness on the seamounts' summits does not increase linearly with nominal crustal age, as would be predicted if seamounts were constructed proximal to the EPR axis and then aged as the lithosphere cooled and subsided away from the ridge. The thickest sediments are found at the center of the chain, implying the most ancient volcanism there, rather than on seamounts furthest from the EPR. The nonlinear sediment thickness along the 8°20’N seamounts suggests that volcanism can persist off‐axis for several million years. 

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