Abstract. We document the long-term evolution of an Agulhas ring detected from satellite altimetry using a technique from nonlinear dynamical systems that enables objective (i.e., observer-independent) eddy framing. Such objectively detected eddies have Lagrangian (material) boundaries that remain coherent (unfilamented) over the detection period. The ring preserves a quite compact material entity for a period of about 2 years even after most initial coherence is lost within 5 months after detection. We attribute this to the successive development of short-term coherent material boundaries around the ring. These boundaries provide effective short-term shielding for the ring, which prevents a large fraction of the ring's interior from being mixed with the ambient turbulent flow. We show that such coherence regain events cannot be inferred from Eulerian analysis. This process is terminated by a ring-splitting event which marks the ring demise, near the South American coast. The genesis of the ring is characterized by a ring-merging event away from the Agulhas retroflection, followed by a 4-month-long partial coherence stage, scenario that is quite different than a simple current occlusion and subsequent eddy pinch off.

Radial spokes are structurally conserved, macromolecular complexes that are essential for the motility of 9 + 2 motile cilia. In Chlamydomonas species, mutations in radial spoke proteins result in ciliary motility defects. However, little is known about the function of radial spoke proteins during embryonic development. Here, we investigated the role of a novel radial spoke protein, leucine-rich repeat containing protein 23 (Lrrc23), during zebrafish embryonic development. Mutations in lrrc23 resulted in a selective otolith formation defect during early ear development. Similar otolith defects were also present in the radial spoke head 3 homolog ( rsph3) and radial spoke head 4 homolog A ( rsph4a) radial spoke mutants. Notably, the radial spoke protein mutations specifically affected ciliary motility in the otic vesicle (OV), whereas motile cilia in other organs functioned normally. Via high-speed video microscopy, we found that motile cilia formation was stochastic and transient in the OV. Importantly, all the motile cilia in the OV beat circularly, in contrast to the planar beating pattern of typical 9 + 2 motile cilia. We identified the key time frame for motile cilia formation during OV development. Finally, we showed that the functions of radial spoke proteins were conserved between zebrafish and Tetrahymena. Together, our results suggest that radial spoke proteins are essential for ciliary motility in the OV and that radial spoke-regulated OV motile cilia represent a unique type of cilia during early zebrafish embryonic development.-Han, X., Xie, H., Wang, Y., Zhao, C. Radial spoke proteins regulate otolith formation during early zebrafish development.

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Background Mahi‐mahi ( Coryphaena hippurus ) is a commercially and ecologically important fish species that is widely distributed in tropical and subtropical waters. Biological attributes and reproductive capacities of mahi‐mahi make it a tractable model for experimental studies. In this study, life development of cultured mahi‐mahi from the zygote stage to adult has been described. Results A comprehensive developmental table has been created reporting development as primarily detailed observations of morphology. Additionally, physiological, behavioral, and molecular landmarks have been described to significantly contribute in the understanding of mahi life development. Conclusion Remarkably, despite the vast difference in adult size, many developmental landmarks of mahi map quite closely onto the development and growth of Zebrafish and other warm‐water, active Teleost fishes.

Freshwater-and seawater-acclimated Fundulus heteroclitus were exposed to acute hypoxia (10% air saturation, 3 h), followed by normoxic recovery (3 h). In both salinities, ventilation increased and heart rate fell in the classic manner, while _ M O 2 initially declined by ∼50%, with partial restoration by 3 h of hypoxia, and no O 2 debt repayment during recovery. Gill paracellular permeability (measured with [ 14 C] PEG-4000) was 1.4-fold higher in seawater, and declined by 50% during hypoxia with post-exposure overshoot to 188%. A similar pattern with smaller changes occurred in freshwater. Drinking rate (also measured with [ 14 C] PEG-4000) was 8-fold higher in seawater fish, but declined by ∼90% during hypoxia in both groups, with post-exposure overshoots to ∼270%. Gill diffusive water flux (measured with 3 H 2 O) was 1.9-fold higher in freshwater fish, and exhibited a ∼35% decrease during hypoxia, which persisted throughout recovery, but was unchanged during hypoxia in seawater fish. Nevertheless, freshwater killifish gained mass while seawater fish lost mass during hypoxia, and these changes were not corrected during normoxic recovery. We conclude that this hypoxiatolerant teleost beneficially reduces gill water permeability in a salinity-dependent fashion during hypoxia, despite attempting to simultaneously improve _ M O 2 , but nevertheless incurs a net water balance penalty in both freshwater and seawater.