Larval pufferfish protected by maternal tetrodotoxin

Marine pufferfish contain tetrodotoxin (TTX), an extremely potent neurotoxin. All species of the genus Takifugu accumulate TTX in the liver and ovaries, although the tissue(s) in which it is localized can differ among species. TTX is the major defense strategy the pufferfish appears to use against predators. TTX is also used as a male-attracting pheromone during spawning. Here we demonstrate an additional (and unexpected) use of maternal TTX in the early larval stages of the Takifugu pufferfish. Predation experiments demonstrated that juveniles of all the species of fish used as predators ingested pufferfish larvae, but spat them out promptly. Liquid Chromatography-Tandem Mass Spectrometry (LC-MSMS) analysis revealed that the pufferfish larvae contain a small quantity of TTX, which is not enough to be lethal to the predators. Immunohistochemical analysis with anti-TTX monoclonal antibody revealed that the TTX is primarily localized in the body surface of the larvae as a layer of protection. Our study showed the female parent of the Takifugu pufferfish vertically transfers TTX to the larvae through its accumulation in the ovaries, and subsequent localization on the body surface of the larvae

Sub-micrometer particle size effects on metastable phases for a photoswitchable Co–Fe Prussian blue analog

International audienceMetastable phases of the photoswitchable molecular magnet K0.3Co[Fe(CN)6]0.77 ⋅ nH2O in sub-micrometer particles have been structurally investigated by synchrotron powder x-ray diffraction (PXRD) measurements. The K0.3Co[Fe(CN)6]0.77 ⋅ nH2O bulk compound (studied here with a sample having average particle size of 500 nm) undergoes a charge transfer coupled spin transition (CTCST), where spin configurations change between a paramagnetic CoII (S = 3/2) –FeIII (S = 1/2) high-temperature (HT) state and a diamagnetic CoIII (S = 0) –FeII (S = 0) low-temperature (LT) state. The bulk compound exhibits a unique intermediate (IM) phase, which corresponds to a mixture of HT and LT spin states that depend on the cooling rate. Several hidden metastable HT states emerge as a function of thermal and photo stimuli, namely: (1) a quench (Q) state generated from the HT state by flash cooling, (2) a LTPX state obtained by photoexcitation from the LT state derived by thermal relaxation from the Q state, and (3) an IMPX state accessed by photo-irradiation from the IM state. A sample with a smaller particle size, 135 nm, is investigated for which the particles are on the scale of the coherent LT domains in the IM phase within the larger 500 nm sample. PXRD studies under controlled thermal and/or optical excitations have clarified that the reduction of the particle size profoundly affects the structural changes associated with the CTCST. The unusual IM state is also observed as segregated domains in the 135 nm particle, but the collective structural transformations are more hindered in small particles. The volume change decreases to 2%–3%, almost half the value found for 500 nm particles (5%–8%), even though the linear thermal expansion coefficients are larger for the smaller particles. Furthermore, photoexcitation from the IM and LT states does not turn into single phases in the smaller particles, presumably because of the multiple interfaces and/or internal stress generated by the coexistence of small CoII–FeIII and CoIII–FeII domains in the lattice. Since the reduced particle size limits cooperativity and domain growth in the lattice, CTCST in the small particle sample becomes less sensitive to external stimuli

High-pressure behavior of heteroepitaxial core-shell particles made of Prussian blue analogs

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This paper appeared in J. Appl. Phys. 129, 235106 (2021) and may be found at https://doi.org/10.1063/5.0049223.International audienceWe report the compressibility of two Prussian blue analogs (PBAs) under hydrostatic pressure, one with small and one with a relatively large cubic unit cell among PBAs, and investigate the modification of their elastic properties when the two lattices are coupled within a heteroepitaxial core-shell structure. Bulk modulus (K0) values are derived from x-ray powder diffraction experiments using a diamond anvil cell with silicone oil as a pressure-transmitting medium. The pressure-volume curves fitted to Murnaghan equations of states show that K0 inversely scales with the crystal packing for the rubidium cobalt hexacyanoferrate and rubidium nickel hexacyanochromate samples (K0 ∼ 29 GPa for Co-Fe PBA, a0 = 9.95 Å and ∼20 GPa for Ni-Cr PBA, a0 = 10.48 Å with a0 being the lattice constant at ambient pressure). The two single-phase samples undergo a cubic-to-rhombohedral phase transition above ∼0.8 GPa, which correlates fairly well with the build-up of nonhydrostatic pressure contributions in the cell. Within the core-shell structure, the volume change observed for the core scales with that of the shell because of the configuration close to the case of a solid pressure-transmitting medium. The Ni-Cr PBA shell layer exhibits an increased rhombohedral distortion with respect to the single-phase reference possibly associated with shearing at the core-shell interface. Its bulk modulus is not significantly modified with respect to that of the single-phase sample despite the presence of defects associated with the growth mode, whereas the P-V curve of the core suggests a stiffening of the Co-Fe PBA lattice