The potential for egg-guarding care in females of the damselfish, Dascyllus reticulatus, in the absence of uniparental male care.

Male damselfish typically demonstrate uniparental egg-guarding care in nature. Potential plasticity in sexual behavior has recently been reported in various teleost fish. To examine behavioral plasticity in parental care, we conducted aquarium experiments to explore the potential for egg-guarding care in the female damselfish, Dascyllus reticulatus. After initial caretaking, males were removed from the mating nests, and cohabiting females frequently exhibited egg predation on the same day. However, we confirmed that females showed significantly decreased egg-predation frequencies on the following day and showed egg-caring behaviors. All experimental females guarded their eggs until they hatched. Females subsequently spawned eggs as females even after performing parental care behaviors, indicating no progression of sex change into males. Molecular analysis of select pituitary gland hormones indicated that egg-caring females and males showed high expression levels of prolactin, suggesting its involvement in the development of parental care behaviors. The cryptic possession of caretaking ability in females may be a tactical response to the need for temporary replacement of the care roles in cases where caretaking males are removed, for example, through predation, in damselfish species living in sexually cohabiting groups.

Bidirectional sex change and plasticity of gonadal phases in the goby Lubricogobius exiguus.

Of the ca. 500 known hermaphroditic fish species, bidirectional sex change and simultaneous hermaphroditism are currently known in 69 and 57 species, respectively. Both bidirectional sex change and simultaneous hermaphroditism are predicted to evolve when mating opportunities are limited, such as in cases of low-density distribution and low mobility of individuals. However, the plasticity of sex is adaptive in obtaining mating opportunities, especially when there is mate loss. Pair-rearing experiments and histological observations of gonads of the goby Lubricogobius exiguus, which has low-density distributions and low mobility, showed bidirectional sex change. The male-role individuals in pairs had gonads in which only the testis was functional (male-phase), whereas the female-role individuals had two types of gonads: only the ovary was functional (female-phase) or both testis and ovary were functional (simultaneously hermaphroditic phase, SH-phase). In addition, single-rearing experiments showed SH-phase gonads in all individuals, and some cyclic spawning but no self-fertilization occurred. These results revealed that L. exiguus has an unusual sexual pattern among hermaphroditic fishes because they undergo bidirectional sex change and some maintain SH-phase gonads. These findings indicate that the low-density distribution and low mobility of L. exiguus in their natural habitat may have influenced the evolution of this unique sexual pattern.

Comparison of mortality and feeding behavior of the false cleanerfish Aspidontus taeniatus and the lance blenny A. dussumieri regarding the effects of mimicry.

Many examples of mimicry have been reported in coral reef fishes of which the most well known is the mimicry of the bluestreak cleaner wrasse, Labroides dimidiatus by the false cleanerfish, Aspidontus taeniatus. To examine the effect of protective and aggressive mimicry of A. taeniatus, mortality and feeding behavior were compared with those of the non-mimic lance blenny, Aspidontus dussumieri, by field observations on the coral reefs of Miyako Island, Okinawa, southern Japan. Survival rate of A. taeniatus was more than twice higher than that of A. dussumieri, but the detected differences were not significant, and the effect of protective mimicry could not be determined. The benthic foods common to both species (the tubeworm, Spirobranchus giganteus, and the boring clam, Tridacna crocea) were very scarce in the study sites, and the feeding behavior of the two species was clearly different: A. dussumieri pecked at the bottom substrate, whereas A. taeniatus fed on fish fins and eggs of damselfish, regardless of body size. Our findings are the first documented evidence of the effect of aggressive mimicry on biting fish fins in relation to the availability of other foods not only in small but also in large A. taeniatus. Supplementary Information: The online version contains supplementary material available at 10.1007/s10164-022-00769-8.

Nitrogen reduction by the Fe sites of synthetic [Mo3S4Fe] cubes.

Nitrogen (N2) fixation by nature, which is a crucial process for the supply of bio-available forms of nitrogen, is performed by nitrogenase. This enzyme uses a unique transition-metal-sulfur-carbon cluster as its active-site co-factor ([(R-homocitrate)MoFe7S9C], FeMoco)1,2, and the sulfur-surrounded iron (Fe) atoms have been postulated to capture and reduce N2 (refs. 3-6). Although there are a few examples of synthetic counterparts of the FeMoco, metal-sulfur cluster, which have shown binding of N2 (refs. 7-9), the reduction of N2 by any synthetic metal-sulfur cluster or by the extracted form of FeMoco10 has remained elusive, despite nearly 50 years of research. Here we show that the Fe atoms in our synthetic [Mo3S4Fe] cubes11,12 can capture a N2 molecule and catalyse N2 silylation to form N(SiMe3)3 under treatment with excess sodium and trimethylsilyl chloride. These results exemplify the catalytic silylation of N2 by a synthetic metal-sulfur cluster and demonstrate the N2-reduction capability of Fe atoms in a sulfur-rich environment, which is reminiscent of the ability of FeMoco to bind and activate N2.

The false cleanerfish relies on aggressive mimicry to bite fish fins when benthic foods are scarce in their local habitat.

The false cleanerfish, Aspidontus taeniatus (Blenniidae), is known for its morphological resemblance to the bluestreak cleaner wrasse Labroides dimidiatus (Labridae). It has been suggested that A. taeniatus, which acts as a mimic, can easily bite the fins of other fishes that are deceived into requesting cleaning from it or allowing it to approach them. In fact, A. taeniatus frequently utilises benthic food items, such as damselfish eggs, the Christmas tree worm Spirobranchus giganteus, and the boring clam Tridacna crocea. Although geographical variation in the reliance on aggressive mimicry (fin biting) has been reported, the factors have not been determined. We hypothesised that one of the factors is the abundance of benthic food items. To examine our hypothesis, we compared the feeding behaviour of A. taeniatus at two locations showing contrasting abundances of benthic food items in Okinawa, southern Japan. The frequency of fin biting by the small A. taeniatus in Ishigaki Island, where S. giganteus and T. crocea were very rare, was significantly higher than that in Sesoko Island, where the two food items were abundant. We conclude that the importance of aggressive mimicry in A. taeniatus varies depending on local food conditions.

Synthesis of Dinuclear Mo-Fe Hydride Complexes and Catalytic Silylation of N2.

Two transition-metal atoms bridged by hydrides may represent a useful structural motif for N2 activation by molecular complexes and the enzyme active site. In this study, dinuclear MoIV -FeII complexes with bridging hydrides, CpR Mo(PMe3 )(H)(µ-H)3 FeCp* (2 a; CpR =Cp*=C5 Me5 , 2 b; CpR =C5 Me4 H), were synthesized via deprotonation of CpR Mo(PMe3 )H5 (1 a; CpR =Cp*, 1 b; CpR =C5 Me4 H) by Cp*FeN(SiMe3 )2 , and they were characterized by spectroscopy and crystallography. These Mo-Fe complexes reveal the shortest Mo-Fe distances ever reported (2.4005(3) Šfor 2 a and 2.3952(3) Šfor 2 b), and the Mo-Fe interactions were analyzed by computational studies. Removal of the terminal Mo-H hydride in 2 a-2 b by [Ph3 C]+ in THF led to the formation of cationic THF adducts [CpR Mo(PMe3 )(THF)(µ-H)3 FeCp*]+ (3 a; CpR =Cp*, 3 b; CpR =C5 Me4 H). Further reaction of 3 a with LiPPh2 gave rise to a phosphido-bridged complex Cp*Mo(PMe3 )(µ-H)(µ-PPh2 )FeCp* (4). A series of Mo-Fe complexes were subjected to catalytic silylation of N2 in the presence of Na and Me3 SiCl, furnishing up to 129±20 equiv of N(SiMe3 )3 per molecule of 2 b. Mechanism of the catalytic cycle was analyzed by DFT calculations.

Case Report: Transoral Penetrating Medullocervical Injury by a Chopstick in Three Cats.

This case series describes transoral penetrating or contusive medullocervical injury by a wooden chopstick in three young cats presenting with acute tetraparesis. CT revealed that remnant fragments of a wooden chopstick penetrated the atlantooccipital space in cases 1 and 2. The remnant fragments were visualized clearly on CT under the bone window setting. MRI revealed a hyper-intense lesion in the spinal cord parenchyma at the level of C1 on T2-weighted images in case 3. Tetraparesis improved after surgical removal of the remnant fragment in case 2 and with supportive care in case 3.

Synthesis of [Mo3S4] Clusters from Half-Sandwich Molybdenum(V) Chlorides and Their Application as Platforms for [Mo3S4Fe] Cubes.

Triangular [Mo3S4] clusters are known to serve as platforms to accommodate a metal atom M, furnishing cubic [Mo3S4M] clusters. In this study, three [Mo3S4] clusters supported by η5-cyclopentadienyl (CpR) ligands, [CpR3Mo3S4]+ (CpR = C5Me4SiMe3, C5Me4SiEt3, and C5Me4H), were synthesized via half-sandwich molybdenum chlorides CpRMoCl4. In the cyclic voltammogram of the [Mo3S4] cluster having C5Me4H ligands, a weak feature appeared in addition to the [CpR3Mo3S4]0/- redox process, indicating the interaction between [CpR3Mo3S4]- and the [NnBu4] cation of the electrolyte, while such a feature was less significant for the C5Me4SiR3 variants. The [Mo3S4] clusters with bulky C5Me4SiR3 ligands were successfully applied as platforms to accommodate an Fe atom to furnish cubic [Mo3S4Fe] clusters. On the other hand, the corresponding reactions of the less bulky C5Me4H analogue gave complex mixtures.

Cubane-Type [Mo3 S4 M] Clusters with First-Row Groups†4-10 Transition-Metal Halides Supported by C5 Me5 Ligands on Molybdenum.

A synthetic protocol was developed for a series of cubane-type [Mo3 S4 M] clusters that incorporate halides of first-row transition metals (M) from Groups 4-10. This protocol is based on the anionic cluster platform [Cp*3 Mo3 S4 ]- ([1]- ; Cp*=η5 -C5 Me5 ), which crystallizes when K(18-crown-6) is used as the counter cation. Treatment of in situ-generated [1]- with such transition-metal halides led to the formation of [Mo3 S4 M] clusters, in which the M/halide ratio gradually changes from 1:2 to 1:1.5 and to 1:1, when moving from early to late transition metals. This trend suggests a tendency for early transition metals to tolerate higher oxidation states and adopt larger ionic radii relative to late transition metals. The properties of the [Mo3 S4 Fe] cluster 6 a were investigated in detail by using 57 Fe Mössbauer spectroscopy and computational methods.

Scaling mimesis: Morphometric and ecomorphological similarities in three sympatric plant-mimetic fish of the family Carangidae (Teleostei).

The mimetic juveniles of a number of carangid fish species resemble plant parts floating near the water surface, such as leaves, seeds and other plant debris. The present study is the first to verify the morphological similarities and ecomorphological relationships between three carangids (Oligoplites saurus, Oligoplites palometa and Trachinotus falcatus) and their associated plant models. Behavioral observations were conducted in the estuary of Curuçá River, in northeastern Pará (Brazil) between August 2015 and July 2016. Individual fishes and associated floating objects (models) were sampled for comparative analysis using both geometric and morphometric approaches. While the mimetic fish and their models retain their own distinct, intrinsic morphological features, a high degree of morphological similarity was found between each fish species and its model. The morphometric analyses revealed a general tendency of isometric development in all three fish species, probably related to their pelagic habitats, during all ontogenetic stages.

Synthesis and Characterization of Bioinspired [Mo2 Fe2 ]-Hydride Cluster Complexes and Their Application in the Catalytic Silylation of N2.

The hydride-supported [Mo2 Fe2 ] cluster complex {Cp*Mo(PMe3 )}2 {FeN(SiMe3 )2 }2 (H)8 (2 a; Cp*=η5 -C5 Me5 ) and its [Mo2 Mn2 ] congener 2 b were synthesized from the reactions of Cp*Mo(PMe3 )(H)5 (1) with M{N(SiMe3 )2 }2 (M=Fe, Mn). The amide-to-thiolate ligand-exchange reactions of complex 2 a with bulky thiol reagents (HSR; R=2,4,6-iPr3 C6 H2 (Tip), 2,6-(SiMe3 )2 C6 H3 (Btp)) furnished the corresponding hydride-supported [Mo2 Fe2 ](SR)2 cluster complexes. The [Mo2 Fe2 ] clusters served as catalyst precursors for the reductive silylation of N2 and yielded ≈65-69 equivalents of N(SiMe3 )3 relative to the [Mo2 Fe2 ] clusters. Treatment of complexes 2 a and b with an excess of CNtBu resulted in the formation of dinuclear Mo-Fe and Mo-Mn complexes, which indicated that the [Mo2 M2 ] cores (M=Fe, Mn) split into two dinuclear species upon accommodation of substrates.

[Fe4] and [Fe6] Hydride Clusters Supported by Phosphines: Synthesis, Characterization, and Application in N2 Reduction.

Multiple iron atoms bridged by hydrides is a common structural feature of the active species that have been postulated in the biological and industrial reduction of N2. In this study, the reactions of an Fe(II) amide complex with pinacolborane in the presence/absence of phosphines afforded a series of hydride-supported [Fe4] and [Fe6] clusters Fe4(µ-H)4(µ3-H)2{N(SiMe3)2}2(PR3)4 (PR3 = PMe3 (2a), PMe2Ph (2b), PEt3 (2c)), Fe6(µ-H)10(µ3-H)2(PMe3)10 (3), and (η6-C7H8)Fe4(µ-H)2{µ-N(SiMe3)2}2{N(SiMe3)2}2 (4), which were characterized crystallographically and spectroscopically. Under ambient conditions, these clusters catalyzed the silylation of N2 to furnish up to 160 ± 13 equiv of N(SiMe3)3 per 2c (40 equiv per Fe atom) and 183 ± 18 equiv per 3 (31 equiv per Fe atom). With regard to the generation of the reactive species, dissociation of phosphine and hydride ligands from the [Fe4] and [Fe6] clusters was indicated, based on the results of the mass spectrometric analysis on the [Fe6] cluster, as well as the formation of a diphenylsilane adduct of the [Fe4] cluster.

Morphometric comparisons of plant-mimetic juvenile fish associated with plant debris observed in the coastal subtropical waters around Kuchierabu-jima Island, southern Japan.

The general morphological shape of plant-resembling fish and plant parts were compared using a geometric morphometrics approach. Three plant-mimetic fish species, Lobotes surinamensis (Lobotidae), Platax orbicularis (Ephippidae) and Canthidermis maculata (Balistidae), were compared during their early developmental stages with accompanying plant debris (i.e., leaves of several taxa) in the coastal subtropical waters around Kuchierabu-jima Island, closely facing the Kuroshio Current. The degree of similarity shared between the plant parts and co-occurring fish species was quantified, however fish remained morphologically distinct from their plant models. Such similarities were corroborated by analysis of covariance and linear discriminant analysis, in which relative body areas of fish were strongly related to plant models. Our results strengthen the paradigm that morphological clues can lead to ecological evidence to allow predictions of behavioural and habitat choice by mimetic fish, according to the degree of similarity shared with their respective models. The resemblance to plant parts detected in the three fish species may provide fitness advantages via convergent evolutionary effects.

Comparative Allometric Growth of the Mimetic Ephippid Reef Fishes Chaetodipterus faber and Platax orbicularis.

Mimesis is a relatively widespread phenomenon among reef fish, but the ontogenetic processes relevant for mimetic associations in fish are still poorly understood. In the present study, the allometric growth of two allopatric leaf-mimetic species of ephippid fishes, Chaetodipterus faber from the Atlantic and Platax orbicularis from the Indo-Pacific, was analyzed using ten morphological variables. The development of fins was considered owing to the importance of these structures for mimetic behaviors during early life stages. Despite the anatomical and behavioral similarities in both juvenile and adult stages, C. faber and P. orbicularis showed distinct patterns of growth. The overall shape of C. faber transforms from a rounded-shape in mimetic juveniles to a lengthened profile in adults, while in P. orbicularis, juveniles present an oblong profile including dorsal and anal fins, with relative fin size diminishing while the overall profile grows rounder in adults. Although the two species are closely-related, the present results suggest that growth patterns in C. faber and P. orbicularis are different, and are probably independent events in ephippids that have resulted from similar selective processes.

N2 activation by an iron complex with a strong electron-donating iminophosphorane ligand.

A new tridentate cyclopentane-bridged iminophosphorane ligand, N-(2-diisopropylphosphinophenyl)-P,P-diisopropyl-P-(2-(2,6-diisopropylphenylamido)cyclopent-1-enyl)phosphoranimine (NpNPiPr), was synthesized and used in the preparation of a diiron dinitrogen complex. The reaction of the iron complex FeBr(NpNPiPr) with KC8 under dinitrogen yielded the dinuclear dinitrogen Fe complex [Fe(NpNPiPr)]2(µ-N2), which was characterized by X-ray analysis and resonance Raman and NMR spectroscopies. The X-ray analysis revealed a diiron complex bridged by the dinitrogen molecule, with each metal center coordinated by an NpNPiPr ligand and dinitrogen in a trigonal-monopyramidal geometry. The N­N bond length is 1.184(6) Å, and resonance Raman spectra indicate that the N­N stretching mode ν(14N2/15N2) is 1755/1700 cm­1. The magnetic moment of [Fe(NpNPiPr)]2(µ-N2) in benzene-d6 solution, as measured by 1H NMR spectroscopy by the Evans method, is 6.91µB (S = 3). The Mössbauer spectrum at 78 K showed δ = 0.73 mm/s and ΔEQ = 1.83 mm/s. These findings suggest that the iron ions are divalent with a high-spin configuration and that the N2 molecule has (N═N)2­ character. Density functional theory calculations performed on [Fe(NpNPiPr)]2(µ-N2) also suggested that the iron is in a high-spin divalent state and that the coordinated dinitrogen molecule is effectively activated by π back-donation from the two iron ions (dπ) to the dinitrogen molecule (πx* and πy*). This is supported by cooperation between a large negative charge on the iminophosphorane ligand and strong electron donation and effective orbital overlap between the iron dπ orbitals and N2 π* orbitals supplied by the phosphine ligand.

Synthesis, structure and valence-trapping vs. detrapping for new trinuclear iron pentafluoro benzoate complexes: possible recognition of organic molecules by 57Fe Mössbauer spectroscopy.

New mixed-valence trinuclear iron pentafluorobenzoate complexes were synthesized. Their valence-detrapping and/or valence-trapping phenomena were studied by (57)Fe Mössbauer spectroscopy and X-ray crystallography. For [Fe3O(C6F5CO2)6(py)3]·CH2Cl2 (1), a valence-trapped state was observed at low temperatures, while the valence-detrapped state was observed at room temperature. Removal of CH2Cl2 from 1 gives the de-solvated [Fe3O(C6F5CO2)6(py)3] (2) where the valence was trapped at room temperature. The CH2Cl2-free 2 can reversibly absorb and desorb CH3CN; the process was followed by (57)Fe Mössbauer spectroscopy by monitoring valence-trapping and valence-detrapping phenomena. Organic molecules such as benzene, toluene, ethylbenzene, cumene, and xylene are also trapped by 2 and affect the iron valence states. However, small molecules such as H2O and CO2 do not affect the valence-trapped state of 2. Three xylene isomers trapped within the nano-void of 2 were distinguished by (57)Fe Mössbauer spectroscopy at room temperature.

Molecular cloning and expression profile of sex-specific genes, Figla and Dmrt1, in the protogynous hermaphroditic fish, Halichoeres poecilopterus.

The genes folliculogenesis specific basic helix-loop-helix (facor in the germline alpha, Figla) and doublesex and mab-3 related transcription factor 1 (Dmrt1) are female- and male-specific genes that play key roles in sex differentiation. To obtain a better understanding of the molecular mechanisms underlying female-to-male sex change, we cloned the cDNAs of these genes from an ovary and a testis of the protogynus wrasse, Halichoeres poecilopterus. This fish has two isoforms of Dmrt1, Dmrt1a and Dmrt1b, caused by an alternative splicing. The Dmrt1b has an insertion of three nucleotides (CAG) in the open reading frame. Figla and Dmrt1 displayed gonadal-specific expression and abundant in the ovaries and in the testes, respectively. In particular, levels of Figla expression in the ovaries were higher in the spawning season than in the non-spawning season. Once sex change began, Figla mRNA decreased and Dmrt1 mRNA increased with progression of oocyte degeneration and spermatogenesis. These expression levels were maintained until the completion of the sex change. Low Figla and high Dmrt1 were also observed in testes of primary males, which functioned as a gonochoristic male throughout its life span in this wrasse. The results of this study suggest that these genes may regulate the gonadal transition from ovary to testis by the same mechanism as that of formation and maintenance of the primary testis in H. poecilopterus.

Interaction of synthetic sulfate green rust with antimony(V).

Green rusts (GRs), which are mixed ferrous/ferric hydroxides, occur in many suboxic soils and sediments and are thought to play an important role in the fate and transport of many inorganic contaminants. In this study, the interaction of Sb with sulfate GR (GRSO4) was investigated using multitechnique approaches such as X-ray absorption fine structure (XAFS), XRD, and BET analyses. XANES analyses show that the oxidation states of Sb(V) sorbed on GRSO4 is dominantly Sb(V), suggesting that GRSO4 does not work as a strong reductant in the system of the present study. The sorption experiment EXAFS, and XRD results suggested that there are two bonding modes for Sb(V) sorption on GRSO4, (i) the sorption to edge sites with inner-sphere complex and (ii) to interlayer surface with outer-sphere complex. In addition, it was found that fraction (i) is dominant for Sb(V) sorption on GRSO4. The transformation of "metastable" GRSO4 was inhibited by the presence of Sb(V). The transformed products of GRSO4, such as magnetite and Fe(OH)2, have larger surface areas and higher capacities as adsorbent for Sb(V) than GRSO4, and the fraction of the transformed product largely affectsthe distribution of Sb between water and solid, a mixture of GRSO4, magnetite, and Fe(OH)2.

Examination of the ability of gonadal sex change in primary males of the diandric wrasses Halichoeres poecilopterus and Halichoeres tenuispinis: estrogen implantation experiments.

Primary males that function as males throughout their lives are often found among protogynous fishes such as wrasses and parrotfishes. However, the issue of whether the sexuality of primary males involves gonochorism or hermaphroditism remains uncertain. To clarify this, we implanted estradiol-17beta (E2) into the body cavities of primary males of two protogynous wrasses, Halichoeres poecilopterus and Halichoeres tenuispinis. At 51-63 days after implantation, primary males with E2 treatment in both wrasses were observed to develop ovarian tissues. These results suggest that primary males of Halichoeres wrasses potentially have the ability to change sex and that estradiol-17beta is related to gonadal transitions in primary males.

Abiotic reduction of antimony(V) by green rust (Fe(4)(II)Fe(2)(III)(OH)(12)SO(4).3H(2)O).

Green rust (Fe(4)(II)Fe(2)(III)(OH)(12)SO(4).3H(2)O) is an intermediate phase in the formation of iron (oxyhydr)oxides such as goethite, lepidocrocite, and magnetite. It is widely considered that green rust occurs in many soil and sediment systems. Green rust has been shown to reduce sorbed Se(VI), Cr(VI), and U(VI). In addition, it is also reported that green rust does not reduce As(V) to As(III). In this study, we have investigated for the first time the interaction between Sb(V) and green rust using XAFS and HPLC-ICP-MS. Most of the added Sb(V) was adsorbed on green rust, and Sb(III), a reduced form, was observed in both solid and liquid phases. Thus, it was shown that green rust has high affinity for Sb(V), and that Sb(V) was reduced to more toxic Sb(III) by green rust despite the high stability of the Sb(V) species even under reducing condition as reported in previous studies. Therefore, green rust can be one of the most important reducing agents for Sb(V), which can influence the Sb mobility in suboxic environments where green rust is formed.