The larval head morphology of Xyela sp. (Xyelidae, Hymenoptera) and its phylogenetic implications

Larval head structures of Xyela sp. are described in detail. The characters are compared to conditions found in larvae of other groups of Hymenoptera and Endopterygota. Like other symphytan larvae the immature stages of Xyelidae are mainly characterized by presumably plesiomorphic features of the head. The head sutures are well developed and all parts of the tentorium are present. The labrum is free and a complete set of labral muscles is present. The maxillae are in a retracted position. In contrast to other hymenopteran larvae Xyela possesses a clypeofrontal suture, a comparatively long antenna and three well‐developed antennal muscles. Apomorphic features of Xyela are the absence of muscles associated with the salivarium and the complete absence of Musculus craniocardinalis. A clade comprising Orussidae and Apocrita is supported by the unsegmented maxillary and labial palps and the absence of the lacinia. Six potential autapomorphies for the Hymenoptera were revealed: (1) the caudal tentorial apodeme, (2) the bifurcated tendon of Musculus craniomandibularus internus, (3) the lateral lobe of the cardo, (4) the origin of M. tentoriohypopharyngalis from the posterior head capsule, (5) the exceptionally strong prepharyngo‐pharyngeal longitudinal muscle and (6) the longitudinal muscle of the silk press. The maxillolabial complex, the vestigial M. craniocardinalis and a distinctly developed labio‐hypopharyngeal lobe bearing the opening of the salivary duct are potential synapomorphies of Hymenoptera and Mecopterida. The globular, orthognathous head capsule, the modified compound eyes, the occipital furrow and the X‐shaped tentorium are features with unclear polarity shared by Hymenoptera and Mecoptera.     

Complexes of oxomethoxovanadium(V) with tridentate thiobenzhydrazide based Schiff bases

A family of complexes containing the {VO(OMe)}²⁺ motif with the O,N,S-donor Schiff bases (H₂tbhsR) derived from thiobenzhydrazide and 5-substituted salicylaldehydes has been reported. Reactions of [VO(acac)₂] with H₂tbhsR in methanol provide the complexes having the general formula [VO(OMe)(tbhsR)] (R = H, OMe, Cl, Br and NO₂) in 40-53% yields. Microanalytical, various spectroscopic (IR, UV-Vis and NMR) and electrochemical measurements have been used for the characterization of the complexes. All the complexes are redox active and display a near reversible metal centred reduction in the potential range 0.20-0.47 V (versus Ag/AgCl). The trend in these potential values reflects the polar effect of the substituent on the salicylidene fragment of tbhsR²⁻. The X-ray crystal structures of all the complexes have been determined. In each of the complexes where R = H, OMe, Cl and Br, the metal ion is in a distorted square-pyramidal O₃NS coordination sphere assembled by the O,N,S-donor tbhsR²⁻, the methoxo and the oxo groups. The complex where R = NO₂, crystallizes as a hexacoordinated species due to coordination of a methanol O-atom at the vacant sixth site. The bond parameters associated with the metal ions and the physical properties of the complexes are consistent with the +5 oxidation state of the metal ion in all the complexes. Scrutiny of crystal packing reveals dimeric, one-dimensional and two-dimensional self-assembled structures via intermolecular C-H?O and O-H?O interactions. The two-dimensional network contains the cyclic tetramer of methanol.     

Presence Of Nemathecia In Parachaetetes Asvapatii Pia, 1936 (Rhodophyta,Gigartinales?): Reproduction In ‘Solenoporaceans’ Revisited

Parachaetetes asvapatii is a very common algal species in the Palaeogene deposits of the Tethyan realm and has been considered as a member of the heterogeneous family Solenoporaceae. This attribution is exclusively based on features of the vegetative tissue, since no reproductive structures have ever been recovered. However, detailed analysis of Late Cretaceous–Eocene material from Turkey has revealed nemathecia-like structures in one specimen attributable to P. asvapatii . These nemathecia are small wart-like structures protruding on the thallus surface that formed by enlargement of the most peripheral cells of the plant. Nemathecia only occur in three families of the order Gigartinales (Rhodophyta): Rhizophyllidaceae, Peyssonneliaceae and Polyideaceae. Since reproductive structures are stable characters, the presence of nemathecia leads us to tentatively refer P. asvapatii and related species (probably Elianella elegans ) to the Gigartinales.     

Biogenic Isoprene (A Review)

Biogenic isoprene was discovered in the mid-1950s as a component of volatile substances emitted from leaves. In plant species emitting isoprene under illumination, this process is closely related to photosynthesis. Thus, a photobiological phenomenon termed isoprene effect or isoprene emission (IE) was discovered. Subsequent studies showed that leaves are capable of releasing isoprene also in darkness, though at a rate two orders of magnitude lower than that in illuminated leaves. It is presently known that the isoprene is emitted not by all plant species from various taxonomic groups, whereas the dark release of isoprene occurs in cells of all living organisms. This review presents a brief historical account of studies dealt with IE. A special emphasis is placed on the roles of light as an energy source and of CO₂ as a carbon source; these factors create the energy–metabolite flow that runs through the green photosynthesizing cell. The data available suggest that IE can be considered as a manifestation of excretory function of the leaf. An attempt is made to describe IE from the standpoint of thermodynamics of irreversible processes. It is shown that the cell represents a dissipative structure whose organization and stability is provided by irreversible processes running far from equilibrium. General view on isoprene emission is that it results from regulated conversions of carbon and free energy in a series of photosynthetic reactions under stressful conditions caused by CO₂ deficit inside illuminated autotrophic cells. This stress generates the energy overflow, far in excess of the energy-consuming capacity. The necessity of discharging this energy excess is dictated by the fact that the living cell is a dissipative structure.     

The spermatozoon of Eurasian murine rodents: Its morphological diversity and evolution

The murine rodents are the most speciose subfamily of mammals. Here the morphology of the spermatozoon, as determined by scanning and transmission electron microscopy of representative species from four Eurasian clades, is described. Much interspecific variability in all components of the spermatozoon was found to occur, although most species have a bilaterally flattened sperm head with a single apical hook of variable length and orientation. Ultrastructural observations indicate that this apical hook invariably contains a nuclear projection as well as a large extension of the subacrosomal cytoskeleton, as a perforatorium rostrally, and a complex asymmetrical acrosomal extension. These spermatozoa also have relatively long tails that are attached to the lower concave surface of the sperm head. Uniquely, in species in the Apodemus clade, the apical hook is orientated caudally. In a few species a highly derived sperm head morphotype that does not contain an apical hook is present. These sperm heads vary in morphology from being globular in two species of Bandicota, to bilaterally flattened and paddle-shaped in Tokudaia and Micromys. In spermatozoa of the latter two genera the subacrosomal cytoskeleton, which is less extensive than in species with a hooked sperm head, forms an apical extension, but that is not the case in Bandicota. In all species where the sperm head lacks an apical hook the acrosome is more symmetrical. The sperm tail is much shorter in these species, with attachment to the head occurring on the ventral surface in Tokudaia and basal in Micromys and the two species of Bandicota. As the sperm head morphotype with a complex apical hook is present in all the major clades of murine rodents, it is likely to be a plesiomorphic character within each of these clades, with the nonhooked sperm heads, which vary greatly in structure between species of the different lineages, probably being independently derived. The ultrastructural organization of the sperm head of Bandicota, but not those of Micromys or Tokudaia, suggest divergence in some of the morphological events associated with sperm-egg interaction at the time of fertilization.     

Self-assembly of three hetero- and homopolynuclear cyanide bridged complexes of Fe-Cu and Cu: hydrothermal syntheses, structural characterization and properties

Reaction of Cu^II, K₃ [Fe(CN)₆] and bidentate diimine ligands by hydrothermal synthesis under different conditions affords one novel heteronuclear Fe^II-Cu^I complex, (bipy = 2,2′-bipyridine), and two homonuclear Cu^I complexes, [Cu^I(μ-CN)(bipy)]_n (2) and (3) (phen = 1,10-phenanthroline). Although all the three complexes are 1D cyanide bridged helical chains, they have different helicoids of pseudo-square, pseudo-trigonal and head-to-head bistrigonal for 1, 2 and 3, respectively. The structure of 1 is extended to 2D hexagonal meshed layers by the hydrogen bonding between terminal cyanides and lattice water molecules, which also contain π-π interactions between adjacent sheets. Cu^I ions in 1 are distorted trigonal planar coordinated by two bridging cyanides and one terminal cyanide, whereas that in 2 and 3 are pseudo-tetrahedral coordinated by two bridging cyanides and two N atoms of a diimine. Both the latter homometallic polymers exhibit similar chain structure, and these chains are close packed with their six adjacent chains in a parallel fashion along the c-axis to form a honeycomb network. It should be noted that complex 1 is the first cyanide bridged Fe^II-Cu^I complex of helical chain structure. The spectroscopic properties of complexes 1-3 have also been investigated.     

Crystal structure and magnetic properties of lanthanide-trans-2-butenoate polymers (Ln = La, Pr, Dy, Ho)

Four lanthanide coordination polymers formulated as {[La₃L₉(H₂O)₃]EtOH · H₂O}_n1, {[Pr₂L₆(H₂O)₂]HL · H₂O}_n2, {[Dy₂L₆(H₂O)]0.5HL · H₂O}_n3 and {[Ho₂L₆(H₂O)]0.5HL · H₂O}_n4 and HL = trans-2-butenoic acid have been synthesized from the corresponding pure lanthanide oxide and HL acid in water at pH 3. The compounds were characterized by chemical analysis, IR spectroscopy, thermogravimetry, variable-temperature magnetic susceptibility and single crystal X-ray diffraction studies. A common feature in these materials is the presence of two differentiated lanthanide nodes linked by carboxylates into extended chains. These are further connected by inter- and intra-molecular hydrogen-bonds involving ligand and solvate molecules. Weak ferromagnetic interactions appear to be operative in the Dy material.     

Oxime-functionalized diazamesocyclic derivates and their metal complexes: Effect of the ligand backbones and anions on the generation of novel monomeric and mono-μ-Cl dimeric Cu complexes

Two oxime-functionalized diazamesocyclic derivates, namely, N,N′-bis(acetophenoneoxime)-1,4-diazacycloheptane (H₂L¹) and N,N′-bis(acetophenonoxime)-1,5-diazacyclooctane (H₂L²), have been prepared and characterized. Both ligands (obtained in the hydrochloride form) can form stable metal complexes with Cu^II and Ni^II salts, the crystal structures of which were determined by X-ray diffraction technique. The reactions of H₂L¹ with Cu(ClO₄)₂ and Ni(ClO₄)₂ afford a penta-coordinated mononuclear complex [Cu(H₂L¹)Cl] · ClO₄ (1) and a four-coordinated monomeric [Ni(HL¹)] · ClO₄ (2), in which the ligand is monodeprotonated. The ligand H₂L² also forms a quite similar mononuclear [Ni(HL²)] · ClO₄ complex with Ni(ClO₄)₂, according to our previous work. However, reactions of different Cu^II salts [Cu(ClO₄)₂, CuCl₂ and Cu(NO₃)₂ for 3, and CuSO₄ for 4] with H₂L² in the presence of NaClO₄ yield two unusual mono-μ-Cl dinuclear Cu^II complexes [Cu₂(HL²)₂Cl] · (ClO₄) (3), and [Cu₂(H₂L²)(HL²)Cl] · (ClO₄)₂ · (H₂O)(4). These results indicate that the resultant Cu^II complexes (1, 3 and 4) are sensitive to the backbones of diazamesocycles and even auxiliary anions.     

Novel polynuclear thallium thiolates with cage structures

Yellow thallium(I)-tetra(2-butanethiolato)-thallium(III) Tl[Tl(SC₄H₉)₄] (1) crystallizes from a solution of thallium(I) carbonate and 2-butanethiol in DMF after heating under reflux in air. In the crystal structure (space group: , a = 8.941(3) Å, b = 11.078(4) Å, c = 13.458(4) Å, α = 70.81(3)°, β = 83.65(3)°, γ = 74.78(3)°, Z = 2) regular, TlS₄ tetrahedra are bridged by thallium(I) atoms to an one-dimensional framework. The thallium(I) atoms are in fivefold distorted coordination and are linked to four further TlS₄ tetrahedra. The resulting Tl₄(S-Bu)₈ units consist of two face-sharing Tl₃S₄ defect cubane entities.TlSC₃H₇ (2) was obtained from a solution of thallium(I) carbonate and 2-propanethiol in DMF after heating under reflux in air. The crystal structure (space group C2/c, a = 22.501(5) Å, b = 10.360(2) Å, c = 12.760(3) Å, β = 107.92(2)°, Z = 16) contains novel [Tl₄(SPr)₅]⁻ units which are linked via thallium atoms to one-dimensional molecular chains running parallel to [0 0 1].     

Rhodium(I) complexes with phosphinooxathiane (POT) and phophinooxazolidine (POZ) ligands: the crystal structures of [(POT)Rh(CO)Cl] and [(POZ)Rh(CO)Cl]

The reactions of two equivalents of the ligands POT or POZ with one equivalent of the rhodium complex [Rh(μ-Cl)(CO)₂]₂ afford the complexes [(POT)Rh(CO)Cl] (1) and [(POZ)Rh(CO)Cl] (2), respectively. The crystal structures of both complexes have been determined showing the rhodium centers to be into slightly distorted square planar environments. Preliminary screening of the catalytic systems POT/Rh and POZ/Rh in the asymmetric hydroformylation of styrene has been carried out.