Pseudooneotodusi a histological study of an Ordovician to Devonian vertebrate lineage

Detailed histological investigations have shed new light on the nature of Pseudooneotodus Drygant, 1974 (?Arenig/ljanvirn - Emsian). The genus has generally been interpreted as a conodont and is represented by squat phosphatic cones. These conodont dements show a differentiation into a lamellar cap, indistinguishable from vertebrate enamel, which is underlain by a spherulitic basal tissue with several characters indicative of dentine. The presence of these two issues in the elements of a conodont argues persuasively for the. vertebrate classification of the cladc, and illustrates that at least some conodonts have a hard tissue complex which is histologically indistinguishable from those of other primitive vertebrates. These observations have potentially important implications for conodont classification and the stratigraphic first appearances of vertebrate hard tissues.     

Preliminary assessment of the use of electron backscatter diffraction (EBSD) in conodonts

Pérez‐Huerta, A., Cusack, M. & Méndez, C.A. 2011: Preliminary assessment of the use of electron backscatter diffraction (EBSD) in conodonts. Lethaia, Vol. 45, pp. 253–258. Conodonts are extensively used as ‘geochemical tools’ in palaeoenvironmental reconstructions in Palaeozoic and Triassic strata. The retention of a primary geochemical signal is substantially dependent on the ultrastructural integrity and crystallinity after diagenesis. Direct assessments of the preservation potential of the polycrystalline matrix are scarce with the exception of the application of transmission electron microscopy (TEM). The possible application of electron backscatter diffraction (EBSD) is introduced for well‐preserved Pennsylvanian platform conodont elements as a novel in situ technique based on successful previous results for biogenic carbonates. EBSD shows the presence of no diffraction in central regions of all studied elements of Idiognathodus and Adetognathus, with possible implications for geochemistry analysis. The absence of diffraction could be attributed to the existence of an amorphous phase, water (+OH) or a process of hypocalcification related to the development of ‘growth cavities’ in the lamellar crown tissue. Overall results indicate the suitability of using EBSD to extract crystallographic information from conodonts and potentially for other apatite (micro‐) fossils. □Conodont, diagenesis, EBSD, geochemistry, Pennsylvanian.     

Intranuclear crystals in plant embryo cells

Summary Two types of protein crystal occur in the nuclei of all tissues of the embryos of Fraxinus excelsior and F. americana. Small crystals about 0.1 micron in diameter and large crystals from 1–4 microns in diameter are described.     

Euconodont hard tissue: preservation patterns of the basal body

Conodont elements, consisting of crown and basal tissue are the well-known fossilized hard parts of Conodonta (extinct marine chordates), but the taphonomic processes leading to decomposition or remineralization of the basal tissue are not well understood. Here we focus on the taphonomy of basal tissue, reviewing the published record and describing new material from Asia and Europe (248 occurrences globally). These include crown and basal tissue in conjunction, and isolated basal bodies showing different stages of preservation. Some isolated specimens resemble phosphate rings similar to those assigned to Phosphannulus universalis. High-resolution biostratigraphy indicates that the lamellar type of conodont basal tissue is found in all facies and depositional environments. Other basal tissue types, described in the literature as tubular, mesodentine, spherulitic or lamellar with canalules, are limited to the early Palaeozoic and found exclusively in siliciclastic deposits (with the exception of spherulitic tissue). Although the stratigraphic record of basal tissue spans the range of Euconodonta (Cambrian–Triassic), this study shows that most of the isolated plate and ring-like structures are derived from early Palaeozoic coniform conodonts. Basal tissue of platform-type elements has a much more fragile shape and is therefore rarely preserved as a recognizable isolated unit.     

Overgrowths of large authigenic apatite crystals on the surface of conodonts from Cantabrian limestones (Spain)

Conodonts from the middle to upper Paleozoic limestones of the Cantabrian zone commonly show apatite overgrowths. A large crystal microtexture observed under the SEM corresponds to local rims of euhedral to subhedral apatite crystals, which were preceded by the neoformation of smaller crystals. Four types of this microtexture (blocky, columnar, fan, and denticular) are described on different areas of the oral surface of conodonts, whereas dissolution features may be present in the basal cavity area. The distribution of these types of microtexture in different areas of conodont morphology suggests a general trend to neocrystallization, where crystal size increases towards the top of the conodont ornamentation and a chemical gradient controls the crystalline growth. This arrangement is widely related to the surface morphology and to the general conodont histology. The large crystal microtexture grows during early diagenesis from near surface to moderate burial and is linked to the known secondary apatite cement present in natural fused clusters of conodonts. The features described here are also compared to microtextures developed on conodonts during low- to medium-grade metamorphic conditions, where phosphate in solution is available.     

Paramoeba invadens n. sp. (Amoebida,Paramoebidae), a Pathogenic Amoeba from the Sea Urchin,Strongylocentrotus droebachiensis,in Eastern Canada1

Paramoeba invadens n. sp. is described from sea urchin tissues and from culture. Amoebae are 20–40 μm in length with an irregular hyaline region producing short subpseudopodia. One parasome per cell is present. The parasome is bipolar with basophilic, Feulgen-positive poles and a Feulgen-negative median segment. The fine structure of the parasome resembles those in other species of Paramoeba and the surface of the amoeba is plain with no hairs or scales. Amoebae dislodged from tissues often adopt a semifloating form; floating forms have been seen in culture. Amoebae circulate within lumina of the water vascular system and can migrate readily into or out of tissues.     

Sieve-element plastids and evolution of monocotyledons, with emphasis on Melanthiaceae sensu lato and Aristolochiaceae-Asaroideae, a putative dicotyledon sister group

Monocotyledons are distinguishable from dicotyledons by their subtype P2 sieve-element plastids containing cuneate protein crystals, a synapomorphic character uniformly present from basal groups through Lilioids to Commelinoids. The dicotyledon generaAsarum andSaruma (Aristolochiaceae-Asaroideae) are the only other taxa with cuneate crystals, but their sieveelement plastids include an additional large polygonal crystal, as is typical of many eumagnoliids. New investigations in Melanthiaceae s.l. revealed the same pattern (polygonal plus cuneate crystals) in the sieve-element plastids ofJaponolirion osense (Japonoliriaceae/Petrosaviaceae), ofHarperocallis flava, Pleea tenuifolia, andTofleldia (all: Tofieldiaceae). InNarthecium ossifragum a large crystal, present in addition to cuneate ones, usually breaks up into several small crystals, whereas inAletris glabra andLophiola americana (Nartheciaceae) and in all of the 15 species studied and belonging to Melanthiaceae s.str. only cuneate crystals are found. Highresolution TEM pictures reveal a crystal substructure that is densely packed in both cuneate and polygonal forms, but in Tofieldiaceae the polygonal crystals stain less densely, probably as a result of the slightly wider spacing of their subunits. The small crystals ofNarthecium are “loose”; that is, much more widely spaced. Such “loose” crystals are commonly found in sieve-element plastids of Velloziaceae, present there in addition to angular crystals, and together with cuneate crystals in a few Lilioids and many taxa of Poales (Commelinoids). Ontogenetic studies of the sieve elements ofSaruma, Aristolochia, and several monocotyledons have shown that in their plastids cuneate crystals develop very early and independent from a polygonal one present in some taxa. Therefore, a conceivable particulation of polygonal into cuneate crystals is excluded. Consequently, mutations of some monocotyledons that contain a lone, large, polygonal crystal in their sieve-element plastids are explained as the result of a complex genetic block. The total result of all studies in sieve-element plastids suggests thatJaponolirion and Tofieldiaceae are the most basal monocotyledons and that Aristolochiaceae are their dicotyledon sister group.     

红豆草中含晶细胞的形态学研究

红豆草（Ｏｎｏｂｒｙｃｈｉｃｖｉｃｉａｅｆｏｌｉａｓｃｏｐ．）植株的所有器官中都分布有含晶细胞,其结晶的类型主要为棱晶,此外还有砂晶。在营养器官中,含棱晶的细胞主要分布在维管组织之中或外围。横切面上,棱晶则几至几十块纵列成行存在,且常伴生于韧皮纤维旁,但每块棱晶各有一分室隔开;在茎的表皮下偶有与大型粘液细胞伴生的砂晶。花萼的表皮中偶有棱晶,花瓣表皮及雄蕊药隔中有砂晶;子房壁内表皮下一层细胞逐渐发育成含棱晶的连续细胞,同时子房维管组织中也形成大量棱晶。分析表明,结晶成分为草酸钙。     

OCCURRENCE,TYPE, AND LOCATION OF CALCIUM OXALATE CRYSTALS IN LEAVES AND STEMS OF 16 SPECIES OF POISONOUS PLANTS

Crystals in 16 species of poisonous plants growing naturally in Saudi Arabia were studied with light microscopy. Three types of crystals were observed: druses, prismatics, and crystal sand. Raphides and styloids were not observed in any of the species studied. Druses occur more frequently in the leaf midrib and in the cortex and pith of the stem. In contrast, crystal sand and prismatic crystals are rare and occur in the leaf, intercostal lamina, and in the vascular tissues. The preliminary results show the absence of the three types of calcium oxalate crystals in the stem and leaf of seven species: Ammi majus L., Anagallis arvensis L., Calotropis procera Ait., Citrullus colocynthis (L.) Schard, Euphorbia peplis L., Hyoscyamus muticus L., and Solarium nigrum L., and the presence of druses, prismatic crystals, and crystal sand either in the leaf and stem or in the leaves or stems of nine species: Anabasis articulata (Forssk.) Moq. in DC., Chenopodium album L., Convolvulus arvensis L., Datura stramonium L., Nerium oleander L., Ricinus communis L., Rumex nervosus Vahl., Pergularia tomentosa L., and Withania somnifera (L.) Dun. in DC. These observations indicate that there is no apparent relationship between the distribution of calcium oxalate crystals and the toxic organs of the plants, and supports the view that the presence of calcium oxalate crystals may not be related to plant toxicity.     

香樟叶肉含晶细胞季节变化研究

为探讨香樟(Cinnamomum camphora)叶肉含晶细胞超微结构的季节变化,阐明香樟叶肉中草酸钙晶体在春夏秋冬的变化规律。该研究以多年生香樟(C. camphora)叶片为材料,分别于春夏秋冬四个季节露地取样,制作超薄切片,用透射电子显微镜(TEM)观察叶肉含晶细胞超微结构的变化。结果表明:春季时香樟叶肉中只有少数细胞有草酸钙晶体,数量较少,晶体结构多为柱状晶、方晶; 夏季时香樟叶肉细胞中随机分布于液泡的草酸钙晶体明显比春季的数量多、体积大、形态丰富,晶体多为柱状晶、方晶、针晶、簇晶; 秋季时香樟叶肉细胞草酸钙晶体和夏季的类似,数量较多,形态多样,以方晶和柱状晶针晶为主,伴有晶簇; 冬季时香樟叶肉含晶细胞晶体形态为柱状晶、方晶、针晶,数量比夏季和秋季的数量略有减少。该研究结果表明在一年四季中香樟叶肉细胞液泡中均有草酸钙晶体结构存在。     

Conodont affinity of the enigmatic Carboniferous chordate Conopiscius

Conopiscius shares V-shaped myomeres with the co-occurring conodont Clydagnathus but instead of a complex oral apparatus it has only a single pair of conical elements, and structures resembling scales are associated with its myomeres. Moreover, the coarsely crystalline crown tissue typical for conodonts has not been identified in the Conopiscius elements, which show only a finely lamellar skeletal tissue. The gap between conodonts and Conopiscius may be filled by isolated elements of similar morphology and structure occurring in the Late Devonian. They reveal a very thin external layer developed mostly at the tooth tip and resembling conodont crown tissue. The pulp cavity is partially filled with layered or spherulitic phosphatic tissue of the kind known also in conodonts (basal filling tissue) and early vertebrates (lamellin). Conodont elements of similar morphology and representing uni-membrate oral apparatuses have not been previously reported from the Devonian or Carboniferous but occur near the Cambrian–Ordovician transition ( Proconodontus ) and in the Late Permian ( Caenodontus ). It is proposed that Conopiscius represents a mostly cryptic conodont lineage extending from the Early Ordovician to the Permian, instead of being directly related to the agnathans.     

Middle Ordovician cephalopod biofacies and palaeoenvironments of Baltoscandia

During the Middle Ordovician cephalopods became an important part of the macrofauna of the Baltoscandian carbonate platform. The earliest cephalopod abundance peak was reached during the early Darriwilian, within the Kunda Stage Yangtzeplacognathus crassus and Lenodus pseudoplanus conodont zones. In sediments of this time interval large orthoconic cephalopods often occur in masses with more than one specimen per square‐meter on bedding surfaces. The assemblages are characterized by the strong dominance of often large endocerids. In proximal depositional settings coiled tarphycerids and other cephalopod groups are an important additional component. In the most distal settings orthocerids are the most important secondary component. Correspondence Analysis of assemblages throughout Baltoscandia revealed three distinct biofacies, which here are termed Orthocerid, Proterovaginoceras and Anthoceras Biofacies, respectively. The biofacies reflect differences in depth and proximity to the shoreline and are consistent with the Baltoscandian Confacies Belts. Spatial changes in absolute abundance and taxonomic composition indicate increased original cephalopod population densities and habitat expansion within the Y. crassus and L. pseudoplanus conodont zones. A nearly coeval abundance peak in a similar facies in South China indicates supraregional causes of the mass occurrence, probably reflecting a globally increased nutrient availability in the water column during the Darriwilian.     

Further studies of the sieve-element plastids of theCaryophyllales includingBarbeuia,Corrigiola, Lyallia,Microtea, Sarcobatus,andTelephium

The sieve-element plastids of 69 species of theCaryophyllales were investigated by transmission electron microscopy. All contained the specific subtype-P3 plastids characterized by a peripheral ring of protein filaments. The presence or absence of an additional central protein crystal and their shape being either polygonal or globular as well as the average sizes of the sieve-element plastids are useful features in the characterization of some families.—Barbeuia contains sieve-element plastids that confirm its placement within thePhytolaccaceae. Lyallia differs fromHectorella by including small starch grains in their sieve-element plastids, which otherwise by their globular crystals negate a closer connection to theCaryophyllaceae. The lack of a central protein crystal in its form-P3fs plastids placesMicrotea best within theChenopodiaceae. Sarcobatus, a so far uncontested member of theChenopodiaceae, contains form-P3cf plastids, i.e., including a central crystal not found elsewhere in this family.Telephium andCorrigiola, shifted back and forth betweenMolluginaceae andCaryophyllaceae, have form-P3cf(s) plastids with a polygonal crystal which favor their placement within theCaryophyllaceae.     

The effect of adenosine triphosphate,magnesium chloride and phospholipids on crystal formation in the demineralized shell-repair membrane of the snail,Helix pomatia L.

Summary The effect of adenosine triphosphate (ATP), magnesium chloride (MgCl₂) and phospholipids on the calcium-binding activity and crystal formation within the decalcified shell-repair membrane of the snail, Helix pomatia, was studied in vitro. The application of ATP produced a characteristic dual effect on calcification: (1) It strongly inhibited the formation of inorganic calcium carbonate (CaCO₃) crystals. (2) It stimulated the development of organic crystalline bodies and induced deposition of amorphous calcium carbonate. The demineralized shell-repair membranes became white and rigid after incubation for 7 days in the medium containing 1.0mM ATP. The inhibitory effect of Mg²⁺ on CaCO₃ crystal formation was diminished by reduction of the concentration of MgCl₂ in the incubation solution. Thus, after incubation for only 24h, 1.0mM MgCl₂ promoted the formation of birefringent CaCO₃ crystals within the repair membranes. The principal effect of phospholipids on the demineralized shell-repair membrane was stimulatory, but after application of phospholipids to the medium, the formation of crystals proceeded slowly. The very large, composite crystals that were formed within the repair membranes showed strong birefringence. In all cases the development of the crystals and the organic crystalline bodies occurred in close vicinity to the amoebocytes. The role of ATP, MgCl₂ and phospholipids in the recalcification of shell-repair membrane is discussed.The author wishes to thank Mrs. E. Hellmén for valuable technical assistance     

The effect of carbonic anhydrase,urea and urease on the calcium carbonate deposition in the shell-repair membrane of the snail,Helix pomatia L.

Summary The effect of carbonic anhydrase (CA), urea and urease on the CaCO₃ deposition in the shell-repair membrane of the snail, Helix pomatia, was studied by injection of CA separately or in combination with urease. This treatment resulted in increased deposits of CaCO₃ and apparent crystal formation within the shell-repair membranes compared with those of the controls. The reactions to CA combined with urea were not uniform. Formation of organic crystalline structures and dendritic spherulites was observed in some of these membranes, whereas the deposition of CaCO₃ crystals was suppressed. Administration of urea alone inhibited the formation of large CaCO₃ crystals, whereas urease stimulated this process. The reaction of young snails was greater compared to adults. The membranes of young snails contained tighly packed, small CaCO₃ crystals and organic crystalline structures, which indicated increase of the calcifying centra and their successive mineralization. The results support the assumption that carbonic anhydrase and urease enhance the rate of calcium carbonate deposition and crystal formation in Helix pomatia.     

Testing microstructural adaptation in the earliest dental tools

Conodont elements are the earliest vertebrate dental structures. The dental tools on elements responsible for food fracture—cusps and denticles—are usually composed of lamellar crown tissue (a putative enamel homologue) and the enigmatic tissue known as ‘white matter’. White matter is unique to conodonts and has been hypothesized to be a functional adaptation for the use of elements as teeth. We test this quantitatively using finite-element analysis. Our results indicate that white matter allowed cusps and denticles to withstand greater tensile stresses than do cusps comprised solely of lamellar crown tissue. Microstructural variation is demonstrably associated with dietary and loading differences in teeth, so secondary loss of white matter through conodont phylogeny may reflect changes in diet and element occlusal kinematics. The presence, development and distribution of white matter could thus provide constraints on function in the first vertebrate dental structures.     

The growth of large single crystals of lysozyme

If protein single crystals larger than those suitable for x-ray analysis are obtained, various spectroscopic, thermal, mechanical, and electrical measurements become possible. To understand the factors governing the crystal size, tetragonal lysozyme crystals were grown in batches at 15°C from solutions of different protein and salt concentrations between pH 4–7. The number and size of the crystals, and the protein concentration remaining in the supernatant, varied markedly with the initial salt amount, pH, and cation species, but large crystals always grew when the initial protein concentration (P) was in a narrow range of 2.5–3 times the crystal solubility (S). It was also shown (1) that the period before the first crystals appeared (D) varied as D ∝ (P/S)^?n, where n ? 5, and (2) that many previous experiments used more supersaturated solutions than the optimal ones thus determined. The reason why large crystals grow only from moderately supersaturated solutions is discussed. The crystal size of the orthorhombic form grown at 40°C was less sensitive to pH and P than the tetragonal form. An effort to measure D and the solubility at 40°C revealed many differences between the two crystal forms, which we ascribe to different interactions to promote crystallization.     

Factors Affecting Formation of Large Calcite Crystals (≥1 mm) in Bacillus subtilis 168 Biofilm

B4 is the most common medium used in general organomineralization studies and has been used to assay or to characterize mineral precipitation potential. In an exercise for the optimization of the laboratory conditions of crystal precipitation in vitro, we used Bacillus subtilis 168 as a type strain and its isogenic mutants. While literature is mainly focused on observing generic precipitation, we investigated the requirement to obtain large crystals (≥1 mm), which could be advantageous in wide-ranging implications for bioconsolidation of soil, sand, stone, and cementitious materials. Calcite crystals are visible on B4 agar plates within 7 days at 37°C after inoculum of B. subtilis 168 strain. In this study, we show that to form large crystals with a diameter ≥1 mm several conditions must be met: i) Reduced amount of B4 medium into the Petri plate improve crystal formation. 55 mm Petri plates contained only 4 ml of B4 agar medium reached a plateau in 6 days at 37°C. High moisture and presence of water condense would decrease crystal formation. ii) Inoculation of cells using a rod instead of a circular shaped spot. When the same number of B. subtilis cells was streaked, rod-shape biofilm significantly fostered crystal precipitation, while spot-shape prevented precipitation. iii) When more than one biofilm is present within the same plate, mutual interactions can affect precipitation in each biofilm. iv) Spherical nucleation sites are identified as initial step during the formation of large calcite crystal.     

Crystal types and their distribution in the bark of African genistoid legumes (Fabaceae tribes Sophoreae,Podalyrieae, Crotalarieae and Genisteae)

The occurrence and distribution of seven crystal types in 114 bark samples from 25 genera and 91 species, representing all four tribes of African genistoid legumes, are reported. The seven types are prismatic, druse (including irregular crystal clusters), navicular (including truncated navicular, here reported for the first time), spherical crystal cluster, styloid, crystal sand and acicular crystals in sheaf‐like aggregates. Unlike most studies, the elemental composition of the crystals was examined using X‐ray microanalyses. With the exception of acicular crystals, all crystals showed the typical peaks of calcium (sometimes accompanied by small amounts of magnesium). Acicular crystals in sheaf‐like aggregates were composed only of carbon and oxygen, indicating that they are organic and precipitate during drying or after fixation in alcohol. These crystals are found only in the two early‐diverging lineages of Podalyrieae (Cyclopia and Virgilia+Calpurnia clades), consistent with the phylogenetic pattern in the tribe (indicating a secondary loss). Navicular crystals are restricted to Podalyrieae and Crotalarieae. Prismatic crystals in bark are proposed to be the ancestral condition, with multiple losses (or reversals) in Podalyrieae, Crotalarieae and Genisteae. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 178 , 620–632.     

Cell and calcium oxalate crystal growth is coordinated to achieve high-capacity calcium regulation in plants

Summary Crystal idioblasts are cells which are specialized for accumulation of Ca²⁺ as a physiologically inactive, crystalline salt of oxalic acid. Using microautoradiographic, immunological, and ultrastructural techniques, the process of raphide crystal growth, and how crystal growth is coordinated with cell growth, was studied in idioblasts ofPistia stratiotes. Incorporation of⁴⁵Ca²⁺ directly demonstrated that, relative to surrounding mesophyll cells, crystal idioblasts act as high-capacity Ca²⁺ sinks, accumulating large amounts of Ca²⁺ within the vacuole as crystals. The pattern of addition of Ca²⁺ during crystal growth indicates a highly regulated process with bidirectional crystal growth. In very young idioblasts,⁴⁵Ca²⁺ is incorporated along the entire length of the needle-shaped raphide crystals, but as they mature incorporation only occurs at crystal tips in a bidirectional mode. At full maturity, the idioblast stops Ca²⁺ uptake, although the cells are still alive, demonstrating an ability to strictly regulate Ca transport processes at the plasma membrane. In situ hybridization for ribosomal RNA shows young idioblasts are extremely active cells, are more active than older idioblasts, and have higher general activity than surrounding mesophyll cells. Polarizing and scanning electron microscopy demonstrate that the crystal morphology changes as crystals develop and includes morphological polarity and an apparent nucleation point from which crystals grow bidirectionally. These results indicate a carefully regulated process of biomineralization in the vacuole. Finally, we show that the cytoskeleton is important in controlling the idioblast cell shape, but the regulation of crystal growth and morphology is under a different control mechanism.Abbreviation SEM scanning electron microscopy