Toward a Phylogenetic Classification of Primates Based on DNA Evidence Complemented by Fossil Evidence

A highly resolved primate cladogram based on DNA evidence is congruent with extant and fossil osteological evidence. A provisional primate classification based on this cladogram and the time scale provided by fossils and the model of local molecular clocks has all named taxa represent clades and assigns the same taxonomic rank to those clades of roughly equivalent age. Order Primates divides into Strepsirhini and Haplorhini. Strepsirhines divide into Lemuriformes and Loriformes, whereas haplorhines divide into Tarsiiformes and Anthropoidea. Within Anthropoidea when equivalent ranks are used for divisions within Platyrrhini and Catarrhini, Homininae divides into Hylobatini (common and siamang gibbon) and Hominini, and the latter divides into Pongina forPongo(orangutans) and Hominina forGorillaandHomo. Homoitself divides into the subgeneraH.(Homo) for humans andH.(Pan) for chimpanzees and bonobos. The differences between this provisional age related phylogenetic classification and current primate taxonomies are discussed.     

A NEW TAXODIACEOUS SEED CONE FROM THE OLIGOCENE OF WASHINGTON

Cunninghamiostrobus goedertii is described as a new species based on permineralized seed cones from the Early Oligocene of Washington. The fossils come from the Makah Formation and were found on the northern shore of the Olympic Peninsula. The cone consists of numerous bract-scale complexes arranged helically around a central axis. Each bract-scale complex has a large bract bearing a small flap of tissue adaxially that represents the ovuliferous scale. Up to three seeds were produced on each complex. The vascular trace to the bract-scale complex diverges from the vascular cylinder of the cone axis as a concentric strand. This divides in the outer cortex of the axis to form a large collateral bract tract abaxially and a minute scale trace adaxially. The latter continues outward to supply the ovuliferous scale. The bract trace divides, forming many strands outward which occur in a row with transfusion tissue between them. Many resin canals also occur in the bract. The new cone combines features found in modern cones of Athrolaxis, Cunninghamia, and Taiwania but is most similar to Cunninghamiostrobus yubariensis from the Late Cretaceous of Japan.     

Migratory divides coincide with reproductive barriers across replicated avian hybrid zones above the Tibetan Plateau

Migratory divides are proposed to be catalysts for speciation across a diversity of taxa. However, it is difficult to test the relative contributions of migratory behaviour vs. other divergent traits to reproductive isolation. Comparing hybrid zones with and without migratory divides offers a rare opportunity to directly examine the contribution of divergent migratory behaviour to reproductive barriers. We show that across replicate sampling transects of two pairs of barn swallow (Hirundo rustica) subspecies, strong reproductive isolation coincided with a migratory divide spanning 20 degrees of latitude. A third subspecies pair exhibited no evidence for a migratory divide and hybridised extensively. Within migratory divides, overwintering habitats were associated with assortative mating, implicating a central contribution of divergent migratory behaviour to reproductive barriers. The remarkable geographic coincidence between migratory divides and genetic breaks supports a long‐standing hypothesis that the Tibetan Plateau is a substantial barrier contributing to the diversity of Siberian avifauna.     

Bet hedging in the underworld

Under starvation conditions, the soil bacterium Sinorhizobium meliloti divides into two types of daughter cell: one suited to short-term and the other to long-term starvation.     

Why Nonlinear Biomedical Physics?

The two goals of Nonlinear Biomedical Physics are: firstly to show how nonlinear methods can shed new light on biological phenomena and medical applications and secondly to bridge the technical, mathematical, and cultural divides between the physical disciplines where these methods are being developed and the audience for their use in the biological and medical sciences.     

Transformation of the Plasmodium cynomolgi Oocyst1

SYNOPSIS. The transformation of the P. cynomolgi oocyst into definitive sporozoite forms occurs 8–10 days after an infective blood meal by Anopheles, stephensi mosquitoes. Vacuolization divides the oocyst cytoplasm into sporoblast sub-units from which sporozoites bud. The role of sporoblast nuclear and cytoplasmic components in the complex differentiative process is discussed.     

GROWTH OF TWO FACULTATIVELY HETEROTROPHIC MARINE CENTRIC DIATOMS1,2

The facultative, heterotrophs Cyclotella cryptica (sclone WT-1-8) and Coscinodiscus sp. were selectively isolated from coastal waters by dark incubation of organically enriched solid medium. C. cryptica grows in the dark with glucose and galactose, and Coscinodiscus sp. with glucose. Clone WT-1-8 of C. cryptica grows about twice as fast with glucose as a previously studied clone (0-3A). In the dark with, 5 × 10^?6 M glucose C. cryptica divides every 3 days, while with 5 × 10^?5 M glucose Coscinodiscus sp. divides every 10 days. Heterotrophic growth of either diatom for 1 year does not cause a major reduction in carbon, nitrogen, chlorophyll a, and chlorophyll c contents, or in photosynthetic ability, compared to light-grown cells. It is possible that facultative heterotrophy is of ecological benefit to these diatoms, probably for slow growth and survival during extended periods of dim light or darkness.     

Evolution,pollination, and systematics of the tribeNeottieae (Orchidaceae)

The various classifications of the orchid tribeNeottieae are reviewed and a new classification is proposed that divides the tribe into three subtribes,Neottiinae, Limodorinae, andCephalantherinae, based primarily on characters of the column (gynostemium). A cladistic analysis illustrates that these three subtribes are more closely related to one another than either is to any other group in subfam.Neottioideae, although there are very few apomorphic characters for the tribe. Pollination biology is also discussed showing links between breeding systems and distribution. There is also a possible role between column and labellum morphology and the emergence of a deceptive pollination syndrome from one of reward.     

疣壶藓尖叶变种的芽胞形成及其生态意义

该研究以疣壶藓尖叶变种(Gymnostomiella vernicosa var.acuminata)为实验材料,在人工培养条件下观察并记录其芽胞产生及脱落过程,以揭示该分类群及相关类群的芽胞形成过程和机制,为疣壶藓尖叶变种的分类提供参考性特征指标,明确苔藓植物芽胞的进化和生态学意义。结果显示,疣壶藓尖叶变种的芽胞形成过程划分为3个阶段:(1)茎表皮细胞的外切向壁局部向外隆起,外突的疣壶藓尖叶变种表皮细胞富含叶绿体,可进行光合作用。(2)芽胞起始细胞横向分裂,形成一个基细胞和一个顶细胞;基细胞经数次横向分裂,下部形成柄状结构,上部的细胞常呈喇叭形的“柄托”;顶细胞经多方向细胞分裂,形成椭球状至圆球状芽胞体,形成初期为富含叶绿体的厚壁细胞,成熟后叶绿体数目逐渐减少,最终变成深棕色至红棕色。(3)由薄壁的柄细胞随机破损使芽胞从母株上脱落。研究表明,在无法预测的多变栖息环境中,相对于有较高的能量、遗传和生态消耗的有性生殖,疣壶藓尖叶变种产生芽胞是一种风险分担策略,可以提高生存几率和有效利用资源,可视为一种扩大和维持种群的有效途径。     

The spermatogenous body cell of the coniferPicea abies (Norway spruce) contains actin microfilaments

Summary In conifer pollen, the generative cell divides into a sterile stalk cell and a body cell, which subsequently divides to produce two sperm. InPicea abies (Norway spruce, Pinaceae) this spermatogenous body cell contains actin microfilaments. Microfilament bundles follow the spherical contour of the body cell within the cell cortex, and also traverse the cytoplasm and enmesh amyloplasts and other organelles. In addition, microfilaments are associated with the surface of the body cell nucleus. The sterile stalk cell also contains microfilament bundles in the cytoplasm, around organelles, and along the nuclear surface. Within the pollen grain, microfilament bundles traverse the vegetative-cell cytoplasm and are enriched in a webbed cage which surrounds the body cell. Microfilaments were identified with rhodamine-phalloidin and with indirect immunofluo-rescence using a monoclonal antibody to actin. The majority of evidence in literature suggests that the spermatogenous generative cell in angiosperms does not contain actin microfilaments, so the presence of microfilaments within the spermatogenous body cell inP. abies appears to be a fundamental difference in sexual reproduction between conifers and angiosperms.     

A note on Wallemia sebi

A review of the available information on the monotypic genus Wallemia supports the interpretation that W. sebi is probably a basidiomycete and may be a teleomorph. It has dolipore/parenthesome septa similar to those found in the suborder Tremellineae, except that the associated parenthesome vesicles are very small and composed of a single membrane. A conjectural interpretation is made that the spore chains, which are composed of repeating sets of four, are meiospores generated from a permanently diploid mother cell that divides repeatedly to generate meiocyte daughter cells.     

“Constructing” the Cell Cycle in 3D

The cycle of duplication and division, known as the cell cycle, is the essential mechanism by which all living organisms reproduce. This activity allows students to develop an understanding of the main events that occur during the typical eukaryotic cell cycle mostly in the process of mitotic phase that divides the duplicated genetic material creating two genetically identical daughter cells.     

DIVISION APPARATUS OF THE CHLOROPLAST IN NANNOCHLORIS BACILLARIS (CHLOROPHYTA)1

Chloroplast division in Nannochloris bacillaris Naumann (Chlorophyta) was examined by electron microscopy after preparation of samples by freeze-substitution. A pair of belts appeared on the surface of the outer and inner envelope membranes at the middle of the chloroplast. These belts seemed to be constructed of thin fibrils that run parallel to the longitudinal direction of the belts. The outer fibrillar belt increased in width as the constriction of the chloroplast advanced. It appears that the fibrillar belt is the division apparatus of the chloroplast. It encircles the chloroplast and finally divides the chloroplast in two as the diameter of the belt decreases.     

The maturation divisions of the parthenogenetic stick insect Carausius morosus Br. (Orthoptera,Phasmidae)

The meiotic stages in the maturation of the egg of the parthenogenetic stick insect Carausius morosus Br. is described. The meiosis consists of two equational divisions and parthenogenesis is thus apomictic. The first prometaphase is formed between 5.8–5.5 days before oviposition; the first metaphase lasts until oviposition; the meiosis ends between 14 and 24 hours after oviposition. An extra chromosome doubling occurs before first anaphase, causing the first metaphase chromosomes to resemble bivalents and requiring that meiosis consists of two divisions instead of one. A terminal affinity between the daughter chromosomes influences chromosome movement during first and second metaphase and anaphase. The first and second polar bodies degenerate. The first polar body divides amitotically during pycnosis. Meiosis takes place ventrally in the egg, the germ anlage development dorsally. The pronucleus divides mitotically in the ventral part of the egg during its migration from ventral to dorsal, enabling blastoderm development to take place both ventrally and dorsally.     

Ratatouille: An Animated Account of Cooking,Taste, and Human Evolution

This paper analyzes the immensely popular animated film Ratatouille as a social and cultural document. It begins with a recapitulation of the movie's story line – a saga of an astute, ambitious and talented rat, who becomes transformed into an accomplished haute cuisine chef. The film illustrates recent anthropological writings on the central role of cooking in human evolution. It also shows how varieties of cooking and table manners provide key indications of the civilizing process. Ultimately, Ratatouille explores distinctions and similarities between “man and beast”. It communicates the idea that all living creatures share more in terms of aptitude and feeling than divides them.     

The nature and behaviour of supernumerary chromosomes in the rhizirideum group of the genus Allium

Individuals at various levels of ploidy in three species of Allium (angulosum, nutans and senescens) contain a morphologically uniform B-chromosome. This supernumerary is different in character from other B-types recorded for the genus. In diploids the B divides at second anaphase so that 50% of the pollen grains transmit it. The level of transmission is lower in the pollen of polyploids and still lower on the female side where pre-meiotic elimination occurs in both diploids and polyploids. Despite this, and although no effect of the B could be discerned on germination, all plants examined possessed the B-chromosome.This paper was prepared in the Department of Genetics, University of Birmingham while the author was a recipient of a British Council Scholarship.     

Segmentation (and eve) in very odd insect embryos

The formation of segments in the Drosophila early embryo is understood in greater detail than any other complex developmental process. Now, by studying other types of insect embryo, we can hope to deduce something of the ancestral mechanism of segmentation and the ways in which it has been modified in evolution. The parasitic wasp, Copidosoma floridanum, is spectacularly atypical of insects in that the small egg cell divides extensively, with no initial syncytial phase, and forms eventually some 2000 embryos⁽¹⁾. This process raises intriguing questions about the control of embryonic polarity and segmentation.     

The tapetum inSchizaea pectinata (Schizaeaceae) and a comparison with the tapetum inPsilotum nudum (Psilotaceae)

A combination tapetum consisting of a cellular, parietal component and a plasmodial component occurs inSchizaea pectinata. A single, tapetal initial layer divides to form an outer parietal layer which maintains its cellular integrity until late in spore wall development. The inner tapetal layer differentiates into a plasmodium which disappears after the outer exospore has developed. In the final stages of spore wall development, granular material occurs in large masses and is dispersed as small granules throughout the sporangial loculus. No tapetal membrane develops. Comparisons are drawn with the combination tapetum found inPsilotum nudum.     

GROWTH AND DIFFERENTIATION OF AXIAL AND LATERAL FILAMENTS IN BATRACHOSPERMUM SIRODOTII (RHODOPHYTA)1

Development of the vegetative gametophyte of Batrachospermum sirodotii Skuja was examined with light and both transmission and scanning electron microscopy. Patterns of wall growth were followed using the Calcofluor White ST pulse-chase method. Thallus structure was analysed in terms of the pattern of development of the apical, periaxial and pleuridial initials that generate the axial and whorled lateral filaments characteristic of Batrachospermum. Apical cells of axial filaments elongate initially by tip growth with the nucleus maintaining a distal position. Nuclear division is horizontal. One daughter nucleus migrates basipetally and a thin, convoluted annular septum and perforate-occluded pit connection are then formed. Elongating axial cells subsequently extend by wall deposition at the base of the cell. Periaxial cells are initiated laterally and elongate primarily by tip growth while the nucleus remains within the axial cell. The nucleus then migrates to the boundary between the initial and the axial cell, divides, and one daughter nucleus moves into the initial and the other back into the axial cell. A slightly irregular annular septum and simple-occluded pit connection are then formed. Pleuridial cell initials begin as terminal to subterminal protuberances on periaxial or pleuridial cells. They first extend by tip growth and later by bipolar band growth. The nucleus remains within the parent cell as the pleuridial initial expands and a narrow septal ring is formed between the two cells. It then migrates through the septal ring into the initial and divides transversely. One nucleus passes back into the parent cell and a thick, flat septum and perforate-occluded pit connection are formed. It is concluded that the potentially indeterminate axial filaments and the determinate lateral pleuridia represent distinct developmental types in Batrachospermum.