A Light and Electron Microscopical Investigation of Loricate Choanoflagellates (Choanoflagellida, Acanthoecidae) from the Andaman Sea, SW Thailand and Denmark: Species of Cosmoeca gen. n.

The choanoflagellate genus Cosmoeca gen.n. is characterized by a very regular arrangement of rod-shaped costal strips, forming 9–12 longitudinal costae (each composed of 34 costal strips) and 2–3 transverse costae. Anteriorly the longitudinal costae attach the transverse costae at the joints between neighbouring transverse costal strips. Five species of Cosmoeca are described: norvegica sp.n. (type species; previously referred to as sp. "N"), C. ventricosa sp.n., (C. phuketensis sp.n., C. subulata sp.n. and C. ceratophora sp.n. Cosmoece ventricosa sp.n. is obviously part of from complex, the extent of which has not yet been fully explained. In this paper, three groups of specimens clearly related to C. ventricosa sp.n. are illustrated and briefly described ( C. ventricosa forms A. B, C). Form A appears to be identical to Pleurasiga orculaeformis Schiller, 1925, sensu Leadbeater.     

Costal Strip Accumulation and Lorica Assembly In the Marine Choanoflagellate Diplotheca Costata Valkanov

ABSTRACT The lorica of the tectiform choanoflagellate D. costata contains five categories of costal strips distinguishable from each other on the basis of morphology and patterning. Categories of strips include those forming the anterior transverse costa; the anterior, intermediate, and posterior costal strips, respectively, of the longitudinal costae and those constituting the posterior transverse costa. the distinctive morphology of each class of strips makes it possible to observe their location and orientation within the overall accumulation of strips at the top of the parent cell collar. In Diplotheca costata the orientation and positioning of the different categories of strips in an accumulation anticipates their orientation and imbrication in the mature lorica. Assembly of the lorica from an accumulation of strips involves lateral sliding of costal strips to constitute transverse costae and longitudinal sliding of strips to constitute longitudinal costae. the motive force for lorica assembly is provided by extension of the anterolateral tentacles.     

Choanoflagellate lorica construction and assembly: the nudiform condition. I. Savillea species

The lorica of Savillea spp. (Choanoflagellida) comprises a two layered arrangement of siliceous costae, the inner layer consists of helical costae and the outer layer longitudinal. In Savillea micropora, the helical costae, in a left-handed conformation, undergo 1.5 turns and extend from a short distance above the base of the lorica to the anterior opening. In S. parva the helical costae undergo two turns from base to anterior opening. Ratios of the numbers of helical to longitudinal costae vary from 1:1 in S. parva to 1:1-1:4 in S. micropora. Cell division in Savillea is of the nudiform type, whereby a cell divides to produce a 'naked' flagellated juvenile that swims away from the parent lorica, settles on to a surface and produces a complete set of costal strips. The first formed strips are those that will form the longitudinal costae, this is followed by the slightly thicker strips which will form the inner helical costae. Lorica assembly occurs as a single continuous process and is mediated by the forward movement of the collar tentacles and a rotational movement by the cell. The longitudinal and helical costae are thereby moved in this one combined movement to their respective positions. The longitudinal costae must rotate freely during assembly whilst the helical costae are held at their front end by the respective longitudinal costae and their rear end on the surface of the cell sheath. The concluding inference, based on lorica construction, that there must be a rotational as well as the observed forward movement during lorica assembly is of seminal importance to understanding the basic pattern of lorica construction and the mechanism of lorica assembly in all choanoflagellates.     

Ontogeny and evolution within the Myophorellidae (Bivalvia): Paedomorphic trends

The role of heterochronic phenomena in molluscan evolution is insufficiently understood but potentially significant. The aim of this paper is to explore some paedomorphic trends in the evolution of the Myophorellidae (Bivalvia: Trigoniida). Early ontogeny of general shell shape and ornamentation of one species of Steinmanella was analyzed and compared to data obtained for three species of Myophorella: two belonging to the subgenus M. (Promyophorella) (one from the Jurassic and one from the Cretaceous) and one belonging to the Jurassic M. (Myophorella). For general shell shape, a geometric morphometric analysis was performed on lateral views of the shells. Regarding ornamentation, flank costal disposition on the marginal carina, tubercle separation and relative development of the sub-commarginal subset of flank costae were quantified. A qualitative analysis was also performed. A two-trend shell shape development is considered as primitive. The first trend is marked by a relative reduction of the posterior margin together with a relative elongation of the shell. A tangential opisthogyrate growth component characterizes the second trend. There is a transitional stage where both trends interact. Early flank ornamentation is characterized by two or three sub-commarginal costae, continuous through the area, after which oblique costae with fine tubercles start to form. The subgenus M. (Myophorella) evolved by paedomorphic retention of juvenile shell shape and ornamentation, resulting in a large shell with coarse tubercles. Shell morphology in Steinmanella evolved by paedomorphic suppression of the primitive second trend in the development of the shell, resulting in an orthogyrate shell shape, and the retention of juvenile ornamentation (coarse tubercles, more sub-commarginal costae, juvenile rates of costal disposition). The paedomorphic (most likely by deceleration) retention of juvenile shell morphology within the Myophorellidae seems to have been recurrent within the group, resulting in many cases of convergence, and obscuring the phylogenetic relationships among its species.     

The costae presenting in high-temperature-induced <Emphasis Type="Italic">vestigial</Emphasis> wings of <Emphasis Type="Italic">Drosophila</Emphasis>: implications for anterior wing margin formation

It has long been noted that high temperature produces great variation in wing forms of the vestigial mutant of Drosophila. Most of the wings have defects in the wing blade and partially formed wing margin, which are the result of autonomous cell death in the presumptive wing blade or costal region of the wing disc. The vestigial gene (vg) and the interaction of Vg protein with other gene products are well understood. With this biochemical knowledge, reinvestigations of the high-temperature-induced vestigial wings and the elucidation of the molecular mechanism underlying the large-scale variation of the wing forms may provide insight into further understanding of development of the wing of Drosophila. As a first step of such explorations, I examined high-temperature-induced (29°C) vestigial wings. In the first part of this paper, I provide evidences to show that the proximal and distal costae in these wings exhibit regular and continuous variation, which suggests different developmental processes for the proximal and distal costal sections. Judging by the costae presenting in the anterior wing margin, I propose that the proximal and distal costal sections are independent growth units. The genes that regulate formation of the distal costal section also strongly affect proliferation of cells nearby; however, the same phenomenon has not been found in the proximal costal section. The distal costal section seems to be an extension of the radius vein. vestigial, one of the most intensely researched temperature-sensitive mutations, is a good candidate for the study of marginal vein formation. In the second part of the paper, I regroup the wing forms of these wings, chiefly by comparison of venation among these wings, and try to elucidate the variation of the wing forms according to the results of previous work and the conclusions reached in the first part of this paper, and provide clues for further researches.     

Costal strip production and lorica assembly in the large tectiform choanoflagellate Diaphanoeca grandis Ellis

Diaphanoeca grandis posseses a voluminous flask-shaped lorica comprising an outer layer of 12 longitudinal costae and an inner layer of four transverse costae. The cell is suspended just above the centre of the lorica chamber by tentacles that are attached to the anterior transverse ring. The component costal strips are superficially similar although four different strip categories can be distinguished on the basis of length and morphology. Costal strips are produced ‘upside-down’ within the parent cell and accumulated in a close-packed horizontal ring at the top of the inner surface of the collar. The order in which costal strips are produced is consistent, starting with those for the transverse rings, basal to anterior, and then the longitudinal costae, again with the posterior first and the anterior later. Cell division is of the classical tectiform variety with the juvenile cell being inverted and pushed backwards out of the parent lorica. Lorica assembly entails firstly the rotation of the anterior vertical strips so they become horizontal and then their movement backwards under the posterior layer of longitudinal strips. From this time onwards, lorica assembly proceeds in a standard manner with the lorica-assembling tentacles providing a forward and left-handed rotational movement.     

Apertural constrictions in some oncocerid cephalopods

Stridsberg, Sven 1981 12 15: Apertural constrictions in some oncocerid cephalopods. Lethaia , Vol. 14, pp. 269–276. Oslo. ISSN 0024–1164.
In some oncocerid cephalopods the shape of the aperture, siphuncle and the general outline of the shell have long served as generic characters. The aperture is mostly elaborated into a certain number of sinuses which take their final shape only in the adult. Therefore, knowledge of the relative age of the animal is required. The last chamber may serve as an indicator of age. A last chamber smaller than the second last indicates a mature specimen. This is because continued growth would have caused the death of the animal as the buoyancy turned negative. Moreover, it is of great importance to study the growth lines along the peristome to observe whether growth has ceased or not. Growth variations have been compared with growth stages. Furthermore, a constricted or contracted aperture can only be determined on specimens with the shell still preserved. Functional parallels are drawn between the Aprychopsis operculum and the restricted aperture. * Cephalopoda, Oncorerida. aperture, ontogeny, growth lines, functional morphologv , Aptychopsis. Silurian, Gotland .     

Acanthocorbis mongolica nov. spec.: description of the first freshwater loricate choanoflagellate (Acanthoecida) from a Mongolian lake

A new acanthoecid choanoflagellate species, Acanthocorbis mongolica sp. nov. was found in preserved phytoplankton samples from the freshwater lake Bayan Nuur (Uvs Nuur Basin, NW Mongolia) in concentrations of up to 1.8×10(5)cellsL(-1). It is the first well-documented species of the mainly marine order Acanthoecida to be found in a freshwater lake. The lorica structures were studied with scanning electron microscopy. Key morphological features of the vase-shaped lorica are spine bases that are composed of multiple (2-4) parallel costal strips, and the existence of two transverse costae. The ecological implications of this find are discussed.     

Stephanoeca arndti spec. nov. – First cultivation success including molecular and autecological data from a freshwater acanthoecid choanoflagellate from Samoa

Until recently acanthoecid choanoflagellates have been described only from marine and brackish waters. Here I describe a distinct, strictly freshwater acanthoecid species from Samoa based on its morphology, ecology and molecular biological data (partial Small Subunit rDNA). The lorica of the species is characterised by two extensions at the posterior chamber which are used for attachment to the substratum. The posterior chamber is constructed of irregularly arranged costae. The anterior chamber consists of four transverse costal rings and 14–18 longitudinal costae. Despite its sturdy appearance, the lorica was extremely sensitive to water turbulence and movements of the water. The species showed a salinity tolerance of 0.5 practical salinity units with reduced growth rates and a temperature tolerance range of 20–34 °C. According to the morphology, phylogenetic analysis, and autecology of the species it was classified as a member of the genus Stephanoeca.     

Kakoeca antarctica gen. et sp.n., a loricate choanoflagellate (Acanthoecidae, Choanoflagellida) from Antarctic sea ice with a unique protoplast suspensory membrane

A new genus and species of loricate choanoflagellate, Kakoeca aniarctica Buck & Marchant gen. et sp.n. grown in rough culture from an Antarctic sea ice innoculum is described. This organism has a distinctive lorica morphology consisting of more than 200 costal strips arranged in transverse and longitudinal costae that arc perpendicular to one another in the posterior portion of the lorica. The transverse costae show declination with respect to the lorica axis in the anterior part of the lorica. The cell is suspended in the lorica by a robust protoplast suspensory membrane. This membrane blocks water flow from the posterior of the lorica necessitating water entry through the side of the lorica, an area where the maximum sized apertures in the lorica are found. Terminology (lorica lining and protoplast suspensory) is suggested for the two types of lorica membranes which have been found associated with loricas.     

Loricate choanoflagellates (Acanthoecida) from warm water seas. VI. Pleurasiga Schiller and Parvicorbicula Deflandre

The loricate choanoflagellate genera Pleurasiga and Parvicorbicula are taxonomically ambiguous. Pleurasiga because of the uncertainty that relates to the true identity of the type species, and Parvicorbicula because too many newly described species over time have been dumped here in lack of better options. While all species currently allocated to the genus Pleurasiga (with the exception of the type species) are observed in our samples from the global warm water belt, the genus Parvicorbicula is represented by just a few and mostly infrequently recorded taxa. Two new species, viz. Pl. quadrangiella sp. nov. and Pl. minutissima sp. nov., are described here. While the former is closely related to Pl. echinocostata, the latter is reminiscent of Pl. minima. Core species of Pleurasiga and Parvicorbicula deviate from the vast majority of loricate choanoflagellates in having both the anterior and the mid-lorica transverse costae located exterior to the longitudinal costae. In Pl. quadrangiella there is no mid-lorica transverse costa but rather a small posterior transverse costa located inside the longitudinal costae. In Pl. minutissima the mid-lorica transverse costa has extensive costal strip overlaps which reveal patterns of costal strip junctions that deviate from the norm.     

贵州喀斯特高原金发藓原变种(Polytrichum commune Hedw.var.commune)蒴齿水湿运动研究

为探究线齿藓类植物在水湿运动中蒴齿结构的变化及对孢子散发的影响,选取贵州喀斯特高原金发藓原变种(Polytrichum commune Hedw.var.commune)为研究对象,通过观察湿度变化下蒴齿结构差异及孢子释放规律,拟揭示水湿运动对孢子释放的影响和功能。结果显示:①湿度增加引起蒴齿间距及盖膜面积的显著增大,并在干燥时恢复。其中齿间距从8.33μm显著增加到11.53μm,同时盖膜面积扩大20%。②在连续风吹试验中,水湿运动初期孢子释放量显著提高,随蒴齿结构的恢复呈下降趋势,并最终保持在极低的孢子释放数量。同时发现,湿度增加导致孢子释放中簇孢占比的提高,并随孢子释放量的减少呈上升趋势,并在蒴齿结构恢复时达到显著差异。③通过单独对干燥期、水湿运动初期及蒴齿结构恢复期进行风吹试验发现,水湿运动初期孢子释放量显著高于干燥期和蒴齿结构再恢复期。当蒴齿结构恢复时,由于簇孢占比的提高,孢子的释放数量仍能显著高于干燥期。本研究表明在水湿运动中金发藓原变种蒴齿结构发生改变,进而显著提高孢子的释放量,并在蒴齿结构恢复时仍能保持高于干燥时的孢子释放能力,这对该物种的传播及繁衍具有积极的意义。     

RETRODISPLACEMENT OF THE ORAL AND ANAL OPENINGS IN DENDRASTERID SAND DOLLARS

In regular echinoids, the mouth opening (or peristome) and the anal opening (or periproct) are located centrally. In irregular echinoids, the peristome tends to shift toward the anterior end of the test, whereas the periproct typically shifts toward the posterior end. This produces an anatomically polarized morphology, which is consistent with functional expectations. In the dendrasterid sand dollars, however, the peristome and periproct have been displaced in the “wrong” directions; the peristome has shifted posteriorly, whereas the periproct has shifted anteriorly. These movements, which run counter to functional expectations, may be termed “retrodisplacements.” This study presents a new model for the development of the oral surface in dendrasterids. The model assumes that the “Dendraster pattern” of development (which occurs in dendrasterids) was derived from the older “Echinarachnius pattern” (which occurs in other northern Pacific sand dollars). The Echinarachnius pattern includes two successive phases of asymmetric growth: the first phase favors anterior growth, whereas the second phase favors posterior growth. These two phases are normally balanced, and at maturity, the test appears to be symmetrical. But if the second phase of unequal growth were suppressed through a heterochronic change in development, the effects on test development would be profound. On the aboral surface, the predicted effects include posterior displacement of the apical system. On the oral surface, the predicted effects include retrodisplacement of the peristome and periproct, as well as conspicuous changes in ambulacral and interambulacral development. In fact, all of the predicted effects are characteristic features of dendrasterids. The model assumes that the oral and aboral surfaces could be simultaneously affected by the same developmental processes. This assumption is supported by empirical evidence: in dendrasterids, there is a strong correlation between the displacement of the apical system (on the aboral surface) and the displacement of the peristome (on the oral surface). The displacement of the apical system (known as “apical eccentricity”) is regarded as a valuable adaptation, because it facilitates suspension feeding. But if oral and aboral development are linked, then selective pressure for apical eccentricity would simultaneously produce new oral characters as well. Thus, the retrodisplacement of the peristome and periproct in dendrasterids may be related to developmental constraints. These unusual characters may have little or no functional significance.     

How does winter pruning affect peach tree–Myzus persicae interactions?

Winter tree pruning is a cultural practice known to modify vegetative growth, which is likely to affect the development of pests. However, it has been poorly addressed as a cultural control method for diminishing the population levels of the green peach aphid, Myzus persicae (Sulzer) (Homoptera: Aphididae), in peach [ Prunus persica (L.) Batsch (Rosaceae)] orchards. In this study, we conducted a 2-year, on-station experiment to evaluate how winter pruning affects peach– M. persicae interactions, by examining tree vegetative growth, aphid population dynamics, and crop yield and fruit quality. We collected data under an insect-proof shelter on adult peach trees submitted to various levels of pruning and artificially infested with aphids. Our results showed that pruning enhanced shoot growth due to the proportion of growing shoots, which increased exponentially (10–60%), whereas the growth rate of growing shoots was not affected. The degree of infestation of peach trees increased with increasing pruning intensity. This effect was mainly due to the increase of the proportion of growing shoots, on which aphids developed better than on rosettes. In turn, the higher the aphid infestation, the higher the aphid-induced shoot-tip damage, leaf curling, and leaf fall that disturbed the growth of growing shoots. However, aphids did not considerably reduce fruit quality at harvest. They did not affect fresh fruit weight, and the refractometric index (indicator of sugar content) was reduced by only 3–4%. The relevance of winter pruning as a cultural method for pest control in orchards conducted under integrated fruit production guidelines is discussed.     

Developmental studies on the loricate choanoflagellateStephanoeca diplocostata Ellis. V. The cytoskeleton and the effects of microtubule poisons

Summary InStephanoeca diplocostata microtubules are located in four positions namely: within the flagellar axoneme; just beneath the plasmalemma; associated with the silica deposition vesicles (SDVs) during early stages of costal strip deposition; and in the mitotic spindle. At the anterior end of the cell the 50–60 peripheral microtubules, which are organized more or less parallel to the long axis of the cell, converge around the base of the emergent flagellum. A short second flagellar base is positioned between the nucleus and the base of the emergent flagellum. Developing costal strips are located individually within SDVs in the peripheral cytoplasm. During the early stages of silica deposition each SDV is curved and subtended longitudinally on its concave side by two microtubules. When a costal strip has achieved sufficient rigidity to withstand bending the SDV-associated microtubules are depolymerized. Treatment of exponentially growing cells with sublethal concentrations of microtubule poisons, such as colchicine, podophyllotoxin, griseofulvin andVinca alkaloids depresses growth. Treatment with these drugs also affects the length and morphology of developing costal strips perhaps by interfering with the shaping and supporting functions of SDV-associated microtubules. Instead of being long and crescentic with a standard radius of curvature, costal strips of treated cells are usually short and misshapen, with irregular bends. After drug treatment, juveniles produced as a result of cell division do not develop flagella but can still assemble a lorica although it is usually misshapen. The role of microtubules and microfilaments in lorica production is discussed.     

论非洲叶肢介科的分类

叶肢介化石生长线下缘锯齿状构造曾作为非洲叶肢介科(Afrograptidae)分类的主要特征,通过扫描图像,从比较解剖学研究入手,揭示了现生与化石叶肢介壳瓣的锯齿构造是由于分布于生长线的一排刚毛,基部关节脱落而形成的;分析了生长线刚毛的形态是属于长针形的轴刚毛,主要司触角功能;在5科18属现生叶肢介中,至少3科7属32种具有生长线刚毛,22属化石叶肢介有锯齿构造;作者认为这一构造被视为非洲叶肢介科分类的主要依据是不合适的,壳瓣的放射褶或粗瘤构造在高级分类上更重要,进而对该科的含义进行了厘定;从壳瓣具有多条放射褶这一构造特征来看,它与小叶肢介超科(Estheriellioidea)的成员在发生关系上比较密切,小叶肢介超科可提升为亚目(Estheriellidea),包括小叶肢介超科和非洲叶肢介超科,是中生代初兴起的一个类群。在白垩纪中期消失。     

Loricate choanoflagellates (Acanthoecida) from warm water seas. II. Bicosta,Apheloecion, Campyloacantha,Crucispina, Calliacantha and Saroeca

The main outcome of this and subsequent papers is to provide a baseline survey of heterotrophic protist diversity from warm water marine ecosystems, exemplified by loricate choanoflagellates (Acanthoecida). Genera in focus here (i.e. Bicosta, Apheloecion, Campyloacantha, Crucispina, Calliacantha and Saroeca) possess anterior spines or projections and a posterior pedicel, and have 0, 1 or 2 transverse costae. Longitudinal costae are, with the exception of Campyloacantha, external to transverse costal elements across all genera examined here. We describe here Apheloecion eqpacia sp. nov. and Calliacantha magna sp. nov., both of which are so far distributionally confined to warm water habitats. A ‘form A’ of Bicosta minor is introduced to facilitate the distinction between B. minor sensu stricto and a presumed warm water adapted variant with a posterior lorica chamber twist of the longitudinal costae.     

Characterization of gp93, a Novel, Highly Heterogeneous Glycoprotein Present in Growth Cone Membranes

Abstract: gp93 was first described in growth cones from fetal rat brain as a 90–97-kDa glycoprotein family that binds wheat-germ agglutinin and consists of at least 12 different isoelectric variants (pl range ∼4.9–6.4). Of particular interest is that different sets of gp93 variants are expressed in growth cones isolated from different brain regions. The preparation of a polyclonal antibody to gp93 allowed further characterization of this glycoprotein. The carbohydrate groups of gp93 were partially characterized by digestion with different glycosidases. The results indicate that most or all oligosaccharide units are N-linked (asparagine-linked) and contain sialic acid. Two-dimensional polyacrylamide gel electrophoresis and western blot with anti-gp93 show that deglycosylated gp93 is an only slightly heterogeneous polypeptide of 66 kDa, indicating that gp93 heterogeneity is due, primarily or exclusively, to differential glycosylation. Analysis of the tissue distribution in fetal rat showed gp93 to be highly enriched in the brain. Immunoblots and immunostaining of cross sections of developing cerebellum revealed that gp93 is developmentally regulated in this tissue, associated primarily with growing parallel fibers and Purkinje dendrites. Immunostaining of neurons in culture shows significant amounts of gp93 in elongating neurites and growth cones. Our results indicate that gp93 is a developmentally regulated glycoprotein of the brain that is most prominent in growth cones and growing neurites and that appears to be glycosylated differentially by different neurons.     

Abnormal growth patterns in the sea urchin Tripneustes CF. Gratilla (L.) under pollution (Echinodermata,Echinoidea)

Two populations of deformed sea-urchins were found in the vicinity of a combined power and desalination plant in the Gulf of Eilat (Aqaba), Red Sea. This area is highly polluted by thermohaline and heavy metal ion effluents. More than 60% of the urchins showed irregular bulging of the aboral half of the test. The height (H) to diameter (D) ratio for the most affected population was 0.70 (±0.15) compared with 0.53 (±0.04) for a normal population, away from the powerplant. In extremely deformed individuals the H/D ratio reached 1.4. The deformed sea-urchins had a wider peristome aperture and larger Aristotle's lantern, and fewer interambulacral plates than a normal urchin of the same diameter.Growth rate of highly deformed urchins in aquaria, under non-polluted conditions, was very low. In 2 months their average diameter increased by only 0.2 mm, compared with 7–8 mm in normal or slightly deformed urchins, under the same conditions.Growth lines in deformed urchins's plates indicate excessive growth in the meridional direction which is normally much less. It is suggested that controlled growth was disrupted. Some possible controlling mechanisms are discussed.     

Evidence that size-selective mortality affects growth of Atlantic cod (Gadus morhua L.) in the southern Gulf of St Lawrence

The effects of size-selective fishing mortality on the growth of Atlantic cod ( Gadus morhuu L.) in the southern Gulf of St Lawrence were investigated and compared between: (1) a period when fishing mortality was relatively high, growth was relatively rapid, and abundance low (1967–1972 year classes): and (2) a period when fishing mortality was lower, growth was slow, and density high (1977–1982 year classes). Cod first entered the fishery at age 3 during both periods. The 1967–1972 year classes (fast growing) were fully recruited to the fishery by age 5 or 6 and the fishery removed over twice as many fish from the lower than upper quartiles of length-at-age distributions for cod 4 to 10 years old (disproportionately high exploitation of slow-growing fish). In contrast. the 1977–1982 year classes (slow growing) did not fully recruit to the fishery until age 9 or 10 and the fishery removed four times as many fish from the upper than lower quartiles of the length-at-age distributions for 4- to 10-year-old cod (disproportionately high exploitation of fast-growing fish). The reduced mean lengths-at-age of the 1977–1982 year classes compared with the 1967–I972 year-classes is consistent with the different patterns of exploitation of fast- and slow-growing fish for the two periods.