Developmental studies on the loricate choanoflagellateStephanoeca diplocostata ellis

Summary Cells ofStephanoeca diplocostata comprise a colourless, flagellated, protoplast lodged in a lorica made of siliceous costae. The single anterior flagellum creates a water current from which bacteria and other food particles are filtered by the collar and ingested by linguiform pseudopodia that arise from the protoplast at the base of the collar. A waist divides the lorica into two chambers, the anterior of which contains three transverse and 17–20 longitudinal costae whereas the posterior chamber comprises two systems of spirally deflected costae and on some cells a pedicel at the hind end. Between 150–185 costal strips of similar length form the lorica. A thin investment covers the inner surface of the posterior chamber and lower part of the anterior chamber and joins with the protoplast at the level of the waist. Costal strips are produced within membrane-bounded vesicles in the peripheral cytoplasm and, although the origin of these vesicles is unknown, there is usually a close association with the Golgi apparatus. Once complete, strips are apparently released sideways through the plasmalemma into the cavity of the posterior lorica chamber. Later, bundles of strips are transferred to the top of the inner surface of the collar where they collectively form a horizontal ring. When sufficient strips to form a lorica have been accumulated at the top of the collar, cell division proceeds.     

Choanoflagellates (Sarcomastigophora, Protozoa) from the Coastal Waters of Taiwan and Japan. I. Three New Species

Three new acanthoecidaean species collected from the coastal waters of Taiwan and Japan are described: Acanthocorbis camarensis n. sp. resembles Acanthocorbis unguiculata in lorica morphology, but differs in having regularly arranged longitudinal and transverse costae at the anterior lorica chamber, and in lacking a nail at the apical end of anterior spine; Diaphanoeca spiralifurca n. sp. is characterized by the spiral arrangement of the costal strips in the posterior half of the lorica chamber and is closely related to Diaphanoeca grandis; Stephanoeca supracostata n. sp. is closely related to Stephanoeca elegans, but differs in having an additional transverse costa at the anterior lorica chamber.     

Further observations on Calliacantha Leadbeater Choanoflagellata), with special reference to C. simplex sp. nov. from many parts of the world.

C. simplex is a new species with an unusually wide geographical range, occurring at sea temperatures as varied as 0 degrees C under ice at Pt Barrow or -1 degrees C in arctic Canada, to 22 degrees C on the equator at the Galapagos Islands. The morphology and range of variation are illustrated by means of light microscopy, transmission electron microscopy and scanning electron microscopy applied to dry whole mounts prepared in situ from freshly-gathered wild material. Among the diagnostic structural features, special interest attaches to the position of the anterior transverse costa which is located unusually far back in comparison with other members of the genus; it is also shown to be within and not outside the ring of four longitudinal costae building up the lorica chamber, although this feature can only be ascertained by scanning. The differences between this species and C. natans (type species of the genus) are shown to be greater and to involve more characters than could previously have been recognized, and some possible functional implications are discussed in a preliminary way.     

武汉东湖周丛原生动物六新种

本文报道武汉东湖周丛原生动物的6种纤毛虫新种:绿累枝虫Epistylis chlorelligerum sp. nov.、斗鞘居虫Vaginicola cupulata sp. nov.、弯鞘居虫Vaginicola curvata sp. nov.、褶鞘居虫Vaginicola plicata sp. nov.、大靴纤虫Cothurnia magna sp. nov.、多纹平鞘虫Platycola multistriata sp. nov.。       

THE NEAR-SPINELESS TRACHELOMONAS GRANDIS (EUGLENOPHYCEAE) SUPERFICIALLY APPEARS SPINY BY ATTRACTING BACTERIA TO ITS SURFACE1,2

Trachelomonas grandis Singh has a mucilaginous, highly porous mineralized lorica (envelope) generally without ornamentation except occasionally for a few short, tapered, anterior or posterior spines. However, as our first cultures of this species aged, rod-shaped structures appeared on the loricas. That these surface projections were bacteria was determined by scanning and transmission electron microscopy. The bacteria, 2-6 μm long with rounded apices, were oriented perpendicular to the exterior lorica surface and were attached on one end by apically produced tie-down fibers. The bacteria also secreted fibers over their entire surface, forming a network between them that collapsed during specimen preparation for scanning electron microscopy. The density of the surface bacteria increased with time until the lorica took on a “spiny” appearance superficially similar to lorica extensions of algal origin. In mature algal specimens, an estimated 1200-1800 bacteria per lorica occurred as a monolayer, the maximum number related to the surface area of the lorica available for bacterial colonization. The bacteria, always motionless while attached, showed putative evidence of budding. Fission formed short chains of up to three cells on the lorica. Our cultures maintained this association for 8 years (1972-1979). However, cultures ordered for further study in the past year have failed to develop loricas with more than just a few bacterial cells, and most have none.     

A taxonomic and ultrastructural study of Trachelomonas Ehr. (Euglenophyta) from subtropical Argentina

Fifty-four loricated euglenophyta taxa sampled in the province of Chaco, Argentina, belonging to the genus Trachelomonas Ehr., have been examined by means of scanning electron microscopy. On the basis of these observations three new varieties are proposed: T. oviformis van duplex, T. robusta var. sparsiornata and T. Sydneyensis var. acuminata. Several details of the lorica ultrastructure are illustrated.     

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.     

New Species of Lagenophrys (Ciliophora,Peritrichia) from New Zealand and Australia1

Lagenophrys novazealandae n. sp. occurs on the gills of Paranephrops zealandicus, a parastacid crayfish from New Zealand. The new species has the hemispheroidal lorica most common among members of its genus and is distinguished by its possession of large tubercles on the thickened edge of the anterior lip of the lorica aperture, a deep cleft in the left side of the lip's edge, and a ovoid to reniform macronucleus located in the right-hand part of the body. It is probable that an as yet unnamed species of Lagenophrys known to occur on another species of Paranephrops in New Zealand is distinct from L. novazealandae but phylogenetically related to it. Lagenophrys petila n. sp. occurs on setae of Parastacoides tasmanicus, a parastacid from Tasmania. The new species has an ovoid lorica tapering to a slender pseudostalk at the posterior end, a type of lorica possessed by only two other members of its genus that also attach to their host's setae. It is distinguished from the other ovoid species by the proportions of the lorica, the extreme shortness of the lips of the lorica aperture, and an ovoid macronucleus located in the right, anterior part of the body. Clefts in the lips of L. novazealandae and other members of Lagenophrys may function as points of flexure to allow the lips to bend in ways that accommodate interspecific differences in the size of the epistomial disk and its operation during suspension feeding.     

Role of the cytoskeleton in choanoflagellate lorica assembly

ABSTRACT. Cell division in Acanthoeca spectabilis produces a "naked" motile daughter cell (juvenile) that settles onto a surface and deposits siliceous costal strips that are stored extracellularly in bundles. When complete, the bundles of strips are assembled in a single continuous movement to form a basket-like lorica. Assembly can be divided into four overlapping stages. Stage 1 entails the left-handed rotation of strips at the anterior end while the posterior end remains stationary. Stage 2 includes the posterior protrusion of the cell to form a stalk. Stage 3 involves the anterior extension of the spines, and Stage 4 the dilation of the lorica chamber and deposition of the organic investment. Scanning electron microscopic images reveal a one-to-one association between the moving bundles of strips and the anterior ring of lorica-assembling tentacles. Treatment with microtubule inhibitors produces "dwarf" cells that lack stalks, have their spines extended, and possess collars but lack flagella. Treatment with microfilament (actin) inhibitors prevents extension of the anterior spines. These experiments demonstrate that posterior cell extension is primarily mediated by microtubules whereas extension of the spines is controlled by the actin cytoskeleton. The processes of cytoskeletal rotation and extracellular costal strip movement are compared, respectively, with rotation of nuclei in animal embryos and movement of mammalian cells over surfaces.     

13 Viral control of phytoplankton

Since the separation of the Trachelomonas subgroup "Saccatae" into a new genus, Strombomonas Deflandre (1930), there has been some question as to its validity. Deflandre's separation was based on morphological characteristics such as the shape of the lorica, lack of a distinctive collar, possession of a tailpiece, lack of ornamentation, and ability to aggregate particles on the lorica. Recent molecular analyses indicated that the loricate taxa were monophyletic, but few species have been sampled. The LSU rDNA from eleven Strombomonas and thirty-eight Trachelomonas species was sequenced to evaluate the monophyly of the two genera. Bayesian and maximum-likelihood analyses found one monophyletic clade for each genus. The Trachelomonas clade was weakly supported, but had five strongly supported subclades. Morphological characters, such as lorica development and pellicle strip reduction, also supported separation of the genera. Lorica development in Strombomonas occurred from the anterior of the cell to the posterior, forming a shroud over the protoplast whereas in Trachelomonas , a layer of mucilage was excreted over the entire protoplast, followed by creation of the collar at the anterior end. Taxa from both genera underwent exponential strip reduction at the anterior and posterior poles. In Strombomonas , only one reduction was visible in the anterior pole, while in most Trachelomonas species, two reductions were visible. Likewise, Strombomonas species possessed two whorls of strip reduction in their posterior end compared to a single whorl of strip reduction in Trachelomonas species. The combined morphological and molecular data support the retention of Trachelomonas and Strombomonas as separate genera.     

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.     

12 Phylogeny of the euglenoid loricate genera trachelomonas and strombomonas based on morphological and molecular data

Since the separation of the Trachelomonas subgroup “Saccatae” into a new genus, Strombomonas Deflandre (1930), there has been some question as to its validity. Deflandre's separation was based on morphological characteristics such as the shape of the lorica, lack of a distinctive collar, possession of a tailpiece, lack of ornamentation, and ability to aggregate particles on the lorica. Recent molecular analyses indicated that the loricate taxa were monophyletic, but few species have been sampled. The LSU rDNA from eleven Strombomonas and thirty‐eight Trachelomonas species was sequenced to evaluate the monophyly of the two genera. Bayesian and maximum‐likelihood analyses found one monophyletic clade for each genus. The Trachelomonas clade was weakly supported, but had five strongly supported subclades. Morphological characters, such as lorica development and pellicle strip reduction, also supported separation of the genera. Lorica development in Strombomonas occurred from the anterior of the cell to the posterior, forming a shroud over the protoplast whereas in Trachelomonas, a layer of mucilage was excreted over the entire protoplast, followed by creation of the collar at the anterior end. Taxa from both genera underwent exponential strip reduction at the anterior and posterior poles. In Strombomonas, only one reduction was visible in the anterior pole, while in most Trachelomonas species, two reductions were visible. Likewise, Strombomonas species possessed two whorls of strip reduction in their posterior end compared to a single whorl of strip reduction in Trachelomonas species. The combined morphological and molecular data support the retention of Trachelomonas and Strombomonas as separate genera.     

Lorica Construction in Eufolliculina sp. (Ciliophora,Heterotrichida)1

ABSTRACT. The structure and ultrastructure of the chitinous lorica of Eufolliculina sp. are described. The lorica is produced from precursor material secreted by the motile swarmer immediately after settling. This material is located in numerous vesicles found in the cortical region of the cells and is secreted by exocytosis. Initially, material is secreted from the ventral part of the cell to produce the attachment plate of the lorica. After this, exocytosis occurs over most of the body surface as the ampulla part of the lorica is constructed. During the later stages of lorica formation, secretion is mainly limited to the anterior of the cell as the neck is formed. The lorica is shaped mainly by the action of the cilia and by the behavior of the cell. While the neck is being formed, the anterior part of the cell is deformed by a local accumulation of cytoplasmic vacuoles. This deformation is employed in shaping the neck. No changes were detected in the organization of the cortical infraciliature during the first stages of lorica formation, but they do occur after the neck has been produced and as the swarmer develops into the sessile form.     

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.     

MORPHOLOGICAL SEPARATION OF THE EUGLENOID GENERA TRACHELOMONAS AND STROMBOMONAS (EUGLENOPHYTA) BASED ON LORICA DEVELOPMENT AND POSTERIOR STRIP REDUCTION1

Since the separation of the Trachelomonas Ehrenberg subgroup “Saccatae” into a new genus, Strombomonas Deflandre (1930) , there has been some question as to its validity. Deflandre's separation was based entirely on characteristics of the lorica, including the shape of the lorica, the lack of a distinctive collar, possession of a tailpiece, lack of ornamentation, and the ability of Strombomonas species to aggregate particles on the surface of the lorica. Recent molecular analyses indicated that the loricate taxa (Trachelomonas and Strombomonas) formed a single monophyletic clade; however, the phylogenetic relationship of Strombomonas to Trachelomonas remains unclear because only two Strombomonas taxa have been sequenced to date. In this study, we evaluated the monophyly of the loricate genera using two sets of morphological characters, lorica development and pellicle strip reduction. Lorica development in Strombomonas occurred from the anterior of the cell to the posterior, forming a shroud over the protoplast. In Trachelomonas, a layer of mucilage was excreted over the entire protoplast, followed by creation of the collar at the anterior end. Taxa from both genera underwent exponential strip reduction at the anterior and posterior poles. In Strombomonas only one reduction was visible in the anterior pole, whereas in most Trachelomonas species two reductions were visible. Likewise, Strombomonas species possessed two whorls of strip reduction in the posterior end compared with a single whorl of strip reduction in Trachelomonas species. These morphological characters support the separation of Trachelomonas and Strombomonas as distinct genera.     

Tropical niche conservatism and the species richness gradient of North American butterflies

Aim We explore the potential role of the ‘tropical conservatism hypothesis’ in explaining the butterfly species richness gradient in North America. Its applicability can be derived from the tropical origin of butterflies and the presumed difficulties in evolving the cold tolerance required to permit the colonization and permanent occupation of the temperate zone. Location North America. Methods Digitized range maps for butterfly species north of Mexico were used to map richness for all species, species with distributions north of the Tropic of Capricorn (Extratropicals), and species that also occupy the tropics (Tropicals). A phylogeny resolved to subfamily was used to map the geographical pattern of mean root distance, a metric of the evolutionary development of assemblages. Regression models and general linear models examined environmental correlates of overall richness and for Extratropicals vs. Tropicals, patterns in summer vs. winter, and patterns in northern vs. southern North America. Results Species in more basal subfamilies dominate the south, whereas more derived clades occupy the north. There is also a ‘latitudinal’ richness gradient in Canada/Alaska, whereas in the conterminous USA richness primarily varies longitudinally. Overall richness is associated with broad‐ and mesoscale temperature gradients. The richness of Tropicals is strongly associated with temperature and distance from winter population sources. The richness of Extratropicals in the north is most strongly correlated with the pattern of glacial retreat since the more recent Ice Age, whereas in the south, richness is positively associated with the range of temperatures in mountains and the presence of forests but is negatively correlated with the broad‐scale temperature gradient. Main conclusions The tropical conservatism hypothesis provides a possible explanation for the complex structure of the species richness gradient. The Canada/Alaska fauna comprises temperate, boreal and tundra species that are nevertheless constrained by cold climates and limited vegetation, coupled with possible post‐Pleistocene recolonization lags. In the USA tropical species are constrained by temperature in winter as well as recolonization distances in summer, whereas temperate‐zone groups are richer in cooler climates in mountains and forests, where winter conditions are more suitable for diapause. The evolution of cold tolerance is key to both the evolutionary and ecological patterns.     

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.     

Growth, development, and nutritional physiology of grasshoppers from subarctic and temperate regions

Despite the importance of developmental rate, growth rate, and size at maturity in the life history of poikliotherms, the trade-offs among these traits and selection pressures involved in the evolution of these traits are not well understood. This study compared these traits in a grasshopper, Melanoplus sanguinipes F. (Orthoptera: Acrididae), from two contrasting geographical regions, subarctic Alaska and temperate Idaho. The growing season in the interior of Alaska is about 80 d shorter than at low-elevation sites in Idaho. We hypothesized that the Alaskan grasshoppers would show more rapid growth and development than grasshoppers from Idaho, at the cost of greater sensitivity to food quality. On a diet of lettuce and wheat bran, grasshoppers from Alaska developed from egg hatch to adult more rapidly than those from Idaho at each of three different temperature regimes. Averaged over all temperature treatments, the weight of the Alaskan grasshoppers was about 5% less than that of the Idaho grasshoppers at the adult molt. Feeding and digestive efficiencies were determined for the final two instars using two meridic diets: one with a high concentration of nutrients and the other with the same formulation but diluted with cellulose. Alaskan grasshoppers again developed more rapidly, weighed less, and had faster growth rates than those from Idaho. Alaskan grasshoppers supported their more rapid growth by increasing postingestive efficiencies; that is, they had higher conversion rates of digested matter to biomass on the high-quality diet, greater assimilation of food on the low-quality diet, and greater efficiency of nitrogen assimilation or retention on both diets. There was no evidence that performance of Alaskan grasshoppers suffered any more than that of the Idaho grasshoppers on the low-quality diet.     

Morphological Variation of <Emphasis Type="Italic">Keratella cochlearis</Emphasis> (Gosse) in a Backwater of the River Thames

The morphological variation of Keratella cochlearis in a Thames backwater has been studied over 4 years. There was a general inverse relationship between lorica length and temperature, but the annual cycle of change depended upon the rate of change of the temperature, and there was considerable variation between years. There was a similar inverse relationship between posterior spine length and temperature, and a shift in both relationships depending on whether the temperature was increasing or decreasing. As the water temperature increased from winter to summer the lorica and posterior spine were longer than at the same temperature as the water cooled from summer to winter. This shift can be modified by anomalous temperatures, such as a late spring or a cool summer.The form lacking a posterior spine usually, but not consistently, had a longer lorica than the typical spined forms. It usually disappeared from the samples at the end of November and did not reappear until March, although with a mild autumn and winter it persisted until January before disappearing. Forms without posterior spines did not all have the same origins.     

Changes in forest productivity across Alaska consistent with biome shift

Global vegetation models predict that boreal forests are particularly sensitive to a biome shift during the 21st century. This shift would manifest itself first at the biome's margins, with evergreen forest expanding into current tundra while being replaced by grasslands or temperate forest at the biome's southern edge. We evaluated changes in forest productivity since 1982 across boreal Alaska by linking satellite estimates of primary productivity and a large tree-ring data set. Trends in both records show consistent growth increases at the boreal-tundra ecotones that contrast with drought-induced productivity declines throughout interior Alaska. These patterns support the hypothesized effects of an initiating biome shift. Ultimately, tree dispersal rates, habitat availability and the rate of future climate change, and how it changes disturbance regimes, are expected to determine where the boreal biome will undergo a gradual geographic range shift, and where a more rapid decline.