Equatorial Ridge Research Articles

Biogeography and evolution of hydrothermal-vent fauna in the eastern Pacific Ocean

The biogeography and evolutionary history of animals that live at hydrothermal vents are connected intimately to the spreading history of mid-ocean ridges. Extensive collections from two active ridge systems in the eastern Pacific Ocean provide an opportunity to examine the regional dispersion of vent-limited organisms. The degrees to which these habitat-limited species from disjunct areas are related gives preliminary information about exchange routes, dispersability, and rates of taxonomic change. Differences between vent faunae from the northern Juan de Fuca and southern East Pacific Rise systems indicate that geographical differentiation has occurred. Geophysical evidence shows that North America interposed as a barrier between the northeast and equatorial Pacific spreading ridges about 35 Ma BP. The vicariating vent fauna of the Juan de Fuca Ridge has since formed an endemic assemblage of generally lower diversity than that found at East Pacific Rise vents. Taxonomic comparisons suggest that rates of speciation have been low. Examination of spreading histories elsewhere should provide predictions of evolutionary patterns in the hydrothermal-vent faunae.

Stenoductus ktenostrepti n. sp. (Apicomplexa : Cephalina) from the Millipede, Ktenostreptus calcaratusDemange

Summary The morphology and life-history of a new cephaline gregarine Stenoductus ktenostrepti n. sp. (Apicomplexa: Cephalina) infecting the millipede, Ktenostreptus culcurutus Demange are described and its systematic position discussed. The sporonts reach 2361 by 432 μm. Gametocysts spherical or ovoid. Spores ovoid, 5.6 by 2.8 or 5.4 by 2.6 μm, with hyaline epispore having round polar projections and an equatorial ridge. Extrusion of spores in a naked cord-like sporodtict. The species has the following ratios: PL: TL = 1 : 21.3; PW : DW = 1 : 2.2.

Oscillations of Dynamic Topography in the Eastern Equatorial Pacific

For 14 months in 1980–81, surface dynamic height was monitored with inverted echo sounders at five sites from 0 to 9°N along 110°W. These records show that the SEC/NECC equatorial current system was well-developed during the boreal summer and fall, but weak and irregular during winter and spring when westward flow associated with the NEC extended as far south as 6°N. Superimposed on the mean dynamic topography of this region are energetic 20-to-80-day oscillations, longer periods being associated with higher latitudes. Near the equatorial ridge (∼5°N), these oscillations have predominantly monthly periods, and amplitude of ∼10 dyn cm comparable to the mean dynamic-height difference across the NECC. The broad in-phase meridional extent of these monthly oscillations implies that the principal mode of ridge variation is vertical undulation rather than meridional meandering, producing large in-phase monthly modulations in transport of the SEC and NECC. Oscillations or the equatorial ridge are correlated with propagating ∼1000-km wavelength sea surface temperature (SST) wave patterns observed in satellite infrared imagery. Passage of a northerly SST crest on the equatorial front at 110°W corresponds to a dynamic height minimum on the equatorial ridge. The relative phase and trochoidal shape of these crests is explained kinematically by superposition of the observed mean and oscillatory dynamic-height fields.

Processes of Short-Term Climatic Variability in the Baroclinic Structure of the Interior Western Tropical North Pacific

Abstract A realistic simulation of short-term climatic variability in the relative dynamic height of the interior western tropical North Pacific (4°–22°N, 127°E–180°) for 9 years (1966–74) was conducted using a two-layer, wind-driven, baroclinic long-wave model. Results of this model were compared with bimonthly maps of observed dynamic height (0/400 db) for the region, constructed by White and Hasunuma from all available temperature/depth observations for the same period. The interannual rms differences about the mean annual cycle of the model dynamic height had a spatial pattern over the region of interest that was nearly identical to that observed, with maximum values (i.e., 3.5 and 4.5 dyn cm, respectively) in the vicinity of the North Equatorial Ridge at 15°N and minimum values (i.e., 2.0 and 3.5 dyn cm, respectively) in the vicinity of the North Equatorial Ridge at 15°N and minimum values (i.e., 2.0 and 3.5 dyn cm, respectively) in the Countercurrent Trough at 7°N. Model frequency spectra were ident...

Spore morphology in the Dicksoniaceae. II. The genus Cibotium

Species of the dicksonioid genus Cibotium occur in the Hawaiian Islands, Central America – Mexico, and Southeast Asia – Western Malaysia. All investigated specimens produce 64-spored sporangia and the sodium hydroxide assay demonstrates a more or less granular perine deposition over the exine in mature or slightly immature spores. This perine form is shared with the other dicksonioid genera Thyrsopteris and Cystodium and with Metaxya and Lophosoria, two genera of problematical affinity which are palynologically more dicksonioid than cyatheoid. The spores of all Cibotium species show some degree of distal ridge development. The least pronounced ridges occur in Central American – Mexican specimens, but most spores from that region have conspicuous distal ridges whose degree of development intergrades with that of Hawaiian material, whereas the greatest degree of distal as well as equatorial ridge development occurs in the species of Southeast Asia – Western Malaysia. Margo development is variable but is also most pronounced in the species in Southeast Asia – Western Malaysia where it is comparable to that of Lophosoria. All investigated specimens show some degree of pitting of the margo, particularly near and parallel to the laesurae. The number of recognized Cibotium species varies considerably with author and the genus as a whole is in need of modern revisionary work.

Studies on a New Cephaline Gregarine, Stenoductus trigoniuli n. sp. With a Note on its Cytopathology

Summary A cephaline gregarine from the Indian millipedes, Trigoniulus goesi ( Porath ) and Xenobolus acuticonus Attems is described and reported here as Stenoductus trigoniuli n. sp. (Cephalina: Monoductidae). The gregarine forms a naked, cord-like sporoduct; its spores are ovoid, with hyaline epispore, having short, round polar thickenings and an equatorial ridge. Fat globules have been cytochemically demonstrated in its intracellular trophozoites in midgut epithelial cells of the millipedes. The globules are proposed as excretory endproducts of an anaerobic metabolism. Fat globules then accumulate in the host-cell cytoplasm, causing a fatty degeneration. This is adaptive, since it releases the intracellular gregarine into the nutrition-rich gut lumen. Sporonts and gametocysts of the gregarine develop in the gut.

The Incidence Of Macular Pucker After Retinal Detachment Surgery

In a study of 63 cases of macular pucker among 857 patients who underwent retinal detachment repair, we isolated several statistically significant risk factors: preoperative vision of less than 6/15 (20/50); preoperative presence of rolled edges, starfolds, or equatorial ridges; re-operations; choroidal hemorrhage; and age past 30 years. We were unable to confirm the risk associated with vitreous loss, vitreous hemorrhage, and degeneration. Results suggested that macular pucker after detachment surgery is produced by a membrane similar in origin to those causing other forms of periretinal proliferation.

Fluctuations of the Dynamic Topography in the Pacific Ocean

Abstract The dynamic topography of the Pacific Ocean has been mapped and its mean annual and random variability has been investigated using approximately 66,600 hydrographic stations. Largest annual fluctuations are associated with the equatorial current system and are probably due to vertical displacements of the thermocline in response to the changing wind field. In the subtropical gyres and in higher latitudes, dynamic topography varies seasonally in response to the annual cycle of surface layer temperature, but the pattern of dynamic height does not change much between summer and winter. In the western portion of the North Pacific anticyclonic gyre, a U-shaped ridge is developed with its open end pointing east, which separates the western boundary current from the interior of the gyre and links the north equatorial ridge with a ridge at the right flank of the Kuroshio. The variability of dynamic height given by its standard deviation increases from east to west across the Pacific Ocean. Most of this v...

Eupenicillium osmophilum sp. nov.

A new species of the genus Eupenicillium: E. osmophilum is described and illustrated. It is characterized by single asci, lenticular ascospores with 2 closely appressed equatorial ridges and divaricate penicilli.

Surface ornamentation of ascospores in Eupenicillium species.

The ascospores of 21 species ofEupenicillium were examined for surface ornamentation by means of the scanning electron microscope. Two groups of species could be distinguished: one with, and another without distinct equatorial ridges. The former group was further subdivided into four types according to wall ornamentation: reticulate, ribbed, spinulose, and smooth.

Leclercqia complexa gen. et sp. nov., a new Lycopod from the late middle devonian of eastern New York

Leclercqia complexa gen. et. sp. nov. is described as a slender, herbaceous lycopod assigned to the family Protolepidodendraceae. Its laminar leaves are divided into an elongate, acuminate, often recurved central division and two opposite, divided, lateral divisions. Leaves are in a low spiral, eight to ten per gyre. Each has a single vein composed of tracheids. Lateral branches from this vein extend only to the base of each lateral division. The main vein extends to tip of leaf. Stomata are slightly sunken and scattered. The xylem strand is a solid rod with fourteen to eighteen protoxylem ridges; maturation is exarch. Protoxylem is composed of annular, spiral, and reticulate elements. Metaxylem is composed of scalariform elements and tracheids with elongate to oval and uni- to multiseriate bordered pits. Leaf traces rise from protoxylem ridges and extend obliquely to bases of leaves. Sporangia are globose to elliptical, attached to sporophylls by a pad of tissue just proximal to the lateral segments and have sporangia on their walls. Dehiscence occurs along the upper margin of the sporangium and is parallel to midline of sporophyll. Groups of sporophylls alternate with vegetative leaves. Spores in situ 60–85 μ in diameter exclusive of ornamentation, with curvaturae perfectae, spinae 5–9 μ long on an equatorial ridge, and biform ornamentation on distal and proximal faces. Plant is eligulate and probably homosporous.

Surface charges of two types of Bacillus megaterium spores differing in their response to n-butane.

SUMMARY: Rode & Foster (1965) showed that the germination of spores of Bacillus megaterium is sometimes affected by hydrocarbons such as n-butane: one type of spore (al),which responds germinatively to l-alanine and inosine, is inhibited by n-butane; a second type of spore (gn), which responds to glucose and KNO3, is not inhibited, but even accelerated a little by the same compound. The study of the biological activity of these kinds of compounds in respect of bacterial spores is useful in elucidating the mechanism of germination. In this communication, the effect of n-butane on the superficial charges of the spores was investigated; differences in electron microscopical morphology have already been shown by Rode (1968): the alanine type spores have a veined surface with a superficial beaded ultrastructure pattern, the glucose type spores have the well-known prominent equatorial ridge and polar knob appearance.

Spore Germination and Emergence of Bacillus megaterium

Bacillus megaterium spores have a characteristic polar knob and equatorial ridge, or groove. During germination, the spore case appears to split along this ridge, and thus allows the new cell to emerge. Mechanically ground spores also split along this ridge, one part of the spore case being hinged to the other, the ridge being evident along a free edge. The equatorial ridge appears to be an area of suspectibility to mechanical pressures and, perhaps, in normal germination, to enzymic action as well.

More about Isoetes Lechleri Mett.

Material representative of this species is now becoming available from a somewhat extended range in South America, and some of recent collection reveals a tendency to variation in important characters. addition to the plants of Killip and Smith from Colombia, on which was based the variety Colombiana (AMERICAN FERN JOURNAL, Vol. 19, p. 18, et seq.), I have received from Dr. W. R. Maxon the following: Venezuela. Laguna di Apontaderos, Mer. floating on water, January 21st, 1929. H. Pittier, No. 13242. U. S. N. Herb. No. 1440618. These plants have the small corm of the species. The leaves are long and slender, often 30 cm. as compared with the 10-13 cm. of Braun's description for I. Lechleri, and 6-7 cm. for I. Karstenii from Venezuela, which latter was afterwards included in the former. As compared with the var. Colombiana, the tips of the leaves are less acute, and the equatorial ridge of the megaspore is better developed. Diameter of megaspore, 376-517 p. Microspores were not discovered. The velum seems to be complete. Bolivia. La Paz. In einem kleinen See, in der Kordillera. Alt. sobre Mar 4300 m. Dr. Otto Buchstein. No date. U. S. N. Herb. No. 1541653. The corm is small, as usual, and the leaves are about 11 cm. long, bright green, tips brown but not setaceous. Wings at base with some brown color, mostly in lines. Velum apparently complete. Ligule dull salmon, large, ovate, apparently mineralized, brittle. Sporangium thinwalled, small. Megaspores 330-396 p diameter, either pure white or suffused with a pale shade of chocolate brown, mostly smooth, often polished, occasionally slightly wrinkled. The equatorial ridge of medium de129