Seasonal reproduction in the seastar Dytaster grandis from 4000 m in the north-east Atlantic Ocean

1990 ◽  
Vol 70 (1) ◽  
pp. 173-180 ◽  
Author(s):  
P. A. Tyler ◽  
D. S. M. Billett ◽  
J. D. Gage
Keyword(s):  
Seasonal Reproduction ◽  
Ne Atlantic ◽  
East Atlantic ◽  
Environmental Forcing ◽  
Sea Floor ◽  
North East ◽  
The North ◽  
History Of ◽  
Feeding Larva

Examination of the reproductive biology of the abyssal seastar Dytaster grandis taken at different times of the year in the NE Atlantic suggests seasonal reproduction that is related to the seasonal pulse of phytodetritus to the deep-sea floor. Although this seastar is an omnivore, the availability of this labile organic material may fuel vitellogenesis during the summer and autumn months. The egg size suggests planktotrophic larval development. Spawning occurs in the early part of each year to allow the zygote to develop into a feeding larva to coincide with the downward flux of phytodetritus. Thus the flux of detritus may constitute an environmental forcing pressure at least at two points in the life history of D. grandis.

An Account of Schistocerca flavofasciata (De Geer 1773) in Trinidad (Orthoptera : Acrididae)

1943 ◽  
Vol 34 (4) ◽  
pp. 291-310 ◽  
Author(s):  
D. Keith McE. Kevan
Keyword(s):  
Schistocerca Gregaria ◽  
Annual Rainfall ◽  
South American ◽  
Tropical Agriculture ◽  
North East ◽  
The North ◽  
Great Economic Importance ◽  
History Of ◽  
Solitary Species

The genus Schistocerca is one of very great economic importance, since it includes the Desert locust of the Old World, Schistocerca gregaria (Forsk.) and the South American locust, S. paranensis (Burm.). It was therefore considered of value to study the life history of one of the solitary species living in Trinidad, and the present investigations were made during 1942 at the Imperial College of Tropical Agriculture at St. Augustine.The climate of Trinidad is humid tropical. The annual rainfall over nineteen years at St. Augustine averaged 68·4 inches, but in the north-east of the Island the rainfall is over 100 inches per annum, falling to below 60 inches on the West coast. The rainy season usually begins about June, with a break in August or September, and lasts till the end of the year or the early part of January. November may be taken as one of the wettest months with a rainfall of about 11·5 inches (at St. Augustine), while more than half an inch is not usual for April. The humidity in November averages about 85 per cent. in the morning and 77 per cent. in the afternoon, but it is still high in April, being 75 per cent. and 64 per cent. for morning and afternoon respectively. The night humidities are even higher. The temperature remains practically constant throughout the year, averaging about 84°F. (29°C.) during the day, and 74°F. (23·3°C.) at night. The temperature may reach 95°F. (35°C.) during the day in the dry season, but it seldom falls as low as 65°F. (18·3°C.) at night.

Nautical Chart Standardization

1983 ◽  
Vol 36 (3) ◽  
pp. 468-479
Author(s):  
D. W. Newson
Keyword(s):  
Large Scale ◽  
East Atlantic ◽  
Nautical Chart ◽  
North East ◽  
The North ◽  
History Of ◽  
The North Sea ◽  
Successful Establishment ◽  
Atlantic Area ◽  
Two Bodies

This paper deals with the work of the International Hydrographic Organisation (IHO) during the last ten years towards the standardization of nautical charts. The work began with the devising of a regional scheme of medium- and large-scale sheets of the north-east Atlantic area, to be co-produced by member nations as contributions to an International (INT) set of charts. It subsequently became clear that, as well as the scheme, a detailed set of specifications would be necessary to secure uniformity of choice of symbols and abbreviations throughout the International series, and also in the various national chart series of which it would form a part.The history of nautical chart standardization has recently been traced by Ritchie – gradual at first after the beginning of the International Hydrographic Bureau in 1921, and later speeding up when the International Hydrographic Conference of 1967 established a study which led to two series of INT charts on very small scales. After this the process gathered further speed with the successful establishment of the two bodies with whose work this paper is primarily concerned: the North Sea International Chart Commission (NSICC) in 1972 and the Chart Specifications (later Standardization) Committee (CSC) in 1977. The ten-nation NSICC, in drawing up the network of INT sheet-lines for its area, established the principles on which such schemes would be extended worldwide and also did extensive groundwork for the Chart Specifications of the IHO. These were completed for worldwide application by the seventeen-nation CSC.

The ecology and reproductive biology of Cherbonniera utriculus and Molpadia blakei from the N.E. Atlantic

1987 ◽  
Vol 67 (2) ◽  
pp. 385-397 ◽  
Author(s):  
P. A. Tyler ◽  
D. S. M. Billett ◽  
J. D. Gage
Keyword(s):  
New Genus ◽  
Great Variability ◽  
The Arctic ◽  
New Genus And Species ◽  
East Atlantic ◽  
Norwegian Sea ◽  
The Past ◽  
North East ◽  
The North ◽  
History Of

The Molpadiida is an order of sea cucumbers identified by their stout body, the posterior region narrowing to simulate a tail and the absence of tubefeet. Typically they inhabit muddy environments from shallow water to abyssal depths. In the past the great variability in the taxonomic characters of this order has led to the formation of many genera and species (Heding, 1931, 1935), but more recently it has become apparent that many diagnostic characters change markedly during the life history of these holothurians and as a result fewer species are now recognised (Deichmann, 1940; Pawson, 1977). In a revision of the Atlantic molpadiids Deichmann (1940) recorded just three species from the north-east Atlantic (Molpadia blakei, M. musculus and Hedingia albicans) with a further three species from the Arctic Ocean and Norwegian Sea (M. arctica, M. borealis and Eupyrgus scaber). To these Sibuet (1974) added the new genus and species Cherbonniera utriculus found in the Bay of Biscay.

Organic and siliceous protistan scales in north-east Atlantic abyssal sediments

2006 ◽  
Vol 86 (4) ◽  
pp. 679-688 ◽  
Author(s):  
Andrew J. Gooday ◽  
Genoveva F. Esteban ◽  
Ken J. Clarke
Keyword(s):  
Deep Sea ◽  
Small Samples ◽  
Heterotrophic Flagellate ◽  
Heterotrophic Flagellates ◽  
East Atlantic ◽  
Sea Floor ◽  
North East ◽  
The North ◽  
Marine Habitats ◽  
Deep Sea Sediments

We report the occurrence of a high diversity of minute (∼1 μm diameter) organic and siliceous protistan scales in small samples (total volume ∼35 μl) of superficial sediment from the Porcupine Abyssal Plain (PAP), north-east Atlantic (4850 m water depth). Many exhibit characters by which they can be identified to species. The organic scales belong to the haptophyte genera Chrysochromulina (8–9 species), Chrysocampanula and Dolichomastix (1 species each). The siliceous scales belong to the chrysophytes Paraphysomonas vestita and Meringosphaera sp. and to the heterotrophic flagellate genus Thaumatomastix (T. dybsoeana, T. formosa, Thaumatomastix sp.). As far as we are aware, this is the first time that non-calcareous protistan scales have been observed in deep-sea sediments (although siliceous skeletal plates and cysts are reported). All scales probably originated from the upper water column and were delivered to the deep-sea floor on rapidly sinking detrital aggregates. However, naked heterotrophic flagellates are known to thrive in abyssal sediment habitats and so the possibility that some scale-bearing protists also live in benthic deep-sea environments cannot be eliminated. Many species identified at the PAP site are common in coastal marine waters around Europe; some occur as far afield as Tasmania and New Zealand. Five Chrysochromulina species are known from central oceanic areas, including parts of the North Atlantic, while another species, C. pringsheimii, is reported from a British freshwater lake. We retrieved ∼15% of the 55 named Chrysochromulina species (∼8% of the estimated total number of species in this diverse group) in the ∼35 μl of abyssal sediment. Because the scales can persist and be identified after cell death, they may provide useful time- and space-averaged information about the distribution of protist species in marine habitats. The long-term fate of the scales on the sea-floor is unknown. It is possible that at least some of the organic scales are preserved as microfossils in deep-sea sediments.

Ras al Khaimah: further archaeological discoveries

Antiquity ◽  
1976 ◽  
Vol 50 (200) ◽  
pp. 216-222
Author(s):  
Beatrice De Cardi
Keyword(s):  
United Arab Emirates ◽  
The State ◽  
Focused Attention ◽  
North East ◽  
The North ◽  
History Of ◽  
The City

Ras a1 Khaimah is the most northerly of the seven states comprising the United Arab Emirates and its Ruler, H. H. Sheikh Saqr bin Mohammad al-Qasimi, is keenly interested in the history of the state and its people. Survey carried out there jointly with Dr D. B. Doe in 1968 had focused attention on the site of JuIfar which lies just north of the present town of Ras a1 Khaimah (de Cardi, 1971, 230-2). Julfar was in existence in Abbasid times and its importance as an entrep6t during the sixteenth and seventeenth centuries-the Portuguese Period-is reflected by the quantity and variety of imported wares to be found among the ruins of the city. Most of the sites discovered during the survey dated from that period but a group of cairns near Ghalilah and some long gabled graves in the Shimal area to the north-east of the date-groves behind Ras a1 Khaimah (map, FIG. I) clearly represented a more distant past.

scholarly journals Thrust–wrench interference tectonics in the Gulf of Cadiz (Africa–Iberia plate boundary in the North-East Atlantic): Insights from analog models

2011 ◽  
Vol 289 (1-4) ◽  
pp. 135-149 ◽  
Author(s):  
João C. Duarte ◽  
Filipe M. Rosas ◽  
Pedro Terrinha ◽  
Marc-André Gutscher ◽  
Jacques Malavieille ◽  
...  
Keyword(s):  
Plate Boundary ◽  
Gulf Of Cadiz ◽  
East Atlantic ◽  
North East ◽  
The North ◽  
Gulf Of Cádiz ◽  
Analog Models

Exceptional influx of oceanic species into the North Sea late 1997

1999 ◽  
Vol 79 (4) ◽  
pp. 737-739 ◽  
Author(s):  
M. Edwards ◽  
A.W.G. John ◽  
H.G. Hunt ◽  
J.A. Lindley
Keyword(s):  
North Sea ◽  
Indicator Species ◽  
Climatic Conditions ◽  
Historical Evidence ◽  
East Atlantic ◽  
North East ◽  
The North ◽  
The North Sea ◽  
Oceanic Species

Continuous Plankton Recorder records from the North Sea and north-east Atlantic from September 1997 to March 1998 indicate an exceptional influx of oceanic indicator species into the North Sea. These inflow events, according to historical evidence, have only occurred sporadically during this century. This exceptional inflow and previous inflow events are discussed in relation to their similarity in terms of their physical and climatic conditions.

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