ALBERT

Description: High-resolution seismic reflection and Sea Beam bathymetric data provide insights into the processes of sediment offscraping and accretion in the Middle America Trench off southern Mexico. Thick terrigenous sediments that are transported down Ometepec Canyon and accumulate along the trench floor are scraped off the oceanic plate and accreted in thrust packets to the lower trench slope. The packets offscraped represent most of the trench strata. Underlying hemipelagic deposits that accumulate on the seafloor seaward of the trench are subducted landward of the toe of the slope. Horizontal displacement on the thrust is less than 1 km. Leading edge folds are the surface expressions of the thrusts and strike subparallel to the base of the trench slope. The folds are continuous for as much as 10 km and have amplitudes as high as 200 m and wavelengths of 0.5 to 2 km. Folds are best developed along sections of the trench with interbedded silty turbidite and mud deposits. Fold are absent where thick coarse-grained fan deposits occur. Thickening of the thrust packets occurs by large-scale thrust duplication, by layer-parallel shortening, and by deposition of material that slumps off the leading edge of older upslope thrust blocks.

Description: This check-list is a compilation of the marine molluscs recorded from Norway and the abyssal depths of the Norwegian Sea. Molluscs not recorded from the Norwegian fauna but found on the North Sea plateau, the British North Sea coast, the Swedish west coast, and in Danish waters are also included. Distributional data are provided for each species. Most commonly used synonyms are listed, together with type species for each accepted generic name. Systematical code numbers are included for easy retrieval of information. An alphabetical index of all generic names mentioned concludes the check-list. Recent taxonomic alterations and all distributional records are documented by literature references.

Description: Morphological characteristics of two large females of Haliphron atlanticus STEENSTRUP (= Alloposus mollis VERRILL) are described and illustrated. The soft and gelatinous body, the shape of the mantle aperture, the formation of the funnel and adhesive apparatus, and the straplike septa connecting the mantle and funnel and containing the stellate ganglion are characteristic features of the species. One specimen, weighing 41 kg after fixation, was found dead near Bergen (60°14′ N, 5°16′ E) in May 1983. The other, weighing 25 kg after being frozen, was caught alive at 210 m off Vestvägöy in the Lofoten archipelago (68°20′ N. 14°14′ E) in November 1984. It was possibly feeding on the prawn, Pandalus borealis KRøYER. Both specimens had arms partly missing and web torn, but were otherwise well preserved. Previous records of H. atlanticus are confined to tropical and warm-temperate areas. The present findings represent the first records from north of 42° N.

Description: We have determined the centroid depths and source mechanisms of 12 large earthquakes on transform faults of the northern Mid-Atlantic Ridge from an inversion of long-period body waveforms. The earthquakes occurred on the Gibbs, Oceanographer, Hayes, Kane, 15°20′, and Vema transforms. We have also estimated the depth extent of faulting during each earthquake from the centroid depth and the fault width. For five of the transforms, earthquake centroid depths lie in the range 7–10 km beneath the seafloor, and the maximum depth of seismic faulting is 14–20 km. On the basis of a comparison with a simple thermal model for transform faults, this maximum depth of seismic behavior corresponds to a nominal temperature of 900° ± 100°C. In contrast, the nominal temperature limiting the maximum depth of faulting during oceanic intraplate earthquakes with strike-slip mechanisms is 700° ± 100°C. The difference in these limiting temperatures may be attributed to the different strain rates characterizing intraplate and transform fault environments. Three large earthquakes on the 15°20′ transform have shallower centroid depths of 4–5 km and a maximum depth of seismic faulting of 10 km, corresponding to a limiting temperature of 600°C. The shallower extent of seismic behavior along the 15°20′ transform may be related to a recent episode of extension across the transform associated with the northward migration of the triple junction among North American, South American, and African plates to its present position near the transform. The source mechanisms for all events in this study display the strike-slip motion expected for transform fault earthquakes; slip vector azimuths agree to within 2°–3° of the local strike of the zone of active faulting. The only anomalies in mechanism were for two earthquakes near the western end of the Vema transform which occurred on significantly nonvertical fault planes. Secondary faulting, occurring either precursory to or near the end of the main episode of strike-slip rupture, was observed for five of the 12 earthquakes. For three events the secondary faulting was characterized by reverse motion on fault planes striking oblique to the trend of the transform. In all three cases the site of secondary reverse faulting is near a compressional jog in the current trace of the active transform fault zone. We find no evidence to support the conclusions of Engeln, Wiens, and Stein that oceanic transform faults in general are either hotter than expected from simple thermal models or weaker than normal oceanic lithosphere.

Description: Maturing females of the octopod Japetella diaphana (Hoyle) develop a luminous oral ring. Studies of specimens of different size show that this structure develops from a muscular ring which undergoes great cellular proliferation, associated with gradual degeneration of the original muscle. The light‐producing cells (photocytes) have a relatively uniform cytoplasm whose most characteristic components are small mitochondria, granular aggregates and microtubular or microfibrillar bundles. It is concluded that the original muscle tissue is not transformed directly into luminous tissue. Possible uses of the luminescence are discussed, based on the postures adopted by live specimens in shipboard aquaria.

Description: The first recorded specimens of Scaeurgus unicirrhus from the South-East Atlantic are described. Five males and two females were captured on the Valdivia Bank, Walvis Ridge, between 24 and 27°S, 400 miles off the Namibian coast. They are compared with specimens caught from other areas, and historical and geographic surveys of the species are made.

Description: The publications of Matsuoka (1983) and Bujak (1984) on dinoflagellate cysts from the Neogene of Japan and the Paleogene‐Neogene of the Bering Sea‐northern North Pacific areas, respectively, resulted in the erection of two new species by each author which are synonymous. Impagidinium pacificum Bujak and Spiniferites ovatus Bujak are therefore designated junior synonyms of Impagidinium japonicum Matsuoka and Spiniferites hexatypicus Matsuoka. Another species, Spiniferites ovatus Matsuoka, does not occur in the material examined by Bujak. Specimens assigned by Matsuoka to Nematosphaeropsis labyrinthea and Tectatodinium pellitum are reassigned to Nematosphaeropsis lemniscata Bujak and Filisphaera filifera Bujak, respectively. The species Reticulatosphaera stellata Matsuoka, which Matsuoka designated the type species of his new genus Reticulatosphaera, is designated a subjective junior synonym of a species originally named by Benedek (1972) as Cleistosphaeridium actinocoronatum. C. actinocoronatum is transferred to Reticulatosphaera and becomes the type‐species of this genus. Specimens assigned to Areoligera senonensis Lejeune‐Carpentier sensu Gocht 1969 by Matsuoka (1974, 1983) and Tanyosphaeridium fusiform by Matsuoka (1974) are reattributed to Systematophora ancyrea and Distatodinium fusiforme (Matsuoka) comb, nov., respectively. Bujak also erected eight Eocene to Pleistocene concurrent‐range zones, two of which were named the I. pacificum and Spiniferites ovatus Zones. These are renamed the I. japonicum and 5. hexatypicus Zones, and the zonation is modified to extend the Trinovantedinium boreale Zone into the early Oligocene, and to restrict the S. hexatypicus Zone to the Miocene.

Description: The Imperial Cormorant Phalacrocorax atriceps is an inshore foraging, diving seabird (Cooper 1985) distributed throughout the southern hemisphere south of 45°S (Watson 1975). A brief description of the diet of the Imperial Cormorant at Marion Island has been published (Blankley 1981). We present here a more comprehensive report based on food samples collected throughout the year.

Description: Chemical composition of Zostera marina L. seed and shoots was determined. Morphology and histochemistry of mature seeds were studied by fluorescence, brightfield and scanning electron microscopy to locate storage constituents in the seed. Starch content in the mature seed was 51% and was the major storage reserve in the embryo and a minor component in the testa. Starch in the shoots ranged from 0.3 to 2.3%. Protein, located in the embryo as small protein bodies, comprised about 9.0% of the seed. Protein in shoots ranged from 6–15%. Protein quality of both seeds and shoots resembled corn in composition, and the first limiting amino acid was lysine. Shoots were high in minerals, fiber and ash, while seeds were lower in these constituents. Fat was low (0.3–1.7%) in both shoots and seeds.

Description: Feeding strategies are different when adult Illex illecebrosus prey on large (trout) and small fish (mummichogs). Attacks on trout are characterized by (1) rotation as the squid changes from tail‐first to head‐first swimming; (2) an approach phase involving rapid acceleration towards the prey; (3) a tracking phase where the squid slowly follows the trout; (4) the capture phase. No tracking phase is present in attacks on mummichogs. These differences in feeding strategies can be explained by performance limitations of the squid jet propulsion system. Head‐first acceleration rates in Illex are low (max. = 12 m • s−2) and maneuverability poor compared to fish. A large fish could thus out‐perform an attacking squid if forced into evasive action. The tracking phase is a type of oceanic stalking strategy designed to bring the squid into close proximity to larger fish. The behaviour is not necessary when attacking small fish due to their low swimming speeds.