72 resultados para Rhinodrilus alatus
Resumo:
Upper Berriasian to lower Aptian calcareous nannofossil assemblages have been studied from a siliciclastic deep-sea fan complex and a subjacent limestone sequence drilled beneath the lower continental rise in the western North American Basin, 270 miles (435 km) off Cape Hatteras, North Carolina (USA). Sharp lithologic facies changes and reworking by turbidites complicate the biostratigraphic interpretation, but provide an excellent opportunity to better distinguish "nearshore" from open-ocean nannofossil species, and to investigate the introduction of neritic taxa into the deep-see environment, a phenomenon that appears to have been widespread within the circum-North Atlantic during Neocomian times. Well-preserved assemblages in dark, carbonaceous claystones were probably displaced from the oxygen minimum zone along the upper slope or outer shelf. Neritic, continental margin species prevalent in this facies include the holococcolith Zebrashapka vanhintei n. gen., n. sp., Lithraphidites alatus magnus n. spp., Pickelhaube furtiva n. gen., and a host of nannoconids and micrantholiths. A qualitative evaluation of widely used guide fossils suggests that the triad of proposed markers for the base of Roth's Zone NC3 make their first appearances in the following (ascending) order: Diadorhombus rectus, TUbodiscus verenae, Calcicalathina oblongata. Of these, we chose the nominative species for the zone, T. verenae, to mark its base and to approximate the Berriasian/Valangian boundary. Cyclagelosphaera deflandrei is strongly affected by diagenesis and is therefore not a reliable index species for the base of Zone NC4 near the Valanginian/Hauterivian boundary (the last occurrence of T. verenae is also not suitable there). In addition, Lithraphidites bollii, a form apparently confined to the low latitudes of the Tethyan region, was absent at the more temperate Site 603 and not available as a subzonal marker for the upper Hautervian-lower Barremian (mid-NC4 and mid-NC5, respectively). Cruciellipsis cuvillieri, however, provides a reliable datum just below the Hauterivian/Barremian boundary (base of NC5), despite the potential for reworking in this section. Nannoconids tend to be reworked in this section, and do not provide trustworthy forms to mark the Barremian/Aptian boundary (base of NC6). Hayesites irregularis n. comb, probably does provide a useful first appearance datum within the lower Aptian, if it is not confused with a more birefringent and globular form, Rucinolithus terebrodentarius n. sp. Rhagodiscus angustus is mimicked by a similar form (Zeughrabdotusl pseudoangustus n. sp.), which apparently ranges down to the Hauterivian, thus Lithastrinus floralis provides a more useful first appearance datum for the base of the middle-upper Aptian Rhagodiscus angustus Zone (NC7). Aside from the new taxa mentioned above, the following are also described: Cretarhabdusl delicatus n. sp. and Cyclagelosphaera jiangii n. sp.
Resumo:
Deep Sea Drilling Project Leg 79 recovered Cretaceous nannofossils at two localities, Sites 545 and 547. Species diversity of the Cretaceous coccoliths is high, and the assemblages range in age from early Valanginian-early Hauterivian to latest Maestrichtian. Site 545 and portions of Site 547 can be combined to form a composite section ranging from the upper Aptian-lower Albian to the middle to upper Cenomanian. As defined by nannofossil events, this section represents a complete record of sedimentary deposition. The interval appears to be the most extensive and complete Cretaceous section yet drilled off the Northwest African margin. The Campanian and Maestrichtian sediments found at Site 547 (Hole 547A) are the youngest Cretaceous strata found on the Northwest African margin. Like the middle Cretaceous sections, the uppermost Maestrichtian of this interval also represents a complete record of sedimentation.
Resumo:
This paper examines the use of Acacia as a nurse crop to overcome some of the ecological and economic impediments to reforestation of degraded areas dominated by grasses including Imperata cylindrica. The study site at Hai Van Pass in central Vietnam was initially reforested using Acacia auriculiformis. After 8 years these stands were thinned and under-planted with Hopea odorata, Dipterocarpus alatus, Parashorea chinensis, Tarrietia javanica, Parashorea stellata, Scaphium lychnophorum, Peltophorum dasyrhachis var. tonkinensis and other high-value native species. At the time of field assessment (early 2004), the Acacia trees were aged between 16 and 18 years and basal area ranged from 9 to 13 m(2) ha(-1) after several thinnings. Acacias facilitated the establishment of native species, but after 6-7 years of growth, further thinning is needed to maintain growth rates. In addition to assisting the establishment of native species, the Acacia nurse crop should provide a revenue stream (NPV about US$ 180, or IRR 19%) sufficient to cover the establishment costs of the underplanted native species (about US$ 100). (c) 2006 Published by Elsevier B.V.
Resumo:
In this research, 9 species of local and introduced fishes of the Zayandehroud River in Esfahan province (in the Sarmatian region belonging to the large paleoarctic fauna) in 6 seasons (winter 2003, spring, summer, autumn and winter 2004 and summer 2005) were parasitologically studied. The local fishes included alburnoides bipunctatus, Alburnus maculatus, Aphanius vladykovi, Capoeta aculeata & Capoeta damascina & the introduced fishes included Aristichthys nobilis, Carassius auratus, Ctenopharyngodon idella and Cyprinus carpio. Upon being hunted, the fishes were transferred alive to Esfahan Aquatics Breeding Center and physiologically studied after the determination of their species and genus by identification keys Berg (30), Coad (31), Saadati (51), Abdoli (20) and Holchic (38). 32 species of parasites were totally identified as follows: 6 Protozoan species including Ichthyophthirius multifiliis, 5 Trichodina species, 2 Myxobolus species including Myxobolus cristatus & Myxobolus saidovi, 16 monogenea species including Dactylogyrus alatus. D. anchorutus, D. baueri, D. chalcalburni, D. chramuli, D. extensus, D. gracilis, D. lamellatus, D. lenkorani and D. pukher, 4 Dactylogyrus spp. 2 Gyrodactylus species, 1 species of Digenea, Diplostomum spthaceum, 4 species of Cestoda including Bothriocephallus gowkongensis, khawia armeniaca, Ligulaintestinalis. Caryophyllaeus sp. 1 Acanthocephala: Acanthocephalo rhynchoides cholodkowsky, 2 species of the crustaceans including the mature & copepodian stages of Lernaea cyprinacea & 1 sp of the genus Lamproglena. Out of all the 166 pcs of the fishes hunted in this research, 127 fishes (76.5%) were infected, and 39 fishes (23.50%) were not infected. In the fishes studied, having 14 of 32 species of the parasites identified, Capoeta aculeata displayed the most variety of infection, and having only 1 sp of the parasites. Aristichthys nobilis displayed the least variety of infection. The new findings of the research will follow: Myxobolus saidovi sp is reported for the 1st time from Iran's fresh water fishes, Alburnus maculatus and Capoeta aculeata are new hosts for M. saidovi and M. cristatus, respectively. Regarding monogenea Capoeta damascina & C. aculeata were reported as the new hosts for parasite D. pukher. The presence of D. pukher the infection of Capoeta aculeata with D. chramuli, D. lenkorani and D. gracilis in the Zayandehroud river were the 1st report. Regarding the Cestodea, Bothriocephalus gowkongensis was reported to be hosted by Aphanius Vladykovi for the 1St time in Iran.