首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
Evidence on occurrence in catches and characteristic of the spatial-bathymetric distribution and size indices of four species of Cottidae—frog sculpin Myoxocephalus stelleri, brightbelly sculpin Microcottus sellaris, antlered sculpin Enophrys diceraus, and furseal sculpin Stelgistrum stejnegeri—in summer-autumn months in the Okhotsk Sea waters off Kamchatka (site from 51°15′ to 57°20′ N, depths of 11–100 m) are provided. The first three species occur mainly in the northern part of the shelf above 54° N at depths smaller than 30–40 m within a comparatively well warmed surface water mass of seasonal modification at near-bottom temperature values above 6°C at various solid grounds. Maximum catches of S. stejnegeri were recorded only at a site of the western Kamchatka shelf from 54°00′ to 54°20′ N on pebbly-stony ground in a narrow bathy-metric range of 41–60 m on the boundary between the well warmed surface water mass of autumn modification and the cold intermediate water mass at a water temperature below 2°C. Evidence on the size-weight indices of the studied species of Cottidae in trawl catches in the Okhotsk Sea waters off Kamchatka in the study period is provided.  相似文献   

2.
The first capture of the Greenland (or Black) halibut Reinhardtius hippoglossoides in the Arctic Ocean on the border with the East Siberian Sea (79°03′–79°08′ N 139°59′–141°16′ E, 259–277 m) and the repeated findings of the species in the Laptev Sea (78°03′–78°04′ N 132°56′–133°04′ E, 307 m; 78°33′–78°35′ N 138°44′–138°48′ E, 125 m) are reported. Fish (79 specimens with the length of 15.0–44.5 cm) were caught during four bottom trawlings on the edge of the continental shelf of the two seas in the transformed waters of Atlantic origin, as evidenced by the discovery of the indicator species of these waters—the Glacier lanternfish Benthosema glaciale (Myctophidae)—in one of the stomachs of halibut. The other captures of Greenland halibut in the Arctic were also reviewed.  相似文献   

3.
A new aulopodid fish,Hime microps, is described after two specimens from the Nazca submarine ridge (25°43′S, 85°29′W at 160–165 m; 25°42′S, 85°24′W at 162–168 m). This species is related toH. japonica andH. curtirostris but differs in having no pyloric caeca and smaller eyes with the horizontal diameter shorter than the snout length. Specimens ofH. japonica from off Japan, the Hawaiian submarine ridge and the Tasman Sea are compared and found to be morphologically identical.  相似文献   

4.
Antje Burke 《Flora》2013,208(5-6):321-329
Succulent plants in arid areas are believed to be often associated with high altitudes, except where they form the dominant, zonal vegetation such as in the Succulent Karoo Biome of southern Africa. To test this hypothesis the contribution of perennial succulents to inselberg floras was investigated on twenty-two isolated mountains (inselbergs) at four study sites (Etendeka–Barab: 19°34′ S/13°42′ E; Spitzkoppe: 21°49′ S/15°09′ E; Namibrand: 25°17′ S/15°47′ E; and Sperrgebiet: 27°43′ S/16°04′ E) along a nearly 1000 km bioclimatic gradient in the Namib Desert and adjacent areas, from the Succulent Karoo in the south to the northern Namib, and along altitude gradients.The contribution of succulents to the flora clearly increased with altitude at the two central study sites, thus showing a hump-shaped trend along the bioclimatic gradient. No such correlation was found at the northern and southern end of the bioclimatic gradient. The surrounding (rocky) lowlands likely resulted in a more even distribution of succulents throughout the landscape in the north, while the position in the heartland of the succulent flora in southern Africa at the southern-most site, levelled out potential patterns related to altitude. Nevertheless, even here, a fair number of succulents restricted to mountain habitats occur. This is the case in all other study sites, where succulents restricted to mountain habitats are always present.Some perennial succulents, such as Aridaria noctiflora, Euphorbia gummifera and Tetragonia reduplicata indicate an upward movement with increasing distance from the Succulent Karoo, by growing on plains and lowlands in the Succulent Karoo, but only on inselbergs at study sites north of the Succulent Karoo.Many of the mountain specialist succulents are sought after by plant collectors, such as species of Conophytum, Crassula and Lithops. Protecting and monitoring vulnerable populations as well as growing these in horticulture may help to alleviate the pressure on some of these rare species in nature. Preserving genetic material of isolated populations from mountain tops ex situ is another important conservation measure, and particularly important in the view of anticipated climatic change.  相似文献   

5.
《Gene》1997,189(1):127-134
We have analyzed the promoter and the coding sequences of the two homologous histone H1°-encoding genes from Xenopus laevis, here termed H1°-1 and H1°-2. Both genes encode proteins of 193 amino acids and differ at just 16 amino-acid residues. Putative regulatory sequences identified in the promoter region are the same and are highly conserved. However, significant differences exist in the 5′ untranslated regions (UTR) of the transcribed sequences of these two genes, such as several deletions in the 5′-UTR of the H1°-2 gene in comparison with the H1°-1 gene 5′-UTR. The 3′-UTR is a short sequence of about 200 bp which is unexpected compared with the long 3′-UTR of mammalian H1° mRNA, but it is in the same size range as in avian H5 mRNA. Thus, the main differences between these two genes are observed in sequences potentially involved in the regulation of the H1° gene expression such as the 5′-UTR. The two genes are expressed during embryogenesis and in several adult tissues. We discuss these findings in terms of the evolution of histone H1° genes in vertebrates and the appearance of histone H5 in avian species.© 1997 Elsevier Science B.V. All rights reserved.  相似文献   

6.
Detailed studies on sub-Arctic and Arctic marine diatom assemblages contribute to the understanding of spatial distribution patterns and their physical drivers. In this study, diatom species were analyzed from water samples collected with a Niskin bottle rosette combined with a CTD along the West Greenland coast (63°58′N–71°08′N and 50°49′W–59°06′W) during summer 2007. Diatom community was represented mainly by three genera Thalassiosira, Fragilariopsis, and Chaetoceros and linked to observed hydrographic and environmental conditions. Thalassiosira spp. were common in coastal waters (particularly Godthåbsfjord) and linked to increased surface water temperature, typical of summer water stratification in West Greenland. Fragilariopsis spp., along with other dominant species associated with higher geographic latitudes, dominated in Arctic fjords (Uummannaq Fjord-Qaumarujuk Fjord). These species generally characterized coastal waters influenced by melting sea ice and/or glacial ice. Chaetoceros spp. were linked to more saline open marine waters, particularly in the Davis Strait south of 70°N, probably corresponding to weaker water stratification and the influence of the West Greenland Current. The present paper provides new knowledge on diatom assemblages along a south–north climate gradient in West Greenland, which is necessary in order to understand how observed ocean-climate changes influence Arctic marine ecosystems. This study provides a reference for palaeoenvironmental reconstructions using diatom microfossils deposited in the West Greenland marine sediments.  相似文献   

7.
In the Black Sea, the sea anemone Sagartia elegans (Dalyell, 1848) has been found for the first time in the Gulf of Odessa (46°31′60 N, 30°48′ E) and karst caves and grottos of the Western Crimea (45°21′ N, 32°30′ E). Previously, S. elegans was known to inhabit coastal waters of Iceland, the British Isles, and continental Europe from Scandinavia to the Adriatic Sea. According to the available data, this gonochoristic species tends to asexual somatic reproduction through laceration: juvenile polyps develop from separated fragments of the pedal disc. A rich color polymorphism is observed. The numerous clonal populations that are found in caves consist of variously sized and similarly colored polyps. All of them descended from one parental individual.  相似文献   

8.
Intertidal Ulva mats occur annually in winter and spring in the Xiangshan Bay (29°26′–29°34′ N, 121°27′–121°50′ E) of China. Thousands of tons of Ulva biomass have been harvested as edible seaweeds for human consumption for several decades in this region. This investigation was designed to quantify Ulva microscopic propagules associated with the mat, identify species composition, and to analyze intra-species relationships using three molecular markers. Phylogenetic analysis based on the nuclear encoded rDNA internal transcribed spacer region, the plastid encoded large subunit of the ribulose 1,5-bisphosphate carboxylase gene, and the 5S rDNA spacer region showed that the mat was principally composed of Ulva prolifera and Ulva flexuosa. Their propagules were detected in both the water column and sediment. Based on phylogenetic analyses of the 5S rDNA spacer region, mat samples of U. prolifera and U. flexuosa were genetically distinct from the green tide samples in the Yellow Sea and U. flexuosa samples from Jiangsu coasts, respectively, revealing that isolated geographical position of the Xiangshan Bay might result in the maintenance of a distinct Ulva population. The results demonstrate that high-resolution DNA markers have great potential in identification and discrimination at and below the species level.  相似文献   

9.
Diatoms are well preserved in partly laminated Holocene and late Pleistocene sediments on the upper continental slope of central Peru. Accumulation rates of diatom species previously recognized as tropical (oceanic, warm water) and subtropical (neritic, cooler water, upwelling) changed markedly downcore in Kasten cores obtained at 11°15′S, 12°58′S, and 13°37′S latitude. Subtropical species (e.g., Thalassiosira eccentrica “group”, Thalassiothrix frauenfeldii, Chaetoceros spp. resting spores, Delphineis spp.) predominated in late Pleistocene sediments of the two southern cores. A mix of tropical and subtropical diatom assemblages occurred in latest Pleistocene sediments, while tropical species (e.g., Coscinodiscus nodulifer/radiatus, Pseudoeunotia doliolus, Thalassionema nitzschioides var. parva) predominated in the late Holocene sediments. In the northern core latest Pleistocene sediments also contained a mix of tropical and subtropical species. Similarly, late Holocene sediments contained predominately tropical species of diatoms. Neoglacial periods (200–400 yr B.P., 2000–2700 yr B.P.), however, were sometimes characterized by a greater abundance of subtropical species and punctuated periodically with blooms of Skeletonema costatum and Rhizosolenia shrubsolei. It is proposed that during times of Southern Hemisphere cooling, Peruvian coastal waters north of 12°S were subjected to episodic mixing with warmer water masses before being overwhelmed by tropical waters that may have either passed southward across a weakened Equatorial Front or arose from intensified offshore countercurrents. Coastal waters south of 12°S latitude were probably unaffected by the tropical influence. Rather, these waters may have undergone intensified upwelling during the last Glacial epoch.  相似文献   

10.
New species Zanclorhynchus chereshnevi sp. n. has been described. The type series of the new species has been sampled along the shores of Prince Edward Islands (46°55′ S 37°58′ E) in the Southern Ocean at the depth of 170 m. The new species differs from the another representative of the genus, Z. spinifer, by weak arming of the first dorsal fin and the head and by the body proportions and coloration.  相似文献   

11.
The first capture of the flying fish Cypselurus hiraii Abe, 1953 in waters of northern Primorye (Serebryanka Bay, 45°02′ N, 136°39′ E) is recorded, demonstrating the penetration of this warmth-loving species beyond its main range. The morphological features and coloration of a young specimen of 103 mm in TL are described.  相似文献   

12.
The Japanese fringed sculpin Porocottus japonicus Schmidt has been found in the Rynda (44°48′03″ N, 136°23′24″ E) and Vladimira (43°52′36″ N, 135°29′30″ E) (Sea of Japan, Primorskii krai) bays for the first time. This species was formerly known only from the northern Tatar Strait and Aniva Bay. In Primorskii krai, P. japonicus inhabits macrophyte beds in shallow sublittoral waters. It reaches a length of 112 mm during its lifespan of approximately 4 years. Spawning occurs in the winter. The species preys predominantly on polychaetes (82.3% of the food weight).  相似文献   

13.
The dominant mammals occupying the subterranean niche in South America are rodents of the genus Ctenomys, which form a large group of 56 species with chromosome numbers ranging from 2n= 10 to 70. In southern Brazil, Ctenomys minutus is the species with the widest geographic distribution, inhabiting sandy fields and dunes extending from Jaguaruna beach in the state of Santa Catarina to the town of São José do Norte in the state of Rio Grande do Sul. Eleven karyotypes (2n= 42; 2n= 46a; 2n= 46b; 2n= 47a; 2n= 47b; 2n= 48a; 2n= 48b; 2n= 49a; 2n= 49b; 2n= 50a and 2n= 50b) were described for this species and zones of hybridization are also known. A sample of 51 C. minutus specimens was collected from five sampling sites about 20 km apart along the coastal plain of Rio Grande do Sul between the municipalities of Tavares (31°23′S 51°09′W) and São José do Norte (31°52′S 51°54′W). We were able to extend the known geographic distribution of C. minutus by 90 km, from Tavares southwards to São José do Norte. During our study we found five karyotypes (2n= 46b, 47b, 48b, 49b and 50b), four of which (2n= 47b, 48b, 49b and 50b) have not previously been described for this species.  相似文献   

14.
Xu Zhaoli 《农业工程》2007,27(9):3678-3686
Distribution patterns and abundance of the euphausiids were examined in the East China Sea (23°30′ –33°00′N, 118°30′ –128°00′ E) in relation to temperature and salinity. The data were collected in 4 surveys from 1997 to 2000. The density or yield density model was used to predict optimum temperature and salinity of water for euphausiid distribution, and thereafter distribution patterns of euphausiids were determined based on the predicted parameters. Of 23 species, Euphausia pacifica, E. nana, Pseudeuphausia sinica and P. latifrons were numerically dominant. The analyses indicate that Euphausia pacifica is an offshore temperate water species, E. nana is an offshore temperate warm water species, P. sinica is a coastal subtropical water species and P. latifrons is an oceanic tropical water species. The 4 species occupied 4 different water masses, respectively, namely, cold water mass, cold and warm water mixed masses in winter and spring, cold and warm water mixed masses in summer and autumn, and warm water mass, which could be the good designators of individual water masses, respectively. The predicated optimal temperatures for E. tenera, S. carinatum, E. diomedeae, Stylocheiron affine, Nematoscelis sp., N. gracilis, N. atlantica, Stylocheiron sp. and S. suhmii are all > 25°. These species are mainly distributed in southern Kuroshio in winter and spring, Kuroshio, the Taiwan Warm Current and Tsushima Current in summer and autumn, the equatorial waters of Pacific Ocean and the eastern waters of the Taiwan Strait. They are called as oceanic tropical water species. Nematoscelis tenella and T. tricuspidata are referred to as offshore subtropical water species according to their geographic distributions even if they are halobionts. Euphausia sanzoi is considered as a typical offshore subtropical water species, which inhabited waters below 25°. Stylocheiron microphthalma, occupying warm current waters where temperature and salinity are nearly 25° and 34 in summer and autumn, belongs to oceanic tropical water species. In the same way, E. similes, E. mutica, Euphausia sp., E. brevis and E. recurva are classified into offshore subtropical water species in accordance with the optimum temperature and salinity of waters as well as locations and seasons of their occurrence. Optimum temperature, rather than salinity, is a better parameter in determining the distribution patterns of euphausiids.  相似文献   

15.
This paper reports the results of a phytosociological and gradient analysis of the vegetation occurring along an altitudinal gradient from Turi (3100 m) to Cerro León (4250 m) on the western flank of the Andes in northern Chile (22°06′–22°22′ S; 68°15′–68°07′ W). Along the transect, the total cover of vegetation ranges from 2.5% at the lower end to 35.7% at 4000 m altitude. Four major physiognomic zones, including six associations are recognized within the transect studied: (1) The ‘Pre-Puna’ belt (2700–3150 m), characterized by a sparse cover of xerophytic subshrubs, including two associations: Acantholippia deserticola-Franseria meyeniana, which occurs over the sedimentary sands around Turi, and Franseria meyeniana-Helogyne macrogyne-Helianthocereus atacamensis, restricted to ravines and canyons. (2) The ‘Puna’ belt (3150–3850 m), physiognomically dominated by shrubs and presenting the highest vegetational cover, including the: Fabiana densa-Baccharis boliviensis, and Junellia seriphioides-Baccharis incarum-Lampaya medicinalis, associations. (3) The ‘High-Andean’ belt, localized above the ‘Puna’, including the Fabiana bryoides-Adesmia horrida and Oxalis exigua-Mulinum crassifolium associations. (4) The ‘Subnival’ belt, a high mountain semi-desert with a poorly developed vegetation. Only three species occur at the upper vegetational limit (4380 m). The phytosociological scheme proposed in this paper can be paralleled with that by Ruthsatz (1977) for the eastern flank of the Andes. A marked contrast in species richness and phytosociological complexity between these Andean regions is pointed out. Lower species richness of the Chilean transect is related to the presence of the Atacama desert, which extends from the coast up to 2700 m in the study area.  相似文献   

16.
The widely distributed long-finned pilot whale (Globicephala melas) has been reported off the Chilean coast, from Iquique (20°12′S) south to Navarino Island (55°15′S; 67°30′W), but little is known about its biology or ecology in the region. Here, we report on the prey of this species, identified by stomach content analyses from animals stranded on Holget Islets, Beagle Channel, southern Chile in August 2006. The stomachs of seven individuals (six females and one male) contained cephalopod remains. The prey composition found in these southern Chilean pilot whales was similar to that described in other parts of the world and the Southern Ocean. This is the first report on the feeding habits of this species from Chile.  相似文献   

17.
A specimen ofToxotes jaculator (Pallas, 1767) (Pisces: Toxotidae) was collected from the mouth of Urauchi River (24°23′55″N, 123°46′48″E), Iriomote Island, Ryukyu Islands, Japan. This species was recorded for the first time from the Japanese Archipelago. Its occurrence in Japan is the northern-most record of this species.  相似文献   

18.
The horizontal and vertical distributions of two species of endemic, burrowing mud crabs Helice crassa Dana 1851 (Grapsidae) and Macrophthalmus hirtipes (Jacquinot 1853) (Ocypodidae) are described for the Avon-Heathcote Estuary (43°33′S: 172°44′E), Christchurch, New Zealand. Substratum preference is shown to be the most important factor influencing mud crab distribution, but lack of tolerance to salinities below 4‰ is also a significant factor preventing M. hirtipes from occurring at points close to freshwater input. Both species had similar sediment organic content and particle size requirements. Helice crassa was concentrated in well-drained, compacted sediments above mid-tide level, whilst Macrophthalmus hirtipeswas found in waterlogged areas below mid-tide level. This vertical separation is shown not to be caused by differential desiccation tolerances, but by feeding and burrowing adaptations related to these different substrata.  相似文献   

19.
Morphological variation among natural populations is a phenomenon commonly observed in marine invertebrates and well studied, particularly, in shelled gastropods. The nassariid Buccinanops globulosus is interesting to study shell shape variation because it exhibits strong interpopulation differences in life history features, including maximum size, fecundity and growth rate. In this study, we examined the pattern of variation in size and shell shape among populations and between sexes of B. globulosus (Bahía San Antonio 40°29′S 63°01′W, Playa Villarino 40°45′S 64°40′W and Bahía Nueva 42°46′S 65°02′W). In particular, we used geometric morphometric techniques to test: (1) whether the two components of shell morphology (size and shape) are independent and (2) whether shape differences between sexes are consistently found among populations, regardless of their body sizes. Our results show shell shape variation between the populations of B. globulosus of northern Patagonia. Intra-specific shell shape variation is affected by body size, indicating allometry. Regardless of the size differences, individuals from Playa Villarino have high-spired shells, and shorter apertures and wider columellar area than individuals from the other populations. Also, sex-related shape differences were consistently found at each population, thus suggesting a common sexual dimorphism in shell morphology for this species. The functional significance of the variability found is discussed in terms of the flexibility of developmental programmes for morphology as well as the evolution of phenotypic plasticity.  相似文献   

20.
In the coastal pine forests (Pinus pinea and Pinus pinaster) of Ravenna (Italy) along the Adriatic coast, many pine trees are stressed or dying. In this paper we present ground elevation, depth to watertable, salinity of groundwater and vegetation species richness data within one of the coastal pine forests and some wetlands north of the Bevano River between LAT. 44°23′10″ and LAT. 44°20′21″ and between LONG. 12°17′25″ and LONG. 12°19′33″. The data are presented areally and along a 50 m long transect perpendicular to the coast to study the cause of distress in the pine forest and in different water pools within the wetlands. The findings were compared to published values of tolerance to salinity for 39 plant species typical of the area and incorporated into a web application to help nature managers in assessing or adjusting water salinity in relation to the vegetation species present. The pine trees are relatively tolerant to salinity (up to 12 g/l) but cannot survive a shallow watertable. On the other hand, species richness or biodiversity in this area is promoted by a shallow watertable and low salinity.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号