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.
Embryonic, larval, and juvenile development of an Indian cyprinid fish, Chela dadiburjori, is described from laboratory-reared specimens. The eggs, measuring 0.7–0.9mm in diameter, were demersal, almost spherical in shape, transparent and unpigmented, with a pale yellow yolk and no oil globule. Hatching occurred 50–61h after fertilization at ca. 27°C. The newly hatched larvae, measuring 2.4–2.6mm in body length (BL), had melanophores on the body with 14–16+14–17=29–31 myomeres. Two dark transverse bands on the ventral body surface and one melanophore on the lower margin of the eye in newly hatched larvae were diagnostic. Additionally, a cement organ for adhering to objects was present on the forehead of yolk sac larvae <3.1mm BL. The yolk was completely absorbed at 3.5mm BL. Notochord flexion was initiated at 5.0mm BL and finished at 6.0mm BL. Aggregate numbers of all fin rays were completed at 9.2mm BL. Squamation was initiated on the caudal peduncle at 8.0mm BL and completed at 10mm BL. The eggs of C. dadiburjori resembled those of the closely related species Devario malabaricus and Danio rerio. The larvae and juveniles of C. dadiburjori were also similar to those of the latter species in general morphology, especially the presence of body melanophores in newly hatched individuals and a distinctive lateral streak on the head during the period from yolk sac to postflexion larvae. However, early yolk sac larvae of C. dadiburjori were more similar to those of Devario malabaricus than Danio rerio in having a cement organ on the forehead. Larvae and juveniles of C. dadiburjori differed from those of the latter two species in pigmentation on the ventral body surface at hatching and around the mouth during the period from preflexion to early postflexion larvae and in having a dark lateral streak or band on the body in postflexion larvae and juveniles.  相似文献   

2.
Chromosome preparations of 30 specimens of Oryzomys subflavus trapped in eight Brazilian localities were C-, and G-banded and analyzed by fluorescence in situ hybridization (FISH). Two karyotypes were found, 2n=50/FN=64, at three coastal localities of the Atlantic Forest domain, and 2n=58/FN=70 at two sites located in the Cerrado biome, Brazil Central. Two fluorescence in situ hybridization (FISH) patterns of the telomeric sequence (T2AG3)n were observed: in both karyotypes the probes hybridized to the telomeres of all chromosomes and also a hybridization signal in the centromeric regions of two autosome pairs was seen in the 2n=50 karyotype. These results, together with the occurrence of other diploid numbers described in the literature, suggest that O. subflavus is a complex species, bearing fusion/fission rearrangements proper to the different biomes which it inhabits.  相似文献   

3.
Behavioral and physiological responses to hypoxia were examined in three sympatric species of sharks: bonnethead shark Sphyrna tiburo, blacknose shark, Carcharhinus acronotus, and Florida smoothhound shark, Mustelus norrisi, using closed system respirometry. Sharks were exposed to normoxic and three levels of hypoxic conditions. Under normoxic conditions (5.5–6.4mg l–1), shark routine swimming speed averaged 25.5 and 31.0cm s–1 for obligate ram-ventilating S. tiburo and C. acronotus respectively, and 25.0cm s–1 for buccal-ventilating M. norrisi. Routine oxygen consumption averaged about 234.6 mg O2kg–1h–1 for S. tiburo, 437.2mg O2kg–1h–1 for C. acronotus, and 161.4mg O2 kg–1 h–1 for M. norrisi. For ram-ventilating sharks, mouth gape averaged 1.0cm whereas M. norrisi gillbeats averaged 56.0 beats min–1. Swimming speeds, mouth gape, and oxygen consumption rate of S. tiburo and C. acronotus increased to a maximum of 37–39cm s–1, 2.5–3.0cm and 496 and 599mg O2 kg–1 h–1 under hypoxic conditions (2.5–3.4mg l–1), respectively. M. norrisi decreased swimming speeds to 16cm s–1 and oxygen consumption rate remained similar. Results support the hypothesis that obligate ram-ventilating sharks respond to hypoxia by increasing swimming speed and mouth gape while buccal-ventilating smoothhound sharks reduce activity.  相似文献   

4.
The larval development and food habits of the marbled parrotfish, Leptoscarus vaigiensis (Scaridae) associated with drifting algae were studied. In this study, 628 L. vaigiensis of various developmental stages ranging from postflexion larvae (9.4mm in standard length, SL) to adults (192.0mmSL) were sampled from drifting algae at two fishing ports in Nakagusuku Bay of Okinawa Island. In 3969 fish comprising 65 taxa in 34 families of Teleostei collected with drifting algae, L. vaigiensis occupied 15.8% of samples and occurred generally throughout the whole year. A large number of L. vaigiensis were collected from July to October accompanied by an occurrence of drifting algae composed of Sargassum spp. Larvae and early juveniles ranging from 11.1 to 14.9mmSL appeared sporadically throughout the year, and postflexion larvae 11mmSL occurred from July to November. Their food shifted from planktonic copepods in postflexion larvae and juveniles ranging from 10.0 to 14.9mmSL to seaweed in the juveniles ranging from 15.0 to 24.9mmSL. Furthermore, adults and young over 25mmSL fed almost exclusively on seaweed, with Sargassum spp. constituting the drifting algae. These facts indicate that drifting algae may have a role concerning food and habitat, and may act as a nursery for L. vaigiensis.  相似文献   

5.
Cultures of Trichodesmium from the Northern and Southern Great Barrier Reef Lagoon (GBRL) have been established in enriched seawater and artificial seawater media. Some cultures have been maintained with active growth for over 6years. Actively growing cultures in an artificial seawater medium containing organic phosphorus (glycerophosphate) as the principal source of phosphorus have also been established. Key factors that contributed to the successful establishment of cultures were firstly, the seed samples were collected from depth, secondly, samples were thoroughly washed and thirdly, incubations were conducted under relatively low light intensities (PAR 40–50molquantam–2s–1). N2 fixation rates of the cultured Trichodesmium were found to be similar to those measured in the GBRL. Specific growth rates of the cultures during the exponential growth phase in all enriched media were in the range 0.2–0.3day–1 and growth during this phase was characterised by individual trichomes (filaments) or small aggregations of two to three trichomes. Characteristic bundle formation tended to occur following the exponential growth phase, which suggests that the bundle formation was induced by a lack of a necessary nutrient e.g. Fe. Results from some exploratory studies showed that filament-dominated cultures of Trichodesmium grew over a range of relatively low irradiances (PAR 5–120molquantam–2s–1) with the maximum growth occurring at 40–50molquantam–2s–1. These results suggest that filaments of the tested strain are well adapted for growth at depth in marine waters. Other studies showed that growth yields were dependent on salinity, with maximum growth occurring between 30 and 37psu. Also the cell yields decreased by an order of magnitude with the reduction of Fe additions from 450 to 45nM. No active growth was observed with the 4.5nM Fe addition.  相似文献   

6.
Tissue-cultured plantlets of three sugarcane (Saccharum spp.) cultivars having a known field smut reaction were screened for susceptibility to Ustilago scitaminea H&P Sydow. Plantlets were inoculated with 0.5 l of a suspension of equally mixed quantities of plus and minus mating type sporidia of U. scitaminea at concentrations ranging from 1×101 to 1×106 cells. Fungal sori (whips) were produced in cultivar N12 (intermediate) 6weeks following inoculation with 1×105 mixed sporidia and thereafter in cultivar NCo310 (susceptible) but not in cultivar N19 (resistant). Sori bearing teliospores were produced up to 3months following inoculation and incubation at 26°C. No sori were produced at mixed sporidial concentrations lower than 1×105cells. The in vitro soral production in cultivars N19, N12 and NCo310 was 0, 27.5 and 47.5% respectively. Plantlets inoculated with 1×105sporidia of only one mating-type did not produce sori in any of the three cultivars tested. Blind scoring of an unknown sugarcane cultivar by this method corresponded exactly with its field smut rating.  相似文献   

7.
Petitpierre E  Garnería I 《Genetica》2003,119(2):193-199
The chromosomes of ten species of Cyrtonus and the genome sizes of six are surveyed. Among the total of 15 chromosomally studied species, 11 have 2n=28 chromosomes and a 13+Xyp male meioformula, three have 2n=40 and 19+Xyp and one 2n=46 and 22+Xyp. All but one species with 28 chromosomes show only metacentric or submetacentric chromosomes, whereas the species with 40 and 46 chromosomes display some telocentrics or subtelocentrics, that are probably derived from the former by centric fissions. However, since the number of major chromosome arms is strikingly higher in these latter species (NF=70 and 78) than in the 28-chromosome species (mostly NF=56), other chromosomal rearrangements such as pericentric inversions or heterochromatin accretions could also be involved. The genome sizes display a narrow range, from 1C=0.6–1.22pg, and they are not significantly correlated with the chromosome numbers. Some possible factors implied in the rough chromosomal evolution of Cyrtonus are discussed in relation to a few other genera of the subfamily Chrysomelinae.  相似文献   

8.
Competitive interactions were compared under field and greenhouse conditions for three representative tallgrass prairie species, Echinacea purpurea, Panicum virgatum and Ratibida pinnata. These were planted in monoculture and in mixtures of two species using a replacement series design with groups of four or eight plants. Competition was determined from shoot dry weight data collected during 120days in the greenhouse and after 415days in the field. Yields declined with increased density of a single species in the greenhouse from 40days onward and in the field. Relative yields were up to 100% higher in mixtures than in monocultures for all species early on in the greenhouse experiment. Later in the experiment and in the field relative yields of E.purpurea decreased in the presence of P.virgatum and R.pinnata, whereas relative yields of these two species increased in the presence of E.purpurea. There were correlations in relative yield between the field and the greenhouse experiment at 80 and 120days. In the greenhouse P.virgatum maintained higher net assimilation rates than the other species. Relative growth rates of all species were higher in monoculture and in mixtures up to 40days, after which they declined, especially for E.purpurea in mixtures. In the field, higher light intensities occurred in pure stands of E.purpurea than in mixed stands with other species. The order of competitive ability that was apparent from these field and greenhouse studies, P.virgatum=R.pinnata>E.purpurea, could be partially explained by photosynthetic rates in relation to canopy light interception.  相似文献   

9.
We used ultrasonic telemetry to examine movement patterns of 11 bat rays, Myliobatis californica, in Tomales Bay, California. Tomales Bay is long (20km) and narrow (1.4km), and is hydrographically separated into outer and inner bay regions. The outer bay (the outermost 8km) is characterized by oceanic conditions while the shallow inner bay (the innermost 12km) features wide seasonal temperature shifts. Five rays were tracked monthly from October 1990 to November 1991 and six rays (four of which carried temperature-sensing transmitters) were tracked daily from 30 June to 16 July 1992. Mean bat ray movement rate was 8.84mmin–1 (range 4.49 to 13.40mmin–1) and was not significantly affected by size (p=0.592), tidal stage (p=0.610), or time of day (p=0.327). Movement direction was unrelated to tidal stage (p=0.472) but showed a highly significant diel pattern (p<0.001). From 2:50–14:50h, rays moved toward the warmer and shallower inner bay, while from 14:50–2:50h they moved toward the cooler and deeper outer bay. These telemetry data, along with known bat ray foraging patterns and respiratory temperature-sensitivity, argue for behavioral thermoregulation as the primary influence on this movement pattern.  相似文献   

10.
Temperature dependencies were established for the egg-to-mummy and mummy-to-adult phases, for mummy mortality, and for parasitism of Aphidius ervi Haliday, Aphidius rhopalosiphi De Stefani-Perez, and Praon volucre (Haliday) (Hymenoptera, Aphidiidae), three parasitoids of Sitobion avenae (Fabricius) (Homoptera, Aphididae), at 8°C, 12°C, 16°C, 20°C, and 25°C on winter wheat (cv. Haven). A physiological model described temperature-dependent development over the full temperature range, whereas a linear model was fitted for data above 8°C and used to estimate the lower temperature thresholds and day-degrees (° D) required for development. The thresholds for A. ervi were 2.2°C for egg-mummy development and 6.6°C for mummy-adult development, those for A. rhopalosiphi were 4.5°C and 7.2°C, and those for P. volucre were 3.8°C and 5.5°C. The time to develop into mummies and adults differed significantly between the three species: A. ervi development into mummies required an average of 159 ° D, while development into adults took an average of 73 ° D. The corresponding average times required for A. rhopalosiphi and P. volucre to develop mummies were 124° D and 126° D, while their development into adults required an average of 70° D and 150° D, respectively. Mummy mortality was 25–35% at 8°C and less at the higher temperatures tested, but began to increase again at 25°C, showing a quadratic relationship between mortality and temperature. Parasitization was very low or, in the case of P. volucre, absent up to 12°C and thereafter increased with increasing temperature. The relationship between parasitization, recorded as percent aphids mummified, and temperature was linear at the temperatures tested and depended on species. A. ervisuperparasitized 11.1% aphids at 20°C and 16.6% aphids at 25°C, whereas superparasitism was low in A. rhopalosiphi and absent in P. volucre. From 16°C to 25°C the P. volucre sex ratio increased. For A. ervi and A. rhopalosiphi there was no trend with temperature, but at 20°C and 25°C it was close to even. Field data for 1996 and 1997 allowed for a comparison of actual and expected emergence of overwintering mummies. In both years, parasitoids were predicted to have emerged from overwintering mummies well in advance of the onset of aphid infestation, and more than a month earlier than the first parasitized aphids were found in winter wheat. Observations from trap plants in other crops supported the predictions of the models. Other factors that can affect biological control by cereal aphid parasitoids are discussed.  相似文献   

11.
Euphorbia characias is a Mediterranean spurge with a diplochorous dispersal system: after a ballistic dispersal that scatters the seeds, some ant species find and retrieve the seeds to their nest (myrmecochorous dispersal). The seed dispersal curve generated by ants in an abandoned field was described and partitioned according to ant size and to the distance to nest entrance from where seeds fell after ballistic dispersal. Both variables (ant size, distance to nest) affected dispersal distance. The seed dispersal curve showed a peak at short distance (median=1m) and a tail extending to 9.4m. The peak and the tail are explained differently. Short distances are usually generated by small ants (Pheidole pallidula and Tapinoma nigerrimum; 0.56±0.41m [n=48]) both from the nearest or farther nest entrances. The tail of the curve is generated disproportionately by big ants (Aphaenogaster senilis and Messor barbarus; 2.09±1.71m [n=61]) from farther nests. Seeds have a much greater probability (P=0.734) of being transported to nests which are not the nearest. This effect is largely due to transportation by big ants.  相似文献   

12.
The mangrove killifish Rivulus marmoratus was reared at 25°±1°C and 17ppt salinity from 0 to 100 days after hatching (DAH), and its early development was described by examining growth and morphometric parameters, meristic characters (vertebral and fin-ray counts), bone-cartilage development, and pigmentation. Growth was isometric for preanal length, head length, snout length, body depth, pectoral-fin length, dorsal-fin length, anal-fin length, and caudal-peduncle depth. Negative allometric growth was observed in eye diameter and gape size. Meristic counts (mean±SD) for vertebrae (34.2±0.4) and dorsal- (8.6±0.5), anal- (11.4±0.5), and caudal-fin rays (30.2±0.8) were complete at 0 DAH (n=5), whereas pectoral-fin rays and pelvic-fin rays were complete by 30 DAH (14.5±0.4, n=5) and 60 DAH (4.2±0.8, n=5). Full ossification of meristic elements proceeded in the following sequence: vertebrae (by 30 DAH), caudal-, dorsal-, and anal-fin rays (by 60 DAH), pectoral-fin rays (between 60 DAH and 100 DAH), and pelvic-fin rays (by 100 DAH). Both morphological characters and meristic counts indicate that this species can be considered to be a juvenile after 9.8mm in standard length (20 DAH).  相似文献   

13.
The spatial genetic structure was assessed by amplified fragment length polymorphism (AFLP) technique for Quercus crispula Blume (37 individuals) and Q.dentata Thunberg (54 individuals) growing along a 550-m transect in Ishikari, Hokkaido, northern Japan. The simple Mantel test revealed significant negative correlation between genetic similarity and geographic distance in Q.dentata and negative but insignificant correlation in Q.crispula. Spatial autocorrelation analysis revealed that Mantels r generally decreased from positive to negative values with the increase of spatial distance in both oak species with significant deviation from zero for the 50–100-m (positive) and 250–300-m classes (negative) in Q.dentata. Thus, significant spatial genetic structure was revealed at least in Q.dentata  相似文献   

14.
Uptake kinetics of nitrogen derived from sewage–seawater mixtures (2.5–20% v/v effluent) were determined in the laboratory for Ulva rigida (Chlorophyceae) native from Bahía Nueva (Golfo Nuevo, Patagonia, Argentine). In terms of nitrogen concentration, experimental enrichment levels varied between 53.7 and 362.3M of ammonium and between 0.77 and 6.21M of nitrate+nitrite. Uptake rates were fitted to the Michaelis–Menten equation, with the following kinetic parameters: ammonium: Vmax = 591.2molg–1h–1, K s=262.3M, nitrate+nitrite: V max=12.9molg–1h–1, K s=3.5M). Both nutrients were taken up simultaneously, but ammonium incorporation was faster in all cases. The results show a high capability of Ulva rigida to remove sewage-derived nitrogen from culture media. In the field, most of the nitrogen provided by the effluent would be tied up in algal biomass, supporting low nitrogen levels found at a short distance away from the source.  相似文献   

15.
In order to conserve the horseshoe crab, Tachypleus tridentatus, a famous living fossil in Kinmen and Taiwan, several investigations related to its basic biology were conducted, and public education/participation programs were implemented. Biological investigations included artificially inducing spawning in the laboratory and field, rearing of juveniles, monitoring of habitat characteristics, and establishing a protected area. The grain size of the sediment of the spawning ground was 0.4–1.8mm in diameter and that of the juvenile nursing ground was 0.11–0.19mm. The most suitable water temperature for incubating eggs and rearing juveniles ranged from 28 to 31°C. A total of 800ha of the coastal zone on Kinmen was designated a protected area for the horseshoe crab, based on the Fishery Law, in December 1999. Fishing is prohibited for the 5-year period from 2000 to 2004. Public education programs were conducted to help local people learn about the basic biology of the horseshoe crab, to become aware of its importance and the necessity for conservation, and to empower them to actively participate in the conservation of this species. In addition, a horseshoe crab conservation program has also been incorporated as an element of the local ecotourism industry. Biotechnology business opportunities that may be created as a result of viable horseshoe crab populations will also be promoted.  相似文献   

16.
The early life history and development of the scopelarchid Benthalbella linguidens was studied, based on 203 specimens (from 5.3 to 89.7mm in body length: BL) collected from Kuroshio, Oyashio waters and transition waters of the western North Pacific. The early life stages of B. linguidens are distinguished from those of other species of Benthalbella that inhabit the North Pacific by the characters of 62–64 myomeres in the larval stage and 26–28 anal fin rays in juvenile and transforming specimen. Larvae are elongate; notochord flexion begins at ca. 12mm BL and is completed at ca. 15mm BL. The fin ray complements are established at ca. 40mm BL. The single transforming specimen (89.7mm BL) that has peritoneal pigment was collected from transition waters. All larvae were collected from Kuroshio and transition waters from winter to early summer; however, the size of larvae in Kuroshio waters was apparently smaller than that in transition waters, with ranges of 5.3–32.4mm BL (mean 17.1) and 15.3–35.3mm BL (mean 27.5), respectively. Juveniles were distributed in transition and Oyashio waters and were absent in Kuroshio waters, where adults are commonly distributed. These occurrences of larvae and juveniles in the western North Pacific indicate that B. linguidens spawns in Kuroshio waters in winter and uses transition waters as nursery grounds.  相似文献   

17.
Cryopreservation of callus tissue of Artimisia annua L. was optimized. Two lines of calli were precultured on MS medium with 5% (v/v) dimethyl sulfoxide, and protected by a cryoprotectant containing 15% (v/v) ethylene glycol, 15% (v/v) dimethyl sulfoxide, 30% (v/v) glycerol and 13.6% (w/v) sucrose. The highest survival rate of callus A201 reached 87% after it was pretreated at 25°C, cryopreserved by liquid nitrogen, recovered in water bath at 25°C and reloaded at 25°C with 34% (w/v) sucrose solution, and that of callus A202 reached 78% after it was treated as callus A201, except pretreated at 35°C, recovered at 35°C and reloaded with 47.8% (w/v) sucrose solution.  相似文献   

18.
The milk-clotting and proteolytic activities of extracellular enzyme preparations from Nocardiopsis sp. were investigated under different culture conditions. A soybean flour medium was used, with concentrations of soybean flour and of glucose varying from 0.25 to 1% w/v and from 0 to 1% w/v, respectively. Growth was monitored with 2ml samples withdrawn from the culture medium at 8-h intervals, for determination of total protein, proteolytic activity, milk-clotting activity and sugar reduction. The best milk-clotting protease production, with a specific activity of 24.49U/mg at 40h, was obtained in the glucose-free medium containing soybean flour 1% w/v.  相似文献   

19.
The spatial distributions of canopy and subcanopy species (50cm stem length) were investigated within a plot extending from the top of a ridge to the valley bottom in a cool-temperate old-growth mixed forest, dominated by Cryptomeria japonica and Fagus crenata, in the snowy region of Japan. Based on the longitudinal profile of the slope, the study slope was divided into the relatively gentle upper slope position (US), the steep lower slope position (LS), the flat valley bottom (VB) and the boundary zone between the upper and lower slopes (BS). Spatial dispersal and the association patterns of species were analyzed in upperstory (10cm d.b.h) and understory (<10cm d.b.h) layers. Dominant species in the upperstory layer abruptly changed from Cryptomeria to Fagus at the BS site. In contrast, the understory trees of many species, including shade-intolerant and evergreen species, were independent of the location of conspecific upperstory trees or canopy gaps and extended their distributions on and around the BS site. Significant, diverse canopy and subcanopy species occurred at this site in both upperstory and understory layers. On the BS site, which is the lower margin of Cryptomeria-dominated vegetation, there were many medium-sized C.japonica that were killed by uprooting or breaking of the stems as a result of heavy snow pressure. It is suggested that the snow pressure gradient along a slope has a strong influence on community structure and the maintenance of diverse canopy and subcanopy species in this snowy mixed forest.  相似文献   

20.
Six specimens (2 flexion larvae: 9.5–10.4mm in notochord length; 4 postflexion larvae: 12.3–18.2mm in standard length) collected from the western North Pacific are tentatively ascribed to the genus Uncisudis of the tribe Lestidiini of the subfamily Paralepidinae (Paralepididae) in sharing remarkably elongate and filamentous pelvic fin rays, their tips reaching the origin of the anal fin. They are described as Uncisudis posteropelvis sp. nov. in uniquely having the insertion of pelvic fins closer to the origin of anal fin than to the posterior end of dorsal fin base among lestidiine species. Addition to this character, the new species has remarkably elongate and filamentous dorsal fin rays, the short distance between anus and origin of anal fin (4.2–6.1% of standard length, SL), the posteriorly located pelvic fins (prepelvic length 69.4–71.5% SL), dorsal fin rays 10, anal fin rays 28–29, myomeres 41–42+38–40=80–81 (vertebrae 38+41=79), and peritoneal pigment spots 11–12. The occurrence of larvae differing in pigment pattern from the present new species suggests another undescribed species of Uncisudis in the western South Pacific.  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