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1.
Rebecca J. Waggett Edward J. Buskey 《Journal of experimental marine biology and ecology》2008,361(2):111-118
Calanoid copepods from seven families in three superfamilies were exposed to a controlled near-field hydrodynamic stimulus and their escape reactions were recorded using high-speed videographic techniques. Copepod species have two distinct mechanisms for increasing conduction speed of neural signals: larger diameter nerve axons and insulated axons, i.e., myelination. Myelinated axons have been found in certain species of the more recently-evolved calanoid superfamilies. Copepod representatives from these superfamilies were expected to have shorter response latencies than species from more ancestral superfamilies due to the increased conduction speed of nerve impulses in myelinated neurons. Using frame-by-frame playback and computerized motion analysis techniques, response latency, jump speed, and acceleration were measured. Kinetic performance of copepods was highly variable, with mean escape speeds ranging between 100-250 mm s− 1 and accelerations of 9-230 m s− 2. Minimum behavioral response latencies of 2 ms were recorded for both myelinated and non-myelinated calanoids. There was no significant difference between the response latencies of copepods from the myelinated and non-myelinated superfamilies. Furthermore, no relationships were found between copepod latency and size for either myelinated or non-myelinated species. Previous research may suggest that myelin may shorten the response latencies of certain calanoid species. However, our results show that non-myelinated copepods are also capable of responding rapidly, within as few as 2 ms, to hydrodynamic stimuli and produce similar kinetic performance to myelinated species. The main advantage of myelination over giant nerve axons is their more efficient transfer of nerve impulses resulting in a metabolic energy savings. Although this energetic reward would be important for copepods in food-limited environments, for coastal copepods, in food-rich habitats, either mechanism is a viable solution. 相似文献
2.
The escape behavior of marine copepods in response to a quantifiable fluid mechanical disturbance 总被引:1,自引:0,他引:1
The threshold shear values needed to elicit the escape reactionto a quantifiable fluid mechanical disturbance were comparedbetween five free-swimming oceanic copepod species. The resultsindicate a significant difference in the threshold for differentspecies of copepods and between different age groups withina single species. In general, animals captured from more energeticregimes required a higher threshold than those captured frommore pacific locations. Labidocera madurae required the highestshear values with 51.5 s1 for 50% of the animals testedto elicit an escape reaction (S50). Acartia tonsa and Euchaetarimana, in contrast, were behaviorally the most sensitive requiringan S50 of only 1.5 and 4.1 s1, respectively, to initiatean escape reaction. Pleuromamma xiphias and Oithona requiredintermediate shear values with an S50 of 7.2 and 8.1 s1.When compared to literature values, the threshold needed toelicit an escape reaction was consistently higher than averageenvironmental shear values. Threshold shear values also variedsignificantly with developmental stage. Naupliar stages of A.tonsarequired greater than six times the S50 value required by adultsof the same species. This suggests that the higher vulnerabilityto predation of naupliar stages of copepods may not only reflectinferior escape strength, but may also result from the higherthreshold needed to elicit an escape reaction. This study supportsthe hypothesis that selective feeding patterns exhibited bypredators of copepods may be the result of the differentialbehavioral sensitivities of different species and developmentalstages of copepods. 相似文献
3.
Habitat choice in relation to environmental factors of two coexisting calanoid copepod species, Eudiaptomus gracilis and E. graciloides, was studied in a mesotrophic lake and in large indoor mesocosms. Both species and sexes showed pronounced diel vertical
migration (DVM) in the field. In 12 m deep mesocosms with free ranging fish DVM was observed and species increased day depth
over time. No changes were observed in copepod day depth over time in experiments with fish kairomone. It is hypothesized
that fish kairomone acts as an early warning system to copepods which respond by moving deeper, but only as far as the thermocline.
For full DVM, a nearby mechanical stimulus is necessary. Thus, as fish go deeper to feed, copepods retreat. The response of
copepods to fish predation, in the presence of low and high numbers of Daphnia,shows that copepods effectively use Daphniaas living shields to avoid predation. The two species adopt different vertical migration strategies depending on whether there
are high or low numbers of Daphniapresent. A dominant feature of mesocosm experiments was the night time aggregating (lekking) of E. gracilis males at the surface. When the spring and autumn percentages of risk takers in the epilimnion were compared, E. gracilis, particularly males, suffered the greatest cost. 相似文献
4.
Brad J. Gemmell Houshuo Jiang Edward J. Buskey 《Proceedings. Biological sciences / The Royal Society》2015,282(1812)
Ciliates can form an important link between the microbial loop and higher trophic levels primarily through consumption by copepods. This high predation pressure has resulted in a number of ciliate species developing rapid escape swimming behaviour. Several species of these escaping ciliates also possess a long contractile tail for which the functionality remains unresolved. We use high-speed video, specialized optics and novel fluid visualization tools to evaluate the role of this contractile appendage in two free-swimming ciliates, Pseudotontonia sp. and Tontonia sp., and compare the performance to escape swimming behaviour of a non-tailed species, Strobilidium sp. Here, we show that ‘tailed’ species respond to hydrodynamic disturbances with extremely short response latencies (less than or equal to 0.89 ms) by rapidly contracting the tail which carries the cell body 2–4 cell diameters within a few milliseconds. This provides an advantage over non-tailed species during the critical first 10–30 ms of an escape. Two small, short-lived vortex rings are created during contraction of the tail. The flow imposed by the ciliate jumping can be described as two well-separated impulsive Stokeslets and the overall flow attenuates spatially as r−3. The high initial velocities and spatio-temporal arrangement of vortices created by tail contractions appear to provide a means for rapid escape as well as hydrodynamic ‘camouflage’ against fast striking, mechanoreceptive predators such as copepods. 相似文献
5.
The polyamine spermidine is an essential biosynthetic precursor of pyrrolizidine alkaloids. It provides its aminobutyl group
which is transferred to putrescine yielding homospermidine, the specific building block of the necine base moiety of pyrrolizidine
alkaloids. The enzymatic formation of spermidine was studied in relation to the unique role of this polyamine as an alkaloid
precursor. S-adenosylmethionine decarboxylase (SAMDC, EC 4.1.1.50) and spermidine synthase (SPDS, EC 2.5.1.16) from root cultures of Senecio vulgaris were partially purified and characterized. The SAMDC-catalyzed reaction showed a pH optimum of 7.5, that of SPDS an optimum
of 7.7. The K
m value of SAMDC for its substrate S-adenosylmethionine (SAM) was 15 μM, while the apparent K
m values of SPDS for its substrates decarboxylated SAM (dSAM) and putrescine were 4 μM and 21 μM, respectively. The relative
molecular masses of the two enzymes, determined by gel filtration, were 29 000 (SAMDC) and 37 000 (SPDS). Studies with various
potential inhibitors revealed, for most inhibitors, profiles that were similar to those established with the respective enzymes
from other plant sources. However, putrescine which is not known to be an inhibitor of plant SAMDC, strongly inhibited the
enzyme from S. vulgaris roots. Spermidine synthase was sensitive to inhibition by its product spermidine. In the presence of the stationary tissue
concentrations of the two polyamines (ca. 0.1 mM each) the activities of SAMDC and SPDS would be inhibited by >80%. The results
are discussed in relation to the role of spermidine in primary and secondary metabolism of alkaloid-producing S. vulgaris root cultures.
Received: 15 September 1999 / Accepted 10 December 1999 相似文献
6.
Trophodynamics and predation impact of the 2 dominant chaetognaths Eukrohnia hamata and Sagitta gazellae were investigated at 19 stations in the vicinity of the Prince Edward Islands and at a 24-h station occupied at the sub-Antarctic
Front in late summer (April/May) 1996. During the entire investigation, the zooplankton assemblages were numerically dominated
by copepods with densities ranging from 21 to 170 ind. m−3. Amongst the copepods, Clausocalanus brevipes, Metridia gerlachei and M. lucens dominated accounting for >90% of the total. Generally, chaetognaths were identified as the second most important group composing
at times up to 30% (mean = 14.7%) of total zooplankton abundance. Of the two chaetognath species, E.␣hamata was generally numerically dominant. Gut content analysis showed that both chaetognath species are opportunistic predators
generally feeding on the most abundant prey, copepods. No feeding patterns were evident during the 24-h station, suggesting
that both species feed continuously. The feeding rates of E. hamata ranged from 0 to 0.50 prey ind. day−1 and between 0 and 0.90 prey ind. day−1 for S. gazellae. The maximum total predation impact of E. hamata was equivalent to 5.2% of the copepod standing stock or up to 103% of copepod production per day. For S. gazellae the predation impact was lower, reaching a level of 3.2% of the copepod standing stock or 63% of the daily copepod production.
Chaetognaths can, therefore, be regarded as an important pelagic predator of the Prince Edward Islands subsystem.
Received: 27 March 1997 / Accepted: 11 September 1997 相似文献
7.
Species and material considerations in the formation and development of microalgal biofilms 总被引:2,自引:0,他引:2
The development of microalgal biofilms has received very limited study despite its relevance in the design of photobioreactors
where film growth may be advantageous for biomass separation or disadvantageous in fouling surfaces. Here, the effects of
species selection, species control, and substrate properties on biofilms of Scenedesmus obliquus and Chlorella vulgaris were investigated. Experiments were conducted in batch culture and in continuous culture modes in a flow cell. Cell growth
was monitored using confocal laser scanning microscopy and gravimetrically. Species selection and species control had significant
effects on biofilm development. On non-sterile wastewater, C. vulgaris shifted from primarily planktonic (23.7% attachment) to primarily sessile (79.8% attachment) growth. The biofilms that developed
in non-sterile conditions were thicker (52 ± 19 μm) than those grown in sterile conditions (7 ± 6 μm). By contrast, S. obliquus attained similar thicknesses (54 ± 31 and 53 ± 38 μm) in both sterile and non-sterile conditions. Neither species was able
to dominate a non-sterile biofilm. The effect of substrate surface properties was minimal. Both species grew films of similar
thickness (∼30 μm for S. obliquus, <10 μm for C. vulgaris) on materials ranging from hydrophilic (glass) to hydrophobic (polytetrafluoroethylene). Surface roughness created by micropatterning
the surface with 10 μm grooves did not translate into long-term increases in biofilm thickness. The results indicate that
species selection and control are more important than surface properties in the development of microalgal biofilms. 相似文献
8.
In many cases the distribution of saccadic reaction times (SRT) deviates considerably from a unimodal distribution and may
often exhibit several peaks. We present a statistical approach to determining the number and form of the individual peaks.
The overall density of the reaction times f
i
(t), i=1…M obtained in M different experiments with the same subject is described as the sum of K basis functions x
k
(t),k=1…K with different weights and an error term. A change in the experimental conditions is assumed to cause a change in the weights,
not in the basis functions. We minimize the square of the difference (measured data minus approximation), divided by the error
of the data. Incrementing K step by step we determine the necessary number of basis functions. This method is applied to data of six subjects tested
in different saccade tasks. We detect five different modes: two in the range 80–140 ms (express modes), two in the range 145–190 ms
(fast-regular mode) and one at about 230 ms (slow-regular mode). These modes are located at about the same positions for different
subjects. The method presented here not only proves statistically the existence of several modes in SRT distributions but
also allows the distributions to be described by a few characteristic numbers that go beyond the mean values and standard
deviations.
Received: 24 March 1997 / Accepted: 5 December 1997 相似文献
9.
Real-time polymerase chain reaction (PCR) is considered a highly sensitive method for the quantification of microbial organisms
in environmental samples. This study was conducted to evaluate real-time PCR with SybrGreen detection as a quantification
method for sulfate-reducing bacteria (SRB) in industrial wastewater produced by several chemical industries. We designed four
sets of primers and developed standard curves based on genomic DNA of Desulfovibrio vulgaris from pure culture and on plasmids containing dissimilatory sulfate reductase (dsrA) or adenosine-5′-phosphosulfate reductase (apsA) genes of SRB. All the standard curves, two for dsrA and two for apsA genes, had a linear range between 0.95 × 102 and 9.5 × 106 copies/μL and between 1.2 × 103 and 1.2 × 107 copies/μL, respectively. The theoretical copy numbers of the tenfold dilutions of D. vulgaris genomic DNA were best estimated (between 2.7 to 10.5 times higher than theoretical numbers) by the standard curve with DSR1F
and RH3-dsr-R primers. To mimic the effect of foreign DNA in environmental samples, serial dilutions of D. vulgaris genomic DNA were mixed with Escherichia coli chromosomal DNA (40 ng per assay). This influenced neither PCR amplification nor the quantification of target DNA. Industrial
wastewater was sampled during a 15-month period and analyzed for the presence of SRB, based on dsrA gene amplification. SRB displayed a higher abundance during the summer (about 107–108 targets mL−1) and lower during the winter (about 104–105 targets mL−1). The results indicate that our real-time PCR approach can be used for detection of uncultured SRB and will provide valuable
information related to the abundance of SRB in durable environmental samples, such as complex and saline industrial wastewaters. 相似文献
10.
Photosynthetic pathway and ontogeny affect water relations and the impact of CO2 on Bouteloua gracilis (C4) and Pascopyrum smithii (C3) 总被引:2,自引:0,他引:2
The eastern Colorado shortgrass steppe is dominated by the C4 grass, Bouteloua gracilis, but contains a mixture of C3 grasses as well, including Pascopyrum smithii. Although the ecology of this region has been extensively studied, there is little information on how increasing atmospheric
CO2 will affect it. This growth chamber study investigated gas exchange, water relations, growth, and biomass and carbohydrate
partitioning in B. gracilis and P. smithii grown under present ambient and elevated CO2 concentrations of 350 μl l−1and 700 μl l−1, respectively, and two deficit irrigation regimes. The experiment was conducted in soil-packed columns planted to either
species over a 2-month period under summer-like conditions and with no fertilizer additions. Our objective was to better understand
how these species and the functional groups they represent will respond in future CO2-enriched environments. Leaf CO2 assimilation (A
n), transpiration use efficiency (TUE, or A
n/transpiration), plant growth, and whole-plant water use efficiency (WUE, or plant biomass production/water evapotranspired)
of both species were greater at elevated CO2, although responses were more pronounced for P. smithii. Elevated CO2 enhanced photosynthesis, TUE, and growth in both species through higher soil water content (SWC) and leaf water potentials
(Ψ) and stimulation of photosynthesis. Consumptive water use was greater and TUE less for P. smithii than B. gracilis during early growth when soil water was more available. Declining SWC with time was associated with a steadily increased
sequestering of total non-structural carbohydrates (TNCs), storage carbohydrates (primarily fructans for P. smithii) and biomass in belowground organs of P. smithii, but not B. gracilis. The root:shoot ratio of P. smithii also increased at elevated CO2, while the root:shoot ratio of B. gracilis was unresponsive to CO2. These partitioning responses may be the consequence of different ontogenetic strategies of a cool-season and warm-season
grass entering a warm, dry summer period; the cool-season P. smithii responds by sequestering TNCs belowground in preparation for summer dormancy, while resource partitioning of the warm-season
B. gracilis remains unaltered. One consequence of greater partitioning of resources into P. smithii belowground organs in the present study was maintenance of higher Ψ and A
n rates. This, along with differences in photosynthetic pathway, may have accounted for the greater responsiveness of P. smithii to CO2 enrichment compared to B. gracilis.
Received: 21 July 1997 / Accepted: 16 December 1997 相似文献
11.
Mannan Hajimahmoodi Mohammad Ali Faramarzi Najmeh Mohammadi Neda Soltani Mohammad Reza Oveisi Nastaran Nafissi-Varcheh 《Journal of applied phycology》2010,22(1):43-50
Antioxidant activities of both cells and extracellular substances were evaluated in 12 soil-isolated strains of microalgae
according to FRAP and DPPH-HPLC assays. Their total phenolic contents were also determined by Folin–Ciocalteu method. Extractions
were performed with hexane, ethyl acetate, and water. The results of FRAP assay showed that algal cells contained considerable
amounts of antioxidants from 0.56 ± 0.06 to 31.06 ± 4.00 μmol Trolox g−1 for Microchaete tenera hexane extract and Chlorella vulgaris water extract, respectively. In water fractions of extracellular substances, the antioxidants were from 1.30 ± 0.15 μmol
Trolox g−1 for Fischerella musicola to 73.20 ± 0.16 μmol Trolox g−1 for Fischerella ambigua. Also, DPPH-HPLC assay represented high antioxidant potential of water fractions. The measured radical-scavenging activities
of the studied microalgae were at least 0.15 ± 0.02 in Nostoc ellipsosporum cell mass to a maximum of 109.02 ± 8.25 in C. vulgaris extracellular substance. The amount of total phenolic contents varied in different strains of microalgae and ranged from
zero in hexane extract to 19.15 ± 0.04 mg GAE g−1 in C. vulgaris extracellular water fraction. Significant correlation coefficients between two measured parameters indicated that phenolic
compounds were a major contributor to the microalgal antioxidant capacities. 相似文献
12.
H. Adelsberger J. Dudel 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1996,180(1):53-61
Whereas the inhibitory innervation of the deep extensor abdominal muscle in crayfish is mediated by a weakly acting common
inhibitor, the opener muscle exhibits a stronger inhibition. In the present study the most abundant γ-aminobutyric acid-activated
chloride channel on distal fibers of crayfish opener muscle was characterized by measuring the current responses after applying
pulses of γ-aminobutyric acid to outside-out patches. The results were compared to those obtained earlier with the chloride
channel on the deep extensor abdominal muscle of the same species. The double logarithmic plot of the dose-response relationship
had a slope of n
H = 2.2 in contrast to n
H = 5.3 for the channel on the deep extensor abdominal muscle. The rise time of the current response declined to 1 ms at a
γ-aminobutyric acid concentration of 50 mmol · l−1. With lower concentrations the rise time increased to a maximal value of 280 ms. No peak of the rise time at low γ-aminobutyric
acid concentrations, as observed for the channel on the deep extensor abdominal muscle, was obvious. The open and closed times
were similar to those of the channel of the deep extensor abdominal muscle. Different reaction schemes were discussed to describe
the kinetics of the chloride channel of the opener muscle.
Accepted: 12 August 1996 相似文献
13.
Localization of ion-regulatory epithelia in embryos and hatchlings of two cephalopods 总被引:1,自引:0,他引:1
Marian Y. Hu Elliott Sucré Mireille Charmantier-Daures Guy Charmantier Magnus Lucassen Nina Himmerkus Frank Melzner 《Cell and tissue research》2010,339(3):571-583
The tissue distribution and ontogeny of Na+/K+-ATPase has been examined as an indicator for ion-regulatory epithelia in whole animal sections of embryos and hatchlings
of two cephalopod species: the squid Loligo vulgaris and the cuttlefish Sepia officinalis. This is the first report of the immunohistochemical localization of cephalopod Na+/K+-ATPase with the polyclonal antibody α (H-300) raised against the human α1-subunit of Na+/K+-ATPase. Na+/K+-ATPase immunoreactivity was observed in several tissues (gills, pancreatic appendages, nerves), exclusively located in baso-lateral
membranes lining blood sinuses. Furthermore, large single cells in the gill of adult L. vulgaris specimens closely resembled Na+/K+-ATPase-rich cells described in fish. Immunohistochemical observations indicated that the amount and distribution of Na+/K+-ATPase in late cuttlefish embryos was similar to that found in juvenile and adult stages. The ion-regulatory epithelia (e.g.,
gills, excretory organs) of the squid embryos and paralarvae exhibited less differentiation than adults. Na+/K+-ATPase activities for whole animals were higher in hatchlings of S. officinalis (157.0 ± 32.4 μmol gFM−1 h−1) than in those of L. vulgaris (31.8 ± 3.3 μmol gFM−1 h−1). S. officinalis gills and pancreatic appendages achieved activities of 94.8 ± 18.5 and 421.8 ± 102.3 μmolATP gFM−1 h−1, respectively. High concentrations of Na+/K+-ATPase in late cephalopod embryos might be important in coping with the challenging abiotic conditions (low pH, high pCO2) that these organisms encounter inside their eggs. Our results also suggest a higher sensitivity of squid vs. cuttlefish
embryos to environmental acid-base disturbances. 相似文献
14.
Little is known about the biology and feeding ecology of Arctogadus glacialis (Peters, 1874), an endemic gadid fish species occurring circumpolarly in both ice-free and ice-covered Arctic seas. In this
study we analysed specimens sampled from bottom trawl and Agassiz trawl catches conducted at eight stations in water depths
from 115 to 490 m in the Northeast Water Polynya off Greenland in August 1990. Size composition and sex ratios were assessed
for 585 fish with standard lengths ranging from 7.8 to 34.5 cm. Median fish sizes at the stations ranged between 8.6 and 18.8 cm.
Quantitative stomach content analyses of a subsample of 175 specimens revealed that in the Northeast Water A. glacialis fed almost exclusively on pelagic prey. Truly benthic organisms were not found in the stomachs, and sympagic species were
rarely recorded. Overall, calanoid copepods were the major prey in terms of numbers. However, stomach contents varied considerably
between fish size groups. In terms of prey biomass, copepods dominated the diet of small fish (<12 cm), primarily occurring
at shallow stations (115–250 m), whereas amphipods and mysids were relatively more important for larger fish (>16 cm), which
dominated the catches at deep stations (360–480 m). The broad variety of diet composition indicated an opportunistic pelagic
feeding pattern.
Received: 6 November 1997 / Accepted: 11 May 1998 相似文献
15.
The hypersensitive response is associated with host and nonhost resistance to Phytophthora infestans
The interaction between Phytophthora infestans (Mont.) de Bary and Solanum was examined cytologically using a diverse set of wild Solanum species and potato (S. tuberosum L.) cultivars with various levels of resistance to late blight. In wild Solanum species, in potato cultivars carrying known resistance (R) genes and in nonhosts the major defense reaction appeared to be the hypersensitive response (HR). In fully resistant Solanum species and nonhosts, the HR was fast and occurred within 22 h. This resulted in the death of one to three cells. In partially
resistant clones, the HR was induced between 16 and 46 h, and resulted in HR lesions consisting of five or more dead cells,
from which hyphae were occasionally able to escape to establish a biotrophic interaction. These results demonstrate the quantitative
nature of the resistance to P. infestans. The effectiveness of the HR in restricting growth of the pathogen differed considerably between clones and correlated with
resistance levels. Other responses associated with the defense reaction were deposition of callose and extracellular globules
containing phenolic compounds. These globules were deposited near cells showing the HR, and may function in cell wall strengthening.
Received: 22 April 1999 / Accepted: 4 November 1999 相似文献
16.
G. A. Aguado-Santacruz J. L. Cabrera-Ponce E. Ramírez-Chávez C. G. León-Ramírez Q. Rascón-Cruz L. Herrera-Estrella V. Olalde-Portugal 《Plant cell reports》2001,20(2):131-136
A finely dispersed, homogeneous and highly chlorophyllous cell suspension (TIANSJ98 cell line) was obtained from shoot apices
of Bouteloua gracilis (H.B.K.) Lag. ex Steud. cultured on MPC medium containing MS salts supplemented with 2,4-D (1 mg/l), BAP (2 mg/l) and adenine
(40 mg/l). When the TIANSJ98 cell line was grown in this medium with shaking at 180 rpm it had doubling times of 7.2 and 3.7
days in terms of fresh and dry weight, respectively. Total chlorophyll content in this cell culture ranged from 121.6 to 18.3 μg/g FW
at 12 and 21 days following culture initiation. Plants regenerated from the TIANSJ98 cell line, via somatic embryogenesis,
were grown to maturity and produced seeds. Although different cell culture systems have been described for cereals and grasses,
to the best of our knowledge this is the first report of a highly chlorophyllous and regenerable cell suspension in Poaceae.
Received: 18 May 2000 / Revision received: 18 September 2000 / Accepted: 21 September 2000 相似文献
17.
V. M. King B. K. Follett 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,180(5):541-551
c-fos induction was investigated as a potential component in the avian photic entrainment pathway and as a possible means of locating
the central pacemaker in birds. In both quail (Coturnix coturnix japonica) and starlings (Sturnus vulgaris) exposure to 1 h of light induced Fos-lir in the visual suprachiasmatic nucleus but not in the medial suprachiasmatic nucleus. However, the degree of c-fos induction in the visual suprachiasmatic nucleus was similar at different circadian times despite the fact that the light
pulses caused differential phase shifts in the locomotor rhythm. For golden hamsters the same experiment resulted in significantly
different levels of Fos-lir in the suprachiasmatic nucleus, as well as different phase shifts. Starlings and hamsters were also entrained to T-cycles that caused a large daily phase shift (T = 21.5 h in starlings, T = 22.67 hours in hamsters), or no daily phase shift (T = free running period). No difference in the induced levels of Fos-lir in the visual suprachiasmatic nucleus region was observed between the two groups of starlings, but in hamsters there were
significantly different levels of Fos-lir in the suprachiasmatic nucleus between the two groups.
Accepted: 15 November 1996 相似文献
18.
The photomechanic infrared receptor for the detection of forest fires in the beetle Melanophila acuminata (Coleoptera: Buprestidae) 总被引:1,自引:0,他引:1
H. Schmitz H. Bleckmann 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1998,182(5):647-657
We recorded from single units of individual sensilla of the thoracic infrared (IR) pit organs of Melanophila acuminata. When the organ was stimulated with a thermal radiator whose emission spectrum was similar to that of a typical forest fire,
units responded phasically with up to seven spikes within 30–40 ms at a radiation power of 24 mW cm−2. In the experiments all wavelengths shorter than 1.6 μm were excluded by a longpass IR filter. Response latencies were about
4 ms and initial impulse frequencies were up to 250 impulses per second (ips). A single spike could be generated even when
stimulus duration was only 2 ms. Reduction of total radiation power from 24 mW cm−2 to 5 mW cm−2 resulted in increased response latencies of 5–6 ms and the occurrence of only two to three spikes. Initial impulse frequencies
decreased to 125 ips. According to our physiological results and calculations, Melanophila should be able to detect a 10-hectare fire from a distance of 12 km. Mechanical stimuli also evoked responses of the IR sensilla.
All present morphological and physiological findings lead to the conclusion that the IR receptors of Melanophila must function by means of a hitherto undescribed photomechanic mechanism.
Accepted: 1 November 1997 相似文献
19.
Three gracilarioid species, Gracilariopsis bailiniae and Gracilaria tenuistipitata from Vietnam and Gracilaria gracilis from Russia, were studied in order to determine whether Gracilaria gracilis might be a superior species for cultivation in brackish-water ponds for agar production compared with the Vietnamese species.
The effects of different salinity levels on the growth rate and agar production as well as agar properties of three gracilarioid
species were compared in controlled laboratory experiments. Gracilaria tenuistipitata and G. gracilis were tolerant to low salinity (∼10‰), whereas Gp. bailiniae died under these conditions. G. tenuistipitata showed superior growth among the three species examined. Gracilaria gracilis had the highest agar content [36.8–46.6% dry weight (dw)]. Agar yield from Vietnamese gracilarioids did not exceed 30% dw.
Gel strength of native agar from Gracilaria gracilis was two-fold higher that from Vietnamese species (278 g cm−2 vs 130 g cm−2). Alkali pretreatment increased gel strength significantly for Gracilaria gracilis (1.4-fold), and G. tenuistipitata and Gp. bailiniae (2.3-fold) compared with native agar. The results suggest that Gracilaria gracilis may be a suitable species for production of reasonably good quality agar. 相似文献
20.
To ascertain the feeding habits of benthic juvenile yellowfin goby Acanthogobius flavimanus, the gut contents of 599 specimens (15–41 mm in standard length, SL), collected on a tidal mudflat in the Tama River estuary
throughout the diel cycle, were examined. The major prey items changed from harpacticoid copepods to errant and sedentary
polychaetes at ca. 20 mm SL. Prey width increased with fish size. Fish of 26–28 mm SL fed mainly from sunset to morning, with
highest feeding intensity during twilight hours and/or high tide. Based on the gut evacuation rate estimated from a forced
feeding experiment in the laboratory and data for the diel change of mean gut-content volume in the field, the daily ration
of juvenile yellowfin goby (26–28 mm SL) was calculated to be 13.8 mm3 fish−1 day−1. This volume is approximately equivalent to 3.9 individuals of the errant polychaete Ceratonereis erythraeensis (9.7 mm in body length, BL) or 8.1 individuals of the sedentary polychaete Prionospio japonica (14.8 mm BL), both species occurring abundantly on the mudflat during the study. 相似文献