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1.
Since fishery management regulations have shifted much of the groundfish trawl effort in the northeastern Pacific from the
continental shelf to the slope, fishery impacts on unassessed demersal slope rockfish species like the aurora rockfish (Sebastes aurora) may have increased. Understanding the life history of these species is a critical first step in developing management strategies
to protect them from overharvest. In this study we employ cross-dating methods to validate the annual periodicity of growth
increments and investigate the age, growth and maturity of aurora rockfish, a species for which life history information is
quite limited. Specimens were collected on an opportunistic basis from Oregon commercial landings and from research cruises,
over the years 2003–2006. Age was estimated for 438 individuals using otoliths processed via the break-and-burn method. The
maximum estimated age was 118 years for females (n = 324) and 81 years for males (n = 114). The von Bertalanffy growth function showed that males grow faster and reach a smaller maximum size than females (males:
L
inf = 34, K = 0.09, t
0 = −1.9; females: L
inf = 37, K = 0.06, t
0 = −5.5), though both sexes demonstrate relatively slow growth. Visual assessment of ovaries showed that the aurora rockfish
is a synchronous spawner with parturition occurring in May and June off Oregon. Female age and length at 50% maturity were
calculated at 12.6 years and 26 cm, respectively (n = 307). Maturity and age data provided evidence for a protracted adolescence in this species. 相似文献
2.
Felipe Amezcua Ivan Martínez-Tovar Yanira Green-Ruiz Felipe Amezcua-Linares 《Ichthyological Research》2006,53(1):70-74
Age and growth of the tropical flatfish Cyclopsetta querna were determined from the sagittal otoliths. From yearly marginal growth increment trends, it was concluded that the opaque
and hyaline zones were formed annually. The oldest individual was a 43.2-cm (5-year-old) female. No significant differences
in length-at-age were found between sexes. The von Bertalanffy growth equation for the entire population was Lt = 60.71 (1 − e (−0.245(t−0.408))). The life span of these species is short, about 5 years. The otoliths proved a reliable structure to determine age of this
species. 相似文献
3.
The growth rate, reproductive aspects, and natural mortality of chimaeras and ratfish are poorly known. In this study, life-history
parameters for cockfish Callorhinchus callorhynchus (Holocephali—Callorhinchidae) are estimated, which is an important fish resource exploited in Chile. Specimens were sampled
from the artisanal fishery captures, from November 2006 to November 2007. The standard length (SL) of males fluctuated between
20 and 62 cm, and between 21 and 70 cm for females. Von Bertalanffy growth parameters were estimated through length-frequency
data analysis using MULTIFAN. The length-weight relationship and von Bertalanffy growth parameters were significantly different
for males and females, as well as the length at 50% maturity. For males a model with 5 age-classes was the best, with asymptotic
length L
∞ = 52 cm SL, growth coefficient K = 0.473 yr−1, and age at length zero t
0 = −0.690 yrs. For females the best model was represented by 10 age-classes (L
∞ = 70.3 cm SL, K = 0.193 yr−1, t
0 = −1.158 yrs) in the length-frequency data sets. Length at 50% maturity of males was estimated in 43.7 cm SL, and in 50.2 cm
SL for females. The natural mortality rate fluctuated between 0.42 and 0.82 yr−1 for males and between 0.12 and 0.37 yr−1 for females, depending upon the method used. It is concluded that C. callorhynchus is a species with life-history parameters significantly different between males and females, and such differences should
be taken into account in future population dynamics analysis. 相似文献
4.
Nelusetta ayraudi (the ocean leatherjacket) is an endemic Australian monacanthid species distributed from North West Cape (Western Australia)
south to southern Queensland. The commercial and recreational fisheries targeting Nelusetta ayraudi have expanded substantially along the coast of New South Wales (NSW) in recent years but there exists little biological information
on which to base effective management of this growing fishery. World-wide, only a few studies have aged monacanthids. Of these,
researchers have interpreted periodic increments in bony structures such as vertebrae and anterior dorsal spines in preference
to those found in otoliths. In this study we estimated age of N. ayraudi by counting growth increments in sectioned otoliths. The periodicity of increment formation was validated using a vital stain,
(oxy-tetracycline), injected into young-of-the-year fish. Growth was rapid especially as juveniles with N. ayraudi attaining approximately 220 mm after 1 year and 340 mm after 2 years. No differences in growth rates were detected between
sexes or between fish captured at different latitudes (zones). The largest male (605 mm, Total Length—TL) and female (656 mm,
TL) were both recorded from northern NSW, with both sexes attaining the maximum age of 6+ years from northern and southern
NSW. The von Bertalanffy parameters describing growth for N. ayraudi were L¥ {L_\infty } = 591 mm (TL), k = 0.377 year−1 and t
o = −0.247 years. 相似文献
5.
Several growth hypotheses have been tested to investigate why males of the sequential hermaphrodite, Mediterranean rainbow
wrasse, Coris julis (Linnaeus, 1758), are relatively larger than females of the same age. Individual growth trajectories were estimated to test
these hypotheses. A good linear relationship between otolith size and body size was observed (r
2
= 0.71, n = 609), thus, past somatic growth of any specific fish can be inferred from the longitudinal data described by the width
of annual increments in the otolith. These data were successfully analyzed by a non-linear mixed-effect model (von Bertalanffy
growth model) using a Bayesian approach. The results obtained suggest that Mediterranean rainbow wrasse secondary males are
relatively larger than females because 1) fish that change sex are already the larger individuals in their age group (specifically
those with higher growth rate, k
secondary males
= 0.199 and k
females
= 0.161) and 2) they experience a growth spurt after sex change. The differences in growth observed in this species and in
other protogynous hermaphrodites could be related to differences in social organization, which, in turn, are related to differences
in the sex change mechanisms. 相似文献
6.
Schizopygopsis younghusbandi younghusbandi is an endemic species whose distribution is restricted to the middle reaches of the Yarlung Zangbo River, being one of the
most important commercial fishes in this area. Age and growth of 606 specimens captured between October 2002 and April 2005
were studied. The range in standard length (L) was 65.7–387.3 mm and total weight (W) was 3.3–772.0 g. The relationship between
L and W was W = 0.000909L2.2493 for males and W = 0.000259L2.4781 for females. Age, determined from anal scales and lapillus otoliths, ranged from 3 to 18 years. The parameters of von Bertalanffy
growth functions, estimated by back-calculated length, were L¥ = 442.7mm LL_\infty = 442.7mm\;L, k = 0.0738 year−1 and t
0
= −1.4 year for males, and L¥ = 471.4mm LL_\infty = 471.4mm\;L, k = 0.0789 year−1 and t
0 = 0.2 year for females. Males and females exhibited statistically significant differences in growth. χ
2-test indicated that von Bertalanffy growth functions could well describe the growth of S. y. younghusbandi. The longevities were 39.2 and 38.2 years for males and females, respectively. Growth inflexion points were 10.2 and 12.0 years
for males and females, respectively, but 84.8% of the captures were at the smaller ages. So conservation and management schemes
for this population should be considered urgently. In addition, we found that populations from the upstream of the Lhasa River,
the downstream of the Lhasa River and the middle reaches of the Yarlung Zangbo River showed statistically significant differences
in growth patterns. 相似文献
7.
A feeding trial was performed in the laboratory with the catfish species Pterygoplichthys disjunctivus to determine stable carbon (13C) and nitrogen (15 N) turnover rates and discrimination factors in non-lethally sampled tissues (red blood cells, plasma solutes, and fin).
A second feeding trial was conducted to determine what P. disjunctivus could assimilate from low-quality wood-detritus—refractory polysaccharides (e.g., cellulose), or soluble wood-degradation products inherent in wood-detritus. This was performed
by feeding the fish an artificial wood-detritus diet with fibrous (δ13C = −26.36‰; δ15
N = 2.13‰) and soluble portions (δ13C = −11.82‰; δ15
N = 3.39‰) that had different isotopic signatures and monitoring the dynamics of isotopic incorporation in the different tissues
over time. Plasma solutes turned over more quickly than red blood cells for 13C and 15 N. However, in contrast to previous studies of juvenile fishes, C and N incorporation was primarily driven by catabolic tissue
turnover as opposed to growth rate. Tissue-diet discrimination factors for 15 N varied from 4.08 to 5.17‰, whereas they were <2‰ for 13C (and less than 0.3‰ for plasma and red blood cells). The results of trial two suggested that P. disjunctivus could not assimilate refractory polysaccharides. Moreover, the δ13C and δ15 N signatures of wild-caught P. disjunctivus from Florida confirmed their detrital trophic standing in Floridian aquatic ecosystems. 相似文献
8.
Pulvinus activity of Phaseolus species in response to environmental stimuli plays an essential role in heliotropic leaf movement. The aims of this study
were to monitor the continuous daily pulvinus movement and pulvinus temperature, and to evaluate the effects of leaf movements,
on a hot day, on instantaneous leaf water-use efficiency (WUEi), leaf gas exchange, and leaf temperature. Potted plants of Phaseolus vulgaris L. var. Provider were grown in Chicot sandy loam soil under well-watered conditions in a greenhouse. When the second trifoliate
leaf was completely extended, one plant was selected to measure pulvinus movement using a beta-ray gauging (BRG) meter with
a point source of thallium-204 (204Tl). Leaf gas exchange measurements took place on similar leaflets of three plants at an air temperature interval of 33–42°C
by a steady-state LI-6200 photosynthesis system. A copper-constantan thermocouple was used to monitor pulvinus temperature.
Pulvinus bending followed the daily diurnal rhythm. Significant correlations were found between the leaf-incident angle and
the stomatal conductance (R
2 = 0.54; P < 0.01), and photosynthesis rate (R
2 = 0.84; P < 0.01). With a reduction in leaf-incidence angle and increase in air temperature, WUEi was reduced. During the measurements, leaf temperature remained below air temperature and was a significant function of air
temperature (r = 0.92; P < 0.01). In conclusion, pulvinus bending followed both light intensity and air temperature and influenced leaf gas exchange. 相似文献
9.
ETA subtype selective antagonists constitute a novel and potentially important class of agents for the treatment of pulmonary
hypertension, heart failure, and other pathological conditions. In this paper, 60 benzodiazepine derivatives displaying potent
activities against ETA and ETB subtypes of endothelin receptor were selected to establish the 3D-QSAR models using CoMFA and CoMSIA approaches. These models
show excellent internal predictability and consistency, external validation using test-set 19 compounds yields a good predictive
power for antagonistic potency. Statistical parameters of models were obtained with CoMFA-ETA (q
2 = 0.787, r
2 = 0.935, r
2
pred
= 0.901), CoMFA-ETB (q
2 = 0.842, r
2 = 0.984, r
2
pred
= 0.941), CoMSIA-ETA (q
2 = 0.762, r
2 = 0.971, r
2
pred
= 0.958) and CoMSIA-ETB (q
2 = 0.771, r
2 = 0.974, r
2
pred
= 0.953) respectively. Field contour maps (CoMFA and CoMSIA) corresponding to the ETA and ETB subtypes reflects the characteristic similarities and differences between these types. The results of this paper provide
valuable information to facilitate structural modifications of the title compounds to increase the inhibitory potency and
subtype selectivity of endothelin receptor. 相似文献
10.
J. B. K. Leonard J. F. Norieka B. Kynard S. D. McCormick 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(4-5):287-295
To assess the energetics of migration in an anadromous fish, adult American shad (Alosa sapidissima) were swum in a large respirometer at a range of speeds (1.0–2.3 body lengths (BL) s−1, 13–24 °C). Metabolic rate (MO2) was logarithmically related to swimming speed (Bl s−1; r
2 = 0.41, slope = 0.23 ± 0.037) and tailbeat frequency (beats × min−1; r
2 = 0.52, slope = 0.003 ± 0.0003). Temperature had a significant effect on metabolic rate (r
2 = 0.41) with a Q10 of 2.2. Standard metabolic rate (SMR), determined directly after immobilization with the neuroblocker gallamine triethiodide,
ranged from 2.2–6.2 mmolO2 kg−1 h−1 and scaled with mass (W) such that SMR = 4.0 (±0.03)W0.695(±0.15). Comparison of directly determined and extrapolated SMR suggests that swimming respirometry provides a good estimate of SMR
in this species, given the differences in basal activity monitored by the two methods. Overall, American shad metabolic rates
(MO2 and SMR) were intermediate between salmonids and fast-swimming perciforms, including tunas, and may be a result of evolutionary
adaptation to their active pelagic, schooling life history. This study demonstrates variability in metabolic strategy among
anadromous fishes that may be important to understanding the relative success of different migratory species under varying
environmental conditions.
Accepted: 3 March 1999 相似文献
11.
Kinetics of styrene biodegradation by <Emphasis Type="Italic">Pseudomonas</Emphasis> sp. E-93486 总被引:1,自引:0,他引:1
The research into kinetics of styrene biodegradation by bacterial strain Pseudomonas sp. E-93486 coming from VTT Culture Collection (Finland) was presented in this work. Microbial growth tests in the presence
of styrene as the sole carbon and energy source were performed both in batch and continuous cultures. Batch experiments were
conducted for initial concentration of styrene in the liquid phase changed in the range of 5–90 g m−3. The Haldane model was found to be the best to fit the kinetic data, and the estimated constants of the equation were: μ
m = 0.1188 h−1, K
S = 5.984 mg l−1, and K
i = 156.6 mg l−1. The yield coefficient mean value
Y\textxs\textapp Y_{\text{xs}}^{\text{app}} for the batch culture was 0.72 gdry cells weight (gsubstrate)−1. The experiments conducted in a chemostat at various dilution rates (D = 0.035–0.1 h−1) made it possible to determine the value of the coefficient for maintenance metabolism m
d = 0.0165 h−1 and the maximum yield coefficient value
Y\textxs\textM = 0.913 Y_{\text{xs}}^{\text{M}} = 0.913 . Chemostat experiments confirmed the high value of yield coefficient
Y\textxs\textapp Y_{\text{xs}}^{\text{app}} observed in the batch culture. The conducted experiments showed high activity of the examined strain in the styrene biodegradation
process and a relatively low sensitivity to inhibition of its growth at higher concentrations of styrene in the solution.
Such exceptional features of Pseudomonas sp. E-93486 make this bacterial strain the perfect candidate for technical applications. 相似文献
12.
13.
Daria Ezgeta-Balić Melita Peharda Christopher A. Richardson Marina Kuzmanić Nedo Vrgoč Igor Isajlović 《Helgoland Marine Research》2011,65(4):457-465
The age, growth, and population structure of the smooth clam Callista chione were determined from samples collected by hydraulic dredge and SCUBA at four locations in the eastern Adriatic during 2007
and 2008. The age of 436 clam shells was determined from internal growth lines present in shell sections, and the timing of
growth line formation was ascertained from monthly collections of clams to occur between August and September when sea water
temperatures were maximal. In addition, age of 30 older individuals was verified with acetate peels of polished and etched
shell sections. Differences were apparent in the age structure and growth rates of clams collected from the four locations
studied. Von Bertalanffy growth (VBG) curves obtained for clams from these locations were L
t
= 72.4 (1−e−0.25(t − 2.68)) (Rab Island), L
t
= 74.5 (1−e−0.15(t + 0.57)) (Pag Bay), L
t
= 79.3 (1−e−0.34(t − 0.97)) (Cetina estuary), and L
t
= 82.5 (1−e−0.11(t + 2.88)) (Kaštela Bay). The age of the clams ranged between 3 and 44 years; median clam ages were similar at three of the four locations
(14, 12, and 12 years, respectively), but was significantly lower in the Cetina estuary (4 years). The VBG growth constants
recorded from clams were within the range of values obtained for this species by previous authors. The observed local differences
in population structure indicate different levels of exploitation and illustrate the need to establish long-term strategies
for a sustainable exploitation of smooth clams in the Croatian Adriatic. 相似文献
14.
William E. Magnusson M. Carmozina de Araújo Renato Cintra Albertina P. Lima Luiz A. Martinelli Tânia M. Sanaiotti Heraldo L. Vasconcelos Reynaldo L. Victoria 《Oecologia》1999,119(1):91-96
We studied the energy flow from C3 and C4 plants to higher trophic levels in a central Amazonian savanna by comparing the carbon stable-isotope ratios of potential
food plants to the isotope ratios of species of different consumer groups. All C4 plants encountered in our study area were grasses and all C3 plants were bushes, shrubs or vines. Differences in δ13C ratios among bushes (xˉ = −30.8, SD = 1.2), vines (xˉ = −30.7, SD = 0.46) and trees (xˉ = −29.7, SD = 1.5) were small. However the mean δ13C ratio of dicotyledonous plants (xˉ = −30.4, SD = 1.3) was much more negative than that of the most common grasses (xˉ = −13.4, SD = 0.27). The insect primary consumers had δ13C ratios which ranged from a mean of −29.5 (SD = 0.47) for the grasshopper Tropidacris collaris to a mean of −14.7 (SD = 0.56) for a termite (Nasutitermes sp.), a range similar to that of the vegetation. However, the common insectivorous and omnivorous vertebrates had intermediate
values for δ13C, indicating that carbon from different autotrophic sources mixes rapidly as it moves up the food chain. Despite this mixing,
the frogs and lizards generally had higher values of δ13C (xˉ = −21.7, SD = 1.6; xˉ = −21.9, SD = 1.8, respectively) than the birds (xˉ = −24.8, SD = 1.8) and the only species of mammal resident in the savanna (xˉ = −25.4), indicating that they are generally more dependent on, or more able to utilise, food chains based on C4 grasses.
Received: 7 May 1998 / Accepted: 30 November 1998 相似文献
15.
Alma R. López-Laredo Fanny D. Ramírez-Flores Gabriela Sepúlveda-Jiménez Gabriela Trejo-Tapia 《In vitro cellular & developmental biology. Plant》2009,45(5):550-558
Tecoma stans is a tropical plant from the Americas. Antioxidant activity and both phenolic compound and flavonoid total content were determined
for callus tissue of T. stans cultured in either a set photoperiod or in darkness. Callus lines from three explant types (hypocotyls, stem, and leaf) were
established on B5 culture medium supplemented with 0.5 μM 2,4-D and 5.0 μM kinetin. While leaf-derived callus grew slower
under a 16-h photoperiod (specific growth rate, μ = 0.179 d−1, t
D = 3.9 d) than in darkness (μ = 0.236 d−1, t
D = 2.9 d), it accumulated the highest amount (p < 0.05) of both phenolics (86.6 ± 0.01 mg gallic acid equivalents/g) and flavonoids (339.6 ± 0.06 mg catechin equivalents/g).
Similarly, antioxidant activity was significantly higher (p < 0.05) when callus was cultured in period light than when grown in extended darkness. Antioxidant activity measured with
a 2,20-azinobis (3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt (ABTS)-based assay was 350.5 ± 15.8 mmol Trolox/g
extract for callus cultured under a defined photoperiod compared to 129.1 ± 7.5 mmol Trolox/g extract from callus cultured
in darkness. Content of phenolic compounds and flavonoids was in agreement with a better antioxidant power (EC50 = 450 μg extract/mg 1,1-diphenyl-2-picrylhydrazyl) and antiradical efficiency. Results of the present study show that calli
of T. stans are a source of compounds with antioxidant activity that is favored by culture under a set photoperiod. 相似文献
16.
D. Audet D. W. Thomas 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(2):146-152
The present study questions whether hypothermia is an artifact due to captivity-induced stress or a thermoregulatory strategy
for bats of the neotropical family Phyllostomidae. In Guanacaste, Costa Rica, Carollia perspicillata and Sturnira lilium exhibited a bimodal distribution of body temperatures when submitted to an ambient temperature of 21 °C. Body temperature
was highly correlated with body mass in both species. C. perspicillata of mass ≥20 g and S. lilium of mass ≥17 g remained normothermic (body temperature >37 °C), whereas at masses below 18 g and 13 g, respectively, >80%
of individuals were hypothermic (body temperature ≤32 °C). In two treatment groups for each species, we restricted food intake
to ca. 20% of body mass on either night 1 or night 4 following capture. Hypothermia was significantly related to food-restriction,
but not time in captivity. Metabolic rate (ml O2 · g−1 h−1) at ambient temperature = 21 °C was MR = e
(–2.11 + 0.101 Tb) (r
2 = 0.7, P < 0.001) for C. perspicillata and MR = e
(−2.62 + 0.115 Tb) (r
2 = 0.89) for S. lilium. Free-ranging, radio tagged C. perspicillata exhibited daily depression of body temperature to 33–34 °C. We conclude that hypothermia is an thermoregulatory strategy
that allows phyllostomid bats to adjust metabolic rate to feeding success and the level of fat stores.
Accepted: 20 August 1996 相似文献
17.
Life history parameters associated with reproductive biology, age, and growth of the convict cichlid (also known as the zebra
cichlid) Amatitlania nigrofasciata, which was introduced into the Haebaru Reservoir on Okinawa-jima Island, were estimated using 437 specimens that ranged from
13.7 to 82.9 mm standard length (SL). Lengths of females at first maturity (SL) and 50% maturity (L
50) were estimated to be 32.2 and 37.3 mm SL, respectively. The spawning period continued throughout the year, with a peak spawning
cycle from March to May 2006–2007. Observations of postovulatory follicles and tertiary yolk stage oocytes indicate that convict
cichlids spawn multiple times within a year. Female cichlids that hatched during the peak spawning seasons matured after October
of the same year. Batch fecundity of females (32.2–61.2 mm SL) ranged from 65 to 345 (mean ± SD = 155 ± 63). Opaque zones
along the outer margins of otoliths formed annually. The maximum age of male and female cichlids was 3 years. The von Bertalanffy
growth formulae (VBGF) were expressed as Lt = 57.4( 1 - e - 0.78( t + 0.91 ) ) {{\hbox{L}}_{\rm{t}}}{ = 57}{.4}\left( {1 - {e^{ - 0.78\left( {t + 0.91} \right)}}} \right) for females and Lt = 69.5( 1 - e - 1.07( t + 0.24 ) ) {{\hbox{L}}_{\rm{t}}}{ = 69}{.5}\left( {1 - {e^{ - 1.07\left( {t + 0.24} \right)}}} \right) for males. Males grew larger than females beginning from the first year. Certain life history characteristics, such as year-round
spawning and early maturation, probably contributed to the successful establishment of the convict cichlid, and this species
in particular is thought to adapt and become established quickly upon introduction to freshwater systems on Okinawa-jima Island. 相似文献
18.
Aspects of body size and gonadal histology in the Antarctic toothfish, Dissostichus mawsoni, from McMurdo Sound, Antarctica 总被引:4,自引:4,他引:0
Twenty-eight specimens of the large notothenioid Dissostichus mawsoni were dissected after capture on a set line near the southern limit of its range in McMurdo Sound, Antarctica. Total length
(L
T) averaged 127.3 cm (range 90–162 cm) and weight (W ) was 26.7 kg (range 10.4–60.3 kg). The length-weight relationship was W=3.44×10−5
L
T
2.85 (n=28, r
2=0.96). Subcutaneous lipid thickness averaged 2.6 mm and showed no difference due to sex, but a significant weak relationship
to W and L
T. Hepatosomatic index (I
H) was 1.6% for females and 1.7% for males; gonadosomatic index (I
G) was 0.9% for females and 0.2% for males. Although specimens were large and sexually mature, the histology indicated that
the gonads of this November sample were in a resting stage. Testes lacked spermatids and spermatozoa. Oocytes were in the
previtellogenic stage (91.2%) or in the first stage of vitellogenesis (8.8%). A few atretic oocytes and empty follicles indicated
that some females in this sample had spawned previously. A summary of the life-cycle is also presented.
Accepted: 27 September 1999 相似文献
19.
The chromosomes of 31 species of Passiflora, distributed throughout the subgenera Astrophea, Calopathanthus, Distephana, Dysosmia, Passiflora, Plectostemma and Tacsonia were analysed. Three different karyotypes were observed: 2n = 12, 24, 36; 2n = 18, 72 and 2n = 20. The karyotype of these
species was almost always constituted of metacentric and submetacentric chromosomes with variable karyotype symmetry. In the
group with x = 6, represented by the subgenus Plectostemma, six diploid species with 2n = 12, one tetraploid with 2n = 24 (P. suberosa) and an intraspecific polyploid with 2n = 12, 36 (P. misera) were analysed. P. pentagona (subgenus Astrophea) may also be included in this karyological group since it presents 2n = 24 and may be of polyploid origin, with x = 6. The
interphase nuclei in this group were areticulate, except those of P. morifolia and P. pentagona with semi-reticulate characteristics. Two small terminal heterochromatic blocks, positive for chromomycin A3, were identified in the largest chromosome pair of P. capsularis and P. rubra, species very closely related, while P. tricuspis displayed four chromosomes with proximal blocks. In the group with x = 9, represented mainly by subgenus Passiflora, 20 species with 2n = 18 and one with 2n = 72 were studied. They presented chromosomes larger than those species with x = 6
and interphase nuclei of semi-reticulate type, except for P. mixta with areticulate nuclei. Four terminal CMA+ blocks were observed in P. edulis, six blocks in P. caerulea and P. racemosa, while five blocks were observed in the single P. amethystina plant analysed. P. foetida (subgenus Dysosmia), the only species with 2n = 20, exhibited six chromosomes with CMA+ blocks and interphase nuclei of the areticulate type. The meiotic analysis of representatives of the three groups (P. foetida, P. suberosa, P. cincinnata and P. racemosa) always presented regular pairing and regular chromosome segregation, except in P. jilekii where a tetravalent was observed. The analysis of the chromosome variation within the genus and the family suggests that
the base number of Passiflora may be x1 = 6 or x1 = 12, whereas x2 = 9 is only an important secondary base number.
Received April 11, 2000 Accepted October 5, 2000 相似文献
20.
Elongate loach (Leptobotia elongata (Bleeker)), an endemic fish species to China, is a famous ornamental freshwater fish. Here, a comparative study of mtDNA
control region (D-loop) (835 bp) sequences was performed to analyze its wild population structure and evaluate the genetic
diversity for 110 individuals from five locations in the upper reaches of the Yangtze River, China. A total of 49 polymorphic
sites and 45 haplotypes yielded high haplotype diversity (h = 0.952), but low nucleotide diversity (π = 0.00454) as that of many fish species. Sequence divergences between haplotypes ranged from 0.0033 ± 0.0011 to 0.0050 ± 0.0012
in intra-groups, and from 0.0037 ± 0.0.0011 to 0.0050 ± 0.0012 between groups. Significant values of Tajima’s D (−1.86383, P < 0.01) and Fu’s F
S (−25.93, P < 0.01), together with uni-modal mismatch distribution, indicated a recent genetic bottleneck or population expansion of
the species. Analysis of molecular variance (AMOVA) indicated a small amount of differentiation among groups (1.7%); most
of the total variation occurred within groups (98.3%). Also, there was no significant population structure (F
ST = 0.017, P > 0.05), and estimates of gene flows among groups were extremely high (Nm = 28.88), suggesting low genetic divergence between populations in the species. The lack of genetic differentiation among
groups is most likely due to the combined gene flow from the downstream movement of eggs and larvae with currents and the
upstream or downstream migration of adults throughout the distribution. These groups of L. elongata distributed in upper reaches of the Yangtze River should be considered as a single management unit. 相似文献