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1.
Summary The nucleotide sequence of the rpsE gene for the ribosomal protein S5 of a mutant of E. coli showing cold-sensitive growth revealed the presence of an insertion sequence, IS1, near the 3-end of the gene. This mutant grows very slowly even at the permissive temperature (30°C). At temperatures below 20°C, its growth becomes negligible. It is likely that the presence of IS1 disturbs the continued translation of the polycistronic messenger RNA of the spc-operon from the point of IS1 insertion downwards, especially at the unfavorable temperatures.  相似文献   

2.
On the basis of symposium contributions onChlorella, Hibbertia, Eucalyptus, Ambrosia and on numerical approaches some fundamental problems of (bio)systematics, evolution, and taxonomic categories are discussed: Methods available for analysing affinities; conflicting evidence from phenetic, biochemical, cytogenetic and other analyses; further classification problems in cases of intermediacy, etc. While sibs of various levels and their natural hierarchy often can be objectively defined, this appears impossible for particular taxonomic levels itself (e. g. species). A single objective taxonomic system of organisms is unrealistic. Certain guiding lines for relative and practicable concepts of species and genus are proposed.Presented at the symposium Speciation and the Species Concept during the XIIth International Botanical Congress, Leningrad, July 8, 1975.  相似文献   

3.
Incubation of synthetic Man\1-4GlcNAc-OMe, GalNAc1-4GlcNAc-OMe, Glc1-4GlcNAc-OMe, and GlcNAc1-4GlcNac-OMe with CMP-Neu5Ac and rat liver Gal1-4GlcNAc (2-6)-sialyltransferase resulted in the formation of Neu5Ac2-6Man1-4GlcNAc-OMe, Neu5Ac2-6GalNAc1-4GlcNAc-OMe, Neu5Ac2-6Glc1-4GlcNAc-OMe and Neu5Ac2-6GlcNAc1-4GlcNAc-OMe, respectively. Under conditions which led to quantitative conversion of Gal1-4GlcNAc-OEt into Neu5Ac2-6Gal1-4GlcNAc-OEt, the aforementioned products were obtained in yields of 4%, 48%, 16% and 8%, respectively. HPLC on Partisil 10 SAX was used to isolate the various sialyltrisaccharides, and identification was carried out using 1- and 2-dimensional 500-MHz1H-NMR spectroscopy.Abbreviations 2D 2-dimensional - CMP cytidine 5-monophosphate - CMP-Neu5Ac cytidine 5-monophospho--N-acetylneuraminic acid - COSY correlation spectroscopy - DQF double quantum filtered - HOHAHA homonuclear Hartmann-Hahn - MLEV composite pulse devised by M. Levitt - Neu5Ac N-acetylneuraminic acid - Neu5Ac2en 2-deoxy-2,3-didehydro-N-acetylneuraminic acid  相似文献   

4.
Zusammenfassung Harzkonservierte Fossilien ermöglichen bei Anwendung adäquater Methoden die morphologische Analyse der Feinmerkmale bis zur Auflösungsgrenze des Lichtmikroskops, Beobachtung in verschiedenen Ebenen und Richtungen, und somit konkrete Rückschlüsse auf die Wirkung und Bedeutung der Einzelelemente und des Gesamtgefüges.Eine so eingehende funktionsmorphologische Analyse mit Berücksichtigung der Positionsvariation (graduell verschiedene Gestaltung in gesetzmäßiger Abhängigkeit von der Lage innerhalb der Gesamtfeder) der Einzelelemente wie Abzweigungs-, Knick-, Neigungswinkel, Krümmung, Länge, Dicke, Querschnitt, Dichte, Differenzierungsgrad der verschiedenen Abschnitte von Rhachis, Rami, Radii inklusive Häkchen und Cirren wird erstmals für fossile Vogelfedern geliefert (hier als Abriß zu einer dokumentarisch und thematisch ausführlicheren Darstellung in Stuttgarter Beiträge zur Naturkunde).Diese Federn entstammen der untersten Unterkreide und sind damit nur relativ wenig jünger alsArchaeopteryx. Sie weisen extrem differenzierten Aufbau auf, der auf hohe flugtechnische und wärmeisolierende Leistungsfähigkeit schließen läßt.Die hier vorgelegten funktionsmorphologischen Ermittlungen an fossilen Körperkonturfedern mögen auch zu einer intensiveren Analyse der bis jetzt stark vernachlässigten Untersuchung ganz normaler Körperfedern rezenter Vögel anregen. Erst dann, nach umfassender Kenntnis ihrer Ausgestaltung innerhalb der verschiedensten rezenten Vogelgruppen, läßt sich überzeugend begründen, ob und wieweit die hier vorgelegten Federn dieses Unterkreide-Vogels noch ursprüngliche Elemente (Plesiomorphien) oder ihnen eigene Sonderbildungen (Autapomorphien) aufweisen; das gilt sowohl für morphologische wie für funktionelle Elemente der Gesamtstruktur.
Resin-preserved fossil bird's feathers from the Lowermost Cretaceous
Summary Parts of some feathers, originating from a single bird, were discovered in our collections of Lower Cretaceous amber from the Lebanon mountains — which, in general, contains the oldest terrestrial microfossils preserved with all morphological details.These contour feathers of the trunk, which are nearly as old as Archaeopteryx (Lowermost Cretaceous: Neocomian/Uppermost Jurassic: Kimmeridigian) were studied with magnifications of 500–900 in several levels by a special technique. (In normal fossils, i.e., impressions, the granulation of the sediment and the fossil's bulky carbon remainders cause a blurred image even at a magnification of merely 100).Special emphasis was laid on the study of the individual elements' gradual variation, depending on the respective position within the total feather (position variation). Where appropriate, an analysis of lengths, quantity, degree of differentiation, angle of inclination, break, and branching, cross-sectional view, curvature, etc. of the rhachis, rami, distal and proximal radii, barbicles, hooklets, etc. were undertaken. [Through measurements of the depth of details the effects caused by a sloping position (apparent variation) may be precisely separated from the real variation.]On the basis of such a detailed knowledge of structure and relative position a thorough functional analysis of the single elements as well as the total system is given.Principal features: The production of plain stability in the feather's center, and of flexibility in its apical and lateral rims; dispersion of forces in case of pressure or a pulling load; function of the hooklets (which donot serve as an interlocking mechanism while the feather is in the normal resting position, but function with increasing braking action only when a neighboring ramus diverges to a precisely defined extent from its resting position) including the mechanism of their unhooking; devices for the avoidance of harmful hooking into contacted parts of other feathers; production of maximal stability by minimal air resistance, and of minute chambers (<0,00001 mm3) with still air for optimal heat isolation.Apart from this abstract, further information, accompanied by numerous figures, will be given in a later paper in Stuttgarter Beiträge zur Naturkunde.


Veränderte Fassung eines am 11. 10. 1971 gehaltenen Vortrages auf der 83. Jahresversammlung der Deutschen Ornithologengesellschaft in Bonn.  相似文献   

5.
A comprehensive sequence analysis of three early chorion genes (6F6.1, 6F6.2, 6F6.3) which form a small subfamily is presented. Two main features characterize this subfamily: (1) the 6F6 gene copies are -branch genes and, unlike typical chorion genes which are organized in divergent gene pairs, they are unpaired, and (2) they are not clustered in genetic locus Ch3 but are dispersed in Ch1-2, which is about 3 to 4 centiMorgans away and contains middle and late chorion genes. Sequence comparisons show that members of this subfamily exhibit high identity values in their major coding region (94–96%) and that similarities also extend, but to a lesser degree, into their noncoding regions. The putative 6F6 promoter regions have no significant similarities with the corresponding regions of other early -genes but quite surprisingly share common elements with middle and late genes. The main difference among the 6F6 gene introns is the presence of inserted sequences: the insert into 6F6.2 (IR; 248 bp) is flanked by a 102–103-bp inverted repeat, while those into 6F6.1 (FIB; 184 bp) and 6F6.3 (HOPE; 951 bp) are carried by a partial Bm1 element. HOPE has features of a non-LTR retrotransposable element. Preliminary experiments indicate that the copy number of IR and HOPE in the Bombyx mori genome is about 5,000 and 20,000, respectively. The great similarity of 6F6 genes cannot be accounted for by selective pressure but rather appears to be the result of gene-conversion-like events, which are supposed to operate frequently in middle and late chorion genes but not in other known early -genes. Using the relative position and orientation of the 6F6 gene copies, it is possible to propose an evolutionary scheme for the formation of chorion locus Ch1-2. Correspondence to: G.C. Rodakis  相似文献   

6.
Summary In these experiments, a considerable range of hydroxysteroid dehydrogenases were demonstrated in vertebrate hepatic tissue; 3, 3, 6, 11, 16, 16, 17 and 20 were consistently present.3 hydroxysteroid dehydrogenase was fairly active in mammalian liver, but consistently greater activity was seen with the 3 dehydrogenases which are probably concerned with steroid detoxication and excretion. 6 and 11 hydroxysteroids were only moderately well used, and both these were noticeably better used in male tissue, as were also 3, 3, 16 and 16 hydroxysteroids. All mammalian liver utilised 16, 16 and 17 compounds fairly well, and 20 was consistently but poorly used.This histochemical evidence agrees with biochemical and clinical evidence for the significance and nature of steroid metabolism in the liver. Many of the enzymes showing activity in the liver have known function in the detoxication and elimination of steroids; and 3-hydroxysteroid dehydrogenase is concerned in cholesterol biosynthesis as well as the biosynthesis of progesterane. To have shown contrasting patterns of activity between liver and steroid producing endocrine tissues is further evidence for the specificity of these techniques in the study of dehydrogenase distribution.  相似文献   

7.
The polypeptide structure and assembly of Ly-2/3 heterodimers   总被引:1,自引:0,他引:1  
Mild reduction of mature, thymic Ly-2/3 heterodimers of M r 67 000 resulted in dissociation into three individual polypeptide chains, , , and , of respective M r values 38000, 35000, and 30000. The and chains were both immunoprecipitated by a monoclonal antibody directed to the Ly-2.1 epitope whereas the Ly-3.1 antibody bound only the chain. The possibility that the and chains of each heterodimer established their interchain links within a labile precursor protein in which a and segments were fused was considered but discounted by the finding that in mice heterozygous for both Ly-2 and Ly-3 loci, the Ly-2 product of one chromosome was not exclusively joined to Ly-3 structures coded by the same chromosome. By utilizing ionic detergents which selectively alter the charge of intrinsic membrane proteins, both Ly-2 and Ly-3 polypeptides were shown to have membrane insertion sites. It is suggested that as a consequence of their likely synthesis on membrane-bound polysomes, newly synthesized Ly-2 and Ly-3 structures accumulate within the same subcellular compartment — the membranes of the rough endoplasmic reticulum. Their elevated concentration within this space may facilitate a low affinity binding interaction between Ly-2 and Ly-3 which is later stabilized by interchain disulfide bond formation.Abbreviations used in this paper BSA bovine serum albumin - DOC sodium deoxycholate - DTT dithiothreitol - HA hemagglutinin - HTAB hexadecyltrimethylammonium bromide - RER rough endoplasmic reticulum - SDS-PAGE sodium dodecyl sulfate polyacrylamide gel electrophoresis - TX100 Triton X-100  相似文献   

8.
The genes were cloned for the two apoprotein subunits, and ,of phycocyanin from the cyanobacterium Spirulina maxima = Arthrospiramaxima) strain F3. The - and -subunit gene-coding regionscontain 489 bp and 519 bp, respectively. The -subunit gene is upstreamfrom the -subunit gene, with a 111-bp segment separating them.Similarities between the -subunits of S. maxima and nine othercyanobacteria were between 58% and 99%, as were those between the -subunits. The maximum similarity between the - and -subunits from S. maxima was 27%.  相似文献   

9.
Summary Simultaneous overproduction of intracellular -glucosidase and extracellular endoglucanase was attempted by constructing two artificial operon systems comprising the -glucosidase-endoglucanase gene(E) or the endoglucanase--glucosidase gene(E) under the control of a strong engineered promoter, BJ27U88 and expressing them in Bacillus subtilis DB104. Two artificial operon systems contained 30 bp or 5 bp gap between the termination codon of the upstream gene and the SD sequence of the downstream gene, respectively. These operon systems were expressed well in B. subtilis and overproduced the -glucosidase cell extract as well as the endoglucanase supernatant. The level of expression in the operon system was almost the same as that in a single expression system.  相似文献   

10.
Summary Six sterols were extracted from lipids produced by Candida curvata yeast. Ergosterol (main component) and five minor compounds: ergosta-7, 24(28)-dien-3 -ol, ergosta-5, 7-dien-3 -ol, ergosta-5, 7, 9, (11), 22-tetraen-3 -ol, ergosta 7, 22-dien-3 -ol, ergost-7-en-3 -ol were identified by gas chromafography/mass spectrometry (GCMS) and quantitated by GLC.  相似文献   

11.
Summary The taste buds of the circumvallate papillae have been examined by electron microscopy in OsO4-fixed, PTA stained material or after KMnO4 fixation. The microvilli of the receptor cells have terminal dilatations which presumably give an increased surface area for transduction. The extracellular spaces at the necks of the receptor cells near the bases of the microvilli are interrupted by closed contacts.The synapses have a well defined synaptic cleft suggesting a chemical rather than an electrical mode of transmission. Synaptic membrane specialisations differ from the membrane thickenings of other types of synapse. Presynaptic dense projections are present but there is no well define postsynaptic thickening. Vesicles occur in both pre- and postsynaptic components, but it is debatable whether or not they should be termed synaptic vesicles. Acknowledgements. We are indebted to Professor J. Z. Young, F. R. S., for his stimulating support, and to Mr. S. Waterman for skilled photography.  相似文献   

12.
Summary The occurrence of the AT chain (i.e. A75 Ile Thr) in different populations was evaluated through a study of 4250 cord blood samples and blood samples from more than 350 SS1 patients. High frequencies were observed in Italy, Yugoslavia, Turkey, Holland, but also in Japan, Vietnam, and India. The chain is (nearly) absent in the Black population of Ghana and Kenya, and low frequencies were observed in China and Australian aborigines. Only a few adult SS patients (18 out of 357) were AT heterozygotes. The chromosomes with the AT globin gene were mapped through an evaluation of the presence of 10 different restriction sites. The AT chromosomes from different populations were closely related and had the same subhaplotypes of [--++-+] (Hinc II 5 to ; Xmn I 5 to G; Hind III in G and A; Hinc II in and 3 to ), quite different from the subhaplotypes seen for AT negative chromosomes.2 This suggests a common ancestor which may have originated in Southern Europe. An evaluation of the chain production by both chromosomes in SS patients and -thalassemia heterozygotes was possible for subjects with an AT heterozygosity. It was concluded that in -thalassemia trait, the chain synthesis is directed for about two-thirds by the thalassemic chromosome and for about onethird by the normal chromosome; the contribution by the normal chromosome decreases with a decrease in total chain production.This is contribution #0890 of the Department of Cell and Molecular Biology, Medical College of Georgia, Augusta, GA 30912, USA  相似文献   

13.
Intragenic polymorphism of the human insulin gene (INS) was investigated in Korean subjects. The 1.9 kb INS sequence, including the 5 to 3 flanking regions, was amplified using the polymerase chain reaction (PCR), and analyzed by direct sequencing. All nucleotide sequences in the coding regions were the same as INS sequences previously reported, and four nucleotides, at positions +216, +1045, +1367, and +1380 in the non-coding regions, were found to be polymorphic. In addition to the previously identified polymorphic alleles l (A-C-C-C) and 1 (T-G-T-A), new nucleotide arrangements were also identified and designated 4 (A-C-C-A), 5 (A-G-C-C), 6 (A-C-T-C), and 2 (T-C-C-C). It was concluded that the new alleles may originate by intragenic recombination within INS during chromosomal crossing-over between the 1 and 1 alleles. The allele 1 was the predominant form in our sample; the new variant alleles, as well as allele 1, appeared to be much less frequent in INSs genes of the Korean subjects studied. Furthermore, the new alleles were detected only in heterozygous form. These results suggest that intragenic recombination can account for allelic divergence in INS.  相似文献   

14.
The production of erythritol and the erythritol yield from glucose by Torula sp. were improved, in increasing order, by supplementing with 10 mg MnSO44H2O l–1, 2 mg CuSO45H2O l–1, and both 10 mg MnSO44H2O l–1 and 2 mg CuSO45H2O l–1. Mn2+ decreased the intracellular concentration of erythritol, whereas Cu2+ increased the activity of erythrose reductase in cells. These results suggest that Mn2+ altered the permeability of cells, whereas Cu2+ increased the activity of erythrose reductase in cells.  相似文献   

15.
Summary On t.l.c. plates 125I-cholera toxin binds to a disialoganglioside tentatively identified as GDlb with about 10 times less capacity than to ganglioside GM1. Binding of labeled toxin to both gangliosides was abolished in presence of excess amounts of unlabeled B subunit. Ganglioside extracts from human or pig intestinal mucosa showed toxin binding to gangliosides GM1 and GD1b. In ganglioside-containing lipid monolayers the penetration of the toxin was independent of the ganglioside binding capacity.Abbreviations GM2 Gal-NAc14Gal(3-2NeuAc)14G1c1Cer - GM1 Gal3Ga1-NAc14Gal(32NeuAc)14G1c11Cer - GD1a NeuAc23Ga113Gal-NAc14Gal(32NeuAc)14G1c11Cer - GD1b Gall3Gal-NAcl4Gal(32NeuAc82NeuAc)14Glc11Cer - GT1b NeuAc23Ga113Ga1-NAcal4Gal(3-2NeuAc82NeuAc)14G1c11Cer - dpPC 1,2-hexadecanoyl-sn-glycero-3-phosphocholine - dpPE 1,2-hexadecanoyl-sn-glycero-3-phosphoethanolamine  相似文献   

16.
Résumé Nous avons fait élever des larves d'Anergates atratulus par des ouvrières deMyrmica laevinodis à 22°C. Pour y parvenir, il n'est pas utile de faire hivernerensemble les larves d'Anergates et les ouvrières deMyrmica. La présence de larves autochtones n'empêche pas lesMyrmica d'élever des larves d'Anergates. Dans toutes les expériences lesMyrmica ont été soumises au fridavant de recevoir des larves d'Anergates. Aucune reine deMyrmica n'a été utilisée dans ces expériences.Sur les 64 larves d'Anergates que nous avons utilisées, 38 se sont transformées en imagos. C'est au début de l'adoption et au moment des métamorphoses que périrent la plupart des 26Anergates perdus. Les femelles vécurent en général 2 ou 3 jours et cherchèrent très tôt à quitter le nid natal. Les mâles vécurent 2 à 3 semaines.
Summary Larvae ofAnergates atratulus were experimentally reared by workers ofMyrmica laevinodis, at 22°C. An overwintering of both larvae ofAnergates and workers ofMyrmica is not necessary for the success of that experiment. The presence of larvae ofMyrmica does not keep theMyrmica from rearing larvae ofAnergates. The workers ofMyrmica have been cooled, in all the experiments, before receiving larvae ofAnergates. No queen ofMyrmica have been used in that experiments.38 of the 64 larvae ofAnergates used became imagos. Most of the 26 lostAnergates died at the beginning of the adoption and during the metamorphosis. The females lived generally 2 or 3 days and tried, very early, to leave their native nest. The males lived 2 or 3 weeks.

Anergates atratulus Myrmica laevinodis, 22 . bmecme Anergates Myrmica. Myrmica Anergates. Myrmica Anergates. Myrmica . 64 Anergates , 38 . 26 Anergates 2 3 . 2 3 .
  相似文献   

17.
Treatment of 18-glycyrrhizic acid with a methanolic solution of HCl resulted in 1 : 1 mixture of methyl esters of 18- and 18-glycyrrhetinic acids. Benzoylation of the mixture led to methyl esters of 3-benzoyl-18-glycyrrhetinic acid and 3-benzoyl-18-glycyrrhetinic acid, which were separated by chromatography on silica gel. 18-Glycyrrhetinic acid was prepared by alkaline hydrolysis of methyl 3-benzoyl-18-glycyrrhetinate and was further used for the syntheses of 3-keto-18-glycyrrhetinic acid and methyl esters of 18-glycyrrhetinic acid and 3-keto-18-glycyrrhetinic acid.  相似文献   

18.
Development of an L6 myoblast in vitro model of moniliformin toxicosis   总被引:1,自引:0,他引:1  
L6 myoblasts were used as an in vitro model to investigate the role of moniliformin and its interaction with monensin in turkey knockdown syndrome and sudden death syndromes in poultry. Cell viability and microscopic and ultrastructural alterations noted in L6 myoblasts cultured in the presence of moniliformin (0.0–0.3 g/l) were compared to those observed in parallel cultures also containing one of the following compounds: selenium (0–0.004 ng/l), thiamine (0–0.3 g/l), or pyruvate (0–0.46 g/l). Marked dilation of the RER, membranous whorls, glycogen deposition, membrane-bound cytoplasmic inclusions and necrosis were observed in myoblasts exposed to 0.03/2-0.30 g moniliformin/l medium. Supplementation of medium with thiamine and pyruvate, or selenium, provided significant protection to cells exposed to 0.0–0.3 g/l or 0.0–0.15 g moniliformin/l, respectively. Dose-dependent differences in protein and ATP production were not detected. Myoblasts grown in medium containing 0–0.15 g moniliformin/l and 7.5–50.0 M A23187, beauvericin or monensin had degrees of cytotoxicity similar to parallel cultures receiving only an ionophore. L6 myoblasts were a useful model of moniliformin toxicosis. The findings of this study suggest cytotoxicity due to moniliformin in L6 myoblasts may be due in part to oxidative damage and altered pyruvate metabolism, and that moniliformin does not predispose myoblasts to ionophore toxicosis. This study supports the results of in vivo investigations in poultry that moniliformin and monensin do not act synergistically to induce knockdown or monensin toxicosis.  相似文献   

19.
Summary A sensitive photometric method is described by which the dichroism of lipid bilayer membranes in aqueous phase can be measured. The method is applied to black films with incorporated chlorophylla andb. With chlorophylla a relatively large dichroism is found in the Soret band and a much weaker dichroism in the red band. From the experimental data, the angles B and R between the blue and red transition moments and the membrane can be obtained. B and R are then used to calculate the angle of the porphyrin ring with respect to the membrane surface. For chlorophylla and three different lipids, values of between 44 and 49° are found.  相似文献   

20.
Unlike most marine teleosts, the coral reef-dwelling spiny damsel, Acanthochromis polyacanthus, lacks a pelagic larva dispersal phase and represents one of few examples of self recruitment onto a natal reef by a marine teleost immediately after hatching. Benthic eggs are protected by the parents, and upon hatching the young remain under parental care for several months. Visual morphogenesis of spiny damsel embryos and juveniles was examined to evaluate the potential visual capabilities of the young after emergence onto the reef. The optic primordia were visible in the embryo as hollow spheres of undifferentiated neuroblasts 2 days after fertilization (daf). Visual morphogenesis proceeded rapidly thereafter in the embryo such that at hatching (between 10 and 12daf) gross visual morphology was consistent with that reported in the majority of juvenile marine teleosts, reflecting direct development of the retina of the spiny damsel within the egg. At hatching, the outer nuclear layer comprised 2 classes of photoreceptors; cones and rods. Tangential sections of the retina revealed a square cone mosaic in which 4 double cones surrounded a single cone. This arrangement remained unchanged in all later life history intervals examined. Absolute eye size was large compared to larvae of marine pelagic spawners. Eye and lens diameters increased from 0.69 and 0.23mm, respectively, on the day of hatching (12daf), to 3.77 and 1.52mm, respectively, in a fish 131daf. Angular density of cones increased from 0.25 cones 10 visual arc–1 in an embryo 8daf, to 1.14 cones 10 visual arc–1 in a fish 131daf, demonstrating the potential for significant increase in spatial resolution with increasing eye size. Convergence ratios of cones to ganglion cells remained relatively constant from the time of hatching, suggesting that the determinate ganglion cell photopic receptive field was established early in development. The increase in the convergence ratios of rods: ganglion cells from 1.4 in the late stages of embryogenesis (10daf; 2 days prior to hatching) to 4.9 in a fish 103daf, demonstrated increasing scotopic ganglion cell receptive field size, with increasing age. This was a result of rod cell addition with growth. An increase in the angular density of rods from 0.18 rods 10 visual arc–1 in an embryo 8daf, to 4.07 rods 10 visual arc–1 in a fish 131daf, and the increase in mean scotopic light path-length from 13.3±1.1m in an embryo 8dpf, to 55±5.2m a fish 22dpf, collectively indicate the potential for increasing scotopic sensitivity during growth. On the basis of visual morphology it is predicted that newly hatched spiny damsel juveniles have substantially greater visual capabilities than first feeding larvae with a pelagic dispersal phase. In addition, we propose that the developmental trajectory of the spiny damsel is different from that of pelagic dispersing larvae and does not simply reflect displacement along a common developmental continuum by an extended embryonic duration.  相似文献   

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