Spontaneous chlorophyll mutants of Pennisetum americanum: Genetics and chlorophyll quantities

Summary Thirteen spontaneously occurring chlorophyll deficient phenotypes have been described and their genetic basis was established. Ten of these — white, white tipped green, patchy white, white virescent, white striping 1, white striping 2, white striping 4, fine striping, chlorina and yellow virescent showed monogenic recessive inheritance and the remaining three — yellow striping, yellow green and light green seedling phenotypes showed digenic recessive inheritance. The genes for (i) white tipped green (wr) and yellow virescent (yv) and (ii) patchy white (pw) and white striping 1 (wst 1) showed independent assortment. Further, the genes for white (w), white tipped green (wr) and yellow virescent (yv) were inherited independently of the gene for hairy leaf margin (Hm).In the mutants — white tipped green, patchy white, white striping 1, white striping 2, fine striping, chlorina, yellow virescent, yellow striping, yellow green and light green phenotypes total quantity of chlorophyll was significantly less than that in the corresponding controls, while in white virescent there was no reduction in the mature stage. For nine of the mutants the quantity of chlorophyll was also estimated in F₁'s (mutant x control green). In F₁'s of six of the mutants — white tip, patchy white, chlorina, yellow virescent, fine striping and yellow striping the quantity of chlorophyll was almost equal to the wild type. In the F₁'s of three of the mutants — white striping 1, white striping 2 and light green an intermediate value between the mutant and wild types was observed. In yellow virescent retarded synthesis of chlorophyll, particularly chlorophyll a was observed in the juvenile stage. Reduced quantity of chlorophyll was associated with defective chloroplasts. In the mutants — white tipped green, white virescent, fine striping, chlorina, yellow striping, yellow green and light green defective plastids were also observed. In patchy white secondary destruction of chlorophylls and the presence of defective plastids were found to be associated with reduced chlorophyll quantity at maturity.Paper chromatographic studies of leaf flavonoids revealed some variation between the inbreds, but there were three common spots, 7, 8 and 9, except for PDP in which the spot 8 was absent. Chlorophyll deficient mutants differed from their respective controls in the absence of one or more of the spots present in the controls and in the presence of new spots in some of the mutants.Most of the chlorophyll mutants showed higher survival rate in the Kharif season than in Rabi season which was attributed to the higher mean day temperature and longer day light period in the Kharif season than in Rabi season.     

Triggering and predisposing factors in the “Red” decline syndrome of Norway spruce (Picea abies)

Summary Analysis of 62 mature Norway spruce (Picea abies provenance Viborg) trees growing in a Danish plantation was undertaken along with analysis of their nutrient contents (N, P, K, Ca, Mg, Fe, Mn, Cu, Zn, B and Na), in each of the three youngest needle age classes, from branches of four exposure directions near the tree top. The aim was to investigate if one among the studied possible predisposing factors was also a triggering factor in the 1989 outbreak of the Red Norway spruce decline in Denmark. Neither nutrient imbalance or deficiency, nor excessive N-deposition or salt-stress were indicated as triggering factors in 1989. The Red syndrome, noticeable for the bright red colour of the current-year needles, was found to be an extension of the European type Novel Decline. Red syndrome is similar to previously reported phenomena of top-dying and sub top-dying, in that it had fewer needle age classes and significantly higher contents of mobile cations (and Ca) in the younger needle classes. Tree ring analysis suggested that the Red syndrome was initiated in the early 1980s, when the trees experienced adverse climatic conditions. Because of this long-term development of the Red Norway spruce decline syndrome, it is concluded that a triggering factor is of minor importance relative to the multitude of predisposing factors.     

Transformation of yeast and Podospora: innocuity of senescence-specific DNAs

Summary Two senscence-specific DNAs (sen-DNAs and ) were tested for their ability to drive autonomous replication in yeast and Podospora. The but not the sequence has autoreplicative (ARS) properties in yeast; the ARS sequences of are not included in the region common to all the sen-DNAs. Neither the nor the sequences can confer autoreplicative properties in Podospora. These sequences inserted into a hybrid vector carrying the suppressor tRNA, su4-1, do not change the mode of transformation of a suppressible leu-1-1 strain of Podospora: the transformation is by integration whether or not the plasmid carries a sen-DNA sequence. The su4-1 gene integrates at its homologous site in a minority of cases. It is possible to reisolate free plasmids at a low frequency from some transformants. The presence of a sen-DNA on the transforming vector has no effect upon the longevity of the transformants.     

Cloning and characterization of the Escherichia coli chromosomal region surrounding the dnaG gene, with a correlated physical and genetic map of dnaG generated via transposon Tn5 mutagenesis

Summary A 24 kilobase pair region of the E. coli chromosome surrounding the dnaG gene has been cloned and characterized. A phage library was first constructed by ligating a Sau3A (GATC) partial DNA digest of the entire E. coli chromosome into the BamHI (G GATCC) cloning vector charon 28. Partial digestion was performed to generate overlapping chromosomal fragments and to allow one to walk along the chromosome. This library was probed with a nick-translated plasmid (pRRB1) containing the rpoD gene, which maps adjacent to dnaG at 66 min. Four bacteriophages: 3, 4, 5, 6 that hybridized to the probe were isolated from the 2,500 plaques screened. One phage recombinant 4, was shown to contain the dnaG gene. Three recombinant plasmids containing dnaG: pGL444, pGL445, pBS105, were constructed via subcloning of 4 using different restriction fragments. Plasmids pGL444 and pBS105 were subjected to transposon Tn5 mutagenesis and 88 Tn5 inserts into the cloned region were isolated. The location of the Tn5 inserts were mapped by restriction enzyme analysis of the plasmids and the insertion mutations were checked for ability to complement a dnaGts chromosomal marker at nonpermissive 40° C. In this manner a correlated physical and genetic map of dnaG was determined. A large number of Tn5 inserts map to a specific 900 b.p. region which we propose may be involved in the regulation of dnaG gene expression.     

Differential Expression and Association of Calcium Channel Subunits in Development and Disease

Voltage-gated calcium channels (VDCC) are essential to neuronal maturation and differentiation. It is believed that important signaling information is encoded by VDCC-mediated calcium influx that has both spatial and temporal components. VDCC are multimeric complexes comprised of a pore-forming ₁ subunit and auxiliary and ₂/ subunits. Changes in the fractional contribution of distinct calcium conductances to the total calcium current have been noted in developing and differentiating neurons. These changes are anticipated to reflect the differential expression and localization of the pore-forming ₁ subunits. However, as in vitro studies have established that regulates the channel properties and targeting of ₁, attention has been directed toward the developmental expression and assembly of isoforms. Recently, changes in the component of the omega-conotoxin GVIA (CTX)-sensitive N-type VDCC have indicated differential assembly of _1B with in postnatal rat brain. In addition, unique properties of 4 have been noted with respect to its temporal pattern of expression and incorporation into N-type VDCC complexes. Therefore, the expression and assembly of specific ₁/ complexes may reflect an elaborate cellular strategy for regulating VDCC diversity. The importance of these developmental findings is bolstered by a recent study which identified mutations in the 4 as the molecular defect in the mutant epileptic mouse (lethargic; lh/lh). As 4 is normally expressed in both forebrain and cerebellum, one may consider the impact of the loss of 4 upon VDCC assembly and activity. The importance of the lb and 4 isoforms to calcium channel maturation and assembly is discussed.     

DNA sequences homologous to the T DNA region of Agrobacterium tumefaciens are present in diverse Rhizobium species

Summary DNA sequences homologous to the T DNA region of the octopine-type Ti plasmid from Agrobacterium tumefaciens are present in different Rhizobium species. Plasmid DNA from each of two R. leguminosarum, two R. meliloti, and four slow-growing Rhizobium strains examined contain restriction endonuclease fragments that hybridize with the T DNA region, or with DNA sequences at or near the adjacent Ti plasmid transfer (ra) region. Four different BamHI fragments that contain homology to the T DNA region were cloned from R. leguminosarum 300 plasmid DNA. Cloned fragments of 5.9 kb and 10.3 kb hybridize to each other and are homologous to sequences which map at the right boundary region (EcoRI fragment 24) of the core T DNA. Ti plasmid sequences homologous to those present in cloned fragments of 10.9 kb and 2.0 kb map in adjacent fragments near the tra genes, approximately 10 kb to the right of the core T DNA.     

Nature of the plasmid-linked penicillinase regulatory region in Staphylococcus aureus

Summary Four noninducible staphylococcal penicillinase plasmids reported to produce a very low basal level of penicillinase were investigated. Incorporation of 5-methyltryptophan, which is known to inactivate the operator binding site of wild-type penicillinase repressor and thereby elicit penicillinase synthesis, did not induce penicillinase synthesis in any of these micro mutants. Therefore, these plasmids are not simply peni ^S mutants. Heterodiploid strains composed of a plasmid fully constitutive for penicillinase synthesis and one of the various micro penicillinase plasmids were constructed. Three of these heterodiploids produce a normal basal level of penicillinase and are inducible by 5-methyltryptophan but not by the standard gratuitous penicillinase inducer. Therefore, each of these three noninducible micro plasmids produces a peni ^S repressor, but in addition, each must bear a mutation in the penZ region. The fourth heterodiploid produces a fully constitutive level of penicillinase. The noninducible micro plasmid present in this heterodiploid must contain a penI ^– mutation and a mutation in the penZ region. Consequently, each of these four noninducible micro plasmids contains at least two mutants genes. Hence, the phenotype of noninducibility plus low basal penicillinase is not due to a point mutation in a second penicillinase regulatory region as has been proposed. Instead, these results strongly suggest that there is only one penicillinase regulatory gene located on the penicillinase plasmid and that this gene (penI) specifies the penicillinase repressor.Journal Paper No. J-8700 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa; Project No. 2029     

Quantitative comparisons between the karyotypes of Australian marsupials from three different superfamilies

Relative DNA values and percent lengths of chromosome arms have been studied for six species of the super-family Dasyuroidea, five species of Phalangeroidea and four species of Perameloidea. By multiplying by relative DNA values all percent lengths have been expressed in the same units. Two species are said to share a chromosome if neither of the arms differs at the 5% level of probability. It is argued that if species share at least two two-armed chromosomes, this can be taken as evidence of relationship. A standard dasyurid karyotype has been defined and individual species of Dasyuridae show only small deviations from it. The nature and significance of the bi-modal distribution of chromosome numbers in marsupials is discussed.     

Filamentous Marine Fungi as Producers of <Emphasis Type="Italic">O</Emphasis>-Glycosylhydrolases: β-1,3-Glucanase from <Emphasis Type="Italic">Chaetomium indicum</Emphasis>

Ninety fungal strains (42 species) isolated from marine habitats were studied for their ability to produce extracellular enzymes. Cultural filtrates of these strains were shown to contain a series of glycosidases (-glucosidases, N-acetyl--glucosaminidases, -galactosidases -mannosidases) and glucanases (1,3--glucanases, amylases) which varied with habitat. The level of activity depended on the species of fungi. Several promising strains capable of producing both individual enzymes and a set of enzymes for splitting carbohydrate-containing compound have been isolated. Optimal conditions for growth of Chaetomium indicum and for biosynthesis of -1,3-glucanase were determined. -1,3-Glucanase was isolated using ion-exchange chromatography, ultrafiltration, and gel filtration. The presence of 2 enzyme forms was shown; both forms were exo--1,3-glucanases.     

Partial purification and properties of γ-glutamyltranspeptidase from mycelia of Morchella esculenta

Three -glutamyltranspeptidase (enzymes I, II and III) were partially purified from the cell free extracts of the cultured mycelia of Morchella esculenta Fr. The molecular masses of enzymes were 155,000 (I), 219,000 (II) and 102,000 (III). All of them catalyzed both hydrolysis and transpeptidation of various -glutamyl compounds. -l-Glutamyl-cis-3-amino-l-proline occurring in the cultured mycelia of this fungus was a good substrate for both reactions. K _m values for hydrolysis were in the order of 10^-4 to 10^-5 M, and those for transpeptidation were in the order of 10^-2 to 10^-4 M. The enzymes were inhibited by a -glutamyltranspeptidase inhibitor, l-serine plus borate.Abbreviations -GTP -glutamyltranspeptidase - HPLC High-performance liquid chromatography     

Ultrastructural localization of corticotropin, β-lipotropin,and αand β-endorphin in the porcine anterior pituitary

Summary The peroxidase-antiperoxidase immunocytochemical technique was used to identify the ACTH/endorphin cells in the porcine pituitary at the ultrastructural level and to determine the precise subcellular localization of the pro-ACTH/endorphin fragments. The cells display different aspects: 1) large, regular shapes with numerous and large secretory granules; 2) small, irregular and angular shapes with small granules aligned along the periphery of the cell; and 3) intermediate forms. The presence of and -endorphin not only in the same cells but also in the same secretory granules that contain ACTH and -LPH clearly indicates that both the precursor or its fragments and the abovementioned peptides are stored in the same granules and released simultaneously by the corticotropic cells. The presence of FSH in some corticotropic cells is also discussed.Abbreviations used in this Article ACTH corticotropin - -MSH -melanotropin (ACTH I–I3) - CLIP corticotropin-like intermediate lobe peptide (ACTH 18–39) - -LPH -lipotropin - -MSH -melanotropin (-LPH 41–58); -endorphin (-LPH 61–91); -endorphin (-LPH 61–76)     

β-Glucosidase excretion by Trichoderma pseudokoningii: Correlation with cell wall bound β-1.3-glucanase activities

The formation and excretion of -glucosidase from Trichoderma pseudokoningii was studied during growth on different carbon sources. The enzyme was present under all conditions examined, but increased activity was found during growth on carbon sources favouring slow growth.Two different patterns of -glucosidase excretion were observed: on carbon sources allowing fast growth a relatively high percentage of total activity was found in the culture fluid, which decreases as the culture grows older, but which increases again during the phase of cell lysis; on carbon sources favouring slow growth, excretion is initially low, but commences at later culture stages.Changes in cell wall composition and cell wall lytic enzyme activities associated with the cell walls were examined during phases of high and low ratios of extracellular to cell-wall bound -glucosidase activities. With no component of the cell wall (chitin, -glucan, -glucan, galactosamine) could correlation with -glucosidase excretion be identified. Among a number of cell-wall lytic, cell-wall associated enzymes (-glucanases, -glucanases, glucosaminidase, galactosaminidase), -1.3-glucanase activity correlated well with the excretion of -glucosidase.The results suggest a possible role of -1.3-glucanases in the mechanism of release of -glucosidase from cell walls of T. pseudokoningii; this is discussed.     

Restriction endonuclease analysis of ribosomal DNA from Saccharomyces cerevisiae

Summary Temperature-sensitive mutants of Escherichia coli that are unable to grow at high temperature can be obtained among those selected for resistance to streptovaricin or rifampicin at low temperature (Yura et al., 1970). One of these mutants (KY5323) that was supposed to carry a single mutation affecting both rifampicin resistance and temperature sensitivity was further investigated. Using purified RNA polymerase preparations obtained from the mutant and the wild type, it was found that the activity for DNA chain elongation is more sensitive to heat treatment than that for RNA chain initiation or DNA binding, and that the mutant enzyme is significantly more labile than the wild-type enzyme with respect to RNA chain elongation, when heat treatment is carried out at high salt concentration. These results, taken together with those of the enzyme reconstitution experiments, strongly suggest that the subunit of the polymerase is directly involved in both RNA chain initiation and elongation reactions. Enzyme reconstitution experiments using isolated subunits derived from the mutant and the wild-type polymerases demonstrate that the alteration of subunit is primarily responsible for both rifampicin resistance and thermolability of the mutant enzyme. In addition, the results suggested the apparent alteration of both and subunits in this mutant. Extensive transduction experiments provided genetic evidence that are consistent with the view that the strain KY5323 carries a second mutation affecting the subunit, beside the primary mutation affecting the subunit. The hypothetical subunit mutation seems to modify quantitatively the rifampicin resistance caused by the subunit mutation.     

Beobachtungen zu Biologie und Verhalten des Gro?en Kragenlaubenvogels (Chlamydera nuchalis)

Zusammenfassung Von Mai bis Juli 1969 wurde im Gebiet von Darwin und Arnhemland (Northern Territory, Australien) Biologie und Verhalten vonChlamydera nuchalis studiert.28 Lauben wurden gefunden. Einzelheiten des Laubenbaues und der hierzu verwendeten Materialien werden beschrieben. Das muß etwa 4–5000 Zweige zum Laubenplatz schaffen; die Wände der Laube bestehen aus etwa 1400 bis 1840 Zweigen.Die zur Ausschmückung der Laube verwendeten Gegenstände umfaßten Molluskenschalen, Knochen, Glasstückchen, Steine und kleine glänzende Metallobjekte. Das Gesamtgewicht des Laubenschmuckes betrug 6,6 bis 12,1 kg. Größe und Gewicht der Einzelobjekte schwankten zwischen 4–10 mm und 0,2–1,2 g bzw. 73 × 36 mm und 40 g. Ihre Gesamtzahl liegt zwischen 5000 und 12 000. Bevorzugt werden weiße und graue Objekte; auch grüne Glasstückchen wurden gefunden.Die Technik des Laubenbaus, die ausschließlich das ausführt, wird beschrieben. Der Rohbau nimmt etwa 3 Wochen in Anspruch, doch werden im Anschluß daran dauernd neue Objekte eingetragen. Anzeichen für das Ausmalen der Laube wurden nicht gefunden. Während der Balz singt das intensiv auf Bäumen oder am Boden. Die einzelnen Balzphasen werden beschrieben. Während des Höhepunktes versucht das durch Sprünge im Kreis das an der Laube zu halten. Begattung wurde außerhalb der Laube nahe dem Ausgang beobachtet. Offensichtlich hat ein mehrere während einer Balzperiode. Während der Balz wird die Laube dauernd ausgebessert und ihr Schmuck neu arrangiert.

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On the biology and behaviour of the Great Grey Bower Bird(Chlamydera nuchalis)

Summary From May to July, 1969 the author observed in the region of Darwin and Arnhem Land (Northern Territory, Australia) the biology and behaviour of the Great Grey Bower Bird.28 bowers were found, in three cases the building process was observed. Bower-building starts with cleaning up an area of 210 to 95 cm and with forming a 7.5 cm thick mat of small twigs intertwined in all directions. The walls are made of uniform twigs the measurements of which are on an average 29.2 mm in length and 2.4 mm in thickness at the lower end. A wall consists of 700 to 920 twigs placed parallel to each other (1400 to 1840 twigs on the two walls). The carries 4000 to 5000 twigs to the site of the bower. The paper gives the measurements of the bower and its orientation towards cardinal points.The bower is completed by a collection of ornaments which consists of land and sea shells of the generaXanthomelon, Venus andTelescopium, bone and glass fragments, stones (almost exclusively quartzite and limestone), and small pieces of glossy metal objects, tin seals etc. The lowest total weight of all objects collected was 6.2 kg, the highest was 12.1 kg. The size and weight of the objects varies between 4 to 10 mm and 0.2 to 1.2 g and 73 by 36 mm and 40 g respectively.Their total number was established at 5000 to 12000.Chlamydera nuchalis prefers white and grey objects with the exception of glass of which also green fragments were found. Some objects were experimentally painted blue, red, black, yellow and green. The discarded them successively and threw them out of the bower.The paper describes the technique of bower-building which is carried out solely by the . It takes the bird three weeks to finish the construction in the rough, but even afterwards the systematically continues to complete the bower, adding a growing number of ornamental objects. During the display period, however, a rebuilt a bower, which had been destroyed, within 2.5 days. The activities observed are shown in the table. Bower Birds may carry, on an average, 90 twigs and 28 glass fragments per hour to the bower. The bower wall painting behaviour ofChlamydera maculata andPtilonorhynchus violacaeus was not observed inChlamydera nuchalis. No traces of painting were found in any of the bowers observed. The author found an interesting behaviour pattern in two who stuck pieces of food into the cracks in the walls. This behaviour strikingly resembles that of passerines feeding their young.During the display period the sings ardently either on trees or on the ground. Display consists of alluring manifestations of the , including nape-crest presentation and bounds. At the bower, the shows the some objects on the opposite side of the passage, and after bowing and raising his head, he turns it so that the nape is directed toward the , and presents to her its lilac crest. During the culminating phase of display the attempts, by circling in leaps, to keep the at the bower. Mating was observed outside the bower, next to its exit. A apparently has several females during the display period. Also during display the rearranges and completes the bower.

     

Characterization of the effectors required for stable inheritance of Streptococcus pyogenes pSM19035-derived plasmids in Bacillus subtilis

The low-copy-number and broad-host-range pSM19035-derived plasmid pBT233 is stably inherited in Bacillus subtilis cells. Two distinct regions, segA and segB, enhance the segregational stability of the plasmid. Both regions function in a replicon-independent manner. The maximization of random plasmid segregation is accomplished by the recombination proficiency of the host or the presence of the pBT233 segA region. The segA region contains two open reading frames (or) [ and ]. Inactivation or deletion of or results in SegA^– plasmids. Better than random segregation requires an active segB region. The segB region contains two ors (or and or). Inactivation of either of the orfs does not lead to an increase in cell death, but or^– plasmids are randomly segregated. These results suggest that pBT233 stabilization relies on a complex system involving resolution of plasmid oligomers (segA) and on the function(s) encoded by the segB region.     

Existence and uniqueness of a sharp travelling wave in degenerate non-linear diffusion Fisher-KPP equations

In this paper we use a dynamical systems approach to prove the existence of a unique critical value c ^* of the speed c for which the degenerate density-dependent diffusion equation u _ct = [D(u)u _x ] _x + g(u) has: 1. no travelling wave solutions for 0 < c < c ^*, 2. a travelling wave solution u(x, t) = (x - c ^* t) of sharp type satisfying (– ) = 1, () = 0 ^*; '(^*–) = – c ^*/D'(0), '(^*+) = 0 and 3. a continuum of travelling wave solutions of monotone decreasing front type for each c > c ^*. These fronts satisfy the boundary conditions (– ) = 1, '(– ) = (+ ) = '(+ ) = 0. We illustrate our analytical results with some numerical solutions.     

Transmission of paternal chloroplasts in Nicotiana

Summary Transmission of paternal chloroplasts was observed in Nicotiana, considered to inherit organelles in a strictly maternal way. Plants carrying streptomycin resistant plastids were used as pollen donors. Cell lines with paternal plastids in the offspring were selected as green (resistant) sectors on calli induced from the seedlings on streptomycin-containing media. The presence of paternal plastids in the regenerated plants was confirmed by restriction analysis. In the Nicotiana plumbaginifolia xN. plumbaginifolia Np(SR1)3 and the N. plumbaginifolia Np(gos)29 xN. tabacum SR1 crosses 2.5% and 0.07% of the offspring were found to contain paternal (tabacum) plastids, respectively. These plants, however, carried maternal mitochondria exclusively. This sexual cybridization method offers a simple way to transfer chloroplasts solely, a goal not accessible by protoplast fusion.     

Average phase difference theory and 1∶1 phase entrainment in interlimb coordination

The dynamics of coupled biological oscillators can be modeled by averaging the effects of coupling over each oscillatory cycle so that the coupling depends on the phase difference between the two oscillators and not on their specific states. Average phase difference theory claims that mode locking phenomena can be predicted by the average effects of the coupling influences. As a starting point for both empirical and theoretical investigations, Rand et al. (1988) have proposed d/dt= — K sin ), with phase-locked solutions =arcsin( /K), where is the difference between the uncoupled frequencies and K is the coupling strength. Phase-locking was evaluated in three experiments using an interlimb coordination paradigm in which a person oscillates hand-held pendulums. was controlled through length differences in the left and right pendulums. The coupled frequency _c was varied by a metronome, and scaled to the eigenfrequency _v of the coupled system K was assumed to vary inversely with _c. The results indicate that: (1) and K contribute multiplicatively to (2) =0 or = regardless of K when =0; (3) 0 or regardless of when K is large (relative to ); (4) results (1) to (3) hold identically for both in phase and antiphase coordination. The results also indicate that the relevant frequency is _c/_v rather than _c. Discussion high-lighted the significance of confirming =arcsin(/K) for more general treatments of phase-locking, such as circle map dynamics, and for the 11 phase-entrainment which characterizes biological movement systems.     

A Cytogenetic Study of the Leaf Beetle Genus Cyrtonus (Coleoptera, Chrysomelidae)

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+Xy_p male meioformula, three have 2n=40 and 19+Xy_p and one 2n=46 and 22+Xy_p. 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.