The growth of Epidermophyton floccosum and E. stockdaleae at different temperatures

The ability of 17 strains of genus Epidermophyton (15 strains belonging to Epidermophyton floccosum, one to E. floccosum var. nigricans and one to E. stockdaleae) to grow at different temperatures (4 °C, 25 °C, 28 °C, 31 °C, 34 °C, 37 °C and 40 °C) was stated.The strains were inoculated on Sabouraud Dextrose Agar and regularly controled over a period of 14 days when the plates were incubated at 25 °C, 28 °C, 31 °C, 34 °C, 37 °C and 40 °C, and over a period of 70 days when the temperature was 4 °C. The optimal growth of E. floccosum was observed at 28 °C and 31 °C, and no signs of growth were recorded neither at 4 °C nor at 40 °C. The optimal development of E. stockdaleae was observed at 25 °C and 28 °C. This species grew from 4 °C to 31 °C.     

Heat-shock DNA homology in distantly related species of Drosophila

Polytene chromosomes of D. melanogaster and D. virilis were hybridized in situ with ¹²⁵I labeled mRNA isolated from polysomes of D. melanogaster tissue culture cells incubated at 37° C. ¹²⁵I mRNA hybridized preferentially with subdivisions 87A and 87Cl of the D. melanogaster 3R chromosome; grains were also observed at regions 93D, 95D and over the chromocenter. A considerable cross hybridization of this mRNA with D. virilis polytene chromosomes was observed. The 29C region of the D. virilis second chromosome was the main site of hybridization. Significant grain numbers also appeared in region 20F of the same chromosome. The two regions mentioned belong to heat shock loci in the latter species. Based on label intensity we conclude that region 29C of D. virilis contains DNA sequences retaining molecular homology with those at subdivisions 87A and 87Cl of D. melanogaster. SDS-polyacrylamide gel electrophoresis revealed similar distributions of heat shock proteins in the two species studied.     

Morphology of the pachytene chromosomes ofPennisetum purpureum schumach

The morphology of the pachytene chromosomes ofPennisetum purpureum was studied. On the basis of relative lengths and arm ratios it was possible to identify them individually. They are numbered 1 to 14 in the order of their decreasing lengths and diagnostic characters are given for each chromosome. The first and the fourteenth chromosomes, the longest and the shortest of the complement respectively, are the nucleolus organizing chromosome. In all the fourteen chromosomes the centromeres are flanked by deep staining regions. This feature is common to the two species.P. typhoides andP. purpureum. Seven out of the fourteen chromosomes have terminal knobs in their long arms. This is a feature in which it differs from the other seven chromosome species.Pennisetum typhoides. These knobs, however, are not present uniformly in all populations; material obtained from Ghana did not show these knobs.     

In situ hybridization of ribosomal DNA labelled with 125iodine to metaphase and lampbrush chromosomes from newts

Methods are described for in situ hybridization of ribosomal DNA from Xenopus laevis, labelled in vitro with ¹²⁵iodine, to mitotic and lampbrush chromosomes from Triturus cristatus carnifex. The hybridization reaction was carried out in a mixture containing 50% formamide, 4 x SSC, 0.1 M KI, at 37° C, or in 2 x SSC, 0.1 M KI at 65° C. Autoradiographs of mitotic metaphases from 2 males showed labelling over the middle of the short arm of one chromosome IX in each metaphase. In some cases, a region near the end of a longer chromosome was also labelled. In lampbrush preparations, labelling was confined to a region identified as about 53 units, near the middle of the short arm of both halves of bivalent IX. The usefulness of the technique and the significance of the labelling of only 1 of the 2 chromosomes IX in mitotic preparations are discussed.     

Inferred chromosome morphology of the ancestral genome ofTriticum

The lengths of the A, B, and D genomes of common wheat,Triticum aestivum, were measured from the karyotype. Relative to the B genome, standardized as length 1.000, the lengths of the A and D genomes were 0.835 and 0.722, respectively. The lengths of the chromosome arms in the A and D genomes were then multiplied by the appropriate constants so that the total lengths of each genome also equalled 1.000. These calculations revealed that homoeologous chromosomes in wheat, with a few exceptions, have similar sizes and arm ratios. The arm lengths of the three homoeologues in each homoeologous group were then averaged. These average chromosomes turned out to be remarkably similar, in size and arm ratio, to their homoeologues in the E genome ofElytrigia elongata. This evidence and data on cross-compatibility and morphological characteristics suggested that the genusTriticum is a result of adaptive radiation from the perennial genusElytrigia, specifically from the complex of species possessing the E genome or one closely related to it.     

Chromosome delineation induced by a combined potassium permanganate-sodium bisulfite treatment

A cytological procedure for in vitro chromosome delineation has been studied using human and mouse (Mus musculus) chromosomes. This method, consisting of slide incubation in KMnO₄ at 0–5° C for 24 h followed by a short exposure to NaHSO₃ (1–3 min) and Giemsa staining, induces extraction of chromatin from human and mouse interphase nuclei and chromosomes. Autoradiography after ³H-ThD incorporation in vitro and cytophotometry confirmed that DNA is removed. Well contour-delineated and non-distorted chromosomes are observed in both species allowing the identification of all human chromosome groups. Contour chromosome delineation and its relationship to chromosome organization is briefly discussed.     

Comparative skeletogenesis of the Oriental Tree Frog Hyla orientalis (Anura: Hylidae)

The ontogeny of skeletal development of the Oriental Tree Frog, Hyla orientalis (Bedriaga, 1890), is followed from tadpole to froglet and compared with four other hylid species i.e., Hypsiboas lanciformis, Hypsiboas pulchellus, Phyllomedusa vaillanti and Pseudis platensis. Our analysis and comparison is based on cleared and double-stained specimens. The parasphenoid is the first skeletal element that ossified in Hyla orientalis is followed by the exoocipital, prootic, axial and appendicular skeletal elements, frontoparietal, nasal, upper jaw, squamosal, pterygoid, lower jaw, vomer and quadratojugal. Ossification initiated at early Stage 33 in Hyla orientalis whereas in other hylids it begins after Stage 37. Major transformations of the larval jaw were visible after Stage 42. Cranial ossifications were completed after appendicular and axial ossifications of Hyla orientalis. All skeletal elements ossified before the end of the metamorphosis, a unique feature of Hyla orientalis in comparison to the other hylids studied here.     

Heat-shock phenomena in Chironomus tentans

Isolated salivary glands of fourth instar larvae of Chironomus tentans were incubated at different above-normal temperatures for various lengths of time. Size changes in Balbiani ring 2 (BR2) and in the heat-inducible chromosome region IV-5C were quantified. These chromosome regions behaved in vitro very much the same as in vivo: BR2 was repressed rapidly by heat shock (37° C), whereas under overheat-shock conditions (42° C) it stayed decondensed. Region IV-5C showed the opposite responses. After a return from heat shock to normal temperatures the puffing pattern recovered. This process depended strictly on the integrity of the gland and on a change of medium. In injured glands a recovery process occurring under heat-shock conditions was discovered.     

Molecular cytogenetic study of three common Mediterranean limpets, Patella caerulea, P. rustica and P. ulyssiponensis (Archaeogastropoda, Mollusca)

The present paper shows the results of chromosome banding and rDNA-FISH study performed on several specimens of different populations of Patella caerulea, Patella rustica and Patella ulyssiponensis. The taxonomic attribution of specimens was ascertained by the molecular phylogenetic analysis of the mitochondrial 16S rRNA gene. P. caerulea and P. rustica had 2n = 18 chromosomes with first seven of biarmed pairs and the remaining two uniarmed pairs. P. ulyssiponensis had 2n = 16 with all biarmed chromosomes. Ag-NOR loci were on the short arms of the first metacentric pair in the three studied limpets, whereas they showed a different pattern of heterochromatin distribution and composition. A chromosome mosaicism was observed in several P. caerulea specimens, which exhibited an unpaired metacentric element and loss of a telocentric pair. The obtained results suggest that in the genus Patella specific diversification was accompanied by variations in heterochromatin distribution and composition and reduction of chromosome number by Robertsonian centric fusion.     

Patterns of replication in the neo-sex chromosomes ofDrosophila nasuta albomicans

Drosophila nasuta albomicans (with 2n = 6), contains a pair of metacentric neo-sex chromosomes. Phylogenetically these are products of centric fusion between ancestral sex (X, Y) chromosomes and an autosome (chromosome 3). The polytene chromosome complement of males with a neo-X- and neo-Y-chromosomes has revealed asynchrony in replication between the two arms of the neo-sex chromosomes. The arm which represents the ancestral X-chromosome is faster replicating than the arm which represents ancestral autosome. The latter arm of the neo-sex chromosome is synchronous with other autosomes of the complement. We conclude that one arm of the neo-X/Y is still mimicking the features of an autosome while the other arm has the features of a classical X/Y-chromosome. This X-autosome translocation differs from the other evolutionary X-autosome translocations known in certain species ofDrosophila.     

Speciation via hybrid dysgenesis: negative evidence from the Drosophila affinis subgroup

Differences in karyotypic structure are compared with reported isozyme differences in three Mediterranean species of Patella. In addition, the karyotypic structure of Patella is discussed in terms of the karyotypic variability of Archaeogastropoda. Both P. lusitanica and P. caerulea have a haploid complement of n=9 (6 metacentric, 1 submetacentric, 1 subtelocentric, 1 telocentric chromosome in P. lusitanica and 6 metacentric, 1 submetacentric, 2 telocentric chromosome in P. caerulea). P. aspera, although regarded as morphologically more closely related to P. caerulea, has a haploid complement of only n=8 (7 metacentric and 1 submetacentric chromosomes).     

Dynamic organization of the β-heterochromatin in the Drosophila melanogaster polytene X chromosome

Region 20 of the polytene X chromosome of Drosophila melanogaster was studied in salivary glands (SG) and pseudonurse cells (PNC) of otu mutants. In SG chromosomes the morphology of the region strongly depends on two modifiers of position effect variegation: temperature and amount of heterochromatin. It is banded in XYY males at 25° C and β-heterochromatic in X0 males at 14° C, i.e. it shows dynamic transitions. In PNC chromosomes region 20 is not heterochromatic, but demonstrates a clear banding pattern. Some molecular markers of mitotic heterochromatin were localized by means of in situ hybridization on PNC chromosomes: DNA of the gene su(f) in section 20C, the nucleolar organizer and 359-bp satellite in 20F. The 359-bp satellite, which has been considered to be specific for heterochromatin of the mitotic X chromosome, was found at two additional sites on chromosome 3L, proximally to 80C. The right arm of the X chromosome in SG chromosomes was localized in the inversion In(1LR)pn2b: the telomeric HeT-A DNA and AAGAG satellite from the right arm are polytenized, having been relocated from heterochromatin to euchromatin. Received: 1 July 1998 / Accepted: 7 September 1998     

Double-stranded DNA with the size expected of replicons can be released from Chironomus polytene chromosomes

The effect of the drug 5-fluorodeoxyuridine on DNA synthesis in Chironomus polytene chromosomes was investigated. The DNA was labelled by injection of radioactive precursor into living animals pre-treated with the drug, extracted with a neutral non-denaturing buffer at 25 ° C and then characterized by gel electrophoresis. After a short pulse a heterogeneous double-stranded DNA population is released from the polytene chromosome. These fragments are later joined together to produce a double-stranded DNA with a size ranging between 8–13 × 10⁶ D. The release of both types of fragments from the polytene chromosome is prevented by lysing the cells at 0 ° C instead of at 25 ° C. The larger double-stranded DNA has the size expected of replicons in Chironomus. The results are discussed in relation to the organization of replication in polytene chromosomes.     

Polymorphism in the location of the 18S and 28S rRNA genes on the chromosomes of the diploid-tetraploid treefrogs Hyla chrysoscelis and H. versicolor

The chromosomes of the diploid Hyla chrysoscelis and its tetraploid sibling species H. versicolor were studied with AgNO₃ staining and in situ hybridization to determine the chromosome location of the 18S and 28S ribosomal RNA (rRNA) genes. A total of 236 Hyla chrysoscelis from 34 localities in 15 U.S. states and 100 H. versicolor from 15 localities in 12 states were examined. The rRNA gene sites were extremely variable in H. chrysoscelis, and also variable, but to a lesser extent, in H. versicolor. The most common rRNA gene site in both H. chrysoscelis and H. versicolor was on the short arm of chromosome 6. All of the rRNA gene locations seen in H. versicolor were also seen in H. chrysoscelis, supporting the hypothesis that the tetraploid H. versicolor arose from H. chrysoscelis. Although polymorphic rRNA gene sites in H. versicolor may reflect the positions of the rRNA genes in H. chrysoscelis ancestors, the origin of the extreme variability of such sites in H. chrysoscelis seems more obscure. Possible explanations include inversions, translocations, mobile genetic elements or a combination of some or all of these.     

Karyotypes,nucleoli, and amphiplasty in hybrids between Hordeum vulgare L. and H. bulbosum L.

Chromosome measurements were carried out in Hordeum vulgare, H. bulbosum, and their diploid, triploid, and tetraploid hybrids. The chromosomes were classified by using relative values, and thus karyotypes were established. For comparison of these karyotypes both relative and absolute values were used. It was concluded that differential amphiplasty occurred, whereas neutral amphiplasty could not be demonstrated. In the hybrids the relative length of the parts of the chromosomes (long arm, short arm, satellite) was not changed in comparison with these lengths in the pure species. The karyotypes of both species had considerable similarities. From comparing the mean absolute genome lengths, it was, however, concluded that in the pure species, as well as in all hybrid types, the chromosomes of H. vulgare were longer than those of H. bulbosum. In the diploid and tetraploid hybrids the mean genome lengths were shorter than those in the pure species and the triploid hybrids. The differential amphiplasty was such that the secondary constriction of chromosome 6 of H. bulbosum, did not show up in the hybrids. This could be related to the suppression of nucleolar formation in the genome of H. bulbosum, because the maximum number of nucleoli in root tip cells equalled the number of satellite chromosomes. Finally it was found that the pattern of nucleolar fusion in diploid and triploid hybrids deviated from the expectation. The results were discussed in relation to chromosomal disturbances that occurred in the hybrid tissues and that resulted in elimination of chromosomes and other effects.     

Somatic chromosomes of higher diptera

Summary The chromosome complements of eighty brain cells ofHylemya antiqua have been studied. The eighty cells were found in thirty-three larvae. Total complement length (TCL) is not randomly distributed among the larvae. Because there is an inverse correlation between chromosome length and width, it appears that in the cells studied the different chromosome lengths are partly expressions of different stages of metaphase contraction. It is suggested that synchronous division of cells still occurs in late larvae.The length of each chromosome arm is highly correlated with that of every other arm. It is possible that the correlations are complete but that inadequate technique causes the departures from completeness which are observed. The chromosome lengths are corrected slightly for distortions, but the corrections make very little difference in the correlation coefficients. There is a high value for the correlation between the correlation of two arm lengths and the sum of the two arm lengths. This is to be expected if the perfect correlation between all arm lengths is being obscured by errors of drawing and measurement.The autosomal arms have very similar coefficients of variation. The arm ratios (length of long arm divided by short arm) are not correlated with TCL or with each other, and arm ratio is randomly distributed among the larvae. The sex chromosomes have a smaller coefficient of variation than the autosomes, so that they are relatively large in small cells and relatively small in large cells.Twenty-two cells inHylemya fugax were measured. The autosomes also showed a high correlation between arm lengths. An entirely heterochromatic autosomal arm showed the same phenomenon of a low coefficient of variation which was shown by the heteropycnotic sex chromosomes inH. antiqua. The low variability of heterochromatic regions accompanied by an apparently non-random distribution of the TCL may produce an erroneous picture of the species complement when dealing with small numbers.It is suggested that for simplicity in using cytological observations of this sort for taxonomic purposes, the technique of measuring the percent TCL of a chromosome plus its arm ratio be replaced by the percent TCL of each arm plus the average length difference between the arms of each chromosome pair in units of percent TCL.     

Photoperiod acclimation and 24-hour variations in the critical thermal maxima of a tropical and a temperate frog

Summary The effect of photoperiod on the upper thermal tolerance of two species of frogs was studied by using the critical thermal maximum (CTM) as the end point. Both species are heliotropic and from temperate climates, but Hyla labialis lives under a near constant tropical photoperiod while Rana pipiens lives under a varying temperatezone photoperiod. The CTM of both species was studied over a 24-hour period to determine if a rhythm of temperature tolerance exists. In all but one of the acclimatization conditions used, the CTM of R. pipiens was higher than that of H. labialis. This agrees with what is known of their thermal ecology. Photoperiod significantly affects the CTM of both species. For Rana pipiens long (LD 16:8) photoperiods result in significantly higher thermal tolerance than short (LD 8:16) or moderate (LD 12:12) photoperiods at both 15 and 25° C. H. labialis shows a different pattern, having highest CTM at 25°C, LD 12:12 and lowest at 15°C, LD 12:12. When acclimated to a short (LD 8:16) photoperiod certain aspects of the frogs' tolerance of high temperatures are altered. At the same acclimatization the CTM of R. pipiens is higher than that of H. labialis, except under a combination short light regime and low temperature, and H. labialis at LD 8:16 shows no thermal acclimation between 15 and 25°C. Significant variation in the CTM over a 24-hour period occurred in H. labialis acclimatized at 25°C, LD 12:12 and R. pipiens at 25°C, LD 8:16 and 15°C, LD 12:12. For both species the 24-hour rhythm of temperature tolerance, when it occurs at LD 12:12, might be of adaptive value. Times of highest thermal tolerance are in the late morning or early afternoon and lowest tolerance is during the dark period. For R. pipiens under the unnatural combination of 25°C, LD 8:16, the pattern is reversed. When all three significant cycles are phase shifted so that the times of highest tolerance coincide, the pattern of the curves is very similar.     

The ZW sex chromosomes of <Emphasis Type="Italic">Gekko hokouensis</Emphasis> (Gekkonidae,Squamata) represent highly conserved homology with those of avian species

Populations of the gecko lizard Gekko hokouensis (Gekkonidae, Squamata) on Okinawajima Island and a few other islands of the Ryukyu Archipelago, Japan, have the morphologically differentiated sex chromosomes, the acrocentric Z chromosome and the subtelocentric W chromosome, although the continental representative of this species reportedly shows no sex chromosome heteromorphism. To investigate the origin of sex chromosomes and the process of sex chromosomal differentiation in this species, we molecularly cloned the homologues of six chicken Z-linked genes and mapped them to the metaphase chromosomes of the Okinawajima sample. They were all localized to the Z and W chromosomes in the order ACO1/IREBP–RPS6–DMRT1–CHD1–GHR–ATP5A1, indicating that the origin of ZW chromosomes in G. hokouensis is the same as that in the class Aves, but is different from that in the suborder Ophidia. These results suggest that in reptiles the origin of sex chromosomes varies even within such a small clade as the order Squamata, employing a variety of genetic sex determination. ACO1/IREBP, RPS6, and DMRT1 were located on the Z long arm and the W short arm in the same order, suggesting that multiple rearrangements have occurred in this region of the W chromosome, where genetic differentiation between the Z and W chromosomes has been probably caused by the cessation of meiotic recombination.     

Chromosome plasticity in Ctenomys (Rodentia Octodontidae): chromosome 1 evolution and heterochromatin variation

A chromosome 1 (Cr1) pericentric inversion is described in six of seven species in the genus Ctenomys (tuco-tucos) from Uruguay. The inversion was inferred from G-band analyses of subtelocentric Cr1 hypothesised to be derived from the ancestral metacentric condition. Cr1 varies across species in heterochromatin amount and localisation including a metacentric chromosome without positive C-bands in C. torquatus, a subtelocentric chromosome with heterochromatic short arms in C. rionegrensis, and a subtelocentric chromosome negative after C-banding in five of the species analysed here. Pachytene chromosomes from C. rionegrensis, a species with the highest heterochromatin content, and C. torquatus, one of the species with the lowest heterochromatin content, were analysed in order to assess possible mechanisms of heterochromatin evolution. This analysis revealed the presence of three heterochromatic chromocenters in C. rionegrensis where bivalents converge, while in C. torquatus only one chromocenter was observed. In both species, highly repetitive DNA was observed, localised in chromocenters after “in situ” hybridisation. Heterochromatin associated protein M31 was localised in chromocenters of both species after immuno-detection. The spread of heterochromatin in Ctenomys chromosomes could be produced by chromatin exchanges at the chromocenter level. We propose the exchange of this DNA associated proteins between non-homologous chromosomes in pachytene to be the responsible for the spread of heterochromatin through the karyotypes of species like C. rionegrensis     

Ecological impacts of invading species: Do parasites of the cane toad imperil Australian frogs?

Parasite transfer to native fauna is a potentially catastrophic impact of invasive species. Introduced cane toads in Australia frequently host the nematode lungworm Rhabdias pseudosphaerocephala, which reduces viability of metamorph toads. If native frogs are vulnerable to this South American parasite, cane toad invasion may affect native species via this route; but if the native taxa are not vulnerable, we may be able to exploit the parasites for managing toads. Our laboratory experiments show that infective larvae can penetrate the body of all seven species of Australian frogs (five hylids: Cyclorana longipes, Litoria caerulea, Litoria dahlii, Litoria nasuta, Litoria rothii, one myobatrachid: Opisthodon ornatus, and one limnodynastid: Limnodynastes convexiusculus) we tested, but most did not host the adult worms at the end of the trials, and none showed major impairment of growth, survival or locomotor performance. One native tree‐frog (L. caerulea) retained high infection levels with few ill effects, suggesting that we might be able to use this taxon as a reservoir species to build up local parasite densities for toad management. However, the interspecific variation in lungworm retention suggests that generalizations about parasite effects on native frogs will be elusive.