Chromosome banding in amphibia

A cytogenetic study performed on a population of the South American leptodactylid frog Eleutherodactylus maussi revealed multiple sex chromosomes of the X₁X₁X₂X₂/X₁X₂Y (=XXAA/XXA^Y) type. The diploid chromosome number is 2n=36 in all females and 2n=35 in most males. The multiple sex chromosomes originated by a centric fusion between the original Y chromosome and a large autosome. In male meiosis the X₁X₂Y (=XXA^Y) multiple sex chromosomes form a classical trivalent configuration. E. maussi is the first species discovered in the class Amphibia that is distinguished by a system of multiple sex chromosomes. Only one single male was found in the population with 2n=36 chromosomes and lacking the Y-autosomal fusion. This karyotype (XYAA) is interpreted as the ancestral condition, preceding the occurrence of the Y-autosome fusion.by H.C. Macgregor     

Complex sex-determining mechanisms in three species of South American grasshoppers (Orthoptera,Acridoidea)

The karyotype of three species of South American grasshoppers are studied in this paper. Leiotettix sanguineus has two chromosome races, one of them with 2n=23 and an XO sex mechanism and the other, as far as we know limited to the Cerro Chato population, with 2n=22 and an XY sex mechanism. Leiotettix politus has two kinds of individuals, one with 2n=14 and XY sex chromosomes and the other 2n=13 and an X₁X₂Y mechanism. Dichroplus dubius presents 2n=21 and an X₁X₂Y sex chromosomes. One of the three specimens studied shows aberrant behaviour in the meiotic process.     

Complex sex-linked fusion heterozygosity in the Australian huntsman spider Delena cancerides (Araneae: Sparassidae)

In the vast majority of spider species studied to date, the karyotype is homogeneous in morphology and exclusively telocentric. The sex-determining system consists of one to three X chromosomes in the male and, correspondingly, two to six in the female. This is the case in species of huntsman spiders belonging to the genera Heteropoda (2n=40+3X), Isopoda, Olios, and Pediana (2n=40+3X) and some populations of the colonial species Delena cancerides (2n=40+3X). In other populations of D. cancerides, wholesale fusion of the karyotype has occurred, reducing the standard huntsman karyotype of 43 telocentric chromosomes to 21 metacentrics and 1 telocentric. Eight of the centric fusion products, including an X-autosome fusion, are maintained in the heterozygous condition in males and, with the single telocentric, form a chain of nine chromosomes at meiosis. The two complexes comprising the chain behave as neo-X and neo-Y chromosomes, and thus the ancestral X₁X₂X₃X₁X₁X₂X₂X₃X₃ sex-determining system has been converted to a system of six X and four Y chromosomes in the male and twelve X chromosomes in the female. Since sex-linked complex heterozygosity is also found in a number of species of social termites, it is suggested that such heterozygosity may have adaptive significance for a colonial lifestyle. Breakdown products of the chain of nine are present in specimens of D. cancerides from Canberra and these appear to represent hybrid products between the 2n=22 and 2n=43 forms. Hybridisation may also have been involved in the origin of the chain-forming races.     

Stability of a multiple X chromosome system and associated B chromosomes in birch aphids (Euceraphis spp.; Homoptera: Aphididae)

Autosomal dissociations are a common feature of aphid karyotype evolution, but multiple X chromosome systems are rare. Birch-feeding aphids of the genus Euceraphis, however, have X₁X₂O males as a general rule, X₁ being always much larger than X₂. Only one species has XO males, and this condition appears to be secondary. Most Euceraphis karyotypes also have one or more, usually heterochromatic, elements that occur in the same numbers in both males and females, yet behave like X chromosomes at male and female meiosis I. They appear to be supernumerary, non-functional X chromosomes, although showing greater within-species stability in size and number than typical B chromosomes. Euceraphis gillettei forms a separate group within the genus and feeds on alders (Alnus species), yet has a similar system, and the two most closely related genera, Symydobius and Clethrobius, also have additional chromosomal elements possibly representing non-functional X chromosomes. Thus the multiple X chromosome system in these aphids seems to be a primitive condition.     

The chromosomes of Hemimerus bouvieri chopard (Dermaptera)

The parasitic insect Hemimerus bouvieri, of rather uncertain systematic position but probably an aberrant member of the order Dermaptera, shows 2n =7, 2n =8. The chromosomes appear to be holocentric. There is an X₁X₂Y sex chromosome mechanism in the male, and a sex-trivalent is formed at meiosis. The two autosomal bivalents seem to be chiasmate and the members of the sex-trivalent may also be held together by chiasmata, but this is uncertain. In general, these cytological features are similar to those of true earwigs (Forficulina).Supported by Public Health Service Grant GM-07212 from the Division of General Medical Seiendes, U.S. National Institutes of Health and by a grant from the Australian Research Grants Committee.     

Cytotaxonomy of the triatominae (Reduviidae: Hemiptera)

The chromosome number and meiotic cycle of 20 species of Triatominae have been investigated. In the male, there are five types of chromosome complement: 20+XY, 20+X₁X₂Y, 20+X₁X₂X₃Y, 18+XY and 22+XY.The cytological data suggest that the type number for the subfamily is 22 (20+XY). In the hybrids: Triatoma barberi () and T. protracta (), anomalous behavior of certain chromosomes has been observed. Phylogenetic relationships based on chromosome evidence in the subfamily have been discussed. It is suggested that fragmentation is the major factor for chromosome evolution in the group.     

Existe-T-IL des chromosomes sexuels multiples chez le campagnol,Microtus arvalis pallas?

The conclusions ofRaicu, Kirillova & Hamar (1969), according to whichMicrotus arvalis has multiple sex chromosomes (X ₁ X ₂ Y ₁ Y ₂, X ₁ X ₁ X ₂ X ₂), are in contradiction to the earlier work ofRenaud (1938) andMatthey (1953) who have reported heterogamety of the XY, XX type for this species as is the situation in the majority of mammals. The mechanism proposed byRaicu and his coauthors in unknown in mammals where only cases of multiple sex-chromosome mechanisms XY ₁ Y ₂, XX and X ₁ X ₂ Y, X ₁ X ₁ X ₂ X ₂ have been described. It was necessary therefore to reexamine the situation in this vole. The author is of the opinion that the conclusions ofRaicu and his coauthors cannot be substantiated and that in this case we have indeed the common type of sex determination.     

Chromosome banding in Amphibia

The chromosomes of the South American marsupial frogs Gastrotheca fissipes, G. ovifera, G. walkeri and Flectonotus pygmaeus were analyzed by means of conventional and various banding techniques. The karyotypes of G. ovifera and G. walkeri are characterized by highly differentiated XY/XX sex chromosomes. Whereas the X chromosomes and autosomes contain large amounts of constitutive heterochromatin, extremely little heterochromatin is located in the Y chromosomes. This is in contrast to all previously known amphibian Y chromosomes and the Y chromosomes of most other vertebrates. In the male meiosis of G. walkeri, the euchromatic segments of the heteromorphic XY chromosomes show the same pairing configuration as the autosomal bivalents. The karyotype of F. pygmaeus is remarkable for the unique presence of telocentric chromosomes and the high frequency of interstitially located chiasmata in the meiotic bivalents. The evolution of the karyotypes and sex chromosomes, the structure of the various classes of heterochromatin and the data obtained from meiotic analyses of the marsupial hylids are discussed.     

Karyotypes and meiotic mechanisms of some eumastacid grasshoppers from East Africa,Madagascar, India and South America

Five species of the subfamily Thericleinae from East Africa show various types of cryptochiasmatic meiosis in the male, in which the chiasmata are not visible in prophase and are only revealed in the course of first metaphase. Several of these species have very large chromosomes. Two species belonging to the subfamily Miraculinae, from Madagascar have 2 n=25 acrocentric chromosomes, the highest number known in the Eumastacidae. Their meiosis is of the normal type. — Eighteen species of the subfamily Pseudoschmidtiinae, also from Madagascar have, for the most part, small chromosomes and a very uniform karyotype, of 2 n=21 acrocentrics. A species of Xenomastax has acquired an X₁X₂Y sex chromosome mechanism as a result of two successive chromosomal fusions. A fusion beween autosomes has reduced the chromosome number to 2 n=19 in the genus Tetefortina. The male meiosis of the Pseudoschmidtiinae is quite orthodox. — Two species of Eumastacids belonging to the subfamily Mastacideinae, from South India, show 2 n=21 acrocentrics. The male meiosis is quite orthodox, with a rather high chiasma frequency. — Three South American species of Eumastacidae, belonging to the subfamilies Paramastacinae, Parepisactinae and Eumastacinae respectively, have karyotypes which seem to be very different from those of the Old World subfamilies that have been studied. Meiosis is normal.The cytological evidence thus confirms the view of systematists that the evolutionary divergence of the subfamilies of Eumastacidae is very considerable, and presumably ancient. As far as we can tell, each subfamily may be characterized by a typical or primitive karyotype. There have been fewer evolutionary fusions of chromosomes in the Thericleinae and Pseudoschmidtiinae than in the Morabinae and no chromosomal dissociations are known to have occurred in the two former subfamilies.Affectionately dedicated to Sally Hughes-Schrader, whose work has enlarged our cytogenetic horizons so greatly, on her 75th birthday, January 25, 1970.Supported by Public Health Service Grant No. GM-07212 from the Division of General Medical Sciences, U.S. National Institutes of Health and by a grant from the Australian Research Grants Committee.     

Chromosomes and sex determination in 13 araneid spiders of North-Eastern India

The diploid chromosome number of 13 species belonging to the family Araneidae (Araneae) ranges between 16 and 25. The sex-determining mechanism seems to be X₁X₂X₃X₄O in one species; X₁X₂X₃O in three species and X₁X₂O in the remaining 9 species. The X₁X₂X₃X₄O, sex-determining mechanism is reported for the first time in spiders. All the chromosomes are with terminal centromeres. C-band preparations in 5 species suggest procentric localization of constitutive heterochromatin in all the chromosomes, though distally located C-band positive blocks are also visible in a few chromosomes.It is suggested that chromosomal evolution in this family has taken place by gradual reduction in diploid number through tandem/centric fusion followed by pericentric inversion in autosomes and nondisjunction/duplication of one X, with subsequent loss of homology in sex chromosomes.     

Karyotypic conservation in the mammalian order monotremata (subclass Prototheria)

The order Monotremata, comprising the platypus and two species of echidna (Australian and Nuigini) is the only extant representative of the mammalian subclass Prototheria, which diverged from subclass Theria (marsupials and placental mammals) 150–200 million years ago. The 2n=63, 64 karyotype (newly described here) of the Nuigini echidna is almost identical in morphology and G-band pattern to that of the Australian echidna, from which it diverged about a million years ago. The karyotype of the platypus (2n=52) has several features in common with those of the echidna species; six pairs of large autosomes, many pairs of small (but not micro-) chromosomes, and a series of small unpaired chromosomes which form a multivalent at meiosis. Comparison of the G-band patterns of platypus and echidna autosomes reveals considerable homology. Chromomycin banding demonstrates GC-rich heterochromatin at the centromeres of many platypus and echidna chromosomes, and at the nucleolar organizing regions; some of this heterochromatin C-bands weakly in platypus (but not echidna) spreads. Late replication banding patterns resemble G-banding patterns and confirm the homologies between the species. Striking heteromorphism between chromosomes of some of the large autosomal pairs can be accounted for in the echidna by differences in amount of chromomycin-bright, late replicating heterochromatin. The sex chromosomes in all three species also bear striking homology, despite the difference in sex determination mechanism between platypus (XX/XY) and the echidna species (X₁X₁X₂X₂/X₁X₂Y). The platypus X and echidna X₁ each represent about 5.8% of haploid chromosome length, and are G-band identical. Y chromosomes are similar between species, and are largely homologous to the X (or X₁).     

Mechanism of sex determination inRumex hastatulus Baldw.

Summary The results presented indicate that the sex determination mechanism in the Texas race ofR. hastatulus 2n = 10 (XX + 8A); 2n = 10 (XX + 8A)] is intermediate between theX/Y andX/A systems. In this race, sex is determined to some extent by theX/A balance, but theY chromosome also affects sex expression, maleness or intersexuality being correlated with different ratios ofX andY chromosomes.The results obtained for the Texas race are fully compatible with data presented by Smith (1963) for the North Carolina race [ 2n = 8 (XX + 6A); 2n = 9 (XX ₁ Y ₂ + 6A)]. It may be concluded that evolution of the karyotype in this species is not accompanied by changes in the mechanism of sex determination.     

Notes on chromosome behaviour in the spermatogenesis of the damselflyEnallagma cyathigerum (Charp.) (Odonata: Coenagrionidae)

The chromosome number in the damselflyEnallagma cyathigerum (Charp.) is 2n =27, 2n =28, n =14 (13). The sex determining mechanism is XX-XO, the X segregates postreductionally in the male.     

XXXY sex chromosomes in males of the jumping spider genus Pellenes (Araneae: Salticidae)

Observations of male meiosis and female chromosome number indicate that eight species of Pellenes have the X₁X₂O male, X₁X₁X₂X₂ female sex chromosome system typical of salticids, four species have an X₁X₂X₃Y male, X₁X₁X₂X₃X₃X₃ female system, and one species has both X₁X₂O and X₁X₂X₃Y males. This is the first report of a Y chromosome in spiders. It is hypothesized that the X₁X₂X₂Y system was derived from an X₁X₂O system by a tandem X-autosome fusion which yielded the X₂ and a centric autosome-autosome fusion which yielded the Y. Data on heteropycnosis, chiasmata, segregation, chromosome number and arm length support this hypothesis. The distribution of the X₁X₂X₃Y system within the genus is phylogenetically confusing and suggests that the two sex chromosome systems have been maintained together as a polymorphism in some lineages for long periods of time or that there have been repeated derivations of the X₁X₂X₃Y or X₁X₂O systems.     

Laser kinetic spectroscopy studies of the bimolecular oxygenation of alpha- and beta-subunits within the R-state of human hemoglobin

Bimolecular oxygenation of tri-liganded R-state human hemoglobin (HbA) is described by bi-exponential kinetics with association rate constants k = 27.2 ± 1.3 (M·sec)^-1 and k = 62.9 ± 1.6 (M·sec)^-1. Both the observed processes have been assigned to the bimolecular oxygenation of - and -subunits of the native tetrameric protein by molecular oxygen. The quantum yields of photodissociation within the completely oxygenated R-state HbA are = 0.0120 ± 0.0017 and = 0.044 ± 0.005 for - and -subunits, respectively. The oxygenation reactions of isolated ^PCMB- and ^PCMB-hemoglobin chains are described by mono-exponential kinetics with the association rate constants k = 44 ± 2 (M·sec)^-1 and k = 51 ± 1 (M·sec)^-1, respectively. The quantum yields of photodissociation of isolated ^PCMB- and ^PCMB-chains (0.056 ± 0.006 and 0.065 ± 0.006, respectively) are greater than that observed for appropriate subunits within the R-state of oxygenated HbA.     

Photosynthesis and apparent affinity for dissolved inorganic carbon by cells and chloroplasts of Chlamydomonas reinhardtii grown at high and low CO2 concentrations

Chloroplasts with high rates of photosynthetic O₂ evolution (up to 120 mol O₂· (mg Chl)^-1·h^-1 compared with 130 mol O₂· (mg Chl)^-1·h^-1 of whole cells) were isolated from Chlamydomonas reinhardtii cells grown in high and low CO₂ concentrations using autolysine-digitonin treatment. At 25° C and pH=7.8, no O₂ uptake could be observed in the dark by high- and low-CO₂ adapted chloroplasts. Light saturation of photosynthetic net oxygen evolution was reached at 800 mol photons·m^-2·s^-1 for high- and low-CO₂ adapted chloroplasts, a value which was almost identical to that observed for whole cells. Dissolved inorganic carbon (DIC) saturation of photosynthesis was reached between 200–300 M for low-CO₂ adapted chloroplasts, whereas high-CO₂ adapted chloroplasts were not saturated even at 700 M DIC. The concentrations of DIC required to reach half-saturated rates of net O₂ evolution (K_m(DIC)) was 31.1 and 156 M DIC for low- and high-CO₂ adapted chloroplasts, respectively. These results demonstrate that the CO₂ concentration provided during growth influenced the photosynthetic characteristics at the whole cell as well as at the chloroplast level.Abbreviations Chl chlorophyll - DIC dissolved inorganic carbon - K_m(DIC) coneentration of dissolved inorganic carbon required for the rate of half maximal net O₂ evolution - PFR photon fluence rate - SPGM silicasol-PVP-gradient medium     

The karyotype of some Australian species of Macropathinae (Gryllacridoidea — Rhaphidophoridae)

The chromosome number of eight species of Australian Macropathinae are reported in this paper. They show basically the same karyotype as four South-American species of the genus Heteromallus. The basic karyotype for the subfamily Macropathinae is established as 2n=45-and 46, with an XO-XX sex mechanism; the X is metacentric.The genus Cavernotettix comprises a cytologically modern and dynamic group of species in which the basic karyotype is modified in several directions. There are two species with XY-XX sex mechanisms and three with X₁X₂YX₁X₁X₂X₂ systems. The latter mechanisms are reported for the first time in Gryllacridoidea.Sponsored by C.A.P.E.S. (Río de Janeiro, Brasil) and F.A.P.E.S.P. (São Paulo, Brasil).     

Production of β-mannosidase and β-mannanase by an alkalophilic Bacillus sp.

Summary An alkalophilic bacterium producing high amounts of the cell-associated -mannosidase and extracellular -mannanase was isolated from soil. The isolate (AM-001) that grew well in alkaline pH media was identified as a strain of Bacillus sp. The optimal cultivation temperature for enzyme production was 31° C for -mannosidase and 37° C for -mannanase with the optimum production medium composed of 1% konjac powder, 0.2% yeast extract, 2% Polypepton, 0.1% K₂HPO₄, 0.02% MgSO₄ · 7H₂O and 0.5% Na₂CO₃. Optimum pH and temperature for -mannosidase were 7.0 and 55° C, and for -mannanase were 9.0 and 65° C.     

The mechanism of sex determination in Rumex acetosella

Summary Cytogenetic studies were made with particular emphasis on the sex-determining mechanism in Rumex acetosella (6 x = 42) and its hybrids (F ₁, F ₂, BC ₁ and BC ₂) with R. hastatulus (synthetic 4 x = 16 = 4 A +4 X = and 4 x = 18 = 4 A + 2 (X Y ₁ Y ₂) = ). Rumex acetosella was almost strictly dioecious with 5050 male and female. Breeding tests revealed that the males were heterogametic. The longest chromosomes (S), usually two, are the sex chromosomes of this hexaploid species. The S chromosomes are homomorphic in both male and female. The sex chromosome: autosome ratios, and the strong epistatic male effect of the S ^M chromosome in the polyploid dioecious species and in the hybrids, are evidence of an X/Y Melandrium type sex-determining mechanism controlled by a single pair of homomorphic sex chromosomes. Thus, the sex chromosome formula of the males was S ^F S ^M and that of females was S ^F S ^F. The present approach is a new method for resolving the sex-determining mechanism in a dioecious species.     

Passive cable properties of locust ocellar L-neurons

Summary The passive electrical cable properties of ocellar L-neurons were determined by applying current steps and recording the voltage transients using a two-electrode intracellular current clamp system. Morphological data were obtained following intracellular staining with Lucifer yellow.Two groups of neurons were distinguished physiologically. In the first group both the membrane time constant _m and the first equalizing time constant ₁ could be determined. In the second group only _m was measurable. The ratio of the physiological groups was equal to the ratio of the morphological types ML:(M1 plus M2) in the median ocellar nerve. Thus the first group probably consists of ML-type L-neurons. The passive cable properties of this group were calculated by combining the physiological and morphological data. The following values were obtained: electrotonic lengthL=1.35; membrane time constant _m =7.6 ms; length constant =0.22 cm; membrane resistivityR _m=2.0 · 10³ · cm²; membrane capacitanceC _m=3.8 F · cm^–2; intracellular resistivityR _i=24 · cm. Evidence is presented that the membrane parameters of the other types of L-neurons have the same values. The results are discussed with special reference to transmission in the ocellar system.