Distance segregation and compound sex chromosomes in mantispids (Neuroptera: Mantispidae)

The sex chromosomes segregate precociously in prometaphase I of male meiosis, without prior synapsis or any physical connection, in 4 species of American mantispids (Neuroptera: Mantispidae). Segregational movements are interpolar, and are implemented through chromosomal fibers. Univalent autosomes, present from diakinesis on in several species, are capable of a similar distance segregation in prometaphase. The sex chromosomes are XX —XY , as is characteristic of the Order, with the exception of Entanoneura phthisica in which both elements are compound —X¹X²X³Y¹Y²Y³in the male, and X¹X¹X²X²X³X³ in the female. In tetraploid sectors of gonial origin in testes of this species no sex bivalents are formed; a distance segregation of 6 sex univalents to each pole is effected, but — as observed in the one individually identifiable pair — segregation separates complete homologues, Y¹ from Y¹, X¹ from X¹, etc. In all species the male meiotic spindle is formed by the collocation of individual chromosomal spindle units within which bivalents become deformed; the timing and degree of deformation vary with the species. In karyotype the American species conform to a common pattern with the known Japanese and European species; diploid numbers range only from 18 to 22, and each complement carries the family insigné of one pair of disproportionately large autosomes in a set of small and rather uniformly sized chromosomes.     

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.     

Ultrastructural characterization of the sex chromosomes during spermatogenesis of spiders having holocentric chromosomes and a long diffuse stage

An ultrastructural study has been made of spermatogenesis in two species of primitive spiders having holocentric chromosomes (Dysdera crocata, XO and Segestria florentia X₁X₂O). Analysis of the meiotic prophase shows a scarcity or absence of typical leptotene to pachytene stages. Only in D. crocata have synaptonemal complex (SC) remnants been seen, and these occurred in nuclei with an extreme chromatin decondensation. In both species typical early prophase stages have been replaced by nuclei lacking SC and with their chromatin almost completely decondensed, constituting a long and well-defined diffuse stage. Only nucleoli and the condensed sex chromosomes can be identified. — In S. florentina paired non-homologous sex chromosomes lack a junction lamina and thus clearly differ from the sex chromosomes of more evolved spiders with an X₁X₂O male sex determination mechanism. In the same species, sex chromosomes can be recognized during metaphase I due to their special structural details, while in D. crocata the X chromosome is not distinguishable from the autosomes at this stage. — The diffuse stage and particularly the structural characteristics of the sex chromosomes during meiotic prophase are reviewed and discussed in relation to the meiotic process in other arachnid groups.     

Reversion of XO to XY sex chromosome mechanism in a phasmid

Summary The sex chromosomes of the male phasmid Isagoras schraderi Rehn comprise an X and a Y, — each with a submedian kinetochore, and one euchromatic and one heterochromatic arm. At meiosis X and Y form an unequal sex bivalent in which the euchromatic arms are terminally associated. Relatively recent reversion from the XO-XX mechanism characteristic of the Phasmidae is indicated by the presence of the euchromatic arm in both X and Y. The diploid number of the male is 34.Unequal autosomal bivalents are found at meiosis in two other species of Isagoras — Isagoras subaquiles Rehn and Isagoras sp. — and in Pseudophasma menius Westwood. The chromosome complements of these species are described.     

Endopolyploidization patterns in non-generative antheridial cells in mono- and dioeciousChara spp. (Characeae) with different DNA C-values

Cytophotometric measurements of nuclear DNA contents and morphometric analyses in the antheridia of five species ofChara indicate that the level of endopolyploidy plays an important role in determining the maximum sizes that shield cells, manubria, and capitular cells attain at the final stage of spermiogenesis. Dioecious species with low DNA C-values—C. aspera andC. tomentosa—display higher values of endopolyploidy: their male sex organs are larger and the quantities of spermatozoids per antheridium are greater than those estimated for monoecious species—C. vulgaris, C. fragilis, andC. contraria. Two types of nucleotypic effects were found to synchronize developmental traits in germ line cells and non-generative component parts within the antheridia; both are discussed in relation to the biological productivity of male sex organs in mono- and dioecious species ofChara.     

Asymmetry of heteropycnosis in tetraploid cells of a grasshopper

In XO male grasshoppers (Acridoidea and Eumastacoidea) X-chromatin is negatively heteropycnotic in spermatogonial mitoses. In neo-XY species which have a fusion between the original X and an autosome it is usual for the former alone to show negative heteropycnosis. This is the case in the Australian Morabine grasshopper species P52a. In tetraploid spermatogonia of this species, however, which contain two neo-X's and two neo-Y's, only one of the neo-X's has a negatively heteropycnotic left limb, the other X having the same degree of condensation as the autosomes. This novel type of behavior is compared with the heteropycnosis of one of the two X's in the somatic cells of female mammals. It is concluded that the asymmetry of condensation of the two X's in tetraploid spermatogonia of P52a demonstrates the existence of a fundamental cellular mechanism which is inherent and only expressed under the abnormal condition of tetraploidy.Supported by Public Health Service Grant 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.     

Chromosome relationships and meiotic mechanisms of certain morsitans group tsetse flies and their hybrids

There are three pairs of euchromatic components, the L₁ and L₂ autosomes and the X chromosome pair respectively, which are found in both G. austeni and the three forms of G. morsitans. Each species/sub-species also includes in its complement a group of heterochromatic autosomes (S) which have various morphologies and differ in number both within and between the species/sub-species. Several lines of evidence are outlined which point to these being supernumerary B chromosomes. Male meiosis is normally achiasmate and only L₁ and L₂ autosomes pair completely. X-Y association is restricted to a small pairing segment the position of which on the X is constant for all the species/sub-species. It is located in one of two positions on the Y chromosome according to the species/sub-species. The S chromosomes behave as hereditary univalents at first anaphase while the sex bivalent can undergo distance pairing best exemplified in G. austeni and G. submorsitans. A Y structural mutant line gives some indication of the size of the pairing segment and demonstrates that survival and maleness is possible even when two-thirds of the chromosome is missing. Meiotic and polytene chromosome studies connected with hybridisation experiments designed to test the sterility factor as a potential means of tsetse control assist in establishing the evolutionary relationship of the subspecies.     

Partial purification and characterization of β-hydroxybutyric acid dehydrogenase of a methylotrophic bacterium,Pseudomonas 135

Summary An intracellular enzyme, d(—)--hydroxybutyric acid dehydrogenase involved in an intracellular poly-d(—)--hydroxybutyric acid degredation was isolated from a facultative methylotrophic bacterium, Pseudomonas 135, grown on methanol as a sole carbon and energy source. This enzyme was partially purified to 11.6-fold by ammonium sulphate fractionation and a dye-affinity chromatography. The enzyme catalysed simultaneously the oxidation of d(—)--hydroxybutyric acid (D-HB) and the reduction of acetoacetate. The optimum pH was 8.5 for the oxidation reaction and 5.5–6.0 for the reduction reaction, and the enzyme was stable for 2 weeks at — 20° C. The K _m values for oxidation and reduction reactions were determined as 1.84 mm for D-HB, 0.244 mm for NAD⁺, 0.319 mm for acetoacetate and 0.032 mm for NADH, respectively. It was also found that d-lactate and NADH significantly inhibited the oxidation reaction by competitive inhibition, and acetoacetate by non-competitive inhibition, respectively. The inhibition constants were determined as 1.49 mm for d-lactate, 0.196 mm for NADH and 1.82 mm for acetoacetate, respectively. According to an experiment with resting cells, it seemed that the enzyme was constitutive. Correspondence to: J. M. Lebeault     

Ecological study of soil fungi of an agricultural field in Allahabad

Summary The soil fungi from an agricultural field in Allahabad where sugarcane is being grown for many years, have been isolated from various depths during different seasons and were identified. The inter-relations of chemical composition of soil and distribution of fungi is also being shown here.The techniques for the isolation and the study of the fungus flora was that ofGoddard modified bySaksena &Mehrotra. Soil samples were examined from 1–6 depths in three seasons of the year and were mechanically and chemically analysed.For the isolation, soil dilution plate method, a modification ofMenzies' method, direct method ofWaksman, Rossi Cholodny Burried slide technique, and screened immersion plate method, were followed Fifty five different species of microfungi belonging to Phycomycetes, Ascomycetes and Fungi — Imperfecti were isolated and identified. The moisture contents, hydrogen-ion concentrations, carbon, nitrogen, phosphorus, calcium, magnesium and iron, etc., of the soil samples from 1–6 inches depths, were also studied.Out of these 12 species covering 9 genera belonged to the Phycomycetes, nine genera of Ascomycetes and nine genera of Fungi Imperfecti were recorded.P. multicolor Grigorieva-Monoilova &Poradielova, andP. roqueforti Thom.,Gliocladium vermoesoni (Biourge)Thom. andMasoniella grisea (Smith)Smith were recorded for the first time from Indian Soil. A new varietyChaetominum nigricolor Ames var.simplex was also isolated.     

Karyotype differences in the crenaticeps-group of Atractomorpha (orthoptera,acridoidea, pyrgomorphidae)

The four known species of the crenaticeps-group of the genus Atractomorpha have 2n ()=18+X0. All members of the complement are rod-chromosomes and the smallest autosome (no. 9) is megameric. The four species have similar amounts of euchromatin but differ markedly in the amount of heterochromatin present in their genomes. In A. similis, A. crenaticeps and the unnamed species, Species-1, there are distinct proximal segments of heterochromatin in the eight large autosomes. In A. similis these chromosomes also have prominent distal segments of heterochromatin. The fourth species, A. australis, has no visible heterochromatin in its eight large autosomes except for a small segment at the proximal end of autosome 4. In all four species, the heterochromatic segments influence chiasma frequency and chiasma position. Moreover the overall chiasma frequency is lowest in A. similis with most heterochromatin and highest in A. australis with least heterochromatin.     

Hormonal control of sex differences in the electric organ discharge (EOD) of mormyrid fishes

Summary Field studies have demonstrated that several species of mormyrid fish from Gabon, West Africa have a sex difference in the pulse-like waveform of their Electric Organ Discharge (EOD). Administration of androgen hormones (testosterone or dihydrotestosterone) to a female or juvenile can induce the EOD typical of a sexually mature male. Data for two such species —Brienomyrus brachyistius (triphasic) andStomatorhinus corneti — are presented, showing that transformation of a female's or juvenile's EOD to a male-like EOD involves a 2–3 fold increase in EOD duration and a downward shift in the peak frequency of the EOD's power spectrum (as determined by Fourier analysis). ForBrienomyrus brachyistius (triphasic), estradiol can also induce changes in the EOD waveform, although not as dramatic as that for androgens. Changes in EOD duration and power spectra are often accompanied by an alteration of the wave-shape or morphology of the EOD pulse, i.e., the relative amplitude of its peaks and the presence of inflection points in its negative and positive phases.A third species,Hippopotamyrus batesii (triphasic), not previously known to have an EOD sex difference, also responds to testosterone treatment with an increase in EOD duration. Preliminary field data indicate this species may have a sexual dimorphism in its EOD, suggesting that the response to a steroid hormone may be an indicator of a sex difference in a species' EOD waveform. Such findings are discussed in relation to the affects of steroids on vertebrate neurons and muscle, and the evolution of electric communication systems.Abbreviations DHT 5-dihydrotestosterone - EOD electric organ discharge - F mature female - HTI interval between peaks (H and T) in EOD's first derivative - IF juvenile female - IM juvenile male - M mature male - PPW peak frequency of power spectrum     

Cytogenetic components of reproductive isolation in Trimerotropis thalassica and T. occidentalis

The grasshopper Trimerotropis thalassica (Bruner) has a diploid count of 2n=23 (XO), 24 (XX). The two largest autosomes pairs are regularly metacentric, a consequence of fixed pericentric inversions. The X-chromosome is also a fixed metacentric. The remaining nine pairs of autosomes are polymorphic for floating pericentric inversions so that the complement consists of a mixture of telocentric and metacentric members. Trimerotropis occidentalis (Bruner) is polymorphic for comparable inversions in only two of its autosome pairs and has a telocentric X. It is, however, unique among the species of the genus Trimerotropis in having only 21 chromosomes in its male diploid set in all the populations so far studied. A single male found in a mixed population of these two species at Jasper Ridge, Stanford University, was characterised by a count 2n=22. In both this respect and in its phenotype it was intermediate in character, representing a natural F₁ hybrid between the two species. Cytogenetic analysis of this hybrid male indicated that occidentalis is differentiated from thalassica only in respect of a single tandem translocation. This has involved two of the telocentric elements of thalassica which have fused into a single composite telocentric partly homologous with each of the smaller progenitors. Although potentially capable of forming a multiple of three, one or other of the progenitor chromosomes regularly fails to pair with the tandem product in the hybrid so that one or more univalents invariably occur. These, by lagging, prevent cytokinesis and subsequently lead to the formation of macrospermatids which inevitably produce a measure of sterility. It is argued that this sterility provides a basis for reproductive isolation.In fond memory of my assistant, collaborator and friend Michael George St. Clair-Freeman who died tragically in a motor accident in Canberra on September 16th 1976     

Late type of daughter cell wall synthesis in one of the Chlorellaceae, <Emphasis Type="Italic">Parachlorella kessleri</Emphasis> (Chlorophyta,Trebouxiophyceae)

Autosporulation is a common mode of propagation for unicellular algae. Autospore-forming species of Chlorellaceae, Chlorella vulgaris Beijerinck, C. sorokiniana Shihira et Krauss, C. lobophora Andreyeva, and Parachlorella kessleri (Fott et Nováková) Krienitz et al. have glucosamine as the main constituent of their rigid cell wall. Recent phylogenetic analyses have showed that the Chlorellaceae divided into two sister groups: the Chlorella-clade and the Parachlorella-clade. We compared the cell wall structure and synthesis of the daughter cell wall in the four species by electron microscopy using rapid freezing and freeze substitution methods. The cell wall of C. vulgaris, C. sorokiniana, and C. lobophora consisted of an electron-dense thin layer with an average thickness of 17–20, 22, and 19 nm, respectively. In these three species, daughter cell wall synthesis occurred on the outer surface of the plasma membrane in the early cell-growth phase. The cell wall of P. kessleri, however, was electron-transparent and 54–59 nm in thickness. Ruthenium red staining of P. kessleri indicated that ruthenium-red-specific polysaccharides accumulated over the outer surface of the plasma membrane. Immunoelectron microscopic observation with an anti--1, 3-glucan antibody and staining with wheat germ agglutinin (WGA) indicated that the cell wall contained -1, 3-glucan and WGA specific N-acetyl--D-glucosamine. In P. kessleri, daughter cell wall synthesis began after successive protoplast division. The daughter cell wall synthesis during autosporulation in the four species of Chlorellaceae can be classified into two types—the early and the late types.     

Population cytogenetics of the genus Caledia (Orthoptera: Acridinae)

The genus Caledia contains two species. C. species nova 1 is restricted to the Oriomo Plateau of S.W. Papua and has a complement of twelve telocentric chromosomes. The second species C. captiva has a much wider distribution pattern—from S.W. Papua in the North, down the entire Eastern seaboard of Australia to Southern Victoria. It is also found in the Northern Territory. Although the chromosome number is the same as C. species nova 1, four major and distinct chromosomal races can be distinguished in C. captiva. — The basic ancestral race is found in Tropical North Queensland at the base of the Cape York Peninsula. All twelve chromosomes are telocentric and the karyotypic organization is similar to that found in C. species nova 1 and in other Acridines. A second, general purpose karyotypic race has a wide distribution between S.W. Papua, Arnhem Land and the East Australian coast as far South as Brisbane. It is considered a derivative form of the ancestral type and is fixed for small pericentric inversions on seven pairs of chromosomes. In the South-Eastern Queensland region there exists a further race which carries large pericentric inversions on all the autosomes and the X chromosome. The situation here is confounded since the basic chromosomes can be represented as either acro or telocentrics. Various levels of polymorphism for the inversions exist between different chromosomes in different populations indicating considerable differentiation within this zone. This race is almost completely surrounded by the general purpose karyotype where the races are contiguous in certain parts of the range. — The South-Eastern corner of Australia is characterised by a chromosome race quite different from those found further North. Here a complex pericentric inversion system exists involving a series of seven small inversions and larger inversions on chromosomes 1, 2, 4 and 10. Chromosomes 2 and 4, in particular, are highly polymorphic. — The presence and persistence of these 4 chromosomal races can be accounted for in terms of the known climatic changes which have occurred in this region in the recent past.     

Autosomal fragmentations and fusions in odonata and their evolutionary implications

The fragmentation of autosomes in the karyotypes ofEnallagma cyathigerum (Charp.) (n=1415),Mecistogaster sp. (n=15),Hetaerina rosea Sel. (n=14),Libellula depressa L. (n=1213),Orthetrum coerulescens (Fabr.) (n=1213),Diplacodes bipunctata (Br.) (n=1315) andD. haematodes (Burm.) (n=1213) is discussed. Original material ofMecistogaster andHetaerina was not available.Fragmentations were found to be the only way in which the recombination index is obligatorily changed (increased) in dragonflies. In at least five out of the seven cases considered the chromosome number is not stabilised: cells in which fragmentation occurred and those in which it did not are found in the same individual (Enallagma, Libellula, Orthetrum, Diplacodes). Fragmentation results in an increase of chromosome number (a) up to the family type number level (Libellula, Orthetrum, D. haematodes), (b) above the latter (Hetaerina) and (c) above any chromosome number ever reported in dragonflies (Mecistogaster, D. bipunctata). In our material the element or elements formed by fragmentation have always the size and usually also the heterochromatic features of the m-chromosomes, irrespective of the presence or absence of the latter in the original complement.A review of species in which fusions of autosomes were recorded or can be assumed is given.Orthetrum brachiale (Beauv.) (n=11) is added to the list. The situation in this species and inSympetrum eroticum Sel. is discussed in detail.The most essential differences between the fusion of (an) autosome (s) with the sex element on one hand (cf.Kiauta, 1969), and the fusion of two or more autosomes on the other, lies in the observations: (a) that in the former case, fused and unfused complements occur in one individual, whereas the latter is specifically characteristic and occurs in all cells, all individuals and all populations of the species, and (b) that autosomal fusion results in an increase of chiasma frequency, due to which the recombination index in secondarily low-n complements remains the same as it was in the primary high-n sets, or becomes even higher (O. brachiale, S. eroticum).Autosomal fragmentation (found so far in some advanced forms only) is considered as a character of phylogenetic advancement. Autosomal fusion, on the other hand, does not have any relation with phylogeny.     

DNS-Reduplikationsmuster der Somatischen Chromosomen von Cricetus cricetus (L.)

The patterns of terminal DNA synthesis of the autosomes and sex chromosomes of Cricetus cricetus were studied. Characteristic late replicating segments are found on all chromosomes allowing identification of most autosomes. The sex chromosomes of both sexes behave similarly; in the male, half of the X and the entire Y are late replicating and heteropycnotic, in the female, half of one X and the whole of the other X. The isopycnotic part of the X-chromosome comprises about 5% of the haploid female complement.

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Wesentliche Teile der vorliegenden Arbeit werden von Fräulein Dorothee Hepp als Dissertation der Medizinischen Fakultät der Universität Freiburg i. Br. vorgelegt.

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Wir danken Dr. Susumu Ohno für kristiche des Munuskriptes und Fräulein Elke Faisst für ihre bei den experimentellen Arbeiten.     

Chromosome replication in four species of snakes

Chromosome measurements were performed in four species of snakes related at the level of suborder (Boa constrictor amarali, Xenodon merremii, Philodryas patagoniensis, Bothrops jararaca). The data obtained point out that pairs 1–3 were common to the four snakes and probably inherited from the ancestor of the suborder Serpentes. Pairs 5–8-W were characteristic of each snake; hence, it is possible to assume that they followed evolving after the appearing of the suborder Serpentes. Z-chromosomes were metacentric in B. constrictor amarali, X. merremii and B. jararaca and slightly submetacentric in P. patagoniensis. Area of these chromosomes varied from 8.6–10.6% of the haploid set in the four species studied.-The study of chromosome replication at the end of the S period points out that shared chromosomes have similar patterns of labeling. Therefore, it is proposed that the distribution of late replicating regions and heterochromatin in the genome is phylogenetically transmitted and probably genetically determined.—The analysis of the ending-sequence of chromosome replication shows that sex chromosomes finish earlier than macroautosomes. It is concluded that snakes probably have no mechanism of sex chromosome heterochromatinization in either sex. The absence of late replicating Z-chromosome in the males, favours the hypothesis that no mechanism of sex dosage compensation is acting in the suborder Serpentes.This work was partially supported by Public Health Service Research grant No. GM-14577-03 from the National Institute of General Medical Sciences and by the Fundo de Pesquisas do Instituto Butantan.     

Glycoconjugates in the secretory epithelium of the chicken mandibular gland

Summary In the secretory epithelium of the chicken mandibular gland, glycoconjugates have been studied by means of histochemical methods of light and electron microscopy. In light microscopy, a series of histochemical procedures have been employed which included lectin—peroxidase—diaminobenzidine methods and a digestion technique with neuraminidase or-amylase. In electron microscopy, a battery of methods were used that corresponded to those employed in light microscopy. In the secretory cells of the chicken mandibular gland, vicinal diol- and sulphate-containing glycoconjugates with sialic acid,-d-mannose,-d-glucose and-d-galactose residues were visualized and the possible histophysiological significances of such glycoconjugates were discussed with special reference to the functions of the salivary gland.     

Chemotaxonomical investigations of the generaBlackstonia andCentaurium (Gentianaceae)

Methanolic extracts from aerial parts and capsules of plants of 5 populations ofBlackstonia perfoliata and 99 populations of nine European and two AmericanCentaurium species (Gentianaceae) have been screened by means of TLC for the secoiridoid glucosides: sweroside, swertiamarin, gentiopicroside and the m-hydroxybenzoyl esters of sweroside, namely centapicrin, desacetylcentapicrin, decentapicrin A and B as well as for the xanthones: 1,8-dihydroxy-3,5-dimethoxyxanthone, 1,8-dihydroxy-3,7-dimethoxyxanthone, 1,8-dihydroxy-3,5,6,7-tetramethoxyxanthone and xanthone--mono-glucosides. The taxonomical significance of the results is discussed. On the basis of chemotaxonomical evidence twoCentaurium species,C. pulchellum andC. tenuiflorum, are placed in sect.Parviflora instead of sect.Centaurium subsect.Parviflora. Part 8 in the series Secoiridoids and Xanthones in the genusCentaurium. For part 7 see:Van der Sluis & Labadie (1985). — Parts of this study were presented at the 10th annual congress of Farmacognosie en Natuurstofchemie in Utrecht, Nederland, Nov. 11, 1983. For summary see:van der Sluis, W. G., & Labadie, R. P. (1984), Pharm. Weekbl.119, 905–906.     

C-banding and non-homologous associations

A chromosome complement formed by 16 autosomes and an Xy_p sex chromosome system was found in Epilachna paenulata Germar (Coleoptera: Coccinellidae). All autosomes were metacentric except pair 1 which was submetacentric. The X and the Y chromosomes were also submetacentric but the Y was minute. The whole chromosome set carried large paracentric heterochromatic C-segments representing about 15% of the haploid complement length. Heterochromatic segments associated progressively during early meiotic stages forming a large single chromocenter. After C-banding, chromocenters revealed an inner networklike filamentous structure. Starlike chromosome configurations resulted from the attachment of bivalents to the chromocenters. These associations were followed until early diakinesis. Thin remnant filaments were also observed connecting metaphase I chromosomes. Evidence is presented that, in this species, the Xy_p bivalent resulted from an end-to-end association of the long arms of the sex chromosomes. The parachute Xy_p bivalent appeared to be composed of three distinct segments: two intensely heterochromatic C-banded corpuscles formed the canopy and a V-shaped euchromatic filament connecting them represented the parachutist component. The triple constitution of the sex bivalent was interpreted as follows: each heterochromatic corpuscle corresponded to the paracentric C-segment of the X and Y chromosomes; the euchromatic filament represented mainly the long arm of the X chromosome terminally associated with the long arm of the Y chromosome. The complete sequence of the formation of the Xy_p bivalent starting from nonassociated sex chromosomes in early meiotic stages, and progressing through pairing of heterochromatic segments, coiling of the euchromatic filament, and movement of the heterochromatic corpuscles to opposite poles is described. These findings suggest that in E. paenulata the Xy_p sex bivalent formation is different than in other coleopteran species and that constitutive heterochromatic segments play an important role not only in chromosome associations but also in the Xy_p formation.