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Sex chromatin and chromosome number in Lepidoptera

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Abstract

Three classes of sex chromatin (SC) distribution have been encountered in a sample of Canadian Lepidoptera. In 78 of the 103 species examined, females were SC positive and males were SC negative. In another 24 species, females and males were SC negative. Females and males of a single species, Eucordylea resinosae, had two equal-sized SC bodies in interphase nuclei. In no species were females found to be SC negative and males SC positive. Usually presence of SC indicates an XX male and XY female sex determining mechanism, and its absence, XX male; XO female, but the exceptional occurrence of SC in females and males of a species suggests the need for caution in too universal an application of this interpretation. Chromosome numbers have also been determined for 53 of the 103 species. Male haploid numbers ranged from 11 to 61, but 30 was most frequently encountered.

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... The spruce budworm has also been at the center of many studies examining various aspects of its biology, including its cytogenetic characteristics. It was reported that its karyotype consists of 30 pairs of chromosomes, including a pair of large chromosomes, presumably sex chromosomes (Ennis 1976;Harvey 1997). According to recent data, large sex chromosomes are a typical feature of most tortricids, with Z chromosomes having arisen from the fusion between an ancestral Z chromosome and an autosome corresponding to chromosome 15 of Bombyx mori Síchová et al. 2013). ...
... We have combined cytogenetic approaches and a high-density SNPbased linkage map to explore the organization of the spruce budworm genome. Our karyotype analyses confirmed the presence of 30 pairs of chromosomes in Choristoneura fumiferana, a number commonly found in Tortricinae, one of three subfamilies recognized in the Tortricidae (Robinson 1971;Ennis 1976;Harvey 1997;Síchová et al. 2013). Our molecular cytogenetic analyses also enabled identification of a noticeably larger pair of chromosomes in both sexes. ...
... Marec,unpublished data;9 Traut et al. (2007) and Marec et al. (2010) reported $40 species]. Interestingly, the number of lepidopteran species for which the sex chromosome system has been described is much smaller than the number for which chromosomes have been quantified ($1,000;Robinson 1971;Ennis 1976;Blackmon et al. 2017). This difference may be attributed to the fact that many earlier studies used male germ cells, which are appropriate for chromosome counts, but not for identifying the sex chromosomes Sahara et al. 2012). ...
Article
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Genome structure characterization can contribute to a better understanding of processes such as adaptation, speciation, and karyotype evolution, and can provide useful information for refining genome assemblies. We studied the genome of an important North American boreal forest pest, the spruce budworm, Choristoneura fumiferana, through a combination of molecular cytogenetic analyses and construction of a high-density linkage map based on single nucleotide polymorphism (SNP) markers obtained through a genotyping-by-sequencing (GBS) approach. Cytogenetic analyses using fluorescence in situ hybridization methods confirmed the haploid chromosome number of n = 30 in both sexes of C. fumiferana and showed, for the first time, that this species has a WZ/ZZ sex chromosome system. Synteny analysis based on a comparison of the Bombyx mori genome and the C. fumiferana linkage map revealed the presence of a neo-Z chromosome in the latter species, as previously reported for other tortricid moths. In this neo-Z chromosome, we detected an ABC transporter C2 (ABCC2) gene that has been associated with insecticide resistance. Sex-linkage of the ABCC2 gene provides a genomic context favorable to selection and rapid spread of resistance against Bacillus thuringiensis serotype kurstaki (Btk), the main insecticide used in Canada to control spruce budworm populations. Ultimately, the linkage map we developed, which comprises 3586 SNP markers distributed over 30 linkage groups for a total length of 1720.41 cM, will be a valuable tool for refining our draft assembly of the spruce budworm genome.
... The studies on chromosome number of Lepidoptera initiated by Henking (1890) were followed by many workers and in the mid 20 th century, about 245 species were known as reported by White 1957. Later on many workers added data to this list (Bigger,1975(Bigger, ,1976De Lesse ,1960,1966, 1967,1970Maeki 1957a,b,c ,1961, 1981Maeki and Ae 1966Saitoh,1960;Suomalainen 1953Suomalainen , 1963Suomalainen , 1965Ennis, 1976;Trentini and Marini 1986;Sharma and Sobti 2000). ...
... Thus, present investigation also suggest a diffused in both the species investigated in Suomalainen 1969, ). However Bigger (1975 and1976), ) have reported localized centromere in such chromosomes with improved techniques in family International Journal of Recent Scientific Research Vol. 7, Issue, 8, pp. 12840-12843, August, 2016Bauer, H. (1967. ...
... Karyotypes of three species of lepidoptera including an investigation of B chromosomes in Pieris sp. Cytologia, 41: 261 Ennis, T.J. (1976). Sex chromatin and chromosome numbers in lepidoptera. ...
Research
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In the present study, the karyotype of two teak defoliator sps. of, Eutectona, Hyblaea was studied from Jammu region, India. Chromosomal studied were made from testis by using 2% Giemsa air drying method. The chromosomes at metaphaseI stage appeared almost of similar size. The haploid chromosome numbers observed in E machaeralis and H purea were 18 and 31, respectively. The largest chromosome was 1.3μm and 0.9 μm in length while the shortest chromosome was 0.4μm &0.3μm respectively. Centromeric fusion of chromosome in these species must played active role leading to decrease in diploid chromosome number.
... Our knowledge on the evolution of lepidopteran sex chromosomes largely stems from the female-specific sex chromatin, i.e., heterochromatic body observed in female interphase nuclei, which corresponds to the W chromosome and can thus be used as indirect evidence of its presence (Ennis 1976;Traut and Marec 1996). Systematic screening for the presence of sex chromatin revealed that basal lepidopteran lineages and caddisflies share the sex chromosome constitution Z0/ZZ. ...
... Among others, he described a sex chromosome trivalent W 1 W 2 Z in two moths of the family Tortricidae, Bactra furfurana and B. lacteana. Other members of this family are characterized by the presence of two conspicuously large elements that correspond to a sex chromosome pair which most likely arose from a sex chromosome-autosome fusion (Suomalainen 1971;Ennis 1976). This large chromosome pair has been observed in all tortricids karyotyped so far (for a comprehensive list of karyotyped species, see Šíchová et al. 2013) and was subjected to detailed molecular analyses (Fuková et al. 2005;Šíchová et al. 2013). ...
... In addition, a similar noticeably large chromosome pair has repeatedly been reported in several families within the mega-diverse superfamily Gelechioidea (Ennis 1976;Kawazoé 1987;Lukhtanov and Puplesiene 1999). Recently, this large chromosome pair has been proven to be the sex chromosomes in the tomato leafminer Tuta absoluta (Gelechiidae) (Carabajal Paladino et al. 2016). ...
Chapter
Chromosome rearrangements can play an important role in adaptive evolution and speciation with gene flow. Here, we briefly review state of the art in chromosomal speciation, along with the classic model of sex chromosome evolution. The main focus lies on sex chromosome?autosome fusions, i.e., neo-sex chromosomes. We describe the presence of neo-sex chromosomes in moth and butterflies (Lepidoptera), the largest group with female heterogamety. Despite the relative stability of lepidopteran karyotypes, fusions which result either in multiple sex chromosomes (W1W2Z or WZ1Z2) or large sex chromosome pairs occurred at a surprisingly high frequency throughout their evolution. We discuss the role of meiotic drive, genetic drift, and selection in the establishing of these derived sex chromosome systems. It is hypothesized that the association between sex-linked reproductive isolation or female preference and larval performance may contribute to ecological specialization and species formation in Lepidoptera.
... That the Lepidopteran chromosomes, except for minor differences in size, present remarkable uniformity in morphology and behaviour during the meiotic cycle have been well documented (Seiler, 1914;Beliajeff, 1930;Federly, 1938;Lorkovic, 1941;Gupta, 1964;Suomalainen, 1969;Rishi, 1973Rishi, , 1975Nayak, 1975;Ennis, 1976 White (1954, p. 176) considered 31 as the most frequent haploid number in the members of the group studied to that date with 29,30 and 3 1 so nearly equally frequent that he did not feel any of these numbers to be considered as the type number in preference to the others. In the present investigations, chromosome numbers of all the eleven species of the noctuids have a haploid chromosome number n = 31 which agrees with the modal haploid chromosome number (n = 31) established for this family and for Lepidoptera in general (Saitoh, 1959;Bigger, 1960Bigger, , 1961Gupta, 1964;Robinson, 1971;Saitoh et. ...
... A pair of chromosomes larger than others frequently occurring in species with high chromosome numbers have been considered as the sex-chromosomes by many workers (Bauer, 1943;White, 1954White, , 1973Suomalainen, 1969Suomalainen, , 1971). Ennis Suomalainen (1969), White (1973) and Ennis (1976) are to be taken as correct, we may consider the larger bivalent in such species as the XX-sex chromosome pair. ...
... Genetic erosion and accumulation of repetitive sequences lead to heterochromatinization of the W chromosome, multiple copies of which form a conspicuous spherical body called sex chromatin in somatic polyploid nuclei [1]. The presence of this sex chromatin body has been used as a simple, though not entirely reliable, assay to determine the presence of the W chromosome in particular species [7][8][9][10]. ...
... The sex chromatin assay was negative in all bagworm specimens examined, indicating the absence of the W chromosome. This method was used as indirect evidence of the W chromosome presence/absence in many lepidopteran species, which was consequently used as a basis for hypotheses about the W chromosome origin (e.g., [8,9,12,33]). However, there are some limitations, since certain chromosomal rearrangements involving the W chromosome are known to disrupt sex chromatin formation. ...
Article
Full-text available
Moths and butterflies (Lepidoptera) are the largest group with heterogametic females. Although the ancestral sex chromosome system is probably Z0/ZZ, most lepidopteran species have the W chromosome. When and how the W chromosome arose remains elusive. Existing hypotheses place the W origin either at the common ancestor of Ditrysia and Tischeriidae, or prefer independent origins of W chromosomes in these two groups. Due to their phylogenetic position at the base of Ditrysia, bagworms (Psychidae) play an important role in investigating the W chromosome origin. Therefore, we examined the W chromosome status in three Psychidae species, namely Proutia betulina, Taleporia tubulosa, and Diplodoma laichartingella, using both classical and molecular cytogenetic methods such as sex chromatin assay, comparative genomic hybridization (CGH), and male vs. female genome size comparison by flow cytometry. In females of all three species, no sex chromatin was found, no female-specific chromosome regions were revealed by CGH, and a Z-chromosome univalent was observed in pachytene oocytes. In addition, the genome size of females was significantly smaller than males. Overall, our study provides strong evidence for the absence of the W chromosome in Psychidae, thus supporting the hypothesis of two independent W chromosome origins in Tischeriidae and in advanced Ditrysia.
... Some of the derived sex chromosome systems correspond to a conspicuously large sex chromosome pair S ıchov a et al. 2013;Mongue et al. 2017;Picq et al. 2018), which suggests that both W and Z sex chromosomes fused with an autosome. Similar large chromosome pairs were also observed in representatives of the families Pyralidae, Oecophoridae, and Gelechiidae with reduced chromosome numbers, but were considered autosomal fusion products (Ennis 1976). Carabajal , however, showed that the large chromosome pair corresponds to sex chromosomes in an invasive gelechiid pest, the tomato leafminer Tuta absoluta (Gelechiidae). ...
... 1A, B, E, F and 2D, E). The existence of a conspicuously large chromosome pair was a characteristic feature of the Gelechioidea karyotypes described to date (supplementary table S6, Supplementary Material online) and Ennis (1976) regarded them as autosomal fusion products. The GISH experiments performed in this study, however, confirmed that the largest chromosome pairs are indeed sex chromosomes in T. absoluta and H. pseudospretella (figs. ...
Article
Full-text available
Sex chromosomes play a central role in genetics of speciation and their turnover was suggested to promote divergence. In vertebrates, sex chromosome–autosome fusions resulting in neo-sex chromosomes occur frequently in male heterogametic taxa (XX/XY), but are rare in groups with female heterogamety (WZ/ZZ). We examined sex chromosomes of seven pests of the diverse lepidopteran superfamily Gelechioidea and confirmed the presence of neo-sex chromosomes in their karyotypes. Two synteny blocks, which correspond to autosomes 7 (LG7) and 27 (LG27) in the ancestral lepidopteran karyotype exemplified by the linkage map of Biston betularia (Geometridae), were identified as sex-linked in the tomato leafminer, Tuta absoluta (Gelechiidae). Testing for sex-linkage performed in other species revealed that while LG7 fused to sex chromosomes in a common ancestor of all Gelechioidea, the second fusion between the resulting neo-sex chromosome and the other autosome is confined to the tribe Gnoreschemini (Gelechiinae). Our data accentuate an emerging pattern of high incidence of neo-sex chromosomes in Lepidoptera, the largest clade with WZ/ZZ sex chromosome system, which suggest that the paucity of neo-sex chromosomes is not an intrinsic feature of female heterogamety. Furthermore, LG7 contains one of the major clusters of UDP-glucosyltransferases, which are involved in the detoxification of plant secondary metabolites. Sex chromosome evolution in Gelechioidea thus supports an earlier hypothesis postulating that lepidopteran sex chromosome–autosome fusions can be driven by selection for association of Z-linked preference or host-independent isolation genes with larval performance and thus can contribute to ecological specialization and speciation of moths.
... However, the Amphiesmenoptera, containing the sister-groups Lepidoptera (butterflies and moths) and Trichoptera (caddisflies) (Misof et al. 2014) has an alternative sex chromosome system with heterogametic females. All caddisflies and basal moths studied thus far have Z0/ZZ (female/male) sex chromosomes (Ennis 1976;Traut and Marec 1996;Marec and Novák 1998;Lukhtanov 2000). At some point in the evolution of Lepidoptera, the W chromosome arose, but the phylogenetic origin and its mechanism remain unknown. ...
... Due to its heterochromatic nature, the W chromosome forms a conspicuous heteropycnotic body in nearly all somatic cells of most lepidopteran females. This so-called sex chromatin (or W chromatin) observed in Malpighian tubules has been used as a convenient, yet indirect, evidence for the presence of the W chromosome in a particular species (e.g., Traut and Mosbacher 1968;Ennis 1976;Traut and Marec 1996;Lukhtanov 2000). In fact, the vast majority of data on the W chromosome distribution in Lepidoptera were obtained through the analysis of the sex chromatin. ...
Article
Full-text available
Moths and butterflies (Lepidoptera) represent the most diverse group of animals with heterogametic females. Although the vast majority of species has a WZ/ZZ (female/male) sex chromosome system, it is generally accepted that the ancestral system was Z/ZZ and the W chromosome has evolved in a common ancestor of Tischeriidae and Ditrysia. However, the lack of data on sex chromosomes in lower Lepidoptera has prevented a formal test of this hypothesis. Here, we performed a detailed analysis of sex chromosomes in Tischeria ekebladella (Tischeriidae) and 3 species representing lower Ditrysia, Cameraria ohridella (Gracillariidae), Plutella xylostella (Plutellidae), and Tineola bisselliella (Tineidae). Using comparative genomic hybridization we show that the first 3 species have well-differentiated W chromosomes, which vary considerably in their molecular composition, whereas T. bisselliella has no W chromosome. Furthermore, our results suggest the presence of neo-sex chromosomes in C. ohridella. For Z chromosomes, we selected 5 genes evenly distributed along the Z chromosome in ditrysian model species and tested their Z-linkage using qPCR. The tested genes (Henna, laminin A, Paramyosin, Tyrosine hydroxylase, and 6-Phosphogluconate dehydrogenase) proved to be Z-linked in all species examined. The conserved synteny of the Z chromosome across Tischeriidae and Ditrysia, along with the W chromosome absence in the lower ditrysian families Psychidae and Tineidae, suggests a possible independent origin of the W chromosomes in these 2 lineages.
... The karyotypes of some species of the family Notodontidae from Europe, Japan, North Africa, India and Canada are known (ROBINSON, 1971;TEMPLADO & ORTIZ, 1970;SAITOH et aI., 1969;KAUR, 1988;ENNIS, 1976). The present study reports some data on the haploid chromosome numbers of 4 species from 4 genera of Noto ontidae rom the Far East of Russia. ...
... All the bivalents gradually decrease in size. and was also found in other species from different regions (ROBINSON, 1971;ENNIS, 1976). The species of the Pygaerinae differ in the haploid number, in contrast to a consistent number in the species of Notodontinae. ...
Article
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The present paper reports the data on the haploid chromosome numbers of 4 species of Notodontidae, collected in the Far East of Russia. All the descriptions of the karyo-types are presented here for the first time. Pe31OMe: B CTaTbe onHCblBalOTCR KapHoTHnbl 4eTbipex BH.QOB XOXJlaTOK c AaJlbHerO BocToKa POCCHH. Zusammenfassung: In dieser Arbeit werden die Karyotypen von 4 Arten der Familie Noto-dontidae erstmals beschrieben.
... In the case of human Alu elements, there is no report of a transposable element containing an Alu sequence [International Human Genome Sequencing Consortium (52)]. In Drosophila, there is no SINE in the genome (51). ...
... A sex chromatin body (SB) observed in the nuclei of lepidopteran females, has been deduced to be composed of condensed W chromosomes (52,53). The SB is detected in the nuclei of sucking stomachs in females by staining with acetic orcein (54). ...
Chapter
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Sex chromosomes of the silkworm, Bombyx mori, are designated as ZW (XY) for females and ZZ (XX) for males. The female mode of development is determined by the presence of a single W chromosome. Therefore, it is presumed that the female-determining gene (Fem) is present on the W chromosome. Until date, 12 W-specific random amplified polymorphic DNA (RAPD) markers have been identified on the normal W chromosome. We have compared the W-translocation chromosomes with normal W chromosome. The T(W;3)Ze (the sex-limited Zebra strain) chromosome lacked 2 W-specific RAPD markers, indicating that the region containing these two W-specific RAPD markers has been deleted. Additionally, we have investigated T(W;2)Y (the sex-limited Yellow-cocoon strain). The T(W;2)Y chromosome lacked 11 such markers. These results indicate that the W chromosomes of the sex-limited strains are the products of reciprocal translocation accompanied by deletion, and an extremely limited region is required to determine femaleness. No genes for morphological traits have been mapped to the W chromosome. Contrary, Z chromosome is rich in genes. Many long terminal repeat (LTR) and non-LTR retrotransposons, retroposons, DNA transposons, and their derivatives, had accumulated as strata on the W chromosome. It is notable that some of these transposable elements contained the Bombyx short interspersed element (Bm1) sequences in the elements. On the other hand, the transposable elements on the Z chromosome were excluded by unequal crossing over or intra-element homologous recombination between LTRs.
... Since the species descriptions of , many studies have attempted to resolve the taxonomy of the spruce budworm complex using characters from genitalia De Benedictis, 1995), eggs (Harvey, 1983, larval, pupal and adult colour (Volney et al., 1983, adult forewing and hindleg basitarsal spine length (De Benedictis, 1995), pheromone attraction (e.g. Sanders, 1971;Sanders et al., 1977;Powell, 1995), larval host association , sex chromatin and chromosome numbers (Ennis, 1976), allozymes Harvey, 1996) and mtDNA . The most recent bibliography of C. fumiferana, although published over 20 years ago , cited 4318 reports and papers mentioning some aspect of the biology of the spruce budworm species complex. ...
... Many taxonomic studies have been undertaken to better identify the species of the 64 spruce budworm complex. These include studies on their morphology for every stage of development Harvey, 1983;Volney et al., 1983Volney et al., , 1984De Benedictis, 1995;, behavioural traits Stehr, 1967;Volney et al., 1984;Powell, 1995;Shepherd et al., 1995), ecogeographical characteristics (Stehr, 1967;Shepherd et al., 1995), and genetic characters (Ennis, 1976;Harvey, 1996;). ...
Thesis
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Species identifications have been historically difficult in the economically important spruce budworm (Choristoneura fumiferana) pest complex. Morphological, ecological, behavioural, and genetic characters have been studied to try to understand the taxonomy of this group, but diagnostic character states differ in frequency rather than being complete replacements between each species. I developed a morphology-based character system that focuses on forewing colour components (Chapter 2), as well as eight simple sequence repeats (SSRs, also referred to as microsatellite markers) (Chapter 3). I tested these along with a 470 bp region of COI mitochondrial DNA (mtDNA) (Chapter 2, 4) to determine their congruence with putative species that were identified by adaptive traits (larval host plant, length of larval diapause, larval and adult morphology, pheromone attraction, distribution). The morphometrics system was effective for identification of the five species tested, with only slight overlap between C. fumiferana and C. biennis. MtDNA distinguished C. fumiferana and C. pinus pinus, but the remaining species shared haplotypes. SSRs distinguished four species (C. fumiferana, C. pinus pinus, C. retiniana, C. lambertiana) but the remaining four species that were included in this survey (Chapter 4) remained mixed within two populations. There was evidence for hybridization between several species pairs. I also conducted a detailed study (Chapter 5) in Cypress Hills, an isolated remnant coniferous forest in western Canada, where identifying individuals from the Choristoneura fumiferana complex has been impossible due to the unusual ecogeographic characteristics of the area. I integrated data on behaviour, ecology, morphology, mtDNA, and SSRs, comparing Cypress Hills populations to those from other regions of North America to determine which species they resembled most. I delimited at least three populations, resembling C. fumiferana, C. occidentalis and C. lambertiana. Adult flight phenology, along with pheromone attraction, were identified as major isolating mechanisms between these populations. My studies highlighted the importance of integrative taxonomy for understanding species boundaries. Their patterns of differentiation suggest that spruce budworm species have recently diverged via natural selection in spite of some gene flow. Overall, this work is intended to contribute to more accurate identification of specimens and a better understanding of the evolutionary processes that drive speciation.
... Of the three species chromosomally examined during this study, two of them, D. hyrtaca and T. siva, have a base number n"31 which is in close correspondence with the modal haploid number of the family Lasiocampidae 19(4): 227-229, 1980(84) 229 and with that of Lepidoptera in general (Kemewitz, 1915;Beliajeff, 1930;Saitoh, 1970;Robinson, 1971;White, 1973;Ennis, 1976 (Federly, 1945), 26 in Trahla vishnu (Nayak, 1975), 25 in Malacosoma indica (Rishi, 1973) and 26 in C. torrida (present report) indicate a trend towards evolution of lower chromosome numbers, and chromosomal fusion rather than dissociation appears to have played the main role in the process. The lagging anaph^ic movement of a pair of elements in Dendrolinus hyrtaca and Taragamd siva, perhaps the homologues of a bivalent, points to their sex-chromosome (XX pair) nature. ...
... The large bivalent occurring in the chromosome garniture of some species of Lepidoptera has often been considered as the sex bivalent (Bauer, 1943;White, 1973;Suomalainen, 1969bSuomalainen, , 1971Ennis, 1976). Traut and Mosbacher (1968) distinguished the sex chromatin as a distinctly heteropycnotic body in the somatic interphase nuclei in the females of 70 out of 83 species they examined and took it as the Y-chromosome since the presence of such a body was not observed in the corresponding males. ...
... However, available studies show an unusual occurrence of sex chromatin in this group. Of the 23 species tested so far, the sex chromatin pattern was atypical in females in 7 of them, despite the fact that the species were phylogenetically distant ( [38,39]; reviewed in the work of [24]). Furthermore, geometrids differ noticeably in chromosome numbers, suggesting dynamic karyotype evolution by fusions and fissions that could include sex chromosomes [40,41]. ...
Article
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Sex chromatin is a conspicuous body that occurs in polyploid nuclei of most lepidopteran females and consists of numerous copies of the W sex chromosome. It is also a cytogenetic tool used to rapidly assess the W chromosome presence in Lepidoptera. However, certain chromosomal features could disrupt the formation of sex chromatin and lead to the false conclusion that the W chromosome is absent in the respective species. Here we tested the sex chromatin presence in 50 species of Geometridae. In eight selected species with either missing, atypical, or normal sex chromatin patterns, we performed a detailed karyotype analysis by means of comparative genomic hybridization (CGH) and fluorescence in situ hybridization (FISH). The results showed a high diversity of W chromosomes and clarified the reasons for atypical sex chromatin, including the absence or poor differentiation of W, rearrangements leading to the neo-W emergence, possible association with the nucleolus, and the existence of multiple W chromosomes. In two species, we detected intraspecific variability in the sex chromatin status and sex chromosome constitution. We show that the sex chromatin is not a sufficient marker of the W chromosome presence, but it may be an excellent tool to pinpoint species with atypical sex chromosomes.
... Similarly, the W chromosome of the wild silkmoth, Samia cynthia, does not have the female-determining function (Yoshido et al. 2016). And several ditrysian species have even lost their W chromosome, they can do without it (Traut and Mosbacher 1968;Ennis 1976;Sahara et al. 2012;Dalíková et al. 2017). The vast majority of ditrysian species, however, retained the W chromosome. ...
Article
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Moths and butterflies (Lepidoptera) are the most species-rich group of animals with female heterogamety, females mostly having a WZ, males a ZZ sex chromosome constitution. We studied chromatin conformation, activity, and inactivity of the sex chromosomes in the flour moth Ephestia kuehniella and the silkworm Bombyx mori, using immunostaining with anti-H3K9me2/3, anti-RNA polymerase II, and fluoro-uridine (FU) labelling of nascent transcripts, with conventional widefield fluorescence microscopy and ‘spatial structured illumination microscopy’ (3D-SIM). The Z chromosome is euchromatic in somatic cells and throughout meiosis. It is transcriptionally active in somatic cells and in the postpachaytene stage of meiosis. The W chromosome in contrast is heterochromatic in somatic cells as well as in meiotic cells at pachytene, but euchromatic and transcriptionally active like all other chromosomes at postpachytene. As the W chromosomes are apparently devoid of protein-coding genes, their transcripts must be non-coding. We found no indication of ‘meiotic sex chromosome inactivation’ (MSCI) in the two species.
... The North American coniferophagous Choristoneura have long been regarded as a complex of species. Over the last five decades, many studies have been conducted in efforts to delineate species on the basis of morphological (Freeman 1967;Harvey and Stehr 1967;Dang 1985Dang , 1992De Benedictis 1995;Lumley and Sperling 2010), behavioral (Harvey 1967;Silk and Kuenen 1988;Sanders and Lucuik 1992), and genetic traits (Ennis 1976;Hickey 1994, 1995;Harvey 1996aHarvey , 1996bLumley and Sperling 2010), and to determine phylogenetic relationships (Harvey 1985;Dang 1992;Hickey 1994, 1995;De Benedictis 1995;Powell and De Benedictis 1995a;Willett 2000;Lumley and Sperling 2010, 2011a, 2011b. Currently, there are eight recognized species in this coniferophagous group (Harvey 1967(Harvey , 1985Powell 1995). ...
Article
Tetropium fuscum (F.), native to Europe and established in Nova Scotia, Canada, since at least 1990, is considered a low-to-moderate threat to spruce (Picea spp.) forests in North America and regulated as a quarantine pest by the Canadian Food Inspection Agency. We tested broadcast applications of the aggregation pheromone racemic (5E)-6,10-dimethyl-5,9-undecadien-2-ol (fuscumol), formulated at 10% concentration in Hercon Bio-Flakes (Hercon International, Emigsville, PA), for efficacy in disrupting T. fuscum mating and suppressing populations. Two applications of 2.5-2.75 kg Bio-Flakes (250-275 g a.i.) per ha per season significantly reduced trap catches and mating success (2009, 2010, 2012): about 30% of females trapped in treated plots had mated compared with 60% of females trapped in untreated plots. Similar reductions in mating success were observed in 2011 with one or two 4.5 kg/ha applications of Bio-Flakes. Mean densities of T. fuscum colonizing sentinel bait logs or girdled trees were 36% lower in pheromone-treated plots than in untreated plots, but the difference was not statistically significant. Lack of population suppression may have been because mated females immigrated into treated plots or because populations were so high that despite a 50% reduction in mating success, absolute numbers of mated females were sufficient to infest our bait logs or trees. This is the first demonstration of insect mating disruption via broadcast application of an aggregation pheromone. Pheromone-mediated mating disruption has potential to slow the spread of invasive cerambycids by targeting low-density outlier populations near or beyond the leading edge of an infestation.
... egg weight; Harvey, 1997). Several authors have reported initial evidence for genic or chromosomal differentiation that might lead to genetic incompatibilities underlying the evolution of intrinsic reproduction isolation (Campbell, 1958;Ennis, 1976;Harvey, 1997Harvey, , 1983aHarvey, ,b, 1985b. Nonetheless, published findings on fertility, combined with limited genetic divergence found in our study, suggest that intrinsic barriers among the three study taxa are probably low in nature. ...
Article
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Species delimitation requires an assessment of varied traits that can contribute to reproductive isolation, as well as of the permanence of evolutionary differentiation among closely related lineages. Integrative taxonomy, including the combination of genome-wide molecular data with ecological data, offers an effective approach to this issue. We use genotyping-by-sequencing together with a review of ecological divergence to assess the traditionally recognized species status of three closely related members of the spruce budworm species complex, Choristoneura fumiferana (Clemens), C. occidentalis Freeman (=C. freemani Razowski) and C. biennis Freeman, each of which is a major defoliator of conifer forests. We sampled a broad region of overlap between these three taxa in Alberta and British Columbia (Canada) where potential for gene flow provides a strong test of the durability of divergence among lineages. A total of 2218 single nucleotide polymorphisms (SNPs) were assayed, and patterns of differentiation were evaluated under the biological, ecological, genotypic cluster and phylogenetic species concepts. Choristoneura fumiferana was genetically distinct with substantial barriers to genetic exchange with C. occidentalis and C. biennis. Conversely, divergence between C. occidentalis and C. biennis was limited to a small subset of outlier loci and was within the range observed within any one of the taxa. Considering both population genetic and ecological patterns of divergence, C. fumiferana should continue to be recognized as a distinct species, and C. biennis (syn.n.) should be treated as a subspecies (C. occidentalis biennis Freeman, 1967) of C. occidentalis, thereby automatically establishing the nominate name C. occidentalis occidentalis Freeman, 1967 for univoltine populations of this species.
... The haploid chromosome number of T. absoluta was n = 29, which is in agreement with previously reported modal haploid chromosome numbers found in Gelechiidae (Lukhtanov & Puplesiene 1999). The presence of a very large bivalent in the diploid complement is also a typical trait of this lepidopteran family (Beliajeff 1930;Ennis 1976;LaChance & Ruud 1979;Bedo 1984;Lukhtanov & Kuznetsova 1988;Bartlett & Del Fosse 1991;Lukhtanov & Puplesiene 1999). In T. absoluta, this large pair of chromosomes proved to be the WZ sex chromosome bivalent (present work). ...
Article
The tomato leafminer, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is one of the most important pests of tomato. With the purpose of developing environmentally friendly control tactics such as the inherited sterility (IS) technique against this species, it is essential to understand its genetics and biology. In this paper we analyzed the karyotype, sperm morphology and sperm ratio in wild-type and X-ray irradiated individuals of T. absoluta. The diploid chromosome number of T. absoluta was 2n = 58 including the pair of sex chromosomes: ZZ in males and WZ in females, which were the largest elements of the complement. Irradiation of pupae in an X-ray machine with a dose of 200 Gy generated various types of chromosomal rearrangements including translocations and fragmentations, resulting in altered chromosome numbers. The analysis of spermatozoa in T. absoluta revealed a significant morphological difference between apyrene and eupyrene sperm bundles. Irradiation with X-ray doses of 100, 150, 200 and 250 Gy did not have a significant effect on the apyrene to eupyrene sperm ratio. However, males irradiated with 300 Gy produced significantly more apyrene sperm than non-irradiated males. All the doses applied influenced the morphology of eupyrene sperm bundles. The modified eupyrene sperm bundles could be used as a bioindicator during the monitoring of an IS program after the release of irradiated males. We found that the modified eupyrene spermatozoa were transferred to the bursae copulatrices of the females. Males treated with 200 Gy transferred a greater proportion of modified eupyrene sperm than untreated males. The results presented herein provide essential information on the cytology of T. absoluta, which is required to evaluate the quality of the released insects, and for better understanding and application of IS against this economically important pest.
... The observed chromosome numbers of Idaea aversata and Pygospila tyres also differ from earlier reports on the chromosome numbers in other members of their families e.g., Geometridae and Crambidae, respectively. Suomalainen (1965) and Ennis (1976) have reported the haploid chromosome number as thirty (n=30) and sixty-one (n=61) in Cidaria sp. and Nepytia canosaria of the family Geometridae, respectively. Pygospila tyres is the member of the family Crambidae. ...
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Moths belonging to the order Lepidoptera have high numbers of small-sized chromosomes which are holocentric. The modal chromosome number in Lepidoptera ranges from n=29 to n=31 but variations have also been found. This order has two types of sex determination systems: (i) WZ ♀; ZZ ♂ and (ii) OZ ♀; ZZ ♂. Lepidopterans are the subject of great interest because of the pest status of many of its species. The present work was undertaken to study the chromosomes of the following moth species from Himachal Pradesh: Cnaphalocrocis medinalis G., Euproctis chrysorrhoea L., Idaea aversata L., and Pygospila tyres C. The haploid chromosome numbers observed in C. medinalis, E. chrysorrhoea, I. aversata, and P. tyres were 30, 31, 26, and 28, respectively. The karyotypes of all the species showed holocentric chromosomes. A long pair of chromosomes was found in the karyotype of all species. Other chromosomes showed a gradual decrease in size or were almost of the same size.
... In meiotic metaphase, 26 bivalents were observed both in males and females, demonstrating that the haploid karyotype of T. varians consists of n = 26 chromosomes. Sucking stomachs were prepared and inspected for the presence or absence of SB, which has been deduced to be composed of condensed W chromosomes (Ennis 1976; Traut and Marec 1996). In females, each nucleus displayed a single, spherical heterochromatin body (Figure 6A). ...
Article
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This study describes the molecular phylogeny, laboratory rearing, and karyotype of a bombycid moth, Trilocha varians (F. Walker) (Lepidoptera: Bombycidae), which feeds on leaves of Ficus spp. (Rosales: Moraceae). The larvae of this species were collected in Taipei city, Taiwan, and the Ryukyu Archipelago (Ishigaki and Okinawa Islands, Japan). Molecular phylogenetic analyses revealed that T. varians belongs to the subfamily Bombycinae, thus showing a close relationship to the domesticated silkworm Bombyx mori (L.), a lepidopteran model insect. A laboratory method was developed for rearing T. varians and the time required for development from the embryo to adult was determined. From oviposition to adult emergence, the developmental zero was 10.47 °C and total effective temperature was 531.2 day-degrees, i.e., approximately 30 days for one generation when reared at 28 °C. The haploid of T. varians consisted of n = 26 chromosomes. In highly polyploid somatic nuclei, females showed a large heterochromatin body, indicating that the sex chromosome system in T. varians is WZ/ZZ (female/male). The results of the present study should facilitate the utilization of T. varians as a reference species for B. mori, thereby leading to a greater understanding of the ecology and evolution of bombycid moths.
... This is probably due to the high modal number (n = 30-31) and small size of lepidopteran chromosomes, their resistance to C-banding procedures, and the preference of researchers for the easily accessible male meiotic metaphases. The presence of sex chromatin bodies, however, indicates the presence of W chromosomes in females of the majority of lepidopteran species (ENNIS 1976;TRAUT and MOSBACHER 1968). ...
Article
Synaptonemal complexes (SCs) of pachytene bivalents from oocytes and spermatocytes of the wax moth, Galleria mellonella, were studied with a microspreading technique. In both sexes 30 bivalents were found. Male SCs in contrast to female SCs contained recombination nodules. No specific bivalent could be recognized in male complements. In female complements, the WZ bivalent was recognized among the three longest bivalents by its delayed pairing and/or unequal lengths of the lateral elements. Pairing of WZ bivalents is complete and lateral elements are nearly equalized in a few cells, presumably at the end of pachytene.
... Since the species descriptions of Freeman (1967), many studies have attempted to resolve the taxonomy of the spruce budworm complex using characters from genitalia (Dang, 1985Dang, , 1992), eggs (Harvey, 1983Harvey, , 1997), larval, pupal and adult colour (Volney et al., 1983Volney et al., , 1984), adult forewing and hindleg basitarsal spine length (), pheromone attraction (e.g. Sanders, 1971; Sanders et al., 1977; Silk & Kuenen, 1988; Powell, 1995), larval host association (Volney et al., 1984; Powell & De Benedictis, 1995), sex chromatin and chromosome numbers (Ennis, 1976), allozymes (Castrovillo, 1982; Harvey, 1996) and mtDNA (Sperling & Hickey, 1994). The most recent bibliography of C. fumiferana, although published over 20 years ago (McKnight et al., 1988), cited 4318 reports and papers mentioning some aspect of the biology of the spruce budworm species complex – clearly effective species identification for this group would serve a diversity of forestry and basic research needs, and help to focus taxonomic efforts for other such complexes. ...
Article
Species in cryptic complexes tend to be very difficult, if not impossible, to identify using morphological characters. One such complex is the spruce budworm (Choristoneura fumiferana Clemens, 1865) species group, an economically important group of Nearctic forest pests. Morphological, ecological, behavioural and genetic characters have been studied to try to understand the taxonomy of this group better, but diagnostic character states differ in frequency rather than being complete replacements between each species. We used mitochondrial DNA (mtDNA), together with a new morphology-based character system that focuses on forewing colour components, to determine if one or a combination of character sources can be used for species diagnoses within the spruce budworm complex. We characterized 47 forewing morphometric measurements and sequenced a 470 bp region of cytochrome c oxidase I mtDNA for 111 ingroup individuals comprising five taxa within the complex. Larval host association and coloration or adult pheromone attraction were used as the prior method for grouping individuals. Our results showed that linear discriminant analysis of morphometric wing characters gave unique clusters for all species on the first and second canonical axes, except for a partial overlap between C. fumiferana and C. biennis, which are not sympatric in nature. In contrast, mtDNA distinguished C. fumiferana, C. pinus pinus Freeman, 1953 and a group of western species, but the three western species (C. occidentalisFreeman, 1967, C. biennisFreeman, 1967 and C. lambertiana Busck, 1915) shared mtDNA haplotypes. On the basis of the linear discriminant analysis of the combined character set, this study supports the application of both morphology and mtDNA within a framework of integrative taxonomy as the most accurate method for species identification. Furthermore, it demonstrates the utility of quantitative colour analysis, which may be particularly helpful for groups in which colour characters are difficult to divide into discrete units due to intergrading hues.
... Extensive taxonomic effort has been invested in delimiting and identifying species and biotypes within the spruce budworm complex. Taxonomic studies have included morphology for every stage of development (Dang, 1985(Dang, , 1992De Benedictis, 1995;Freeman, 1967;Harvey, 1983;Harvey and Stehr, 1967;Lumley and Sperling, 2010;MacKay, 1953MacKay, , 1962Volney et al., 1983Volney et al., , 1984, behavioural traits (Harvey, 1967(Harvey, , 1997Powell, 1995;Powell and De Benedictis, 1995;Shepherd et al., 1995;Silk and Kuenen, 1988;Stehr, 1967;Volney et al., 1984), ecogeographical characteristics (Shepherd et al., 1995;Stehr, 1967), and genetic characters (Castrovillo, 1982;Ennis, 1976;Harvey, 1996;Lumley and Sperling, 2010;Sperling andHickey, 1994, 1995). Yet, these species (and subspecies) remain difficult to identify because their defining characters differ in frequency rather than being complete character replacements (Dang, 1992;Harvey, 1985Harvey, , 1997. ...
Article
Species identifications have been historically difficult in the Choristoneura fumiferana group, an important insect pest complex. We examined the utility of simple sequence repeats (SSRs, also referred to as microsatellites) and mitochondrial DNA (mtDNA) for delimiting and identifying eight currently recognized species sampled across North America. Four of these species formed discrete clusters using SSRs, while only two species were delimited with mtDNA. There was evidence for hybridization or incomplete lineage sorting between several species pairs. An integrative approach, using both phenotypic traits and molecular markers, allowed for the discrimination of more biologically relevant species units than did the use of molecular markers alone. As species are currently identified using putatively adaptive phenotypic traits, the differences observed between recognized species and neutral SSRs or mtDNA suggests that these species (or evolutionary significant units) have diverged via natural selection in spite of some gene flow.
... Sex linkage of other allozymes in these species has not yet been investigated . At the cytological level many tortricids have a haploid chromosome number of n 30, with the one believed to be the sex chromosome visibly larger than the rest ( Ennis 1976; Smith 1944; Suomalainen 1971). This contrasts with the situation in H. virescens (Chen and Graves 1970) and most noctuids (Robinson 1971) in which n 31 and the chromosomes are more nearly equal in size. ...
Article
The noctuid moth Heliothis virescens is a significant pest of several crops including cotton, where the predominant control method relies on chemical insecticides. In the 1970s H. virescens became highly resistant to the organophosphorus insecticide methyl parathion. Organophosphorus and carbamate insecticides inhibit the enzyme acetylcholinesterase (AChE) by binding to the active site, and one mechanism of resistance is an altered AChE insensitive to this inhibition. We characterized Acein , an autosomal locus controlling AChE insensitivity in H. virescens , and mapped it to linkage group 2. This is the first linkage assignment for a gene conferring insecticide resistance in a lepidopteran. The apparent translocation of this autosome to the sex chromosome in many species of the family Tortricidae leads to the prediction that if organophosphorus resistance due to target-site insensitivity occurs in these tortricids, it should be sex linked. This prediction is novel because sex-linked insecticide resistance genes are rare among insects.
Article
The meiotic stages in males and females of Trabala vishnu Lef. were studied using in vitro colchicine treatment and C-banding. In the females, meiosis was achiasmatic. The sex chromosomes were associated in a trivalent (AAWZ) consisting of a W-chromosome translocated onto an autosome to form an AW chromosome, paired with the homologous autosome and the Z-chromosome. In the homogametic males, the two Z-chromosomes paired in the usual manner. The females had 24 autosomal bivalents and a sex trivalent in meiosis, whereas the males had 26 bivalents, including a sex bivalent. The intensely C-banded W-chromosome was confirmed at pachytene, and was the longest element in the trivalent. Karyotypes prepared from female somatic metaphases of brain ganglia revealed 2n = 51 with the heteromorphic sex chromosome pair ZW, while the male karyotypes (2n = 52) showed a homomorphic ZZ sex chromosome pair. It may be that the primary step in the differentiation of sex chromosomes was the concentration of highly repetitive DNA sequences, i.e. heterochromatinization in the W-chromosome, which preceded morphological differentiation of heteromorphic sex chromosomes.
Article
Although a monophyletic group, male (XX/XY) and female heterogametic (WZ/ZZ) sex chromosome systems with a couple of variants like XX/X, Z/ZZ and multiple sex chromosome systems occur in insects. Molecular and morphological differences between X and Y or W and Z range from imperceptible to conspicuous. This article illustrates sex chromosome differentiation mainly in two fly species, Drosophila melanogaster and Megaselia scalaris, and in Lepidoptera. The earliest phases of XY evolution are present in the fly M. scalaris. Occasionally in this species, the male determining gene jumps to another chromosome, transforming the new host chromosome to a functional Y chromosome. Thus, in M. scalaris there are strains with virtually no XY differentiation (except for the sex determining function) and others with a moderate degree of differentiation. Base substitutions and alterations like sequence deletions, duplications, and insertions of mobile sequences mark the onset of molecular differentiation. Accumulation of molecular changes and coarser alterations are thought to lead to the morphological differences seen in WZ chromosome pairs of Lepidoptera. The W chromosome probably evolved in the most numerous clade of Lepidoptera, the Ditrysia, after it diverged from the common lepidopteran stem. Extant species display various degrees of molecular and morphological differentiation of the W chromosome, translocation or fusion with autosomes, and loss of the W.
Article
Laboratory studies of seven North American Choristoneura species and two subspecies from widely distributed locations demonstrate the low level of genetic separation among them. No differences were found in numbers (n = 30) or morphology of chromosomes among members of the group or in any of the hybrids examined. High levels of mating success were obtained in all inter se matings as well as in crosses and back-crosses. However, mating success was greater for crosses within host type and within pheromone type than for crosses between types. Viability and fertility were similar in all the hybrids and close to those of the inter se progenies. Mean weights of initial eggs varied by a factor of 2 from the lowest (C. pinus Freeman) to the highest (C. lambertiana ponderosana Obraztsov). Mean weights of initial eggs produced by hybrids were generally close to those of the parental species. However, when one parent was C. fumiferana (Clem.), mean weights of initial eggs were either much larger (male C. fumiferana) or much smaller (female C. fumiferana) than either parental type. These differences could affect survival of some progeny under harsh conditions. This evidence supports other studies in indicating that C. fumiferana is genetically distinct from other species in this group.
Article
Testicular development and spermatogenesis were studied in Boarmia selenaria Schiff. Testicular size increased rapidly during larval life and diminished continually thereafter. There was a close relationship between the age of the insect and the progress of spermatogenesis. The chromosome number was found to be n = 31. The sex chromatin body was observed only in female tissues.
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Moths of the family Tortricidae constitute one of the major microlepidopteran groups in terms of species richness and economic importance. Yet, despite their overall significance, our knowledge of their genome organization is very limited. In order to understand karyotype evolution in the family Tortricidae, we performed detailed cytogenetic analysis of Grapholita molesta, G. funebrana, Lobesia botrana, and Eupoecilia ambiguella, representatives of two main tortricid subfamilies, Olethreutinae and Tortricinae. Besides standard cytogenetic methods, we used fluorescence in situ hybridization for mapping of major rRNA and histone gene clusters and comparative genomic hybridization to determine the level of molecular differentiation of the W and Z sex chromosomes. Our results in combination with available data in the codling moth, Cydia pomonella, and other tortricids allow us a comprehensive reconstruction of chromosomal evolution across the family Tortricidae. The emerging picture is that the karyotype of a common ancestor of Tortricinae and Olethreutinae differentiated from the ancestral lepidopteran chromosome print of n = 31 by a sex chromosome-autosome fusion. This rearrangement resulted in a large neo-sex chromosome pair and a karyotype with n = 30 conserved in most Tortricinae species, which was further reduced to n = 28 observed in Olethreutinae. Comparison of the tortricid neo-W chromosomes showed differences in their structure and composition presumably reflecting stochasticity of molecular degeneration of the autosomal part of the neo-W chromosome. Our analysis also revealed conservative pattern of the histone distribution, which is in contrast with high rDNA mobility. Despite the dynamic evolution of rDNA, we can infer a single NOR-chromosome pair as an ancestral state not only in tortricids but probably in all Lepidoptera. The results greatly expand our knowledge of the genome architecture in tortricids, but also contribute to the understanding of chromosomal evolution in Lepidoptera in general.
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Eleven representatives of the superorder Amphiesmenoptera (Trichoptera + Lepidoptera) were examined for sex chromatin status. Three species represent stenopsychoid, limnephiloid and leptoceroid branches of the Trichoptera; eight species belong to the primitive, so-called nonditrysian Lepidoptera and represent the infra-orders Zeugloptera, Dacnonypha, Exoporia, Incurvariina, Nepticulina and Tischeriina. The female-specific sex chromatin body was found in the interphase somatic nuclei of Tischeria ekebladella (Bjerkander 1795) (Lepidoptera, Tischeriina). The sex chromatin was absent in all investigated Trichoptera species as well as in all representatives of the nonditrysian Lepidoptera except Tischeria ekebladella. The sex chromosome mechanism of Limnephilus lunatus Curtis 1834 (Trichoptera, Limnephilidae) is Z/ZZ. The sex chromosome mechanism of Tischeria ekebladella (Lepidoptera, Tischeriina) is ZW/ZZ including the W chromosome as the largest element in the chromosome set. The data obtained support the hypothesis that the Z/ZZ sex chromosome system, the female heterogamety and the absence of the sex chromatin body in interphase nuclei are ancestral traits in the superorder Amphiesmenoptera. These ancestral characters are probably kept constant in all the Trichoptera and in the most primitive Lepidoptera. The W sex chromosome and the sex chromatin evolved later in the nonditrysian grade of the Lepidoptera. It is proposed that the sex chromatin is a synapomorphy of Tischeriina and Ditrysia.
Article
Cytological investigations in forty-five species of Indian moths belonging to ten families (Tinaeidae, Limacodidae, Thyrididae, Pyralididae, Lasiocampidae, Saturnidae, Sphingidae, Noctuidae, Lymantriidae, Hypsidae) of Lepidoptera revealed haploid chromosome numbers varying from 12 to 31, the latter number being predominant (in 26 species). Their haploid chromosome numbers at metaphase I and II are stated in a table.
Article
The chromosome number in males of Antheraea compta (Wild) and A. assamensis (semi-domesticated) is 30, while in females it is 30 (XY) in A. compta and 29 (XO) in A. assamensis, the latter concomitantly does not reveal sex chromatin in interphase nuclei of both somatic and germ cells. This confirms that the Y chromosome, which forms the sex chromatin in females of A. compta, has been lost in the other species. Meiosis in males shows discrete chiasmata while in females of both species it is achiasmatic. Meiotic details of the species are given and the evolutionary inter-relationship is discussed.
Article
Structural mutants of the W chromosome that are kept in laboratory strains are described using light and electron microscopic techniques. The series comprises a translocation, a deficiency, fusions, and W fragments. — Conclusions drawn from the mutants are the following: At least one half of the W serves no vital function and is dispensable. Female sex determination, if the W is involved at all, rests on the other half. The amount and form of heterochromatin in somatic interphase nuclei depends on the amount and location of the W chromosome material. The W inactivation in somatic cells does not spread to attached autosomal segments.
Article
Genetic sexing technique based on the construction of a balanced lethal strain (BLS) has been proposed for Phthorimaea operculella (Zeller). The isolation of female with T(W;Z) translocation is a fundamental step to develop such a strain. Gamma irradiation was used to induce the requested translocations. The availability of sex-linked morphological marker is required to facilitate the detection of such mutations. Since a visible sex-linked marker has not been found in P. operculella, the main objective of our study was therefore to determine the possibility of using sex heterochromatin body as a marker to identify the required translocated females. The appearance of sex heterochromatin body and the analysis of sex chromosomes in F1 females of irradiated P. operculella females were investigated. The percentage of abnormality in sex heterochromatin body in highly polyploid Malpighian tubule nuclei was positively correlated with the applied dose. Based on the appearance of this body, three mutant lines were isolated: elongated, small and fragmented lines. W chromosome was easily distinguished from Z chromosome when the analysis of pachytene sex chromosome bivalents of P. operculella females was carried out. The aberrations involved in W chromosome directly influenced the appearance of sex heterochromatin body in highly polyploid somatic cells of the isolated mutant lines. The results showed that sex heterochromatin could be used as sex determination and cytogenetic marker in P. operculella.
Article
The female-specific heterochromatin (W chromatin) is derived from the W chromosome. It forms a single sphere in highly polyploid somatic tissues of the wild-type strain of the flour moth Ephestia kuehniella. This heterochromatin sphere consists of chromatin of a high but not uniform electron density. It contains multiple cavities and has a rather smooth outer surface. The W chromatin is well delimited from the remaining chromatin of the nucleus. Thus, probably the whole W chromosome is heterochromatic in these tissues. This assumption is confirmed by the study of strains with mutant W chromosomes. In these mutants a whole autosome is translocated to the W chromosome. The W chromatin in highly polyploid cells of these strains is split up into several bodies with a rugged surface. Cytophotometric measurements of polyploid nuclei up to values of 1000C show the DNA of the W chromatin to increase proportionally to the total DNA of the cell and to contain 3% of the total nuclear DNA. The DNA concentration is 3–8 times higher in the W chromatin than in the rest of the nucleus. As can be seen in autoradiography experiments with [3H]thymidine, replication of the W chromatin DNA is out of phase with the remaining chromatin. Using autoradiography of short-term [3H]uridine incorporation as a measure for transcriptional activity, no such activity could be detected in the female specific heterochromatin. This means that the whole W chromosome, or at least most of it, is heterochromatic and transcriptionally inactive in somatic tissues. However, there are indications that this inactivation is specific for somatic tissues while in the previtellogenetic oocyte of the adult ovary the W chromosome is transcriptionally active.
Article
Chromosome number and morphology have been examined in four established cell lines (Md63, Md66, Md108, and Md109) of the forest tent caterpillar, Malacosoma disstria Hübner, and one (Cf124) of the spruce budworm, Choristoneura fumiferana (Clemens). Chromosome number distributions of Md63 (mode = 112) Md108 (mode = 103), Md109 (mode= 103), and Cf124 (mode = 110) overlap sufficiently to prevent identification of individual lines by number alone. However, Md66 is exceptional in possessing a modal number of 157. One large chromosome occurs in cells of all lines. The presence of this chromosome, the lack of any distinct polyploid series among chromosome numbers encountered, and the general inverse relationship between number and size of chromosomes, suggest that the high level of heteroploidy characteristic of these and other lepidopteran cell lines reflects not only a possible polyploid origin but also extensive chromosomal rearrangement and fragmentation. Tolerance for such change is attributed to the holokinetic organisation of lepidopteran chromosomes. A distinct heteropycnotic body is present in about 10% of Cf124 cell nuclei, and can be used as a marker for this line. This body may represent the sex chromatin normally encountered in somatic cells of female C. fumiferana.
Article
Sex chromosome morphology of eight Lepidoptera species was studied, exploiting predominantly the pachytene stage when chromosomes display a remarkable chromomere pattern. Six species had a WZ/ ZZ sex chromosome system, one species a W1W2Z/ ZZ system and one species was of the Z/ZZ type. Much like XY chromosomes in groups with male heterogamety, the lepidopteran sex chromosomes showed various degrees of structural differentiation. Differences between Z and W chromomere patterns ranged from undetectable to obviously non-homologous. A common property of the W chromosomes (the W1 in the W1W2Z/ZZ system) was the possession of a block of heterochromatin. The heterochromatin block comprised a small or a large segment of the W or even the entire W, depending on the species. Segments with apparent structural homology are evolutionarily young parts of the sex chromosomes-recently fused autosomes that have not had sufficient time for differentiation. The 'primitive' lepidopteran species Micropterix calthella had a Z/ZZ sex chromosome system. This supports the hypothesis that the lepidopteran W chromosome came into being at the base of the 'advanced' Lepidoptera; it was presumably an autosome whose homologue fused to the original Z chromosome.
Article
We have discovered an inordinately large chromosome pair at the pachytene stage in the oocyte of the sex-limited pB (black larval marking) silkworm (Bombyx mori) strain (TWPB). We have analyzed the composition and arrangement of this large chromosome. A genetic linkage analysis shows that the large chromosome is made up of the W chromosome, the second chromosome fragment (pB fragment), and the fifth chromosome (linkage group) containing at least the region from map position 0.0 to 40.8. We also observed a sex heterochromatin body (SB) that we deduced to be made up of condensed W chromosomes. The number of SBs in each female nucleus among the sucking stomach cells of the TWPB strain was variable. Evidently, the W chromosome of the TWPB strain is attached to another chromosome. The composition of the W chromosome, the second chromosome fragment, and the fifth chromosome was studied through linkage analysis for these three chromosomes. We used two strains derived from the TWPB strain, the sex-limited pM (moricaud larval marking)-like (TWPML) and the autosomal pM-like (T5PML). The results show that the TWPML strain originates through a detachment of the fifth chromosome from the large chromosome of the TWPB strain, and the T5PML strain originates through a detachment of the W chromosome from that. Accordingly, the large chromosome of the TWPB strain is arranged in the order W chromosome--second chromosome fragment--fifth chromosome.
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The W chromosome of the silkworm Bombyx mori is devoid of functional genes, except for the putative female-determining gene (Fem). To localize Fem, we investigated the presence of W-specific DNA markers on strains in which an autosomal fragment containing dominant marker genes was attached to the W chromosome. We produced new W-chromosomal fragments from the existing Zebra-W strain (T(W;3)Ze chromosome) by X-irradiation, and then carried out deletion mapping of these and sex-limited yellow cocoon strains (T(W;2)Y-Chu, -Abe and -Ban types) from different Japanese stock centers. Of 12 RAPD markers identified in the normal W chromosomes of most silkworm strains in Japan, the newly irradiated W(B-YL-YS)Ze chromosome contained three, the T(W;2)Y-Chu chromosome contained six, and the T(W;2)Y-Abe and -Ban chromosomes contained only one (W-Rikishi). To investigate the ability of the reduced W-chromosome translocation fragments to form heterochromatin bodies, which are found in nuclei of normal adult female sucking stomachs, we examined cells of the normal type p50 strain and the T(W;2)Y-Chu and -Abe strains. A single sex heterochromatin body was found in nuclei of p50 females, whereas we detected only small sex heterochromatin bodies in the T(W;2)Y-Chu strain and no sex heterochromatin body in the T(W;2)Y-Abe strain. Since adult females of all strains were normal and fertile, we conclude that only extremely limited region, containing the W-Rikishi RAPD sequence of the W chromosome, is required to determine femaleness. Based on a comparison of the normal W-chromosome and 7 translocation and W-deletion strains we present a map of Fem relative to the 12 W-specific RAPD markers.
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The speciose insect order Lepidoptera (moths and butterflies) and their closest relatives, Trichoptera (caddis flies), share a female-heterogametic sex chromosome system. Originally a Z/ZZ (female/male) system, it evolved by chromosome rearrangement to a WZ/ZZ (female/male) system in the most species-rich branch of Lepidoptera, a monophyletic group consisting of Ditrysia and Tischeriina, which together comprise more than 98% of all species. Further sporadic rearrangements created multi-sex chromosome systems; sporadic losses of the W changed the system formally back to Z/ZZ in some species. Primary sex determination depends on a Z-counting mechanism in Z/ZZ species, but on a female-determining gene, Fem, in the W chromosome of the silkworm. The molecular mechanism is unknown in both cases. The silkworm shares the last step, dsx, of the hierarchical sex-determining pathway with Drosophila and other insects investigated, but probably not the intermediate steps between the primary signal and dsx. The W chromosome is heterochromatic in most species. It contains few genes and is flooded with interspersed repetitive elements. In interphase nuclei of females it is readily discernible as a heterochromatic body which grows with increasing degree of polyploidy in somatic cells. It is used as a marker for the genetic sex in studies of intersexes and Wolbachia infections. The sex chromosome system is being exploited in economically important species. Special strains have been devised for mass rearing of male-only broods in the silkworm for higher silk production and in pest species for the release of sterile males in pest management programs.
It has been known since 1924 that a proportion of females in the butterfly H. bolina produce only daughters, whereas others produce a 1:1 sex ratio. The present results confirm this, and show also that occasionally a few males are produced. The production of broods with a disturbed sex ratio is inherited entirely through the female line. By sexing the embryos and larvae cytologically and observing mortality in the embryos and late pupal stage we have obtained evidence that the deficiency of males is due to their very high mortality in the pre-adult stage. It is suggested that the abnormal sex ratio is due to an infective cytoplasmic factor (the presence of spirochaetes, as in Drosophila, having been ruled out), in contrast to Acraea encedon where meiotic drive of the Y chromosome has been postulated. The view is put forward that the polymorphism in H. bolina is maintained by the 'infected' females being at a slight disadvantage and that their numbers are maintained by contagion from an unidentified reservoir species.
Article
In four of the moth species investigated, viz. Witlesia murana, Scoparia arundinata (Pyraloidea), Bactra furfurana and B. lacteana (Tortricoidea) the metaphase plates of the first meiotic division of their oocytes show a trivalent in addition to the normal bivalents. It evidently has its rise in a transverse break in one of the conjugated chromosomes. Two sex chromatin bodies can be seen in the female somatic cells of three of these species, whereas other species with a normal XY bivalent have only one. These two sex chromatin bodies are unequal in size, and their sizes bear approximately the same relation to each other as do those of the two smaller chromosomes of the trivalent. The broken chromosome is evidently the Y chromosome. The sex chromosome designation for the four above-mentioned species is thus XY1Y2 for the females and XX for the males. The sex chromosomes of the four species are among the biggest of the respective complements. This supports the view that the big chromosome to be found in several Lepidoptera species is the sex chromosome. It seems that in animals with holokinetic chromosomes an excessive fragmentation is hindered, at least in the case of the sex chromosomes, by its deleterious effect on the balance of sex-determining genes.
Downloaded from www.nrcresearchpress.com by Duke University on 01/19/13 For personal use only. I 30 T
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197 1. Lepidcaptera genetics. Pergamon Press, Toronto. Smith, S. 6. 1945. The diagnosis of sex by means of heteropycnosis
  • R Robinson
Robinson, R. 197 1. Lepidcaptera genetics. Pergamon Press, Toronto. Smith, S. 6. 1945. The diagnosis of sex by means of heteropycnosis. Sci. Agric. 25: 566-57 1.
Abstract] [PDF] [PDF Plus] Can
  • T J Ennis
  • S S Sohi
  • Chromosomal Characterisation Of Five Lepidopteran Cell Lines Of Malacosoma Disstria
  • Lasiocampidae
  • And
  • Fumiferana
  • Tortricidae
T. J. Ennis and S. S. Sohi. 1976. CHROMOSOMAL CHARACTERISATION OF FIVE LEPIDOPTERAN CELL LINES OF MALACOSOMA DISSTRIA (LASIOCAMPIDAE) AND CHRISTONEURA FUMIFERANA (TORTRICIDAE). Canadian Journal of Genetics and Cytology 18:3, 471-477. [Abstract] [PDF] [PDF Plus] Can. J. Genet. Cytol. Downloaded from www.nrcresearchpress.com by Duke University on 01/19/13 For personal use only.