DOCSLIB.ORG

Sequential Analysis of Meiotic Prophase in Grasshoppers

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Sequential Analysis of Meiotic Prophase in Grasshoppers Cytologia 45:641-649, 1980 Sequential Analysis of Meiotic Prophase in Grasshoppers A. M. Vazquez, C. Martinez and J. R. Lacadena Departamentode Genetica,Facultad de Biologia UniversidadComplutense, Madrid, Spain ReceivedJanuary 9, 1979 Prophase meiotic stages of difficult interpretation, namely synizesis and diffuse stage, have been noted since early descriptions of meiosis (Wilson 1925 , Inouye 1929). The lack of chronology criteria which might establish a proper sequence of the observed phases has been, perhaps, one of the reasons which have made the under standing difficult. It has also made difficult to locate both stages within the meiotic cycle. In recent years, several criteria of chronology have come to be used which per mit the real establishment of the prophase meiotic stages. Moens (1964) was the first to give a new interpretation to the prophase I in which he included some atypi cal stages, namely synizesis, schizonema and diffuse stage. The synizesis, described as a stage in which homologous chromosomes appear paired forming a compact tangle, has been placed at the beginning of the prophase (Moens 1964, Nagl 1969, Lacadena and Vazquez 1971, Owens and Molder 1971). The diffuse stage is a period of apparent decondensation of the chromosomes previously paired and contracted. This stage has been reported by several authors and generally placed close to pachytene or diplotene (see review by Klasterska 1976). Its significance is still to be explained being connected with crossing over by some authors (Rossen and Westergaard 1966, Barry 1969, Peacock 1970) or with special periods of genetic activity by others (Lu and Raju 1970, Klasterska 1971, 1976, Owens and Molder 1971). In the present work, the sequence of the prophase I in the male meiosis of two genus of grasshoppers has been studied. The sequence was determined and the presence of a diffuse stage found. For this study longitudinal sections of testis tubu les were used showing the presence of a maturity gradient along the tubules. Material and methods Three species of the genus Chortippus (C. longicornis, C. apicalis and C. bicolor and one of the genus Oedipoda (O. coerulenses coerulenses) were used. No signi ficant differences were found in the process of spermatogenesis in the species studied, so that the results are set out together. All specimens were collected in autumn in the campus of the University. The testicles were extracted by dissection and fixed for six hours in Bouin's fixative. Next, they were washed in an alcohol series from greater to lesser grada tion, beginning with ethanol of 70•Ž down to distilled water. At this stage the sepa ration of tubules was carefully carried out. 642 A. M. Vazquez, C. Martinez and J. R. Lacadena Cytologia 45 After dehydratiation, the tubules were embedded in paraffin and 5,U longitudi nal sections were cut. A double acetic-carmine and fast-green staining was carried out. The former 10 minutes at 40•Ž and the latter a rapid pass through an alcoholic solution of fast green. The sections were made permanent mounted in Euparal. Results Each tubule was found to be divided into cysts, the number of which fluctuated from seven to twelve. The meiocytes belonging to a cyst arise from only one cell and they divide synchronouslly (King 1967). It was observed that a maturity gradient exist along the tubule in such a way that the distant cysts are found in an earlier stage of division than those situated in the proximate part. After having checked the existence of a maturity gradient in side the tubule, sequential studies of meiotic stages were carried out. After the cysts whose cells were spermatogonia in division or in a resting phase, others appeared with a bulky nuleus in their cells. In some of these cells the existence of loops coming out of the interior of the chromatin clew was observed. The double nature of the loops was established through the study of preparations made by squash because it was difficult to do so from the sections. Two parallel filaments were ob served leaving a clearly visible space between them. This phase was considered com parable to the synizesis (Fig. 1). Following the cysts whose nuclei were at synizesis, cysts at zygotene stage were found. The compactness of their nuclei was smaller, being possible to discern the double nature of the bivalents. After zygotene, cysts with normal appearence of pachytene stage were found. Following the pachytene cysts, and on same occasions appearing associated with that stage, one can find cells whose nuclei were very rounded, of great size, and completely filled by a fairly compact weft of filaments which resembled a net work. These cells showed a darker stain and the nucleolus was seen with difficulty (see Fig. 2). Sometimes nuclei could be seen which were interpreted as a tran sition between the pachytene nuclei and those previously described. In these, the chromosomes start losing their definite outline becoming diffused and losing their individuality. It can be considered these cells as being in a diffuse stage. As the meiosis advanced, cells appeared in which the chromosomes started to be seen again and the weft of filaments became less compact. It is a state which could be described as an emergence of the diffuse stage chromosomes toward diplotene chromosomes. At diplotene it is possible to distinguish the bivalents quite clearly as shorter structures in which the chiasmata are visible. On some occasions cysts showing both classic diplotene and diffuse stage cells were found (Fig. 2) With the appearance of cysts in diakinesis following the diplotene ones, the prophase I was completed. It was attempted to establish the relative duration of each phase in relation to 1980 Sequential Analysis of Meiotic Prophase in Grasshoppers 643 Table 1. Duration of each phase in relation to the total duration of the prophase I Figs. 1-2. 1, cyst showing meiocytes at synizesis. a, magnification •~3600. b, magnification. •~ 5800. 2, cyst showing meiocytes at diffuse (df) and diplotene (dp) stages. •~1650. 644 A, M. Vazquez, C. Martinez and J. R. Lacadena Cytologia 45 the total duration of the prophase I. Assuming that the number of cells per cyst is constant, a survey was made of the number of cysts occupied by each phase in rela tion to the number of cysts with cells in prophase I. The results are shown in the Table 1. Discussion The appearance of a maturity gradient along the seminal tubule of the male grasshoppers of the Chortippus and Oedipoda genera, permits us to use the cysts arrangements as a criterion of chronology in order to establish the proper sequence of the prophase I of these species. Based on this arrangement, we have established as the first phase the synizesis, a meiotic stage in which the homologous chromosomes appear apparently paired. This stage has been previously described by other authors and it was also placed at the beginning of meiosis (Swanson 1958, Moens 1964, Nagl 1969, Lacadena and Vazquez 1971, Owens and Molder 1971, Maguire 1972). The fact that in this phase the homologous chromosomes lay one beside another parallelly does not necessarily mean that this pairing is similar to that of pachytene as Moens (l.c.) suggested, but rather a close spatial arrangement which would allow the meiotic pairing with a greater facility since the homologous chromosomes would not be situated at random in the leptotene clew. This idea, previously suggested by Feldman (1966), was also indicated by Maguire (1972, 1974) who stated that, as a premeiotic homologous pairing exists, the synapsis during the meiotic prophase would require very little movement in relation to the diameter of the nucleus. Already in 1925 Wilson and in 1942 Smith referred to a pairing of homologous chromosomes in the last premeiotic telophase. Westergaard (1964) and Rossen and Westergaard (1966) also referred to a "precocious synapsis". More recent studies (Feldman 1966, Maguire 1968, Brown and Stack 1968, Chauman and Abel 1968, Stack and Brown 1969) support this hypothesis. In 1971, Stack studied the changes which were produced in the successive mitosis during the development of the plant Ornithogalum virens and defined them as premeiotic changes which gave the mito sis a gradual meiotic appearance, indicating that the homologous chromosome pairing, at least in this species, is a progressive phenomenon. We consider this hypo thesis of the premeiotic pairing to facilitate the synapsis and it is what really would explain the presence of the synizesis in the early prophase. It could be thought that the double structure observed in synizesis represents the two sister chromatids of one single chromosome instead of the two homologous chromosomes of one bivalent. If it were the real event it must be observed later the beginning of pairing, nevertheless one can see the same configuration in the fol lowing states although the chromosomes form a less compact mass. After the synizesis we situated the zygotene and later the pachytene. The pair ing continues increasing gradually from one to another, there not being possible to establish the presence of the schizonema stage as observed in other species (Moens 1964, Nagl 1969, Whelan and Hornby 1969, Lacadena and Vazquez 1971). As indicated in the results, the diffuse stage was located after pachytene. Never- 1980 SequentialAnalysis of Meiotic Prophase in Grasshoppers 645 theless, it is worth mentioning that cells at diffuse stage could appear together with pachytene cells in the same cyst. A similar situation was found with diplotene cells. These facts can be interpreted as the progressive changes from pachytene to diffuse stage or from diffuse to diplotene stages. Moreover the presence of nuclei with inter mediate aspect between the mentioned phases corroborates our interpretation. One can find plenty of references concerning this phase (see reviews by Klasterska 1976, 1977) although it does not always appear defined as such, but the descriptions given coincide with this stage.
Load more

Recommended publications
  • The Cytology of Tasmanian Short-Horned Grasshoppers ( Orthoptera: Acridoidea)
    PAP. & PROC. ROY. Soc. TASMANIA. VOL. 86. (15TH SEPTEMBER. 1952.) The Cytology of Tasmanian Short-Horned Grasshoppers ( Orthoptera: Acridoidea) By G. B. SHARMAN Department of Botany, University of Tasmania* WITH 1 PLATE AND 57 TEXT FIGURES SUMMARY The cytology of twenty-six of the twenty-nine species of short-horned grass­ hoppers (superfamily Acridoidea) recorded from Tasmania is described. Intra­ specific cytological polymorphism is described in some species. Cytological evidence of phylogenetic relationships has been indicated where possible. INTRODUCTION Mainly because of their large size, and general suitability for cyto­ logical study the chromosomes of the short-horned grasshoppers (super­ family Acridoidea) have been the subject of wide research. In the largest and most widely studied family, the Acrididae, early workers (McClung, 1905; Davis, 1908) reported the male number as being uniformly twenty­ three rod-shaped chromosomes, but Granata (1910) showed that Pam­ phagus possessed nineteen rod-shaped chromosomes. With few exceptions an XO sex chromosome sy~tem is found. Later work has shown that one group of subfamilies of the Acrididae is characterised by the male diploid number of· nineteen rod-shaped chromosomes, whilst another and larger group is characterised by the male diploid number of twenty-three. These are usually called the ten and twelve chromosome groups, and correspond to the Chasmosacci and Cryptosacci groups of subfamilies (Roberts, 1941). Cytologically the Chasmosacci is a very uniform group as has been shown by Rao (1937) and Powers (1942). The twelve chromosome group, how­ ever, has some cytological variability. In more than forty genera the characteristic male diploid chromosome number of twenty-three is found (White, 1945) ; but" centric fusions" (White, 1945) have been responsible for lowering the chromosome number of some species, although the characteristic twenty-three arms are still found.
    [Show full text]
  • Evidence of Premeiotic Control of Chromosome Pairing in Triticum Aestivum
    Genet. Res., Camb. (1972), 20, pp. 201-212 201 With 8 text-figures Printed in Great Britain Evidence of premeiotic control of chromosome pairing in Triticum aestivum BY M. W. BAYLISS* AND RALPH RILEY (Received 19 April 1972) SUMMARY A genotype of wheat deficient for a pair of chromosomes stabilizing chiasma frequency against extremes of temperature was investigated to determine the position and duration of temperature sensitivity with respect to first metaphase of meiosis. Temperature changes over a critical range, followed by sequential sampling and measurement of chiasma frequency, showed a relatively short temperature-sensitive stage, the position and duration of which were dependent on the final temperature used. Comparison with meiotic timings made independently showed that the temperature-sensitive stage occurred in the premeiotic interphase. Euploid wheat was shown to have a stage in chiasma forma- tion sensitive to high-temperature treatments at a similar time. Comparison with the work of others showed that the sensitive stage lay between the last premeiotic mitosis and the start of DNA synthesis. This modification of chromosome pairing at a much earlier stage than has been previously demonstrated is further evidence that the processes of chromosome pairing and crossing-over are probably more complex than formerly envisaged. 1. INTRODUCTION The pairing of chromosomes at meiosis is the necessary precursor of genetic recombination in higher organisms. This is emphasized by the good cytogenetic evidence now available that the chiasmata associating meiotic chromosomes represent structures that arise as a result of the events that also lead to genetic crossing-over (Lewis & John, 1965). However, there is little understanding of the nature, causes or control of meiotic pairing.
    [Show full text]
  • Ecological Status Near Thermal Power Plant and Jetty in Abdasa Taluka, Dist– Kutch Gujarat India
    International Journal of Avian & Wildlife Biology Research Article Open Access Ecological Status near thermal power plant and jetty in Abdasa Taluka, Dist– Kutch Gujarat India Abstract Volume 3 Issue 5 - 2018 The thermal power plant has major impact of hot water discharge in to nearby creek Ashok K Rathoure or into sea on its ecosystem. The baseline for avian biodiversity, marine ecosystem Ecology & Biodiversity Expert, Eco Chem Sales & Services; and terrestrial ecosystem has to be assessed before discharging the hot water into sea. Ecosystem Resource Management Pvt. Ltd., India We have assessed the terrestrial as well as marine ecosystem for baseline scenario near the thermal power plant in Abdasa taluka, Kutch Gujarat. In the present study, Correspondence: Ashok K Rathoure C/O Mr. Gyanendra K we have focused on terrestrial baseline status of ecological system of surrounding. Rathoure, Mayashivraj Sadan, Gupta Colony, Hardoi–241001, The findings state that area is not rich in biodiversity but mangrove biodiversity and (UP), India, Tel +91 9450501471, Email [email protected] density may be affected due to the thermal power plant activities. Received: August 26, 2018 | Published: October 02, 2018 Keywords: Avian biodiversity, mangrove, hot water discharge, impact, endangered species, thermal power plant Introduction this area. Due to unfavourable meteorological conditions and diverse habitat, a rapid snapshot survey for biological reconnaissance was The area in question has one thermal power plant running by Sanghi conducted in this case. Secondly, the activity rhythms of different Industries Limited and one Jetty (walkway accessing the centre of an species differ on a diurnal scale. For instance the rodents dwelling in enclosed water body or structure that projects from the land out into the sandy tracts of the buffer zone were seen despite being ubiquitous, water) structure built in 1994–1995 which is mainly used to Cement but leave unmistakable sole imprints of the hind paws on the sand.
    [Show full text]
  • 'Tasmanian Museum and Art Gallery's Expedition of Discovery I – the Flora
    Papers and Proceedings of the Royal Society of Tasmania, Volume 153, 2019 5 TASMANIAN MUSEUM AND ART GALLERY’S EXPEDITION OF DISCOVERY I – THE FLORA AND FAUNA OF WIND SONG, LITTLE SWANPORT, TASMANIA by Matthew Baker, Simon Grove, Miguel de Salas, Catherine Byrne, Lyn Cave, Kevin Bonham, Kirrily Moore and Gintaras Kantvilas (with 15 plates, two tables and an appendix) Baker, M.L., Grove, S., de Salas, M.F., Byrne, C., Cave, L., Bonham, K., Moore, K. & Kantvilas, G. 2019 (14:xii): Tasmanian Museum and Art Gallery’s Expedition of Discovery I – The flora and fauna of Wind Song, Little Swanport, Tasmania. Papers and Proceedings of the Royal Society of Tasmania 153: 5–30. https://doi.org/10.26749/rstpp.153.5 ISSN 0080–4703. Tasmanian Museum and Art Gallery, GPO Box 1164, Hobart, Tasmania 7001, Australia (MLB*, SG, MFS, CB, LC, KB, KM, GK). *Author for correspondence. Email: [email protected] A flora and fauna survey was conducted at the east coast Tasmanian property Wind Song in 2017 as part of the Tasmanian Museum and Art Gallery’s ongoing research, collection-building and nature-discovery program. The survey recorded 885 taxa, primarily from the targeted groups of vascular plants, bryophytes, lichens, butterflies, moths, beetles, snails and slugs. Several of the taxa recorded, chiefly lichens and invertebrates, are new to science or new records for Tasmania. The survey provides a benchmark for further work and serves as an indicator of the biodiversity of a former farming property on Tasmania’s east coast. Key Words: species discovery, biodiversity, Tasmania, lichens, multidisciplinary survey.
    [Show full text]
  • March 2010 Newsletter [PDF 2 MB]Orthopteran Overdose?!
    Garden for Wildlife Newsletter Alice Springs NT No. 30 February 2010 Wildlife News Big and small! Orthopteran Overdose?! They make the land come alive with every step, escorting you down the driveway in waves and clouds. They eat your vegies, but they feed the birds and lizards. Have patience! Remember the desert operates in ‘Boom and Bust’ cycles in response to rain. It has rained, plants and animals are ‘booming’. If there is no more rain over the next few months and things dry out, the ‘bust’ will begin and grasshopper populations will subside. So enjoy them while they last! As these grasshoppers mung into your citrus, have a close look at them. You may have already noticed the incredible variation. And there are crickets and katydids, mantids and stick insects amongst them. Here are a few orthopterans (grasshoppers, crickets and katydids belong to the Orthoptera Order) for you to try and identify: Grasshoppers Photo: The Leopard Grasshopper Holger Woyt Stropis maculosa The Toadhopper Family: ACRIDIDAE Buforania crassa Striking with its dark spots, the Leopard Grasshopper is commonly Family: ACRIDIDAE seen in a variety of habitats in Alice Springs. They are herbivourous, Sub-family: CATANTOPINAE however the native diet is contrary to the name, they don’t eat grass The Toadhopper is a plump Northern Territorian spur- as a first choice, they eat a variety of herbaceous plants including throated grasshopper. It can grow to at least 10cm long with your prized herbs, Caltrop, Boerhavia coccinea, citrus leaves, etc a thorax of around 3.5cm wide! It can be found on shellite or before they switch the grasses that are left over.
    [Show full text]
  • Of Evidence to Date Suggests That It Is the End-Product of an Interrelated A
    THE EFFECT OF X-IRRADIATION ON CHIASMA FREQUENCY IN CHORTHIPPUS BRUNNEUS M. WESTERMAN* Deportment of Genetics,Universityof Birmingham, England Received20.viii.70 1. INTRODUCTION THE formation of chiasmata during or immediately prior to pachytene in eukaryotic cells can no longer be thought of as an isolated event. The weight of evidence to date suggests that it is the end-product of an interrelated series of processes initiated at some earlier stage of meiosis, some or all of which can be affected by a variety of physical and chemical agents. In the desert locust, Schistocerca gregaria, Westerman (1967) has shown that following exposure of males to a single dose of X-rays there are three discrete periods at which chiasma frequency may be altered. Thus irradiation during the S.. phase of spermatogonial mitoses and during leptotene-early zygotene gave a significant increase in chiasma frequency when scored at diplotene- diakinesis. In contrast, an equal dose given during premeiotic DNA synthe- sis led to a significant decrease. These alterations in mean cell chiasma frequency in S. gregaria appear to be the result of alterations in the number of chiasmata formed by the long and medium bivalents only, the three small bivalents continuing to form a single chiasma under all conditions. Since the chromosomes of this species, though all telocentric, do not respond in the same way, it seemed worth while extending the study to another grasshopper species, Chorthippus brunneus (Thunb.)—one which includes metacentric as well as telocentric elements in its complement. 2. MATERIAL AND METHODS In the first of two duplicate experiments, 87 fifth instar and young adult male Chorthippus brunneus from a laboratory culture of animals originating from the wild were divided into three groups.
    [Show full text]
  • Evidence of Premeiotic Control of Chromosome Pairing in Triticum Aestivum
    Genet. Res., Camb. (1972), 20, pp. 201-212 201 With 8 text-figures Printed in Great Britain Evidence of premeiotic control of chromosome pairing in Triticum aestivum BY M. W. BAYLISS* AND RALPH RILEY (Received 19 April 1972) SUMMARY A genotype of wheat deficient for a pair of chromosomes stabilizing chiasma frequency against extremes of temperature was investigated to determine the position and duration of temperature sensitivity with respect to first metaphase of meiosis. Temperature changes over a critical range, followed by sequential sampling and measurement of chiasma frequency, showed a relatively short temperature-sensitive stage, the position and duration of which were dependent on the final temperature used. Comparison with meiotic timings made independently showed that the temperature-sensitive stage occurred in the premeiotic interphase. Euploid wheat was shown to have a stage in chiasma forma- tion sensitive to high-temperature treatments at a similar time. Comparison with the work of others showed that the sensitive stage lay between the last premeiotic mitosis and the start of DNA synthesis. This modification of chromosome pairing at a much earlier stage than has been previously demonstrated is further evidence that the processes of chromosome pairing and crossing-over are probably more complex than formerly envisaged. 1. INTRODUCTION The pairing of chromosomes at meiosis is the necessary precursor of genetic recombination in higher organisms. This is emphasized by the good cytogenetic evidence now available that the chiasmata associating meiotic chromosomes represent structures that arise as a result of the events that also lead to genetic crossing-over (Lewis & John, 1965). However, there is little understanding of the nature, causes or control of meiotic pairing.
    [Show full text]
  • Cytogenetic Studies in Calomys Musculinus(Rodentia, Cricetidae)
    _??_1988 by Cytologia, Tokyo Cytologia 53: 7-17 , 1988 Cytogenetic Studies in Calomys musculinus(Rodentia, Cricetidae) Marcelo Adriana Ciccioli Depto. Cs. Biologicas, Facultad de Ciencias Exactas y Naturales, (1428), Buenos Aires, Argentina Accepted December 11, 1986 The rodents of the genus Calomys are widely distributed in South America and many spe cies are represented in Argentina (Cabrera 1961). Among them, Calomys musculinus is one of the reservoirs of the "Arenavirus" agent of the Argentine Haemorrhagic Fever (Gardenal et al. 1977). The systematic position of some species of the group is not clear and brought about con troversies due to their morphological similitude. An example of this have been Calomys laucha and Calomys musculinus,which have often been described as only one species. Neverthe less, Massoia et al. (1968) confirmed C. musculinus as a good species based on studies of ex ternal characters, metric and craneal indexes, and chromosomic numbers. The mitotic karyotype, and the C and G bands have been described (Luna et al. 1979); the chromosomic numbers counted initially as 2n=38 for C. musculinusand 2n=64-62 for C. laucha (Massoia et al. 1968) were confirmed (Gardenal et al. 1977, Forcone et al. 1980, D'Aiutolo et al. 1981). Isoenzymatic studies (Gardenal et al. II, 1977) and research concerning the organi zation of the DNA in both species (Corach and Vidal Rioja 1982) were also carried out, pro ving in all the cases their distinctness. Based on the preliminary studies carried out on C. musculinus' meiosis (Ciccioli and Rahn 1984) the first stages of that process were analysed so as to observe and describe the diffuse stage, the frequency and distribution of chiasmata in relation to their possible terminalisation, and the formation of the synaptonemal complexes, in order to study the behavior of the sexual pair.
    [Show full text]
  • Gwambygine Pool Conservation Reserve
    Gwambygine Pool Conservation Reserve Fauna (macro-invertebrate and herpetofauna) Inventory Survey - 2009/10 ©David Knowles Spineless Wonders Fauna Surveys Prepared and published for the River Conservation Society York Western Australia with financial assistance from Wheatbelt Natural Resource Management. Cover Photograph: Common male Gwambygine Pool Damselfies (above) Blue Ringtail Lestidamselfly Austrolestes annulosus (centre) Redfront Coenadamselfly Xanthagrion erythroneurum (below) Aurora Bluetail Coenadamslefly Ischnura heterosticta Report David Knowles Design Fleur Knowles Spineless Wonders 08 9247 5772 [email protected] www.spinelesswonders.com.au CONTENTS Page Forward 4 Introduction 5 Maps and Pie Graph 9 Scope 12 Specimen preservation and collection 13 Voucher Specimen Lodgement 13 Interpretation aids 13 DEC Permit 13 Sampling Methods 14 Definitions 16 Site Subregion and Description 17 Plants of the Immediate Riparian Zone 18 Results - Ordinal Summaries and Tables 19 Conclusions 44 Recommendations 45 Acknowledgements 46 Web Resources 46 References 47 Interpreting The Tables – DefinitionsSymbols 48 Text And Abbreviations 48 MAIN TABLE APPENDIX 1 - 6 49 Table Appendix 7 - Table Of Commom Naming Codes 102 - 124 COLOUR SUPPLEMENT Spring (GREEN) 1 Summer (RED) 30 Autumn (GOLD) 58 Gwambygine Pool Conservation Reserve Fauna (macro-invertebrate and herpetofauna) Inventory Survey Forward It gives me a great deal of pleasure to present this Invertebrate Survey of Gwambygine Pool Conservation Reserve by David Knowles. The River Conservation Society commissioned David to carry out three surveys of the Reserve in September, October and November 2009 and in May 2010. The survey has revealed a rich diversity and abundance of the terrestrial invertebrate population in close proximity to Gwambygine Pool – a much greater abundance than had been expected.
    [Show full text]
  • Habitat Fragmentation and Its Effects on Birds and Grasshoppers in Eucalypt Remnants in the Tasmanian Midlands
    Habitat fragmentation and its effects on birds and grasshoppers in eucalypt remnants in the Tasmanian Midlands. by are") Michael MacDonald, BSc (hons Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy School of Geography and Environmental Studies Faculty of Science and Engineering University of Tasmania August, 2001 I declare that this thesis contains no material which has been accepted for a degree or diploma at the University or any other institution, except by way of background information and duly acknowledged in the thesis, and to the best of my knowledge and belief no material previously published or written by another person except where due acknowledgment is made in the text of the thesis. Michael MacDonald Date: zmo( II Authority of Access This thesis may be made available for loan and limited copying in accordance with the Copyright Act 1968 Michael MacDonald Date: V(710 ( Ill Abstract In the subhumid Midlands region of Tasmania, forty-seven remnants of eucalypt woodland and dry sclerophyll forest as well as six control sites were surveyed for birds and grasshoppers, in order to examine the responses of these groups to habitat fragmentation. A wide range of characteristics of the remnants (including position in landscape, management regime and vegetation) were related to species richness, diversity and density of the two groups as well as to the distributions of individual species. Remnant size, vegetation structure and tree health all showed significant relationships with bird species richness and diversity. Small remnants with open understorey and high levels of dieback showed radically different species composition than larger ones or those with dense understorey.
    [Show full text]
  • Kodak AR 10 Stripping Film) from Feulgen-Stained Squash Preparations of Testicular Material and These Were Allowed to Expose for 7 Weeks Before Processing
    THE ANALYSIS OF EXCHANGES IN TRITIUM-LABELLED MEIOTIC CHROMOSOMES 1. SCHISTOCERCA GREGARIA T. CRAIG-CAMERON and G. H. JONES Department of Genetics, University of Birmingham Received19.v.69 1. INTRODUCTION AUTORADIOGRAPHY following tritiated thymidine incorporation offers a new technique for the analysis of meiotic recombination. This method depends on the fact that germ line chromosomes, like those of somatic cells, show a semi-conservative segregation of labelled DNA in successive cell generations. Chromosomes which incorporate label in the pre-meiotic S phase enter meiosis with both chromatids labelled, while chromosomes labelled one cell cycle earlier, in the S phase of the last pre-meiotic cell cycle, enter meiosis having one labelled and one unlabelled chromatid. This pattern of partial labelling becomes modified due to the occurrence of re- combinational exchange events in meiotic prophase, and these determine the final labelling pattern of Anaphase 1 and Metaphase II chromosomes. This much has been established from earlier autoradiographic studies of the replication and recombination of meiotic chromosomes (Taylor, 1965; Callan and Taylor, 1968; Peacock, 1968; Church and Wimber, 1969). Evidently this method can be applied to the search for possible sister chrom- atid exchange (SCE) in meiotic cells as well as to the analysis of non-sister crossovers, and these were the two foremost aims of the present work. The potential of tritium autoradiography for the study of meiotic SCE has been explored in an earlier paper (Jones and Craig-Cameron, 1969). In the present report we present a more thorough analysis of the label segregation patterns in Schistocerca gregaria germ line chromosomes.
    [Show full text]
  • Molecular Studies of Homologous Chromosome Pairing in Triticum
    \ø\'r1 Itt' Molecular Studies of Homologous Chromosome Pairing tn Triticum aestivum by Stephen'W'. Thomas B. Ag. Sc. (Hons.) This thesís is presented for the degree of Doctor of PhilisoPhY in The Department of Plant Science Waíte Agricultural Research Institute The (Iniversity of Adelaide March 1997 ERRATA Page 11 - last paragtaPh, line 7 coñtrast to the Holliday "model" Page 15 - line 5 replace "shown to be" with "shown to @" Page23 - line 28 "initiation" Page25 - last paragraph, line 1 'þolycomplexes" Page26 - 3rd paragraph,line2 "extranuclear" Page 31 - 3rd paragraph,line 4 rep"lace "long är- õf the chromosome" with "long arm of chromosome 58" Page 35 - 2ndparagraph, line 11 "non-homologous" Page 35 - 2ndparagraph, line 14 rep"lace "Furthêrmoie in plants tri-isosomic 5BL plants" with "Furthermore in tri-isosomic 5BL plants" Page 35 -2ndparagraph,line 16 "intrachromosomal" Page 36 - 2ndparagraph, line I "non-random" Page 43 - line 2 "di ethylpyrocarb onate" Page 43 - 2ndparagraph, line I 'þrecooled" Page 46 - 4Ihparagraph, line 3 "solutiqn" Page 47 -2ndparugraph, line 2 "manafacturer's" Page 48 -Iine2 and "was" incubated ' Page 58 - line 5 "oaraffm" Page 59 - line 10 l'identified" Page 69 - paragraPh 3, line 1 ..has utilised for cloning and replace been cloning and allows" with'was allowed" "tiiilålioi Page75 - paragraPh 2,line 14 "zygotene-PachYtene" Fisure 3.5 - line 2 thã phage "red. transferred Fisure 3.5 - line 6 clõnes which "did" not Figure 3.9 - line 4 5 minutes "Ègg" exPosed Page 84 - line 5 "advancql" Page 88 - line 5 "both
    [Show full text]