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Deviation from apomictic reproduction in Dendrobaena octaedra?

2008; BioMed Central; Volume: 145; Issue: 4 Linguagem: Inglês

10.1111/j.0018-0661.2008.02045.x

1601-5223

Vibeke Simonsen, Martin Holmstrup,

Study of Mite Species

HereditasVolume 145, Issue 4 p. 212-214 Open Access Deviation from apomictic reproduction in Dendrobaena octaedra? Vibeke Simonsen , Vibeke Simonsen Department of Terrestrial Ecology, ational Environmental Research Institute, University of Aarhus, Silkeborg, DenmarkSearch for more papers by this authorMartin Holmstrup, Martin Holmstrup Department of Terrestrial Ecology, ational Environmental Research Institute, University of Aarhus, Silkeborg, DenmarkSearch for more papers by this author Vibeke Simonsen , Vibeke Simonsen Department of Terrestrial Ecology, ational Environmental Research Institute, University of Aarhus, Silkeborg, DenmarkSearch for more papers by this authorMartin Holmstrup, Martin Holmstrup Department of Terrestrial Ecology, ational Environmental Research Institute, University of Aarhus, Silkeborg, DenmarkSearch for more papers by this author First published: 15 September 2008 https://doi.org/10.1111/j.0018-0661.2008.02045.xCitations: 1 Vibeke Simonsen, Vejlsoevej 25, P.O. Box 314, DK- 8600 Silkeborg, Denmark. E-mail: vs@dmu.dk AboutFiguresReferencesRelatedInformationPDFSections Material and methods Results and Discussion AcknowledgementsReferencesCiting LiteraturePDF ToolsExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessClose modalShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL The earthworm Dendrobaena octaedra has an original distribution covering the central and northern Palearctic but has spread over large areas of North America and has caused considerable concern there as the introduction may lead to collapse of local species (Callaham et al. 2006; Tiunov et al. 2006). It is reported to reproduce through apomictic parthenogenesis (Omodeo 1955). This is in contrast to all other parthenogenetic earthworms that have automictic (meiotic) parthenogenesis (Suomalainen et al. 1987). The number of chromosomes and the morphology of the internal and external male organs may vary (Omodeo 1955; Casellato and Rodighiero 1972; Vedovini 1973) but D. octaedra in northern Europe are hexaploids with 6n=108. This number was confirmed by a subsequent study (Hongell and Terhivuo 1989). When doing isozyme analysis (Terhivuo and Saura 1990) it was observed that the clonal diversity was high, among 428 individuals 147 clones based on six enzymes were observed and of these 80 clones were unique, i.e. only found in a single individual. This high level of clonal diversity was also found in a study done in the northern hemisphere (Hansen et al. 2006) where 176 clones based on seven enzymes, at least representing nine loci revealed 125 unique clones among 345 worms analysed. Compared to other parthenogenetic earthworm species in northern Europe, D. octaedra always has a very high level of clonal diversity (Terhivuo and Saura 2006). The high diversity may be due to efficient dispersal of clones, effects of polyploidy, modification of gene products (proteins), meiotic thelytoky accompanied with segregation, self fertilisation or occasional sexual reproduction (cf. Bengtsson 2003). However, self fertilisation or sexual reproduction can most likely be excluded since only incomplete spermatogenesis is found (Omodeo 1955, 1957). Furthermore, absence of male pores in many specimens does not support biparental reproduction or self fertilisation (Terhivuo 1988; Terhivuo and Saura 2006). In an ovum from the ovisac 108 chromosomes were found to be univalents (Hongell and Terhivuo 1989) which indicated that oogenesis was asynaptic, i.e. the eggs were developing through mitosis instead of meiosis, which is an argument against meiotic thelytoky. This observation fits to earlier findings (Omodeo 1955). Only high rates of dispersal, effects of polyploidy in combination with null alleles and/or segregation distortion or modifications of gene products may explain the high level of diversity. In the present study a comparison of phenotypes from reproducing individuals and their offspring by means of allozymes was carried out to see if the apomictic parthenogenetic reproduction mode could be confirmed. Material and methods Individuals were collected from laboratory cultures of Dendrobaena octaedra from four locations: Disko (Greenland), Jyväskyla (Finland), Silkeborg DMU and Silkeborg Nordskov (Denmark). Cocoons from each culture were incubated at 20°C on moist filter paper. Fifteen newly hatched juveniles from each location were then cultured in isolation (Bindesbøl et al. 2007) until each worm had reached sexual maturity and at least 15 cocoons had been produced. At this stage the adult worm was frozen at −80°C and stored until analysis. The cocoons were incubated on moist filter paper until hatching and juveniles were frozen and stored at −80°C until analysis. The allozyme procedures and enzymes (a total of seven) were the same as described by Hansen et al. (2006). In addition, three more enzymes were included in this study, i.e. acid phosphatase (ACP, E.C. 3.1.3.2) and mannose-6-phosphate isomerase (MPI, E.C. 5.3.1.8) using the histidine-citrate buffer pH=5.7 and superoxide dismutase (SOD, E.C. 1.15.1.1) using the lithium hydroxide-borate buffer pH=8.1. When doing the analyses the adult and the offspring were applied side by side on the gel. Only one zone of aspartate aminotransferase was revealed for the juveniles and scored, although in a previous study two zones were scored for adult worms (Hansen et al. 2006). Regarding cytosol aminotransferase only the most heavily stained zone was scored in this study and not the polymorphic zone, which was scored in an earlier study (Hansen et al. 2006). Results and Discussion Eleven worms from each of the locations produced cocoons. From eight to 15 offspring were collected from each of the adults, in total 634 juveniles were analysed. Most offspring were identical to the parental worm. A similar study on the automic parthenogenetic reproducing worm Eiseniella tetraedra showed congruence between the offspring and the parent (Terhivuo et al. 2002) as expected. However, some offspring in the present study revealed a phenotype not identical to the adult (Table 1, Fig. 1). This was indeed unexpected: in apomictic parthenogenesis the eggs are formed through mitosis and all offspring will be identical. However, a high degree of polyploidy (hexaploidy) can mask the presence of null alleles and other alleles, i.e. five chromosomes carrying the gene or genes for phenotype 1 and one chromosome carrying the gene or genes for phenotype 2. A combination of null alleles and non-disjunction may explain the presence of the deviating phenotype shown in Fig. 1. In order to judge if (mitotic) non-disjunction played a role for this observation, the karyotypes should have been determined. That, in turn, would have needed identifying individual sets of six chromosomes, something that was beyond the scope of this work. Furthermore, worms with chromosomal numbers deviating from 108 were mainly found in Greenland, northern Iceland and Dolomite Alps (Omodeo 1955, 1957). However, the number of parental worms having offspring with deviating phenotypes was 4–7 for all locations with the sample from Greenland having five worms with deviating phenotypes (Table 1). Table 1. Parents with deviating phenotypes among offspring analysed for three enzymes (ID no.=identity no., AAT=aspartate aminotransferase, EST=esterase and SOD=superoxide dismutase). All the parents revealed single banded phenotypes for the three enzymes listed. Location Parent ID no. Enzyme AAT EST SOD No. of offspring Deviating phenotype (triple banded) Deviating phenotype 1 (single banded) Deviating phenotype 2 (double banded) Deviating phenotype (triple banded) Disko, Greenland 1 15 1 3 15* 9 4 15 2 8 15** 1 1 15 15 1 Jyväskyla, Finland 3 15 1 5 15 1 6 15 2 7 15 1 12 15** 1 1 Silkeborg, DMU, Denmark 2 15 1 3 15* 11 4 4 15 1 10 14 1 Silkeborg, Nordskov Denmark 4 15 1 5 15 2 9 15 1 10 12 1 12 15* 5 14 14** 2 2 15 11 1 *Fit to 1:1 segregation according to the test value for a χ2 test after Yates’ correction.**Not tested for fit to 1:1 segregation. Figure 1Open in figure viewerPowerPoint Esterase, parent no. 15 from Disko, Greenland. The parent is the sample to the left followed by four offspring, a blank and 11 offspring. Offspring no. 6 has the deviating phenotype 1. Three litters were in agreement with a 1:1 segregation (Table 1), which could be due to self-fertilisation. Unfortunately, the parental worms were not checked for male pores. However, the remaining 18 litters did not fit to 1:1 segregation, which ruled out self-fertilisation as the only explanation for the variation found in Dendrobaena octaedra. Gene conversion would require meiosis, and, as stated in the introduction, the oogenesis was reported to be mitotic and not meiotic. On the other hand, the results suggest the presence of an alternate phenotype, which is compatible with the expectations of gene conversion. Furthermore, the results were not consistent with any realistic mutation rate, which for allozymes is 10-6 as mentioned by many authors (Allendorf and Luikart 2006). In addition, it had to be the same mutation as the deviating type 1 had the same zymogram for all the observations where this phenotype was found. Finally, the deviating phenotypes not fitting to self-fertilisation were only found for the enzyme esterase. This enzyme might be more sensitive to the environment than other enzymes, e.g. enzymes in the glycolytic pathway, which are needed for normal metabolism. A study on esterase from Lumbricus rubellus revealed that metals might have an effect on the phenotype of esterase (Simonsen and Scott-Fordsmand 2004). If the environment was responsible for the deviating phenotypes it would be expected to observe the same phenomenon for all the worms studied in this work as they were kept under the same conditions. Jordaens et al. (1999) have observed that feeding may have an impact on esterases in slugs (Cariarion species). This phenomenon can be ruled out in the present study due to the experimental design. In conclusion, our study shows that other reproductive mechanisms than apomictic parthenogenesis and to some extent self fertilisation may occur in D. octaedra. A more detailed study of the reproduction mode is needed to understand why natural populations of this parthenogenetic earthworm often display a high level of genetic variation. Acknowledgements We would like to thank Anni Christiansen for competent technical assistance with the isozyme analysis and Elin Jørgensen and Zdenek Gavor for cultivating the worms. The study was partially supported by the EU Integrated Project ALARM (EU 6th Framework Programme No. GOCE-CT-2003-506675). A. Saura and J. Terhivuo are highly acknowledged for valuable comments to an earlier version of this manuscript. References Allendorf F. W. and Luikart G., (2006). Conservation and the genetics of populations, Blackwell. Bengtsson B.-O., (2003). Genetic variation in organisms with sexual and asexual reproduction. J. Evol. Biol. 16: 189– 199. Bindesbøl A. M., Bayley M., Damgaard C. F. et al., (2007). Life-history traits and population growth rate in the laboratory of the earthworm Dendrobaena octaedra cultured in copper-contaminated soil. Appl. Soil Ecol. 35: 46– 56. Callaham M. A.Jr., González G., Hale C. M. et al., (2006). Policy and management responses to earthworm invasions in North America. Biol. Invas. 8: 1317– 1329. Casellato S. and Rodighiero R., (1972). Karyology of Lumbricidae. III. Contribution. Caryologia 25: 513– 524. Hansen P. L., Holmstrup M., Bayley M. et al., (2006). Low genetic variation for Dendrobaena octaedra from Greenland compared to populations from Europe and North America: refuge or selection?. Pedobiologia 50: 225– 234. Hongell K. and Terhivuo J., (1989). Chromosomal status of the parthenogenetic earthworm Dendrobaena octaedra (Sav.) (Oligochaeta: lumbricidae) in southern Finland. Hereditas 110: 179– 182. Jordaens K., Van Riel P., Verhagen R. et al., (1999). Food-induced esterase electromorphs in Carinarion spp. and their effects on taxonomic data analysis (Gastropoda, Pulmonata, Arionidae). Electrophoresis 20: 473– 479. Omodeo P., (1955). Cariologia dei Lumbricidae. II. Contributo. Caryologia 8: 135– 178. Omodeo P., (1957). Lumbricidae and Lumbriculidae of Greenland. Medd. Groenland 124: 1– 27. Simonsen V. and Scott-Fordsmand J. J., (2004). Genetic variation in the enzyme esterase, bioaccumulation and life history traits in the earthworm Lumbricus rubellus from a metal contaminated area, Avonmouth, England. Ecotoxicology 13: 773– 786. Suomalainen E., Saura A. and Lokki J., (1987). Cytology and evolution in parthenogenesis, CRC Press. Terhivuo J., (1988). Morphological and morphometric variation of the parthenogenetic earthworm Dendrobaena octaedra (Sav.) (Oligochaeta, Lumbricidae) in eastern Fennoscandia. Ann. Zool. Fenn. 25: 303– 320. Terhivuo J. and Saura A., (1990). Allozyme variation in parthenogenetic Dendrobaena octaedra (Oligochaeta: Lumbricidae) populations of eastern Fennoscandia. Pedobiologia 34: 113– 139. Terhivuo J. and Saura A., (2006). Dispersal and clonal diversity of North-European parthenogenetic earthworms. Biol. Invas. 8: 1205– 1218. Terhivuo J., Lundqvist E. and Saura A., (2002). Clone diversity of Eiseniella tetraedra (Oligochaeta: Lumbricidae) along regulated and free-flowing boreal rivers. Ecography 25: 714– 720. Tiunov A. V., Hale C. M., Holdsworth A. R. et al., (2006). Invasion patterns of Lumbricidae into the previously earthworm-free areas of northeastern Europe and the western Great Lakes region of North America. Biol. Invas. 8: 1223– 1234. Vedovini A., (1973). Systematique, caryologie et ecologie des oligochetes terrestres de la region Provençale PhD thesis. Fac. of Science, Univ. of Provence, Marseille. Citing Literature Volume145, Issue4August 2008Pages 212-214 FiguresReferencesRelatedInformation RecommendedCytology of Some Apomictic Paspalum SpeciesByron L. Burson, Crop ScienceQuantitative variation for apomictic reproduction in the genus Boechera (Brassicaceae)Olawale M. Aliyu, M. Eric Schranz, Timothy F. Sharbel, American Journal of BotanyLimonium homoploid and heteroploid intra- and interspecific crosses unveil seed anomalies and neopolyploidy related to sexual and/or apomictic reproductionSofia I.R. Conceição, Ana Sofia Rõis, Ana D. Caperta, TAXONReproduction mode in the allopolyploid facultatively apomictic hawkweed Hieracium rubrum (Asteraceae, H. subgen. Pilosella)ANNA KRAHULCOVÁ, STANISLAVA PAPOUŠKOVÁ, FRANTIŠEK KRAHULEC, HereditasEvidence for Autoploidy in Apomictic Paspalum RufumCamilo L. Quarín, Guillermo A. Norrmann, Francisco Espinoza, Hereditas