Chromosomal nucleolar organizer region (NOR) phenotypes in nine species of the genus Ophryotrocha (Polychaeta: Dorvilleidae)

Sella, Gabriella; Vitturi, R.; Ramella, L.; Colomba, Mariastella

doi:10.1007/bf00363916

Cited by 9 publications

(3 citation statements)

References 39 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…According to Ohno (1970), animals which have developed heteromorphic chromosome sex systems appear to be more evolved than animals without them. Amemiya and Gold (1990), Thiroit-Quieveux and Insua (1992) and Sella et al (1995) maintain that the presence of a single pair of NOR-bearing chromosomes is a plesiomorphic character. Together, this provides evidence in favor of specialization of the karyotype of Paracentrotus lividus, which consists of a low chromosomal number (2n = 36) compared to other echinoids (2n = 42 to 44) (Colombera et al 1977) and includes morphologically differentiated sex chromosomes and three chromosomal pairs involved in nucleolar organization.…”

Section: Discussionmentioning

confidence: 95%

Karyotype analysis of the sea urchinParacentrotus lividus (Echinodermata): evidence for a heteromorphic chromosome sex mechanism

et al. 1996

Self Cite

View full text Add to dashboard Cite

A consistent diploid number of 2n = 36 was determined for the sea urchin Paracentrotus lividus from the Gulf of Palermo by analysis of mitotic chromosomes of both early developing embryos and male gonads. The haploid number n = 18 was determined by counts of spermatocyte bivalents at diakinesis. A heteromorphic chromosome sex mechanism of the XY type is likely present in this species. This is indicated by the occurrence of a chromosomal pair, pair No. 2, which is heteromorphic in both morphology and size in about 50% of the mitotic figures (metaphases and anaphases) of embryos. In addition, heteromorphism of the same pair of chromosomes occurred during spermatogonial metaphases in the five male specimens investigated here. The detection of a low chromosome number (2n--36) compared to other echinoids (2n = 42 to 44), a heteromorphic chromosome sex system and the involvement of three chromosome pairs in nucleolar organization (NORs) provide evidence of the specialization of the P. lividus karyotype.

show abstract

Section: Discussionmentioning

confidence: 95%

Karyotype analysis of the sea urchinParacentrotus lividus (Echinodermata): evidence for a heteromorphic chromosome sex mechanism

et al. 1996

Self Cite

View full text Add to dashboard Cite

show abstract

“…The increments in genome size, however, do not correspond to increased numbers of chromosomes (Gambi et al, 1997). The position of chromosomal nucleolar organizer regions (NOR) has been characterized and found to be highly polymorphic not only within the genus but also within most of the species (Sella et al, 1995;Vitturi et al, 2000). On the basis of inferred low GC contents and only one pair of NOR carrying chromosomes (studied by fluorescent in situ hybridization), Vitturi et al (2000) suggested that O. robusta, with 2n ϭ 10 and a small genome size (0.4 pg), is pleisiomorphic within the group.…”

Section: Discussionmentioning

confidence: 99%

Molecular Phylogeny of the Model Annelid Ophryotrocha

Dahlgren

Åkesson

Schänder

et al. 2001

The Biological Bulletin

View full text Add to dashboard Cite

Annelids of the genus Ophryotrocha are small opportunistic worms commonly found in polluted and nutrient-rich habitats such as harbors. Within this small group of about 40 described taxa a large variety of reproductive strategies are found, ranging from gonochoristic broadcast spawners to sequential hermaphroditic brooders. Many of the species have a short generation time and are easily maintained as laboratory cultures. Thus they have become a popular system for exploring a variety of biological questions including developmental genetics, ethology, and sexual selection. Despite considerable behavioral, reproductive, and karyological studies, a phylogenetic framework is lacking because most taxa are morphologically similar. In this study we use 16S mitochondrial gene sequence data to infer the phylogeny of Ophryotrocha strains commonly used in the laboratory. The resulting mtDNA topologies are generally well resolved and support a genetic split between hermaphroditic and gonochoristic species. Although the ancestral state could not be unambiguously identified, a change in reproductive strategy (i.e., hermaphroditism and gonochorism) occurred once within Ophryotrocha. Additionally, we show that sequential hermaphroditism evolved from a simultaneous hermaphroditic ancestor, and that characters previously used in phylogenetic reconstruction (i.e., jaw morphology and shape of egg mass) are homoplasic within the group.

show abstract

“…This view was not supported by Eibye-Jacobsen & Kristensen (1994), who found Iphitimidae not to be monophyletic and a subtaxon of Dorvilleidae sensu Orensanz (1990), but still favoured a close relationship of Ophryotrocha and Iphitime. Caryological (Robotti et al 1991;Sella et al 1995) and genetic (Dahlgren et al 2001) methods have been used to investigate the relationships among ophryotrochan species, as well as their relationships to other genera. These studies have indicated close relationships among species within Ophryotrocha and between Ophryotrocha and other genera placed in Dorvilleidae.…”

Section: Introductionmentioning

confidence: 99%

The phylogeny of the annelid genusOphryotrocha(Dorvilleidae)

Heggøy

Schänder

Åkesson

2007

Marine Biology Research

View full text Add to dashboard Cite

Ophyotrocha is easy to keep in the laboratory and has therefore been used in several studies of evolution and speciation. The phylogenetic relationships within the group are, however, still not clear and morphological and molecular data are contradictory. Here we attempt to shed light on the phylogeny by adding an additional gene (cytochrome c oxidase subunit I) to the previous analyses of the group. However, the results are still incongruent with the results from the morphological data. We also include a species of the genus Iphitime, and conclude that this species falls within the Ophryotrocha clade. The implications are discussed.

show abstract

Chromosomal nucleolar organizer region (NOR) phenotypes in nine species of the genus Ophryotrocha (Polychaeta: Dorvilleidae)

Cited by 9 publications

References 39 publications

Karyotype analysis of the sea urchinParacentrotus lividus (Echinodermata): evidence for a heteromorphic chromosome sex mechanism

Karyotype analysis of the sea urchinParacentrotus lividus (Echinodermata): evidence for a heteromorphic chromosome sex mechanism

Molecular Phylogeny of the Model Annelid Ophryotrocha

The phylogeny of the annelid genusOphryotrocha(Dorvilleidae)

Contact Info

Product

Resources

About