Fissions,fusions, and translocations shaped the karyotype and multiple sex chromosome constitution of the northeast‐Asian wood white butterfly,Leptidea amurensis

Previous studies have shown a dynamic karyotype evolution and the presence of complex sex chromosome systems in three cryptic Leptidea species from the Western Palearctic. To further explore the chromosomal particularities of Leptidea butterflies, we examined the karyotype of an Eastern Palearctic species, Leptidea amurensis. We found a high number of chromosomes that differed between the sexes and slightly varied in females (i.e. 2n = 118–119 in females and 2n = 122 in males). The analysis of female meiotic chromosomes revealed multiple sex chromosomes with three W and six Z chromosomes. The curious sex chromosome constitution [i.e. W_1–3/Z_1–6 (females) and Z_1–6/Z_1–6 (males)] and the observed heterozygotes for a chromosomal fusion are together responsible for the sex‐specific and intraspecific variability in chromosome numbers. However, in contrast to the Western Palearctic Leptidea species, the single chromosomal fusion and static distribution of cytogenetic markers (18S rDNA and H3 histone genes) suggest that the karyotype of L. amurensis is stable. The data obtained for four Leptidea species suggest that the multiple sex chromosome system, although different among species, is a common feature of the genus Leptidea. Furthermore, inter‐ and intraspecific variations in chromosome numbers and the complex meiotic pairing of these multiple sex chromosomes indicate the role of chromosomal fissions, fusions, and translocations in the karyotype evolution of Leptidea butterflies.     

Major structural genomic alterations can be associated with hybrid speciation in Aegilops markgrafii (Triticeae)

During evolutionary history many grasses from the tribe Triticeae have undergone interspecific hybridization, resulting in allopolyploidy; whereas homoploid hybrid speciation was found only in rye. Homoeologous chromosomes within the Triticeae preserved cross‐species macrocolinearity, except for a few species with rearranged genomes. Aegilops markgrafii, a diploid wild relative of wheat (2n = 2x = 14), has a highly asymmetrical karyotype that is indicative of chromosome rearrangements. Molecular cytogenetics and next‐generation sequencing were used to explore the genome organization. Fluorescence in situ hybridization with a set of wheat cDNAs allowed the macrostructure and cross‐genome homoeology of the Ae. markgrafii chromosomes to be established. Two chromosomes maintained colinearity, whereas the remaining were highly rearranged as a result of inversions and inter‐ and intrachromosomal translocations. We used sets of barley and wheat orthologous gene sequences to compare discrete parts of the Ae. markgrafii genome involved in the rearrangements. Analysis of sequence identity profiles and phylogenic relationships grouped chromosome blocks into two distinct clusters. Chromosome painting revealed the distribution of transposable elements and differentiated chromosome blocks into two groups consistent with the sequence analyses. These data suggest that introgressive hybridization accompanied by gross chromosome rearrangements might have had an impact on karyotype evolution and homoploid speciation in Ae. markgrafii.     

Reciprocal chromosome painting shows that the great difference in diploid number between human and African green monkey is mostly due to non-Robertsonian fissions

We used reciprocal chromosome painting with both African green monkey (C. aethiops) and human chromosome specific DNA probes to delineate homologous regions in the two species. Probes were derived by fluorescence-activated chromosome flow sorting and then were reciprocally hybridized to metaphase spreads of each species. Segments in the size range of a single chromosome band were identified, demonstrating the sensitivity of the approach when comparing species that diverged more than 20 million years ago. Outgroup analysis shows that the great difference in diploid numbers between the African green monkey (2n = 60) and humans (2n = 46) is mainly owing to fissions, and the direction of change is towards increasing diploid numbers. However, most break points apparently lie outside of the centromere regions, suggesting that the changes were not solely Robertsonian as has been previously assumed. No reciprocal translocations have occurred in the phylogenetic lines leading to humans or African green monkeys. The primate paints established here are a valuable tool to establish interspecies homology, to define rearrangements, and to determine the mechanisms of chromosomal evolution in primate species. Received: 10 December 1998 / Accepted: 18 February 1999     

Comparative cytogenetics of six Indo‐Pacific moray eels (Anguilliformes: Muraenidae) by chromosomal banding and fluorescence in situ hybridization

A comparative cytogenetic analysis, using both conventional staining techniques and fluorescence in situ hybridization, of six Indo‐Pacific moray eels from three different genera (Gymnothorax fimbriatus, Gymnothorax flavimarginatus, Gymnothorax javanicus, Gymnothorax undulatus, Echidna nebulosa and Gymnomuraena zebra), was carried out to investigate the chromosomal differentiation in the family Muraenidae. Four species displayed a diploid chromosome number 2n = 42, which is common among the Muraenidae. Two other species, G. javanicus and G. flavimarginatus, were characterized by different chromosome numbers (2n = 40 and 2n = 36). For most species, a large amount of constitutive heterochromatin was detected in the chromosomes, with species‐specific C‐banding patterns that enabled pairing of the homologous chromosomes. In all species, the major ribosomal genes were localized in the guanine‐cytosine‐rich region of one chromosome pair, but in different chromosomal locations. The (TTAGGG)_n telomeric sequences were mapped onto chromosomal ends in all muraenid species studied. The comparison of the results derived from this study with those available in the literature confirms a substantial conservation of the diploid chromosome number in the Muraenidae and supports the hypothesis that rearrangements have occurred that have diversified their karyotypes. Furthermore, the finding of two species with different diploid chromosome numbers suggests that additional chromosomal rearrangements, such as Robertsonian fusions, have occurred in the karyotype evolution of the Muraenidae.     

Phylogenomics of several deer species revealed by comparative chromosome painting with Chinese muntjac paints

A set of Chinese muntjac (Muntiacus reevesi) chromosome-specific paints has been hybridized onto the metaphases of sika deer (Cervus nippon, CNI, 2n = 66), red deer (Cervus elaphus, CEL, 2n = 62) and tufted deer (Elaphodus cephalophus, ECE, 2n = 47). Thirty-three homologous autosomal segments were detected in genomes of sika deer and red deer, while 31 autosomal homologous segments were delineated in genome of tufted deer. The Chinese muntjac chromosome X probe painted to the whole X chromosome, and the chromosome Y probe gave signals on the Y chromosome as well as distal region of the X chromosome of each species. Our results confirmed that exclusive Robertsonian translocations have contributed to the karyotypic evolution of sika deer and red deer. In addition to Robertsonian translocation, tandem fusions have played a more important role in the karyotypic evolution of tufted deer. Different types of chromosomal rearrangements have led to great differences in the genome organization between cervinae and muntiacinae species. Our analysis testified that six chromosomal fissions in the proposed 2n = 58 ancestral pecoran karyotype led to the formation of 2n = 70 ancestral cervid karyotype and the deer karyotypes is more derived compare with those of bovid species. Combining previous cytogenetic and molecular systematic studies, we analyzed the genome phylogeny for 11 cervid species.     

Trends in the karyotypic evolution of the Neotropical catfish family Heptapteridae Bockmann 1998 (Teleostei: Siluriformes)

The Heptapteridae family is endemic to the Neotropics and is one of the most representative members of the Siluriformes order in small bodies of water. Due the lack of data for clearly distinguishing their species, only recently was elevated from condition of subfamily to family. However, many doubts about certain species remain yet. There are a relatively large number of cytogenetics studies about heptapterids that permits comparative analyses focused in the karyotype evolution of the group. However, the absence of studies about this theme motivated this work. Were analyzed cytogenetically most representative species of the family: Rhamdia, Imparfinis, Pimelodella, Phenacorhamdia, and Taunaya, and compared with available data from the family. The comparative analysis indicated the predominance of biarmed chromosomes and low variation of the diploid number (around 2n = 58) suggesting that centric inversions were more important than centric fissions in the history of heptapterids. It is corroborated by a remarkable number of NOR phenotypes mainly in Imparfinis and Rhamdia species. A probable condition of Heptapteridae plesiomorphic karyotype would be one composed of 2n = 58 chromosomes of types metacentric and submetacentric mainly, with simple NOR at the sub terminal position. The reduction of diploid number, it would possibly through successive events of chromosome fusion with deletions and inversion rearrangements responsible for NOR variation within the certain genus. The occurrence of B chromosomes is from a derived event, possibly of recent origin, without phylogenetic implications.     

Chromosomal Diversity and Karyotype Evolution in South American Macaws (Psittaciformes,Psittacidae)

Most species of macaws, which represent the largest species of Neotropical Psittacidae, characterized by their long tails and exuberant colours, are endangered, mainly because of hunting, illegal trade and habitat destruction. Long tailed species seem to represent a monophyletic group within Psittacidae, supported by cytogenetic data. Hence, these species show karyotypes with predominance of biarmed macrochromosomes, in contrast to short tailed species, with a predominance of acro/telocentric macrochromosomes. Because of their similar karyotypes, it has been proposed that inversions and translocations may be the main types of rearrangements occurring during the evolution of this group. However, only one species of macaw, Ara macao, that has had its genome sequenced was analyzed by means of molecular cytogenetics. Hence, in order to verify the rearrangements, we analyzed the karyotype of two species of macaws, Ara chloropterus and Anodorhynchus hyacinthinus, using cross-species chromosome painting with two different sets of probes from chicken and white hawk. Both intra- and interchromosomal rearrangements were observed. Chicken probes revealed the occurrence of fusions, fissions and inversions in both species, while the probes from white hawk determined the correct breakpoints or chromosome segments involved in the rearrangements. Some of these rearrangements were common for both species of macaws (fission of GGA1 and fusions of GGA1p/GGA4q, GGA6/GGA7 and GGA8/GGA9), while the fissions of GGA 2 and 4p were found only in A. chloropterus. These results confirm that despite apparent chromosomal similarity, macaws have very diverse karyotypes, which differ from each other not only by inversions and translocations as postulated before, but also by fissions and fusions.     

Molecular phylogenetic analyses of nuclear and plastid DNA sequences support dysploid and polyploid chromosome number changes and reticulate evolution in the diversification of Melampodium (Millerieae, Asteraceae)

Chromosome evolution (including polyploidy, dysploidy, and structural changes) as well as hybridization and introgression are recognized as important aspects in plant speciation. A suitable group for investigating the evolutionary role of chromosome number changes and reticulation is the medium-sized genus Melampodium (Millerieae, Asteraceae), which contains several chromosome base numbers (x = 9, 10, 11, 12, 14) and a number of polyploid species, including putative allopolyploids. A molecular phylogenetic analysis employing both nuclear (ITS) and plastid (matK) DNA sequences, and including all species of the genus, suggests that chromosome base numbers are predictive of evolutionary lineages within Melampodium. Dysploidy, therefore, has clearly been important during evolution of the group. Reticulate evolution is evident with allopolyploids, which prevail over autopolyploids and several of which are confirmed here for the first time, and also (but less often) on the diploid level. Within sect. Melampodium, the complex pattern of bifurcating phylogenetic structure among diploid taxa overlain by reticulate relationships from allopolyploids has non-trivial implications for intrasectional classification.     

Molecular phylogeny and karyotype differentiation in <Emphasis Type="Italic">Paratelmatobius</Emphasis> and <Emphasis Type="Italic">Scythrophrys</Emphasis> (Anura,Leptodactylidae)

Paratelmatobius and Scythrophrys are leptodactylid frogs endemic to the Brazilian Atlantic forest and their close phylogenetic relationship was recently inferred in an analysis that included Paratelmatobius sp. and S. sawayae. To investigate the interspecific relationships among Paratelmatobius and Scythrophrys species, we analyzed a mitochondrial region (approximately 2.4 kb) that included the ribosomal genes 12S and 16S and the tRNAval in representatives of all known localities of these genera and in 54 other species. Maximum parsimony inferences were done using PAUP* and support for the clades was evaluated by bootstrapping. A cytogenetic analysis using Giemsa staining, C-banding and silver staining was also done for those populations of Paratelmatobius not included in previous cytogenetic studies of this genus in order to assess their karyotype differentiation. Our results suggested Paratelmatobius and Scythrophrys formed a clade strongly supported by bootstrapping, which corroborated their very close phylogenetic relationship. Among the Paratelmatobius species, two clades were identified and corroborated the groups P. mantiqueira and P. cardosoi previously proposed based on morphological characters. The karyotypes of Paratelmatobius sp. 2 and Paratelmatobius sp. 3 described here had diploid chromosome number 2n = 24 and showed many similarities with karyotypes of other Paratelmatobius representatives. The cytogenetic data and the phylogenetic analysis allowed the proposal/corroboration of several hypotheses for the karyotype differentiation within Paratelmatobius and Scythrophrys. Namely the telocentric pair No. 4 represented a synapomorphy of P. cardosoi and Paratelmatobius sp. 2, while chromosome pair No. 5 with interstitial C-bands could be interpreted as a synapomorphy of the P. cardosoi group. The NOR-bearing chromosome No. 10 in the karyotype of P. poecilogaster was considered homeologous to chromosome No. 10 in the karyotype of Scythrophrys sp., chromosome No. 9 in the karyotype of Paratelmatobius sp. 1, chromosome No. 8 in the karyotypes of Paratelmatobius sp. 2 and of Paratelmatobius sp. 3, and chromosome No. 7 in the karyotype of P. cardosoi. A hypothesis for the evolutionary divergence of these NOR-bearing chromosomes, which probably involved events like gain in heteochromatin, was proposed.     

Sugarcane genome architecture decrypted with chromosome‐specific oligo probes

Sugarcane (Saccharum spp.) is probably the crop with the most complex genome. Modern cultivars (2n = 100–120) are highly polyploids and aneuploids derived from interspecific hybridization between Saccharum officinarum (2n = 80) and Saccharum spontaneum (2n = 40–128). Chromosome‐specific oligonucleotide probes were used in combination with genomic in situ hybridization to analyze the genome architecture of modern cultivars and representatives of their parental species. The results validated a basic chromosome number of x = 10 for S. officinarum. In S. spontaneum, rearrangements occurred from a basic chromosome of x = 10, probably in the Northern part of India, in two steps leading to x = 9 and then x = 8. Each step involved three chromosomes that were rearranged into two. Further polyploidization led to the wide geographical extension of clones with x = 8. We showed that the S. spontaneum contribution to modern cultivars originated from cytotypes with x = 8 and varied in proportion between cultivars (13–20%). Modern cultivars had mainly 12 copies for each of the first four basic chromosomes, and a more variable number for those basic chromosomes whose structure differs between the two parental species. One?four of these copies corresponded to entire S. spontaneum chromosomes or interspecific recombinant chromosomes. In addition, a few inter‐chromosome translocations were revealed. The new information and cytogenetic tools described in this study substantially improve our understanding of the extreme level of complexity of modern sugarcane cultivar genomes.     

Does polyploidy occur in central European species of the family Sphaeriidae (Mollusca: Bivalvia)?

Some representatives of the bivalve family Sphaeriidae are assumed to be polyploid. In this study, 11 sphaeriid species (nine of the genus Pisidium, one of Musculium, and one of Sphaerium) inhabiting central Europe were studied karyologically, 10 of them for the first time. Analysis revealed high chromosome numbers (from 140 to 240). To elucidate the origin of high chromosome numbers, DNA contents were measured by flow cytometry in 5 of the studied species and, for comparison, in S. corneum and S. nucleus, which are known to be diploid (2n=30). Species with high chromosome counts yielded very similar DNA contents that are not higher than in the related species with low diploid numbers. This finding contradicts a possible origin of these species by recent polyploidization or hybridization of related species. Chromosome complements of the investigated species with high chromosome numbers differ from those with low 2n in their small chromosome size and the high proportion of subtelo- or acrocentric chromosomes. This indicates their possible origin either by an ancient polyplodization event followed by chromosomal rearrangements or by multiple chromosome fissions.     

Chromosomal distribution of interstitial telomeric sequences as signs of evolution through chromosome fusion in six species of the giant water bugs (Hemiptera,Belostoma)

Tandem arrays of TTAGG repeats show a highly conserved location at the telomeres across the phylogenetic tree of arthropods. In giant water bugs Belostoma, the chromosome number changed during speciation by fragmentation of the single ancestral X chromosome, resulting in a multiple sex chromosome system. Several autosome–autosome fusions and a fusion between the sex chromosome pair and an autosome pair resulted in the reduced number in several species. We mapped the distribution of telomeric sequences and interstitial telomeric sequences (ITSs) in Belostoma candidulum (2n = 12 + XY/XX; male/female), B. dentatum (2n = 26 + X₁X₂Y/X₁X₁X₂X₂), B. elegans (2n = 26 + X₁X₂Y/X₁X₁X₂X₂), B. elongatum (2n = 26 + X₁X₂Y/X₁X₁X₂X₂), B. micantulum (2n = 14 + XY/XX), and B. oxyurum (2n = 6 + XY/XX) by FISH with the (TTAGG)_n probes. Hybridization signals confirmed the presence of TTAGG repeats in the telomeres of all species examined. The three species with reduced chromosome numbers showed additional hybridization signals in interstitial positions, indicating the occurrence of ITS. From the comparison of all species here analyzed, we observed inverse relationships between chromosome number and chromosome size, and between presence/absence of ITS and chromosome number. The ITS distribution between these closely related species supports the hypothesis that several telomere–telomere fusions of the chromosomes from an ancestral diploid chromosome number 2n = 26 + XY/XX played a major role in the karyotype evolution of Belostoma. Consequently, our study provide valuable features that can be used to understand the karyotype evolution, may contribute to a better understanding of taxonomic relationships, and also elucidate the high plasticity of nuclear genomes at the chromosomal level during the speciation processes.     

Comparative molecular cytogenetic analysis of three <Emphasis Type="Italic">Leuciscus</Emphasis> species (Pisces,Cyprinidae) using chromosome banding and FISH with rDNA

A comparative molecular cytogenetic analysis was performed on three species of the genus Leuciscus viz. ide L. idus, chub L. cephalus and dace L. leuciscus distributed in Poland, using C-, Ag- and chromomycin A₃ (CMA₃)-stainings and fluorescence in situ hybridization (FISH) with 5.8S + 28S rDNA as a probe. Although the three species examined shared 2n = 50 chromosomes and the largest acrocentric chromosome pair in the complement, they were characterized with karyotypic differences in terms of the number of uni- and biarmed chromosomes and the localization of nucleolar organizer regions (NORs) revealed by Ag-staining and FISH. L. idus and L. cephalus showed the rDNA sites on the long arms of one submetacentric (SM) chromosome pair and on the short arms of one subtelocentric (ST) chromosome pair, respectively. These NORs were CMA₃-positive, GC-rich and C-positive heterochromatic sites in both species. Such chromosome banding features were also true for four NORs localizing on one of each SM and ST pair in L. leuciscus, but considerable numerical NOR polymorphism became apparent with Ag-staining and FISH due to a different combination of these NOR-bearing SMs and STs in this dace. The present results indicate that the molecular cytogenetic analysis applied herein may become useful to elucidate the karyotype evolution and phylogenetic relationships among the species in the genus Leuciscus and other related groups.     

Directional mitochondrial introgression and character displacement due to reproductive interference in two closely related Pterostichus ground beetle species

Reproductive interference due to interspecific hybridization can lead to character displacement among related species with overlapping ranges. However, no studies have examined which reproductive traits are most important in reducing reproductive interference. We conducted molecular analyses of two nuclear genes (28S and Wingless) and a mitochondrial gene (COI) from two closely related ground beetle species, Pterostichus thunbergi and Pterostichus habui (Coleoptera: Carabidae), with overlapping distributions. In addition, we examined four reproductive traits (body size, organ morphologies of intromittent and non‐intromittent male genital organs, and female reproductive period) in sympatric and allopatric habitats. We compared male genital morphology using geometric morphometric analysis. The species determined by morphology were classified into separate groups based on the phylogenetic tree constructed by the nuclear gene (Wingless). However, according to the mitochondrial genes examined, P. thunbergi was not monophyletic, whereas at the sympatric sites, these species formed a monophyletic clade. This incongruence suggests that interspecific hybridization and subsequent mitochondrial introgression from P. habui to P. thunbergi have occurred. Concerning genital morphology, both of the intromittent and nonintromittent organs of P. thunbergi differed more from P. habui at the sympatric sites than between allopatric sites, suggesting reproductive character displacement. Pterostichus thunbergi, which likely arrived in P. habui habitat in small numbers, would have experienced stronger selection pressures than P. habui.     

A phylogenetic analysis of Pseudopaludicola (Anura) providing evidence of progressive chromosome reduction

Here, we present a molecular phylogenetic analysis of the Neotropical genus Pseudopaludicola focusing on species relationships including 11 of the 17 known species of Pseudopaludicola; several samples of Pseudopaludicola are not assigned to any species; and 34 terminal species as an outgroup. The study was based on the analysis of approximately 2.3 kb of the sequence of the mitochondrial 12S rRNA, tRNA^val and 16S rRNA genes through maximum parsimony and Bayesian phylogenetic reconstruction approaches. Our results showed that Pseudopaludicola is a well‐supported monophyletic group organized into four major clades and confirmed that the assemblage of species that lack T‐shaped terminal phalanges is paraphyletic with respect to the P. pusilla Group. Chromosomal data mapped on the cladogram showed a direct correlation among the four clades and observed chromosome numbers (2n = 22, 20, 18 and 16) with a progressive reduction in the chromosome number. Overall, our findings suggest that some taxonomic changes are necessary and reinforce the need for a revision of the genus Pseudopaludicola.     

Structure and evolution of <Emphasis Type="Italic">Apetala3</Emphasis>, a sex-linked gene in <Emphasis Type="Italic">Silene latifolia</Emphasis>

Background  

The evolution of sex chromosomes is often accompanied by gene or chromosome rearrangements. Recently, the gene AP3 was characterized in the dioecious plant species Silene latifolia. It was suggested that this gene had been transferred from an autosome to the Y chromosome.     

Phylogeography and diversification of an Amazonian understorey hummingbird: paraphyly and evidence for widespread cryptic speciation in the Plio‐Pleistocene

Straight‐billed Hermit Phaethornis bourcieri inhabits the understorey of upland terra firme forest throughout most of the Amazon basin. Currently, two allopatric taxa regarded as subspecies are recognized: P. b. bourcieri and P. b. major. However, the validity, interspecific limits and evolutionary history of these taxa are not yet fully elucidated. We use molecular characters to propose a phylogenetic hypothesis for populations and taxa grouped under Phaethornis bourcieri. Our results showed that P. bourcieri is part of the ‘Ametrornis’ clade, along with Phaethornis philippii and Phaethornis koepckeae, and that the subspecies major is more closely related to the latter two species than to populations grouped under nominate bourcieri. Our phylogenetic hypotheses recovered three main reciprocally monophyletic clades under nominate bourcieri separated by the lower Negro River and the Branco River or the Branco–Negro interfluve (clades B and C) and the upper Amazon (Solimões) or lower Marañon/Ucayali Rivers (clades C and D). Based on multi‐locus phylogeographic and population genetics approaches, we show that P. b. major is best treated as a separate species, and that P. b. bourcieri probably includes more than one evolutionary species, whose limits remain uncertain. The diversification of the ‘Ametrornis’ clade (P. bourcieri, P. philippii and P. koepckeae) is centred in the Amazon and appears to be closely linked to the formation of the modern Amazon drainage during the Plio‐Pleistocene.     

Diverse evolutionary pathways shaped 5S rDNA of species of tribe Anemoneae (Ranunculaceae) and reveal phylogenetic signal

Anemone sensu lato (including Pulsatilla and Hepatica), tribe Anemoneae (Ranunculaceae), is arranged into two subgenera, Anemone and Anemonidium, with basic chromosome numbers x = 8 and x = 7, respectively. We elucidated the level of divergence of 5S rDNA unit arrays between the subgenera, determined intra‐individual and interspecific sequence variation and tested 5S rDNA phylogenetic signal in revealing the origin of polyploid species. High intra‐individual nucleotide diversity and the presence of 5S rDNA unit array length variants and pseudogenes indicate that weak homogenization forces have shaped 5S rDNA in the investigated species. Our results show that 5S rDNA evolved through two major changes: diversification of 5S rDNA into two lineages, one with long (subgenus Anemone) and one with short 5S rDNA unit arrays (subgenus Anemonidium); and subsequent contraction and expansion of 5S rDNA unit arrays. Phylogenetic analysis based on 5S rDNA supports the hypothesis that A. parviflora could be a parental species and donor of the subgenome D to the allopolyploids A. multifida (BBDD) and A. baldensis (AABBDD). In A. baldensis interlocus exchange possibly occurred, followed by subsequent replacement of the 5S rDNA from subgenome D with those from subgenome B. Here we present evidence that both models, concerted and birth‐and‐death evolution, were probably involved in the evolution of the 5S rDNA multigene family in subgenera Anemone and Anemonidium.     

Molecular Phylogenetic Positions of Two New Marine Gregarines (Apicomplexa)—Paralecudina anankea n. sp. and Lecudina caspera n. sp.—from the Intestine of Lumbrineris inflata (Polychaeta) Show Patterns of Co‐evolution

Gregarine apicomplexans are unicellular parasites commonly found in the intestines and coeloms of invertebrate hosts. Traits associated with the conspicuous feeding stage of gregarines, known as the trophozoite, have been used in combination with molecular phylogenetic data for species delimitation and the reconstruction of evolutionary history. Trophozoite morphology alone is often inadequate for inferring phylogenetic relationships and delimiting species due to frequent cases of high intraspecific variation combined with relatively low interspecific variation. The current study combined morphological data with small subunit (SSU) rDNA sequences to describe and establish two novel marine gregarine species isolated from the intestine of a polychaete host Lumbrineris inflata collected in British Columbia (Canada): Paralecudina anankea n. sp. and Lecudina caspera n. sp. The sister species to the host is Lumbrineris japonica, which can be found on the opposite side of the Pacific Ocean (Japan) and contains two different species of gregarine parasites: Paralecudina polymorpha and Lecudina longissima. Molecular phylogenetic analyses placed P. anankea n. sp. as the sister species to P. polymorpha and L. caspera n. sp. as the sister species to L. longissima. This phylogenetic pattern demonstrates a co‐evolutionary history whereby speciation of the host (Lumbrineris) corresponds with simultaneous speciation of the two different lineages of intestinal gregarines (Paralecudina and Lecudina).     

Characterization of a new cytotype and ocurrence of a B microchromosome in two spot astyanax,Astyanax bimaculatus Linnaeus, 1758 (Characiformes: Characidae)

Although Astyanax bimaculatus is the most representative species of the genus in the Amazon region, there are no cytogenetic studies of A. bimaculatus species in Amazon region. Thus, we aimed to analyse the chromosome complements of specimens from this area using classic and molecular cytogenetic approaches. The results revealed the existence of a distinct cytotype and this is the first report of the occurrence of a B microchromosome in the species. Overall, these data indicate that the karyotypic evolution of this species is complex, involving the occurrence of chromosomal rearrangements.