Pairs Of Submetacentric Chromosomes Research Articles

Karyotypes and Physical Mapping of Ribosomal DNA with Oligo-Probes in Eranthis sect. Eranthis (Ranunculaceae).

A comparative karyotype analysis of four species of yellow-flowered Eranthis sect. Eranthis, i.e., E. bulgarica, E. cilicica, E. hyemalis, and E. longistipitata from different areas, has been carried out for the first time. All the studied specimens had somatic chromosome number 2n = 16 with basic chromosome number x = 8. Karyotypes of the investigated plants included five pairs of metacentric chromosomes and three pairs of submetacentric/subtelocentric chromosomes. The chromosome sets of the investigated species differ mainly in the ratio of submetacentric/subtelocentric chromosomes, their relative lengths, and arm ratios. A new oligonucleotide probe was developed and tested to detect 45S rDNA clusters. Using this probe and an oligonucleotide probe to 5S rDNA, 45S and 5S rDNA clusters were localized for the first time on chromosomes of E. cilicica, E. hyemalis, and E. longistipitata. Major 45S rDNA clusters were identified on satellite chromosomes in all the species; in E. cilicica, minor clusters were also identified in the terminal regions of one metacentric chromosome pair. The number and distribution of 5S rDNA clusters is more specific. In E. cilicica, two major clusters were identified in the pericentromeric region of a pair of metacentric chromosomes. Two major clusters in the pericentromeric region of a pair of submetacentric chromosomes and two major clusters in the interstitial region of a pair of metacentric chromosomes were observed in E. longistipitata. E. hyemalis has many clusters of different sizes, localized mainly in the pericentromeric regions. Summarizing new data on the karyotype structure of E. sect. Eranthis and previously obtained data on E. sect. Shibateranthis allowed conclusions to be formed about the clear interspecific karyological differences of the genus Eranthis.

Morphological Differentiation and Karyotypic Studies of the African Common Toad Sclerophrys (Bufo) Regularis (Reuss, 1833)

The study analyzed the morphological differentiation and karyotype among populations of the common toad, Sclerophrys (Bufo) regularis from six Local Government Areas in Ondo state. Variations in fifteen morphometric and qualitative characters in one hundred and seventy-one animals from six population samples were analyzed using univariate and multivariate statistics. Descriptives of sexes and correlation between morphological characters was also analyzed. Female toads had larger mean values of most of the morphological characters studied with weight contributing the largest variance. The chromosomes of twenty-four specimens of the toad were also studied using standard bone marrow smear techniques. A chromosome complement of 2n=20 was observed for this species. The chromosomes consists of nine pairs of metacentric and one pair of submetacentric chromosomes. The chromosomes based on centromeric position could be grouped into two - metacentric and submetacentric - and based on size, into three metacentric chromosomes; 1-4 which were large, metacentric chromosomes; 5-6 medium sized metacentric chromosomes, while 7-9 were small sized, and the last pair (10), submetacentric chromosomes were small. The fundamental number of this species is 40 and with no sex chromosomes or satellites reported, while bi-armed chromosomes were observed. Findings also showed that female individuals of the species weighed more than the male.

Contributions of species Rineloricaria pentamaculata (Loricariidae:Loricariinae) in a karyoevolutionary context

Species of Rineloricaria demonstrate an interesting evolutionary history from a cytogenetic point of view, due to the occurrence of extensive variation in diploid number (2n=36 -70 chromosomes), with Robertsonian rearrangements mostly responsible for this karyotypic diversity. In this study we present the karyotypic data for a population of Rineloricaria pentamaculata, collected in the Itiz stream, a tributary of the Paraná River Basin (Paraná, Brazil), which exhibited 2n=56 chromosomes distributed in 8m/sm+48st/a (number fundamental equal to 64) and simple NOR system revealed by fluorescent in situ hybridization (FISH) with 18S rDNA probe, silver nitrate and positive C band, located on the first submetacentric chromosome pair (pair 5). In addition, the NOR pair showed a size heteromorphism for this region, rich in GC composition (positive CMA3). Clusters of 5S rDNA were located in 14 chromosomes and the FISH with a telomeric probe was used to map possible evidence of chromosomal fusions, however, it showed only telomeric sites. These results corroborate the data for the species R. pentamaculata and the genus Rineloricaria, showing that they are similar to most of the populations analyzed. About the cytogenetic data of R. pentamaculata, we reaffirm that most populations were conserved, but in those with derived characteristics, Robertsonian chromosomal rearrangements probably contributed to the karyotypic evolution of the group.

Chromosome Complement of Pomatoschistus marmoratus and Karyotype Evolution in Sand Gobies (Gobiidae: Gobionellinae)

The family Gobiidae constitutes one of the most diverse groups among teleost fish; some of its species are objects of aquaculture and fisheries. Despite many years of cytogenetic studies, the chromosome complements of many species of gobies remain unknown, and the trends of karyotypic evolution are poorly understood. Here I describe a previously unstudied karyotype of a widespread species from the group of sand gobies (Pomatoschistus marmoratus) and analyze the trends of karyotypic evolution of this group in comparison with other taxonomic groups of gobies from the Atlantic-Mediterranean and Ponto-Caspian regions. For P. marmoratus, the diploid number is 2n=46; it consists of 11 pairs of submetacentric chromosomes, 12 pairs of subtelocentric and telocentric chromosomes (NF=68). A comparative karyological analysis showed that the main trend in the karyotypic evolution of sand gobies differs from that of other groups of gobies and is associated with an increase in the number of chromosomal arms as a result of chromosomal rearrangements leading to a change in the centromere position. The results obtained contribute to understanding the role of chromosomal rearrangements in the evolution of Gobiidae and are of interest for further cytogenetic studies of this large family of fish.

Apomixis for no bacteria-induced thelytoky in Diglyphus wani (Hymenoptera: Eulophidae).

In Hymenoptera species, the reproductive mode is usually arrhenotoky, where haploid males arise from unfertilized eggs and diploid females from fertilized eggs. In addition, a few species reproduce by thelytoky, where diploid females arise from unfertilized eggs. Diploid females can be derived through various cytological mechanisms in thelytokous Hymenoptera species. Hitherto, these mechanisms were revealed mainly in endosymbiont-induced thelytokous Hymenoptera species. In contrast, thelytokous Hymenoptera species in which a reproductive manipulator has not been verified or several common endosymbionts have been excluded were paid less attention in their cytological mechanisms, for instance, Diglyphus wani (Hymenoptera: Eulophidae). Here, we investigated the cytological mechanism of D. wani using cytological methods and genetic markers. Our observations indicated that the diploid karyotypes of two strains of D. wani consist of four pairs of relatively large metacentric chromosomes and one pair of short submetacentric chromosomes (2n = 10). The arrhenotokous strains could complete normal meiosis, whereas the thelytokous strain lacked meiosis and did not expulse any polar bodies. This reproductive type of lacking meiosis is classified as apomictic thelytoky. Moreover, a total of 636 microsatellite sequences were obtained from thelytokous D. wani, dominated by dinucleotide repeats. Genetic markers results showed all three generations of offspring from thelytokous strain maintained the same genotype as their parents. Our results revealed that D. wani is the first eulophid parasitoid wasp in Hymenoptera whose thelytoky was not induced by bacteria to form an apomictic thelytoky. These findings provide a baseline for future inner molecular genetic studies of ameiotic thelytoky.

KARYOTYPE ANALYSIS OF PACHIRA (PACHIRA AQUATICA)

Pachira aquatica belongs to the Bombacaceae group, the clades in the family Malvaceae. The subfamily contains about 304 species, most with high economic and medicinal values. Considering their importance, some of the plants attained special cultural status. Pachira comes from Central America and South America, introduced and spread to Europe, Africa, and Asia. The diversity of plant morphology can result from environmental factors interacting with genetic features, then expressed as phenotypes. Geographic isolation can prevent gene flow between populations. Geographic separation allows mutations to occur, and natural selection and genetic drift can alter allele frequencies differently in separate populations leading to allopatric speciation. The present study aims to determine the characteristics and chromosomal composition of P. aquatica. This study used the squashing method, often employed to obtain chromosomes by squeezing the preparations. The results showed that the number of chromosomes of pachira was 2n = 66. The chromosome length of pachira ranged from 0.812±0.009 to 1.955±0.009 μm. The chromosome shape of pachira is metacentric. The karyotype arrangement of pachira is 2n = 2× = 29m + 4sm, where 2n equals to 29 pairs of metacentric chromosomes and four pairs of submetacentric chromosomes. The intrachromosomal asymmetry index (A1) of the chromosome of pachira scored at 0.19±0.001, with the value of the interchromosomal asymmetry index (A2) at 0.224±0.021.

Karyotypes and ZZ/ZW Sex Chromosome System of Endemic Squalius recurvirostris (Leuciscinae, Cyprinidae) in Turkey

In this study, detailed cytogenetic properties of the endemic Akşehir chub, Squalius recurvirostris, distributed in the basin of the Ilgın (Çavuşçu) Lake basin was investigated by applying the standard Giemsa staining, C-banding and Ag-NOR technique. Diploid chromosome number is (2n) 50. A pair of heteromorphic chromosomes was detected in the karyotype in females. However, this difference was not observed in males. Therefore, it was determined that the heteromorphic chromosome pair in females were ZZ/ZW sex chromosomes. The Z chromosome in females is large acrocentric, and the W chromosome is medium-sized submeta/subtelocentric. The number of all chromosomal arms (NF) is 90, and the fundamental number of autosomal arms (NFa) is 88 in the karyotyped of the individuals studied. Some bi-armed and acrocentric chromosomes have centromeric C-bands in the chromosome set. The slightly centromeric or pericentromeric C-bands are observed in some chromosomes, while other chromosome pairs are C-negative. In the individuals studied two active NORs were detected. Both of these NORs were hemizygous and associated with a large C-heterochromatin region. One of the NORs was detected on the entire long arm of the submetacentric chromosome pair and the other on the entire short arm of another submetacentric chromosome pair.

First karyotype description of the species of Adenomera Steindachner, 1867 (Anura, Leptodactylidae) in the " thomei" clade.

The genus Adenomera Steindachner, 1867 currently comprises 29 nominal species, some of which are suggested to be cryptic species complexes. The present study was carried out with specimens of the "thomei" clade that encompasses three taxa distributed in the Atlantic Forest biome: Adenomerathomei Almeida et Angulo, 2006, Adenomera sp. L., and Adenomera sp. M. We used classical cytogenetics to describe the diploid number and karyomorphology of these three species collected in two different locations in the state of Bahia, Brazil. Our results revealed the diploid number 2n = 24 (FN = 34) with two pairs of metacentric chromosomes (pairs 1 and 5), three pairs of submetacentric chromosomes (pairs 2, 3, and 4), and seven pairs of telocentric chromosomes (pairs 6, 7, 8, 9, 10, 11, and 12). Further morphological, bioacoustic, and cytogenetic data (C-banding and AgNor) are needed to better delineate the lineages within the "thomei" clade.

Cytogenetic Analysis of Alburnus escherichii (Teleostei: Leuciscidae) in Turkey

In this study, cytogenetic properties of A. escherichii were investigated using standard Giemsa staining, C-banding, and Ag-NOR staining techniques. The karyotype of Sakarya bleak, the diploid chromosome number was 2n = 50, consists of six pairs of metacentric, 12 pairs of submetacentric, and seven pairs of acrocentric autosomes (NF=86). No morphologically distinguishable heteromorphic sex chromosomes were detected in the karyotype. While most autosomes had centromeric and pericentromeric C-heterochromatin (some chromosomes slightly) blocks, the other autosomal pairs were C-negative. Also, the short arm of the eleventh submetacentric chromosome pair was entirely C-positive. The nucleolar organizer regions were localized in medium-sized submetacentric autosomal pairs. Active NORs associated with the C-heterochromatin were observed in the whole of the short arm of the eleventh chromosome pair, and their active NORs were homomorphic. The banded karyotypes of A. escherichii were reported in this study for the first time. Significant findings obtained in this research may contribute to cytotaxonomy of Alburnus species in Anatolian and Europe.

Karyotype and genome size in Adonis vernalis and Adonis volgensis

The comparative karyological analysis of Adonis vernalis and Adonis volgensis (Ranunculaceae) from 11 populations from Russia (Altai Territory, Novosibirsk Region, Republic of Khakassia) and Bulgaria was carried out. The somatic chromosome number was 2n = 16 in all studied plants. Chromosome sets of A. vernalis from the Altai Territory (near Sibirskiye Ogni village) and the Republic of Khakassia (Tashtipskiy District), A. volgensis from the Altai Territory (near Chernopyatovo village) and Bulgaria (Kavarna Municipality) consist of eight metacentric and eight submetacentric chromosomes. Two pairs of submetacentric chromosomes had small satellites in short arms. The karyotype formula of these plants was 2n = 2x = 16 = 8m + 4sm + 4smsat. The specimen with the chromosome rearrangement (nonreciprocal translocation) was found in the Altai Territory population. The chromosome mutation has changed the chromosome morphology of submetacentric pair to metacentric pair of different size. The karyotype formula of this specimen was 2n = 2x = 16 = 2n = 10m + 6sm. A similar mutation was previously found out in A. apennina (A. sibirica) from the Tomsk Region. The nuclear DNA content (2C-value) was determined in eight Adonis populations by flow cytometry. The average absolute nuclear DNA content in A. vernalis attained on from 18.88 ± 1.01 to 19.47 ± 1.17 pg, and in A. volgensis attained on from 16.10 ± 0.41 to 16.47 ± 0.47 pg. Differences in 2C-value between A. volgensis and A. vernalis correlated with differences in total chromosome lengths of the set.

Check-list of chromosome numbers of the family Hygromiidae (Gastropoda: Stylommatophora) with new data on Circassina frutis

Chromosome number data on the Hygromiidae (Gastropoda: Stylommatophora) are summarized and reviewed briefly in the context of the phylogeny of the family. In hygromiids, the haploid chromosome numbers range from 21 to 26. It is supposed that n = 21 is the ancestral chromosome number in the family. The modal haploid number for Hygromiidae is 23. Description of karyotype in terms of chromosome number and morphology of hygromiid land snail Circassina frutis is provided for the first time. The diploid chromosome number of this species is 2n = 46. The karyotype is symmetric and consists of 21 pairs of metacentric and 2 pairs of submetacentric chromosomes. The karyotype formula is as follows: 2n = 42m + 4sm (n = 21m + 2sm). The fundamental number (FN) is 92. Chromosomes range in length from 2.53 μm for the smallest pair to 6.00 μm for the largest pair. The total length of chromosomes in diploid complement (TCL) is 170.40 ± 3.22 μm.

Anadolu’ya endemik Squalius anatolicus (Bogutskaya, 1997) (Teleostei, Leuciscidae) türünün karyotip, C-bant ve NOR fenotipi

The karyotype and distribution of constitutive heterochromatin and nucleolus organizer regions (NORs) of Anatolian leuciscine endemic to Lake Beysehir, Squalius anatolicus (Bogutskaya, 1997) were analyzed respectively using conventional Giemsa-staining, C-banding and Ag-impregnation. Diploid chromosome number was 2n = 50 and karyotype consisted of 7 pairs of metacentric, 13 pairs of submetacentric, 5 pairs of subtelo- to acrocentric chromosomes, NF value equaled 90. Heteromorphic elements indicating sex chromosomes were not detected. C-banding revealed clear pericentromeric constitutive heterochromatin blocks in several chromosomes. Ag-impregnation revealed the size heteromorphism of NORs that covered almost the entire short arms of the middle-sized submetacentric chromosome pair. The karyotype pattern and simple NOR phenotype of S. anatolicus are nearly identical with that found not only in Squalius species analyzed to date but also in many other representatives of the Eurasian leuciscine cyprinids, which indicates remarkable chromosome stasis in this leuciscid lineage.

Chromosomal banding properties of Oxynoemacheilus simavicus (Balık & Bănărescu, 1978) (Teleostei: Nemacheilidae) from Gediz River (Turkey)

The chromosomal banding properties of Oxynoemacheilus simavicus (Balık & Bănărescu, 1978) were revealed out by C-banding and silver staining. Constitutive heterochromatin regions were determined on the pericentromeres of most chromosomes by C-banding. Otherwise, nucleolus organizer regions (NORs) were observed on the short (p) arms of one middle-sized submetacentric (sm) chromosome pair by silver staining. Also, Ag-NOR size and number polymorphisms were observed. The obtained results shall contribute to the genus Oxynoemacheilus chromosomal studies.

Contributions to the taxonomy of Trachelyopterus (Siluriformes): comparative cytogenetic analysis in three species of Auchenipteridae

ABSTRACT Auchenipteridae is divided into subfamilies Centromochlinae and Auchenipterinae. Parauchenipterus is included in the latter and is subject of taxonomic discussions concerning its validation or synonymization with Trachelyopterus. Herein, three species from two hydrographic basins were cytogenetically analyzed: Parauchenipterus striatulus from Doce River and two sympatric species, P. galeatus and Trachelyopterus coriaceus, from the Araguaia River. Diploid number of 58 chromosomes was verified for all species, but P. striatulus has different karyotype formula from the others. The three species have heterochromatin located in terminal regions of almost all chromosomes and in pericentromeric region on acrocentric chromosomes. Simple NORs was verified on a subtelocentric chromosome for all species. 5S rDNA sites were detected in three submetacentric chromosome pairs in P. striatulus; in a metacentric chromosome pair and submetacentric pair in T. coriaceus; and in one metacentric chromosome pair in P. galeatus. The similarities found in the karyotypes of the three species suggest the existence of only one genus, Trachelyopterus; therefore, our data refutes the validation of Parauchenipterus. Moreover, the differences in 5S rDNA distribution in P. galeatus in comparison with other populations already studied, indicate the existence of a new taxonomic unit, which suggests a species complex in P. galeatus.

B Chromosomes and Cytogenetic Characteristics of the Common Nase Chondrostoma nasus (Linnaeus, 1758).

Supernumerary B chromosomes (Bs) are very promising structures, among others, in that they are an additional genomic compartment for evolution. In this study, we tested the presence and frequency of B chromosomes and performed the first cytogenetic examination of the common nase (Chondrostoma nasus). We investigated the individuals from two populations in the Vistula River basin, in Poland, according to the chromosomal distribution of the C-bands and silver nucleolar organizer regions (Ag-NORs), using sequential staining with AgNO3 and chromomycin A3 (CMA3). Furthermore, we analyzed the chromosomal localization of two rDNA families (45S and 5S rDNA) using fluorescence in situ hybridization (FISH) with rDNA probes. Chondrostoma nasus individuals showed a standard (A) chromosome set consisting of 2n = 50: 12 metacentric, 32 submetacentric, and 6 acrocentric chromosomes (NF = 94). Fourteen out of the 20 analyzed individuals showed 1–2 mitotically unstable submetacentric B chromosomes of different sizes. Six of them, in 14.1% of the analyzed metaphase plates, had a single, medium-sized submetacentric B (Bsm) chromosome (2n = 51) with a heterochromatic block located in its pericentromeric region. The other seven individuals possessed a Bsm (2n = 51) in 19.4% of the analyzed metaphase plates, and a second Bsm chromosome (2n = 52), the smallest in the set, in 15.5% of metaphase plates, whereas one female was characterized by both Bsm chromosomes (2n = 52) in 14.3% of the analyzed metaphase plates. AgNORs, GC-rich DNA sites, and 28S rDNA hybridization sites were observed in the short arms of two submetacentric chromosome pairs of A set. The constitutive heterochromatin was visible as C bands in the centromeric regions of almost all Chondrostoma nasus chromosomes and in the pericentromeric region of several chromosome pairs. Two 5S rDNA hybridization sites in the pericentromeric position of the largest acrocentric chromosome pair were observed, whereas two other such sites in co-localization on a smaller pair of NOR chromosomes indicate a species-specific character. The results herein broaden our knowledge in the field of B chromosome distribution and molecular cytogenetics of Chondrostoma nasus: a freshwater species from the Leuciscidae family.

Chromosomal Metaphase Spreads with G and NOR bandings of Fresh Water Teleost, Clarias batrachus

Background,The detail structure of chromosomes depicted by their banding pattern is very useful in drawing homology and analogy in the structure of chromosome within and between the species. Results, In the present study, the diploid number of chromosomes was 50 in the fresh water teleost, Clarias batrachus in which 18 metacentric, 20 submetacentric and 12 telocentric chromosomes were observed. Structurally, the G bands revealed that transverse bands were visible after banding. These were due to the presence of heterochromatin and presence and absence of bases, these bands were observed at two pairs of submetacentric chromosomes. The NOR bands on the chromosomes were detected by silver staining in the two pairs of medium size telocentric chromosomes. It was believed that silver staining bound with the non-histone proteins of the transcriptionally active NOR region. Conclusion, Our results showed that basic information of chromosome number and morphology with G and NOR banding can be used as an important tool for cytogenetic data of fresh water teleost Clarias batrachus.

Karyotype analysis and nucleolar organizer regions (NORs) of Sundaic yellow catfish, Hemibagrus capitulum (Siluriformes, Siluridae) in Thailand

This is the first report on karyo-morphological details and characteristic of nucleolar organizer regions (NORs) of Sundaic yellow catfish, Hemibagrus capitulum (Siluriformes, Siluridae), from Sirindhorn Peat Swamp Forest, Narathiwat Province, Thailand.The mitotic chromosome preparations were prepared from kidney cells of ten male and eight female specimens. Conventional staining and Ag-NOR banding techniques were applied to stain the chromosomes. The results showed that the diploid chromosome number of H. capitulum was 2n = 56 and the fundamental number of both sexes was 108. The karyotype consists of 2 large metacentric, 8 large submetacentric, 2 large acrocentric, 18 medium metacentric, 12 medium submetacentric, 6 medium acrocentric, 4 medium telocentric, and 4 small metacentric chromosomes. None of strange size chromosomes related to sex was found. In addition, the telomeric NORs were clearly observed in the short arm of the submetacentric chromosome pair 16. The karyotype formula for H. capitulum is as follows: 2n = 56 = L2m + L8sm + L2a + M18m + M12sm + M6a + M4t + S4m.

Comparative Cytogenetics of Two Squalius Bonaparte, 1837 Species (Cypriniformes: Leuciscidae)

The karyotypes and other chromosomal characteristics of Anatolian endemic species Squalius carinus Ozulug and Freyhof (Ichthyol Explor Freshw 22(2):107–148, 2011) and S. fellowesii (Gunther, 1868) (Cypriniformes: Leuciscidae) were analysed by means of sequential Giemsa staining, C-banding and silver staining. The diploid chromosome numbers were invariably 2n = 50; their karyotypes were composed of 12 pairs of metacentric, ten pairs of submetacentric and three pairs of subtelo-acrocentric chromosomes in S. carinus, whereas ten pairs of metacentric, ten pairs of submetacentric and five pairs of subtelo-acrocentric chromosomes in S. fellowesii. No heteromorphic sex chromosomes were detected. The largest chromosome pair in their karyotypes was a subtelo-acrocentric chromosome. C-positive heterochromatins were observed on the pericentromeric regions of most of the chromosomes in the studied species. In addition, heterochromatic blocs were observed in the karyotype of S. carinus. The nucleolus organizer regions were detected terminally on the short (p) arms of single submetacentric chromosome pair in both species. Our study thus confirmed overall conservatism of leuciscin karyotypes.

Characterization of the karyotype and accumulation of repetitive sequences in Australian Darling hardyhead Craterocephalus amniculus (Atheriniformes, Teleostei).

Belonging to the order Atheriniformes, Craterocephalus is one of the most widespread genera of freshwater fishes in Australia, spanning along the northern coast from central Western Australia to central New South Wales and across the Murray-Darling and Lake Eyre basins. In this study, both conventional cytogenetic techniques (Giemsa, C-banding, CMA3/DAPI staining), and fluorescence in situ hybridization (FISH) with telomeric DNA and rDNA probes were used to examine the karyotypes and other chromosomal characteristics of Darling hardyhead (Craterocephalus amniculus) from New South Wales, Australia. We identified a diploid chromosome number 2n = 48 (NF = 58) in all studied individuals. FISH with rDNA probes showed a nonsyntenic pattern, with signals on one pair of subtelocentric chromosomes for 5S rDNA and one pair of submetacentric chromosomes for 28S rDNA. C-banding displayed the accumulation of constitutive heterochromatin in the centromeric regions of approximately 40 chromosomes. CMA3/DAPI fluorescence staining revealed extremely GC-rich signals in the pericentromeric region of one submetacentric chromosomal pair with size polymorphism. We detected telomeric signals at the end of all chromosomes and no interstitial signals.

Karyological and morphological variation within Petrosimonia brachiata Bunge in Bulgaria

We studied karyological and morphological variability of the only representative of the genus Petrosimonia (Amaranthaceae) in Bulgaria and evaluated the current state of its populations in the country. The results indicated that Bulgarian populations of Petrosimonia brachiata have a diploid chromosome number of 2n = 16. In the population from the Pomorie Lake, the karyotype consists of six pairs of metacentric and two pairs of sub-metacentric chromosomes. In the population from the Atanasovsko Lake, satellites were observed on one pair of sub-metacentric chromosomes. Statistical analysis demonstrated that the main source of phenotype variation in the species is within the populations. Vegetative traits are more variable than generative ones. No significant variability was found in the studied quantitative characteristics or pollen morphology. Given the biological type of the species (annual) and its limited distribution in Bulgaria, the status of the two populations of P. brachiata cannot be regarded as stable, and the danger of a potential threat to them in the future is a possibility not to be excluded.