Printer Friendly

Chromosomes of Crossopriza lyoni (Blackwall 1867), intraindividual numerical chromosome variation in Physocyclus globosus (Taczanowski 1874), and the distribution pattern of NORs (Araneomorphae, Haplogynae, Pholcidae).

ABSTRACT. Pholcidae (Haplogynae) encompasses 967 described species, of which only 14 have been cytogenetic analyzed. Several chromosomal features have already been described including presence of meta- and sub-metacentric chromosomes and sex determination chromosome system (SDCS) of the X, [X.sub.1][X.sub.2]Y, and [X.sub.1][X.sub.2] types, which contrast with the telo- and acrocentric chromosomes and SDCS of the [X.sub.1][X.sub.2] type typical of entelegyne spiders. To obtain further cytogenetic information for the family, we examined two pholcid species, Crossopriza lyoni (Blackwall 1867) and Physocyclus globosus (Taczanowski 1874) using both conventional staining and silver staining techniques. Crossopriza lyoni exhibited 2n = 23 = 22 + X in males and 2n = 24 = 22 + XX in females, while P. globosus showed 2n = 15 = 14 + X and 4n = 30 = 28 + 2X, both in male adults, 2n = 16 = 14 + XX in female adults and embryos, and 2n = 15 = 14 + X in male embryos. Both species revealed predominately metacentric and submetacentric chromosomes and a SDCS of the X/XX type. The cytogenetic data obtained in this work and those already recorded for C. lyoni indicate interpopulational and intraspecific numerical chromosome variation, suggesting the presence of chromosomal races or cytotypes in this species. The intraindividual numerical chromosome variation observed in male adult specimens of P. globosus may be explained by the presence of cytoplasmatic bridges between germ cells. The use of the silver staining technique to reveal the nucleolar organizer region (NOR) showed that chromosome pairs 4 and 6 and the X chromosome in C. lyoni are telomeric NOR-bearers, and that the chromosome pair 2 in P. globosus possesses a proximal NOR in the long arm.

Keywords: Chiasma, chromosome rearrangements, meiosis, syncytial, tetraploidy

**********

The family Pholcidae currently has 81 genera and 967 described species (Platnick 2007) and is included in the Haplogynae (Coddington & Levi 1991; Ramirez 2000), which is considered less morphologically derived than Entelegynae. Chromosome analyses within Pholcidae were initiated by Painter (1914) in Spermophora senoculata (Duges 1836) (as Spermophora meridionalis Hentz 1837). Due to the inefficient cytogenetic techniques of the time, Painter noted only that the chromosome complement consisted of small metacentric chromosomes and that the sex determination chromosome system (SDCS) was of the [X.sub.1][X.sub.2] type. Since then, considering the number of named species, little cytogenetic information on Pholcidae has been added to the literature. Cytogenetic data currently exist for 14 pholcid species (Table 1), which represent less than 2% of the total known. The Indian Crossopriza lyoni (Blackwall 1867) has provided the greatest amount of chromosomal data that encompassed several populations. Bole-Gowda (1958) described the presence of 2n = 27 = 13II + X with metacentric autosomes and sex chromosomes; Sharma et al. (1959) recorded 2n = 24 = 11II + [X.sub.1][X.sub.2] with metacentric autosomes and acrocentric sex chromosomes; Srivastava & Shukla (1986) observed 2n = 25 = 12II + X but did not provide any information regarding chromosome morphology, and finally Parida & Sharma (1987) and Shar ma & Parida (1987) reported the presence of 2n = 23 = 11II + X, also with no description of chromosome morphology. In Physocyclus Simon 1893, all cytogenetic described species (Physocyclus californicus Chamberlin & Gertsch 1929, Physocyclus enaulus Crosby 1926, and Physocyclus sp.) occur in the Nearctic region (Cokendolpher 1989) and show a great karyotypic uniformity in relation to diploid number (2n = 15), metacentric chromosome morphology, and X/XX sex determination chromosome system type.

Recently, cytogenetic analyses were carried out in three pholcid species. Pholcus phalangioides (Fuesslin 1775) revealed 2n = 24 = 11II + [X.sub.1][X.sub.2] in males with metacentric autosomes and acrocentric sex chromosomes (Rodriguez-Gil et al. 2002); Mesabolivar luteus (Keyserling 1891) showed 2n = 15 = 7II + X in males and 2n = 16 = 7II + XX in females with a metacentric chromosome morphology; in the male specimens of Micropholcus fauroti (Simon 1887), the diploid number was 2n = 17 = 8II + X, with the chromosomes being described as biarmed (Araujo et al. 2005b).

Existing karyotypic descriptions for pholcid species (Table 1) show that the diploid number varies from 2n = 15 to 2n = 32, that the predominant chromosome morphology is metacentric and that the most frequent SDCS is of the X/XX type. In addition to this type of SDCS, some species of this family presented [X.sub.1][X.sub.2]/[X.sub.1][X.sub.1][X.sub.2][X.sub.2] and [X.sub.1][X.sub.2]Y/[X.sub.1][X.sub.1][X.sub.2][X.sub.2] types in a decreasing succession of occurrence.

In the other 11 haplogyne families, specifically Diguetidae, Drymusidae, Dysderidae, Filistatidae, Leptonetidae, Ochyroceratidae, Plectreuridae, Scytodidae, Segestriidae, Sicariidae, and Tetrablemmidae, from which 28 species have been cytogenetically characterized (Hackman 1948; Suzuki 1954; Becak & Becak 1960; Diaz & Saez 1966a, 1966b; Benavente & Wettstein 1980; Silva 1988; Tugmon et al. 1990; Silva et al. 2002; Kral et al. 2006), the diploid number varies from 2n = 7 to 2n = 37, the predominant chromosome morphology is also metacentric, and the SDCS may be of the X (43%), [X.sub.1][X.sub.2] (26%), [X.sub.1][X.sub.2]Y (24%) or XY (7%) types.

The majority of cytogenetically analyzed araneomorph species belong to Entelegynae. Approximately 500 species of entelegyne spiders, representing nearly 30 families, have a diploid number varying between 2n = 14 and 2n = 52, a predominantly acrocentric chromosome morphology, and a SDCS of the [X.sub.1][X.sub.2] type in most species. The few cytogenetically studied species of Pholcidae and other haplogyne families exhibit karyotypic peculiarities, such as predominantly metacentric chromosome morphology and X/XX sex determination chromosome system, that contrasts with those of Entelegynae. The cytogenetic analysis of other haplogyne species will probably provide additional information that can be useful in establishing some strategies of karyotype differentiation among the species of this group and also between Haplogynae and Entelegynae.

Considering the karyotypic peculiarities of Pholcidae, the present work aims to characterize the cytogenetics of two species of this family, Crossopriza lyoni and Physocyclus globosus (Taczanowski 1874). The diploid number, chromosome morphology, SDCS type, and behavior of chromosomes during meiosis were determined with conventional staining, and the distribution pattern of the active nucleolar organizer regions (NORs) in the chromosomes was established using silver staining.

METHODS

The chromosomal characterization in C. lyoni was performed through the analysis of 27 adult specimens (24 males and 3 females); in P. globosus, 10 adult specimens (7 males and 3 females) and 12 embryos were used. The individuals of both species were collected from natural populations in the city of Rio Claro (22[degrees]05'S, 47[degrees]30'W), State of Sao Paulo, Brazil. The adult specimens were deposited in the collection of the Butantan Institute, city of Sao Paulo, State of Sao Paulo, Brazil. All analyzed adult specimens were collected in August 2003 and P. globosus embryos were collected in January 2004.

The gonadal and embryonic chromosome preparations were obtained using the technique described by Webb et al. (1978), although a few were prepared from testicles not submerged in colchicine solution. Conventional staining was performed using a 3% Giemsa solution for 12 to 15 minutes. The NOR silver staining was carried out according to the methodology described by Howell & Black (1980).

[FIGURES 1-4 OMITTED]

RESULTS

Cytogenetics of Crossopriza lyoni.--Analysis of 356 gonadal cells of C. lyoni using conventional staining revealed 2n = 23 chromosomes in the spermatogonial metaphases (Fig. 1) and 2n = 24 in the oogonial metaphases (Fig. 3), a meiotic formula of 2n = 11II = X in the spermatocytes I (Fig. 5), and the occurrence of n = 11 or n = 12 = 11 = X with metacentric and submetacentric chromosomes in the metaphases II of males (Figs. 6, 7). These data showed the occurrence of the X/XX sex determining system in C. lyoni.

The conventionally stained mitotic metaphases of C. lyoni showed chromosomes with little morphological definition (Figs. 1, 3). In these cells, the chromosome elements of pair 1 and the X sex chromosome were always easily identified as being the largest elements of the complement; the other chromosomes represented a series of gradually decreasing size. Additionally, the X chromosome was positively heteropycnotic in most gonadal metaphases and spermatogonial anaphases.

[FIGURES 5-7 OMITTED]

The silver-stained spermatogonial metaphases exhibited 5 telomeric NORs occupying the short arm of the chromosome elements of pair 4, the long arm of the chromosome elements of pair 6, and one of the arms of the metacentric X chromosome (Fig. 2). The oogonial metaphases showed only two telomeric NORs in the long arm of the pair 6 chromosomes (Fig. 4), reflecting an intersexual heterogeneity in the activity of these regions.

In the diplotene and diakinesis of the male C. lyoni specimens, the autosomal bivalents showed a regular meiotic behavior of pairing and staining, and the X chromosome appeared as an extremely large and isopycnotic univalent (Fig. 5). In these cells, most of the bivalents possessed an interstitial chiasma with a cross configuration, with the exception of bivalents 1 and 2 that showed two chiasmata, assuming a ring configuration. In some of these cells, the smallest bivalent showed a precocious separation, but exhibited a regular segregation in the subsequent meiotic phases (Fig. 5).

The metaphases II of male C. lyoni, with n = 11 or n = 12 = 11 + X, confirmed the regular reductional segregation of all the chromosomes in the preceding anaphase I and the meta- and submetacentric morphology of the chromosomes (Figs. 6, 7). In the metaphases II with n = 12, the X chromosome was identified through its large size and positive heteropycnosis.

Silver-stained spermatocytes I and II did not show NOR markings on the chromosomes. However, early prophasic nuclei I from male specimens exhibited a strongly stained nucleolus.

Conventionally stained interphasic nuclei of males and females showed one and two positive heteropycnotic chromatinic blocks, respectively, which probably corresponded to a sexual chromatin (Fig. 8). The silver staining of the interphasic nuclei of males resulted in the marking of three nucleoli (Fig. 9), corroborating the results obtained regarding the number of Ag-NOR-bearing chromosomes in the spermatogonial metaphases, i.e., pairs 4 and 6 and the X chromosome. In the inter phasic nuclei of female specimens, only one strongly stained nucleolus was observed, confirming the number of active NORs verified in the oogonial metaphases.

[FIGURES 8-9 OMITTED]

Cytogenetics of Physocyclus globosus.--The testicular cells of the 7 analyzed adult specimens of P. globosus showed intraindividual variation in the number of chromosomes, i.e., of the 208 metaphases obtained from these individuals, 125 exhibited 15 = 14 + X chromosomes (Figs. 10, 12), and 83 showed 30 = 28 + 2X chromosomes (Figs. 11, 14). Of approximately 30 spermatogonial metaphases obtained from each individual, about 60% of cells showed 15 chromosomes and about 40% possessed 30 chromosomes. The analysis of 136 oogonial and embryonic metaphases showed the occurrence of 16 = 14 + XX chromosomes (Fig. 16) in 9 females (3 adults and 6 embryos) and 15 = 14 + X chromosomes in 6 male embryos.

[FIGURES 10-11 OMITTED]

The spermatocytes of the adult specimens of P. globosus also exhibited intraindividual variation in the number of chromosomes. Spermatocytes I showed the meiotic formula 7II + X (Fig. 18) or 14II + 2X (Fig. 19) in prophase I and metaphase I; spermatocytes II exhibited 7 chromosomes (Fig. 20) or 8 = 7 + X chromosomes (Fig. 21) in the metaphases II, indicating that these came from the spermatocytes I with 7II + X. Or they possessed 15 = 14 + X chromosomes (Fig. 22), indicating that they originated from spermatocytes I with 14II + 2X.

Considering the chromosome numbers obtained in the testicular, ovarian and embryonic cells of P. globosus, the diploid number and the chromosomal sex determination system were established: 2n = 15 = 14 + X = 7II + X in males and 2n = 16 = 14 + XX = 7II + XX in females. The testicular cells with 30 = 28 + 2X = 14II + 2X were interpreted as tetraploids, indicating an intraindividual numerical chromosome variation in the male specimens of adult P. globosus.

The gonadal and embryonic somatic metaphases revealed that pairs 1, 2, 4 and 6 of the P. globosus karyotype are submetacentric, and that pairs 3, 5 and 7 and the X chromosome are metacentric (Fig. 10). The autosomal pairs could be arranged in a series of gradually decreasing size and the X chromosome was a size intermediate between chromosome pairs 1 and 2.

[FIGURES 12-17 OMITTED]

Only mitotic metaphases of males and females were subjected to silver staining, which revealed a NOR in the proximal region of the long arm of the second pair of chromosomes (Figs. 13, 15, 17). The metaphases with 2n = 15 and those with 2n = 16 exhibited a maximum number of two NOR-bearing chromosomes, while the metaphases with 30 chromosomes presented a maximum number of four NOR-bearing chromosomes; in these metaphases, the NORs were always marked in the chromosomes of pair 2.

[FIGURES 18-22 OMITTED]

In the P. globosus testicular chromosome preparations, meiocytes with 15 or 30 chromosomes were found in all the phases of meiosis I. In the subphases prophase I and metaphases I, autosomal bivalents and the X univalent always occurred, even in the cells with 30 = 14II + 2X (Figs. 18, 19). In the diplotene cells, the occurrence of an interstitial chiasma was observed in three bivalents, in the cells with 15 = 7II + X, and in six bivalents, in the cells with 30 = 14II + 2X. Metaphases II showed chromosome numbers that confirmed the reductional segregation of the chromosomes during the preceding anaphase I, including the asynaptic X chromosomes present in the cells with 30 = 14II + 2X.

The silver-stained testicular meiocytes provided no information on NORs or nucleolar material, with the exception of pachytene cells that exhibited a single strongly stained block of nucleolar material.

Conventionally stained testicular and ovarian interphasic nuclei revealed the presence of one or two large heteropycnotic-positive blocks, respectively, which are probably related to the sex chromatin (Figs. 23, 24). The occurrence of two chromatinic blocks in a few testicular interphasic nuclei (Fig. 24) suggested the presence of cells with two X chromosomes in males. Silver-stained interphasic nuclei exhibited a single marked nucleolus (Fig. 25).

[FIGURES 23-25 OMITTED]

DISCUSSION

The cytogenetical data obtained from C. lyoni and P. globosus in relation to the metacentric and submetacentric morphology of all the chromosomes of the complement and the presence of an X/XX sex determination system are similar to those described for related species belonging to the Nearctic, Neotropical, Oriental and Palearctic regions (Bole-Gowda 1958; Srivastava & Shukla 1986; Parida & Sharma 1987; Sharma & Parida 1987; Cokendolpher 1989; Araujo et al. 2005b; Kral et al. 2006). However, the studied species showed some particularities regarding chromosome number when compared with related species described in the literature.

The C. lyoni specimens analyzed in this work showed a diploid number (2n = 23 = 22 + X) similar to the one found by Parida & Sharma (1987) and Sharma & Parida (1987) in specimens from the same species from two different Indian populations. Nevertheless, this diploid number differs from those described by Bole-Gowda (1958)--2n = 27 = 26 + X, Sharma et al. (1959)--2n = 24 = 22 + [X.sub.1][X.sub.2], and Srivastava & Shukla (1986)--2n = 25 = 24 + X, for individuals belonging to other, more geographically distant Indian populations.

Chromosome rearrangements of the centric fission, followed or not by pericentric inversion, and/or centric fusion types are suggested in order to explain the interpopulational and intraspecific numerical variation found in C. lyoni. The presence of predominantly metacentric or submetacentric autosomes and of a SDCS of the [X.sub.1][X.sub.2] type, with acrocentric X chromosomes, or of the X type, with a metacentric X chromosome, corroborate such mechanisms of karyotypic differentiation.

Chromosomal variations of the diploid number have already been described for some species of entelegyne spiders, such as Agelena limbata Thorell 1897 (Agelenidae), Delena cancerides Walckenaer 1837 (Sparassidae) and Evarcha hoyi (Peckham & Peckham1883) [as Pellenes hoyi (Peckham & Peckham 1909)] (Salticidae). In each one of these species, karyotypes belonging to different populations were characterized as chromosomal races that appeared to have originated mainly by centric or tandem fusion, involving only autosomes or autosomes and sex chromosomes (Maddison 1982; Rowell 1985, 1990, 1991; Tsurusaki et al. 1993; Hancock & Rowell 1995). Likewise, the different karyotypes present in C. lyoni could represent chromosomal races or cytotypes.

There are three works that focus on the phylogeny of pholcid spiders (Huber 2000; Bruvo-Madaric et al. 2005; Astrin et al. 2006) and could be used to hypothesize the origin of the C. lyoni cytotypes. However, the study of Astrin et al. (2006) did not include Spermophora senoculata, which Bruvo-Madaric et al. (2005) considered basal to all pholcines and part of Holocneminae. Due to its type of SDCS, this species was also considered to be the most basal of all pholcid species already analyzed from the cytogenetic point of view (Kral et al. 2006). The phylogeny proposed by Huber (2000) was based on morphological characters and that of Bruvo-Madaric et al. (2005) was made using both morphological and molecular data.

Considering the phylogeny described by Bruvo-Mararic et al. (2005), S. senoculata, with 2n = 25 = 11II + [X.sub.1][X.sub.2]Y (Kral et al. 2006), is basal in relation to C. lyoni. The [X.sub.1][X.sub.2]Y system of basal pholcid species could give rise to an [X.sub.1][X.sub.2] system, such as that registered for one C. lyoni Oriental population with 2n = 24 = 11II + [X.sub.1][X.sub.2] (Sharma et al. 1959), by gradual heterochromatinization and erosion of the Y sex chromosome. Taking into account this process of SDCS differentiation, the 2n = 24 = 11II + [X.sub.1][X.sub.2] could represent the basic karyotype of C. lyoni. The other diploid numbers obtained for this species could be derived from this basic number. The process of Y sex chromosome heterochromatinization and erosion have been detected in many groups of arthropods and considered a usual event involved in SDCS evolution (White 1973; Smith & Virkki 1978; Steinemanm & Steinemanm 1998). On the other hand, the possibility of conversion of an [X.sub.1][X.sub.2]Y system into an X system, as postulated by Kral et al. (2006) for some Haplogynae species, can not be excluded, especially if we consider the 2n = 23 = 11II + X of Holocnemus caudatus (Kral et al. 2006), which represents a genus closely related to Crossopriza (Huber 2000; Bruvo-Madaric et al. 2005). If so, the C. lyoni populations with 2n = 23 = 11II + X could be ancestral.

The proposal that 2n = 24 originated the chromosomal races in C. lyoni suggests karyotypic evolution by raising or lowering the diploid number of chromosomes and an origin of the [X.sub.1][X.sub.2] sex determination chromosome system from the [X.sub.1][X.sub.2]Y system. The proposal that 2n = 23 is the ancestral condition requires an increase in the chromosome number and origin of an X system from an [X.sub.1][X.sub.2]Ysystem. These propositions differ from those elaborated by other researchers, such as Suzuki (1951, 1954), Postiglioni & Brum-Zorrila (1981), Maddison (1982), Rowell (1985, 1990) and Datta & Chatterjee (1988), in order to explain the karyotypic differentiation of most spider species.

Considering that the highest chromosome numbers occur in some less morphologically derived spider species (Mesothelae and Mygalomorphae) and that the acrocentric chromosome morphology and [X.sub.1][X.sub.2] sex determination chromosome system are the most frequent among Araneae, these researchers have suggested that the above-mentioned karyotypic characteristics would be ancestral to Araneae. Lower chromosome numbers and other types of chromosome morphology and sex determination systems, particularly of the X and [X.sub.1][X.sub.2]X3Y types, would be derived mainly from centric fusions followed or not by pericentric inversions, or by tandem fusions. Alternatively, some of these researchers postulated that the existence of an X sex determination chromosome system as an ancestral condition can not be ruled out and X chromosome centric fission from species with a metacentric X chromosome could give rise to an [X.sub.1][X.sub.2] system.

Nevertheless, cladistic analyses have indicated that Mesothelae, Mygalomorphae and Araneomorphae (Haplogynae and Entelegynae) have undergone independent processes of morphological differentiation. Independent processes also seem to have promoted the diversification between haplogyne and entelegyne spiders (Platnick et al. 1991; Griswold et al. 1999; Ramirez 2000). These data raise the possibility of an independent karyotypic differentiation in the Mesothelae, Mygalomorphae, Haplogynae and Entelegynae spiders, i.e., the karyotypic differentiation of extant spiders may occur by a raise or lowering of the basic chromosome number.

Unfortunately, we do not have enough evidence to determine the process of karyotypic differentiation among the C. lyoni cytotypes. Cytogenetical analysis of other Crossopriza species will certainly provide additional information that will allow a more secure establishment of the characteristics of the basic karyotype of the species of this genus, as well as the mechanisms involved in the origin of the chromosomal races or the cytotypes of C. lyoni.

Considering that C. lyoni is a species with a wide geographic distribution, the karyotype diversity recorded for this species is not surprising and the occurrence of other cytotypes can not be excluded. Therefore, it is not possible to disregard the hypothesis that C. lyoni represents a species complex. Cytogenetic analyses may be useful in understanding the taxonomy of this species, that is, if distinct cytotypes are sympatric and there are not hybrid karyotypes. In a few animal groups whose species are very morphologically similar, cytogenetic studies coupled with morphological analyses have promoted the discovery of new species (Silva & Yonenaga-Yassuda 1998; Bertollo et al. 2000).

In the P. globosus sample analyzed, the number of chromosomes found in females, 2n = 16 = 14 + XX, and male embryos, 2n = 15 = 14 + X, is coincident with those described by Cokendolpher (1989) for other Physocyclus species, namely P. californicus, P. enaulus and Physocyclus sp. However, an intraindividual variation in the number of chromosomes, i.e., 2n = 15 = 14 + X and 4n = 30 = 28 + 2X, was observed in the testicular cells of the adult specimens of P. globosus.

The presence of tetraploid cells in the male germ line of P. globosus is probably related to the occurrence of cytoplasmatic bridges between cells of the same cyst. These bridges form a syncytium and promote synchronization in cell division and cell differentiation (Alberti & Weinmann 1985; Alberts et al. 2002; Michalik et al. 2003). Due to some peculiarities of these cytoplasmatic bridges, cell couples from a single cyst remained connected during chromosome preparation, leading to the formation of cells that were apparently tetraploid, and of interphasic nuclei with two sexual chromatinic blocks. In fact, the chromosomes of the resulting tetraploid cells exhibited the same degree of condensation and meiotic behavior. In the pholcid Mesabolivar luteus, some diplotene cells appeared in pairs, and the authors also suggested that the organization of the testicular cells was responsible for this apparent tetraploidy (Araujo et al. 2005b).

Cokendolpher & Brown (1985) also verified the presence of a few polyploid cells in Physocyclus sp., which was attributed to the cell treatment with a colchicine solution. In P. globosus, the numerical chromosome variation was certainly not due to the cell treatment with the colchicine solution, because this variation was also observed in preparations where the cells were not subjected to this solution.

The meiotic testicular cells of C. lyoni and P. globosus showed that the autosomal bivalents and the univalent X chromosome exhibited a regular behavior similar to those described by Suzuki (1954), Bole-Gowda (1958), Cokendolpher (1989), Tugmon et al. (1990), Gorlov et al. (1995), Gorlova et al. (1997), Shyh-Hwang (1999) and Rodriguez-Gil et al. (2002) for most Araneae in terms of condensation, synapsis, chiasma number and chromosome segregation.

The occurrence of the nucleolus or NORs associated with specific chromosomes has been described in some spiders based on ultrastructural analysis of bisected testicular cells using transmission electron microscopy (Benavente & Wettstein 1980; Wise 1983) or on analysis of silver impregnated gonadal and embryonic metaphases using light microscopy (Araujo et al. 2005a; Kral et al. 2006). In these analyses, the nucleolar material was associated with the X chromosome in some haplogyne spiders, such as Dysdera crocata Koch 1838 (Dysderidae), with 2n = 11 = 10 + X (Benavente & Wettstein 1980), Ochyrocera sp. Simon 1891 (Ochyroceratidae), with 2n = 13 = 12 + X (Kral et al. 2006), Scytodes thoracica (Latreille 1802) (Scytodidae), with 2n = 19 = 18 + X (Kral et al. 2006), and Monoblemma muchmorei Shear 1978 (Tetrablemmidae), with 2n = 23 = 22 + X (Kral et al. 2006), and with autosomes of some entelegyne species, such as two autosomal bivalents of Allocosa georgicola (Walckenaer 1837) (as Lycosa georgicola) (Lycosidae, Entelegynae), with 2n = 28 = 26 + [X.sub.1][X.sub.2] (Wise 1983), and three autosomal pairs of Nephilengys cruentata (Fabricius 1775) (Nephilidae), with 2n = 22 + [X.sub.1][X.sub.1][X.sub.2][X.sub.2] (Araujo et al. 2005a).

In C. lyoni, five NORs were found occupying the telomeric regions of the pair 4, pair 6 and X chromosomes, while in P. globosus, two NORs were found in the interstitial region of the pair 2 chromosomes. The presence of a NOR in the X chromosome of C. lyoni, D. crocata, Ochyrocera sp., Scytodes thoracica, and Monoblemma muchmorei, all bearing an X/XX sex determination system type, suggests that the X chromosome can represent one of the elements that constitutes the basic NOR pattern in "Higher Haplogynes"(sensu Coddington & Levi 1991). The absence of a NOR marking in the X chromosome of P. globosus is possibly due to chromosome rearrangements or differential activation of this region. Considering the low number of species whose chromosomes have been subjected to silver staining, it is not yet possible to determine a quantitative pattern of active NORs in spiders.

The interpopulational and intraindividual numerical variations respectively found in C. lyoni and P. globosus have different origins and meanings in the two species. In C. lyoni, the interpopulational variation shows that structural chromosome rearrangements are acting upon the karyotypic evolution of this species. On the other hand, the apparent tetraploidy of the spermatogonial metaphases in P. globosus is a result of the tissue organization of the spermatogonia. Thus, variation in P. globosus seems to have no relationship to chromosomal evolution of this species, but reflects a mechanisms which guarantees that great quantities of spermatozoids are simultaneously differentiated at the moment of reproduction.

ACKNOWLEDGMENTS

We thank D. Araujo and M.C. Schneider from Universidade Estadual Paulista (UNESP), Departamento de Biologia, Rio Claro, State of Sao Paulo, Brazil, and two anonymous reviewers for comments, suggestions, and critical review of the manuscript.

Manuscript received 13 March 2006, revised 5 April 2007.

LITERATURE CITED

Alberti, G. & C. Weinmann. 1985. Fine structure of spermatozoa of some labidognath spiders (Filistatidae, Segestriidae, Dysderidae, Oonopidae, Scytodidae, Pholcidae; Araneae; Arachnida) with remarks of spermiogenesis. Journal of Morphology 185:1-35.

Alberts, B., A. Johnson, J. Lewis, M. Raff, K. Roberts & P. Walter. 2002. Molecular Biology of the Cell. Garland Science, New York. 1616 pp.

Araujo, D., D.M. Cella & A.D. Brescovit. 2005a. Cytogenetic analysis of the neotropical spider Nephilengys cruentata (Araneomorphae, Tetragnathidae): standard staining, NORs, C-bands and base-specific fluorochromes. Brazilian Journal of Biology 65:193-202.

Araujo, D., A.D. Brescovit, C.A. Rheims & D.M. Cella. 2005b. Chromosomal data of two pholcids (Araneae, Haplogynae): a new diploid number and the first cytogenetical record for the new word clade. Journal of Arachnology 33:591-596.

Astrin, J.J., B.A. Huber, M. Bernhard & C.F.C. Klu"tsch. 2006. Molecular taxonomy in pholcid spiders (Pholcidae, Araneae): evaluation of species identification methods using CO1 and 16S rRNA. Zoologica Scripta 35:441-457.

Bertollo, L.A.C., G.G. Born, J.A. Dergam, A.S. Fenocchio & O. Moreira-Filho. 2000. A biodiversity in the neotropical Erythrinidae fish, Hoplias malabaricus. Karyotypic survey, geographic distribution of cytotypes and cytotaxonomic considerations. Chromosome Research 8:603-613.

Becak, W. & M.L. Becak. 1960. Constituicao cromossomica de duas especies de aranhas do genero Loxosceles. Revista Brasileira de Biologia 20:425-427.

Benavente, R. & R. Wettstein. 1980. Ultrastructural characterization of the sex chromosomes during spermatogenesis of spiders having holocentric chromosomes and a long diffuse stage. Chromosoma 77:69-81.

Bole-Gowda, B.N. 1958. A study of the chromosomes during meiosis in twenty-two species of Indian spiders. Proceedings the Zoological Society of Bengal 11:69-108.

Bruvo-Madaric, B., B.A. Huber, A. Steinacher & G. Pass. 2005. Phylogeny of pholcid spiders (Araneae: Pholcidae): combined analysis using morphology and molecules. Molecular Phylogenetics and Evolution 37:661-673.

Coddington, J.A. & H.W. Levi. 1991. Systematics and evolution of spiders (Araneae). Annual Review of Ecology and Systematics 22:565-592.

Cokendolpher, J.C. 1989. Karyotypes of three spider species (Araneae: Pholcidae: Physocyclus). Journal of the New York Entomological Society 97:475-478.

Cokendolpher, J.C. & J.D. Brown. 1985. Air-dry method for studying chromosomes of insects and arachnids. Entomological News 96:114-118.

Datta, S.N. & K. Chatterjee. 1988. Chromosomes and sex determination in 13 araneid spiders of North-Eastern India. Genetica 76:91-99.

Diaz, M.O. & F.A. Saez. 1966a. Investigaciones citogeneticas sobre algunas species de araneidos Uruguayos. Congresso Latino Americano de Zoologia, Anais 2:3-9.

Diaz, M.O. & F.A. Saez. 1966b. Karyotypes of South-American Araneida. Memorias do Instituto Commemorativo 33:153-154.

Gorlov, I.P., O.Y. Gorlova & D.V. Logunov. 1995. Cytogenetic studies in Siberian spiders. Hereditas 122:211-220.

Gorlova, O.Y., I.P. Gorlov, E. Nevo & D.V. Logunov. 1997. Cytogenetic studies on seventeen spider species from Israel. Bulletin of the British Arachnological Society 10:249-252.

Griswold, C.E., J.A. Coddington & N.I. Platnick. 1999. Towards a phylogeny of Entelegyne spiders (Araneae, Araneomorphae, Entelegynae). Journal of Arachnology 27:53-63.

Hackman, W. 1948. Chromosomenstudien an Araneen mit besonderer Berucksichtigung der Geschlechtschromosomen. Acta Zoologica Fennica 54:1-101.

Hancock, A.J. & D.M. Rowell. 1995. A chromosomal hybrid zone in Australian huntsman spider, Delena cancerides (Araneae: Sparassidae). Evidence for a hybrid zone near Canberra, Australia. Australia Journal of Zoology 43:173-180.

Howell, W.M. & D.A. Black. 1980. Controlled silver staining of nucleolus organizer regions with protective colloidal developer: a 1-step method. Experientia 36:1014-1015.

Huber, B.A. 2000. New World pholcid species (Araneae: Pholcidae): a revision at generic level. Bulletin of the American Museum of Natural History 254:1-347.

Kral, J., J. Musilova, F. St'ahlavsky, M. Rezac, Z. Akan, R.L. Edwards, F.A. Coyle & C.R. Almerje. 2006. Evolution of the karyotype and sex chromosome systems in basal clades of araneomorph spiders (Araneae: Araneomorphae). Chromosome Research 14:859-880.

Maddison, W.P. 1982. XXXY sex chromosomes in males of the jumping spiders genus Pellenes (Araneae: Salticidae). Chromosoma 85:23-37.

Michalik, P., M.R. Gray & G. Alberti. 2003. Ultrastructural observations of spermatozoa and spermiogenesis in Wandella orana Gray, 1994 (Araneae: Filistatidae) with notes on their phylogenetic implications. Tissue & Cell 35: 325-337.

Painter, T.S. 1914. Espermatogenesis in spiders. Zoologische Jahrbucher Abteilung fur Anatomie und Ontogenie der Tiere 38:509-576.

Parida, B.B. & N.N. Sharma. 1987. Chromosome number, sex mechanism and genome size in 27 species of Indian spiders. Chromosome Information Service 43:11-13.

Platnick, N.I., J.A. Coddington, R.R. Forster & C.E. Griswold. 1991. Spinneret morphology and the phylogeny of haplogyne spiders (Araneae, Araneomorphae). American Museum Novitates 3016:1-73.

Platnick, N.I. 2007. The World Spider Catalog, Version 7.5. American Museum of Natural History, New York. Online at: http://research.amnh.org/ entomology/spiders/catalog/index.html.

Postiglioni, A. & N. Brum-Zorrilla. 1981. Karyological studies on Uruguayan spiders. II. Sex chromosomes in spiders of the genus Lycosa (Araneae: Lycosidae). Genetica 56:47-53.

Ramirez, M.J. 2000. Respiratory system morphology and the phylogeny of haplogyne spiders (Araneae, Araneomorphae). Journal of Arachnology 28:149-157.

Rodriguez-Gil, S.G., L.M. Mola, A.G. Papeschi & C.L. Scioscia. 2002. Cytogenetic heterogeneity in common haplogyne spiders from Argentina (Arachnida, Araneae). Journal of Arachnology 30:47-56.

Rowell, D.M. 1985. Complex sex-linked fusion heterozygosity in the Australian huntsman spider Delena cancerides (Araneae: Sparassidae). Chromosoma 93:169-176.

Rowell, D.M. 1990. Fixed fusion heterozygosity in Delena cancerides Walck. (Araneae: Sparassidae): an alternative to speciation by monobrachial fusion. Genetica 80:139-157.

Rowell, D.M. 1991. Chromosomal fusion and meiotic behaviour in Delena cancerides (Araneae: Sparassidae). I. Chromosome pairing and Xchromosome segregation. Genome 34:561-566.

Sharma, G.P., B.L. Gupta & R. Parshad. 1959. Cytological studies on the Indian spiders. III. An analysis of the chromosomes in the male germ cells of the spider Crossopriza lyoni (Blackwall), Fam. Pholcidae. Research Bulletin of the Panjab University 10:49-53.

Sharma, G.P. & B.B. Parida. 1987. Study of chromosome in spiders from Orissa. Pranikee 8:71-76.

Shyh-Hwang, C. 1999. Cytological studies on six species of spiders from Taiwan (Araneae: Theridiidae, Psechridae, Uloboridae, Oxyopidae, and Ctenidae). Zoological Studies 38:423-434.

Silva, D. 1988. Estudio cariotipico de Loxosceles laeta (Araneae: Loxoscelidae). Revista Peruana de Entomologia 31:9-12.

Silva, M.J. & Y. Yonenaga-Yassuda. 1998. Karyo-type and chromosomal polymorphism of an undescribed Akodon from Central Brazil, a species with the lowest known diploid chromosome number in rodents. Cytogenetics and Cell Genetics 81:46-50.

Silva, R.W., D.R. Klisiowicz, D.M. Cella, O.C. Mangili & I.J. Sbalqueiro. 2002. Differential distribution of constitutive heterochromatin in two species of brown spider: Loxosceles intermedia and Loxosceles laeta (Araneae, Sicariidae), from the metropolitan region of Curitiba, PR (Brazil). Acta Biologica Paranaense 31:123-136.

Smith, S.G. & N. Virkki. 1978. Animal Cytogenetics. 3. Insecta. 5. Coleoptera. Gebru"der Borntraeger, Berlin.

Srivastava, M.D.L. & S. Shukla. 1986. Chromosome number and sex determing mechanism in forty seven species of Indian spiders. Chromosome Information Service 41:23-26.

Steinemanm, M. & S. Steinemanm. 1998. Enigma of Y chromosome degeneration: Neo-Y and Neo-X chromosomes of Drosophila miranda a model for sex chromosome evolution. Genetica 102/ 103:409-420.

Suzuki, S. 1951. Cytological studies in spiders. I. A comparative study of the chromosomes in the family Argiopidae. Journal of Science of the Hiroshima University (B-1) 12:67-98.

Suzuki, S. 1954. Cytological studies in spiders. III. Studies on the chromosomes of fifty-seven species of spiders belonging to seventeen families, with general considerations on chromosomal evolution. Journal of Science of the Hiroshima University (B-1) 15:23-136.

Tsurusaki N., Y. Ihara & T. Arita. 1993. Chromosomes of the funnel-web spider Agelena limbata (Araneae: Agelenidae). Acta Arachnologica 42: 43-46.

Tugmon, C.R., J.D. Brown & N.V. Horner. 1990. Karyotypes of seventeen USA spiders species (Araneae, Araneidae, Gnaphosidae, Loxoscelidae, Lycosidae, Oxyopidae, Philodromidae, Salticidae and Theridiidae). Journal of Arachnology 18:41-48.

Wang, X.-Z., S.-J. Cui, Z.-L. Yang, J.-P. Wang & Y.-J. Wang. 1997. On karyotype of the Pholcus affinis (Araneae: Pholcidae). Acta Arachnologica Sinica 6:19-22.

Webb, G.C., M.J.D. White, N. Contreras & J. Cheney. 1978. Cytogenetics of the parthenogenetic grasshopper Warramaba (formerly Moraba) virgo and its bisexual relatives. IV. Chromosome banding studies. Chromosoma 67:309-339.

White, M.J.D. 1973. Animal Cytology and Evolution. 3rd Edition. Willian Clowes & Sons, London. 961 pp.

Wise, D. 1983. An electron microscope study of the karyotypes of two wolf spiders. Canadian Journal of Genetics and Cytology 25:161-168.

Rosangela Martins Oliveira, (1) Aline Carolina de Jesus, (1) Antonio Domingues Brescovit (2) and Doralice Maria Cella (1): (1) Universidade Estadual Paulista-UNESP, Instituto de Biociencias, Departamento de Biologia, Caixa Postal 199, CEP 13506-900, Rio Claro, State of Sao Paulo, Brazil. E-mail: characid@yahoo.com.br (2) Instituto Butantan, Laboratorio de Artropodes Peconhentos, Av. Vital Brasil, n. 1500; CEP 05503-900, Sao Paulo, State of Sao Paulo, Brazil
Table 1.--Cytogenetic characterized Pholcidae species with their
respective diploid numbers (2n), chromosome morphology (CM) and
biogeographical region of origin (BR). A = acrocentric;
M = metacentric; SM = submetacentric; T = telocentric. * as
Artema atlanta; ** as Pholcus affinis (Schenkel 1913); *** as
Spermophora meridionalis Hentz 1837.

 Species 2n/male CM

Artema atlanta * Walckenaer 32 = 15II + --
 1837 [X.sub.1][X.sub.2]
Crossopriza lyoni 27 = 13II + X 26M + XM
 (Blackwall 1867
C. lyoni 24 = 11II + 22M + [X.sub.1]
 [X.sub.1][X.sub.2] [X.sub.2]A
C. lyoni 25 = 12II + X --
C. lyoni 23 = 11II + X --
C. lyoni 23 = 11II + X 22M + XM
Holocnemus caudatus (Dufour 23 = 11II + X 16M + 6SM + XM
 1820
Mesabolivar luteus 15 = 7II + X 14M + XM
 (Keyserling 1891
Micropholcus fauroti 17 = 8II + X 17M or SM
 (Simon 1887
Pholcus manueli ** 25 = 12II + X A-T + XSM
 Gertsch 1937
Pholcus crypticolens 24 = 11II + 22M + [X.sub.1]
 Bosenberg & Strand 1906 [X.sub.1][X.sub.2] [X.sub.2]A
Pholcus phalangioides 24 = 11II + --
 (Fuesslin 1775 [X.sub.1][X.sub.2]
P. phalangioides 25 = 11II + 18M + 4SM +
 [X.sub.1][X.sub.2]Y [X.sub.1]M +
 [X.sub.2]SM
 + YM
Pholcus sp. 26 = 12II + --
 [X.sub.1][X.sub.2]
Physocyclus californicus 15 = 7II + X 14M + XM
 Chamberlin & Gertsch
 1929
Physocyclus enaulus 15 = 7II + X 14M + XM
 Crosby 1926
Physocyclus globosus 15 = 7II + X 6M + 8SM + XM
 (Taczanowski 1874)
Physocyclus sp. 15 = 7II + X 14M + XM
Spermophora senoculata [X.sub.1][X.sub.2] [X.sub.1]
 *** (Duges 1836) [X.sub.2]M
S. senoculata 25 = 11II + 22M + [X.sub.1]
 [X.sub.1][X.sub.2]Y [X.sub.2]YM

Species BR Authors

Artema atlanta * Walckenaer Oriental Parida & Sharma (1987);
 1837 Sharma & Parida (1987)
Crossopriza lyoni Oriental Bole-Gowda (1958)
 (Blackwall 1867
C. lyoni Oriental Sharma et al. (1959)
C. lyoni Oriental Srivastava & Shukla
 (1986)
C. lyoni Oriental Parida & Sharma (1987);
 Sharma & Parida (1987)
C. lyoni Neotropical This work
Holocnemus caudatus (Dufour Palearctic Kral et al. (2006)
 1820
Mesabolivar luteus Neotropical Araujo et al. (2005b)
 (Keyserling 1891
Micropholcus fauroti Neotropical Araujo et al. (2005b)
 (Simon 1887
Pholcus manueli ** Palearctic Xiuzhen et al. (1997)
 Gertsch 1937
Pholcus crypticolens Palearctic Suzuki (l954)
 Bosenberg & Strand 1906
Pholcus phalangioides Neotropical Rodriguez-Gil et
 (Fuesslin 1775 al. (2002)
P. phalangioides Palearctic Kral et al. (2006)
Pholcus sp. Oriental Sharma & Parida (1987)
Physocyclus californicus Nearctic Cokendolpher (1989)
 Chamberlin & Gertsch
 1929
Physocyclus enaulus Nearctic Cokendolpher (1989)
 Crosby 1926
Physocyclus globosus Neotropical This work
 (Taczanowski 1874)
Physocyclus sp. Nearctic Cokendolpher (1989)
Spermophora senoculata Nearctic Painter (1914)
 *** (Duges 1836)
S. senoculata Palearctic Kral et al. (2006)
COPYRIGHT 2007 American Arachnological Society
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2007 Gale, Cengage Learning. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Title Annotation:nucleolar organizer region
Author:Oliveira, Rosangela Martins; de Jesus, Aline Carolina; Brescovit, Antonio Domingues; Cella, Doralice
Publication:The Journal of Arachnology
Article Type:Report
Geographic Code:3BRAZ
Date:May 1, 2007
Words:6277
Previous Article:The utility of molecular markers from non-lethal DNA samples of the cites II protected "tarantula" Brachypelma vagans (Araneae, Theraphosidae).
Next Article:A novel trap to capture ballooning spiders.
Topics:

Terms of use | Privacy policy | Copyright © 2019 Farlex, Inc. | Feedback | For webmasters