Adilson Ariza Zacaro

Complex meiotic configuration of the holocentric chromosomes: the intriguing case of the scorpion Tityus bahiensis

Mitotic and meiotic chromosomes of Tityus bahiensis were investigated using light (LM) and transmission electron microscopy (TEM) to determine the chromosomal characteristics and disclose the mechanisms responsible for intraspecific variability in chromosome number and for the presence of complex chromosome association during meiosis. This species is endemic to Brazilian fauna and belongs to the family Buthidae, which is considered phylogenetically basal within the order Scorpiones. In the sample examined, four sympatric and distinct diploid numbers were observed: 2n = 5, 2n = 6, 2n = 9, and 2 = 10. The origin of this remarkable chromosome variability was attributed to chromosome fissions and/or fusions, considering that the decrease in chromosome number was concomitant with the increase in chromosome size and vice versa. The LM and TEM analyses showed the presence of chromosomes without localised centromere, the lack of chiasmata and recombination nodules in male meiosis, and two nucleolar organiser regions carrier chromosomes. Furthermore, male prophase I cells revealed multivalent chromosome associations and/or unsynapsed or distinctly associated chromosome regions (gaps, less-condensed chromatin, or loop-like structure) that were continuous with synapsed chromosome segments. All these data permitted us to suggest that the chromosomal rearrangements of T. bahiensis occurred in a heterozygous state. A combination of various factors, such as correct disjunction and balanced segregation of the chromosomes involved in complex meiotic pairing, system of achiasmate meiosis, holocentric nature of the chromosomes, population structure, and species dispersion patterns, could have contributed to the high level of chromosome rearrangements present in T. bahiensis.

A Comparative Cytogenetic Analysis of 2 Bothriuridae Species and Overview of the Chromosome Data of Scorpiones

The order Scorpiones is one of the most cytogenetically interesting groups within Arachnida by virtue of the combination of chromosome singularities found in the 59 species analyzed so far. In this work, mitotic and meiotic chromosomes of 2 species of the family Bothriuridae were detailed. This family occupies a basal position within the superfamily Scorpionoidea. Furthermore, review of the cytogenetic data of all previously studied scorpions is presented. Light microscopy chromosome analysis showed that Bothriurus araguayae and Bothriurus rochensis possess low diploid numbers compared with those of species belonging to closely related families. Gonadal cells examined under light and in transmission electron microscopy revealed, for the first time, that the Bothriuridae species possess typical monocentric chromosomes, and male meiosis presented chromosomes with synaptic and achiasmatic behavior. Moreover, in the sample of B. araguayae studied, heterozygous translocations were verified. The use of techniques to highlight specific chromosomal regions also revealed additional differences between the 2 Bothriurus species. The results herein recorded and the overview elaborated using the available cytogenetic information of Scorpiones elucidated current understanding regarding the processes of chromosome evolution that have occurred in Bothriuridae and in Scorpiones as a whole.

Cytogenetic analysis of Ctenostomini by C-banding and rDNA localization and its relevance to the knowledge of the evolution of tiger beetles (Coleoptera: Cicindelidae)

In this work, the first cytogenetic data on Neotropical Collyrinae is provided, by way of their karyotypes, C-banding and ribosomal genes (rDNA) localization using fluorescence in situ hybridization (FISH). The two species analysed, Ctenostoma (Procephalus) ornatum ornatum (male) and Ctenostoma (Euctenostoma) rugosum(female) showed, respectively, a diploid number of 17 and 18 chromosomes. C. ornatum ornatum has a multiple sex chromosome system ( n=7 + X1X2Y), and mitotic and meiotic metaphase cells showed rDNA gene labelling in the smallest autosomal pair. In this species, no C-bands were obtained, while C. rugosum seems to exhibit centromeric and/or interstitial C-bands in almost all chromosomes. The observation of a multiple sex chromosome system in Ctenostomini ensured the appearance of this characteristic in the hypothetical ancestral of Collyrinae and Cicindelini. The subfamily Collyrinae is not uniform in what concerns diploid chromosome number and rDNA gene localization, because C.ornatum ornatum possesses a lower chromosome number and autosomal rDNA genes when compared with the other Collyrinae species studied ( Neocollyris spp.). Independent events leading to the reduction in chromosome number might have taken place during the split of the Collyrinae into the tribes Ctenostomini and Collyrini.

Association of Ceracis cornifer (Mellié) (Coleoptera: Ciidae) with the bracket fungus Pycnoporus sanguineus (Basidiomycetes: Polyporaceae)

Two new records of Ceracis cornifer (Mellie) in the Southeast Region of Brazil are presented here, describing the association of this species with the bracket fungus Pycnoporus sanguineus. The association of other species of the Ceracis furcifer Mellie group with this fungus is discussed.

CYTOGENETICS OF THREE BRAZILIAN GONIOSOMA SPECIES: A NEW RECORD FOR DIPLOID NUMBER IN LANIATORES (OPILIONES, GONYLEPTIDAE, GONIOSOMATINAE)

Abstract Currently, 60 species of harvestmen have been karyotyped and all of these are from the Nearctic and Palearctic regions. This work is the first cytogenetic report of three gonyleptid species of the suborder Laniatores: Goniosoma aff. badium, G. proximum and G. spelaeum of the Neotropical region, from the southeastern region of Brazil. Conventional Giemsa stain chromosome preparations were obtained from embryonic cells and adult male testes. Embryo mitotic plates of G. aff. badium and G. proximum indicated 88 chromosomes, and mitotic spermatogonial plates of G. spelaeum males revealed intra- and interindividual variation of chromosome number, ranging from 92–109 chromosomes. In the three analyzed species, the mitotic chromosomes were meta- or submetacentric with no obvious sex chromosomes being identified during mitosis. Prophase I spermatocytes of G. spelaeum also revealed intra- and interindividual bivalent number variation and furthermore indicated the presence of multivalence. The karyotypes of these three Goniosoma species exhibited the largest chromosome pair with a negative heteropycnosis in the distal region of the shortest arm; chromosomes of G. spelaeum submitted to silver impregnation evidenced this negative heteropycnotic region as nucleolus organizer region (NOR). These results, when compared with cytogenetic data of other Laniatores species from the Palearctic region, indicated that a new record for diploid chromosome number probably characterize the genus Goniosoma in the Neotropical region.

Xylographus globipennis Reitter, 1911 (Coleoptera: Ciidae): A barely studied species with broad distribution in the Afrotropical region

Xylographus globipennis Reitter, 1911, a ciid beetle known only from its type locality in Eritrea, has in fact a broad distribution in the Afrotropical region. A redescription of the species is provided, including the description of its male terminalia, based on the lectotype and three paralectotypes, here designated, and specimens from several localities in Democratic Republic of the Congo and in Kenya. The geographic distribution and similarities of external morphological characters of X. globipennis to other African Xylographus species are also discussed.

First report of a parthenogenetic Grylloidea and new genus of Neoaclini (Insecta: Orthoptera: Grylloidea: Phalangopsidae: Phalangopsinae)

This study describes a new genus and species of Neoaclini cricket based on specimens collected in the Brazilian Atlantic forest. In addition to the morphological description, we also report karyotype. Ubiquepuella telytokous n. sp. represents the first recorded occurrence of parthenogenesis in Grylloidea. Although the exclusively parthenogenetic reproduction is rare in Orthoptera, we acknowledge this phenomenon in this species based on successful reproduction in the laboratory setting (i.e., approximately ten generations) despite the absence of males, indicating thelytokous parthenogenesis.

Karyotype plasticity in crickets: Numerical, morphological, and nucleolar organizer region distribution pattern of Anurogryllus sp.

Abstract Within the Orthopteran species, those of the suborder Ensifera have been rarely studied from the cytogenetic point of view, mainly due to the difficulties for taxonomic identification of its species. The Gryllidae is the second largest family of this suborder and possesses some genera, such as Anurogryllus, that occur only on the American continents. The aim of this work was to determine the karyotype characteristics, the meiotic chromosome behaviour, and the nucleolar organizer region (NOR) pattern of Anurogryllus sp (Orthoptera: Gryllidae). In the analyzed sample, high levels of numerical, morphological, and NORs polymorphisms were detected. Within five distinct karyotypes that were found, the basic karyotype of Anurogryllus sp. showed 2n(♂) = 22 + X0 with acrocentric autosomes and a metacentric X sex chromosome; furthermore, a conspicuous secondary constriction related to the NOR was present along the entire short arm on pair 5. The other four types of karyotypes arose from centric fusions between elements of pairs 1/3, 2/6, 4/7 and a NOR partial translocation from pair 5 onto the long arm terminal region of one element of the fused pair 2/6. Such intraspecific variability and the consequences of high levels of polymorphism are discussed, leading to conjectures about the mechanisms that led to these chromosome rearrangements.

Recombination nodules in coleopteran species: Palembus dermestoides (Tenebrionidae) and Epicauta atomaria (Meloidae)

This work describes the first report about the occurrence of recombination nodules (RNs) in spread pachytene cells of two species of Coleoptera: Palembus dermestoides (Tenebrionidae) and Epicauta atomaria (Meloidae). The RNs were observed in preparations contrasted with phosphotungstic acid. Considering RN morphology and its occurrence in pachytene bivalents (one per autosome bivalent) these structures were interpreted to be late RNs. P. dermestoides and E. atomaria have 2n = 20 chromosomes including an Xyp sex determination system. In spite of most frequently subtelocentric morphology observed in the autosomes of both species, the occurrence of RNs is limited only to the synaptonemal complex (SC) structure of the long arms. These findings are in agreement with those obtained using light microscopy analysis in which only one chiasma or terminalization event is observed per autosomal bivalent in early or late metaphase I cells. The RNs have the same average width of the SC of each analyzed species, a circular shape, strong electron density, and are observed mainly between the lateral elements of the SC. The RNs of P. dermestoides and E. atomaria have approximately the same average size (width), 180 ± 20 nm and 160 ± 80 nm, respectively. The absence of RNs in the short arms and its occurrence in the long arms are discussed considering the short arm pericentromeric and pro-centric heterochromatin.

Histochemical Characterization of the Embryonic Stages in Diatraea saccharalis (Lepidoptera: Crambidae)

Abstract Embryonic development in Diatraea saccharalis F. (Lepidoptera: Crambidae) has been studied by means of whole mounts, histochemical techniques, and light microscopy. Three embryonic stages were identified up to larval eclosion. In the first stage, 0–10 h, intense multiplication of energids occurred, and significant changes in RNA levels were detected in distinct zones before the start of blastulation. During the second stage, 10–24 h, new protein and RNA sites were detected in the egg’s periphery. This was probably because of migration of energids and formation of the blastula. Gastrulation occurs during this stage and is characterized by intense synthetic and mitotic processes. The third stage, 25–168 h, showed ortochromatic and metachromatic regions at the posterior pole and in the yolk, egg periphery, and body of the embryo. Organogenesis closes approximately on the sixth day when the embryo starts feeding on the remaining yolk. Its development is complete by the end of the seventh day on which the larva ecloses.