Nucleolar meiotic cycle in orthoptera

The evolution of nucleolar material was analyzed during spermatogenesis of two grasshopper species by using “in vivo” visualization and the silver staining method. Both nucleoli and nucleolar remnants are detectable during prophase I and absent from metaphase I until telophase I. During telophase I a great number of small silver positive masses which correspond to prenucleolar bodies (PBs) are observed covering the chromatin surface. At interkinesis these PBs coalesce to form nucleoli, which are dispersed at prophase II. Silver dots at NOR position were observed on metaphase II chromosomes. PBs reappear at telophase II and give rise to the nucleoli detected in early spermatids.This cycle is compared with those reported in plants and in some other animal species.     

Spermatogenesis and spermiogenesis in Microcotyle sp. (Microcotylidae, Monogenea)

Ultrastructural observations of spermatogenesis and spermiogenesis in Microcotyle sp. a microcotylid monogenean parasite from the gills of Hypostomus sp., are described. The spermatogonia were irregularly shaped, forming a peripheral layer of cells; spermatocytes were larger than spermatogonia and a nuclear synaptonemal complex was observed; young spermatids were joined by a central cytophore forming rosettes. Spermiogenesis was characterized by the outgrowth of a cytoplasmic protuberance, the zone of differentiation, containing the basal bodies, separated by an intercentriolar body, from which flagella grow out and fuse posteriorly with the median process. Cross sections of the anterior and the middle regions of spermatozoa revealed nuclei, mitochondria, peripheral microtubules, and paired axonemes each with a 9+1 pattern.     

Aquatic heteroptera from Mariana County, Minas Gerais, Brazil

In surveys carried out in lotic and lentic environments in Mariana County, Minas Gerais state, Brazil, 35 genera and 64 species of aquatic and semi-aquatic Heteroptera were recorded, distributed in 13 families. Thirty four species were collected in lentic environments, while in lotic environments 48 species were collected, some of them common to both environments. Nepomorpha presented the greatest number of species (45), markedly for the family Naucoridae, represented by 12 species. Among the 19 Gerromorpha species collected, eight were Veliidae and six were Gerridae.     

Meiotic chromosomes and nucleolar behavior in testicular cells of the grassland spittlebugs Deois flavopicta, Mahanarva fimbriolata and Notozulia entreriana (Hemiptera, Auchenorrhyncha)

Spittlebugs annually infest pastures and cause severe damage, representing a serious problem for the tropical American beef cattle industry. Spittlebugs are an important biotic constraint to forage production and there is a lack of cytogenetic data for this group of insects. For these reasons, we conducted this work, in which the spermatogenesis and nucleolar behavior of Deois flavopicta, Mahanarva fimbriolata and Notozulia entreriana were studied. The males possessed testes in the shape of a "bunch of grapes"; a variable number of testicular lobes per individual and polyploid nuclei composed of several heteropycnotic bodies. A heteropycnotic area was located in the periphery of the nucleus (prophase I); the chiasmata were terminal or interstitial; metaphases I were circular or linear and anaphase showed late migration of the sex chromosome. The chromosome complement had 2n = 19, except for N. entreriana (2n = 15); the spermatids were round with heteropycnotic material in the center and elongated with conspicuos chromatin. The analysis of testes after silver nitrate staining showed polyploid nuclei with three large and three smaller nucleolar bodies. Early prophase cells had an intensely stained nucleolar body located close to the chromatin and another less evident body located away from the chromatin. The nucleolar bodies disintegrated during diplotene. Silver staining occurred in two autosomes, in terminal and subterminal locations, the latter probably corresponding to the nucleolus organizer regions (NORs). The spermatids were round with a round nucleolar body and silver staining was observed in the medial and posterior region of the elongated part of the spermatid head.     

Development of silver stained structures during spermatogenesis in different genera of Formicidae

Development of silver stained structures during the spermatogenesis of Tapinoma nigerrlum, Pheidole pallidula, Tetramorium caespitum, Tetramorium semilaeve, Lasius niger and Plagiolepis schmitzii are studied. Nucleolar masses are only observed in early prophase. Obvious NORs are present in metaphase in all genera and species studied. However, there are no nucleolar Ag precipitates after metaphase. A resumption of silver stainability occurs in round spermatids. The majority of these genera present differential activity between the existing NORs. In T. nigerrimum there is primary or secondary NOR activity in all chromosomes of the complement, although there are interpopulation differences in relation to the NOR activity. In the remaining genera only certain chromosomes present NOR activity. Interpopulation genetic differences and environmental factors can cause differential activity of secondary NORs as observed in Tapinoma nigerrimum.     

Chromosomal characteristics and karyotype evolution of Oxyopidae spiders (Araneae, Entelegynae)

We made a cytogenetic analysis of four species of Oxyopidae and compared it with the karyotype data of all species of this family. In Hamataliwa sp, the mitotic cells showed 2n♂ = 26+X(1)X(2) and telocentric chromosomes. The 2n♂ = 28, which has been described for only one oxyopid spider, is the highest diploid number reported for this family. Peucetia species exhibited distinct karyotype characteristics, i.e., 2n♂ = 20+X(1)X(2) in P. flava and 2n♂ = 20+X in P. rubrolineata, revealing interspecific chromosome variability within this genus. However, both Peucetia species exhibited telocentric chromosomes. The most unexpected karyotype was encountered in Oxyopes salticus, which presented 2n♂ = 10+X in most individuals and a predominance of biarmed chromosomes. Additionally, one male of the sample of O. salticus was heterozygous for a centric fusion that originated the first chromosomal pair and exhibited one supernumerary chromosome in some cells. Testicular nuclei of Hamataliwa sp and O. salticus revealed NORs on autosomal pairs, after silver impregnation. The majority of Oxyopidae spiders have their karyotype differentiated by both reduction in diploid number chromosome number and change of the sex chromosome system to X type; however, certain species retain the ancestral chromosome constitution 2n = 26+X1X2. The most remarkable karyotype differentiation occurred in O. salticus studied here, which showed the lowest diploid number ever observed in Oxyopidae and the second lowest registered for Entelegynae spiders.     

Anisops sardeus (Heteroptera): A new expansive species in Central Europe

Although insects form a large part of the aquatic fauna worldwide, expansive species of aquatic insects are quite rare. Recently, we can observe a tendency to the range expansions in several aquatic insect species. Here, we present the first record of water bug species Anisops sardeus sardeus (Heteroptera: Notonectidae) from Slovakia. This is the northernmost record of this small-bodied backswimmer which is native to Sahelo-Sindian area, extending to Mediterranean. However, the species shows recent range expansion northward in Europe. We document the current distribution of A. s. sardeus in Slovakia and Europe, and discuss the drivers of expansion and possible impact of the alien species on resident fauna.     

Waterbugs (Heteroptera: Nepomorpha and Gerromorpha) as sources of essential n‐3 polyunsaturated fatty acids in Central Siberian ecoregions

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A New Species of the Genus Paravelia Breddin 1898 from Argentina (Heteroptera: Veliidae)

A new species of the genus Paravelia (Heteroptera: Veliidae) is described, increasing the number of species of the genus known from Argentina to three: P. platensis Berg 1883, P. paxila Drake 1957, and the new sp. P. correntina. Some ecological and statistical notes are included. Scanning electron micrographs and illustrations are provided.     

Chromosome elimination and sex determination in springtails (Insecta, Collembola).

A post-zygotic mechanism of sex determination is described in the two symphypleonans Dicyrtomina ornata (Nicolet) and Ptenothrix italica Dallai. The process consists of the loss of two sex chromosomes from the male embryo. At the end of the first meiotic division of spermatogenesis, a second chromosome elimination occurs, allowing half the secondary spermatocytes, later transformed into spermatids, to receive a complete haploid set of chromosomes. The secondary spermatocytes, which receive an incomplete set of chromosomes, degenerate. Males of the two collembolan species, therefore, produce a reduced number (50%) of spermatozoa. Females of D. ornata have 2n = 12 and males 2n = 10 chromosomes; females of P. italica have 2n = 14 and males 2n = 12 chromosomes. In both species, oogenesis proceeds normally and chromosomes pair and form chiasmata in meiotic prophase. The adaptive significance of this post-zygotic mechanism of sex determination is discussed. The mechanism seems to be a characteristic feature of the suborder Symphypleona. The neanurid Arthropleona Anurida maritima (Guérin), which was studied for comparative analysis, has 2n = 8 chromosomes and normal spermatogenesis producing haploid nuclei with four chromosomes. J. Exp. Zool. (Mol. Dev. Evol.) 285:215-225, 1999.     

Checklist of the aquatic Hemiptera (Heteroptera: Gerromorpha and Nepomorpha) of Cambodia,with descriptions of new species of Microvelia Westwood, 1834 and Ranatra Fabricius, 1790

Based on specimens (Natural History Museum Vienna, Cambodian Entomology Initiatives at the Royal University of Phnom Penh, private collection of fourth author) and based on literature, we provide a first species list of aquatic Hemiptera (Gerromorpha and Nepomorpha) of Cambodia. We studied 38 species (37 identified) and added three reliable species records from the literature. In total, we report on 41 species in 25 genera and 11 families (Belostomatidae, Gerridae, Hebridae, Helotrephidae, Hydrometridae, Mesoveliidae, Micronectidae, Naucoridae, Nepidae, Notonectidae, Veliidae). Most of these taxa are recorded from Cambodia for the first time. We describe two species as new to science: Microvelia falcata sp. n. (Veliidae) and Ranatra cardamomensis sp. n. (Nepidae). Subspecific rank is given for Cylindrostethus costalis malayensis Polhemus, 1994 stat. n. (Gerridae) that was formerly described as a distinct species.

http://zoobank.org/urn:lsid:zoobank.org:pub:C95441BD-C817-42BA-87CA-01070A4B7F17     

Four New Species of Rhagovelia (Heteroptera: Veliidae) from Minas Gerais (Brazil), with a Key to the Regional Species of the angustipes Complex

Four new species of Rhagovelia, R. ochroischion, R. turmalis, R. sbolos, and R. trianguloides, are described from Minas Gerais, Brazil, along with the previously unknown female of R. triangula Drake. A key to the Rhagovelia species of the angustipes complex known from Minas Gerais and adjacent areas is provided.     

Detection of quantitative trait loci causing abnormal spermatogenesis and reduced testis weight in the small testis (Smt) mutant mouse.

The small testis (Smt) mutant mouse is characterized by a small testis of one third to one half the size of a normal testis, and its spermatogenesis is mostly arrested at early stages of meiosis, although a small number of spermatocytes at the late prophase of meiosis and a few spermatids can sometimes be seen. We performed quantitative trait locus (QTL) analysis of these spermatogenic traits and testis weight using 221 F2 males obtained from a cross between Smt and MOM (Mus musculus molossinus) mice. At the genome-wide 5% level, we detected two QTLs affecting meiosis on chromosomes 4 and 13, and two QTLs for paired testis weight as a percentage of body weight on chromosomes 4 and X. In addition, we found several QTLs for degenerated germ cells and multinuclear giant cells on chromosomes 4, 7 and 13. Interestingly, for cell degeneration, the QTL on chromosome 13 interacted epistatically with the QTL on chromosome 4. These results reveal polygenic participation in the abnormal spermatogenesis and small testis size in the Smt mutant.     

First evidence of sex chromosome pre-reduction in male meiosis in the Miridae bugs (Heteroptera)

The karyotype and male meiosis of Macrolophus costalis Fieber (Insecta, Heteroptera, Miridae) were studied using C-banding, AgNOR-banding and DNA sequence specific fluorochrome staining. The chromosome formula of the species is 2n = 28(24+X1X2X3Y). Male meiotic prophase is characterized by a prominent condensation stage. At this stage, two sex chromosomes, "X" and Y are positively heteropycnotic and always appeared together, while in autosomal bivalents homologous chromosomes were aligned side by side along their entire length, that is, meiosis is achiasmatic. At metaphase I, "X" and Y form a pseudobivalent and orient to the opposite poles. At early anaphase I, the "X" chromosome disintegrates into three separate small chromosomes, X1, X2, and X3. Hence both the autosomes and sex chromosomes segregate reductionally in the first anaphase, and separate equationally in the second anaphase. This is the first evidence of sex chromosome pre-reduction in the family Miridae. Data on C-heterochromatin distribution and its composition in the chromosomes of this species are discussed.     

Aspects of germinal cyst and sperm development in Poecilia latipinna (Teleostei: Poeciliidae).

The structure of the testis of Poecilia latipinna is described with particular reference to Sertoli cell-germ cell relationships during development and maturation of the germinal cyst. The cyst develops when primary spermatocytes become surrounded by a single layer of Sertoli cells at the testis periphery. As spermatogenesis and then spermiogenesis proceed, the cyst moves centrally in the testis toward the ducts comprising the vasa efferentia. In addition to being a structural part of the germinal cyst, the Sertoli cells phagocytize residual bodies cast off by developing spermatids and form an association with mature bodies cast off by developing spermatids and form an association with mature sperm, which resembles that observed in mammals, before the sperm are released into the vasa efferentia as a spermatozeugmata. The results of this investigation are discussed in view of what is known concerning testis structure in other teleosts and similarities between cell functions in teleosts and mammals. It is concluded that teleost Sertoli cells, teleost lobule boundary cells and mammalian Sertoli cells are homologous.     

C-heterochromatin and extra (B) chromosome distribution in six species of the Nabis (Heteroptera, Nabidae) with the modal male karyotype 2n = 16 + XY

The basic male karyotype of the six Nabis species (Heteroptera, Nabidae) is confirmed as being 2n=16+XY. The chromosomes are holokinetic while male meiosis is achiasmatic. The sex chromosomes undergo postreduction and in second metaphase show distance pairing, registered in all nabid species examined so far. Using C-banding technique for the first time in the family Nabidae, the heterochromatin was revealed on chromosomes of six species. The species showed different amount and distribution of C-heterochromatin. Only in Nabis (Dolichonabis) limbatus did the C-bands distribution make possible the identification of every chromosome pair in the karyotype. In other species, C-bands were found in some of the autosomes and the X, localized either interstitially or at telomeres. Only the Y usually showed relative stability ofthe C-banding pattern. In four of six species, extra (B) chromosomes were observed and their behaviour in meiosis described.     

Chromosome systems in the eriococcidae (Coccoidea Homoptera)

Spermatogenesis is described in two eriococcid species and the observations are compared to those previously reported. In Gossyparia spuria the diploid chromosome number is 28 in both males and females. In the female all the chromosomes are euchromatic. In most male tissues 14 of the chromosomes are euchromatic (E) and 14 are heterochromatic (H). Prior to the first meiotic division in males the number of H chromosomes was reduced. During prophase I all the cells showed 14 E chromosomes and from 1 to over 9 H chromosomes. The range of chromosome numbers in metaphase I was similar to that in prophase I. All the chromosomes divided in anaphase I, and, following differential uncoiling at interkinesis, the E and H groups of chromosomes segregated from each other at anaphase II. Only the E groups formed sperm. The presence of a variable number of H chromosomes and a haploid number of E chromosomes in spermatogenesis suggested the presence of the multiple-D variant of the Comstockiella chromosome system. In this system some of the H chromosomes become euchromatic prior to prophase I of spermatogenesis and pair with their E homologues. All the remaining H chromosomes are thus univalents, while among the E elements, some are univalents and the rest are bivalents. The observed reduction in the number of H chromosomes in the first meiotic division which was previously attributed to pairing among the H chromosomes, is now interpreted to be the result of the return of some of the H chromosomes to a euchromatic state and to their subsequent pairing with their E homologues. Spermatogenesis in Eriococcus araucariae was similar to that of G. spuria except that the reduction in the number of H chromosomes was not as extensive. The chromosome systems of the two species are compared to those of other eriococcids and the differences are briefly discussed.Supported by grant GB1585 from the National Science Foundation, Washington, D. C.