The ovaries of aphids (Hemiptera,Sternorrhyncha, Aphidoidea): morphology and phylogenetic implications

The ovaries of aphids belonging to the families Eriosomatidae, Anoeciidae, Drepanosiphidae, Thelaxidae, Aphididae, and Lachnidae were examined at the ultrastructural level. The ovaries of these aphids are composed of several telotrophic ovarioles. The individual ovariole is differentiated into a terminal filament, tropharium, vitellarium, and pedicel (ovariolar stalk). Terminal filaments of all ovarioles join together into the suspensory ligament, which attaches the ovary to the lobe of the fat body. The tropharium houses individual trophocytes and early previtellogenic oocytes termed arrested oocytes. Trophocytes are connected with the central part of the tropharium, the trophic core, by means of broad cytoplasmic processes. One or more oocytes develop in the vitellarium. Oocytes are surrounded by a single layer of follicular cells, which do not diversify into distinct subpopulations. The general organization of the ovaries in oviparous females is similar to that of the ovaries in viviparous females, but there are significant differences in their functioning: (1) in viviparous females, all ovarioles develop, whereas in oviparous females, some of them degenerate; (2) the number of germ cells per ovariole is usually greater in females of the oviparous generation than in females of viviparous generations; (3) in oviparous females, oocytes in the vitellarium develop through three stages (previtellogenesis, vitellogenesis, and choriogenesis), whereas in viviparous females, the development of oocytes stops after previtellogenesis; and (4) in the oocyte cytoplasm of oviparous females, lipid droplets and yolk granules accumulate, whereas in viviparous females, oocytes accrue only lipid droplets. Our results indicate that a large number of germ cells per ovariole represent the ancestral state within aphids. This trait may be helpful in inferring the phylogeny of Aphidoidea.     

Structure of the ovaries in larvae and mature females of euholognathan stoneflies (Plecoptera)

The morphology of ovaries, oviducts and egg capsules in four species of euholognathan stoneflies was investigated. The characteristic features found were as follows: (i) numerous, long ovarioles, that open individually to the extensively folded, lateral oviducts; (ii) a thin, morphologically undifferentiated chorion; (iii) a thick gelatinous layer (extrachorion) which acts as an adhesive layer fixing the eggs to the substrate. Additionally, in the larval ovariole of Leuctra sp. the terminal filament anlage and clusters of germ cells have been found. These observations are in agreement with the classification of stonefly ovaries as primary (true) panoistic.     

Ovary structure and transovarial transmission of endosymbiotic microorganisms in Marchalina hellenica (Insecta,Hemiptera, Coccomorpha: Marchalinidae)

Szklarzewicz, T., Kalandyk‐Kolodziejczyk, M., Kot, M. and Michalik, A. 2011. Ovary structure and transovarial transmission of endosymbiotic microorganisms in Marchalina hellenica (Insecta, Hemiptera, Coccomorpha: Marchalinidae). —Acta Zoologica (Stockholm) 00 :1–9. The paired ovaries of Marchalina hellenica are composed of about 200 ovarioles of telotrophic type. In each ovariole, a trophic chamber, vitellarium and ovariolar stalk can be distinguished. The tropharia comprise trophocytes and early previtellogenic oocytes (termed arrested oocytes) or trophocytes only. The arrested oocytes are not capable of further development. In the vitellaria, single oocytes develop that are connected to the tropharium by means of broad nutritive cords. The number of germ cells (trophocytes and oocytes) constituting ovarioles is not constant and may range between 25 and 32. Numerous endosymbiotic bacteria occur in the cytoplasm of trophocytes. The endosymbionts are transported via nutritive cords to the developing oocyte. The obtained results are discussed in a phylogenetic context.     

Differences in bacterial diversity of host-associated populations of Phylloxera notabilis Pergande (Hemiptera: Phylloxeridae) in pecan and water hickory

Host‐associated differentiation (HAD) is the presence of genetically divergent, host‐associated populations. It has been suggested that microbial symbionts of insect herbivores may play a role in HAD by allowing their insect hosts to use different plant species. The objective of this study was to document if host‐associated populations of Phylloxera notabilis Pergande (Hemiptera: Phylloxeridae) in pecan and water hickory corresponded with differences in the composition of their associated bacteria. To test this hypothesis, we characterized the symbionts present in P. notabilis associated with these two tree species through metagenomic analyses using 454 sequencing. Differences in bacterial diversity were found between P. notabilis populations associated with pecan and water hickory. The bacteria, Pantoea agglomerans and Serratia marcescens, were absent in the P. notabilis water hickory population, whereas both species accounted for more than 69.72% of bacterial abundance in the pecan population.     

Structure of ovaries in ensign scale insects,the most primitive representatives of Coccomorpha (Insecta,Hemiptera)

The ovaries of Orthezia urticae and Newsteadia floccosa are paired and composed of numerous short ovarioles. Each ovariole consists of an anterior trophic chamber and a posterior vitellarium that contains one developing oocyte. The trophic chamber contains large nurse cells (trophocytes) and arrested oocytes. The total number of germ cells per ovariole (i.e., cluster) is variable, but it is always higher than 32 and less than 64. This suggests that five successive mitotic cycles of a cystoblast plus additional divisions of individual cells are responsible for the generation of the cluster. Cells of the trophic chamber maintain contact with the oocyte via a relatively broad nutritive cord. The trophic chamber and oocyte are surrounded by somatic cells that constitute the inner epithelial sheath around the former and the follicular epithelium around the latter. Anagenesis of hemipteran ovarioles is discussed in relation to the findings presented. © 1995 Wiley-Liss, Inc.     

Egg hull formation in Callochiton dentatus (Mollusca,Polyplacophora): the contribution of microapocrine secretion

Abstract. Egg hull formation during oogenesis in the chiton Callochiton dentatus does not follow the typical model of merocrine secretion involving Golgi vesicle exocytosis. Instead, microapocrine secretions are primarily responsible for egg hull formation, although merocrine secretions contribute “areolae” and the vitelline layer. Microapocrine secretion mechanisms are poorly understood, involving a different cellular pathway than is typical. Egg hull formation in C. dentatus involves two types of microapocrine secretions released by the oocyte, one of which is described here for the first time. The plesiomorphic jelly-like egg hull of chitons, as exemplified by the eggs of members of the basal order Lepidopleurida and present also in eggs of C. dentatus (Chitonida: Callichitonidae), may have evolved solely as an oocyte secretion, whereas members of some other families in the order Chitonida form their egg hulls with considerable secretory input from the follicle cells as well.     

毛蚜属Chaitophorus蚜虫(半翅目:蚜科:毛蚜亚科)与初级内共生菌Buchnera的演化关系

【目的】蚜虫体内共生菌种类丰富,二者关系十分密切。几乎所有蚜虫都具有一类专性的初级内共生菌Buchnera aphidicola,二者的专性共生关系使蚜虫-Buchnera成为研究共生关系演化的理想模型。本研究对蚜虫-Buchnera在低级阶元水平上的"平行演化假说"进行了验证。【方法】选取在杨属Populus或柳属Salix植物上营同寄主全周期生活的毛蚜属Chaitophorus蚜虫作为研究对象,基于不同来源的分子标记(蚜虫线粒体基因、核基因和内共生菌基因),运用最大似然法和贝叶斯法重建蚜虫和Buchnera的系统树,并利用Tree Map、Jane和Para Fit检验二者是否具有协同系统发生关系。【结果】Tree Map和Jane分析检测到毛蚜属蚜虫与Buchnera具有显著的共成种信号,Para Fit分析结果表明二者的总体关联极为显著。【结论】毛蚜属蚜虫与其初级内共生菌Buchnera在种级及以下水平上符合"平行演化假说",并且二者的演化关系不会受到寄主植物差异的影响。     

Microorganization of ovaries and oogenesis of Haplotaxis sp. (Clitellata: Haplotaxidae)

Ovaries of Haplotaxis sp. were studied in active and nonactive states, that is, in a sexually mature specimen and in specimens outside of the reproductive period. Two pairs of ovaries were found in segments XI and XII. Especially in the nonactive state, they were in close contact with copulatory glands. Each ovary was composed of germ cells interconnected with syncytial cysts, which were enveloped by a layer of somatic cells. Within cysts each germ cell had one ring canal connecting it to the common anuclear cytoplasmic mass called a cytophore. During oogenesis clustering germ cells differentiated into nurse cells and oocytes; thus, the oogenesis was recognized as meroistic. Vitellogenic oocytes were detached from the ovaries and continued yolk absorption within the body cavity. Because recent studies have shown the variety of ovaries and germ line cyst organization in clitellates and suggest their evolutionary conservatism at the family or subfamily level, the data presented here can be valid in understanding the phylogenetic relationships among Clitellata. In this context, ovaries found in Haplotaxis sp. resembled those of the “Tubifex” type. “Tubifex” ovaries are characteristic for numerous microdrile taxa (tubificines, limnodriloidines, propappids, lumbriculids, and leech‐like branchiobdellids) and can be regarded as the primary character for these Clitellata in which germ‐line cysts are formed during early oogenesis. As the family Haplotaxidae is currently considered to be paraphyletic and the species studied here belongs to Haplotaxidae sensu stricto, our results support the close relationship of Haplotaxidae sensu stricto to the clade consisting of Lumbriculidae, Branchiobdellida, and Hirudinida, in which lumbriculids are sister to the latter two.     

Barbronia weberi (Clitellata,Hirudinida, Salifidae) has ovary cords of the Erpobdella type

The organization of the ovaries in representative of the Salifidae (Hirudinida, Erpobdelliformes) was studied at the ultrastructural level for the first time. Like in other leeches, the ovaries of Barbronia weberi are composed of an outer envelope (i.e., an ovisac made up of two coelomic epithelia, muscle cells, and connective tissue) and several internal units, which are broadly similar to the ovary cords found in representatives of the Erpobdellidae. There are usually 6–8 ovary cords that are twisted or cambered with a narrow apical part and a broader, irregularly shaped distal end in each ovisac of B. weberi. Each ovary cord is built from somatic and germ‐line cells and the latter tend to form multicellular cysts that are equipped with a central cytoplasmic core (cytophore). There are two morphologically different subpopulations of germ‐line cells: oocytes and more numerous nurse cells. Growing oocytes form protuberances on the ovary cord surface and eventually detach from the cord and float freely in the ovisac lumen, whereas the other components of germ‐line cysts (i.e., nurse cells and cytophore) degenerate. It should be pointed out that there is a prominent gradient of germ‐cell development along the long axis of the cord. The somatic cells form the ovary cord envelope (the so‐called spongiosa cells) and also penetrate the spaces between germ‐line cells. Both kinds of the somatic cells, that is, those forming the cord envelope and the somatic cells that are associated with oocytes (follicular cells) have a well‐developed system of intercellular channels. Additionally, one prominent somatic cell, the apical cell, was found at the apical tip of each ovary cord. Because the aforementioned features of ovary cords found in B. weberi are very similar (with a few minor exceptions) to the ovary cords that have been described in Erpobdella octoculata and E. johanssoni, we propose the term “ovary cords of the Erpobdella type” for them. Our results support a close phylogenetic relationship between Salifidae and Erpobdellidae. J. Morphol. 275:479–488, 2014. © 2013 Wiley Periodicals, Inc.     

根瘤蚜对不同抗性葡萄的选择性及葡萄根系挥发性物质的鉴定

为了探讨不同抗性水平砧木及品种对根瘤蚜吸引及驱避效应以及鉴定挥发性物质组分,采用离体根段培养法测定葡萄根瘤蚜Phylloxera viticola Fitch对砧木5BB,140Ru及栽培品种巨峰的选择性,发现根瘤蚜对栽培品种巨峰的根段具有很强的选择性,至接种后3 d,67.13％的根瘤蚜优先选择巨峰;而对5BB和140Ru的选择性却很差,分别有15.29％和17.58％的根瘤蚜选择5BB及140Ru。根瘤蚜在不同品种根段上的生长发育和繁殖也存在明显差异。对砧木5BB和巨峰根系的挥发性组分进行测定,发现2个品种挥发物独有组分数量均较高,巨峰独有组分为23个,占总成分数的48.94％,5BB的独有组分为32个,占总成分数的57.14％。5BB和巨峰的共有组分为24个,主要成分均为亚油酸甲酯和反油酸甲酯,但含量有所不同,其中,5BB以倍半萜类的丁香醇及脂肪酸甲酯类的亚油酸甲酯,反油酸甲酯,棕榈油酸甲酯含量较高,高于巨峰中相应物质含量的4.23%~6.46％,而巨峰以邻苯二甲酸二丁酯及胆甾烷含量较高,分别高于5BB相应组分含量的6.81％和1.07％。结果说明葡萄根瘤蚜对不同抗性水平砧木及品种确实存在不同的选择性,并且不同抗性水平的砧木及品种的挥发性物质存在显著差异。     

The aboral ring and the development of early gonads in the echinoid Paracentrotus lividus (Echinodermata, Echinoidea)

Abstract. The development of the genital apparatus is described for the echinoid Paracentrotus lividus. This apparatus derives from the aboral ring, an annular structure that includes an inconspicuous coelom and, in juveniles, the germinal rachis. The germinal epithelium grows out from the germinal rachis, and the gonadal wall and coelom in early (tubular) gonads share similarities with their equivalents in the aboral ring. The original germinal rachis regresses to form a genital cord one cell wide in late juveniles. A genital cord was observed in a few field-collected adult individuals (>40 mm test diameter).     

Differential subcellular sequestration of proapoptotic and antiapoptotic proteins and colocalization of Bcl-x(L) with the germ plasm, in Xenopus laevis oocytes

Apoptosis is an important element of normal embryonic development and gametogenesis in invertebrate and vertebrate species. Although the components of apoptotic machinery are present in Xenopus laevis fully grown stage VI oocytes and eggs, apoptosis in the developing Xenopus ovary is limited to the somatic cells with no indication of apoptosis in the germ cells. Considering the possibility that Xenopus previtellogenic oocytes might lack the components of the apoptotic pathway, we analyzed Xenopus Stage I oocytes for the presence of the proapoptotic factors Bax and tumor suppressor p53, and antiapoptotic factors Bcl-x(L) and mitochondrial heat shock protein 60 (Hsp60). We found that pro- and antiapoptotic proteins are present in Xenopus oocytes but, surprisingly, they are located in distinct subcellular compartments with proapoptotic proteins Bax and p53 being sequestered in the oocyte nucleus and antiapoptotic protein Bcl-x(L) sequestered in the cytoplasm and highly enriched in the METRO region of the mitochondrial cloud, where it colocalized with the germ plasm, and Hsp60 colocalizing with all mitochondria. The absence of apoptosis in Xenopus early oogenesis is maybe due to differential sequestration of pro- and antiapoptotic molecules.     

Structure of the female reproductive system of the lac insect,Kerria chinensis (Sternorrhyncha,Coccoidea: Kerridae)

The ovaries of female lac insects, Kerria chinensis Mahd (Sternorrhyncha: Coccoidea: Kerridae), at the last nymphal stage are composed of several balloon‐like clusters of cystocytes with different sizes. Each cluster consists of several clusters of cystocytes arranging in rosette forms. At the adult stage, the pair of ovaries consists of about 600 ovarioles of the telotrophic‐meroistic type. An unusual feature when considering most scale insects is that the lateral oviducts are highly branched, each with a number of short ovarioles. Each ovariole is subdivided into an anterior trophic chamber (tropharium) containing six or seven large trophocytes and a posterior vitellarium harbouring one oocyte which is connected with the trophic chamber via a nutritive cord. No terminal filament is present. Late‐stage adult females show synchronized development of the ovarioles, while in undernourished females, a small proportion of ovarioles proceed to maturity.     

Evidence for host-associated clones of grape phylloxera Daktulosphaira vitifoliae (Hemiptera: Phylloxeridae) in Australia

Grape phylloxera, Daktulosphaira vitifoliae Fitch, is an important pest of grapevines (Vitis vinifera L.) (Vitaceae). Using microsatellite DNA markers it was demonstrated strong associations can exist between D. vitifoliae asexual lineages and vine host type within a vineyard. Also, in excised root bioassays, D. vitifoliae collected from three regions where different genotypic classes predominated showed host-specific differences in life table parameters of reproductive rate and intrinsic rate of increase. Lastly, comparisons of mitochondrial DNA (cytochrome oxidase I) sequences revealed that D. vitifoliae in Australia have paraphyletic origins and fall into two clades partially related to vine host usage. These findings indicate introduction of separate lineages of D. vitifoliae which have close host associations and as such, have important implications for management of this pest in Australia.     

Ultrastructural study of oogenesis in Phoronopsis harmeri (Phoronida)

Temereva, E.N., Malakhov, V.V. and Yushin, V.V. 2011. Ultrastructural study of oogenesis in Phoronopsis harmeri (Phoronida). —Acta Zoologica (Stockholm) 92 : 241–250. The successive stages of oogenesis in Phoronopsis harmeri were examined by electron microscopy methods. During the oogenesis, each oocyte is encircled by vasoperitoneal (coelomic) cells forming a follicle. The previtellogenic oocytes are small cells which accumulate ribosomes for future synthesis; their cytoplasm contains characteristic clusters of mitochondria and osmiophilic particles resembling a germ plasm of other metazoans. The cytoplasm of the vitellogenic oocytes includes numerous mitochondria, cisternae of the rough endoplasmic reticulum, Golgi bodies and annulate lamellae. The synthesis of three types of inclusions was observed: strongly osmiophilic granules (lipid droplets) as a prevalent component, distinctly larger granules surrounded by membrane (proteinaceous yolk) and numerous large vesicles with pale flocculent content. No inclusions which could be unequivocally interpreted as the cortical granules were detected. The surface of the vitellogenic oocytes is covered by microvilli which increase in number and length during development. The oogenesis in Phoronida may be interpreted as follicular because of close association of oocytes with the vasoperitoneal tissue. However, well‐developed synthetic apparatus together with a strongly developed microvillous surface and absence of endocytosis indicate a clear case of autosynthetic vitellogenesis. Thus, in phoronids, there is a combination of simply developed follicle and autosynthesis that, apparently, is plesiomorphic character.     

Organization of the mitochondrial genomes of whiteflies,aphids, and psyllids (Hemiptera,Sternorrhyncha)

Background  

With some exceptions, mitochondria within the class Insecta have the same gene content, and generally, a similar gene order allowing the proposal of an ancestral gene order. The principal exceptions are several orders within the Hemipteroid assemblage including the order Thysanoptera, a sister group of the order Hemiptera. Within the Hemiptera, there are available a number of completely sequenced mitochondrial genomes that have a gene order similar to that of the proposed ancestor. None, however, are available from the suborder Sternorryncha that includes whiteflies, psyllids and aphids.     

Diversity of bacteria associated with Hormaphidinae aphids (Hemiptera: Aphididae)

Bacteria are ubiquitous inhabitants of animals.Hormaphidinae is a particular aphid group exhibiting very diverse life history traits.However,the microbiota in this group is poorly known.In the present study,using high-throughput sequencing of bacterial 16S ribosomal RNA gene amplicons,we surveyed the bacterial flora in hormaphidine aphids and explored whether the aphid tribe,host plant and geographical distribution are associated with the distribution of secondary symbionts.The most dominant bacteria detected in hormaphidine species are heritable symbionts.As expected,the primary endosymbiont Buchnera aphidicola is the most abundant symbiont across all species and has cospeciated with its host aphids.Six secondary symbionts were detected in Hormaphidinae.Arsenophonus is widespread in Hormaphidinae species,suggesting the possibility of ancient acquisition of this symbiont.Ordination analyses and statistical tests show that the symbiont composition does not seem to relate to any of the aphid tribes,host plants or geographical distributions,which indicate that horizontal transfers might occur for these symbionts in Hormaphidinae.Correlation analysis exhibits negative interference between Buchnera and coexisting secondary symbionts,while the interactions between different secondary symbionts are complicated.These findings display a comprehensive picture of the microbiota in Hormaphidinae and may be helpful in understanding the symbiont diversity within a group of aphids.     

Ovarian Structure in Milnesium tardigradum (Tardigrada, Milnesiidae) during Early Vitellogenesis

The ultrastructure of the ovary of Milnesium tardigradum during early vitellogenesis is described. Within the ovary, there were large multinuclear cells surrounded by many mononuclear oocytes. Observation of serial sections revealed four multinuclear cells that were connected to each other by cytoplasmic bridges. Each peripheral oocyte was connected to the multinuclear cell. An enormous ER-like structure was conspicuous in the centre of the multinuclear cell. The presence of large numbers of lipid droplets and yolk granules in both multinuclear cells and many mononuclear oocytes suggested a role as nurse cells. A small number of these oocytes grow to be eggs. The structural features of the multinuclear nurse cell were compared with other known examples.     

Ecological and genetic aspects of grape phylloxera Daktulosphaira vitifoliae (Hemiptera: Phylloxeridae) performance on rootstock hosts

Performance and genetic variability of clonal lineages derived from one Californian and one German population of grape phylloxera, Daktulosphaira vitifoliae Fitch were studied on their natal grape rootstock host and on three novel hosts over four generations in an aseptic dual culture system. The ability of D. vitifoliae to adapt to new hosts was measured by changes in fitness (rm) over four generations. The performance of a given clonal lineage changed over successive generations, depending upon the host plant and the phylloxera group. Analysis of amplified fragment length polymorphism-polymerase chain reaction (AFLP-PCR) banding patterns from 40 individual parthenogenetic D. vitifoliae revealed equal levels of genetic variation both among the four clonal lineages analysed and within the different generations of one lineage. Analysis of molecular variance (AMOVA) showed no significant differences between the D. vitifoliae lineages reared on different host plants, nor was a correlation between host performance and genotype found.