Horizontal transmission of a microsporidium from the convergent lady beetle, Hippodamia convergens Guérin-Méneville (Coleoptera: Coccinellidae), to three coccinellid species of Nova Scotia

Convergent lady beetles, Hippodamia convergens Guérin-Méneville, are a popular choice for aphid control in North America. An unidentified microsporidium was found in H. convergens adults that were purchased from a commercial insectary in 2004. This study examined egg cannibalism and egg predation as a means of horizontal transmission of the unidentified microsporidium among H. convergens larvae and three coccinellid species found in Nova Scotia: Coccinella septempunctata (seven-spotted lady beetle), C. trifasciata perplexa (three-banded lady beetle), and Harmonia axyridis (multicolored Asian lady beetle). The microsporidium was transmitted with 100% efficiency when first instars fed on microsporidia-infected eggs. Mean spore count data from smear preparations of infected beetles suggest that the infection was as heavy in C. trifasciata perplexa (a native coccinellid) (11.2 ± 0.96 spores/100 μm²) as it was in H. convergens (the natural host) (12.8 ± 1.16) but lighter in the introduced species C. septempunctata (7.5 ± 0.65) and H. axyridis (0.8 ± 0.11). For all of the beetle species examined, larval development was significantly longer for microsporidia-infected individuals than for their uninfected cohorts. The microsporidium had no effect on larval mortality. Based on the results of this study, field-collected H. convergens should be examined for microsporidia and uninfected individuals should be used to rear individuals for release in biological control programs. However, this is unlikely to happen because H. convergens are relatively easy and inexpensive to collect from their overwintering sites for redistribution.     

Fine Structure and Development of Pilosporella chapmani (Microspora: Thelohaniidae) in the Mosquito,Aedes triseriatus (Say)1

ABSTRACT. New information on the life cycle and fine structure of Pilosporella chapmani, a microsporidium of the mosquito Aedes triseriatus, is presented. Pilosporella chapmani is shown to have two sporulation sequences, one of them being involved in transovarial transmission. One sequence, involving meiosis and production of a moniliform sporogonial plasmodium, occurs in the larval fat body, resulting in eight uninucleate, spherical, and fully developed spores. The other occurs in oenocytes of adult mosquitoes and results in isolated, binucleate, elongate, and thin-walled spores. Also, for the first time, metabolic products are shown to be expelled into the surrounding host tissues through the wall of the sporocyst.     

The sporulation capable (sca) mutation of Saccharomyces cerevisiae is an allele of the SIR2 gene

Summary We have used the special properties of the spo13-1 mutation in order to study the regulation of yeast meiosis by the mating type loci. We have found that both the rme1-1 mutation and the sca mutation allow haploid meiosis in spo13-1 strains. Therefore, haploid meiosis is regulated in the same manner as diploid meiosis. Unlike rme1-1, the sca mutation allows meiosis through derepression of the silent mating type cassettes; sca strains can sporulate only because they express both MAT a and MAT information. We have found further that sca is an allele of SIR2, one of the genes involved in repression of the silent cassettes. Therefore, the RME1 gene is the only known candidate for a master negative regulator through which the MAT locus controls meiosis.     

The Ultrastructure of Spores (Protozoa: Microsporida) from Lophius americanus,the Angler Fish1

ABSTRACT. Spinal and cranial ganglia of American angler fish, Lophius americanus, are often infected with microsporidia. This protozoon elicits the formation of large, spore-filled, hypertrophied host cells, cysts. Previous reports of microsporidia in European lophiids identify the parasite as Spraguea lophii, a genus which has recently been shown to be dimorphic. The spores from L. americanus are monomorphic (2.8 × 1.5 μm) and uninucleate. Each spore contains a polar tube that forms six to nine coils. Spraguea lophii differs from the microsporidium described in L. americanus in several ways. Spraguea lophii has two spore types: a large spore (4.0 × 1.25 μm) containing a diplokaryon and three to four polar tube coils and a smaller uninucleate spore (3.5 × 1.5 μm) with five to six polar tube coils. Because of these major differences, the microsporidium from L. americanus is removed from the genus Spraguea and returned to its original genus, Glugea, as a new species, G. americanus n. sp. Other ultrastructural characteristics of G. americanus are included: the posterior vacuole encloses two distinct membranous structures; one is tubular and resembles a “glomerular tuft” and the second is lamellar and composed of concentric membrane whorls, additionally, the straight or manubroid portion of the polar tube proceeds beyond the posterior vacuole before it turns anteriorly and begins to coil.     

Natural hybridization between <Emphasis Type="Italic">Phlomis lycia</Emphasis> D. Don × <Emphasis Type="Italic">P. bourgaei</Emphasis> Boiss., (Lamiaceae) revealed by RAPD markers

Randomly Amplified Polymorphic DNA markers (RAPD) were used to assess the hybrid identity of individuals sampled as Phlomis × termessi Davis. Out of 95 primers screened, 11 primers produced reproducible amplification patterns used for discrimination of P. × termessi and their parents. Eleven primers produced 81 bands. Forty two percent of the RAPD bands existed in parents. Of the 54 bands found in P. lycia, 19 were found only in this species and 7 of these were monomorphic. Similarly, of 57 RAPD bands observed in P. bourgaei, 18 were found only in P. bourgaei and 6 of these were monomorphic. Among hybrid individuals, 35 of the 73 markers were monomorphic. Fifteen of these existed in individual parents showing that parents were homozygous for these markers. Of the 35 monomorphic bands observed among hybrid individuals, 5 were present in the samples of one of the parents and completely absent from the samples of the other; therefore, additive inheritance is indicated. Of the 5 additive bands, 1 was inherited from P. bourgaei and 4 were inherited from P. lycia. Among 38 polymorhic markers observed in hybrid individuals, 9 were new and hybrid-specific. Pollen fertility was also investigated. Mean pollen fertility for P. lycia and P. bourgaei was 93% and 97% respectively. However, mean pollen fertility for hybrids was 65% (±10.5).     

A Comparison of Spore Polypeptides in Microsporidia from a Grasshopper Control Program1

Spore polypeptide profiles of Nosema locustae and an unidentified microsporidium infecting Aulocara elliotti and Psoloessa delicatula are compared with sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis (PAGE). Unique spore polypeptide profiles are not detected for the unknown microsporidium from A. elliotti and P. delicatula whereas these profiles are distinctly different from N. locustae spore polypeptide profiles. These results indicate that the microsporidium is not a polymorphic form of N. locustae but a separate species.     

Influence of Dimilin on a microsporidian infection in the gypsy moth Lymantria dispar (L.) (Lepidoptera: Lymantriidae)

Bioassay studies were conducted to investigate the influence of Dimilin (diflubenzuron), a chitinsynthetase inhibitor used for insecticidal control of the gypsy moth, Lymantria dispar, on the development and viability of a microsporidian pathogen of L. dispar. Before or after an infection with a Nosema species, L. dispar larvae were fed Dimilin in sublethal dosages. Dimilin fed to L. dispar larvae at 0.65 ng/cm² diet surface resulted in a total larval mortality of 53%. Although the microsporidian infection alone did not cause high mortality rates (9%), mortality increased to 96% when L. dispar larvae were inoculated with both Dimilin and Nosema spores. When Dimilin was fed to the larvae 24 h before or 6 days after inoculation with the microsporidium, the number of mature spores produced was significantly reduced. When Dimilin was fed to the larvae 24 h after microsporidian inoculation, the number of spores produced was not significantly reduced. Spores that were produced in larvae after Dimilin had been ingested with the diet were less infectious than spores produced in control larvae; the experimental infection rate decreased from 94% when spores obtained from control larvae were used, to 48 or 10% when spores obtained from larvae fed Dimilin 24 h or 6 days after Nosema inoculation, respectively, were used. Mature microsporidian spores washed in Dimilin solution prior to oral inoculation, however, were as infectious as spores stored in liquid nitrogen. We have shown that Dimilin interferes with the establishment of the parasite in its host. In addition, when Nosema sp. succeeds in infecting the L. dispar host despite treatment with Dimilin, the microsporidium does not develop optimally and spore production is reduced.     

Electrophoretic evidence for the origin ofDryopteris yakusilvicola (Dryopteridaceae)

To investigate the origin of the triploid agamosporous speciesD. yakusilvicola, an electrophoretic analysis was made for five enzymes of theD. sparsa complex.Dryopteris yakusilvicola showed a monomorphic banding pattern for the five enzymes and was heterozygous in all six gene loci coding them. Comparison of enzyme banding patterns suggests that the genome ofD. yakusilvicola was derived through hybridization betweenD. sabaei and either a sexual tetraploid or an agamosporous triploid ofD. sparsa. Cytological evidence (Darnaediet al., 1989) supports the idea that of the two types ofD. sparsa the sexual tetraploid is a parent. The monomorphic pattern implies thatD. yakusilvicola originated from a single hybrid between the parental species, and that it is a neo-endemic of Yakushima Island.     

Vertical transmission and overwintering of microsporidia in the gypsy moth, Lymantria dispar

Vertical transmission and the overwintering success of three different microsporidia infecting Lymantria dispar (Lepidoptera: Lymantriidae) larvae were investigated. Endoreticulatus schubergi, a midgut pathogen, was transmitted to offspring via female and male via the egg chorion (transovum transmission). Between 8% and 29% of the emerging larvae became infected. No spores of E. schubergi were found in surface-washed eggs. Nosema lymantriae, a microsporidium that causes systemic infections, was transovarially transmitted. Between 35% and 72% of the progeny were infected. Vairimorpha disparis, a fat body pathogen, was not vertically transmitted. The infectivity of spores that overwintered in cadavers of infected L. dispar varied by species, placement in the environment, and weather conditions. Spores of E. schubergi were still infective after an eight month exposure period of cadavers on the ground. Spores of N. lymantriae and V. disparis remained highly infective only when cadavers overwintered under a more or less continuous snow cover for four months.     

Variation in daily floral display and the potential for geitonogamous pollination in two monomorphic enantiostylous Monochoria species

Mirror-image flowers (enantiostyly) have long been considered a mechanism to promote cross-pollination between flowers of alternate stylar orientation. However, in monomorphic enantiostyly, the occurrence of both left- and right-styled flowers on the same individual plant might appear to promote geitonogamy rather than outcrossing relative to the condition of dimorphic enantiostyly. We investigated daily floral display during the flowering season in two experimental populations of monomorphic enantiostylous species, Monochoria korsakowii and Monochoria vaginalis (Pontederiaceae) to assess the potential effects of floral display on geitonogamous pollination. The left- and right-styled flowers exhibited a 1:1 ratio both within individuals and populations. In M. korsakowii and M. vaginalis, 86.0% and 71.3% daily floral displays involved fewer than three flowers thus reducing the likelihood of geitonogamy. Moreover, daily displays often involved one floral form and mixed-formed with unequal ratios of left- and right-styled flowers also reducing opportunities for geitonogamy. Therefore variation in daily floral display in these two Monochoria species suggests that the impact of monomorphic enantiostyly in promoting geitonogamy will be reduced by small display sizes, or through simulating dimorphic enantiostyly.     

Epizootiology of Amblyospora connecticus (Microsporida) in Field Populations of the Saltmarsh Mosquito, Aedes cantator, and the Cyclopoid Copepod, Acanthocyclops vernalis

The natural ecology of a heterosporous microsporidium, Amblyospora connecticus was investigated at three different salt marsh habitats during 1986–1989. The parasite has a well-defined seasonal transmission cycle that occurs regularly each year and intimately involves the primary mosquito host, Aedes cantator, and the intermediate copepod host, Acanthocyclops vernalis. In the spring, the microsporidium is horizontally transmitted from the copepod, where it appears to overwinter, to the mosquito via the ingestion of haploid spores produced in the copepod. Mosquitoes develop a benign infection, and females transmit the microsporidium transovarially to their progeny via infected eggs. Oviposition occurs during the summer and infected eggs hatch synchronously in the fall causing widespread epizootics. Infected larvae die, and the cycle is completed when meiospores are released into the pool and subsequently are eaten by A. vernalis, which reappears in the fall and early winter. Amblyospora connecticus thereby persists by surviving in one of two living hosts throughout most of its life cycle rather than in the extra-corporeal environment. This represents an important survival strategy for A. connecticus as results show the salt marsh habitat to be a relatively unstable environment that is subject to periodic flooding and drying. The adaptive significance of utilizing an intermediate host in the life cycle is discussed as it directly facilitates transmission and enhances survival of the microsporidium.     

Establishment of Endoreticulatus N. G. for Pleistophora fidelis (Hostounský & Weiser, 1975) (Microsporida: Pleistophoridae) Based on the Ultrastructure of a Microsporidium in the Colorado Potato Beetle,Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae)1,2

A new genus, Endoreticulatus n. g., is described for the microsporidium Pleistophora fidelis (Hostounský & Weiser, 1975) based on light and electron microscopic studies of a microsporidium in the Colorado potato beetle, Leptinotarsa decemlineata (Say). This latter microsporidium is considered to be conspecific with P. fidelis because both isolates have been shown to be infectious for L. decemlineata where infection is limited to the epithelial cells of the midgut; both are haplokaryotic and develop as groups of sporoblasts and spores in subpersistent vacuoles in the host cell. In addition, meronts, sporonts, and spores of each isolate often occur simultaneously in a common cell, and by light microscopy they both appear similar. Ultrastructural studies of the isolate from L. decemlineata revealed that all developmental stages occur in parasitophorous vacuoles derived from cisternae of rough endoplasmic reticulum of the host cell cytoplasm. Based on the unique nature of the parasitophorous vacuole, a new genus, Endoreticulatus, is proposed for P. fidelis. The genus is compared with the other genera whose species undergo multisporous sporogony in sporophorous vesicles. In addition, the nature of the parasitophorous vacuole of Endoreticulatus fidelis (Hostounský & Weiser, 1975) n. comb. is compared with the parasitophorous vacuole known to encase various developmental stages of several other microsporidian species.     

Chromosomal differentiation withinCrocus vernus agg. (Iridaceae) in the Carpathian Mts.

Western and eastern Carpathian populations ofCrocus heuffelianus s. lat. (incl.C. scepusiensis) have 2n = 18 but differ in karyotype. While western populations are chromosomally monomorphic, eastern populations exhibit geographical karyotypic differentiation.     

Pseudacteon decapitating flies (Diptera: Phoridae): Are they potential vectors of the fire ant pathogens Kneallhazia (=Thelohania) solenopsae (Microsporidia: Thelohaniidae) and Vairimorpha invictae (Microsporidia: Burenellidae)?

Fire ant decapitating flies in the genus Pseudacteon were tested for their potential as hosts or vectors of two microsporidian pathogens of the red imported fire ant, Solenopsis invicta. Decapitating flies that attacked or were reared from S. invicta workers infected by Kneallhazia (=Thelohania) solenopsae or Vairimorpha invictae were tested for either pathogen by polymerase chain reaction (PCR) tests or visual examination for spores using phase microscopy. Three species of fire ant decapitating flies acquired the pathogen, Kneallhazia solenopsae. K. solenopsae was detected in 58% of pooled samples of Pseudacteon obtusus flies and 44% of pooled samples of Pseudacteon cultellatus that developed in K. solenopsae-infected fire ant workers. K. solenopsae was also found in 17% of pooled samples of field-collected Pseudacteon curvatus. In contrast, the microsporidium V. invictae was not detected in P. obtusus reared from V. invictae-infected S. invicta workers. Neither K. solenopsae nor V. invictae were detected in any of the hovering or ovipositing flies in the laboratory exposures, indicating no mechanical acquisition of the microsporidia occurred during oviposition activity. Greater than 92% of the P. obtusus that developed in K. solenopsae-infected ants survived and emerged as adults, thus indicating no detrimental effects of the microsporidium on pupal development and emergence. These results indicate that Pseudacteon decapitating flies may be able to vector K. solenopsae but not V. invictae among fire ants. Further tests are planned to determine if flies containing K. solenopsae are capable of transferring this pathogen either during oviposition or by being consumed by fire ant larvae.     

Meiosis in the aquatic fungusCatenaria allomycis

Summary Catenaria allomycis Couch (Blastocladiales) is an endobiotic fungal parasite primarily of species of the genusAllomyces. The life cycle ofC. allomycis contains both sexual and asexual phases. Synaptonemal complexes have been found in young developing resistant sporangia (RS) suggesting that meiosis occurs within the thick walled RS prior to syngamy. Ultrastructural evidence suggests that meiosis proceeds through pachytene in the developing RS and is arrested in diplotene of prophase I until the sporangia are induced to germinate at which time the meiotic process is completed. Quantitative nuclear counts in developing RS support the ultrastructural observations. Meiotic nuclei are characterized by polar fenestrae in the nuclear envelope and intranuclear plaque-like microtubule organizing centers (MTOC).Portion of a Ph.D. dissertation submitted by the senior author to the Graduate School, University of Georgia.     

Ultrastructural features of megasporogenesis inTorreya nucifera (Taxaceae)

In megasporogenesis ofTorreya nucifera (Taxaceae) more than one product of meiosis can start to germinate, a process previously observed inTaxus. Ultrastructural analysis ofT. nucifera revealed that this behaviour is cytologically determined by the presence of a transfer cell type wall-membrane apparatus and by the presence of uncommonly complex plasmalemmasomes in the megasporocyte. These features may determine a uniform supply of nutrients to the entire megasporocyte cytoplasm, so that after meiosis the germination potential is not restricted to the chalazal megaspore. Even if more than one product of meiosis can originate the female gametophyte in bothTaxus andTorreya, this process involves different ultrastructural aspects in the two species. In conclusion, the extension of the germination potential is a common characteristic to both species but it is most probably the result of some evolutionary convergence.     

温度对斯托克通氏烟草雄配子体形成和发育的影响

为探究低温对斯托克通氏烟草(Nicotiana stocktonii)花粉母细胞(PMC)减数分裂及其雄配子体发育过程的影响,采用卡宝品红染色法,研究不同温度条件下该材料雄配子体形成和发育的过程。结果表明:种植于昼温(31±0.5)℃、夜温(11±0.5)℃人工气候箱中的Nicotiana stocktonii花粉母细胞减数分裂过程异常现象较少,出现微核的比率较低,用新鲜成熟的花粉做萌发实验花粉萌发率较高,为(71±3)%; 而种植于昼温(25±0.5)℃、夜温(3±0.5)℃条件下的Nicotiana stocktonii开花后花药大多干瘪,用新鲜成熟花粉做萌发实验花粉萌发率低,为(13.67±3)%,花粉母细胞减数分裂过程出现染色体桥、染色体不同步、染色体断片、落后染色体等现象,存在微核的细胞比率较高。因此,Nicotiana stocktonii花粉母细胞减数分裂与小孢子发育过程易受温度影响,从而影响花粉的可育性。     

The pattern of zygotene and pachytene pairing in allotetraploid Aegilops species sharing the U genome

Allotetraploid Aegilops species sharing the U genome, Ae. columnaris (UUMM), Ae. ovata (UUMM), Ae. triaristata (UUMM), Ae. triuncialis (UUCC) and Ae. variabilis (UUSS), regularly form bivalents at metaphase I of meiosis. The pattern of zygotene and pachytene pairing was analyzed by whole-mount surface-spreading of synaptonemal complexes under the electron microscope. The data indicated that at the zygotene stage the chromosomes were almost exclusively associated as bivalents; only a few multivalents (7%) were observed. These observations are discussed in relation to mechanisms of diploidization of polyploid meiosis.     

Cytotaxonomic study on two putative hybrids in the genusDuchesnea (Rosaceae)

The karyotypes and chromosome associations at meiosis in two types of natural hybrids, 7x and 8x, betweenDuchesnea chrysantha (2x) andD. indica (12x) were investigated. The 7x hybrid had a haploid chromosome set from each parent plant, whereas the 8x hybrid was considered to have a full set ofD. chrysantha and half a set ofD. indica. In the two hybrids, the chromosomes ofD. chrysantha andD. indica conjugated only slightly at meiosis. It is probable that no common genome set between the diploidD. chrysantha and the dodecaploidD. indica exists. The present evidence indicates thatD. chrysantha andD. indica should be considered to be distinct species, although they have sometimes been treated as a single species.