Interacting effects of temperature and salinity on Bonamia sp. parasitism in the Asian oyster Crassostrea ariakensis

The proposition to introduce the Asian oyster Crassostrea ariakensis to the mid-Atlantic region of the USA is being considered with caution, particularly after the discovery of a novel microcell haplosporidian parasite, Bonamia sp., in North Carolina. Although this parasite was found to be pathogenic in C. ariakensis under warm euhaline conditions, its persistence in C. ariakensis exposed to various temperature and salinity combinations remained unresolved. In this laboratory experiment, we tested the influence of temperature in combination with a wide range of salinities (10, 20 and 30 psu) on Bonamia sp. Temperature was either changed from warm (>20 °C) to cold (6 °C for 6 weeks) and back to warm or maintained constant and warm. Warm temperature was associated with higher host mortality than cold temperature, suggesting that temperature influenced Bonamia sp. pathogenicity. The effect of salinity was revealed under warm temperature with highest mortality levels observed in infected C. ariakensis exposed to 30 psu. When temperature was increased following low-temperature exposure, Bonamia sp. was not detected; however sub-optimal experimental conditions may have contributed to this result, making it difficult to draw conclusions regarding the reemergence of the parasite after low-temperature exposure. Although the overwintering of Bonamia sp. in C. ariakensis will need to be further investigated, the results presented here suggest that Bonamia sp. may be able to persist in C. ariakensis under a combination of low temperature and meso- to euhaline salinities.     

Observation of a Bonamia sp. infecting the oyster Ostrea stentina in Tunisia, and a consideration of its phylogenetic affinities

The small non-commercial oyster Ostrea stentina co-occurs with commercially important Ostrea edulis in the Mediterranean Sea, yet its disposition with respect to the destructive pathogens Bonamia ostreae and Marteilia refringens is unknown. We began an evaluation of the Bonamia spp. infection status of O. stentina from Hammamet, Tunisia, in June 2007 using polymerase chain reaction diagnostics followed by histology and in situ hybridization. Of 85 O. stentina sampled, nine were PCR-positive for a Bonamia sp. using a Bonamia genus-specific assay; of these nine, one displayed the uninucleate microcells associated with oyster hemocytes characteristic of Bonamia spp. There was no associated pathology. DNA sequencing of the parasite from this one infected individual revealed it to be of a member of the Bonamia exitiosa/Bonamia roughleyi clade, an identification supported by positive in situ hybridization results with probes specific for members of this clade, and by the morphology of the parasite cells: nuclei were central, as in B. exitiosa, not eccentric, as in B. ostreae. There is no basis for identifying the Tunisian parasite as either B. exitiosa or B. roughleyi, however, as these species are genetically indistinguishable. Likewise, there is no basis for identifying any of the other Bonamia spp. with affinities to the B. exitiosa/B. roughleyi clade, from Argentina, Australia, Spain, and the eastern USA, as one or the other of these named species. Though they are clearly distinct from Bonamia perspora and B. ostreae, justification for drawing species boundaries among the primarily austral microcells with affinities to B. exitiosa and B. roughleyi remains elusive.     

The fine structure of the pollen wall inStrelitzia reginae (Musaceae)

The pollen wall ofStrelitzia reginae (Musaceae) consists of a nearly unsculptured, very thin, highly reduced, but coherent exine, and a thick intine (with an outer, channeled layer and an inner, largely homogeneous layer). After short, incomplete acetolysis the exine covers the remaining, severely shrinked protoplast as a folded, but unaltered “skin”, while the intine has totally disappeared. After extended acetolysis only the coherent, skin-like exine remains. Thus, the term “exine-less pollen” sometimes used for similar sporoderm structures in other genera ofZingiberales is misleading and should be substituted by the term “skin-like exine”. Surprisingly, the peculiar pollen wall ultrastructure ofStrelitzia and some otherZingiberales is very similar to that of some genera of theLaurales, an example for convergent evolution within the angiosperms.     

Effect of toluidine blue on pollen germination and pollen tube growth

Toluidine blue is known to induce gynogenic haploids in significant numbersin Populus]. Because the efficacy of a chemical in inducing gynogenesis depends largely on its effeot on pollen germination, on pollen tube growth, and on male gamete formation, the effect of toluidine blue (0, 1, 10 and 100 mgl-1) on these processes was studied in treated pistils ofSolatium nigrum (4 X), as well as on cultured pollen grains ofS. nigrum andTrigonella foenumgraecum. Irrespective of the time of application, toluidine blue (1 and 10 mg I-1) had no effect on pollen germination or pollen tube growth in pistils ofS. nigrum; at 100 mg I-1 it invariably inhibited both the processes. Almost similar responses were elicited by cultured pollen grains. InT. foenum-graecum toluidine blue had no effeot on pollen germination and suppressed tube growth. Gamete formation was inhibited, to various degrees, at all the concentrations tested; at 100 ing I-1 hardly any pollen tube showed gamete formation. Based on our results, and those on other systems, the potentiality of toluidine blue as an inducer of gynogenesis has been analysed.     

A cytological and morphometric analysis of a triploid apomict,Opuntia × Kelvinensis (subgenus Cylindropuntia,Cactaceae)

A morphometric analysis ofOpuntia spinosior, O. fulgida, and their putative hybrid,O. × kelvinensis was supplemented with cytogenetic data and pollen stainability for all OTUs. The morphometric analysis supported the hypothesis for the hybrid origin ofO.×kelvinensis and indicated that limited backcrossing has occurred betweenO.×kelvinensis andO. spinosior. Almost all individuals investigated ofO.×kelvinensis are triploid, with 33 chromosomes, those ofOpuntia fulgida are mostly diploid, but in part triploid, and all ofO. spinosior investigated are diploid. The very high percentage of sterile seed produced by triploidO.×kelvinensis is almost certainly a consequence of unequal segregation of chromosomes in pollen mother cells during anaphase I. The ability ofO.×kelvinensis to reproduce vegetatively is attributable to itsO. fulgida parentage. It is hypothesized that the success ofO.×kelvinensis is a result of its particularly preadaptive genome isolated from infrequent backcrossing via meiotic irregularities of odd-polyploidy and its ability to reproduce vegetatively.     

Development and survival ofOrius albidipennis andO. levigatus (Het.: Anthocoridae) on various diets

The effect of various diets on nymphal development and survival of two predaceous anthocorid bugs,Orius albidipennis (Reuter) andO. laevigatus (Fieber) was investigated in the laboratory. Five different diets were compared: eggs ofEphestia kuehniella Zeller; eggs ofE. kuehniella plus mixed flower pollen; only mixed flower pollen; pollen from sweet pepper (Capsicum annuum L. cv. Mazurka) flowers; and sweet pepper plants. A high percentage of predators successfully completed nymphal development on those diets containing lepidopterous eggs. When fed on sweet pepper pollen, the survival percentages were 65% forO. laevigatus and 38% forO. albidipennis. No nymphs of either species completed the nymphal stage on mixed flower pollen or on sweet pepper plants. Development was significantly faster on diets containing eggs ofE. kuehniella. Results are discussed in relation to the capability of the bugs to survive periods of prey scarcity and to the optimization of release strategies for these predators in the greenhouse.     

Observations on the big bang flowering of Miconia minutiflora (Melastomataceae)

Trees ofMiconia minutiflora produced abundant flowers for only one to three days during mid-April 1983 in the vicinity of Saül, French Guiana. They attracted large numbers of at least 14 species of bees that collected nectar or pollen or both. Nectar production is uncommon in the Melastomataceae and not previously reported forMiconia. Peak bee activity at the trees was in the morning and by afternoon most visits were limited to those bees in search of remnant pollen, especially species ofTrigona. As has been shown for other neotropical plants, heavy rains may trigger flowering in this species. It is suggested that the flowering system ofM. minutiflora promotes outcrossing because of interactions among the numerous species of bees visiting the trees and because of inter-individual variation in nectar and pollen availability. Therefore, bees may fly to other trees instead of becoming satiated with nectar or pollen from a single tree.     

Reproduction inCampanula afra (Campanulaceae): Mating system and the role of the pollen collecting hairs

The aim of the present investigation is to compare two geographically well separated populations ofC. afra with different mating systems with emphasis on (1) factors controlling the length of the male phase with special attention paid on the pollen collecting hairs, (2) crossing ability among populations with different mating systems; shouldC. afra be regarded as one or several species?, and (3) correlations between pollen germinability and mating system; how does pollen germinability vary with anthesis and stigma development? From the results it can be concluded that the length of the male phase and the development of the stigma depend on the stimulation of the pollen collecting hairs rather than on the amount of pollen removed. Furthermore, the length of the male phase was found to be correlated with the mating system, i.e., in the population with a mixed mating system, the differences between treated and untreated flowers were less pronounced than in the population being obligately outcrossing. I also found correlations between mating system and pollen germinability, where the population with a mixed mating system had a high germinability at stigma receptivity, whereas for the xenogamous population, the germinability approached zero at stigma development. No crossing incompatibility was found between the two populations ofCampanula afra in any of the combinations.     

Development and reproduction of Adalia bipunctata on factitious and artificial foods

The native coccinellid Adalia bipunctata (L.) (Coleoptera: Coccinellidae) may be an alternative to exotic species like Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) for the biological control of aphid pests in Europe. The availability of adequate factitious or artificial foods may help optimize its mass production. This study examines the nutritional value of Ephestia kuehniella Zeller (Lepidoptera: Phycitidae) eggs plus bee pollen, pea aphids Acyrthosiphum pisum (Harris) (Hemiptera: Aphididae) and mixtures of bee pollen and cysts of Artemia franciscana Kellogg (Branchiopoda: Artemiidae) and/or a lyophilized artificial diet based on bovine meat and liver. Reproducing adults of A. bipunctata were obtained on all diets tested, but immature survival, adult weights, development times and reproductive rates differed among diets. Over 84% of first instars fed on E. kuehniella eggs plus pollen or aphids survived to adulthood. Feeding predator larvae on pollen combined only with A. franciscana cysts or artificial diet yielded 40–55% immature survival, but survival increased to 74% when all of these components were mixed. Adult weights of A. bipunctata on the mixtures of pollen, A. franciscana cysts and/or artificial diet were 55–75% of those on aphids or on E. kuehniella eggs plus pollen. Lifetime fecundity was superior on E. kuehniella eggs plus pollen (1,864 eggs) to that on the other diets (264–889 eggs). The use of mixtures of plant and animal foods for A. bipunctata and other predators may contribute to increasing the cost-effectiveness of commercial mass production by reducing inputs of natural prey like aphids, or of nutritious but expensive factitious foods like lepidopteran eggs.     

Histochemical studies on the distribution of 5-nucleotidase in the germinating pollen grains ofEschscholtzia californica cham.

The present paper incorporates a detailed study on the distribution of 5-nucleotidase in the germinating pollen grains ofEschscholtzia califomica. The intense activity of this enzyme has been found in the wall of pollen grains and pollen tubes and small positive granules in the lumen of both in the pollen grains and pollen tubes. The presence of this enzyme in the wall is presumably connected with the permeability and transport process and growth regulation of the pollen tubes.     

An analysis of somatic and meiotic behaviour of chromosomes ofBowiea volubilis HARV.

A critical analysis of karyotype and meiosis ofBowiea volubilis Harv. showed normal bivalent formation with considerable irregularities in meiosis. Asynchrony is manifested to a significant extent within the anther where the range is between pollen grains and early stages of pollen mother cells.     

Gametogenesis of tobaccoin vitro

Excised anthers ofNicotiana tabacum L. were culturedin vitro at the stage of pollen tetrads, which proved in our experiments to be the most suitable initial stage for cultivation, up to the stage of mature pollen grains, using Ito and Stern's nutrient medium, or this medium supplemented with uracil. Germinating capacity of the pollen grains formed and the lengths of pollen tubes were quantitatively evaluated.     

Histochemical studies on the distribution of non-specific esterase in the germinating pollen grains ofPortulaca grandiflora

The study deals with the distribution of non-specific esterase in germinating pollen grains ofPortulaca grandiflora. Intense activity of the enzyme is seen in small granules distributed homogeneously in pollen grains stigma hairs and throughout the length of pollen tubes. Further the walls of pollen grains also demonstrate intense activity. The functional significance of the enzyme in these locales has been discussed.     

Effect of wind-borne pollens on the population dynamics ofAmblyseius hibisci [Acarina: Phytoseiidae]

Populations ofAmblyseius hibisci (Chant), an important predator of citrus red mite,Panonychus citri (McGregor) exhibited varying responses to field applications of cat-tail,Typha latifolia L., pollen in San Joaquin Valley citrus groves. Predator densities increased to significantly higher levels after pollen treatments during the fall months, and to a limited extent after late winter treatments, but not after early spring treatments. The amount of response appeared to be inversely related to the levels of natural foods present during the various seasons. Results of the wind-borne pollen monitoring studies indicated that population growth inA. hibisci was correlated with the seasonal pattern of pollen fallout. Population growth was slowest in years when pollen catches were low during the late winter and early spring, and fastest in years when peak pollen catches occurred in late winter or early spring. Population growth inA. hibisci did not appear to be markedly responsive toP. citri populations although suppression of prey densities was indicated in ca. 50% of the cases. In laboratory tests,A. hibisci reproduced through 3 generations on 11 of 23 pollens tested.     

Influence of adult diet on the fecundity and survival of the predator,Chrysopa scelestes [Neur.: Chrysopidae]

Studies were conducted in the laboratory to determine the most suitable diet for adults ofChrysopa scelestes Banks that would result in the maximum fecundity and longevity, without adversely affecting hatchability. Out of 6 adult diets tested, the died containing 40% honey and pollen grains of castor,Ricinus communis L. has influenced upon the female for production of more eggs. On an average, 796 eggs were laid in 36.83 reproductive days, this was followed by Protinex^? + fructose + pollen grains and honeydew of mealy bug,Planococcus citri (Risso) + pollen grains. The diet consisting of 40 % honey had little effect either on the per day reproduction or on the effective ovipositional period for total number of egg production. Pre-ovipositional period was observed to be extended in 40% honey followed by honeydew ofP. citri + pollen grains. Hatching of larvae was found to be not affected by various diets.

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Résumé Des études de laboratoire ont été menées dans le but de mettre au point un régime pourChrysopa scelestes Banks assurant une fécondité et une longévité maximales et n'affectant pas l'éclosion des jeunes larves. Parmi les 6 régimes essayés, celui qui contient 40 % de miel et du pollen de ricinRicinus communis L. a donné lieu à la ponte la plus abondante de la part des femelles. En moyenne, chaque femelle dépose alors 796 œufs en 36,8 j de ponte. Viennent ensuite les régimes constitués de Protinex^￡, fructose et pollen, puis du miellat de la cochenille farineusePlanococcus citri (Risso) et de pollen. La nourriture à base de 40% de miel aboutit à une fécondité totale très réduite, tant par une incidence sur la fécondité quotidienne que sur la durée de la ponte. La durée de la période de pré-oviposition subit l'allongement le plus considérable dans le cas de l'alimentation avec 40% de miel, suivi par celui que provoque le miellat deP. citri additionné de pollen. L'éclosion des jeunes larves n'a pas été influencée par les divers régimes imaginaux testés.

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Contribution No. 350/83 of I.I.H.R., Bangalore-89.     

A taxonomic study of the genusCalamagrostis on Mount Yakeishidake

Populations of seven species ofCalamagrostis growing on Mt. Yakeishidake were studied from a viewpoint of taxonomy. Four of them (C. sesquifolia, C. fauriei, C. matsumurae, C. gigas) were composed of tetraploid plants with 2n=28 and high pollen fertility.C. matsumurae andC. gigas had sympatric contacts, but no sign of their hybridization could be detected. The population ofC. sachalinensis on this mountain included hexaploids (2n=42) and octoploids (2n=56), and no obvious morphological or ecological differences could be found between them. The population ofC. sachalinensis was estimated to include various ecological races which may be continuously graded. InC. langsdorffi, only octoploid plants were found. Plants with 2n=56+0?1B were found in the population ofC. hakonensis. The pollen features of the collections ofC. langsdorffii, C. sachalinesis andC. hakonensis showed that apomictic seed formation may be more or less developed in them. Populations of these species on Mt. Yakeishidake were clearly separated morphologically. It was concluded that the populations of the seven species examined each have a unity and that strains ofC. langsdorffii, C. sachalinensis andC. hakonensis found on Mt. Yakeishidake are confined to those of a derived type.     

An autoradiographic study of RNA synthesis during maturation and germination of pollen grains ofHyoscyamus niger

Summary The pattern of RNA synthesis during maturation and germination of pollen grains ofHyoscyamus niger was studied using³H-uridine autoradiography. Incorporation of label during pollen maturation was periodic with peak RNA synthesis occurring in the uninucleate, nonvacuolate pollen grains and in the vegetative cell of the bicellular pollen grains. During the early stages of germination, isotope incorporation occurred predominantly in the nucleus of the vegetative cell with little or no incorporation in the generative cell. With the appearance of the pollen tube, incorporation of³H-uridine in the vegetative cell nucleus decreased and completely disappeared at later stages of germination. No incorporation of isotope was observed in the sperms formed in the pollen tube by the division of the generative cell. From a comparison of the results of this study with those of previous works on RNA synthesis during pollen embryogenesis in cultured anthers ofH. niger, it is concluded that in contrast to embryogenic development, there is no requirement for sustained RNA synthesis by the generative cell nucleus for normal gametophytic development.     

The functional response ofTyphlodromus pyri to its prey,Panonychus ulmi: the effect of pollen

We looked at the effect of the presence of pollen (Typha latifolia) on the functional response ofTyphlodromus pyri (Phytoseiidae) toPanonychus ulmi (Tetranychidae) in the laboratory. We found that pollen significantly reduced the predation rate but that the magnitude of the effect was not large. Over the lower range of prey densities the effect appeared to be due to a decrease in search efficiency.     

Chimborazoa (Sapindaceae), a new genus from Ecuador

Paullinia lachnocarpa has been known only from flowering and immature fruiting material collected in Ecuador. A recent collection with mature fruit shows that this biternate-leaved plant with multi-stelar stems and schizocarpic (indehiscent) fruit is best placed in its own genus,Chimborazoa. The only known species isChimborazoa lachnocarpa, which appears to be endemic to mountainous areas (1200–2000 m) in the provinces Chimborazo and Cotopaxi, Ecuador. The pollen morphology ofChimborazoa differs from that ofPaullinia. The lectotypification ofP. lachnocarpa is discussed, the new genus is described and illustrated, and a key to the genera of the Paullinieae is provided.