Involvement of trichothecenes in fusarioses of wheat, barley and maize evaluated by gene disruption of the trichodiene synthase (Tri5) gene in three field isolates of different chemotype and virulence

Fusarium graminearum is the main causative agent of Fusarium head blight on small grain cereals and of ear rot on maize. The disease leads to dramatic yield losses and to an accumulation of mycotoxins. The most dominant F. graminearum mycotoxins are the trichothecenes, with deoxynivalenol and nivalenol being the most prevalent derivatives. To investigate the involvement of trichothecenes in the virulence of the pathogen, the gene coding for the initial enzyme of the trichothecene pathway was disrupted in three field isolates, differing in chemotype and in virulence. From each isolate three individual disruption mutants were tested for their virulence on wheat, barley and maize. Despite the different initial virulence of the three wild-type progenitor strains on wheat, all disruption mutants caused disease symptoms on the inoculated spikelet, but the symptoms did not spread into other spikelets. On barley, the trichothecene deficient mutants showed no significant difference compared to the wild-type strains: all were equally aggressive. On maize, mutants derived from the NIV-producing strain caused less disease than their wild-type progenitor strain, while mutants derived from DON-producing strains caused the same level of disease as their progenitor strains. These data demonstrate that trichothecenes influence the virulence of F. graminearum in a highly complex manner, which is strongly host as well as moderately chemotype specific.     

Comparison of routine metabolic rates of the stygobite, Gammarus acherondytes (Amphipoda: Gammaridae) and the stygophile, Gammarus troglophilus

1. Reduced metabolic rate among cave organisms compared with surface species has long been suggested as an adaptation to food shortage in cave environments. However, comparisons of metabolic rates between species have not often included closely related surface and cave species. By measuring metabolic rate across three seasons and over a range of body sizes, we examined the hypothesis that the routine metabolic rate of Gammarus acherondytes, a federally listed stygobitic amphipod, is lower than that of the closely related stygophilic Gammarus troglophilus. To determine if human activities increased the supply of organic matter to caves, we also examined the relationship between residential development and bacterial contamination in water wells. 2. For G. acherondytes, the slope of the overall relationship between oxygen consumption and body dry mass did not differ from zero and did not vary seasonally, whereas for G. troglophilus it was positive and higher in summer than in winter and spring. These results provide insights into a potential novel metabolic adaptation among stygobites. Higher metabolic rate in young G. acherondytes would allow efficient use of typically transient energy sources and a low metabolic rate at larger body sizes would increase survival through periods of food scarcity. 3. The number of wells with faecal coliform contamination was weakly but positively correlated with the number of residential building permits, indicating that surface land‐use changes probably increase the availability of energy in groundwater systems inhabited by G. acherondytes. This may give stygophilic animals, with higher metabolic rates, a competitive advantage in the caves, thus reducing the abundance of stygobites such as G. acherondytes.     

Food quality for Daphnia in humic and clear water lakes

1. Growth and reproduction of Daphnia fed lake seston were measured in two categories of meso‐ to eutrophic lakes differing with respect to terrestrial organic matter influence (humic and clear water lakes). The content of highly unsaturated fatty acids (HUFA), P and N, as well as the taxonomical composition of seston were analysed. 2. Seston HUFA and C : P ratios were similar between lake categories, whereas C : N ratios were lower in the clear water lakes in both spring and summer. Despite the similarity in HUFA and P content of seston, Daphnia growth rate, clutch size and the proportion of gravid females were, respectively, about 1.5, 3 and 6 times higher in the clear water lakes. 3. Differences in growth and reproduction were related to a combination of higher N content and good fatty acid quality of the seston in the clear water lakes. Relatively high biomass of edible algae, such as Rhodomonas sp. and Cryptomonas sp., in the clear water lakes, and differences in water pH likely contributed to the observed differences in Daphnia growth and reproduction between lake categories. Additionally, it is possible that Daphnia was energy limited in the humic lakes despite high particulate organic carbon (POC) concentrations, as the contribution of non‐algal and detrital C to the POC pool was high. 4. Our results suggest that dietary HUFA content has the potential to improve herbivore growth and reproduction if N and P are not limiting. N merits more attention in studies of zooplankton nutrition.     

Invasions and niche width: does niche width of an introduced crayfish differ from a native crayfish?

1. Human activities have promoted the spread of species worldwide. Several crayfish species have been introduced into new areas, posing a threat to native crayfish and other biota. Invader success may depend on the ability to utilise a wide variety of habitats and resources. Successful invaders are generally expected to have broader niches and to be more plastic than non-invasive species.
2. Using stable isotope ratios of carbon and nitrogen we compared the niche widths of native noble crayfish and introduced signal crayfish, a successful invader of Swedish streams. The calculation of niche width took account of between-site differences in basal resource isotope signature ranges. We also assessed whether population density, prey biomass or prey diversity affected niche width.
3. At the species level, signal crayfish had twice the niche width of noble crayfish. However, individual populations of noble crayfish and signal crayfish in Swedish streams had similar niche widths. This suggests that signal crayfish has greater plasticity with respect to habitat utilisation and feeding than noble crayfish. Niche width in both species correlated positively with benthic invertebrate biomass and diversity, indicating that animal food sources are important for crayfish.
4. We find that assessing niche width in relation to invader success can be a useful tool trying to predict the impact of invasions on different scales. The findings in this study suggest that invaders and natives will have a similar impact on the stream scale whereas the invader will have a larger impact on the regional scale due to the ability to utilise a wider range of streams.     

金黴菌發酵過程中的代謝變化

在兩種培養基中觀察了金黴菌培養過程中pH的變化、葡萄糖的消耗,氮的同化、金黴素的產生、氨和有機酸濃度的變化、菌絲的呼吸等代謝變化,這兩種培養基的區別,即在一種培養基中另加入肉湯粉和玉蜀黍漿。 兩種培養基發酵過程中,葡萄糖的消耗,氮的同化,氨和金黴素的產生等變化的一般趨勢,大致相似。加肉湯粉和玉蜀黍漿的培養基中,產生的金黴素量均為不加的5倍。 兩種培養基發酵過程中,有機酸的產生和菌絲的呼吸變化的趨勢有顯著不同。含肉湯粉和玉蜀黍漿的培養基中,培養出的菌絲有兩種類型:一種淺色的氧化代謝特強,另一種菌絲深褐色的呼吸低,代謝變化屬於發酵型,但兩種類型的金黴素的產生量是一樣的。在搖瓶內金黴菌的發酵過程,按代謝可以分為三個階段,第二天到第三天以前為“旺盛生長期”,接着到第四天止菌絲開始自溶為“開始自溶期”最後為“迅速自溶期”。培養基中,金黴素的濃度,在第二期最高。     

Zum Nachweis des Axialkomplexes bei Holothurien (Echinodermata)

On the basis of a histological investigation concerning 16 species of 4 holothurian orders, the homology of the so-called problematic canal with the axial sinus on the one side and the dorso-axial haemal strand with the axial gland on the other side is discussed. Combining these results with former investigations, the following conclusions are drawn. There is no axial complex as an organic unit represented within the class Holothuroidea. Nevertheless, this axial complex, formerly thought to be missing, is locally disintegrated into two parts, which are isolated from each other within the dorsal mesentery. One part is the stone canal—protocoelampulla—the other one the axial sinus—axial gland. Within the holothurians there is a tendency towards reduction of the protocoelampulla and the axial sinus. This recently aberrant structure of the axial complex can be deduced from an echinoid "plan".     

Corticocolpoda kaneshiroae N. G., N. Sp., a New Colpodid Ciliate (Protozoa, Ciliophora) from the Bark of Ohia Trees in Hawaii

Corticocolpoda kaneshiroae n. g., n. sp. was discovered in the bark of Ohia trees (Metrosideros polymorpha) from the Hawaiian Archipelago. Its morphology and infraciliature were studied in live cells, with the scanning electron microscope, as well as in specimens impregnated with protargol, silver nitrate, and silver carbonate. The new genus, Corticocolpoda, belongs to the family Colpodidae and is unique in having a left oral ciliary field (polykinetid) composed of 13–20 equidistantly spaced, paired rows of monokinetids. The new species, C. kaneshiroae, measures 100–300 × 60–250 μm and has a huge vestibulum used to capture large food items, mainly other ciliates. The oral ciliary fields are within the vestibulum and of equal length; the right field is a paroral membrane composed of a single row of dikinetids. Several micronuclei are attached to the ellipsoid macronucleus. The mucocysts are inconspicuous and arranged around the somatic dikinetids. The resting cyst is globular and has a 1–2 μm thin, firm, yellowish inner wall and a 20-μm-thick, fragile, hyaline outer wall. Convergent evolutionary paths and a possible polyphyly of the Colpodidae are discussed. An improved key to the genera of the family Colpodidae is provided. Twenty-three species of ciliates and one flagel***iate (Hemimastix amphikineta), which occurred together with C. kaneshiroae, are new for the fauna of Hawaii and listed in the ecology section.     

SPOTTED HYAENA WHOOPS: FREQUENT INCIDENCE OF VOCAL INSTABILITIES IN A MAMMALIAN LOUD CALL

ABSTRACT

Spotted hyaena Crocuta crocuta whoops are loud calls normally produced in a sequence termed a bout. Whoops are produced by hyaenas irrespective of age or sex to display identity and convey information about the location of the caller. The majority (91%, n=460) of whoops produced by spotted hyaenas, from two geographically separate populations in southern Africa and one population in eastern Africa, showed pronounced nonlinear phenomena, predominantly subharmonics. Whoops produced by males and females had a similarly high probability of sub- harmonics, and 91.5% of the 78 bouts examined contained calls with subharmonics. These results provide evidence that nonlinear vocal phenomena are a common feature of hyaena whoops. The presence of subharmonics in whoops may be enhanced by vocal tract resonances when the fundamental frequency and first formant in the calls are close or coincide. Vocal membranes may also play a role. The high incidence of subharmonics in whoops may enhance individual recognition by adding structural complexity to calls. As 33 of 34 individually known spotted hyaenas examined in this study produced whoops containing subharmonics, it is unlikely that the production of subharmonics is confined to calls from individuals of a particular social status, sex, size, or level of developmental asymmetry, as proposed for nonlinear phenomena in the calls of other mammalian species, although variation in structural features of subharmonics may convey information about these characteristics.