O. J.-P. Ball

Do organic and anthropogenic acidity have similar effects on aquatic fauna

In Westland, New Zealand, there are many brownwater steams with naturally low pH (often around 4) brought about by high concentrations of organic acids. Up to 90% of dissolved aluminium in these humic streams is bound to organic matter and is therefore non-toxic. This condition enabled us to investigate the effects of long-term, natural acidity on aquatic biota without the compounding effects of high concentrations of toxic aluminium that are found in many anthropogenically-acidified, clearwater streams of the Northern Hemisphere. Most fish are absent from Northern Hemisphere clearwater habitats with pH < 5. However, in Westland 9 out of 14 native fish species were found in brown waters with pH below 5, and 7 species were taken from waters with pH < 4.5. Furthermore, 34 of the 37 most widespread aquatic insect taxa were recorded in Westland streams with pH < 5, and 24 were taken from sites with pH < 4.5. Clearly, many members of the freshwater fauna in Westland are well-adapted for life in waters of low pH. Physiological adaptations enabling this tolerance may be the same as those that evolved in response to the physicochemical variability associated with the unpredictable flow regimes of Westland streams. Tolerances of low pH have been documented in aquatic fauna from some naturally acidic, humic waters of the Northern Hemisphere, although degree of tolerance can vary within as well as between species. Colonisation of recently-acidified waters by acid-tolerant strains may cause more subtle changes in community structure than can be detected by conventional ecological techniques.

Fungal and host genotype effects on compatibility and vascular colonization by Epichloë festucae

Parental and progeny isolates of the endophytic fungus Epichloe festucae were tested for compatibility with five grass species: Lolium perenne, Festuca arundinacea, F. longifolia, F. pratensis , and F. rubra subsp. rubra . One parental and some progeny isolates adversely affected the growth of plants, causing increased mortality of inoculated seedlings, stunted growth and chlorotic leaf symptoms. Growth of hyphae from surface-sterilized leaf sheaths and blades was more vigorous and concentrated from stunted than from symptomless plants. In addition, the growth of isolates was influenced by the host species, whereby estimates of hyphal concentration were consistently highest in meadow fescue associations and lowest in tall fescue associations. Light microscopic and transmission electron microscopic examination of stunted plants indicated no changes in host cells. Intercellular hyphae were observed within vascular bundles of leaf blades and sheaths of many of the endophyte–grass associations. The frequency of infected vascular bundles and the concentration of hyphae within them was highest in plants infected with the stunting parental isolate and lowest in plants infected with the symptomless parental isolate. Hyphae within vascular bundles-were typically in close contact with sieve-tube elements and appeared to be functioning as powerful sinks, diverting assimilates and restricting growth.

Distribution and Accumulation of the Alkaloid Peramine in Neotyphodium lolii-Infected Perennial Ryegrass

Through the production of alkaloids and mycotoxins, the endophytic fungus of perennial ryegrass, Neotyphodium lolii, confers resistance to the host grass against several insect pasture pests and causes health problems in livestock. The effects of plant component, plant reproductive development, and plant management (trimming) on the concentration and accumulation of peramine, the alkaloid thought to be most important for conferring resistance against Argentine stem weevil, were investigated. Clones of eight different naturally occurring perennial ryegrass-N. lolii associations were used in the experiment, which was conducted during spring–summer, which corresponded with the height of plant reproductive activity. Clones were either trimmed regularly to maintain them in a vegetative state (V clones) or not trimmed, allowing them to become fully reproductive (R clones). V and R clones of each grass/endophyte association were destructively harvested at times that corresponded roughly with the start, middle, and end of the plant reproductive phase. Harvested material was dissected into a number of plant components that were analyzed for peramine concentration by HPLC. All clippings from the V clones were also analyzed. Peramine concentrations were usually similar in leaf sheaths and leaf blades, but they decreased as leaf age increased. The seed from R clones and younger sheaths and blades of leaves from vegetative tillers contained the highest concentrations, while the root, crown, and dead leaf tissue contained the lowest. During the inflorescence phase, tissues from reproductive tillers generally contained lower concentrations than corresponding tissues from vegetative tillers. Also at this time, mean peramine concentrations were higher in V clones than in R clones. By the end of the plant reproductive phase, at the mature seed stage, mean peramine concentrations in R and V clones were similar. The seed component, which contained approximately 75% of the total peramine present in the plant (at a mean concentration of 63.7 μg/g), probably accounted for much of the recovery in the R clones.

Distribution and Accumulation of the Mycotoxin Lolitrem B in Neotyphodium lolii- Infected Perennial Ryegrass

The symbiotic relationship between perennial ryegrass and its endophytic fungus, Neotyphodium lolii, is of considerable agronomic significance in New Zealand. Livestock ingesting N. lolii-infected perennial ryegrass may succumb to a neuromuscular condition, ryegrass staggers, the probable cause of which has been identified as the endophyte-produced indole–diterpenoid mycotoxin lolitrem B. The effects of plant component, plant reproductive development, and plant management (clipping) on the concentration and accumulation of lolitrem B were investigated. Eight different naturally occurring perennial ryegrass–N. lolii associations were cloned. They were either trimmed regularly to maintain their vegetative state (V clones) or not trimmed at all to enable full plant reproductive development (R clones). At times that corresponded approximately with the start, middle, and end of the plant reproductive phase, V and R clones of each grass–endophyte association were destructively harvested. After dissection into a number of plant components, harvested material was analyzed for lolitrem B content by HPLC. Analyses were also performed on all clippings taken from the V clones. Highest lolitrem B concentrations in vegetative parts were found in older leaf sheaths and dead leaves. Towards the end of the plant reprodutive phase, dead leaves also contained a large proportion of the total lolitrem B content of the V clones. The highest concentration of lolitrem B was found in the seed, which accounted for nearly 60% of the total quantity in R clones. Leaf blades, young leaf sheaths, roots, and crowns generally contained low to moderate concentrations. In late spring, mean concentrations in R and V clones were similar. By the time mature seed was present (mid-summer), mean concentrations in R clones were three times higher than in V clones. This difference was attributed largely to the contribution by the seed in the R clones. The implications of these findings in relation to ryegrass staggers in livestock are discussed.

Ergovaline Distribution in Perennial Ryegrass Naturally Infected with Endophyte

Recently there has been renewed interest in the possible impact on animal health and performance and insect resistance of ergovaline in perennial ryegrass (Lolium perenne) naturally infected with Neotyphodium lolii. In an earlier limited study of vegetative plants, ergovaline was found to be concentrated in basal tissues (Davies et al., 1993). We have now examined the ergovaline content of tissue fractions of vernalized endophyte-infected ryegrass plants in spring, and report our findings to draw attention to the effect of the reproductive status of the ryegrass plant on the exposure of grazing stock to ergovaline in the forage on offer.

Endophyte Isolate and Host Grass Effects on Chaetocnema pulicaria (Coleoptera: Chrysomelidae) Feeding

ABSTRACT Endophytic fungi belonging to the genus Neotyphodium, confer resistance to infected host grasses against insect pests. The effect of host species, and endophtye species and strain, on feeding and survival of the corn flea beetle, Chaetocnema pulicaria Melsheimer (Coleoptera: Chrysomelidae) was investigated. The grass—endophyte associations included natural and artificially derived associations producing varying arrays of common endophyte-related alkaloids or alkaloid groups, peramine, lolitrem B, ergovaline, and the lolines. Preference and nonpreference tests showed that C. pulicaria feeding and survival were reduced by infection of tall fescue with the wild-type strain of N. coenophialum, the likely mechanism being antixenosis rather than antibiosis. In the preference tests, endophyte and host species effects were observed. Of the 10 different Neotyphodium strains tested in artificially derived tall fescue associations, eight strongly deterred feeding by C. pulicaria, whereas the remaining two strains had little or no effect on feeding. Infection of tall fescue with another fungal symbiont, p-endophyte, had no effect. Perennial ryegrass, Lolium perenne L., infected with six strains of endophyte, was moderately resistant to C. pulicaria compared with endophyte-free grass, but four additional strains were relatively inactive. Six Neotyphodium—mendow fescue, Festuca pratensis Huds., associations, including the wild-type N. uncinatum—mendow fescue combination, were resistant, whereas three associations were not effective. Loline alkaloids seemed to play a role in antixenosis to C. pulicaria. Effects not attributable to the lolines or any other of the alkaloids examined also were observed. This phenomenon also has been reported in tests with other insects, and indicates the presence of additional insect-active factors.

Corn Flea Beetle (Chaetocnema Pulicaria) Responses to Natural Endophytes of Tall Fescue, Meadow Fescue, and Perennial Ryegrass

Adult corn flea beetle (Chaetocnema pulicaria) were less numerous on plots containing tall fescue (Festuca arundinacea) infected with the endophytic fungus Neotyphodium coenophialum than on endophyte-free tall fescue plots (Kirfman et al. 1986). The experiments described in this paper were aimed to ascertain whether the endophyte-mediated resistance to corn flea beetle was a consequence of antibiosis or feeding deterrence, and whether grass-endophyte associations other than tall fescue-N. coenophialum were also resistant.

Distribution, nymphal habitat, genetic structure and conservation of the New Zealand mayfly Isothraulus abditus (Insecta: Ephemeroptera) and a description of its subimago

ABSTRACT Distribution, nymphal habitat and genetic structure of the New Zealand mayfly Isothraulus abditus were investigated to improve our understanding of its ecology and conservation status. A description of the undescribed subimaginal stage is also provided. Isothraulus abditus has now been recorded from 55 North Island streams, 47 being new to published literature. Its distribution currently extends from Mangonui in Northland to Taumatatahi near Whanganui. Nymphs live in forested stream pools and backwaters containing organic detritus. Genetic structure of six populations was assessed using the mitochondrial cytochrome c oxidase subunit I (COI) gene. Thirty-six haplotypes were identified from 123 individuals, and a maximum uncorrected genetic distance of 1.8% indicated that specimens belong to a single species. However, those within Northland showed some genetic differentiation. Restricted habitat, sparse distribution and some genetic differentiation of I. abditus suggest its conservation status should be classified as ‘At Risk’. LSID: urn:lsid:zoobank.org:pub:75C386BC-C0A5-4627-AE4B-8C5D749D53BA

IMMUNOLOGICAL DETECTION OF THE NEOTYPHODIUM-LIKE ENDOPHYTE OF ANNUAL RYEGRASS

Annual ryegrass (Lolium multiflorum) is sometimes infected with a Neotyphodium-like endophytic fungus (Latch et al. 1988). The significance of this little-studied endophyte is not thought to be great as it has not been associated with any livestock disorders, or with resistance to invertebrates, with the exception that Argentine stem weevil (Listronotus bonariensis) adults were deterred from feeding on young seedlings ([Latch et al. 1988). The Neotyphodium-like endophyte has also not been fully described taxonomically. The experiments described in this paper aimed to determine whether the Neotyphodium-like endophyte could be detected in annual ryegrass herbage (vegetative and reproductive) using a polyclonal antiserum prepared against the tall fescue (Festuca arundinacea) endophyte, N. coenophialum. This would also provide information about the serological relationship between N. coenophialum and the Neotyphodium-like endophyte.

Feeding Preferences of Larval Fall Armyworm on Neotyphodium-Infected Grasses

A number of insects are deterred from feeding on grasses by alkaloids produced in planta by Neotyphodium endophytes (Popay and Rowan, 1994). Also, alkaloids associated with endophyte-infected grasses are toxic to some herbivorous insects. The objectives of this study were to determine the ability of fall armyworm to discriminate between tall fescue (TF), meadow fescue (MF) and perennial ryegrass (PRG) infected with various Neotyphodium endophytes and their endophyte-free counterparts.