Spatial patterns and sampling plans for cereal aphids [Hom.: Aphididae] killed by entomophthoralean fungi and hymenopterous parasitoids in spring wheat

Cereal aphids infesting spring wheat in southwestern Idaho were surveyed during 1988 and 1989 for the presence of entomophthoralean fungi and hymenopterous parasitoids. Cereal aphids killed by the fungi (cadavers) and parasitoids (mummies) includedDiuraphis noxia (Mordvilko),Metopolophium dirhodum (Walker),Sitobion avenae (F.), andSchizaphis graminum (Rondani). Taylor's power law was used to describe the relationships between mean densities of cadavers or mummies (number per tiller) and associated variances. Except forS. graminum mummies, which were at low levels throughout the growing seasons and tended to be randomly distributed, Taylor's slopes exceeded 1.0 for all the aphid cadavers and mummies, indicating varying degrees of clumping in spatial pattern. The spatial patterns ofD. noxia andM. dirhodum cadavers were similar, simply reflecting those of their own populations, but more aggregated than were their respective mummies resulting from parasitoid attack. The intercepts and slopes from the power law analysis were used to generate functional relationships between the proportion of wheat tillers bearing cadavers or mummies of each aphid species and the mean density, and develop optimal numerical (direct counting) and binomial (presence or absence) sample size curves for both cadavers and mummies of each aphid species.      

Chironomid pupal exuviae and larvae of two storage reservoirs in The Netherlands

For three years chironomid larvae were collected bimonthly with a grab sampler in two deep storage reservoirs in The Netherlands. Chironomid pupal exuviae were collected monthly, from April to November, with a handnet. Net samples yielded more taxa than grab samples. The taxa found in net samples originated from more habitats, than taxa found in grab samples. The relative contribution of Orthocladiinae was much larger in net samples. Based on the results obtained in the two reservoirs, some advantages and disadvantages of both sampling methods are discussed.     

The spring development of phytoplankton in Lake Erken: species composition,biomass, primary production and nutrient conditions — a review

Relative abundance and within-lake distributions of three fishes, northern redbelly dace (Phoxinus eos), finescale dace (Phoxinus neogaeus), and central mudminnow (Umbra limi), were examined using minnow traps in Tuesday Lake, a small bog lake in the Upper Peninsula, Michigan. For these species, catches in minnow traps placed at the perimeter of the lake were 21 to 52 times higher than catches in midlake traps. Variance: mean ratios of perimeter trap catches indicated that both dace species were highly aggregated while the distribution of mudminnows was less aggregated or random. Over an 11 day period during which all fish caught were removed from the lake, catch per unit effort (CPUE) of both dace species declined in response to fish removal. In contrast, CPUE for mudminnows was low initially, increased to an asymptote and then declined only in the last 5 days of the fish removal. The patterns of CPUE for mudminnows indicated that mudminnow trapability and/or activity was reduced in the presence of high densities of dace. The low abundance of dace in traps with many mudminnows suggested mudminnows avoided traps already containing dace. Throughout the removal period, CPUE provided an accurate index of dace abundance, whereas this was true for mudmnnows only after dace populations had been reduced drastically. Therefore, in any use of minnow traps to estimate populations, both spatial distributions and relative species abundance of small fishes must be taken into account.     

Trypanosoma musculi: Passive hemagglutination technique to measure antibody in mice

A passive hemagglutination assay was developed to measure Trypanosoma musculi-specific antibody in mice. Indicator-erythrocyte donor mice received 550 rad ⁶⁰Co 24 hr before intraperitoneal injection of 3 × 10⁴T. musculi. T. musculi antigen-coated erythrocytes were obtained from these mice on Day 9 postinfection. T. musculi antigen-coated erythrocytes obtained in this manner were used as indicator erythrocytes in a passive hemagglutination procedure. Serum from hyperimmunized mice (three consecutive infections at 21-day intervals) gave titers as high as 1:1024. Titers of 1:256 and 1:512 were obtained from singly infected mice on Days 18 and 28 postinfection, respectively. In marked contrast, nude mice infected with T. musculi did not produce a detectable agglutinating antibody response. Erythrocytes obtained from either irradiated (550 rad ⁶⁰Co) uninfected mice, nonirradiated infected mice, or normal mice did not agglutinate when combined with any of the sera tested. These data suggest the usefulness of this passive hemagglutination assay for the measurement of antibody to T. musculi in the serum of infected mice.     

Immunity acquired by sheep from an experimental infection with haemonchus contortus

Adams D.B. and Beh K.J. 1981. Immunity acquired by sheep from an experimental infection with Haemonchus contortus. International Journal for Parasitology11: 381–386. A primary infection of sheep with a single dose of Haemonchus contortus larvae was traced by faecal egg counts until it had substantially declined after 55 weeks. These primed sheep were then given a sequence of two reinfections with the parasite. Comparison of faecal egg counts in primed sheep and in two separate groups of previously worm-free sheep showed that primary infection conferred significant immunity. This, however, was not sufficiently protective to prevent the development of further anaemia and faecal egg counts indicative of clinical haemonchosis. It is suggested that an adaptation in the host-parasite relationship which promotes the longevity of primary infection with H. contortus may also moderate the induction of acquired immunity.The titre of haemagglutinating antibody specific for H. contortus rose in serum during the course of primary infection, but the two reinfections did not stimulate a rise in titre. Titres of haemagglutinating antibody before reinfection did not correlate with subsequent faecal egg counts.     

Ecological studies of spores of aquatic hyphomycetes in the cringle brook,lincs

The aquatic Hyphomycete spora of the Cringle Brook, Lincs, was examined by foam sampling and by the use of cellophane impaction traps between August, 1968 and January, 1970.The species most frequently found (Tetracladium marchalianum, Alatospora acuminata and Flagellospora curvula) were generally in agreement with those found by other workers in temperate areas. Impaction trap samples generally contained fewer species than foam samples but filiform spore types such as Flagellospora were more frequently found on traps than in foam suggesting that impaction is more selective towards the filiform spore type than is foam. Many species increased in frequency in autumn accompanying and following leaf fall, and the winter spora was dominated by Alatospora acuminata, Clavariopsis aquatica, Clavatospora stellata, Flagellospora curvula and Lemonniera aquatica. During the summer the spora was dominated by Tetracladium marchalianum.The role of foam and impaction in the balance of aquatic spore populations is discussed in relation to techniques available for their study.     

Relieving efforts in palm‐tree tissue sampling for population genetics analyses

1. The young leaves are the main source of nucleic acids for population genetic studies in palm‐trees; however, the access to this tissue may be limited by specific features of each species. Using root tissues as an alternative source of nucleic acids could facilitate the sampling in large populations.
2. This study tests root tissue viability as an alternative nucleic acid source (root versus. leaf) and explores different protocols (tissue storage and DNA extraction methods) to obtain high‐quality DNA samples.
3. The results showed no significant differences in DNA concentration (603.7 vs. 599.1 ng/μl) and quality ratios (A260/280:2.1 vs. 1.9, and A260/230:2.1 vs. 2.0) for the comparisons of tissue source (leaf vs. root) and DNA extraction method (manual vs. kit). For tissue storage method, DNA concentration was significantly higher for root tissues stored in 70% and 90% alcohol solutions (692.8 and 822.6 ng/μl, respectively) versus those obtained from leaf tissue (603.7 ng/μl); however, for the quality parameters, no differences were found.
4. Results showed the effective potential of using root tissue as an alternative source for nucleic acids, which could facilitate population sampling of palm‐tree species for future studies, and this methodological alternative could be applied to other plant systems with similar sampling challenges.

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