Two new species ofOdilia (Nematoda: Heligmonellidae) from Australian rodents,with comments onO. bainae Beveridge & Durette-Desset, 1992

Odilia tasmaniensis n. sp.,O. praeputialis n. sp. andO. bainae Beveridge & Durette-Desset, 1992 from the small intestine of Australian murids are described and illustrated. The two new species are distinguished from the other eight species in the genus, namelyO. mackerrasae (Mawson, 1961),O. brachybursa (Mawson, 1961),O. emanuelae (Mawson, 1961),O. melomyos (Mawson, 1961),O. polyrhabdote (Mawson, 1961),O. uromyos (Mawson, 1961),O. mawsonae (Durette-Desset, 1969) andO. bainae Beveridge & Durette-Desset, 1992.O. tasmaniensis n. sp. fromRattus lutreolus is characterised by the longitudinal cuticular ridges being continuous, the presence of 18 ridges in cross-section in the middle region of the body, the joined distal ends of the spicules forming a curved bluntly rounded tip, a short genital cone with a single ventral papilla and a pair of laterally curving dorsal raylets and the posterior end of the female tapering sharply.O. praeputialis n. sp. fromZyzomys woodwardi is characterised by continuous longitudinal cuticular ridges, the presence of 22–35 ridges in cross-section in the middle of the body, the sharply pointed joined distal tips of the spicules, a complex genital cone with a flat membraneous proconus, a ventral papilla projecting from an extension of the body wall, a pair of short straight dorsal raylets and the presence of a praepuce on the posterior end of the female.O. bainae is characterised by the longitudinal cuticular ridges being continuous, the presence of 17–22 ridges in cross-section in the middle region of the body, the joined distal ends of the spicules surrounded in an oval transparent cap, a long genital cone with a single ventral papilla and a pair of laterally curving dorsal raylets, and the absence of a praepuce on the posterior end of the female.Rattus lutreolus and the pseudomyine rodentsPseudomys higginsi andMastacomys fuscus are new host records for this species.     

Germination stimulation in wild oats (Avena fatua L.) by synthetic strigol analogs and gibberellic acid

At concentrations of 0.01–1 mM, five synthetic multiring analogs of strigol were effective germination stimulants of intact and dehulled wild oat (Avena fatua L.) seeds. The effect was concentration-dependent and equaled or exceeded that produced by equimolar gibberellic acid (GA₃). The most effective strigol analog treatments induced 55–80% germination within 7 days in intact wild oat seeds and resulted in 63–86% germination and normal seedling growth over 14 days. Intact wild oat controls germinated 14% after 14 days. The stimulation of wild oat germination by these synthetic strigol analogs demonstrates that these compounds, initially developed as germination stimulants for the seeds of the parasitic weed, witchweed (Striga asiatica L. Kuntz.), have bioregulatory activity in dormant seeds of monocots, as well as dicots. None of the compounds tested significantly affected the germination of nondormant cultivated oat seeds (Avena sativa L.). The commonly used dispersal agent, Tween 20 (0.1%), was found to inhibit germination of cultivated oats, alone and in the presence of 2% acetone.     

Factors regulating fruit and seed production in the desert annual Lesquerella gordonii

Summary This study examines the pattern of reproduction and factors that limit the maternal reproductive output in the self-incompatible annual, Lesquerella gordonii. Greenhouse experiments showed that fruits do not abscise and they mature if they contain at least one fertilized (outcrossed) ovule. Field studies showed that flowering increased to a peak and then fell off rapidly, while seed production/fruit decreased through the season. Pollen addition did not increase the number of fruit or seeds per fruit, suggesting that fruit and seed production are not pollinator limited. Addition of water increased fruit and seed production by extending the life of the plant, by increasing the number of stalks which flowered, and by increasing the number of seeds per fruit. This indicates that fruit and seed production are resource limited. Fruits are relatively inexpensive as compared to seeds as over 93% of the water in fruits is contained in the seeds. Fifty-three percent of the plants were lost to herbivory as were 64.6% of the fruits on the remaining plants, indicating that herbivory also limited fruit and seed production. It is hypothesized that high fruit set coupled with variable seed set in L. gordonii is an adaptive response to unpredictable, variable resource levels, and high herbivory risk.     

Digestion in the peritrich ciliateOphrydium versatile

Summary Digestion in the peritrich ciliateOphrydium versatile O.F.M. involves a complex sequence of intracytotic and exocytotic membrane fusion and recycling events. Food particulates are concentrated in the lower cytopharynx which forms a fusiform-shaped food vacuole. Upon release from the cytopharynx, this food vacuole begins to condense, concentrating the food particulates. Excess membrane is removed intracytotically. These released membranes pieces form discoidal vesicles which are recycled to the base of the cytopharynx, thus providing additional membrane for subsequent food vacuole formation. In the condensed food vacuole, digestion proceeds; hydrolytic enzymes are delivered to the food vacuole via rough endoplasmic reticulum and/or by the cup-shaped coated vesicles (CSCV). As these vesicles fuse with the food vacuole, the food vacuole enlarges, digestion proceeds and an electron-dense membrane coat appears along the luminal surface of the food vacuole. Prior to defecation, the food vacuole undergoes a final condensation; irregularly-shaped, electron dense, single-membrane bound vesicles are cut-off intracytotically from the old food vacuole. These vesicles undergo condensation and invagination to form the cup-shaped coated vesicles (CSCV) which fuse with younger food vacuoles.     

Measurement of the microbial biomass in intact cores of soil

The fumigation/respiration technique was used to estimate the size of the soil microbial biomass. Sieving decreased the biomass in winter but increased it in summer; we suggest that this was a consequence of the different substrates available and the different microbial populations during the year. The flush in respiration following fumigation correlated significantly with the CO₂-C produced 10 days after fumigation (X), so that in the soils studied by us the biomass (B) can be calculated from Bk=0.673X–3.53, wherek is the fraction of fumigated organisms mineralized to CO₂, thus avoiding the need to measure CO₂ production from unfumigated cores.     

Transposon mutagenesis in Proteus mirabilis.

A technique of transposon mutagenesis involving the use of Tn5 on a suicide plasmid was developed for Proteus mirabilis. Analysis of the resulting exconjugants indicated that Tn5 transposed in P. mirabilis at a frequency of ca. 4.5 x 10(-6) per recipient cell. The resulting mutants were stable and retained the transposon-encoded antibiotic resistance when incubated for several generations under nonselective conditions. The frequency of auxotrophic mutants in the population, as well as DNA-DNA hybridizaiton to transposon sequences, confirmed that the insertion of the transposon was random and the Proteus chromosome did not contain significant insertional hot spots of transposition. Approximately 35% of the mutants analyzed possessed plasmid-acquired ampicillin resistance, although no extrachromosomal plasmid DNA was found. In these mutants, insertion of the Tn5 element and a part or all of the plasmid had occurred. Application of this technique to the study of swarmer cell differentiation in P. mirabilis is discussed.     

Neorhabditostomum yeni n. g., n. sp. (Nematoda,Strongyloidea) from Muntiacus muntjak in Sabah,Malaysia

Neorhabditostomum yeni n. g., sp. is described from the intestine of the barking deer, Muntiacus muntjak, from Simatuoh, Sapulot, Sabah, Malaysia. It is distinguished from the nearest genera, namely Bourgelatoides and Rhabditostomum, in the subfamily Oesophagostominae by the presence of an elongate, unsegmented, oesophageal funnel, a single leaf crown, the separation of the oral collar by a wide groove from the cephalic vesicle, the position of the cervical papillae, the absence of filaments on the spicules and the absence of an evagination of the vulva. The significance of the arrangement of the cephalic papillae within the Stronglyloidea is discussed. ac]19860428