The effect of ammonia treatment on the solubilization of straw and the growth of cellulolytic rumen bacteria

Pre-treatment of straw with anhydrous ammonia increased its susceptibility to solubilization by the predominant cellulolytic bacteria from the rumen, Bacteroides succinogenes, Ruminococcus albus and R. flavefaciens. Ammonia treatment also increased the production of microbial protein and fermentation products by all three species. Scanning electron microscope observations of straw during digestion suggested that the attack of straw by these bacteria was accompanied by the formation of substantial numbers of adherent microcolonies.     

Interactions between ants and seeds of two myrmecochorous plant species in recently burnt and long‐unburnt forest sites

Myrmecochory (seed dispersal by ants) is a common seed dispersal strategy of plants in fire‐prone sclerophyll vegetation of Australia, yet there is little understanding of how fire history may influence this seed dispersal mutualism. We investigated the initial fate of seeds of two myrmecochorous plant species, the small‐seeded Pultenaea daphnoides J.C. Wendl. and the large‐seeded Acacia pycnantha Benth., in replicated burnt (3.25 years since fire) and unburnt (53 years since fire) forest plots in the Mount Lofty Ranges, South Australia. Specifically we measured (i) seed removal rates; (ii) the frequency of three ant–seed interactions (seed removal, elaiosome robbery and seed ignoring); (iii) the relative contribution of different ant species to ant–seed interactions; and (iv) the abundance of common interacting ant species. Rates of seed removal from depots and the proportion of seeds removed were higher in recently burnt vegetation and the magnitude of these effects was greater for the smaller‐seeded P. daphnoides. The overall proportion of elaiosomes robbed was higher in unburnt vegetation; however, the decrease in elaiosome robbery in burnt vegetation was greater for P. daphnoides than for A. pycnantha. Ants ignored seeds more frequently in burnt vegetation and at similar rates for both seed species. In total, 20 ant species were observed interacting with seeds; however, three common ant species accounted for 66.3% of ant–seed interactions. Monomorium sydneyense almost exclusively robbed elaiosomes, Rhytidoponera metallica typically removed seeds and Anonychomyrma nr. nitidiceps showed a mix of the three behaviours towards seeds. Differences in the proportions of seeds removed, elaiosomes robbed and seeds ignored appeared to be largely driven by an increase in abundance of A. nr. nitidiceps and a decrease in abundance of M. sydneyense in burnt vegetation. Understanding how these fire‐driven changes in the initial fate of myrmecochorous seeds affect plant fitness requires further investigation.     

Metabolic rate in diapause and nondiapause brown locust eggs correlated with embryonic development

Insects use dormancy to survive adverse conditions. Brown locust Locustana pardalina (Walk.) eggs offer a convenient model to study dormancy (diapause and quiescence), which contributes to their survival under arid conditions. The metabolic rates of developing nondiapause, diapause and quiescent eggs are compared in the present study using closed‐system respirometry. The embryo becomes committed to continue development and hatch or to enter diapause 6 days after the eggs are placed on moist soil. The metabolic rate of nondiapause eggs increases exponentially until hatching, whereas that of diapause eggs is low and stable. The metabolic rate of diapause laboratory eggs (1.9 ± 0.6 µL CO₂ mg^?1 h^?1) is significantly higher than that of field eggs (0.5 ± 0.3 µL CO₂ mg^?1 h^?1), although the ranges of metabolic rate overlap and the embryos are all in late anatrepsis. The metabolic rate of quiescent eggs is similar to that of diapause eggs but decreases with time. Low metabolic rates during arrested development allow eggs to persist over long periods before hatching.     

A comparison of daphnid gut particles with the sestonic particles present in two Thames Valley reservoirs throughout 1970 and 1971

The numerically most abundant component of the seston in two of the Thames Valley storage reservoirs of the Metropolitan Water Board consisted of flocculent organic material which, together with the hyaline, transparent and blackened particles, formed the non-living sestonic fraction. The abundance of bacterio-plankton was estimated from plate counts which are known to provide an under-estimate of the bacteria present. The phytoplankton consisted of the larger flagellates present throughout the year together with a seasonal succession of algae in much greater numbers, namely the smaller flagellates, diatoms, colonial greens, Tribonema and Anabaena. A seasonal analysis of the gut contents of Daphnia magna, D. pulex and D. hyalina (occurring as important grazers in the reservoirs), revealed the presence of organic particles throughout the year plus cells or filaments of the prevailing alga at different seasons. During the summer, there were periods when the guts contained recognizable animal and plant debris. Flagellate and bacterial remains were never seen intact in the guts although these were abundant in the seston during early spring. The filamentous Tribonema was ingested when large crops of it were present. The most frequent size of ingested particle was between 1–2 μm and up to 60% of the animals examined contained particles which were neither longer nor wider than 20μm. Most of these animals ranged between 0·5–1·9 mm in length. A limiting factor for ingestion was thought to be width rather than length of particle and most very large particles found in the gut were long narrow and pliant filaments like Tribonema, or gelatinous colonial green algae, or flexible, foldable crustacean filtering limbs. There appeared to be no difference in the nature or size of particle ingested by the three different species of daphnids and any difference in maximal particle width observed was more likely to be related to body size than to species of consumer.     

Motion Analysis in the Assessment of Surgical Skill

Abstract

Manual skill is now widely recognised as an important aspect of training in surgery. However, measurement of the skill of a surgeon has in the past been rather subjective in nature, relying on the judgement of experts in the analysis of videotapes. Objective measurements can be made by analysing the velocities of a surgeon's hands during a procedure. In particular, we have found that the number of movements made during a typical procedure will decrease as the surgeon's skill increases. Velocity traces display purposeful movements corrupted by uncorrelated noise from sources such as hand tremor and measurement artefacts. However, we have found that it is possible to filter the noise effectively. Furthermore, we have shown that the skill measurement obtained by counting movements is highly robust to over or under filtering.     

Fire‐related cues and germination from the soil seed bank of senescent remnants of mallee vegetation on Eastern Kangaroo Island

Plant communities dominated by narrow‐leaved mallee (Eucalyptus cneorifolia) are almost entirely confined to north‐eastern Kangaroo Island, South Australia, an area which has been extensively cleared for agriculture. Consequently, surviving examples consist mostly of small remnants which are thought to be senescent due to the exclusion of fire. This senescence is associated with the loss of many native understory species. Prescribed burns have been suggested as a management tool to stimulate the restoration of native plants from the soil seed bank; however, no seed bank studies have previously been conducted on Kangaroo Island and the seed bank literature usually focuses on particular species rather than on plant communities. We conducted an experiment to investigate the effects of the fire‐related cues heat and smoke on the germination of plants from the seed bank in soil sampled from 10 long‐ungrazed narrow‐leaved mallee sites on Kangaroo Island. Eighty trays of soil were monitored in a controlled glasshouse for five months after being subjected to heat and/or smoke treatments. The overall number of native, but not exotic, plant species germinating from the soil seed bank was significantly increased by all three fire‐related treatments (heat, smoke and heat plus smoke) compared with the control (no fire‐related treatment). Different plant life forms exhibited varying responses to heat and smoke treatments. The results of this study illustrate that the application of fire‐related treatments to soil seed banks in controlled glasshouse conditions can stimulate the recruitment of native species, including several species of conservation concern. These findings also indicate the potential of using these treatments for the ex situ germination of fire dependent species for revegetation purposes and indicate aspects of prescribed burns that may be important for restoring different components of native vegetation.