In Vitro Cultivation of the Vascular Phase of Sarcocystis singaporensis

To establish an in vitro culture system for the precystic phase of Sarcocystis singaporensis, we initially tested various excysting fluids for sporocysts. An excysting fluid containing 2.5% bovine taurocholate and 10% bile of the specific intermediate host, Rattus norvegicus, in RPMI medium was the most suitable resulting in excystation of 80% of the sporozoites. Subsequently, we identified brain endothelial cells and pneumonocytes of the rat to promote growth of sporozoites to schizonts. Hepatoma, fibroblastic, or myoblastic cells were not suitable for the parasite's development. First-generation schizonts were seen at days 3-10 postinoculation (PI); a distinct second peak of schizogonic development only occurred in endothelial cells at days 14-18 PI. First-generation schizonts were 26.0 (± 3.8) μm in diameter and contained 32-50 merozoites, second-generation schizonts measured 34.4 (± 10.6) μm and contained 54-72 merozoites. Merozoite yield at large-scale culture conditions (75 cm² flasks) using pneumonocytes as host cells was relatively low. Ultrastructurally, sporozoites and merozoites were quite similar to corresponding stages of other Sarcocystis species. With regard to host cell specificity and developmental kinetics, in vitro cultivation showed close similarities to the situation in vivo.     

To mark the host or the patch: Decisions of a parasitoid searching for concealed host larvae

We found evidence for patch marking in the parasitic wasp Halticoptera laevigata (Hymenoptera: Pteromalidae) foraging for concealed hosts. Wasps attack larvae of the fruit fly Myoleja lucida (Diptera: Tephritidae) in fruits of honeysuckle. A special feature of this host-parasitoid system is the limited food supply of a patch (i.e. a fruit of honeysuckle), which allows the successful development of only a single host fly larva. Females of the parasitoid H. laevigata were found to mark the host patch with a pheromone and to abandon the patch following oviposition into a single host larva. Field data revealed that eggs of the parasitoid were spread out evenly among infested patches, with several larvae of the host fly left unparasitized in those patches that contained more than one host. Since many parasitic insects mark the parasitized host after oviposition, we assumed host marking to be the ancestral character state and studied the patch-marking behaviour of H. laevigata as a derived character state as an alternative foraging strategy. We used stochastic dynamic modelling to investigate under what conditions mutant (patch) markers would be able to invade a population of normal (larval) markers. The models suggested that, under a variety of conditions, wasps marking the patch obtained higher fitness than wasps only marking the larva. Consequently, the results from our model predict the evolution of the patch-marking behaviour found in the empirical investigation. Finally, we discuss alternative pathways to the evolution of patch marking and point out under what circumstances the evolution of a patch-marking behaviour can generally be expected.     

Actuarial senescence in laboratory and field populations of Lepidoptera

1. Recent observations of actuarial senescence – an increase in mortality rate with age – have challenged the assertion that the brevity of adult insect life spans precludes ageing. 2. Here the rate of senescence in 22 species of Lepidoptera was quantified by fitting demographic models to adult survivorship data drawn from a range of field and laboratory studies. 3. Senescence was evident in all 22 species investigated, with a model of age‐related mortality consistently fitting the survivorship curves significantly better than an alternative model which assumes constant mortality. 4. The rates of senescence varied significantly among species. The rates of senescence also differed significantly between sexes for all species tested, but not in a consistent way.     

PRIMARY PEPTIDE SEQUENCES FROM SQUID MUSCLE AND OPTIC LOBE MYOSIN IIs: A STRATEGY TO IDENTIFY AN ORGANELLE MYOSIN

The squid giant axon provides an excellent model system for the study of actin-based organelle transport likely to be mediated by myosins, but the identification of these motors has proven to be difficult. Here the authors purified and obtained primary peptide sequence of squid muscle myosin as a first step in a strategy designed to identify myosins in the squid nervous system. Limited digestion yielded fourteen peptides derived from the muscle myosin which possess high amino acid sequence identities to myosin II from scallop (60–95%) and chick pectoralis muscle (31–83%). Antibodies generated to this purified muscle myosin were used to isolate a potential myosin from squid optic lobe which yielded 11 peptide fragments. Sequences from six of these fragments identified this protein as a myosin II. The other five sequences matched myosin II (50–60%, identities), and some also matched unconventional myosins (33–50%). A single band that has a molecular weight similar to the myosin purified from optic lobe copurifies with axoplasmic organelles, and, like the optic lobe myosin, this band is also recognized by the antibodies raised against squid muscle myosin II. Hence, this strategy provides an approach to the identification of a myosin associated with motile axoplasmic organelles.     

The development of an Early Ordovician hard ground community in response to rapid sea-floor calcite precipitation

The Kanosh Shale (Upper Arenig, Lower Ordovician) of west-central Utah. USA. contains abundant carbonate hardgrounds and one of the earliest diverse hardground communities. The hardgrounds were formed through a combination of processes including the development of early digenetic nodules in clay sediments which were exhumed and concentrated as lags by storms. These cobble deposits. together with plentiful biogenic metrical. were cemented by inorganically precipitated calcite on the sea floor. forming intraformational conglomerate hardgrounds. Echinoderms may have -played a critical role in the development of hardground faunas since their disarticulated calcite ossicles were rapidly cemented by syntaxial overgrowths. forming additional cobbles and hardgrounds. The echinoderms thus may have taphonomically facilitated the development of some of the hard substrates they required. A significant portion of the hardground cements may have been derived from the early dissolution of aragonitic mollusk shells. Kanosh hardground species include the earliest bryozoans recorded on hardgrounds and large numbers of stemmed echinoderms. primarily rhipidocystid cocrinoids. Bryozoans and echinoderms covered nearly equal areas of the hardground surfaces. and there was a distinct polarization between species which preferred the upper. exposed portions of the hardgrounds and others which were most common on undercut. overhang surfaces. The Kanosh Shale hardground fossils combine elements of Late Cambrian assemblages and Middle Ordovician faunas, thus confirming predicted trends in hardground community evolution. especially the replacement of cocrinoids by bryozoans and. to a lesser extent, by other stemmed echinoderms, especially crinoids. The Kanosh community marks the transition from the Cambrian Fauna to The Paleozoic Fauna in The hardground ecosystem. *Carbonate hardgrounds, aragonite dissolution, calcite cement, Echinodermara, Trepostomata, Nicholsonclla. Dianulites. Porifpra. taphonomic facilitation, Utah. Pogonip Group, Kanosh Shale. Ordovician.     

An Electron Microscope-Cytochemical Method for Differentiating Membranes of Host Red Cells and Malaria Parasites*

Limiting membranes of malaria parasites and host red cells stain differently when exposed to positively charged iron colloid. Negatively charged red cell membranes avidly bind colloid, whereas parasite membranes do not. This selectivity in colloidal iron uptake by the 2 types of membranes can be utilized as an aid in discerning the amounts of contaminating host cell membranes in “free” malaria parasite preparations and in related cell-free membrane extracts.     

Purification and properties of ginger chlorotic fleck virus

A previously undescribed isometric virus, named ginger chlorotic fleck virus (GCFV), was detected in ginger (Zingiber officinale) imported into Australia from a number of countries. The geographical distribution of the virus is uncertain, but is thought to include India, Malaysia and Mauritius. The virus apparently does not occur in Australian commercial ginger plantings. The virus has isometric particles c. 30 nm in diameter, with a sedimentation coefficient of 111 S, and was readily purified from infected ginger with yields of 50–90 mg/kg leaf tissue. Purified preparations contained a major species of single-stranded RNA of mol. wt 1.50 × 10⁶ and a major coat protein species of mol. wt 29.0 × 10³. At pH 7, the particles formed a single zone in both caesium chloride and caesium sulphate gradients, with buoyant densities of 1.355 g cm^-3 (fixed virus) and 1. 297 g cm^-3 (unfixed virus), respectively. The virus particles migrated as two electrophoretic components and were labile when treated with 10 mM EDTA, 1 M NaCI, 10 mM tris pH 8.25 or when negatively stained with potassium phosphotungstate. GCFV was mechanically transmitted only to ginger, and was not transmitted by the aphids Myzus persicae. Pentalonia nigronervosa, Rhopalosiphum maidis or R. padi. Possible affinities of GCFV with the sobemo-virus group are discussed. The present cryptogram of GCFV is ^R/_l: ^1.5/₂₀: ^S/_S: ^S/_*.     

Peroxidases in Relation to Removal of Dormancy and Germination of Apple Embryos

The changes in germination, peroxidase activity and isoperoxidase spectrum have been studied in apple embryos at 5°C (stratification) and at 20°C in the presence or absence of seed coats. The embryo dormancy is progressively released at 5°C, but not at 20°C. The peroxidase activity in embryos covered with seed coats is very low at 5°C as well as at 20°C which corresponds to a restricted number of isoenzymes. In isolated embryos the peroxidase activity increases significantly. This is due to an increase in both the number and the activity of the isoperoxidases and it is more pronounced at 20°C than at 5°C. The obtained results suggest that the soluble peroxidases are not involved in the process of the release of embryo dormancy. The variations observed are attributed to the growth process following germination, which can occur even at low temperature.