Evidence for parasitoid‐induced premature mortality in the Argentine stem weevil

The Argentine stem weevil Listronotus bonariensis Kuschel (Coleoptera: Curculionidae) is an exotic pest of New Zealand ryegrass and the adult‐stage is parasitized by the introduced solitary endoparasitoid Microctonus hyperodae Loan (Hymenoptera: Braconidae: Euphorinae). This biological control agent is effective, although, under both laboratory and field conditions, an unexplained source of premature mortality in the weevils is observed after exposure to M. hyperodae. This premature mortality may be affected to varying degrees by the length of time of parasitoid exposure, the physiological conditions of the host, and the host to parasitoid ratios, although it occurs naturally without any physical interruption to the parasitoid ovipositional process. In the present study, the premature mortality reported in earlier studies is confirmed and it is conjectured to be the result of injection of parasitoid venom without an egg. Moreover, the lack of premature mortality resulting from longer exposure periods indicates that there might be a curative effect resulting from subsequent oviposition; the egg reverses the toxic effect induced by the injection of venom only. As discussed, this phenomenon may not be restricted to the L. bonariensis/M. hyperodae system and, accordingly, there are evolutionary, biosecurity and general pest management questions to be considered.     

A Comparison of Field and Molecular Techniques for Sexing Beavers

Abstract: The traditional method of sex identification in beavers (Castor canadensis) by external palpation can be inaccurate. We tested 2 genetic methods for determining sex in beavers, the zinc-finger DNA marker and the Y chromosome-specific sex determining region (SRY) marker. The SRY marker identified sex correctly in 57 of 67 (85%) beavers, whereas the zinc-finger technique was successful less often in only 48 of 67 (72%) animals. Sex was correctly assigned by palpation for 21 of 27 beavers (78%). Beaver studies in which accurate sex identification is critical may benefit by verifying the sex of individuals using one or both of these molecular markers.     

Tolerance of Anoxia and Ethanol Toxicity in Chickpea seedlings (Cicer arietinum L.)

Controversy exists as to whether ethanol ever accumulates totoxic levels in anaerobic tissues of higher plants. In orderto manipulate the internal concentrations of ethanol and relatethese to anaerobic injury, seedlings of chickpea (Cicer arietinumL.) were incubated under strict anoxia in vessels in which theanaerobic atmosphere either remained static or else was circulatedwith that of a large anaerobic incubator. Incubation with acirculating, as compared with a static, anaerobic atmospheredoubled the time that the seedlings could be kept under anoxiaand emerge in subsequent survival testing in the glasshouse.Circulating the anaerobic atmosphere gave a 13-fold reductionin the accumulation of ethanol in the seedlings. Parallel experimentswhich varied the ratio of head space relative to seedling numberconfirmed that the dilution of the volatile products of anoxia.increasedsurvival. These products included carbon dioxide, ethanol andtraces of acetaldehyde. While carbon dioxide may play a rolein modifying glycolytic activity under anoxia, it is suggestedthat it is not directly toxic and that it is the reduction inethanol concentration in the seedlings as a result of head spacedilution that contributes to their increased longevity in circulatinganaerobic atmospheres. Key words: Cicer arietinum L., Ethanol, Anaerobic conditions     

Influence of Donor Age on Establishing Well-Differentiated Clonal Cultures from Embryonic Chicken Retinal Pigmented Epithelium

Retinal pigmented epithelia (RPE) isolated from chicken embryos of various developmental stages were dissociated into single cells, and their ability to re-express defferentiated characteristics in clonal culture was investigated. The lighty pigmented, columnar cells isolated from stage 25 to 29 embryos dissociated more easily than the heavily pigmeted, cuboidal cells from embryos of stages 30 to 34. The yield of RPE cells per embryo increased with donor age, paralleling the growth of the epithelium in vivo . However, the potential these cells to attach, to proliferate, and to form typical, welldifferentiated RPE colonies declined with donor age. Cells from stage 25 embryos developed exclusively into large, typical epithelial colonies which expressed all stages of differentiation from flat, unpigmented cells at the margin to cuboidal, pigmented cells in the centre. At the other end of the spectrum, cells from stage 34 embryos frequently formed small, atypical colonies of unpigmented cells, in addition to typical but relatively small colonies. The plating efficiency (calculated on the basis of pigmented colonies formed within 3 weeks) dropped from more than 2% at stage 25 to 0.01% at stage 34.     

Evidence contrary to the existence of storage lipid in leaves of plants inhabiting cold climates

Abstract In a study of the lipid composition of the upland Empetrum nigrum subspp. hermaphroditum and Empetrum nigrum subspp. nigrum with a lowland distribution, no evidence was found to support the suggestion that lipids (triacylglycerols) play a major energy storage role in the leaves of alpine species. On a quantitative basis the triacylglycerols constituted less than 5% of the total lipid in both species and the lowland species possessed the higher levels of total lipid, neutral lipid and triacylglycerols. It is suggested that the presence of a well-developed waxy cuticle might account for the high total lipid levels encountered in dwarf evergreen shrubs.     

Growth of <Emphasis Type="Italic">Theileria parva</Emphasis>-infected Bovine Lymphoid Cells in Irradiated Mice

SEVERAL attempts to establish Theileria parva, the causative organism of East Coast fever of cattle, in laboratory animals^1–4 have failed. The recent successful establishment of T. parva macroschizont-infected bovine lymphoid cells in tissue culture⁵ provided a concentrated source of material which could be used in further attempts to infect laboratory animals.     

Mortality and survival of African Penguins Spheniscus demersusinvolved in the Apollo Seaoil spill: an evaluation of rehabilitation efforts

The bulk ore carrier Apollo Sea sank near Dassen Island, South Africa, on 20 June 1994 during a period of winter storms. Approximately 10 000 African (Jackass) Penguins Spheniscus demersus were oiled, collected and transported to the SANCCOB rescue centre; 5213 were released after cleaning, 4076 with flipper bands. We believe that most of the penguins oiled during this incident reached an island or the mainland alive, and that there was no mass mortality in the wild at the time of the oil spill. Birds from all parts of the breeding range were oiled, but most were from Robben and Dassen Islands. The overwhelming majority of released birds made the transition from the rescue centre to the wild successfully; 2652 had been resighted at breeding colonies within two years of their release; the cumulative number of birds was increasing steadily and an asymptote had not been reached by August 1996. There was a wide dispersal of released penguins, with recoveries and resightings over 1800 km of coastline between Algoa Bay and Walvis Bay.