Foraging interactions between Wandering Albatrosses Diomedea exulans breeding on Marion Island and long-line fisheries in the southern Indian Ocean

Wandering Albatrosses Diomedea exulans are frequently killed when they attempt to scavenge baited hooks deployed by long-line fishing vessels. We studied the foraging ecology of Wandering Albatrosses breeding on Marion Island in order to assess the scale of interactions with known long-line fishing fleets. During incubation and late chick-rearing, birds foraged further away from the island, in warmer waters, and showed high spatial overlap with areas of intense tuna Thunnus spp. long-line fishing. During early chick-rearing, birds made shorter foraging trips and showed higher spatial overlap with the local Patagonian Toothfish Dissostichus eleginoides long-line fishery. Tracks of birds returning with offal from the Toothfish fishery showed a strong association with positions at which Toothfish long-lines were set and most diet samples taken during this stage contained fishery-related items. Independent of these seasonal differences, females foraged further from the islands and in warmer waters than males. Consequently, female distribution overlapped more with tuna long-line fisheries, whereas males interacted more with the Toothfish long-line fishery. These factors could lead to differences in the survival probabilities of males and females. Non-breeding birds foraged in warmer waters and showed the highest spatial overlap with tuna long-line fishing areas. The foraging distribution of Marion Island birds showed most spatial overlap with birds from the neighbouring Crozet Islands during the late chick-rearing and non-breeding periods. These areas of foraging overlap also coincided with areas of intense tuna long-line fishing south of Africa. As the population trends of Wandering Albatrosses at these two localities are very similar, it is possible that incidental mortality during the periods when these two populations show the highest spatial overlap could be driving these trends.     

Methods for detecting non-randomness in species co-occurrences: a contribution

Summary Comparison of co-occurrences between species on a group of islands with those expected from a randombased null model could provide evidence on community structure. However, it is difficult to decide on the appropriate null model. Gilpin and Diamond proposed a model and a test for departure from it, but this test is shown to indicate significant structure even when applied to a matrix of random numbers. An alternative method is suggested, using the distribution of Gilpin and Diamond's deviation as test statistic, but determining the expected distribution by Monto Carlo simulation, and using many such simulations as a randomisation test of significance. The null model used accepts the observed totals of occurrences for islands and species; it therefore offers a somewhat conservative test. Applied to the Vanuatu bird data that Gilpin and Diamond used, significant departure from a null model is seen, but with an excess of extreme negative associations, the opposite result from that given by Gilpin and Diamond's method. It is not possible to tell whether the negative associations are due to autecology, biogeography, or to interactions between species.     

Reproductive success,spontaneous embryo abortion,and genetic load in flowering plants

Summary Reproductive success is divided into two phases: preemergent (the number of viable seeds that enter the ambient environment) and postemergent (the percentage of progeny that survive to reproduce). We studied preemergent reproductive success (PERS) in flowering plants by measuring the fruit/flower (Fr/Fl) ratio and the seed/ovule (S/O) ratio in a number of species of outcrossing and inbreeding plants, where PERS=the product of (Fr/Fl) and (S/O). In order to determine the influence of the ambient environment (including resource availability) we studied pairs of outcrossing and inbreeding species occurring in the same habitat. Among outcrossing species PERS averaged about 22%, whereas in inbreeding species the average was approximately 90%. The progeny/zygote (P/Z) ratio was studied in hand-pollinated populations in Epilobium angustifolium (a strongly outcrossing species) from populations in Oregon and Utah, by direct observation of embryogenesis at twoday intervals throughout the course of seed development. The P/Z ratio in both populations averaged near 30%, and the developing embryos showed a surprising array of abnormalities that resulted in embryo death. During early development >95% of the ovules had normally developing globular embryos, but beginning with differentiation (cotyledon formation) about 70% of the original globular embryos aborted during the course of embryogenesis and seed development. The clustering of developmental lethals during peroids of major differentiation events parallels the animal model of development. We found little evidence that PERS was limited by the ambient environment (including resource availability), pollination, or factors associated with the inbreeding habit. Instead, PERS was found to be inextricably linked to outcrossing plants, whose breeding systems promote genetic variability. The high incidence of developmental lethals in E. angustifolium and the resulting low P/Z ratio (ca. 30%) is attributed to genetic load (any lethal mutation or allelic combination) possibly working in combination with developmental selection (interovarian competition among genetically diverse embryos). Examples of maternally controlled, fixed patterns of ovule abortion with respect to position or number are discussed. However, we found no need to employ female choice as a hypothesis to explain our results for the extensive, seemingly random patterns of embryo abortion in E. angustifolium and other outcrossing species. A more parsimonious, mechanistic explanation based on genetic load-developmental selection is sufficient to account for the differential survivorship of embryos. Likewise, the traditional concept of a positive growth regulator feedback system based on the number of surviving ovules in an ovary can account for subsequent fruit survivorship.     

Phosphorus nutrition of jarrah (Eucalyptus marginata) seedlings

Summary Effects of calcium phosphate supply on plant dry matter and phosphorus concentrations of parts of jarrah (Eucalyptus marginata) seedlings grown in a lateritic topsoil from the jarrah forest were examined in two glasshouse trials. Phosphorus deficiency depressed root and shoot dry weights and severely deficient leaves were smal and purple with prominent red major veins. Phosphorus deficiency severely reduced stem phosphorus levels (0.5% to 0.02%, experiment 1). Phosphorus concentrations were higher in bark than wood and the amount of phosphorus in the bark was sensitive to stem age and phosphate supply. Phosphorus adequate plants had bark phosphorus concentrations in the range 0.2–0.9% compared to <0.1% in deficient plants (experiment 2). Jarrah leaves accumulated dry matter up to 80 days after expansion and some leaves exported phosphorus during this period. Bark analysis may therefore be preferable to leaf analysis for detecting phosphorus deficiency in this species.     

Plant Morphological and Biochemical Responses to Field Water Deficits : II. Responses of Leaf Glycerolipid Composition in Cotton

The effects of water deficits on leaf glycerolipid composition were analyzed in two photoperiodic strains of field grown cotton (Gossypium kirsutum L.) that differ in sensitivity to drought. Leaves from plants grown under dryland conditions exhibited increased dry weight and specific leaf weight. The average midday leaf water potential in the dryland treatment decreased to −1.9 and −2.4 megapascals, respectively, for the T25 and T185 genotypes. Total leaf lipid content of plants exposed to dryland conditions was 5.9 and 7.5% of leaf dry weight for strain T25 and T185, respectively. The difference in leaf lipid content between these genotypes was caused by water deficits and was attributed to loss of both phospholipids and glycolipids in strain T25. There was no apparent loss of phospholipids due to water deficits in the T185 genotype; however, a significant loss of glycolipids was partially compensated by a 2-fold increase in triacylglycerol. No change in triacylglycerol was found between treatments in T25 leaves. Water deficit caused a significant decline in the relative degree of acylunsaturation in phospholipids and glycolipids from both genotypes; however, the double bond index for triacylglycerol increased in both genotypes. It is believed that the observed responses of leaf lipid composition to dryland conditions may be an additional criterion for characterization and selection of new drought-tolerant cotton genotypes.     

Cytochrome-c oxidase. Subunit structure and proton pumping

This article reviews the significance of the subunit structure of cytochrome-c oxidase in proton pumping and in particular summarizes available evidences for or against a role of subunit III in the control of this important function of the enzyme.     

Growth of a human carcinoma (HEp3) in nude mice: rapid and efficient metastasis

Our aim was to identify conditions which would permit the development of spontaneous metastasis of a human tumor in nude mice in a rapid and predictable manner and to explore ways to quantitate metastasis. Using a human squamous carcinoma--HEp3--we determined that invasiveness and metastasis were influenced by the host. HEp3 cells grew very rapidly and without a significant lag period in Balb/c and NIH(S)-II nude mice kept in aseptic conditions; a much longer lag period was observed in NIH-Swiss mice kept in conventional conditions. The HEp3 tumor displayed a highly invasive behavior in N-NIH(S)-II mice, in which it invaded the body wall, gaining access to the peritoneal cavity. Microinvasion was noted in all strains of mice inoculated with HEp3 cells. To prolong survival of the mice until metastases became evident, primary tumors were excised when they weighed 1-2 gm. N-NIH(S)-II and Balb/c nude mice, maintained in germ-free conditions, were most receptive to the development of metastases-lung metastases developed in 80% of these mice. Over 60% of all metastases were present within 4 weeks following the removal of the primary. Only 26% of tumor bearing NIH-Swiss developed lung metastases. Lung metastases were observed in some mice in the absence of local microinvasion, local tumor recurrence, and regardless of the presence of lymph node involvement. They were also noted in mice from which primary tumors were not excised. We compared three methods of lung metastasis detection: histology, detection of tumor cells in the cultures of lung minces, and the measurement of the levels of human urokinase-type plasminogen activator directly in the lysates of lungs. The detection of tumor cells in cultures of lung minces appeared to be the most sensitive of these methods and the determination of enzyme in lung lysates seemed to hold most promise for a quantitative approach. These data indicate that, the type of tumor, as well as the genetic background and the maintenance conditions of the host, have to be carefully selected to ensure the successful outcome of the particular tumor-host interaction being studied. Adherence to these guidelines allowed us, in the case of the HEp3 tumor, to develop a rapid, predictable, and efficient model in which to study factors affecting metastasis of this human tumor.