The geological setting of the earliest life forms

Summary Life on Earth may have begun about 4×10⁹ years (4 Ga) ago. Plate tectonics probably operated in the early Archaean, with rapid spreading at mid-ocean ridges, a komatiitic (magnesium-rich) oceanic crust, active volcanic arcs and the development of extensional basins on continental crust. Shallow water environments would have been more restricted and probably shorter-lived than in later geological times; however, extensive shallow seas existed in the later phases of the development of extensional basins. Bacterial communities-presumably photosynthetic-have probably existed in such shallow-water settings and probably at shallow depths in the oceans for at least 3.5 Ga. Because the mid-ocean ridges were probably subaqueous, hydrothermal systems would have been very vigorous and would have offered suitable habitats for early chemo-autotrophic bacterial communities. Early life forms probably also occupied vesicles in lavas, pumice and volcanic breccias, and pores in soft sediments, living in the constant flux of fluid flushing through permeable strata. Other, similar habitats would have existed in volcanic island arcs and in extensional basins.     

Continued use of soft‐metal bands on gulls in North America reduces the value of recovery data

Use of soft‐metal (aluminum alloy) bands on gulls (Laridae) is known to result in high rates of band loss and, as a result, hard‐metal (monel, incoloy, or stainless steel) bands are superior for most studies. However, the U.S. Bird Banding Laboratory (BBL) and the Canadian Wildlife Service Bird Banding Office continue to issue soft bands for use on gulls, and the BBL does not make specific recommendations about use of hard bands so many banders continue to use soft bands. For wholly marine species of gulls banded in North America since 1996, ～20% have been banded with soft bands; the proportion of soft bands used on partially freshwater gulls was ～70% up to 2009, but has since fallen to 40%. Using hierarchical Bayesian models in program MARK, we analyzed recovery data for three gull species and found that estimates of annual survival rates derived from soft bands (0.68–0.81) were lower than those derived from hard bands (0.85–0.96). Comparison of survival rates of Herring Gulls (Larus argentatus) in the Great Lakes basin and on the Atlantic coast provided no evidence that soft bands last longer in freshwater than saltwater. Band loss compromises many types of studies, including those assessing the possible effects of climate change. We recommend that use of soft bands on gulls be discontinued, and that banders be required to use hard bands on these species in the future. The same consideration applies to other long‐lived species, including some waterfowl and all albatrosses, pelicans, cormorants, shearwaters, petrels, terns, shorebirds, and alcids. Use of hard bands should be based on expectations about a species’ longevity and evidence of band wear, rather than on whether or not it occurs in saltwater.     

Bioenergetic theory predicts infection dynamics of human schistosomes in intermediate host snails across ecological gradients

Epidemiological dynamics depend on the traits of hosts and parasites, but hosts and parasites are heterogeneous entities that exist in dynamic environments. Resource availability is a particularly dynamic and potent environmental driver of within‐host infection dynamics (temporal patterns of growth, reproduction, parasite production and survival). We developed, parameterised and validated a model for resource‐explicit infection dynamics by incorporating a parasitism module into dynamic energy budget theory. The model mechanistically explained the dynamic multivariate responses of the human parasite Schistosoma mansoni and its intermediate host snail to variation in resources and host density. At the population level, feedbacks mediated by resource competition could create a unimodal relationship between snail density and human risk of exposure to schistosomes. Consequently, weak snail control could backfire if reductions in snail density release remaining hosts from resource competition. If resource competition is strong and relevant to schistosome production in nature, it could inform control strategies.     

Variation in the ribosomal internal transcribed spacers and 5.8S rDNA among five species of Acropora (Cnidaria; Scleractinia): patterns of variation consistent with reticulate evolution

The ITS sequences of Acropora spp. are the shortest so far identified in any metazoan and are among the shortest seen in eukaryotes; ITS1 was 70-80 bases, and ITS2 was 100-112 bases. The ITS sequences were also highly variable, but base composition and secondary structure prediction indicate that divergent sequence variants are unlikely to be pseudogenes. The pattern of variation was unusual in several other respects: (1) two distinct ITS2 types were detected in both A. hyacinthus and A. cytherea, species known to hybridize in vitro with high success rates, and a putative intermediate ITS2 form was also detected in A. cytherea; (2) A. valida was found to contain highly (29%) diverged ITS1 variants; and (3) A. longicyathus contained two distinct 5.8S rDNA types. These data are consistent with a reticulate evolutionary history for the genus Acropora.      

The effects of azadirachtin on the testes of the desert locust,Schistocerca gregaria (Forskål)

Testes removed from Schistocerca gregaria, injected with 5 or 7&mgr;g azadirachting(-1) body wt on day 0-2 of the Vth instar and killed by decapitation 20days after treatment, showed significant reductions between the widths, lengths and volumes of the treated groups, compared to control insects. Under cytological examination these testes, from insects exhibiting classical signs of azadirachtin poisoning, showed arrested spermatogenic meiosis at Metaphase I.     

Production and characterization of monoclonal antibodies to a Veillonella species from a continuous-flow culture system of chicken cecal bacteria

Administering native intestinal flora to newly hatched chicks protects against cecal Salmonella colonization, and is known as competitive exclusion. Continuous-flow culture systems have been used to maintain defined competitive exclusion cultures. We have recently demonstrated that such a stable continuous-flow culture, CF3, contains 29 bacterial strains representing ten genera. Broiler chicks treated with CF3 are protected against Salmonella colonization of the ceca. Such protection is correlated with elevated concentrations of proprionic acid in the cecal contents of treated chicks. In this study we report on the preparation and characterization of monoclonal antibodies to one of the proprionic acid producing anaerobes contained in CF3, namely Veillonella CF3. Five different monoclonal antibodies were characterized with respect to: (1) isotype; (2)Veillonella specificity as judged by cross-reactivity profiles with other bacteria; (3) sensitivity as measured by the limit of detection of the number of colony forming units of Veillonella; and (4) antigen recognition of Veillonella by Western Blot analysis. These antibodies have been used to enumerate Veillonella in both the CF3 cultures and in the ceca of young chicks.     

Seasonal declines in reproductive success of the common tern Sterna hirundo: timing or parental quality?

Reproductive success declines over the course of the breeding season in many bird species. Two categories of hypothesis have been evoked to explain this decline. The “timing” hypothesis suggests that seasonal declines in breeding success are attributable to the date of laying. The “parental quality” hypothesis suggests that seasonal declines result from the fact that young, inexperienced, or low quality birds breed later in the season. To evaluate the relative importance of timing and parental quality, egg exchanges and removals were used to manipulate hatching dates of common terns Sterna hirundo. Indices of quality, attendance, provisioning rates, and reproductive success of birds in three experimental groups (delayed hatch pairs, advanced hatch pairs, and pairs induced to relay) were compared to those of date‐matched controls. Pairs that hatched chicks early raised more chicks than pairs hatching chicks late in the season, regardless of initial laying date. This suggests that hatching chicks early is advantageous in itself. Our results, however, also support the parental quality hypothesis. There was a significant negative relationship between natural laying date and fledging success, independent of hatching date. Differences in chick growth and survival suggest that higher quality adults may be able to compensate for the disadvantages of late hatching dates and achieve similar reproductive success to that of pairs hatching chicks early. We found that pairs hatching chicks late in the season were subject to more incidents of kleptoparasitism than those hatching chicks early. This may be a proximate factor contributing to seasonal declines in reproductive success for common terns, although such a mechanism would not be likely in non‐colonial species. Failure to control for egg quality may have biased the results of some prior egg exchange experiments. Additionally, altered cost of incubation may be an unavoidable confounding factor in studies designed to manipulate timing of breeding.     

A high incidence of jaagsiekte following experimental cold exposures in housed sheep

The fortuitous occurrence of cases of jaagsiekte (sheep pulmonary adenomatosis) in a group of young Scottish Blackface sheep exposed to experimental cold stress is described. The incidence (11/62 cases) was high and the age of onset early (less than 20 months) by comparison with the authors' local experience of the disease. There was also some indication that males were more susceptible (9/26) than females (2/36). The results are not conclusive, but suggest the need for similar cold stress experiments in animals deliberately infected with the disease.

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Zusammenfassung Es wird über das zufällige Auftreten von Jaagsiekte (Lungenadenomatose der Schafe) in einer Gruppe von Schottisch-Blackface Schafen berichtet, die in einem Kältebelastungsversuch verwendet wurden. Die Häufigkeit war hoch (11/62 Fälle) und nach den Erfahrungen der Autoren früh, denn die Tiere waren unter 20 Monate alt. Ausserdem bestanden Hinweise auf Geschlechtsunterschiede in der Empfindlichkeit, weil mehr männliche (9/26) als weibliche Tiere (2/36) erkrankten. Die Ergebnisse sind nicht endgültig. Zur weiteren Abklärung sind Versuche erforderlich, in denen vorsätzlich infizierte Tiere der gleichen Kältebelastung ausgesetzt werden.

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Resume On rapporte ici sur l'apparition fortuite de "Jaagsiekte" (adénomatose pulmonaire du mouton) dans un groupe de moutons de la race écossaise à face noire faisant l'objet d'un essai de contrainte au froid. La fréquence des cas d'infections était élevée (11 bêtes malades sur 62) et très précoce selon l'expérience des auteurs, les animaux n'étant âgés que de 20 mois au plus. En outre, on en tire certaines indications concernant une différence possible entre les sexes, vu que la proportion des béliers atteints (9/26) est nettement plus élevée que celle des brebis malades (2/36). Ces résultats ne sont cependant pas définitifs. Afin de les compléter, il faudrait placer des animaux préalablement infectés dans des conditions semblables de contrainte au froid.