Colonization and succession of invertebrate communities in a new stream in Glacier Bay National Park, Alaska

1. Invertebrate colonization of a new stream following glacial recession is documented for a 12 year period from 1978 to 1990. 2. Invertebrates, particularly Chironomidae, displayed site-specific temporal succession over the study period, at the end of which a number of the pioneer colonizers were no longer collected. 3. Maximum species richness was found in 1988, whereas total invertebrate density was greatest in 1978, 10 years earlier. 4. Water temperature appeared to be the most significant factor determining the year of colonization of invertebrate taxa. As a result, deterministic trends were apparent in patterns of invertebrate colonization and succession. 5. Salmonids first colonized the stream in 1988. Dietary analyses of juvenile Dolly Varden (Salvelinus malma) showed preferential selection for blackfly and small chironomid larvae.     

Distribution of pedicle boring traces and the life habit of Late Paleozoic leiorhynchid brachiopods fiom dysoxic habitats

Alexander, R.R. 1994 10 15: Distribution of pedicle boring traces and the life habit of Late Paleozoic leiorhynchid brachiopods from dysoxic habitats.
Pedicle boring traces, Podichnus isp., are concentrated on the anterolateral commissure of both valves of Leiorhynchoidea carboniferum and L. weeksi from the black ferruginous micrites of the Chainman Formation (Upper Carboniferous; west-central Utah, USA) and black phosphatic ('False Cap') limestone of the Phosphoria Formation (southeastern Idaho, USA), respectively. The absence of Podichnus isp. from the posterior of shells of both species indicates that the beak of the shell was buried in the mud, inaccessible to colonization by conspecific larvae. The concentration of pedicle boring traces near the anterolateral incurrent regions of leiorhynchid shells with a well-developed central fold further suggests that settling conspecific larvae behaved rheotaxically. Larvae were induced to metamorphose near the commissure of the host shell, where suspended food was drawn to the incurrents of the host. The piggybacked mode of life on the anterior of conspecific hosts provided a refuge for juveniles above the dysoxic black sediments. In contrast, modem brachiopods that live as epibionts on skeletal substrates display either a random or posteriorly concentrated distribution of pedicle boring traces. Permian, Carboniferous, brachiopods, leiorhynchids, Podichnus, dysoxic, rheotaxis .     

Women,Labour and Fertility: Population Growth in Nineteenth Century Java

The sharp increase in Java's population after 1830 is usually explained in terms of higher living standards and consequent lower mortality resulting from Dutch colonization, but there is little historical evidence supporting such an interpretation and much to refute it. An alternative view is that Java's population growth after 1830 was due to increasing fertility. The major constraint on Javanese fertility prior to this period had been extended periods of postpartum absistence, the length of which was determined by the duration of breastfeeding because people believed semen had deleterious effects on breast milk. In 1830 a system of forced cultivation of export crops was imposed by the Dutch rulers and greatly increased the amount of labour which Javanese households required to reproduce themselves. The arduous work women began to undertake made it increasingly difficult to breastfeed their children. As the average period of breastfeeding fell, the average period of postpartum abstinence declined and fertility increased.     

Bluetongue epidemiology in the Caribbean region: serological and entomological findings from a pilot sentinel system in Trinidad and Tobago

When monitored by the agar gel immunodiffusion test for antibody to bluetongue viruses, a sentinel flock of twenty-five lambs remained seropositive through the year, whereas in a sentinel herd of twenty calves only two individuals seroconverted and these became negative again within 2 months. A light trap operated with the calf herd yielded high numbers of Culicoides insignis Lutz (over 18,000 per trap night) along with C. filariferus Hoffman, C. pusillus Lutz, C. leopoldi Ortiz, C. foxi Ortiz, C. limai Barretto, C. diabolicus Hoffman and C. guyanensis Floch and Abonnenc. Culicoides were trapped at the sheep station which had housed the lambs 3 years following the sentinel study. No virus was isolated from pools of C. insignis, C. filariferus and C. pusillus. Six other species were collected in insufficient numbers to warrant attempted virus isolations.     

Comparative hydrodynamic stability of brachiopod shells on current-scoured arenaceous substrates

Selected brachiopod specimens were placed on a well-sorted medium grained sand (0.5 mm) in a recirculating flume and subjected to a constant unidirectional current of 26–27 cm/sec. The specimens were placed in each of six feasible life-orientations. In three orientations, the valves were reclining with either the lateral, anterior or posterior profile upcurrent. In three orientations, the commissural plane was perpendicular to the substrate with either the pedicle or brachial valve upcurrent, or a lateral margin upcurrent. Destabilization indices were calculated for each specimen in each orientation based on the elapsed time until the specimen reoriented. Nonstrophic biconvex brachiopods are most stable with the valves reclining on the substrate. Among orientations with the valves erect, the pedicle valve upcurrent and the brachial valve upcurrent are the most and least stable orientations, respectively. Shell stability increased among nonstrophic specimens that were more equi-biconvex. Biconvex strophic brachiopods are also more stable if the valves were equi-biconvex, cither compressed (biplanate) or inflated, provided that the specimen was propped up on its hingeline with a lateral margin upcurrent. Catacline interareas afforded greater stability than procline, apsacline or orthocline interareas when the valves were perpendicular to the substrate. Accentuated plication reduced shell stability. Alate biconvex forms were often more stable if the valves were vertical to the substrate rather than reclining. Alate biconvex geometries are more stable than nonstrophic and strophic biconvex forms if the commissural plane is perpendicular to the substrate and parallel to the current. Broad catacline interareas increased stability in all orientations. Plano-convex and dorsi-biconvex alate forms are usually less stable than equi-biconvex or ventri-biconvex alate geometries. Concavo-convex geometries are stable in all orientations except with the valves nearly vertical to the substrate and parallel to the current. Spines greatly retard sediment-scour and maintain concavo-convex specimens in orientations with the valves elevated above the substrates. D Brachiopoda, shell shape, hydrodynamic stability.