Field studies on the bionomics of the free-living stages of St. Lucian Schistosoma mansoni.

Densities of Schistosoma mansoni miracidia and cercariae in natural habitats in three St. Lucian valleys were monitored over a 3-year period by exposure of sentinel snails, Biomphalaria glabrata, and a cercariometric technique, supplemented by sampling of field snails. Separate measures for control of S. mansoni transmission were under evaluation in two of the valleys. Sentinel snails became infected sporadically and their infection rates per valley ranged from 0·12% to 4·99%. S. mansoni miracidial inoculation rates ranged from 1 to over 4 per infected sentinel snail. Combined rainfall of more than 3 in on the day before any day of sentinel snail exposure interfered with miracidium-snail interaction. Densities of S. mansoni cercariae ranged from 0·05 to 21 per litre of water sampled. The number of cercariae detected in a habitat by cercariometry was directly proportional to the number of infected field snails. Sentinel snail infection rates exhibited a downward and an upward trend, respectively, in the controlled and uncontrolled areas, although the changes were not significant statistically.     

Spontaneous mutation in a thermoacidophilic archaeon: evaluation of genetic and physiological factors

We used direct selection of pyrE and pyrF mutants to estimate the rates of spontaneous mutation in Sulfolobus acidocaldarius as a function of genetic background and culture conditions. Fluctuation tests were applied to several genetically marked strains, including one isolated as a putative mutator strain, and to cultures grown over a wide range of temperature and other physiological conditions. The results suggested some impact of auxotrophic markers on the apparent rate of mutation, but no obvious pattern of effect of growth conditions, including those that gave evidence of being physiologically stressful. Received: 27 May 1997 / Accepted: 2 September 1997     

Bivalve distribution on coral carpets in the Northern Bay of Safaga (Red Sea, Egypt) and its relation to environmental parameters

Summary Bivalve assemblages on coral carpets in the Northern Bay of Safaga do not form distinct associations, but gradually shift in faunal composition. The taxonomic shift is accompanied by continuous variations in bivalve density and percentage of living individuals as well as by a change of coral associations and potential bivalve habitats. The gradual lateral change of associations is best documented byTridacna maxima and jewel box clams (Chamoidea) and is probably due to variations of the suspension load in the water column. High suspension loads in the water column are additionally indicated by ‘giant oysters’ (extremely large individuals ofHyotissa hyotis) and striking agglomerates ofLopha cristagalli. The vertical differentiation is best documented by the decrease of the zooxanthellateTridacna maxima and is probably due to the depth-dependent light penetration in the water column, which is attenuated in areas of high suspension load.     

A human challenge: discovering and understanding continental copepod habitats

Copepods have invaded an astonishing variety of aquatic and humid continental environments and microhabitats. The historical process of discovery and investigation of copepods in ephemeral, acid and thermal waters, subterranean waters and sediments, phytotelmata, humid soils, leaf litter, human-modified and artificial habitats, and other situations extends over about 130 years. The methods developed to collect in and study these habitats range from simple nets to elaborate pumping systems and diving techniques. Investigations of non-lacustrine continental environments have contributed greatly to the understanding of aspects of copepod biology such as reproduction, diapause and population dynamics. Questions regarding faunistics and biological diversity, biogeography, evolution, transport and introductions of alien species have also been informed by such studies. This article briefly reviews these topics, and provides detailed lists of records from some of the less well-known kinds of habitats.     

Evidence bearing on the origin of infraspecific disjunction inSophora gypsophila (Fabaceae)

Morphometrical, cytological, chemical and ecological data are presented concerning the origin of infraspecific disjunction inSophora gypsophila, its 2 varieties, var.gypsophila and var.guadalupensis, being known from only 2 very local sites which are separated by approximately 300 km. It is concluded that the populations are remnants of a much more widespread, highly variable sib of Wisconsin time.     

The role of the root cell wall in the heavy metal tolerance ofAthyrium yokoscense

Cells of the roots ofA. yokoscense growing on metalliferous habitats were fractionated into their cell wall and cytoplasmic components. About 70–90% of the total copper, zinc and cadmium was located in the cell wall. Copper had a markedly greater affinity for the cell wall than zinc and cadmium, and was prevented from entering the cytoplasm. A large proportion of these heavy metals in the cell wall were exchanged as ions. The capacity of the cell wall for exchanging metal ions inA. yokoscense was higher than in other plants growing on metalliferous habitats. However, compared with different ferns unable to grow on metalliferous habitats, this capacity was not unique toA. yokoscense. Consequetly, the root cell wall ofA. yokoscense is considered to be an important site of metal ion storage and may play the role of an excretory organ for heavy metals. On the other hand, as proportion of the heavy metls was transported to the cytoplasm, where the metal content was much higher than the average for normal ferns. This would suggest thatA. yokoscense has another metabolic mechanism related to metal tolerance.     

Conservation of moths in The Netherlands: population trends, distribution patterns and monitoring techniques of day-flying moths

The loss of butterfly diversity in north-western Europe has been studied extensively but much less is known about the status of other macrolepidoptera. The present paper presents results of the research on mainly day-flying larger moths carried out by Dutch Butterfly Conservation in The Netherlands. Research started in 1992 with a public campaign and a mapping programme, leading to an increase in the number of records of macrolepidoptera. Results from the mapping programme on day-flying moths showed a strong general decrease in The Netherlands, comparable with the loss of butterfly diversity. Transect counts have been undertaken since 2000 for a few species and this method is sufficient to measure trends over time if the moth densities are high enough. Another research component was to focus on marshland habitats in The Netherlands. Fifty-five characteristic marshland moth species were selected and the relative abundance of nearly all these species has declined. These trends were compared with four other countries in the Atlantic biogeographical zone. The relative abundance of the majority of marshland moths in The Netherlands was found to be higher than those in other European countries, so that The Netherlands has a special responsibility for the conservation of the moths of its marshes. Moreover, we emphasise that, next to butterflies, moths can be of great use in nature conservation because of their potential significance as indicator species in endangered habitats.     

Potential food resources available to malleefowl Leipoa ocellata in marginal mallee lands during drought

Abstract Prime mallee lands that once supported high densities of malleefowl, Leipoa ocellata in New South Wales have been extensively cleared for agriculture. Malleefowl are now restricted largely to more and habitat. Given the added competition from introduced herbivores, there is concern that these marginal habitats may not contain sufficient food resources to support viable populations of malleefowl, particularly in times of drought. An opportunistic feeding strategy and omnivorous diet enable malleefowl to exploit a diverse array of food items. Vegetative and invertebrate food resources available to malleefowl in marginal mallee lands were monitored over a period of 1 year during drought. Food resources were varied, transient and patchily distributed. Composition and abundance fluctuated considerably, but potential food was never entirely absent. Despite the prevailing drought, food was obtainable throughout the year provided malleefowl adapted to the fluctuating availability of each of the various potential food resources. Reduced food resources in marginal habitat is not implicated as a major factor in the demise of the malleefowl. Food was most abundant between August and November, inclusive, due largely to the abundance of herbs, the diverse supply of buds, flowers and fruit on perennial shrubs, and the sporadic proliferation of cockroaches. Food availability was least, and therefore most critical, during February, March and June. The most favourable time of the year, in terms of available food resources, for the release of captive-bred individuals was during spring, around September.