Degradability and Sediment Sorption of an Alcohol Polyglycol Ether Surfactant Putatively Useful for the Control of Red Swamp Crayfish in Rice Fields

This work reports studies of the degradation rates of a fattyalcohol polyglycol ether non-ionic surfactant, Genapol OXD-080, putatively useful for the control of red swamp crayfish (Procambarus clarkii Girard) in rice fields under laboratory and field conditions. The influence of temperature,sediment site specificity and sorption were taken into account.The degradation kinetics of the surfactant depends on the experimental conditions: type of inocula and temperature. Thedistribution of this chemical in aquatic systems was also examined. Genapol OXD-080 was removed into the sedimentsreadily after application, and sorption was considered the majorpath of removal from the water phase. Data suggest that furtherstudies are required regarding the effects of Genapol OXD-080 in aquatic organisms resident in rice fields, in parallelwith the development of technologies related with the use ofsurfactants to control P. clarkii populations.     

Daily and seasonal feeding rhythmicity of <Emphasis Type="Italic">Palaemonetes varians</Emphasis> (Leach 1814) from southwestern Europe

The feeding activity rhythm of Palaemonetes varians (Leach 1814) was studied by collecting stomachs over a 24-h cycle in four different seasons of 1996 and spring–summer of 1997 to assess a regulation of this behaviur dependent upon seasonal variations in photoperiod length. A total of 6,692 stomachs were collected from a population reared in an extensive earthen pond located in the Guadalquivir Estuary salt marshes (Spain). Stomach fullness (f) classification was performed with a stereomicroscope by means of a four-point visual qualitative scale. Results showed that a high proportion of stomachs were empty in all seasons considered and a great variability in the data occurred irrespective of the time of the day. The number of full stomachs at each catch were represented over 24-h for each sampling season. Time series showed the occurrence of a feeding activity rhythm phased at day–night transitions. The sunset peak occurred in all months of sampling, while the sunrise one occurred in summer. Results are discussed in relation to available data on behavior, moulting, and reproduction of this and other species of the same genus.     

Economic Underdevelopment And Sustainable Development In The World:Conditioning Factors,Problems And Opportunities

This paper deals with the various factors that condition underdevelopment in the world. It suggests some alternatives and points out the potential opportunities that both the developed and the underdeveloped world will have in the coming years to change the gloomy prospects that we see today. The present paper outlines the trends in historical priorities in development, changing as they pass from economic development to social development to ecological conservation – the three pillars of Sustainable Development.The paper analyses the importance of geography, a very relevant and often neglected conditioning factor. Also, it analyses the role of socio-economic conditioning factors like political immaturity, demographics, land ownership and external debt.Furthermore, the current opportunities for economic take-off are presented, from cash surpluses to low interest rates, from natural resource management to tourism or migration, from the Information Revolution to liberalisation of agricultural markets. Current obstacles are also analysed. The paper, on the basis of current facts and figures, reaches the conclusion that there is a structural need for sustained development aid for most poor countries, but it must be distributed in a more rational way.Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue.     

Effects of hand weeding strip and nitrogen fertilizer on corn plants

The objective of the present research was to evaluate effects of different strip weed control associated with nitrogen fertilizer on corn applied after planting. The experiment was set and conducted in Botucatu, S?o Paulo State, Brazil, and the hybrid planted was Dekalb 333-B. A completely randomized block design with four replications was used. Experimental plots were disposed as a factorial scheme 2 x 2 x 4, constituted by two types of weeding on row (with or without manual hoeing), two types of weeding on inter-row (with or without manual hoeing), and four nitrogen levels applied after planting (00, 60, 90, and 120 kg ha(-1)). Plots were composed by six rows with 5 m length. Nitrogen fertilizer was applied at 35 days after emergence (d.a.e). For weed community it was evaluated: weed density, dominancy, frequency, and relative importance. The main weed species were: Brachiaria plantiginea, Amaranthus retroflexus, Bidens pilosa, Cyperus rotunds, Brachiaria decumbens, Euphorbia heterofila, Oxalis latifolia, Acanthospermum hispidum, Commelina benghalensis. It was evaluated corn height at 40 and 100 d.a.e., first ear insertion height at 100 d.a.e., and final grain yield at harvesting. Plants and first ear insertion height were affected when nitrogen fertilizer was not applied. Treatments without weed control showed that weed interfered negatively with plants height. There were no correlation between weeds and nitrogen fertilizer for all parameters evaluated. Parcels without weed showed the highest ear weights and final grain production. Treatments that received nitrogen fertilizer, independently of studied arrangement, provided higher yields.     

Perceived changes in well-being and happiness with gardening in urban organic allotments in Portugal

Urban allotment gardens (AG) in Portugal have increased in recent years, as in many other European countries and worldwide. The contribution of these gardens to the happiness and well-being of urban populations has been recognized, but evaluations of their benefits are still very scarce. The objective of this study was to evaluate this contribution, based on the urban organic AG of the Devesa Park in Vila Nova de Famalicão, Portugal. The sample included 65 gardeners who completed the self-administered questionnaires of Bem-Estar Pessoal (personal well-being scale), Felicidade Subjetiva (subjective happiness scale) and sociodemographic characteristics. Respondents were mainly adults under 65 years, married and academically well qualified and about half of them had a professional activity, with nearly one third being retired. They considered themselves happy with their life (Personal Well-being Index = 74.5%) and revealed an optimistic and positive attitude towards life, regardless of economic or social difficulties. The increased frequency of visits for gardening was positively related to a greater perception of subjective happiness. The gardeners who visited the AG more frequently considered themselves happier from a self-perspective and in comparison with peers. It can be suggested that urban organic AG represent a means for enhancing citizen well-being, contributing positively to their feelings of happiness and life satisfaction, changing behaviours and developing personal capacities. Beyond economic measures, urban AG can be recommended to capture the well-being of societies.     

Settlement patterns and post-settlement survival in two Mediterranean littoral fishes: influences of early-life traits and environmental variables

We examined the relationships between daily pattern of settlement and environmental parameters during two consecutive years in two littoral fishes, Lipophrys trigloides (Blenniidae) and Chromis chromis (Pomacentridae), in the NW Mediterranean Sea. We also used individual early-life traits (pelagic larval duration, size at hatching and size at settlement) calculated from otoliths, to study the proximate causes of settlement variability and size-selective mortality after settlement. Several early-life characteristics of L. trigloides (planktonic larval duration and size at hatching), and environmental variables averaged during the whole planktonic period (e.g. water temperature, wave height, solar radiation) were related with the magnitude of settlement. In contrast, C. chromis showed no significant relationships between early-life traits and the magnitude of settlement, and a weak relationship between settlement magnitude and environmental variables. Furthermore, juvenile survivors showed larger size at hatching than settlers, indicating that size at hatching affected the juvenile survival of the two species. These results suggest that survival was linked largely to conditions at hatching for both species.     

A field test of the intraspecific brood parasitism hypothesis in the golden egg bug (<Emphasis Type="Italic"> Phyllomorpha laciniata</Emphasis>)

In natural populations of golden egg bugs ( Phyllomorpha laciniata), females lay eggs on plants where they develop unattended, or on conspecifics, where they remain firmly glued until the nymphs hatch and start an independent life. Mortality rates among eggs laid on plants are higher than among eggs carried by adults. Because females cannot lay eggs on themselves, in order to improve offspring survival, they have to lay eggs on other individuals. Two hypotheses have been proposed to explain egg carrying: (1) the mating pair intraspecific brood parasitism hypothesis suggests that females dump eggs on copulating pairs, and (2) the paternal care hypothesis suggests that the system is driven mainly by males accepting eggs to improve the survival rates of their own offspring. Our data from the field show that 77% of the eggs are carried by males, because more males than females carry eggs, and because males carry a greater number of eggs. In addition, we show that mating males carry more recently laid eggs than single males. These results support the view that egg carrying is performed predominantly by males and that eggs are laid on males by their current mating partner, probably between repeated copulations. Males are likely to accept eggs, despite intermediate levels of paternity, because they cannot discriminate in favour of their own eggs, because rejected eggs will face 97% mortality rates on plants, and because they do not suffer mating costs when they carry eggs. However, females carry 23% of the eggs, but no differences in egg carrying have been found between mating and single females, suggesting that this is not the result of egg dumping while females are copulating. Egg carrying by females could reflect low levels of intraspecific parasitism, which is likely to reflect the low rate of successful attempts by egg-laying females who try to oviposit on other conspecifics rather indiscriminately, in an effort to improve the survival of their offspring.     

Differences in sterol composition of clams (<Emphasis Type="Italic">Ruditapes decussatus</Emphasis>) from three rías in Galicia (NW Spain)

The sterol composition of three different populations of Ruditapes decussatus from three localities close to each other, but where different environment conditions prevail, was investigated over a period of 14 months. Sterols of adult clams were isolated by thin layer chromatography and identified by gas chromatography/mass spectrometry. In all samples, the major sterol component was cholesterol (>40% of total sterols); other sterols identified were 24-norcholesta-5,22-dienol, 22-cis-dehydrocholesterol, 22-trans-dehydrocholesterol, brassicasterol, 24-methylene-cholesterol, campesterol, stigmasterol, -sitosterol and isofucosterol. At each locality, changes in sterol levels followed specific and different patterns, which remained constant for the period studied and allowed the origin of the clams to be distinguished. Stepwise discriminant analysis, based on the percentage amounts of the sterols at each locality, indicated brassicasterol, 22-cis-dehydrocholesterol, cholesterol, 24-norcholestadienol and -sitosterol as discriminant variables that distinguish clam populations. Correct identification of the clam origin was achieved in 100% of the samples, demonstrating that sterols can justifiably be used as molecular biomarkers for determining the origin of this bivalve species.Communicated by O. Kinne, Oldendorf/Luhe     

Reproductive strategies of two deep-sea gastropod species from the Porcupine Seabight (Northeast Atlantic)

Two species of small gastropods (<6 mm in length), Amphissa acutecostata (Philippi, 1844) and Gymnobela subaraneosa (Dautzenberg and Fischer, 1896), widely distributed in the northeast Atlantic, were found in large numbers in the Porcupine Seabight (Northeast Atlantic). Except for some aspects of taxonomy and distribution, as well as some data on larval development, the biology of these species is unknown. This study describes basic aspects of the life-history strategies of both species. Histological studies showed that oocyte and sperm development in both species was similar to the gametogenetic patterns observed in other deep-sea gastropods. In females, oogonia proliferated in the germinal epithelium and developed into previtellogenic oocytes (30–40 m), which grew into vitellogenic primary oocytes. Vitellogenic oocytes were covered by a thin layer of follicle cells involved in the vitellogenic processes. The maximum size for mature oocytes was 99.06 m for A. acutecostata and 114.82 m for G. subaraneosa. In A. acutecostata most of the volume of the ovary was occupied by previtellogenic and early vitellogenic oocytes, whereas in G. subaraneosa most of the volume was filled by large vitellogenic oocytes. Both species showed quasi-continuous production of oocytes. The oocyte size-frequency diagrams suggested a continuous release of a small number of oocytes throughout the year for A. acutecostata, and asynchronous periodic spawning events for G. subaraneosa. Gonad development and gametogenesis could be strongly affected by presence of parasites in one of the populations of G. subaraneosa.Communicated by J.P. Thorpe, Port Erin     

Reproduction and sex reversal of the solitary vermetid gastropod<Emphasis Type="Italic"> Serpulorbis arenarius</Emphasis>

The reproductive biology of the Mediterranean vermetid gastropod Serpulorbis arenarius, a subtidal sessile solitary species that lives in shady rocky communities, was studied at two localities south-east of the Iberian Peninsula. Its population density is usually low, with specimens sometimes sparsely distributed. Its shell often appears to be covered by epibiotic organisms. The sex ratio is biased toward males (63%) in the populations of SE Spain, and the results point towards hermaphroditism with alternating sexuality. The results obtained suggest that all specimens are first males, change to females under some as yet unknown condition and, after the ovogenesis cycle has been completed, revert to the original sexual state (male). The possible adaptive forces that favour hermaphroditism in this species are discussed, and we hypothesise that the seizure of a spermatophore by males may stimulate sex change to female. Brooding females (51% of females studied) were found from March to December. In males, histological study of testes revealed that spermatogenesis seems to occur throughout the year. Females brooded between 5 and 28 (=15) egg capsules, which were attached by stalks to the inner surface of the shell. It is noteworthy that the gonads of two of the specimens brooding egg capsules were developing testes. The newly laid egg capsules were filled with an organic intracapsular matrix, in which 40–153 (=94) eggs were embedded. The mean diameter of the uncleaved ova was 352.5 µm. The organic intracapsular matrix and some nurse eggs were used as an extra-embryonic food source. Hatching occurred at an advanced veliger stage, immediately followed by metamorphosis. Therefore, the larval development of S. arenarius is of a lecithotrophic intracapsular type, with a short, free-swimming/crawling phase.Communicated by O. Kinne, Oldendorf/Luhe