Settlement preferences in coral-reef fishes: Effects on patterns of adult and juvenile distributions,individual fitness and population structure

Abstract Coral-reef fishes exhibit a wide range of habitat preferences at settlement. However, the consequences of these preferences to fitness and population dynamics are poorly known. We critically evaluate evidence for these consequences from recent studies of settlement preferences, and note that most studies have concentrated on only a few common taxa. We recommend that this taxonomic base be broadened, and that settlement preferences be incorporated into future studies of the link between larval supply and population dynamics of reef fishes.     

DEVELOPMENT OF ACCESSORY SEXUAL ORGANS IN BIOMPHALARIA GLABRATA (PLANORBIDAE) IN RELATION TO TIMING OF INFECTION BY SCHISTOSOMA MANSONI: CONSEQUENCES FOR ENERGY UTILIZATION PATTERNS BY THE PARASITE

The growth rates of ovotestis and individual accessory sexualorgans (ASO) of Biomphalaria glabrata snails were studied forcontrols and for immature and mature snails infected with Schistosomamansoni. The infection of immature B. glabrata strongly delaysgrowth of the ovotestis and inhibits the development of theaccessory sexual organs. There is no significant differenceup to 2 weeks post infection in the volume of the ovotestisand the ASO between mature infected B. glabrata and controlsnails. From 3 to 4 weeks post infection there was a reductionin the volume of the ovotestis and the ASO of infected matureB. glabrata; then growth of the ovotestis, albumen gland andfemale organs was stopped, but the effect of infection was lessconsistent for the male organs. For a parasite, immature andmature snails have to be considered as two different resourceenvironments, each having at infection time a particular patternof resource allocation, towards growth for juvenile and towardsreproduction for adult snails, changing the possible energyutilization patterns which can be used by the trematode. (Received 29 January 1993; accepted 22 April 1993)     

Rubisco Content and Specific Activity in Barley (Hordeum vulgare L.): I. GENETIC VARIABILITY

Seven barley varieties, differing widely in their geographicorigin, were analysed at the seedling stage under controlledconditions for the following traits: (A) Soluble leaf proteincontent, (B) Rubisco content, (C) Total carboxylase activity,as well as for combinations of these basic characteristics:relative Rubisco concentration, relative carboxylase activity,and specific carboxylase activity of the enzyme. A very large genotypic variability was detected in all traits,especially for the total activity of Rubisco, with strong genotypiccorrelations between these traits, whereas environmental correlationswere almost non-existent. There were also relatively good correlationswith the gross assimilation rate (Pg) among the same range ofvarieties, measured in the adult stage in a previous investigation.For two out of five crosses analysed in the F₁ generation, significantdifferences were found between reciprocal hybrids. These results are discussed in terms of heredity patterns ofthe characteristics concerned, namely the double genetic determinismof Rubisco: a large subunit controlled by maternally inheritedchloroplast DNA and a small subunit controlled by nuclear DNA. Key words: Rubisco, barley, genetic variability, maternal inheritance