IN SITU UPTAKE KINETICS OF AMMONIUM AND PHOSPHATE AND CHEMICAL COMPOSITION OF THE RED SEAWEED GRACILARIA TIKVAHIAE1

The uptake kinetics of ammonium and phosphate by Gracilaria tikvahiae McLachlan were studied under field conditions. Seaweeds, pulse fed once a week for 6 h over a 4-week period, had maximum uptake rates of 19 μmol·g fwt^?1·h^?1 for ammonium and 0.28 μmol·g fwt^?1·h^?1 for phosphate. For both nutrients there was a positive linear correlation between uptake rate (v) and concentration (S) over the entire range of concentration tested. In a nutrient depletion experiment, the phosphate uptake curve determined over a wide range of concentrations consisted of two stages of saturation at low concentrations, and a linear phase at high concentrations. Ash free dry weight, chlorophyll a, phycoerythrin, and protein content were higher in pulse fed plants than in control plants receiving no nutrient additions, while the reverse held true for carbohydrate contents and the C/N ratios. The C/N ratio inversely correlated with ammonium and phosphate uptake rate as well as protein and phycoerythrin content, and positively with carbohydrate content.     

Responses of Spotted Hyenas to Lions Reflect Individual Differences in Behavior

Competition among mammalian carnivores can be particularly intense and can influence population dynamics at lower trophic levels. One strategy employed by carnivores to minimize potentially costly interspecific competition is avoidance of dominant species. Recent research has highlighted the importance of consistent individual differences in behavior (i.e. temperament traits) in understanding behavioral variation during predator–prey interactions and intraspecific interactions. However, the importance of such individual differences to interspecific competition has received little attention. Here, we examined the responses of spotted hyenas (Crocuta crocuta) to their primary competitors, African lions (Panthera leo), to (1) determine whether hyenas avoid lions and (2) evaluate the potential importance of individual differences in behavior during interspecific competition. Spotted hyenas and lions co‐occur throughout much of Africa and are vigorous competitors. Whereas lions sometimes kill hyenas and steal their food, lions also represent a source of food for hyenas via scavenging. Using audio playback experiments, we found that hyenas do not uniformly avoid potential encounters with lions. Indeed, we noted considerable variation among individuals in their responses to lion roars, and this variation reflected consistent individual differences in risk‐taking and vigilance tendencies. Individual differences in vigilance behavior were specific to interactions with lions. We conclude that individual differences in behavior have the potential to play an important role in determining the nature and outcome of interspecific competition.     

Branch,micropropagule and tissue culture of the red algaeEucheuma denticulatum andKappaphycus alvarezii farmed in the Philippines

Three forms of the iota-producing carrageenophyte,Eucheuma denticulatum, and four forms of the kappa-producing carrageenophyte,Kappaphycus alvarezii, obtained from seaweed farms in the Philippines have been grown in the laboratory under unialgal and axenic conditions. Comparison of media indicates that seed stocks of both species can be cultured using enriched seawater media ranging from ESS and SWMD-1 to inexpensive soil extract (Erdshreiber's) or holding in sterile seawater for up to three weeks. Micropropagation has been successful with at least two forms of each species resulting in clonal propagation from axenic explants within 4 to 8 weeks. Callus development and branch regeneration has also been induced in two forms of each species. The results indicate that culture facilities in the farming areas of the Philippines could maintain high-yielding and rapidly growing seed stock for the seaweed farmers.     

Suspended cultivation of Gracilaria in the sea

Suspended rope cultivation systems for Gracilaria or Gracilariopsis can be seeded from spores but vegetative propagation is used for those which are currently commercially successful. Such systems and methods have been recently developed for the shallow lagoon areas around Lüderitz, Namibia and deeper open water sites off the Araya Peninsula, Venezuela. Various sites, substrata, depths and seeding methods have been assessed and have resulted in average commercial growth rates of about 3.5% per day. Netlon ‘Superope’ has been demonstrated to be more suitable than laid rope as a substratum for outplanted vegetative Gracilaria gracilis in Namibia as it does not compress the thalli as they grow. An efficient method, using hooks, has been developed to ‘seed’ the Superope. There is a very low incidence of algal epiphytism: mainly Ceramium and Ulva sp. In Venezuela, pilot rope cultivation systems for Gracilariopsis tenuifrons proved successful and have good commercial prospects.     

Bacterial Characteristics Determining the Potential Host Range of Bacteriophage T4

Many members of the Enterobacteriaceae, but not other gram-negative organisms, apparently carry a specific recognition site for the T4 tail tube on their cytoplasmic membranes.