PEROXIDASE IN CAULERPA1

A survey of 17 species of Caulerpa showed peroxidase activity to be widespread in this genus. The intracellular location of the activity varied in different species, but only in C. cliftoni Harvey was it associated with wound plugs. In eight species peroxidase activity was present in the branching points of the trabeculae and in 12 of the 17 species it was found in the cell wall or in the trabeculae adjacent to the cell wall. Peroxidase was isolated from one species, C. simpliciuscula C. Ag., and some of its properties examined. Two isoenzymes were present, both of them different from the peroxidase isolated from Batophora oerstedii J. Agardh and Cymopolia barbata L.     

High Nitrogen and Phosphorous Acquisition by Belowground Parts of Caulerpa prolifera (Chlorophyta) Contribute to the Species' Rapid Spread in Ria Formosa Lagoon,Southern Portugal

Despite worldwide proliferation of the genus Caulerpa and subsequent effects on benthic communities, little is known about the nutritional physiology of the Caulerpales. Here, we investigated the uptake rates of ammonium, nitrate, amino acids, and phosphate through the fronds and rhizoids + stolon, the internal translocation of nitrogen, and developed a nitrogen budget for the rapidly spreading Caulerpa prolifera in Ria Formosa lagoon, southern Portugal. Caulerpa prolifera acquired nutrients by both aboveground and belowground parts at similar rates, except nitrate, for which fronds showed 2-fold higher uptake rates. Ammonium was the preferential nitrogen source (81% of the total nitrogen acquisition), and amino acids, which accounted for a significant fraction of total N acquisition (19%), were taken up at faster rates than nitrate. Basipetal translocation of ¹⁵N incorporated as ammonium was nearly 3-fold higher than acropetal translocation, whereas ¹⁵N translocation as nitrate and amino acids was smaller but equal in either direction. The estimated total nitrogen acquisition by C. prolifera was 689 μmol · m⁻² · h⁻¹, whereas the total nitrogen requirement for growth was 672 μmol · m⁻² · h⁻¹. The uptake of ammonium and amino acids by belowground parts accounted for the larger fraction of the total nitrogen acquisition of C. prolifera and is sufficient to satisfy the species nitrogen requirements for growth. This may be one reason explaining the fast spreading of the seaweed in the bare sediments of Ria Formosa where it does not have any macrophyte competitors and the concentration of nutrients is high.     

Culture studies onCaulerpa (caulerpales,chlorophyceae) III. Reproduction,development and morphological variation of laboratory-culturedC. racemosa var.peltata

Reproduction, development and morphological variation of the marine green algaCaulerpa racemosa var.peltata from the southern part of Japan were studied in culture in the laboratory. Anisogamous biflagellate male and female gametes were produced monoeciously and copulated with each other. Settled zygotes became spherical and increased in volume. After five weeks, they formed two germ tubes which extended in opposite directions. Both germ tubes became elongated and branched, resulting in the formation of creeping, filamentous, protonema-like plants. These plants formed primary shoots which differentiated into creeping rhizomes and upright axes. Each upright axis successively formed ramuli and developed into an assimilator. The morphology of assimilators, i.e., shape and arrangement of ramuli, varied with culture coditions. The effects of temperature and light intensity on the formation of assimilators were investigated with 25 combinations of 5 temperatures (20.0–30.0C) and 5 light intensities (0.5–8.0 klux). The morphological plasticity of this alga is identical to that ofCaulerpa racemosa var.laetevirens, which was previously described by the present authors. Thus, apparently, the plasticity of this taxon is correlated with environmental factors. It appears, moreover, thatC. racemosa var.peltata andC. racemosa var.laetevirens are ecophenes (ecads) of a single species.     

Oral Passive Immunization Effect of Anti-Human Rotavirus IgY and Its Behavior against Proteolytic Enzymes

The neutralization titer of anti-human rotavirus (HRV) IgY was completely inactivated by pepsin at pH 2.0. However, it was not significantly affected by trypsin or chymotrypsin under certain conditions. The immunological activity of the IgY was observed in the intestine of suckling mice for 2 h after oral administration and the activity rapidly decreased thereafter. The effects of oral supply of IgY were thus estimated for HRV-induced diarrhea in suckling mice and it was found that a previous supply of the IgY, (1 h before HRV infection) completely prevented the HRV-induced diarrhea. The preventive effect was decreased as the time gap between IgY administration and HRV infection was longer. However, the oral supply of the IgY within 24h after HRV infection was still effective and decreased the incidence of HRV diarrhea in suckling mice.     

Spectral Changes of the γ-Irradiated Glucose Solution

β-1,3-Xylanase was purified to gel electrophoretic homogeneity and 83-fold from a cell-free culture fluid of Vibrio sp. XY-214 by ammonium sulfate precipitation and successive chromatographies. The enzyme had a pl of 3.6 and a molecular mass of 52 kDa. The enzyme had the highest level of activity at pH 7.0 and 37°C. The enzyme activity was completely inhibited by Cu²⁺, Hg²⁺, and N-bromosuccinimide. The enzyme hydrolyzed β-1,3-xylan to produce mainly xylotriose and xylobiose but did not act on xylobiose, p-nitrophenyl-β-D-xyloside, β-1,4-xylan, β-1,3-glucan, or carboxymethyl cellulose.     

Fragility of Erythrocytes from Chicks and Rats Fed Dilauryl Succinate and Related Compounds

Susceptibility to hydrogen peroxide of the erythrocytes from chicks and rats fed dilauryl succinate and related compounds with and without supplementation of dl-α-tocopheryl acetate was determined.

Dilauryl succinate, lauryl alcohol, n-decyI alcohol, myristyl alcohol, and lauraldehyde were confirmed to make the erythrocytes from the chicks fragile. Supplemented dl-α-tocopheryl acetate of 200 mg per kg of diet completely prevented the hemolysis induced by these compounds. Dilauryl succinate also makes the rat’s erythrocytes fragile and supplemented dl-α-tocopheryl acetate prevented the hemolysis of the rats, but ethoxyquin was not. The symptoms of encephalomalacia in the chick is preceded by increased hemolysis value of the erythrocytes, and this hemolysis value dropped after the appearance of encephalomalacia.     

Production of rhizoids by Caulerpa prolifera in culture

Studies on Caulerpa prolifera rhizoids were carried out to determine the possibility of mass culture, because the rhizoids produce a bio-adhesive. Rhizoids can be induced by cutting the base of a blade and floating it in a media or planting it in sand. Measurement of rhizoid production included determination of number, length, and the weight of attached sand grains. The growth experiments were for 1–2 weeks and fronds growth was compared to rhizoid production. Optimal conditions for rhizoid growth included low levels of nitrogen and phosphate (less than 5 and 2 μM, respectively), low irradiance (30 μmol photon m⁻² s⁻¹), moderate temperature (22–28°), continuous shaking, addition of microelements and auxin (1 ppm) and initially detached fronds followed by attachment. Under these optimal conditions maximal weekly growth reached 70–170 rhizoids per blade, 7–11 mm length and maximal attachment to sand grains. Blade growth of C. prolifera responded similarly to rhizoid production and reached a weekly growth rate of 30–130%.     

Invasion of alien macroalgae in different Mediterranean habitats

The study evaluated different macroalgal invasions in the main Mediterranean coastal habitats on hard bottom. Biodiversity, species composition and structure of macroalgal assemblages were compared among non-invaded areas and areas invaded by the Chlorophyta Caulerpa racemosa var. cylindracea and by the turf-forming Rhodophyta Womersleyella setacea in three different habitats: shallow rocky bottom, deep rocky bottom and dead matte of the seagrass Posidonia oceanica. Results showed that alien macroalgae constituted a relevant component of benthic assemblages in invaded areas of the Mediterranean Sea. Assemblages invaded by Womersleyella setacea and Caulerpa racemosa showed lower values of diversity and large differences in the structure and species composition related to non-nvaded assemblages. The species that mostly suffered from invasion were erect species reproducing sexually; moreover, the dominance of W. setacea led to low abundance of native filamentous algae, while C. racemosa colonization seemed particularly threatening for encrusting algae. All the studied habitats appeared highly invasible by alien macroalgae, even if W. setacea appeared more invasive in deeper habitats, while colonization of C. racemosa seemed more serious in shallower habitats; the dead matte of P. oceanica represented a suitable substrate for the spread of both species. Differences among assemblages in different habitats were reduced in invaded areas.     

Grazing rates of Elysia tomentosa on native and introduced Caulerpa taxifolia

The marine alga Caulerpa taxifolia Vahl (C. Agardh), recognized globally as one of the most prolific non-native species introductions, has been introduced to several temperate locations from where it has since rapidly expanded. C. taxifolia is protected by a toxin (terpenoid) in its tissues that limits grazing by native herbivores. Sacoglossan molluscs of the genus Elysia are among the few organisms that graze C. taxifolia; however, little is known about their feeding ecology. In the current study, we quantified the grazing rates of Elysia tomentosa on native C. taxifolia (Moreton Bay, Queensland) and introduced C. taxifolia (Botany Bay and Lake Conjola, New South Wales). Grazing rates were similar at Moreton Bay sites and Botany Bay; however, they were significantly lower in Lake Conjola. At the maximum observed grazing rate, slugs ate their body weight in C. taxifolia (dry weight) every 18–24 h. Differences in grazing rates between locations may be explained by differences in C. taxifolia morphology rather than native or introduced origin. Handling editor: J. Padisak     

Modeling the Increase and Control of Caulerpa taxifolia, an Invasive Marine Macroalga

Population modeling based on species’ demography makes it possible to predict the pace of an invasion and evaluate the likelihood of success of different control strategies. We modeled the initial (density-independent) rate of increase of Caulerpa taxifolia (Vahl) C. Agardh (aquarium strain), a green alga that has markedly altered marine communities where it has invaded in the Mediterranean Sea. Parameter values for patch growth (from stolon extension) and reproduction (by asexual fragmentation and reattachment) were gleaned from published studies. Only the most conservative model, invoking field growth rates and low levels of fragment reattachment (2.5 m⁻² of existing patch each summer), closely matched observed increases (4–14 × annually). The most effective times for control (greatest reduction in rate of increase) were removal of established patches before summer and removal of fragments after summer. These times correspond to just before maximum growth and just after maximum reproduction, respectively. Only a combined strategy, incorporating 99% removal of all fragments and annual removal of 99% of established patches, was predicted to eliminate C. taxifolia entirely (λ < 1). This level of effort is only likely to be possible during the first few years of an invasion, arguing strongly for careful monitoring and rapid response to potential high-impact invaders.