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.     

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.     

Introduced species in seagrass ecosystems: Status and concerns

A literature review revealed that at least 56 non-native species, primarily invertebrates and seaweeds, have been introduced to seagrass beds, largely through shipping/boating activities and aquaculture. Four seagrass species also have been introduced. The introductions of the seaweeds Caulerpa taxifolia, C. racemosa v. cylindracea, Codium fragile ssp. tomentosoides, Sargassum muticum, the Asian mussel, Musculista senhousia, and the seagrass, Zostera japonica, are the best-known examples in seagrass beds. The ecological effects on seagrasses and associated communities have been examined for slightly less than half of the introduced species, which have predominantly negative effects. There is a paucity of experimental data for ecological effects, particularly for seagrass community structure and function. The exception to this finding is the introduction of the seagrass Z. japonica with oyster aquaculture to native eelgrass beds on the Pacific coasts of Canada and the USA. Recent experiments in several different seagrass ecosystems confirmed that disturbance contributes to the invasibility of seagrass beds. More definitive studies are required to elucidate the relative effects of nutrient pollution and introduced species in causing seagrass decline, particularly where reduced herbivory and boating activity also covary. Seagrass beds often are subject to multiple introduced species, but their cumulative effect has been virtually unstudied. The potential for compounded negative effects merits serious attention. Heightened attention to the issue of introduced species in seagrass beds is called for given the evidence that introduced species can contribute to seagrass decline, to biodiversity changes that could affect seagrass ecosystem functions, and that they can compromise seagrass restoration. Comprehensive surveys in seagrass beds, complemented by more stringent experimental and mensurative sampling designs, are needed. In the interim, conserving seagrass density and bed size can offer resistance to introduced species. Managing to prevent the introductions, including restricting transplantations of non-native biota during seagrass restorations, is likely to bear positive benefits for seagrass ecosystems.     

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     

How an invasive alga species (<Emphasis Type="Italic">Caulerpa taxifolia</Emphasis>) induces changes in foraging strategies of the benthivorous fish <Emphasis Type="Italic">Mullus surmuletus</Emphasis> in coastal Mediterranean ecosystems

The foraging behaviour variability of three striped red mullet (Mullus surmuletus L. 1758) populations with respect to the vegetation cover was examined along the French Mediterranean coasts. We tested both the carrying capacity of different habitats and the hypothesis of a food segregation by the invasive alga Caulerpa taxifolia (Vahl) C. Agardh, on the functioning of benthic fish populations. The results indicated a significant site effect on M. surmuletus foraging behaviour and movements. The vegetation cover may play an important role in modifying the striped red mullet cost of foraging (sampling effort) and thus its strategy of prey capture. As long as the cover of marine phanerogams and/or macrophyte algae (Caulerpaceae) increases, the foraging budget and the distances covered in search of prey decrease significantly. Similarly, the striped red mullet increases the prospected sample periods to augment its foraging success, swimming above the bottom. These changes are related to the development of a dense superficial network of plagiotropic rhizomes and stolons, and to the reduction of space between fronds that limits the accessibility to resources and may increase intra-specific food competition. The role of C. taxifolia does not differ from that of other marine phanerogams but induces significant changes in the structure of Mullidae populations at the local level. The rapid expansion of Caulerpaceae in the Mediterranean Sea could constitute a real threat for the balance of the marine coastal biodiversity and the ecology of M. surmuletus, which is considered a flagship species for coastal Mediterranean demersal fisheries.     

Spread of the introduced tropical green alga Caulerpa taxifolia in northern Mediterranean waters

The first report of Caulerpa taxifolia in the Mediterranean is from 1984. The alga was found on the rocky shore at Monaco, below the Oceanographic Museum, where it had been on display in tropical aquaria. Within five years, there was an abundance of C. taxifolia on the shores around the first point of observation. In 1987, C. taxifolia appeared on the French coast, 3 km east of Monaco, at Cap Martin. By late 1991, 30 ha of shore in the vicinity of Monaco was covered with the alga. New points of colonization were in Livorno, Italy, 240 km east of Monaco, and to the west at Agay, Le Lavandou, Hyères, Toulon, Les Lecques, Saint Cyprien, 50 to 370 km from Monaco. The westernmost point of colonization, noted in September 1992, was 600 km from Monaco, at Majorca (Balearic island, Spain). Most types of substrata, between 0 and 50 m depth, are susceptible to colonization by C. taxifolia. Seaweed and seagrass populations on the coasts of Monaco and Cap Martin have been significantly reduced or destroyed because of invasion by C. taxifolia.     

MEDITERRANEAN CAULERPA TAXIFOLIA AND C. MEXICANA (CHLOROPHYTA) ARE NOT CONSPECIFIC

In 1984, Caulerpa taxifolia (Vahl) C. Agardh was reported along the coast of Monaco. Over the past decade it has spread along 60 km of the Mediterranean coastline and presently represents a potential risk to biodiversity. Several explanations have been advanced regarding the presence of C. taxifolia in the Mediterranean. One hypothesis maintains that the alga was introduced accidentally into the sea at Monaco, where it has been used as a decorative alga in aquaria. Caulerpa taxifolia has not been reported in earlier marine floras of the Mediterranean, and its sudden appearance has suggested that it may be a recent introduction. Another hypothesis proposes that C. taxifolia and Caulerpa mexicana Sonder ex Kützing are morphological variants of one another and hence conspecific taxa. Caulerpa mexicana has been found in the eastern Mediterranean since at least 1941. In order to establish the taxonomic identities of these taxa, individuals from five populations of C. taxifolia and four populations of C. mexicana were collected from within and outside of the Mediterranean. Comparative DNA sequence analysis of the nuclear ribosomal cistron, including the 3′-end of the 18S, ITS1, 5.8S, and ITS2 regions, show clear phylogenetic separation of the two taxa using parsimony and maximum likelihood analyses. Separation is maintained whether the analyses are based on just the more conserved 18S data or just the fast- evolving spacers. The two species are thus not conspecific. For specimens of uncertain identity (i.e. taxifolia–mexicana intermediates), a PCR diagnostic amplification can easily be performed because the ITS1 in C. taxifolia is 36 nucleotides shorter than the ITS1 in C. mexicana. Whether or not C. taxifolia has been present for a longer period of time in the marine flora, either as a cryptic endemic species or as the result of one or more introductions, represents an additional hypothesis that will require identification of biogeographic populations from throughout the world, as well as a population-level study of the Mediterranean region.     

POPULATION GENETICS AND TAXONOMY OF CAULERPA (CHLOROPHYTA) FROM THE GREAT BARRIER REEF,AUSTRALIA1

Allozyme variation was examined in seven species and four varieties of Caulerpa sampled from the Great Barrier Reef (GBR) region, Australia. Differences between species were greater than those between populations of the same taxon sampled from different geographical locations, and typically included fixed gene differences (no alleles found in one taxon shared by the other taxon) at two or more loci. Three varieties of C. racemosa, vars imbricata, laetevirens, and racemosa, and a peltate morph of C. racemosa were as strongly distinguished genetically as the six other species examined: C. cupressoides, C. lentillifera, C. peltata, C. serrulata, C. sertularioides, and C. taxifolia. Cluster analysis did not place all of the C. racemosa varieties together and linked them with other species, but cladistic analyses showed the allozyme data gave little useful phylogenetic information. Eight of 13 plants identified initially as C. serrulata were distinguished at several loci, indicating the presence of an undetermined cryptic taxon. Population genetic analysis of polymorphism, which occurred in some taxa, demonstrated strong spatial differentiation among populations of C. cupressoides, C. racemosa vars laetevirens and racemosa, C. serrulata, and C. taxifolia and significant but variable degrees of clonality and/or inbreeding within these populations. Allozymes proved to be a useful tool for defining species boundaries and investigating population structure in Caulerpa, but not for determining phylogenetic relationships within the genus.     

ALGAL CALCIFICATION IN SOME CODIACEAE (CHLOROPHYTA): ULTRASTRUCTURE AND LOCATION OF SKELETAL DEPOSITS1,2

The capitular filaments of Penicillus and Rhipocephalus consist of an inner tube containing the cytoplasm and an outer calcified sheath. The sheath originates at the cell wall and differentiates into several layers which form the outer filament wall. CaCO₃ is deposited between organic layers within the sheath and is not in direct contact with the seawater. Pores within the sheath, usually uncalcified, may facilitate exchange of gases and solutes. The cytoplasm is characterized by vacuolar inclusions of calcium oxalate needles 50–150 μm long. A closed cortical surface is lacking. Udotea cyathiformis Dec. and U. conglutinata (Ellis & Sol.) Lam. are similar to Penicillus and Rhipocephalus, in addition showing some CaCO₃ between filaments (ICS-calcification). Udotea flabellum (Ellis & Sol.) Lam. is different as the filaments are profusely branched giving rise to a fully developed cortical surface. Pores and vacuolar calcium oxalate inclusions are absent. CaCO₃ deposition occurs within cortical filaments in between layers of the filament wall and subcortically in intercellular spares (ICS). Cortex calcification shows primary and secondary deposits bearing some resemblance to sheath calcification and to coralline red algae. In Rhipocephalus phoenix (Ellis & Sol.) Kütz., Penicillus pyriformis A. &E. Gepp, U. cyathiformis and U. conglutinata CaCO₃ is precipitated intracellularly within the sheath, in contrast to Halimeda and Cymopolia where it is deposited extracellularly in between filaments. U. flabellum takes an intermediate position showing both intra- and intercellular calcification. The sheath compartment volume is between 12.5 and 7500 μm³and 5–3 orders of magnitude smaller than the ICS-compartment. Compartment size and location of CaCO₃may bear on calcification mechanisms. One condition for such a mechanism may be restricted exchange of solutes (CO₂, CO₃^2-, HCO₃^-, O₂, Co²⁺). Codiaceae; filament ultrastructure; Penicillus; Rhipocephalus; Udotea     

TOXICITY OF SUBTROPICAL MARINE ALGAE USING FISH MORTALITY AND RED BLOOD CELL HEMOLYSIS FOR BIOASSAYS1

Two bioassays (fish mortality and fish erythrocyte hemolysis) were used to survey for the presence of toxic principles in aqueous extracts of 19 species of marine macro-algae found in south Florida coastal waters. Extracts from six species (Chlorophyta—Anadyomene stellata (Wulfen) C. Ag., Caulerpa prolifera (Forsskål) Lamour., Penicillus capitatus Lamarck: Rhodophyta—Centroceras clavulatum (C. Ag.) Montague, Laurencia papillosa (Forsskål) Grev., L. poitel (Lamour.) Howe) showed lethal toxicity to the spotfin mojarra, Euconistomus argenteus Baird & Girard. Extracts from three species (Chlorophyta—A. stellata: Phaeophyta—Dictyota dichotoma (Hudson) Lamour.: Rhodophyta—Wrangelia penicillata C. Ag.) lysed erythrocytes of sea bream, Archosargus rhomboidalis (L.).