Search

The external peripheral termini of vasculature in botryllid ascidians (ampullae) are important in the expression of effector mechanisms during histocompatibility reactions. We study here morphological changes to the microstructure during allorecognition in Botrylloides subpopulation I (SP1) from the Mediterranean coast of Israel, where special giant ampullae, called megaloampullae are developed hours after first allogeneic challenge. The basal part of each naive ampulla consists of a sheath of continuous squamous epithelial cells (1 μm×20 μm). At the tip of the ampullae, about 130 epithelial cells become columnar with wide apical pads (15 μm×5–10 μm), that contain electron-opaque “adhesive vesicles”. Foci of crystallizations were observed within the vesicles of some columnar cells. Ampullar epithelial cells develop internal folds that support tight attachments between circulating blood cells (most of them are pigment cells) and ampullar epithelium. During the histoincompatibility process, the tunic peripheral edge at the interaction area becomes highly convoluted. Filaments (up to 1.16 μm) accumulate in the interaction tunic matrix. Some of these filaments encircle destructed cells. Fragmented cell membranes are also found next to the reacting ampullae. The most characteristic feature of the Botrylloides SP1 rejection reaction is dilation of the ampullae. The ampullar epithelium becomes “curly” when megaloampullae are formed. Within the curly region, about 30% of the squamous epithelial cells are further stretched, up to 33 μm in length. Some additional mechanisms are suggested to explain the fast increase (up to seven times) in ampullar width that is recorded within a few hours from the first allogeneic contact. [ABSTRACT FROM AUTHOR]

Abstract Recreational and other human activities degrade coral reefs worldwide to a point where efficient restoration techniques are needed. Here we tested several strategies for gardening denuded reefs. The gardening concept consists of in situ or ex situ mariculture of coral recruits, followed by their transplantation into degraded reef sites. In situ nurseries were established in Eilat's (Northern Red Sea) shallow waters, sheltering three types of coral materials taken from the branching species Stylophora pistillata (small colonies, branch fragments, and spat) that were monitored for up to two years. Pruning more than 10% of donor colonies' branches increased mortality, and surviving colonies displayed reduced reproductive activity. Maricultured isolated branches, however, exceeded donor colony life span and reproductive activity and added 0.5–45% skeletal mass per year. Forty-four percent of the small colonies survived after 1.5-year mariculture, revealing average yearly growth of 75 ± 32%. Three months ex situ maintenance of coral spat (sexual recruits) prior to the in situ nursery phase increased survivorship. Within the next 1.5 years, they developed into colonies of 3–4 cm diameter. Nursery periods of 2 years, 4–5 years, and more than> 5 years have been estimated for small colonies, spat, and isolated branches, respectively. These and other results, including the possible use of nubbins (minute fragments the size of a single or few polyps), are discussed, revealing benefits and drawbacks for each material. In situ coral mariculture is an improved practice to the common but potentially harmful protocol of direct coral transplantation. It is suggested that reef gardening may be used as a key management tool in conservation and restoration of denuded reef areas. The gardening concept may be applicable for coral reefs worldwide through site-specific considerations and the use of different local coral species. [ABSTRACT FROM AUTHOR]

Examines the ecological and life history characteristics of Botryllus schlosseri ascidian populations along the Israeli Mediterranean coast. Correlation of colony numbers with mean seawater temperatures; Dominance of the brown morph at all studied localities; Evidence of subpopulations exhibiting microgeographic differences.

The role of autotrophic nutrition in the production of coral planula was investigated in two field experiments carried out in Eilat, the Red Sea during 1980 and 1981, on the branching coral, Stylophora pistillata. Photosynthetically fixed carbon in coral tissue significantly decreased during planulation compared to the non-reproductive season. Planula-larvae collected 1 to 7 mo after coral tissue was labelled with C contained significant amounts of C-labelled photosynthates. The results provide the first direct evidence that energy requirements for planula production in a hermatypic coral are supported by translocation of products from algal photosynthesis. It is suggested that this is also the case in other hermatypic species. [ABSTRACT FROM AUTHOR]

The article focuses on the outbreak of corallivorous snail Drupella cornus at coral colonies in the northern Gulf of Eilat, Israel. It relates that between 1999 and 2000, large numbers of the snail appeared following coral mortality. It notes that in the subsequent years, the number of snails increased dramatically, in which more than 200 Drupella on each 30-centimeter (cm) diameter colony of several branching coral species were found. It was noted that all coral colonies of the quay died within 2 years. It was also observed that at first, the Drupella fed only on branching coral species, but as these were killed, the snails were found on massive and encrusting species of corals, including Turbinaria mesenterina and Pavona cactus.

Based on mtCOI sequences comparisons, recent studies reassigned the 'dwarf Botrylloides leachii' from the Levant as Botrylloides nigrum. Here we conducted a survey of the literature and of deposited mtCOI sequences of botryllid ascidians, elucidating ambiguities in their taxonomy. We found that the species, dwarf morph of Botrylloides leachii, Botrylloides nigrum, Botryllus aster and Botryllus arenaceus are grouped together on a single molecular taxon. Then, results of three additional markers (18S, 28S, H3) contradicted literature suggestions, revealing minute distances between Botrylloides leachii and the 'dwarf Botrylloides leachii'. Moreover, only Botrylloides leachii and the 'dwarf Botrylloides leachii' develop giant ampullae as an allorecognition response. Our results raise the possibility that inadequate identification, together with faults in molecular assignment, including queries regarding the efficacy of the mtCOI as the exclusive barcoding tool in botryllid ascidians, is the major culprits responsible for the emerged inconsistencies between the mtCOI sequences and traditional taxonomy. Thus, we assign the Levantine dwarf form as Botrylloides aff. leachii.

Phenotypic plasticity enables multicellular organisms to adjust morphologies and various life history traits to variable environmental challenges. Here, we elucidate fixed and plastic architectural rules for colony astogeny in multiple types of colonial ramets, propagated by cutting from genets of the branching coral Stylophora pistillata from Eilat, the Red Sea. We examined 16 morphometric parameters on 136 one-year old S. pistillata colonies (of seven genotypes), originating from small fragments belonging, each, to one of three single-branch types (single tips, start-up, and advanced bifurcating tips) or to structural preparative manipulations (representing a single or two growth axes). Experiments were guided by the rationale that in colonial forms, complexity of evolving phenotypic plasticity can be associated with a degree of structural modularity, where shapes are approached by erecting iterative growth patterns at different levels of coral-colony organization. Analyses revealed plastic morphometric characters at branch level, and predetermined morphometric traits at colony level (only single trait exhibited plasticity under extreme manipulation state). Therefore, under the experimental manipulations of this study, phenotypic plasticity in S. pistillata appears to be related to branch level of organization, whereas colony traits are controlled by predetermined genetic architectural rules. Each level of organization undergoes its own mode of astogeny. However, depending on the original ramet structure, the spherical 3-D colonial architecture in this species is orchestrated and assembled by both developmental trajectories at the branch level, and traits at the colony level of organization. In nature, branching colonial forms are often subjected to harsh environmental conditions that cause fragmentation of colony into ramets of different sizes and structures. Developmental traits that are plastic, responding to fragment structure and are not predetermine in controlling astogeny, allow formation of species-specific architecture product through integrated but variable developmental routes. This adaptive plasticity or regeneration is an efficient mechanism by which isolated fragments of branching coral species cope with external environmental forces.

This study evaluates water genotoxicity of the Kishon River, the most polluted river in Israel that is under restoration. Water samples were collected every other month (January 2001-May 2003) from five sites, and genotoxicity was assayed by the alkaline comet assay using a fish hepatoma cell line (RTH-149). Genotoxicity in the Kishon River was reduced during 2002 as compared to the previous year. The results further revealed fluctuations in genotoxicity levels at all sites throughout the studied period with variations for the same month during consecutive years and seasonality. In general, summer samples were more genotoxic than winter samples. In the vast majority of the 75 water samples, all four parameters for genotoxicity that were employed revealed significant higher genotoxic levels than the controls. Comet percentage values in Kishon River samples were, on average, 1.8-2.4 times higher than controls. Damage score, comet tail length, and cumulative tail length values were 2.2-3.1, 2.4-3.7, and 2.4-3.7 times higher than controls, respectively. The Histadrut Bridge and Haifa fishing harbor (3.0 m depth) emerged as the most polluted sites, whereas Kiryat Haroshet was the least contaminated. Results call for a long-term genotoxicity follow-up plan at the Kishon River in order to assess the possibly evolving chronic genotoxicity state.

Hepatic cytochrome P4501A (CYP1A) expression was partially characterized in the striped sea bream (Lithognathus mormyrus) from the Mediterranean coast of Israel as part of the process of establishing the CYP1A gene as an environmental biomarker. Reverse transcription-competitive polymerase chain reaction, competitive enzyme-linked immunosorbent assay, and ethoxyresorufin O-deethylase (EROD) assay were used for evaluating transcript, protein, and catalytic activity levels, respectively, in absolute units. Highest elucidated transcript, protein, and catalytic activity levels were 0.264 +/- SD 0.084 fmol/microg total RNA, 0.88 +/- 0.52 pmol/microg total protein, and 1.11 +/- 0.52 pmol resorufin/min/microg total protein, respectively, and the lower levels were 0.009 +/- 0.007 fmol/microg total RNA, 0.17 +/- 0.08 pmol/microg total protein, and 0.11 +/- 0.06 pmol resorufin/min/microg total protein, respectively, demonstrating substantial induction potential. All alternate pairs of seven examined field samples, revealing a transcript-level ratio higher than 1.7, also demonstrated a significant difference between their transcript levels, indicating a potential to detect relatively small biomarker changes (1.7-fold) caused by environmental effects. Simultaneous triple measurements of transcript, protein, and catalytic activity were carried out in individuals from two field samples and during a 318-d decay experiment. Fish from the field samples revealed significant alternate bivariate correlation between transcript, protein, and enzymatic activity. Conflicting results were found when analyzing the decay experiment, in which both protein and catalytic activity levels decreased significantly to basal levels, in contrast to no significant change in transcript levels throughout the experiment. No significant difference was observed between males and females regarding the levels of CYP1A transcript, protein, and EROD.

The alkaline comet assay, a sensitive method for DNA strand breaks and alkali labile site detection in individual cells, was employed here as an ecotoxicological monitoring tool for evaluation of genotoxicity in the Kishon River, Israel. This river, the most polluted river in Israel, has recently elicited major public concern with regard to cancer incidences in people who have dived there over many years. Five water samples were collected every odd month throughout the year 2001, from four localities. The comet assay was employed on fish hepatoma cell line RTH-149. Cells were exposed for 2h, in triplicate, to Kishon water: medium (1:1) samples that were pre-adjusted for pH and salinity percentage levels. Three DNA damage parameters (comet percentages, score of damage, and cumulative tail lengths of the comet), revealed significantly higher genotoxic values in Kishon water-treated cells as compared with the controls (up to 2.4, 3.2, and 3.6-fold, respectively). Part of the sampling sites revealed higher genotoxicity than other polluted sites. The results of this study demonstrate that the comet assay with RTH-149 cells can be successfully applied to a variety of aquatic samples revealing freshwater, marine and estuary conditions. The method found to be fast, sensitive, and suitable for monitoring programs.

The comet assay, one of the most widely used techniques for the evaluation and detection of DNA strand breaks, is frequently employed in vivo. In vitro assays are usually performed with mammalian cell lines, clearly not the best choice for tests on aquatic genotoxicity. Here we evaluated a fish hepatoma cell line (RTH-149) and a primary blood cell culture from the intertidal colonial tunicate Botryllus schlosseri as possible model targets for comet assays using the genotoxic agent H2O2. We found that DNA strand break levels in RTH-149 fitted dose-dependent responses better than the tunicate cells. Moreover, in B. schlosseri controls, 34% of the cells were already ranked as severely damaged. Assays were then performed on water samples from the polluted Kishon river (Israel) on three different dates, using RTH-149 cells (50% dilutions, 2-h exposures). In all cases, high genotoxicity of the river water was revealed by evaluating comet percentages, average tail lengths and DNA damage levels. This assay was found to be fast and sensitive, appropriate to be employed as a part of a monitoring program. The use of B. schlosseri blood cells should be validated in additional work.

Some of the characteristics of allogeneic resorption have been revealed in studies of chimeras of two Botrylloides subpopulations (SP1 and SP3) inhabiting the Mediterranean coast of Israel. Both Botrylloides SPs exhibited the same outcomes, which differ significantly from the resorption documented in the well-studied botryllid ascidian, Botryllus schlosseri: 1. Resorption in Botrylloides chimeras was usually a very fast process starting 1 to 26 days after fusion and terminating in < 9 days thereafter. 2. Resorption occurs at any blastogenic stage. 3. Resorption is complete, including zooids, buds, blood vessels and ampullae. 4. Either one of the genotypes can be resorbed in multipair chimeras of any specific combination. 5. Resorption starts simultaneously in all zooids of the partner to be resorbed. 6. Time for resorption and directionality were not affected by the size ratios between the partners (0.3-1.8). As in B. schlosseri, other phenomena (disconnection, chimeric death and retreat growth) interrupt resorption in ca. 60% of the chimeras, under laboratory conditions. We propose that external stress conditions also have a significant role in a nonimmunological expression of resorption in Botrylloides.