Yehuda Benayahu

Hemiasterlin and geodiamolide TA ; two new cytotoxic peptides from the marine sponge hemiasterella minor (Kirkpatrick)

Three cytotoxic peptides, Jaspamide (1) and the two new peptides hemiasterlin (2) and geodiamolide TA (3), have been isolated from the sponge Hemiasterella minor. The structures of the three were determined by interpretating the NMR and mass spectra. Hemiasterlin (2) is a novel linear tripeptide embodying two unique, new natural aminoacids and geodiamolide TA (3) is a higher homologe of geodiamolides A–F.

Limitations of Mitochondrial Gene Barcoding in Octocorallia

The widespread assumption that COI and other mitochondrial genes will be ineffective DNA barcodes for anthozoan cnidarians has not been well tested for most anthozoans other than scleractinian corals. Here we examine the limitations of mitochondrial gene barcoding in the sub‐class Octocorallia, a large, diverse, and ecologically important group of anthozoans. Pairwise genetic distance values (uncorrected p) were compared for three candidate barcoding regions: the Folmer region of COI; a fragment of the octocoral‐specific mitochondrial protein‐coding gene, msh1; and an extended barcode of msh1 plus COI with a short, adjacent intergenic region (igr1). Intraspecific variation was <0.5%, with most species exhibiting no variation in any of the three gene regions. Interspecific divergence was also low: 18.5% of congeneric morphospecies shared identical COI barcodes, and there was no discernible barcoding gap between intra‐ and interspecific p values. In a case study to assess regional octocoral biodiversity, COI and msh1 barcodes each identified 70% of morphospecies. In a second case study, a nucleotide character‐based analysis correctly identified 70% of species in the temperate genus Alcyonium. Although interspecific genetic distances were 2× greater for msh1 than COI, each marker identified similar numbers of species in the two case studies, and the extended COI + igr1 + msh1 barcode more effectively discriminated sister taxa in Alcyonium. Although far from perfect for species identification, a COI + igr1 + msh1 barcode nonetheless represents a valuable addition to the depauperate set of characters available for octocoral taxonomy.

Space partitioning by stony corals soft corals and benthic algae on the coral reefs of the northern Gulf of Eilat (Red Sea)

The major faunistic and floristic components occupying space on the coral reefs of the northern Gulf of Eilat (Red Sea) are stony corals, soft corals and benthic algae. The percent living coverage of the three components and the relative abundance of the different species of each component were studied by line transects, on the reef flats and the upper forereef zones of nine localities. A wider and higher range of living coverage values of stony corals were recorded at the upper fore-reef zones (18.30–49.09%) compared with the reef flats (5.50–31.66%) at the different stations. The most abundant stony corals on the reef flats areCyphastrea microphthalma, Stylophora pistillata, Favia favus, Porites lutea, Platygyra lamellina and the hydrozoanMillepora dichotoma. The fire coralM. dichotoma dominates the upper fore-reef zone in most of the stations. The average percent living coverage of soft corals on the reef flats ranged between 0.20 and 17.06%, and on the upper fore-reef zones between 1.68 and 15.13%. Seventy percent of the total living coverage of the soft coral community is contributed by 2 to 3 species. They tend to form large monospecific “carpets”, such as those composed ofSinularia sp.,Sarcophyton glaucum andLobophytum pauciflorum. The common benthic algae on the coral reef studied occur as turfs or macroscopic noncalcareous algae. They play a significant role in occupying space, especially on the reef flats. The most abundant algae recorded in all localities are the turfsSphacelaria tribuloides, Jania sp. and the macroscopic non-calcareous algaeTurbinaria elatensis andColpomenia sinuosa. Comparison between reef flats and upper fore-reef zones, in terms of average living cover of stony corals, shows that the variation among the reef flats is grater than the variation among the upper fore-reef zones. However, there is no significant variation in the average living coverage of soft corals between these two zones. Annual living-coverage values of algae on the reef flats are significantly higher than those of the upper fore-reef zones. Extremely low tides occurring periodically but unpredictably at Eilat cause mass mortality of the benthic communities on the reef flats reopening new spaces for settlement. The coexistence of stony corals, soft corals and algae on the reef ecosystem is due to different biological properties of each component. Opportunistic life histories of certain stony corals and most algae enable quick colonization of newly opened spaces. Lack of predators, high tolerance against abiotic factors and ability to form large aggregates of colonies are suggested as possible factors supporting the existence of soft corals in shallow water. Biological factors such as competition, predation and grazing pressure play an increasingly important role in controlling space utilization by the components studied with the advancement of succession.

Herbivory in Asymbiotic Soft Corals

A zooxanthellae-free soft coral from the Red Sea feeds almost exclusively on phytoplankton, a mode of nutrition so far unknown for corals. Herbivory was also found in three other azooxanthellate soft corals. In tropical oligotrophic waters, phytoplankton biomass density may be an order of magnitude higher than that of zooplankton. Use of this resource allows these azooxanthellate cnidarians to be highly productive in flow-exposed oligotrophic reef waters.

Prolonged lag in population outbreak of an invasive mussel: a shifting-habitat model

Biological invasions pose a great threat to the integrity of natural communities. Some invasive species demonstrate a population explosion shortly after arrival while in other cases a prolonged lag between arrival and population outbreak is evident. This paper describes a case of a prolonged lag and explores the possible mechanism for this lag. The Red Sea mussel Brachidontes pharaonis, a Lessepsian migrant, was first recorded in the Mediterranean seven years after the opening of the Suez Canal in 1869. Since then it spread along the Israeli coast and as far northwest as Sicily. Studies conducted in the late 1970s, when B. pharaonis was still rare, predicted that it would not establish dense populations along the Israeli coast and would not outcompete the indigenous mussel Mytilaster minimus, although it has strong negative effects on survival and growth of the native species. It was attributed to the invaders low intrinsic rate of increase relative to that of the native species, and to strong density-independent mortality generated by exposure to high wave action and sedimentation. In contrast to these predictions, we found massive formations of B. pharaonis beds after lag of about 120 years. We looked for distributional patterns that may explain this lag and found no south–north gradient but a strong habitat-dependent colonization. Most apparent are dense B. pharaonis mussel beds (density >300 per 100 cm2) on rocky platforms where mussel beds were absent in the past. These platforms lack the vermetid rim that is typical to this formation. In platforms protected by a biogenic rim, sediment accumulation is high and perennial algae flourish. None of the mussel species form beds in such habitats. We suggest that the delayed formation of B. pharaonis beds along the Israeli coast is a consequence of a recent shift in habitat conditions on some platforms. It is possible that receding of the biogenic rim at the edge of these platforms allowed more effective washing, reduced sediment accumulation, and reduced perennial algae cover making platforms more suitable for the mussels. Lower density-independent mortality allowed B. pharaonis to dominate on such platforms over the indigenous species. On beachrock, a habitat previously dominated by M. minimus, we recorded a rapid shift in numerical domination to B. pharaonis (from 1 : 7 to 1.4 : 1 Brachidontes/Mytilaster individuals) over a period of 4 years (1995–1999). This is probably a result of saturation of the habitat by B. pharaonis recruits originating from the established populations on platforms. Salinity changes and a potential genetic shift may also have contributed to the invasive mussel outbreak.

Vertical artificial structures as an alternative habitat for coral reef fishes in disturbed environments

Abstract The coral reefs of Eilat (Red Sea) have been heavily damaged as a result of extensive tourist activity. Artificial reefs have been demonstrated to be a potential tool for the restoration of marine habitats. We investigated the fish assemblage on pillars supporting the oil jetties in Eilat, studying the species composition on these vertical structures; and the relationships between fish community features and the structural characteristics of these artificial reefs over time, using multivariate regression analysis. The fish assemblage on these 25-year-old structures was shown to be abundant and diverse, comprising 146 species, distributed among 35 families. The 10 most abundant species were planktivores, accounting for 78% of all individuals; the most numerous fish was Neopomacentrus miryae (Tomacentridae). Size and complexity of pillars were correlated with fish abundance, richness and diversity, and related to the availability of shelters. These community indices increased near the bottom, possibly due to behavioral preferences. High coefficient of variance (CV) values indicated high temporal variability, resulting from a pronounced recruitment of N. miryae and other common species during April 1993. We discuss the possible use of these artificial reefs as a model for the construction of artificial habitats aimed at the rehabilitation of fish assemblages in deteriorating natural coral reef areas.

Community structure of stony and soft corals on vertical unplanned artificial reefs in Eilat (Red Sea): comparison to natural reefs

In many reef ecosystems, artificial reefs (AR) have become permanent additions to the area, sustaining well-developed benthic communities. Long-term studies on the development of AR coral communities are scarce, and comparisons with their natural surroundings are limited. The present study describes the stony and soft coral community structure of unplanned vertical AR in Eilat (Red Sea) that have progressed beyond the initial successional phases, and compares these to the adjacent natural reefs (NR). Coral communities were characterized using belt transects, conducted on 34- and 14-year-old unplanned AR, and on two proximate NR. Stony corals were the major component in the NR, while soft corals, mainly Nephtheidae, accounted for up to 90% of the total living coverage in the AR. This was attributed to physical and biological features associated with the AR’s vertical orientation, which was absent in the NR, and to the life history traits of these soft corals. Community differences between the two AR were related to structural stability and age. The results suggest that AR may increase local heterogeneity and space availability by adding novel habitats, increasing production and elevating species diversity in the surroundings.

Effect of an exotic prey on the feeding pattern of a predatory snail

The mussel Brachidontes pharaonis, which invaded the Mediterranean from the Red Sea about 120 years ago, has recently become abundant in many midlittoral and some infralittoral rocky habitats along the Israeli rocky shore. We investigated the influence of B. pharaonis, as a novel prey, on the foraging patterns of the large whelk Stramonita haemastoma in the field, and examined food preferences in the laboratory. S. haemastoma has shifted from indigenous species to feeding on the novel mussel when abundant. The whelk prefers to prey upon the invasive mussel over all indigenous species offered (e.g. barnacles and mussels), probably due to its larger size. In the midlittoral zone, the foraging activity of S. haemastoma is considerably low even where refuges are readily available (incisioned-rocks) and food density is high (mainly B. pharaonis). Higher proportions of whelks are actively foraging in the infralittoral zone but usually on smaller prey, mostly barnacles. We suggest that this differential foraging activity in the two zones is related to the degree of exposure to wave action. The midlittoral is inherently more exposed to wave action than the infralittoral, where sea conditions are more benign and the whelks may enjoy longer activity periods.

Reproduction and developmental pathways of Red Sea Xeniidae (Octocorallia, Alcyonacea)

This work on Red Sea alcyonaceans describes the reproductive patterns of 21 xeniid species. Gonochorism is the commonest sexual mode but simultaneous hermaphroditism was recorded in 4 species and brooding of planulae was observed in 15 species. The reproductive patterns of Xenia umbellata and Heteroxenia fuscescens were examined. X. umbellata exhibits seasonal spermatogenesis, continuous oogenesis and a 7 month period of planulation each year. H. fuscescens has continuous gametogenesis, and planulation occurs throughout the year, lacking any lunar pattern. The prolonged breeding season of H. fuscescens reflects intrapopulation asynchrony in larval development and subsequent maturation. Xeniids possess structurally similar gonads, but adopt diverse reproductive and developmental pathways.

Longevity, competence and energetic content in planulae of the soft coral Heteroxenia fuscescens

Abstract The longevity and competence period of the azooxanthellated planulae of the soft coral Heteroxenia fuscescens , a common shallow-reef inhabitant on the Red Sea reefs, were studied for the first time. The caloric content of the planulae in the course of their life is determined and its possible significance for the longevity and competence periods is considered. H. fuscescens planulae are able to metamorphose immediately upon release and tend to settle adjacent to their parent colonies. The current study presents evidence for absence of a pre-competence period. A maximal longevity of 50 days and a competence of 49 days were recorded, providing an effective dispersal time which encompasses virtually the entire lifespan of the planulae. A monthly variation was found in longevity and competence, possibly temperature related; significantly higher metamorphosis rates occurred during the hotter months of the year, indicating the occurrence of additional temporal variations related to the species reproduction. During late stages of the experiments most of the planulae underwent partial metamorphosis, probably due to a lack of necessary inducers for settlement. It is hypothesized that these polyps may obtain zooxanthellae through their mouth opening, thus acquiring the energy to extend their pelagic life, until they encounter such settlement inducers. Two-day old planulae had a caloric content of 0.58 ± 0.05 cal × planula −1 ; which decreased gradually with age, to a minimum of 0.35 ± 0.005 cal × planula −1 in 16-day old planulae. H. fuscescens has a wide distribution along the eastern coast of Africa, probably due to the longevity and competence of its planulae.