Cystoseira Myrica Research Articles

INDUCTION AND REDUCTION OF ANTI‐HERBIVORE DEFENSES IN BROWN AND RED MACROALGAE OFF THE KENYAN COAST1

Herbivory is particularly intense in tropical benthic communities, suggesting preference of constitutive, rather than inducible, anti‐herbivory defense. The objective of the study was to examine whether anti‐herbivore defenses in the red alga Hypnea pannosa J. Agardh and the brown algae Sargassum asperifolium Hering and G. Martens ex J. Agardh and Cystoseira myrica (S.G. Gmelin) C. Agardh could be induced and subsequently reduced in response to grazing by the amphipod Cymadusa filosa Savigny. During a 14‐day treatment phase, algae were exposed to amphipod grazing or were left ungrazed (control). Subsequently, one subset of algae was used in feeding assays, whereas another was cultivated for additional 14 days without consumers (recovery phase). At the end of each phase, bioassays were conducted to detect defensive traits in terms of differences in consumption rates of grazed and control pieces of live algae and agar‐based food containing nonpolar algal extracts. Consumption of grazed live S. asperifolium and H. pannosa specimens was lower than of control algae. Furthermore, nonpolar extracts of grazed S. asperifolium and C. myrica were less preferred than those from control algae. Defensive responses were exclusively detected after the treatment phase, although strong preference of ungrazed H. pannosa and C. myrica over grazed conspecifics continued throughout the recovery phase. These findings suggest that phenotypic plasticity in anti‐herbivory defense of marine macroalgae 1) might be more common than previously shown, 2) could be switched on and off within 2 weeks, and 3) can be found in nonpolar algal extracts.

Characterization of the alginates from algae harvested at the Egyptian Red Sea coast

The alginates from five species of brown algae from the Egyptian Red Sea coast, namely: Cystoseira trinode, Cystoseira myrica, Sargassum dentifolium, Sargassum asperifolium, and Sargassum latifolium, were isolated and their compositions and structures studied by 1H NMR spectroscopy. All the alginates studied contain more guluronic acid (G) than mannuronic acid (M) and have a homopolymeric block-type structure ( η<1). The intrinsic viscosity of the alginate samples range from 8.6 to 15.2 and the gel strength ranges from 10.97 to 15.51. The constitutional G- and M-blocks of alginates from two different species ( C. trinode and S. latifolium) were separated after partial acid hydrolysis. The 1H NMR spectral data of the blocks GG and MM obtained by chemical fractionation were compared with those of polymeric alginates. The monomeric uronic acids were separated by complete acid hydrolysis of S. asperifolium alginate and the G and M monomers were characterized by 1H, 13C NMR spectroscopy as well as by paper electrophoresis.

Cytotoxic hydroazulene diterpenes from the brown alga Cystoseira myrica.

Cytotoxicity-guided fractionation of the alcohol extract of the brown alga, Cystoseira myrica, afforded four new cytotoxic hydroazulene diterpenes, dictyone acetate (2), dictyol F monoacetate (4), isodictytriol monoacetate (6), and cystoseirol monoacetate (8), together with two known cytotoxic hydroazulene diterpenes, pachydictyol A (1) and dictyone (3). The constitution of each isolated compound has been determined on the basis of spectroscopic and chemical evidence.

Determination of the Biomass and Phycocolloid Contents of some Marine Algae from Eritrea

Specimens of five marine species of the brown (Cystoseira myrica, Sargassum torvum and Turbinaria ornata) and red (Gracilaria cortica and Gracilaria crassa) algae collected from the Red Sea coast of Eritrea were analyzed for their content of biomass and phycocolloids. Sargassum torvum was found to be the dominant species of a maximum biomass. Among the brown species, Turbinaria ornata was distinctive for its high content of alginic acid. Amount of agar did not fluctuate greatly in Gracilaria species. تمت دراسة وتعيين محتوى الكتلة الحيوية ومحتوى الغرويات النباتية لعينات خمس فصائل طحالب جمعت من ساحل البحر الأحمر بأريتريا. شملت الدراسة الطحالب البنية ( سيستوسيرا ميريكا، سيرجاسوم تورفوم وتيربيناريا أورناتا) والحمراء ( جراسيلاريا كورتيكا، وجراسيلياريا كراسا). تبينأن سيرجاسوم هي الفصلية السائدة بحد أعلى من الكتلة الحيوية. كشفت الدراسة أن تيربيناريا أورناتا تميزت بمحتواها العالي من حمض الجينيك. كمية الأجار لم تتبدل كثيرا في فصائل الجراسيلاريا.

ALGAL VEGETATION IN THE ELAT CORAL REEF RESERVE

During 1993–1996, algal vegetation was studied in three stations in Elat: two stations in the Hof Almog Nature Reserve and a third station at Taba, further south. In the Hof Almog stations, filamentous turf comprised more than half of the algal vegetation, macroalgae were scarce except for Lobophora variegata and crustose red algae, and total algal cover was low. In Taba, cover by macroalgae, e.g., Cystoseira myrica and Sargassum spp., and total algal cover was higher than in Hof Almog. Around the world, Cystoseira and Sargassum have disappeared or decreased in polluted areas. The almost total absence of these genera in the Hof Almog stations, in contrast to their ample occurrence at Taba, indicates pollution in Hof Almog but less in Taba. Numerous species found in earlier studies are absent in Elat, while other species are recorded for the first time in the present study.

Hofstenia arabiensis Nov. Sp. (Hofsteniidae): ANew Species of Acoelan Turbellaria from theRed Sea North of J eddah

A new Acoelan worm. Hofstenia arabiensis was found alive on the brown algae Sargassum vulgare (J.G. Agardh), and Cystoseira myrica, in the reef flat shoreward of the fringing reef in front of the Old King's Palace, North of Jeddah (Saudi Arabia). It is elongated having an anterior tip and a blunt posterior end. The color of the body is nearly yellowish red. The living worm is about 5 mm long and its breadth reaches about 1.25 mm. Nearly 35 specimens of this worm were collected during the month!; of May and June 1986. Reconstructions of the'new species were drawn from the median sagittal position by the exami!1ation of transverse, longitudinal and frontal sectipns of the worm stained by Haematoxylin-eosin and Mal- lory stain. This worm is related to the genus Hofstenia due to the fact that it has an integumentary nerve plexus. The mouth aperture is subterminal. The pharynx is strongly muscular. Vesicula seminalis is present and the ovary is follicular. It is a new species due to the fact that the worm is tubular, having a rounded anterior tip and a blunt and smooth posterior end: It has a yel- lowish red color. The worm has a network subepidermal nerve plexus ex- tending from the anterior tip of the body till the end of its first half, moreover, the central brain mass surrounding the statocyst is totally absent. The penis bulb is provided with only 4 chitinised spines. The sunk epithelial layer of the pharynx is unciliated and the oesophagus is missing.

Inhibitory activities of some marine algae on aflatoxin accumulation

A study was conducted to determine the ability of five marine algae of the phaeophyta class, namely, Sargassum despiense, Turbinaria decurrense, Dilophus ligulatus, Cystoseira myrica and Padina pavonia, to act against mycelial growth and/or aflatoxin accumulation by a toxigenic strain of Aspergillus flavus, at different levels, in rice corn steep medium. Aflatoxins were quantitated both intra- and extracellularly. At the level of 20 gm/100 ml, the first three algal species were the most effective, reducing mould growth to about 22% and aflatoxin accumulation to 8.5–12% of control. The other two algae also reduced aflatoxin production by about 84%. The volatile oils of the three algae showed antifungal properties. Fortification of the medium with either fatty acids or unsaponifiable matter resulted in reducting aflatoxin formation to 11% and 25% respectively with milder effect on mould growth.