Skeletal calcification patterns in the sea urchin Tripneustes gratilla elatensis (Echinoidea: Regularia)

A comprehensive study on skeletal calcification in the regular echinoid Tripneustes gratilla elatensis was carried out between 1979 and 1981 in the northern Gulf of Eilat (Red Sea), employing size measurement, allometry and radiotracer techniques. Uptake rates of the isotope ⁴⁵Ca were used to estimate the calcification rate of whole tests. Calcification rates of the different skeletal parts and the ⁴⁵Ca uptake along the sutural margins of individual plates were also measured. Whole-test calcification rates for juvenile individuals, 11 to 13 mm in diameter, relative to their skeletal Ca dry weight, calculated using the allometric relationship between skeletal dry weight and diameter, were 1.5 to 1.8% d^-1 for 4 to 8 h of incubation, while calcification rates obtained from periodical size measurements and allometrical constants amounted to 2.75% d^-1. The apparent discrepancy between these results is explained partly by the short duration of the incubations, during which the internal calcium pools, apparently in the coelom, were not fully saturated with the radioactive tracer. This discrepancy decreased when longer radioactive incubations were used, or when a post-incubational deposition of ⁴⁵Ca from these pools was allowed. The size of these pools is roughly 10 mol Ca per 13-mm individual, and it resides probably in the coelom where Ca concentration is 3 times higher than in seawater. The calcification rates given as percentage of skeleton added per day, both for the radioactive and allometric methods, decreased with the urchins' size. The calcification patterns of various components of the skeleton generally fitted their allometrical trends — a relative decrease in the size of the spines, apical plates and lantern. The teeth calcify rapidly to compensate for the constant erosion of their tips. Calcification per plate decreased exponentially from the apex to the peristome. Plate-edge calcification patterns of both interambulacral and ambulacral plates fitted patterns derived from size increment measurements, using natural growth-lines. Typically, most plates grow more horizontally (latitudinally) than vertically. It is suggested that the vertical vs horizontal calcification ratio (v/h) determines the individual plate growth and affects the whole test morphology.     

Littoral fauna of the Red Sea: the population of non-scleractinian anthozoans of shallow waters of the Red Sea (Eilat)

Approximately 22 species of sea anemones and 20 species of alcyonarians were found on the reef fringing the shallow water at Eilat (Gulf of Aqaba) and other localities along the Red Sea coast of the Sinai Peninsula. Investigations showed that these 2 groups of non-scleractinian coelenterates from (on different substrates) well identified colonies, part of them inhabiting sandy bottoms, other groups growing on the reef surface. Observations lead to the conclusion that several of the sea anemones and alcyonarians can act, under certain conditions, as factors limiting the development of hermatypic corals. In some areas, several species of the 2 groups of animals are found together with their symbiotic partners, such as fishes and crustaceans.This research has been sponsored partly by a grant from the Smithsonian Institution, No. SFC-7-0074 to L. B. Slobodkin (N. Y.) and L. Fishelson (T.-A.).     

Food composition and feeding behavior of shallow-water crinoids at Eilat (Red Sea)

The food of 3 feather-stars, Lamprometra klunzingeri Hartlaub, 1890), Heterometra savignii (J. Müller, 1841) and Capillaster multiradiatus (Linnaeus, 1758), from the shallow water of Eilat (Red Sea) was found to be composed of planktonic and semi-benthalic organisms with a strong dominance of zooplankton. Monthly analyses of stomach contents showed seasonal changes in the participation of various systematic units in the diet. Food-comprising organisms were found to be selected according to size, and those measuring up to 400 formed 90% of the diet.This research has been sponsored partly by the Oceanic Biology Branch, Office of Naval Research, U.S.A. under contract N 62558-4556 and contract F 671052 67C 0043 between the Office of N.R. and the Tel-Aviv University. It represents part of the M.Sc. thesis of the first named author (in the framework of Red Sea investigations headed by Dr. L. Fishelson).     

Three party symbiosis: acoelomorph worms,corals and unicellular algal symbionts in Eilat (Red Sea)

Epizoic worms were found to occur on certain coral colonies from reefs off the coast of Eilat (Red Sea). We identified 14 coral species infested by acoelomorph worms at a depth range of 2–50 m. The host corals were all zooxanthellate and included both massive and branching stony corals and a soft coral. Worms from all hosts were identified as belonging to the genus Waminoa and contained two distinct algal symbionts differing in size. The smaller one was identified as Symbiodinium sp. and the larger one is presumed to belong to the genus Amphidinium. Worm-infested colonies of the soft coral, Stereonephthya cundabiluensis, lacked a mucus layer and exhibited distinct cell microvilli, a phenotype not present in colonies lacking Waminoa sp. In most cases, both cnidarian and Acoelomorph hosts displayed high specificity for genetically distinctive Symbiodinium spp. These observations show that the epizoic worms do not acquire their symbionts from the “host” coral.     

Ecological and biological phenomena influencing coral-species composition on the reef tables at Eilat (Gulf of Aqaba,Red Sea)

Observations performed on coral colonies damaged during a very low tide on the shallow-water reef tables at Eilat (Red Sea), showed that most colonies are able to regenerate if parts of the living tissue remain intact on the skeletons. Brain-like corals, such asFavia favus andPlatygyra lamellina, were found to be more resistant to dessication than the delicate bush-like forms. It was also observed that the exposed skeletons of corals were immediately covered by a successive group of algae with a rich invertebrate epifauna among them. It is postulated that unpredicted extreme low water, occurring once in several years, could be the factor that prevents crowding on the reef tables, thus keeping high the level of coralspecies diversity.Supported, in part, by a grant from the Smithsonian Institution, USA. SFC-70074.This paper was presented at the Intecol Symposium held in Dubrovnik in March, 1972.     

Seasonal variations in the stable isotopic composition and the skeletal density pattern of the coralPorites lobata (Gulf of Eilat,Red Sea)

The stable carbon and oxygen isotopic compositions of the massive coralPorites lobata collected from the Gulf of Eilat, Red Sea, in May 1987 were measured along the vertical growth axis. The isotopic compositions show annual periodicity. The variations along the isotopic profile, compared with the X-radiography, indicate that the high-density bands are enriched in¹⁸O and deposited during the season of lowest water temperature (winter). In contrast, the low-density bands are depleted in¹⁸O and deposited during the warmest seawater temperatures (summer). The stable carbon and the oxygen isotopic ratios are negatively correlated with a shift in phase. During the season of higher water temperatures and light intensity values (summer), the skeleton is depleted in¹⁸O and enriched in¹³C and vice versa for the winter time. The shift between the carbon and the oxygen isotopic curves reflects the shift between the seasonal light intensities and seasonal temperature variations in the shallow water. The oxygen isotope ratio was used to detect the seasonal variations in seawater temperatures. The coral aragonitic skeleton is depleted in¹⁸O compared to apparent equilibrium with ambient seawater. The disequilibria range from (ca.) -3.10 to -3.50 with an average value of 3.40. The isotope fractionation behavior during skeleton precipitation is discussed in light of the environmental variables.     

Induction of metamorphosis of two species of sea urchin from Sea of Japan

The induction of metamorphosis in mature larvae by selected chemical compounds and natural substrata was investigated in two species of sea urchins from the Sea of Japan, Strongylocentrotus intermedius and Scaphechinus mirabilis. Glutamine in crystalline form was added directly to water containing mature larvae, and this compound, at a final concentration of 10 g ml^-1, was an inducer of metamorphosis in S. intermedius (100% activity) and S. mirabilis (50% activity). Gutamine, or its natural mimetic molecules, may be an active component of the exogenous cue that induces metamorphosis of S. intermedius larvae. This exogenous cue was produced by the epiphytic calcareous algae, Melobesia spp. that colonized the older sea grass Zostera marina. Glutamic acid was also used as an inducer of metamorphosis for S. intermedius and S. mirabilis larvae (50 to 60% activity), but it was toxic to the larvae.     

The dual functions of sea urchin gonads are reflected in the temporal variations of their biochemistry

Fatty acid analyses are emerging as a powerful technique to probe trophic interactions between organisms. In this paper, the application of both this procedure and gonad index (GI) determination on two populations (intertidal and subtidal) of the echinoid Psammechinus miliaris is reported. The investigation spanned the 3-month spawning period of Scottish west coast populations. In both populations a progressive decrease in the GI was found, coupled with an increasing maturity stage (from mature to spent). Sexual maturation and decrease in GI was synchronous between the two populations. In conjunction, there were distinct changes in gonad biochemistry. Differences in the fatty acid composition of the gonad reflected the changes in sexual maturation. Mature males and females had significant differences in the fatty acid composition of their gonads, whereas post-spawned individuals showed no gender differences. Male urchins had higher levels of polyunsaturated fatty acids (PUFAs) compared to females, and there was a dramatic reduction in the fatty acids 22:6(n−3) and 20:5(n−3) with increasing maturity stage. Using multivariate statistical techniques, these changes in the fatty acid composition of the sea urchin gonad were linked to habitat related diet differences combined with gender differences. These changes in the fatty acid signatures clearly reflect the dual function of the gonad as both a nutrient store and a reproductive organ.     

Coral recruitment: a spatio-temporal analysis along the coastline of Eilat,northern Red Sea

Recruitment rates of stony corals to artificial substrates were monitored for 2 years at 20 sites along the coast of Eilat, northern Red Sea, to compare with those recorded at other coral reef locations and to assess variation in recruitment at several spatial scales. Coral recruitment was low compared to that observed on the Great Barrier Reef in Australia, but was similar to levels reported from other high-latitude reef locations. Pocilloporids were the most abundant coral recruits in all seasons. Recruitment was twofold higher during the first year than during the second year of study. There was considerable spatial variability, with the largest proportion of variance, apart from the error term, attributable to differences between sites, at a scale of 10² m. Spearmans ranked correlation showed consistency in spatial patterns of recruitment of pocilloporid corals between years, but not of acroporid corals. During spring, when only the brooding pocilloporid coral Stylophora pistillata reproduces at this locality, most coral recruitment occurred at central and southern sites adjacent to well-developed coral reefs. During summer, recruitment patterns varied significantly between years, with wide variation in the recruitment of broadcasting acroporid corals at northern sites located distant from coral reefs. Settlement was low at all sites during autumn and winter. This work is the first detailed analysis of coral recruitment patterns in the Red Sea, and contributes to the understanding of the spatial and temporal scales of variation in this important reef process.Communicated by O. Kinne, Oldendorf/Luhe     

Migration,habitat use,and competition among mobile corals (Scleractinia: Fungiidae) in the Gulf of Eilat,Red Sea

We examined the impact of seven species of mobile mushroom corals (Fungiidae) on the community structure of sheltered reef slopes in terms of their patterns of migration, habitat use and competition with other benthic organisms. On fringing reefs at Eilat, Red Sea, polyps detached at 1 to 6 cm length, and grew to 11–55 cm length. Attached mushroom corals were oriented vertically in reef cavities. Detached corals migrated downward on the reef slope and onto rubble or soft substratum at the reef base, at 29 to 71 cmyr^–1. Mobility decreased with corallum size and extent of undersurface ornamentation. In aquaria, small corals righted themselves and migrated up to 6 cm d^–1 by nocturnally inflating and pushing their tissues against the substratum. Autonomous coral behavior and storm-generated water motion appeared to account for most fungiid mobility at Eilat. Mushroom corals did not damage each other upon contact, even in multi-species aggregations, but unilaterally damaged non-fungiid scleractinian corals. Their dominance during contact interactions retards overgrowth by larger attached scleractinians, and mobility allows them to colonize soft substrata not accessible to most other reef corals.     

Differentiation of protoplasm in nummulitidae (Foraminifera) from Elat,Red Sea

Chambers and canal system in the shells of Operculina ammonoides (Gronovius) and Heterostegina depressa d'Orbigny contain different protoplasm. The connections between the two main parts of the protoplasmic body are much smaller than the connections from chamber to chamber by the stolo system. The connections between chamber and canal system are located in the marginal sulcus and at the base of the chamber. The chamber protoplast (including the stolo system) is protected by a relatively thick, lamellar, mucopolysaccharide membrane — called organic lining — which represents also the template for the mineralization of the shell. Together, organic lining and shell form the cell wall. Over the pore holes in the lateral chamber walls, the organic lining thins out, but is not perforated. The plasma membrane below the organic lining seems to be differentiated by a bossy surface with comparatively coarse granules. The symbionts are concentrated below the lateral wall of the chambers, nestling against 2 or 3 pore-hole depressions. The differentiation of the organic lining, the plasma membrane below the pore holes, and the position of the symbionts in the chamber plasma point to a physiologic relationship between pores and symbionts. The cell organelles in the chamber protoplasm indicate the mainly metabolic function of the chamber protoplast. The protoplasm in the canal system is covered only by the plasma membrane, and is particularly rich in microtubuli similar to ordinary foraminiferal rhizopods. The canal system is, therefore, interpreted as consisting of a system of invaginations of the cell wall determining the morphology of proximal parts of the pseudopods.     

Reproductive cycle of the sea urchin Holopneustes purpurascens (Temnopleuridae: Echinodermata)

This study documents the annual reproductive cycle of the Temnopleurid echinoid Holopneustes purpurascens near Sydney. H. purpurascens reached sexual maturity between 11 and 26 mm diameter and was gonochoristic. The sequence of oogenesis was similar to previously described echinoids. However, the proportion of eggs at each stage showed no temporal pattern in abundance, suggesting that vitellogenesis is continuous throughout the year. Spermatogenesis was also similar to other echinoids and showed a significant increase in the proportion of partially spawned testes in spring, followed by a similar increase in the proportion of partially spawned testes in late spring and summer. Gonad indices showed a peak in weight from late winter to mid-spring (9.10ǃ.47 for females; 6.28ǂ.43 for males; mean-SE), then a decline for both sexes. Although spawning was variable over time, there was a peak in the proportion of spawning from late winter to early summer that correlated with the observed peaks in gonad indices and gametogenic cycles. The demographic implications of this reproductive pattern are that new recruits can enter the population through synchronous spawning during the breeding period, and smaller haphazard spawning events at other times of the year.     

Profitability and sustainability of edible sea urchin fishery in Sardinia (Italy)

Sea urchin (Paracentrotus lividus) fishery is intensively practiced in several areas of the Mediterranean basin. In Sardinia, as well as other Mediterranean countries, sea urchin is a basic ingredient for several dishes due to the delicacy of its gonads (roe), and demand is constantly increasing. Restrictions have been implemented in order to minimise the risk of overexploitation, however, these measures might jeopardize economic convenience in sea urchin harvesting. This paper estimates economic convenience within the edible sea urchin fishery in Sardinia. It aims to determine whether both profitability and sustainability, in terms of the preservation of sea urchin stock, can be guaranteed by actual policy regulation. We found high variability in terms of captures and profitability among firms, and a considerable degree of this variability is the result of technological differences between fishing methods. Analysis also suggests that a slight increase in allowed captures should generate a more than proportional increase in profits. This evidence gives some useful suggestions for improving the efficacy of policies in affecting the economic and environmental sustainability of the Mediterranean sea urchin fishery.     

Seasonality in gonads,fat deposits and condition of tropical surgeonfishes (Teleostei: Acanthuridae)

Lipids are stored in mesenteries surrouding the gut and in paired, retroperitoneal fat bodies dorsal to the anal fin in at least 24 surgeonfishes representing 5 genera (Acanthurus, Ctenochaetus, Naso, Prionurus, Zebrasoma) from Western Mexico, Hawaii, French Polynesia, Great Barrier Reef and the Red Sea. In A. nigrofuscus from the Red Sea and C. striatus from French Polynesia, fat stores and condition index (K=100 W/L ³) increased during cool seasons, several months before gonads developed, and declined with the onset of gonadal development. Fat bodies and mesenteric fat deposits developed in all sizes of A. nigrofuscus and C. striatus, and condition paralleled seasonal changes in fat deposits. Gonads of A. nigrofuscus developed in specimens of 76 to 159 mm standard length (SL), while they developed in C. striatus only at lengths>170 mm total length (TL) for females and 195 mm TL for males. Mesenteric fats and fat bodies exhibited similar changes in size, and did not differ in occurrence of major groups of lipids or their relative prevalence. The relative proportions of the major lipid classes differed, however, between these storage sites and other tissues. Muscle, liver and gonads contained less triacylglycerol relative to cholesterol and polar lipid than did mesenteric or fat body lipids. Energy and nutrients acquired during cool saasons with short feeding days appear to support reproductive events during warm seasons, when feeding during longer days fails to meet demands. Fat stores and condition continue to decline beyond the reproductive season until winter.     

Bioactivity as an Options Value of Sea Cucumbers in the Egyptian Red Sea

Abstract:  The utility of a species can be divided into its direct, indirect, and options values. In the marine environment, direct consumptive values predominate and often lead to overexploitation at the expense of significant options values derived through bioprospecting for natural products. We surveyed the waters of the Egyptian Red Sea coast (Gulf of Aqaba [north] and the Red Sea [south]) for species of sea cucumbers and analyzed extracts from species for a range of bioactivities with potential biomedical applications. All habitat types were surveyed within these regions. We found 22 species of sea cucumber of which two, Holothuria fuscogilva and Holothuria flavomaculata , were recorded in Egypt for the first time. Although none of the species identified were unique to the Gulf of Aqaba, 10 species were only found in the Red Sea sector. Bioassay results showed that although no species had antibacterial activity, most extracts exhibited activity against Candida and Leishmania but were most active against a LoVo mammalian carcinoma cell line. Our most significant finding was the intraspecific variation in bioactivity in individuals collected from different habitat types and sectors of the coast. This variation may reflect the effect of environment on secondary metabolite production or may indicate significant genetic diversity between populations within a species. Our results indicate a potentially significant options value to sea cucumbers through bioprospecting. Given the importance of economic development in countries such as Egypt and the perceived low conservation value of invertebrates such as sea cucumbers, the linking of these factors to conservation is vital for the maintenance and sustainable exploitation of these animals .     

Fish predators and scavengers of the sea urchin Paracentrotus lividus in protected areas of the north-west Mediterranean Sea

Direct observations of predation on 436 individuals of the sea urchin Paracentrotus lividus (Lamarck) were carried out in infralittoral rocky bottoms (between 5 and 20 m deep) in three Mediterranean marine reserves. The predator guild was composed of six fish species, the sparids Diplodus sargus and D. vulgaris being the main predators, and the labrid Coris julis a major predator of juvenile sea urchins. Four species attempted but failed to open sea urchins. The scavenger guild was most rich in species, with 17 species observed. Predation was size-dependent; the size of predators increased with increasing size of the sea urchins. The presence of two feeding guilds is suggested, one composed of sparids (Diplodus spp.), able to kill juvenile and adult sea urchins, and the other composed of labrids (mainly C. julis), which feed on juvenile sea urchins. To avoid the extension of overgrazed, barren areas created by P. lividus populations, fisheries' regulations should focus on major sea-urchin predators, chiefly D. sargus, D. vulgaris and C. julis. Received: 23 April 1997 / Accepted: 30 May 1997     

Removal of glycine from solution by the sea urchin Strongylocentrotus purpuratus

Radioautography and liquid-scintillation counting of juvenile sea urchins — Strongylocentrotus purpuratus (Stimpson) — exposed to ³H- and ¹⁴C-labeled glycine showed that the ³H is rapidly translocated throughout the animal and lost, while the ¹⁴C is slowly translocated into the interior of the urchin and incorporated into insoluble material.     

Ammonia as confounding factor in toxicity tests with the sea urchin Paracentrotus lividus (Lmk)

The aim of this study was to investigate the toxicity of total ammonia towards sea urchin bioassays, in order to elucidate the role of ammonia as confounding factor in sediment quality assessment studies. New toxicity data, expressed as EC50, NOEC and LOEC are reported for Paracentrotus lividus based on experiments at differing pH values. Results confirmed that sperm cell toxicity test is not very sensitive to ammonia, while total ammonia embryotoxicity is strictly pH dependent. Accurate observations of embryotoxic effects at increasing total ammonia concentrations evidenced progressive shifts from malformed plutei to gastrula and blastula blockages. Toxicity data obtained for P. lividus are comparable with previous results with other echinoid species.     

Dietary accumulation of UV-absorbing mycosporine-like amino acids (MAAs) by the green sea urchin (Strongylocentrotus droebachiensis)

The bioaccumulation of ultraviolet radiation-absorbing mycosporine-like amino acids (MAAs) by Strongylocentrotus droebachiensis (Müller) was determined in specimens maintained on MAA-rich and MAA-deficient diets. Individuals were fed either the red alga Mastocarpus stellatus (Stackhouse), which has a high concentration of the MAA shinorine (6.98 nmolmg^–1 dry wt), and trace amounts of the MAAs porphyra-334, asterina-330 and palythine, or the brown alga Laminaria saccharina (Lamouroux), which contains no detectable MAAs. Reproductively spent urchins were fed ad libitum during a 9 mo period in 1992 to 1993 until they were once again gravid. To monitor accumulation, samples of urchin tissues and ingested food were taken throughout the 9 mo period from males and females maintained on each diet, and the concentrations of MAAs determined using high performance liquid chromatography. Urchins maintained on a diet of M. stellatus showed an ovarian shinorine concentration (8.33 nmol mg^–1 dry wt) 25 times higher than those fed L. saccharina. There was no change in MAA content of testes or somatic tissues in either feeding group. More than 99% of the MAAs present in an experimental meal of M. stellatus were removed during passage through the gut. Previous studies have inferred dietary accumulation of MAAs by comparing MAAs present in animal tissues with the consumer's potential diet in the field. This is the first study to have monitored MAA accumulation in animal tissues in conjunction with a controlled diet having a known MAA composition. Concentrating MAAs in the ovaries may provide eggs released into the water column with protection from damaging solar ultraviolet radiation.