Leptogorgia Virgulata Research Articles

Evidence for trophic niche partitioning among three temperate gorgonian octocorals

Trophic niche theory predicts that species in competition for a limiting resource will evolve adaptations allowing them to consume alternative resources and occupy new niche space. Trophic niche partitioning is often identified by differences in the morphology of feeding structures across species; however, these differences may not always be readily observable. Due to their constrained polyp morphology, octocorals are often viewed a single functional group that contributes to benthic-pelagic coupling by feeding opportunistically on available particles. To test the hypothesis that sympatric gorgonians share the same trophic niche, feeding selectivity of three gorgonian species (Leptogorgia virgulata, Muricea pendula, and Thesea nivea) was compared using a combination of flume experiments and stable isotope analysis. The tentacle length and polyp surface area of L. virgulata and T. nivea were also measured and compared. In flume experiments, clearance of rotifers (“typical” zooplankton) and a mixture of cultured phytoplankton indicated that L. virgulata and T. nivea fed on zooplankton and not phytoplankton. Stable isotope values for all three species are consistent with distinct trophic niches, with M. pendula occupying a lower trophic level. Thesea nivea was found to have significantly larger polyp surface area and tentacle length; however, this did not appear to explain observed trophic differences. The results of this study provide evidence for niche partitioning, but future work is required to better understand the mechanism behind this divergence.

The Biology and Evolution of Calcite and Aragonite Mineralization in Octocorallia

Octocorallia (class Anthozoa, phylum Cnidaria) is a group of calcifying corals displaying a wide diversity of mineral skeletons. This includes skeletal structures composed of different calcium carbonate polymorphs (aragonite and calcite). This represents a unique feature among anthozoans, as scleractinian corals (subclass Hexacorallia), main reef builders and focus of biomineralization research, are all characterized by an aragonite exoskeleton. From an evolutionary perspective, the presence of aragonitic skeletons in Octocorallia is puzzling as it is observed in very few species and has apparently originated during a Calcite sea (i.e., time interval characterized by calcite-inducing seawater conditions). Despite this, octocorals have been systematically overlooked in biomineralization studies. Here we review what is known about octocoral biomineralization, focusing on the evolutionary and biological processes that underlie calcite and aragonite formation. Although differences in research focus between octocorals and scleractinians are often mentioned, we highlight how strong variability also exists between different octocoral groups. Different main aspects of octocoral biomineralization have been in fact studied in a small set of species, including the (calcitic) gorgonianLeptogorgia virgulataand/or the precious coralCorallium rubrum.These include descriptions of calcifying cells (scleroblasts), calcium transport and chemistry of the calcification fluids. With the exception of few histological observations, no information on these features is available for aragonitic octocorals. Availability of sequencing data is also heterogeneous between groups, with no transcriptome or genome available, for instance, for the clade Calcaxonia. Although calcite represents by far the most common polymorph deposited by octocorals, we argue that studying aragonite-forming could provide insight on octocoral, and more generally anthozoan, biomineralization. First and foremost it would allow to compare calcification processes between octocoral groups, highlighting homologies and differences. Secondly, similarities (exoskeleton) betweenHelioporaand scleractinian skeletons, would provide further insight on which biomineralization features are driven by skeleton characteristics (shared by scleractinians and aragonitic octocorals) and those driven by taxonomy (shared by octocorals regardless of skeleton polymorph). Including the diversity of anthozoan mineralization strategies into biomineralization studies remains thus essential to comprehensively study how skeletons form and evolved within this ecologically important group of marine animals.

Sea whip coral Leptogorgia virgulata in the Mid-Atlantic Bight: Colony complexity, age, and growth

Sea whip coral Leptogorgia virgulata are a common structural component of both natural and artificial hard-bottom reef habitats in the mid-Atlantic region and may serve as essential habitat for commercially valuable species. However, they are slow-growing, easily damaged, and especially vulnerable to damage by passive fishing gear such as pots and traps. Despite their potential importance, until recently, sea whips have been generally understudied in this region. We examined the colony complexity, length, age, and growth of sea whips from four artificial reef sites in the mid-Atlantic region to gain a better understanding of their biology in the area. There were no significant differences in the bifurcation (Rb) and tributary to source (T/S) ratios between sites, with the Rb ≈3 for all sites, indicating similar complexity between sites. The total length distribution was 8.3 cm to 85.3 cm, and 50% of corals in the range of 34.2–56.4 cm. Age, estimated from annual growth ring counts, ranged from 2 to 15 y, with 50% of corals in the range of 6 to 8 y. The large proportion of middle-sized and middle-aged corals suggests episodic recruitment. Age-length keys showed the trend of age increasing with total coral length, and a von Bertalanffy growth model demonstrated size-dependent growth following the equation: E[L—t] (cm) = 86.1(1−e−0.14(t−1.44)). This is the first study providing such data for sea whips in the coastal mid-Atlantic region, and the baseline created will be a useful reference to study changes over time.

Mitogenomic phylogenetic analyses of Leptogorgia virgulata and Leptogorgia hebes (Anthozoa: Octocorallia) from the Gulf of Mexico provides insight on Gorgoniidae divergence between Pacific and Atlantic lineages.

The use of genetics in recent years has brought to light the need to reevaluate the classification of many gorgonian octocorals. This study focuses on two Leptogorgia species—Leptogorgia virgulata and Leptogorgia hebes—from the northwestern Gulf of Mexico (GOM). We target complete mitochondrial genomes and mtMutS sequences, and integrate this data with previous genetic research of gorgonian corals to resolve phylogenetic relationships and estimate divergence times. This study contributes the first complete mitochondrial genomes for L. ptogorgia virgulata and L. hebes. Our resulting phylogenies stress the need to redefine the taxonomy of the genus Leptogorgia in its entirety. The fossil‐calibrated divergence times for Eastern Pacific and Western Atlantic Leptogorgia species based on complete mitochondrial genomes shows that the use of multiple genes results in estimates of more recent speciation events than previous research based on single genes. These more recent divergence times are in agreement with geologic data pertaining to the formation of the Isthmus of Panama.

The relationship between fish abundance and benthic community structure on artificial reefs in the Mid-Atlantic Bight, and the importance of sea whip corals Leptogorgia virgulata.

Autogenic engineers (i.e., biogenic structure) add to habitat complexity by altering the environment by their own physical structures. The presence of autogenic engineers is correlated with increases in species abundance and biodiversity. Biogenic structural communities off the coast of Delaware, Maryland, and Virginia (Delmarva) are comprised of multiple species including boring sponge Cliona celata, various hydroids (i.e., Tubularia sp., Obelia sp., Campanular sp.), northern stone coral Astrangia poculata, sea whips Leptogorgia virgulata, and blue mussels Mytilus edulis. Sea whips are soft corals that provide the majority of vertical height to benthic structure off the coast of the Delmarva peninsula. The mid-Atlantic bight is inhabited by several economically valuable fishes; however, data regarding habitat composition, habitat quality, and fish abundance are scarce. We collected quadrat and sea whip images from 12 artificial reef sites (i.e., shipwrecks) ranging from 10 to 24 m depth to determine proportional coverage of biogenic structures and to assess habitat health, respectively. Underwater video surveys were used to estimate fish abundances on the 12 study sites and determine if fish abundance was related to biogenic coverage and habitat health. Our results showed that higher fish abundance was significantly correlated with higher proportional sea whip coral coverage, but showed no significant relationship to other biogenic structure. Assessment of sea whip condition (as a damage index) showed that sea whip corals on artificial reefs off the Delmarva coast exhibited minor signs of degradation that did not differ significantly among study sites.

Molecular Cloning and Characterization of First Organic Matrix Protein from Sclerites of Red Coral, Corallium rubrum

We report here for the first time the isolation and characterization of a protein from the organic matrix (OM) of the sclerites of the alcyonarian, Corallium rubrum. This protein named scleritin is one of the predominant proteins extracted from the EDTA-soluble fraction of the OM. The entire open reading frame (ORF) was obtained by comparing amino acid sequences from de novo mass spectrometry and Edman degradation with an expressed sequence tag library dataset of C. rubrum. Scleritin is a secreted basic phosphorylated protein which exhibits a short amino acid sequence of 135 amino acids and a signal peptide of 20 amino acids. From specific antibodies raised against peptide sequences of scleritin, we obtained immunolabeling of scleroblasts and OM of the sclerites which provides information on the biomineralization pathway in C. rubrum.

Effects of salinity and sedimentation on the Gorgonian Coral, Leptogorgia virgulata (Lamarck 1815)

Construction of jetties along the Texas coast has provided hard substrate biota with suitable habitats for attachment that is otherwise scarce. Although similar to natural hard bottom environments such as coral reefs or offshore banks, jetties in temperate or subtropical areas are subjected to substantially more environmental instability including swift channelized currents, terrestrial runoff, maintenance dredging, fluctuating temperatures, and swells from ship and recreational boat traffic. The gorgonian coral Leptogorgia virgulata, found on south Texas jetties, is constantly exposed to the variable salinity and sediment loads associated with these jetty systems. In this study, L. virgulata was collected from the Aransas Pass jetties near Corpus Christi, Texas and experimentally tested to determine their ability to tolerate a range of salinities and sediment loads over 14 days. In response to salinity, L. virgulata showed significant tissue loss ( p < 0.05) at 10, 15, 45, 50 and 60 with 100% loss at 60, but showed little or no tissue loss and peak polyp activity at 25–40. When exposed to sedimentation treatments up to 20,000 mg l − 1 , L. virgulata maintained healthy tissue and polyp feeding activity and did not show any symptoms or significant differences in tissue loss. These results indicate that L. virgulata is well-adapted to euryhaline conditions and is very tolerant of high sediment loads, a factor in its success on structures along the Texas coast.

Coral as Environmental BioIndicators: Ecological and Morphological Effects of Gasoline on Gorgonian Corals, Leptogorgia virgulata

Oil spills are the most common sources of pollution in marine ecosystems occurring worldwide, causing problems not only for benthic and pelagic organisms but also for terrestrial species that feed on marine organisms. Coral, more so than many other organisms, are sensitive to tiny changes in the marine environment, which makes them an excellent bioindicator of changing environmental conditions. In this study, Leptogorgia virgulata located in the Aransas Pass ship channel, Port Aransas, Texas was examined to determine the level of gasoline (10 ppm, 50 ppm, and 100 ppm) this species could tolerate. Our experimental research compared both coral-tips (the youngest and most rapid growing part of gorgonian corals) to the coral-bases (the older part of these coral) of L. virgulata. Affects were characterized by determining the number of sclerites sloughed off over seven days (168 h). Comparative analysis between treatments show that gasoline has a significant negative consequence, damaging coral tissue over time (ANOVA, p=0.008; ?=0.05). Similarly, the sensitivity of tips to bases was significantly different (ANOVA, p=0.003; ?=0.05). The coral-bases sloughed more cells and sclerites than the coral-tips indicating greater sensitivity to the gasoline treatments. This study also showed that at low concentrations, environmental managers may have as much as 48 h to mitigate the effects of a petroleum spill. Any clean-up not completed beyond that period of time will cause massive death to the coral L. virgulata and associated inhabitants, including potentially important sport fishes known to associate with these benthic fauna.

Antimicrobial activity in the common seawhip, Leptogorgia virgulata (Cnidaria: Gorgonaceae)

Antimicrobial activity was examined in the gorgonian Leptogorgia virgulata (common seawhip) from South Carolina waters. Extraction and assay protocols were developed to identify antimicrobial activity in crude extracts of L. virgulata. Detection was determined by liquid growth inhibition assays using Escherichia coli BL21, Vibrio harveyii, Micrococcus luteus, and a Bacillus sp. isolate. This represents the first report of antimicrobial activity in L. virgulata, a temperate/sub-tropical coral of the western Atlantic Ocean. Results from growth inhibition assays guided a fractionation scheme to identify active compounds. Reverse-phase HPLC, HPLC–mass spectrometry, and 1H and 13C NMR spectroscopy were used to isolate, purify, and characterize metabolites in antimicrobial fractions of L. virgulata. Corroborative HPLC–MS/NMR evidence validated the presence of homarine and a homarine analog, well-known emetic metabolites previously isolated from L. virgulata, in coral extracts. In subsequent assays, partially-purified L. virgulata fractions collected from HPLC–MS fractionation were shown to contain antimicrobial activity using M. luteus and V. harveyii. This study provides evidence that homarine is an active constituent of the innate immune system in L. virgulata. We speculate it may act synergistically with cofactors and/or congeners in this octocoral to mount a response to microbial invasion and disease.

Expression of heat shock and cold shock proteins in the gorgonian Leptogorgia virgulata

In this study, we analyzed the response of the temperate, shallow-water gorgonian, Leptogorgia virgulata, to temperature stress. Proteins were pulse labeled with (35)S-methionine/cysteine for 1 h to 2 h at 22 degrees C (control), or 38 degrees C, or for 4 h at 12.5 degrees C. Heat shock induced synthesis of unique proteins of 112, 89, and 74 kDa, with 102, 98 and 56 kDa proteins present in the control as well. Cold shock from 22 degrees C-12.5 degrees C induced the synthesis of a 25 kDa protein, with a 44 kDa protein present in the control as well. Control samples expressed unique proteins of 38, and 33 kDa. Non-radioactive proteins expressed under the same conditions as above, as well as natural field conditions, were tested for reactivity with antibodies to heat shock proteins (HSPs). HSP60 was the major protein found in L. virgulata. Although HSP47, HSP60, and HSP104 were present in all samples, the expression of HSP60 was enhanced in heat stressed colonies, while HSP47 and HSP104 expression were greatest in cold shocked samples. Inducible HSP70 was expressed in cold-shocked, heat-shocked, and field samples. Constitutively expressed HSP70 was absent from all samples. The expression of HSP90 was limited to heat shocked colonies. The expression of both HSP70 and HSP104 suggests that the organism may also develop a stress tolerance response.

Thyroxine and vitamin D in the gorgonian Leptogorgia virgulata

The gorgonian coral Leptogorgia virgulata contains thyroxine, or a thyroxine-like substance, referred to here as G-T 4. The G-T 4 levels were significantly higher in colonies collected in the summer vs. winter months. Using immunocytochemical techniques, G-T 4 was localized in the axis, polyp epithelium, and within the electron dense bodies of scleroblasts (spicule-forming cells), as well as on the periphery of spicules. G-T 4 was also localized in the mesoglea between closely adjacent scleroblasts. The effects of exogenous T 4 on the uptake of Ca 45 was determined in spicule, tissue and axis fractions of L. virgulata. The uptake of Ca 45 increased in T 4 treated spicules but decreased in the tissue fraction for all time periods tested. The uptake of Ca 45 into axes was not affected by exogenous T 4 until day 10 of the study. These data suggest that G-T 4 may function in the process of spicule formation. 1,25-dihydroxyvitamin D apparently is synthesized via ultraviolet radiation. Colonies deprived of ultraviolet radiation had significantly more ‘irregular’ spicules than colonies maintained in ultraviolet radiation. Exposure to sunlight therefore may be associated with the process of normal spicule formation.

Carbonic anhydrases in calcified tissues.

Precipitation of calcium carbonate (CaCO3) and calcium phosphate, especially hydroxyapatite [Ca10(PO4)6(OH)2] has been an important physiological reaction through the evolution. Carbonic anhydrase activity has been associated with the calcification process regardless of precipitating calcium salt. Precipitation of calcium carbonate is a fundamental process in many marine invertebrates, particularly in corals. Lucas and Knapp (1997) have demonstrated that carbonic anhydrase plays a pivotal role in the formation of calcitic sclerites of octocoral (Leptogorgia virgulata) regardless of the carbon source. Interestingly and comparably to mammalian cartilage calcification, Giraud-Guille (1984) has demonstrated that in addition to intracellular carbonic anhydrases it is possible that an extra-cellular carbonic anhydrase may have a role in the initiation of calcification in the crab cuticle. Acetazolamide was found to be inhibitory also in the formation of calcified spicules of developing sea urchin embryos (Mitsunaga et al., 1986). Recent study of Pedrozo et al. (1996) showed that carbonic anhydrase activity regulates precipation of calcium carbonate and mineralization of statoconia in Aplysia californica. These examples clearly demonstrates the essential role of carbonic anhydrase in the regulation of calcium carbonate precipitation in various biological systems. However, most dramatic demonstration of the role of carbonic anhydrase in biological calcification comes from the experiments where egg shell formation in birds has totally been blocked by carbonic anhydrase inhibitors (Benesch, 1984).

A physiological evaluation of carbon sources for calcification in the octocoral Leptogorgia virgulata (Lamarck).

The union of calcium cations with carbonate anions to form calcium carbonate (CaCO3) is a fundamentally important physiological process of many marine invertebrates, in particular the corals. In an effort to understand the sources and processes of carbon uptake and subsequent deposition as calcium carbonate, a series of studies of the incorporation of 14C-labeled compounds into spicules was undertaken using the soft coral Leptogorgia virgulata. It has been surmised for some time that dissolved inorganic carbon in sea water is used in the biomineralization process. Furthermore, it was suspected that metabolically generated CO2 is also available for calcification. As a means of testing these possible sources of carbon in spicule calcification, key enzymes or transport systems in each pathway were inhibited. First, the enzyme carbonic anhydrase was specifically inhibited using acetazolamide. Second, the active transport of bicarbonate was inhibited using DIDS (4,4'-diisothiocyanato-stilbene-2,2'-disulfonic acid). Third, CO2 generation resulting from glycolysis and the citric acid cycle was arrested using iodoacetic acid, which interferes specifically with the enzyme glyceraldehyde-3-phosphate dehydrogenase. The results indicate that dissolved CO2 is the largest source of carbon used in the formation of calcitic sclerites, followed by HCO3- from dissolved inorganic carbon. In L. virgulata, the dissolved inorganic carbon is responsible for approximately 67% of the carbon in the sclerites. The other 33% comes from CO2 generated by glycolysis. Two important conclusions can be drawn from this work. First, carbon for spiculogenesis comes not only from dissolved inorganic carbon in the environment but also from metabolically produced carbon dioxide. While the latter has been theorized, it has never before been demonstrated in octocorals. Second, regardless of the carbon source, the enzyme carbonic anhydrase plays a pivotal role in the physiology of spicule formation in Leptogorgia virgulata.

Biochemical characterization of purified carbonic anhydrase from the octocoral Leptogorgia virgulata

Carbonic anhydrase (CA) has been isolated and purified from the octocoral Leptogorgia virgulata (Lamarck) in an effort to investigate its role in the mineralization and demineralization of spicules and other calcified hard tissues. Affinity-chromatography using Prontosil-derivatized carboxymethylcellulose (CM) Bio-Gel A provided a one-step purification for 30 kdalton polypeptides with carbonic anhydrase activity. Four distinct polypeptides (designated α, β, γ, and δ) are separated from one another at this molecular weight by two-dimensional gel electrophoresis. The specific activity of the L. virgulata CA is on average 57.5±1.5 U g-1, is inhibitable by 10-6 M acetazolamide, and is unaffected by 5mM dithiotheitol. The amino acid composition of these polypeptides is similar to that of mammal, bird, reptile, fish and arthropod species. Antiserum made against the L. virgulata CA reacts specifically with the 30 kdalton polypeptides in western blots, and crossreacts with human CA I and II. Antiserum against avian CA II crossreacts with the L. virgulata 30 kdalton polypeptides. This is the first report of the characterization of a purified CA from an octocoral, and production of a CA antiserum to a species in the phylum Cnidaria.

Mechanisms of the Annual Cycling of Organic-Matrix Collagen from Spicules of the Gorgonian Leptogorgia virgulata

The insoluble organic matrix fraction from the spicules of the gorgonian Leptogorgia virgulata cycles annually. That is, in the summer, this fraction is predominantly collagenous while in the winter, collagen is largely absent. The mechanisms by which cycling occurs have been examined. It appears that spicules become etched and breaches form, probably via acidification and subsequent decalcification. Acidificationat the periphery of winter spicules, and presumably subsequent decalcification, has been verified using acridine orange. The internal organic matrix now becomes exposed to the hydrolytic action of such enzymes as acid phosphatase, which is secreted by secondary sclerocytes and scleroblasts. The digestive enzyme acid phosphatase has been localized throughout the year. In the winter, when the collagen content of spicules is lowest, there was strong labeling for acid phosphatase at the periphery of the spicules, suggesting that the enzyme may be involved in the removal of at least some portion of the organic matrix at this season. The level of enzyme activity in the polyps, heaviest in the fall and variable during the rest of the year, probably reflects seasonal changes in the productivity of the coastal waters in which the gorgonians live. Labeling for acid phosphatase was also strong in the winter in the cortical region of the axis. The enzyme may be digesting collagen that was transported to the axis. Labeling for acid phosphatase in the secondary sclerocytes was at a moderate level throughout the year. Additional key words: Cnidaria, octocoral, calcification, acid phosphatase, decalcification,

Seasonal localization of a collagenous protein in the organic matrix of spicules from the gorgonian Leptogorgia virgulata (Cnidaria: Gorgonacea)

Spicules of the gorgonian Leptogorgia virgulata possess an insoluble matrix fraction that is predominantly collagenous in summer months. This collagenous component is largely absent in winter months. Using an antibody directed against the 140 kD collagenous protein (CP) of the insoluble matrix, immuno-gold labelling was employed to localized this protein at the transmission electron-microscopy level throughout the year, and in different areas of the gorgonian colonies. Within the tip regions, the 140 kD CP varied throughout the year in the spicules, electron-dense bodies (EDBs) of scleroblasts, polyp vesicles, desmocytes and axes. In the mid and base regions, the 140 kD CP varied throughout the year in the spicules, EDBs and lysosomes of scleroblasts, desmocytes and axes. This variation in the location and density of the label suggests a dynamic annual cycling of the collagenous component of the insoluble matrix. EDBs may transport a collagenous component of the matrix to the spicule-forming vacuole. A component of the 140 kD CP may be transported and/or degraded by polyp vesicles and lysosomes, respectively. The pattern of labelling of the axial region suggests that translocation and storage of a component of the collagenous protein may occur. Environmental factors may be responsible for the triggering of matrix cycling.

Colony morphology, age structure, and relative growth of two gorgonian corals, Leptogorgia hebes (Verrill) and Leptogorgia virgulata (Lamarck), from the northerm Gulf of Mexico

Along the northeastern Gulf of Mexico coast, Leptogorgia hebes is the predominant gorgonian at two inner shelf (22 and 27 m) sites, while Leptogorgia virgulata dominates a third shallow (1–2m), inshore site. The axial skeleton of both species is composed of concentric rings which appeared to exhibit annual periodicity. Although age structure of the populations differed between shelf sites, neither colony growth rates, estimated from direct measurements of ring widths plotted on Walford graphs, nor overall branching complexity, determined from bifurcation ratios (Rb), differed between the shelf populations. Larger individuals at the 27m shelf site were simply older than those at the shallower (22m) shelf site. Walford plots of growth increments revealed colony growth of the shallow inshore species to be similar to that of the offshore species.

Emesis, learned aversion, and chemical defense in octocorals: a central role for prostaglandins?

Prostaglandin A2 and its ester derivatives comprise as much as 8% of the wet tissue weight of some octocoral species such as Plexaura homomalla (phylum Cnidaria, class Anthozoa, subclass Octocorallia). These high levels of prostaglandins, although initially palatable to fish, may function as defensive toxins by inducing emesis and learned aversions in potential predators. As the fish Fundulus heteroclitus and Halichoeres garnoti gain experience through the course of experiments, they increasingly reject foods containing emetic prostaglandins, but do not alter their acceptance of untreated control foods. Emesis is also induced in fish by consumption of tissue or lipid extracts from the subtropical whip coral Leptogorgia virgulata (subclass Octocorallia, order Gorgonacea). The emetic properties of L. virgulata induce learned aversions in the fish Micropterus salmoides and Morone saxatilis. Extracts of L. virgulata do not contain high levels of prostaglandins but do, however, contain other metabolites that appear to mimic the effects of eicosanoids. Some nonprostanoid secondary metabolites may induce emesis by stimulating prostaglandin biosynthesis in the gastric mucosa of predators.

Collagen in the Spicule Organic Matrix of the Gorgonian Leptogorgia virgulata

Decalcification of the calcareous spicules from the gorgonian Leptogorgia virgulata reveals an organic matrix that may be divided into water insoluble and soluble fractions. The insoluble fraction displays characteristics typical of collagen, which is an unusual component of an invertebrate calcium carbonate structure. This matrix fraction exhibits a collagenous amino acid profile and behavior upon SDS-PAGE. Furthermore, the reducible crosslink, dihydroxylysinonorleucine (DHLNL), is detected in this fraction. The composition of the matrix varies seasonally; i.e., the collagenous composition is most prevalent in the summer. These results indicate that the insoluble matrix is a dynamic structure. Potential roles of this matrix in spicule calcification are discussed.

The dynamics of spicule calcification in whole colonies of the gorgonian Leptogorgia virgulata (Lamarck) (Coelenterata: Gorgonacea)

The dynamics of calcification was examined in fractionated segments throughout entire colonies of the gorgonian Leptogorgia virgulata (Lamarck). The uptake of 45Ca, 3H-aspartic acid and 3H-thymidine was evaluated in isolated fractions including tissues, spicules and axes. Polyp number and distribution, axis weight and spicule type and size were also examined. The highest rates of uptake for all labeled materials were in the branch tips, indicating that the greatest degree of organic matrix formation, subsequent spicule formation and cell division occur in this apical region of the colony. Ca uptake decreased from the branch tips to the mid-portions of colonies, followed by an increase toward the bases. This latter rise in uptake is due to the increase in size and density of spicules which causes an increase in isotopic exchange. At branch junctions, the predominant cellular activity appears to be spicule formation vs. cell division. Axes of apical regions of branches displayed high rates of Ca uptake supporting its active role in the calcification process. The number and distribution of polyps, as well as spicule types, was variable among colonies indicating individual variability and/or the impact of varying environmental conditions. Data indicate that, although spicule formation occurs at its highest rate at branch tips, it occurs throughout the remainder of the colony as well.