Structure,iodination and growth of the axial skeletons of Muricea californica and M. fruticosa (Coelenterata: Gorgonacea)

Axial skeletons of two closely related, sympatric species of gorgonians were examined for details of gross morphology, internal organization and fine structure. Banded fibers with a periodicity of 430 Å and oriented circum-axially to the longitudinal axis of the skeleton (i.e., lying on the plane perpendicular to the axis), were revealed by electron microscopy in the axial skeleton of Muricea californica; they indicate the presence of a collagen-like protein in the gorgoin of this species. No circum-axial fibers were found in the axial skeleton of M. fruticosa. Differences in fine structure are related to gross morphological differences in the skeletons. A sequence of events for the addition of new material to the axial skeleton (growth) is described based on histological observation. Iodine-125 is used as a tracer for the deposition of new skeletal material, and is suggested as a new method for studying gorgonian growth rates.     

Chemical changes accompanying maturation of the connective tissue skeletons of gorgonian and antipatharian corals

The skeletons of 3 gorgonian and 2 antipatharian corals were subjected to quantitative chemical analysis. Protein values ranged from 70.4 to 93.6%; ash from 3.0 to 19.4%; lipid from 0 to 8.4%; carbohydrate from 1.24 to 3.94% and halogen from 4.2 to 24.9% of the dry skeletal weight. Hydroxyproline and phenolic values were 0 to 3.0% and 11.6 to 25.0% of the protein, respectively. Lipid, present in 2 gorgonian species and 1 antipatharian, significantly decreased with age in all three cases. Glucose and galactose accounted for over 90%, and sialic acids for an additional 1 to 10%, of the carbohydrate in the gorgonian skeletons studied; the glucose content of the gorgonian skeleton decreased with age. The antipatharian skeletons possessed no glucose or galactose, but contained significant levels of amino sugars; the presence of chitin is confirmed. In the gorgonians, bromine and iodine, the predominant halogens, increased with skeletal age and were present in nearly equal amounts. Small amounts of bromine were found in the antipatharian skeletons, but very large amounts of iodine were found in older parts of the skeleton. The basal regions of both antipatharian species contained >23% by weight of iodine, the highest content of iodine yet recorded for any organism.     

Skeleton and sclerite formation in the precious red coral Corallium rubrum

The carbonate skeleton of the gorgonian coral Corallium rubrum (L.) is composed of both a skeletal axis and numerous sclerites scattered in the mesoglea. Studies carried out on these skeletal elements and their associated tisues using microscopy and X-ray microanalysis, suggest a close relationship between the process of sclerite formation and skeletogenesis. The skeleton is surrounded by an axial epithelium composed of a single cell type. These cells associate intimately with mesogleal sclerites and scleroblasts, incorporating them into a nascent skeleton at the branch tip. Subsequent (sub-apical) growth appears to occur solely through the agency of the axis epithelial cells that serve to physically separate mesogleal sclerites and scleroblasts from contact with the axis. The epithelium is associated with the production of layered calcite crystals and irregular protuberances that constitute the mature, calcareous skeleton. Free sclerites in the mesoglea appear to be the product of multiple cells that are cytologically indistinguishable from those in the axis epithelium. Like the axis, sclerites are produced as layers of calcite crystals with irregular protuberances. The protuberances differ only slightly from those of the axis, and the skeleton is mineralogically indistinguishable from the sclerites. Thus, the skeleton of red coral is not primarily the product of fused sclerites. Instead, we suggest that the axis epithelium treats the incipient skeleton as if it were the core of a single sclerite, and conversely, that the mesogleal scleroblasts of C. rubrum constitute a fragmented axis epithelium.     

Calcium and magnesium carbonate concentrations in different growth regions of gorgonians

Four of the most abundant gorgonian species from the southwestern Cape waters, Eunicella papillosa (Esper, 1797), E. alba (Esper, 1797), E. tricoronata Velimirov, 1971 and Lophogorgia flamea (Ellis and Solander, 1786) were analysed for Ca and Mg by atomic absorption spectroscopy (AAS) and ethylenediaminetetraacetate (EDTA) titration. The total mineral content in the peripheral tissues, excluding the axial skeleton, expressed as the sum of CaCO₃ and MgCO₃ of dry matter was between 65.5 and 83.5%. The mineral content varied in different growth regions and all specimens showed a higher degree of mineralization at the base than at the branch tips. The MgCO₃ concentration varied with genus and species and was between 9 and 11 mol %. The variation of the MgCO₃ concentration within different growth regions of the same species was small and generally did not exceed 0.8 mol %. From the branch to the stem, CaCO₃ and total mineral content was found to increase. The CaCO₃:MgCO₃ rations in different growth regions of all species indicated that the composition of the mesoskeleton with regard to the relative concentration of CaCO₃ and MgCO₃ is constant throughout the animal. Mineralogically, the mesoskeleton consists of high magnesian calcite as identified by X-ray diffraction. MgCO₃ concentrations determined by the peak shift method and by AAS were in fair agreement. The MgCO₃ data in gorgonian samples from the cold Atlantic Ocean and the warmer Indian Ocean show a linear relationship between water temperature and MgCO₃ concentration already demonstrated by Chave (1954). However, our data were consistently lower by 1 to 2% than expected.     

Life history and viability of a long-lived marine invertebrate: the octocoral Paramuricea clavata

The red gorgonian Paramuricea clavata is a long-lived, slow-growing sessile invertebrate of ecological and conservation importance in the northwestern Mediterranean Sea. We develop a series of size-based matrix models for two Paramuricea clavata populations. These models were used to estimate basic life history traits for this species and to evaluate the viability of the red gorgonian populations we studied. As for many other slow-growing species, sensitivity and elasticity analysis demonstrate that gorgonian population growth is far more sensitive to changes in survival rates than to growth, shrinkage, or reproductive rates. The slow growth and low mortality of red gorgonians results in low damping ratios, indicating slow convergence to stable size structures (at least 50 years). The stable distributions predicted by the model did not differ from the observed ones. However, our simulations point out the fragility of this species, showing both populations in decline and high risk of extinction over moderate time horizons. These declines appear to be related to a recent increase in anthropogenic disturbances. Relative to their life span, the values of recruitment elasticity for Paramuricea clavata are lower than those reported for other marine organisms but are similar to those reported for some long-lived plants. These values and the delayed age of sexual maturity, in combination with the longevity of the species, show a clear fecundity/mortality trade-off. Full demographic studies of sessile marine species are quite scarce but can provide insight into population dynamics and life history patterns for these difficult and under-studied species. While our work shows clear results for the red gorgonian, the variability in some of our estimates suggest that future work should include data collection over longer temporal and spatial scales to better understand the long-term effects of natural and anthropogenic disturbances on red gorgonian populations.     

Submersible and laboratory observations on Asteroschema tenue,a long-armed euryaline brittle star epizoic on gorgonians

In situ and laboratory obervations of the biology and behaviour of the deep-sea, euryaline brittle star Asteroschema tenue Lyman, from Jamaica, are described. The brittle star is found clinging to the gorgonian Ellisella barbadensis at depths of 168 to 230 m off Jamaica, and is here restricted to this gorgonian. The brittle star, which is usually cryptically coloured, is active principally nocturnally, when it extends arm loops and employs the tube feet for microphagous filter-feeding. Locomotory activity is limited to extension and retraction along the gorgonian, achieved by means of unusual arm-loop patterns. Association with a gorgonian appears to be essential for the survival of the brittle star. The study was conducted in 1985.Order of authors' names is arbitrary     

Antimicrobial activity of extracts of Caribbean gorgonian corals

Extracts of 39 species of Caribbean gorgonians were tested for antimicrobial activity against 15 strains of marine bacteria. The bacteria consisted of three opportunistic pathogens, Vibrio parahaemolyticus, Leucothrix mucor, and Aerococcus viridans, and 12 strains isolated from either healthy or decayed gorgonians. Overall, only 15% (79 out of 544) of the tests resulted in antibacterial activity with 33% (13 out of 39) of the gorgonians inhibiting only one bacterial strain and 23% (9 out of 39) showing no activity. The extracts of four Pseudopterogorgia species showed relatively high levels of activity, inhibiting 43 to 86% of the bacterial strains. The potency of the active Pseudopterogorgia species was variable, however, and three additional Pseudopterogorgia species were inactive against all bacterial strains. With the exception of one sensitive strain, Vibrio species were resistant to gorgonian metabolites. Our results indicate that organic extracts of most Caribbean gorgonians do not possess potent, broad-spectrum antibacterial activity inhibitory to the growth of opportunistic marine pathogens and bacteria associated with healthy and decayed gorgonian surfaces. These findings suggest that the inhibition of bacterial growth is not the primary ecological function of gorgonian secondary metabolites and that bacteria may not be important selective agents in the evolution of gorgonian secondary chemistry.     

Development of a new standardised method for sustainable monitoring of the vulnerable pink sea fan Eunicella verrucosa

The aim of this survey was to test a standardised method to follow the demographic evolution of a dense aggregative ‘forest’ population of the temperate gorgonian Eunicella verrucosa (Octocorallia, Gorgoniidae) using in situ photographic recordings. Distribution, density, growth and demographic evolution of the colonies was compared along two parallel transects. Computer treatment allowed the estimation of the total branch fan surface area, and the individual growth of tagged colonies was determined by measuring the increase in this surface area, using consecutive photographs taken at two-year intervals. To integrate the potential bias of branch overlapping, we proposed a correction factor between the in situ photographic surface area and the surface area of the gorgonian calculated from ex situ photographic surface area with all branches deployed. The surface-frequency distribution of colonies was converted to estimated-age-frequency distribution using an estimated growth curve based on the net growth rate. The technique used revealed significant differences in population structure and the dynamics of gorgonian colonies, as the two transects appeared to be influenced by different environmental conditions. The recruitment also seemed to vary according to year and transect, resulting in different densities. Our work showed clear results in characterising the variations of gorgonian demographic evolution at a small spatial scale; thus, it is assumed that this method could be a sustainable tool for coastal environmental managers.     

The collagenous nature of problematical ligaments in crinoids (Echinodermata)

A major adaptive problem among comatulid crinoids is the need for a system of articulation and muscularization of the skeleton which provides rigidity in the cirri, arms, and pinnules for maintaining position and feeding in moving water masses, and also the ability to undergo occasional rapid flexions. Most skeletal ossicles of comatulids are united by so-called ligament fibers, while arm articulations possess masses of muscle as well as ligament. Light and electron microscopic work shows that the ligament consists primarily of collagen fibers. Similarity of this dual system of crinoid arm musculature to the muscles and collagenous catch apparatus of echinoid spines suggests that the crinoid ligaments may provide the needed rigidity to the crinoid skeleton, in a manner similar to that by which the echinoid catch apparatus can hold the spine tightly to the test in one position.     

Linking local to global properties in branching modular networks: gorgonian coral colonies

Branching growth is present both in plants and animals, either marine or terrestrial. Although cellular and other modular levels of organization in plants and animals have evolved through different molecular and physiological mechanisms, several aspects of their branching modular system and morphology are similar. We studied vessel organization and colony integration, in order to comprehend underlying relationships between different structural components in a gorgonian coral network. The theoretical formalism was validated in the gorgonian coral Eunicea mammosa (Plexauridae, Octocorallia) in Belize. As in vascular plants, these colonial animals create a complex network of connections among modular branches integrated in stem canals downstream toward the base. A new formalism is proposed for describing gorgonian branching. A global property of a colony is for instance the size of its base or its weight whereas a local property is the size of branch in a particular place of the colony. However, a global property is not the simple addition of local modular properties, as the case of stem canals in the colony base. Theoretically, the process of branching is tightly intertwined with the internal network organization. The colony network centralization is driven by a linear relationship between the total number of branches and the stem canals at the base of the colony. If stem canals play important roles in the transport of nutrients throughout the colony and the biomechanical support from the base up to the tips, we can assume that there is an underlying association between the number of stem canals at the base and the number of for example, terminal branches. These associations may provide new findings that extend our understanding of the functional organization of tree-like networks in octocorals and their vascular systems. The idea that the external components of a tree-like plant network are directly correlated and connected down to the main trunk seems to be analogous in an animal system.     

Chemical resistance of gorgonian corals against fungal infections

The frequency and impact of diseases affecting corals throughout the Caribbean have been increasing but little is known about the factors promoting the emergence and outbreak of disease. A disease caused by a fungal pathogen [Aspergillus sydowii (Thom et Church)] which affects Caribbean sea fan corals provided an opportunity to examine the efficacy of coral crude extracts in disease resistance. Minimum inhibitory concentration (MIC) assays showed that of the 20 common gorgonian species in the Florida Keys, extracts from 15 species had MICs < 15 mg ml⁻¹ against A. sydowii pathogenic to sea fans. Extracts from several species in two gorgonian genera (Pseudoplexaura and Pseudopterogorgia) were among the most active, with MICs < 10 mg ml⁻¹. Gorgonia ventalina L., one of two sea fan species known to be hosts to A. sydowii in the field, had an MIC < 10 mg ml⁻¹, suggesting that complete disease resistance requires more active extracts. For the antifungal compounds to be effective in situ, they must also occur in sufficiently high concentrations in living coral tissue. For example, Pseudopterogorgia americana (Gmelin) had comparatively potent extracts but did not have sufficient concentrations in the tissue to be effective. Conversely, Plexaura homomalla Esper extracts were less potent but occurred in high enough concentrations in the tissue to be effective against A. sydowii. When potency and extract concentration are considered together (i.e. potency × concentration), several other gorgonian corals emerge as likely hosts to A. sydowii. Crude extracts from the most active gorgonian species were also effective against two geographic variants of A. sydowii pathogenic to sea fans, a non-pathogenic terrestrial strain of A. sydowii, and three strains of A. flavus Link known to be human, plant, and insect pathogens (MIC range, 7.5 to > 15 mg ml⁻¹). Although the potency in these assays did not attain a clinically significant level, the potency is comparable to a known antifungal agent, hygromycin B, which had an MIC ≤7.5 mg ml⁻¹ in our assays, highlighting the potential of these gorgonian corals for bioprospecting. Received: 29 May 1999 / Accepted: 22 May 2000     

Studies on reef corals. III. Fine structural changes of calicoblast cells in Pocillopora damicornis during settling and calcification

The site of reef-coral calcification has been studied in the branching coral Pocillopora damicornis Lamarck. Electron microscopy and X-ray microprobe analysis were performed on the calicoblast epidermis of newly settled larval stages and of adult coral. During settling, the heterogeneous columnar cell composition of the planktonic larva epidermis is replaced by a simple epithelium consisting of a single cell type, the calicoblast cell. Metamorphosis appears tightly linked to settling, with cell changes occurring within hours after attachment, and is marked by the appearance of a new secretory cell. The calicoblast cell of the adult coral is extremely flattened, and interdigitates extensively with adjacent calicoblast cells. This cell possesses a featureless plasma membrane lacking microvilli or flagella. It characteristically contains large membrane-bound vesicles with homogeneously fine granular contents. Preliminary microprobe analysis indicated a higher calcium content in these vesicles than in surrounding tissue; however, not in concentrations suggesting calcium-carbonate precipitation. They may represent sites of organic matrix synthesis. The calicoblast epidermis is separated from the underlying coral skeleton by a narrow gap. This gap appeared devoid of substructure, either organic or inorganic. The coral soft tissues are attached to the skeleton by mesogleal attachment processes, the desmoidal processes. These consist of a complex fibrous network originating in the mesoglea, and inserting onto the skeleton via specialized attachment regions consisting of electron-opaque membranous plaques. Skeletogenesis in reef-corals probably occurs extra-cellularly, external to the calicoblast epidermis, by simple overgrowth of the skeleton.     

Possible control mechanism of cell motility in the gorgonian Eunicella cavolinii

In a previous study it was demonstrated that a lectin controls cell-cell interaction in the gorgonian Eunicella cavolinii (Koch) as a negative modulator. Now we describe the procedure to purify this lectin to homogeneity; its molecular weight is 23 400. The homologous proteoglycans were identified as positive modulators of cell-cell (and/or cell substrate) interaction. The purified single proteoglycan aggregates were 1200±700 nm long and the distance between the attachment points of the proteoglycan subunits was about 45 nm. The glycosaminoglycan residues of the gorgonian proteoglycans were identified as hyaluronic acid (35.5%), heparan sulfate (47.9%) and dermatan sulfate (14.1%). Binding studies with immobilized homologous proteoglycan preparations revealed that gorgonian cells attach to this substratum presumably via its glycosaminoglycans. Quantitative determinations of these two modulators of cell-cell recognition in the three regions of individual colonies revealed concentration gradients these concentration differences reflect a lower cell motility in the polyp-bearing branches and a higher motility of the cells in the polyp-free stem and in the basis, is discussed.     

Extension rate: A primary control on the isotopic composition of West Indian (Jamaican) scleractinian reef coral skeletons

Large variations in skeletal microarchitecture, and in the carbon and oxygen isotopic composition of the skeleton, exist within single calices and over the surfaces of single colonies of various species of West Indian (Jamaican) scleractinian reef corals. Rapidly extending parts of individual colonies are depleted in both C¹³ and O¹⁸ regardless of the abundance of zooxanthellae in the overlying tissues. We suggest that this relationship is due to active translocation of organic compounds to sites of rapid calcification. Considerable variation in isotopic composition is found in skeletons of different specimens of the same species even when the skeletons are sampled in a consistent manner, come from the same locality and depth, and have a comparable growth history. The isotopic composition of the scleractinian skeleton is vastly more complex than has heretofore been realized.     

Comparative biometry of Eunicella singularis (Gorgonian) sclerites at East Mediterranean Sea (North Aegean Sea, Greece)

The two forms of Eunicella singularis sclerites, spindles and clubs, were examined in two sites in East Mediterranean Sea, Greece. The comparison of the sclerites size was based on the hydrodynamic profile of the sites (the site of Arethoussa was exposed and the Phidonissi site was sheltered), on the sites bathymetry (AR 5–8 m, AR 9–13 m, PH 5–10 m, PH 11–13 m) and on the position occupied by the sclerites on the gorgonian colonies (top, middle and base). With the usage of image system analysis the following microfeatures were measured or calculated: projection, length, width, elongation factor, compactness factor, length × width and length/width. The present study confirms the hypothesis that spindles are involved in the recovering of the gorgonian colonies and clubs contribute to the flexion capacity of the colonies. The spindles of the shallow E. singularis colonies (AR 5–8 m) were significantly bigger (length, width) compared with the others, in order to assure the best recovery of the colonies after their flexion, induced by higher water current velocity in shallow water. The clubs occupy the intern part of the mesoglea and their size (length, width) increased in colonies from the shallow exposed site in order to facilitate the gorgonian flexion. The present study demonstrates the gorgonian adaptation (in a microscopic scale) to the environmental pressure of hydrodynamic conditions.     

Cryopreservation of the dinoflagellate symbiont of the octocoral <Emphasis Type="Italic">Pseudopterogorgia elisabethae</Emphasis>

In this paper we describe a cryopreservation protocol followed by the culture of Symbiodinium sp. isolated from the Caribbean gorgonian Pseudopterogorgia elisabethae as a potential renewable source of the dinoflagellate symbiont. Four different freezing protocols were designed: a controlled cooling device designed to cool at 1°C/min, a three-step protocol (−20°C for 2 h, −70°C for 2 h, liquid nitrogen-LN₂), a two-step protocol (−70°C for 2 h, LN₂), and a one-step protocol (LN₂). All cells were stored in LN₂ after cryopreservation. The cryoprotective agents (CPA) used were ethanol (EtOH) and methanol (MeOH) at 10 and 20%, and seawater (FSW) was used as a control. Viability measurements using cell counts showed that all cryopreservation protocols were relatively successful, and no trends were observed regarding freezing protocol or CPA used. After 19 weeks in culture the viability of samples which had high biomass was determined by the fluorescent assay CellTiter Blue™. The most viable cultures were those cryopreserved by a two-step protocol using 20% MeOH or 20% EtOH as a CPA. A genetic examination of the DNA of these samples using Symbiodinium-specific PCR primers confirmed that the composition of the culture had not changed. For the first time, we report that Symbiodinium sp. isolated from a gorgonian can be cryopreserved and subsequently cultured successfully. Lory Z. Santiago-Vázquez and Nealie C. Newberger contributed equally to this publication.     

Net negative growth detected in a population of <Emphasis Type="Italic">Leptogorgia sarmentosa</Emphasis>: quantifying the biomass loss in a benthic soft bottom-gravel gorgonian

Gorgonian species may contribute to the three-dimensional seascape in soft bottom-gravel areas, but the information on their biology and ecology is very scarce. The biometry and secondary production of the Mediterranean soft bottom-gravel passive suspension feeder Leptogorgia sarmentosa (Cnidaria: Octocorallia) was studied using photographic monitoring of the primary branches from May 1998 to September 2000. The primary branches observed had a high density of polyps (2.2 ± 0.2 SD polyps mm⁻¹) and a high organic matter content (63.2 ± 9.1 SD %). During the two-year sampling period, there was a net negative growth in 90% of the gorgonian population. The mean loss during the 27-month period was −2.9 ± 0.9 SD cm per branch (5.7 mg C branch⁻¹). However, considering only the initial and final diameters and maximum height in the 27 months elapsed time, the gorgonians showed positive growth, which meant that photographic sampling of single branches was a more appropriate method for gorgonian secondary production monitoring. A water mass anomaly detected in 1999 in the north-western Mediterranean Sea may have been the cause of the net negative growth in L. sarmentosa in the studied area. Partial mortality due to different factors, such as strong currents, predation, disease, etc., could be a common strategy in sessile colonial benthic populations that would facilitate their maintenance even during very stressful circumstances.     

Spatial variability in reproductive cycle of the gorgonians <Emphasis Type="Italic">Paramuricea clavata</Emphasis> and <Emphasis Type="Italic">Eunicella singularis</Emphasis> (Anthozoa,Octocorallia) in the Western Mediterranean Sea

Paramuricea clavata (Risso, 1826) and Eunicella singularis (Esper, 1794) are the most representative gorgonian species in hard bottoms sublittoral communities in the Western Mediterranean Sea. Reproductive cycles of two populations of both species were studied in two distinct locations approximately 600 km apart (Medes Islands and Cape of Palos), in order to assess interpopulation variability on a relevant geographic scale. Seasonal variation of lipid concentration levels in the gorgonian tissue was used as a tool to quantify energy storage by each studied population in order to explain possible interpopulation differences in gonadal output. Sex ratio in Medes Islands populations of both species was 1:1, while in Cape of Palos sex ratio was significantly male biased (1:7) in P. clavata, and female biased (1.7:1) in E. singularis populations. Spawning timing occurred in all cases coinciding with a marked increase in sea-water temperature in spring, and after the most successful feeding season, but comparing localities there was a clear temporal shift in the time of gametes release, appearing well linked to the shift in sea-water temperature rising in spring in both sites at the depth where populations are placed. Therefore, in this study the temperature appears as the main synchronizing factor of gonadal development within these populations. Significant differences in gonadal volume per polyp were found in both species owing mainly to differences in the number of gonads per polyp between populations, with Cape of Palos populations displaying higher values in both studied species, suggesting that the exposition to different local conditions may be reverted in a different gonadal output. But the observed patterns in lipid concentrations levels in gorgonians disable us to conclude that lipid concentration levels explain the observed differences in gonadal output found in this study.     

Micromorphology and ultrastructure of Caribbean sclerosponges

Fine structural analysis of living tissue of the sclerosponges Ceratoporella nicholsoni (Hickson) and Stromatospongia norae Hartman, collected near Discovery Bay, Jamaica, between 1984 and 1986, was carried out using transmission and scanning electron microscopy (TEM and SEM). The thick dermal membrane of these sponges is covered by exopinacocytes having a T shape in sections perpendicular to the surface. A dense, complex glycocalyx is produced at the surface of these cells. Choanocyte chambers are diplodal and unusually small. The inhalant and exhalant canals of both species are characterized by the presence of valvules, made by transverse lamellipodial processes of the endopinacocytes lining them. An abundant and diversified bacterial community occupies almost 20% of the mesohyl. A single layer of active basopinacocytes lines the mesohyl at the interface between the living tissue and the aragonitic skeleton. Basopinacocytes are presumed to be precursors of the irregular fibrillar organic matrix found in the aragonitic skeleton. Sclerocytes and spongocytes are abundant in the vicinity of the siliceous spicules. Typical lophocytes releasing smooth collagen fibrils are common in the dermal membrane as well as in the choanosome where they can be grouped in bundles. Uniquely, C. nicholsoni elaborates rough intercellular fibrils characterized by periodically spaced thickenings. The endolithic algae Ostreobium sp. is present in the most apical zones of the aragonitic skeleton, but does not seem to interfere with its development. The striking micromorphological resemblances between both species are discussed and compared to demosponges.Contribution no. 472 from the Discovery Bay Marine Laboratory, University of the West Indies, Discovery Bay, Jamaica, West Indies     

Sexual reproduction and external brooding by the Caribbean gorgonianBriareum asbestinum

The reproductive biology of the gonochoricBriareum asbestinum (Pallas), a common Caribbean gorgonian, was studied in the San Blas Islands (Panama), La Paguera (Puerto Rico) and the Bahamas. Of 721 colonies examined at the height of the reproductive season, during the summers of 1985 to 1988, all were either male or female. No hermaphroditic colonies or polyps were observed. The sexratio of Panama populations was significantly biased in favor of males (2.1:1,n=454) over all four years of the study. A significant male bias was also found in populations sampled in Puerto Rico (2.3:1,n=143) and in the Bahamas (2.5:1,n=124). The consistency of this geographically widespread skewed sex-ratio is unique among octocorals and scleractinians. Ooyctes appear annually in September and reach maximum diameter (600 to 900µm) in June and July of the following year. The 3 to 5 mo developmental cycle of spermaries is shorter than that of females and begins in March. Spawning in males is synchronous and occurs following the full moons of June and July. Fertilization is internal. Embryos are released from polyps very early in development, often whilst still in the process of cleaving. Embryos remain attached to the outside of the colony for 3 to 5 d, many becoming entrapped in mucous sheets secreted by the colonies. Larvae are negatively buoyant and settle rapidly once displaced from the colony. Males become reproductive at smaller branch sizes than females. Reproductive effort (gonads polyp^–1 and total gonad volume polyp^–1) for both males and females increased with increasing branch size and in polyps away from the tip and base of the branch.Please address all correspondence and requests for reprints to Dr Brazeau at his present address: Department of Biology, University of Houston, Houston, Texas 77204-5513, USA