New epizooic symbioses between sponges of the genera Plakortis and Xestospongia in cryptic habitats of the Caribbean

Three new cases of sponge symbiosis between species of Plakortis and Xestospongia were found in reef caves and mesophotic reef habitats of the Caribbean. Plakortis sp. 1 from the Bahamas associates exclusively with Xestospongia deweerdtae which was originally described living freely on the deep fore-reef and caves of Jamaica. In addition, we found Plakortis sp. 2 from Puerto Rico which associates with both X. deweerdtae and a different Xestospongia sp. Sponge specimens were identified using cytochrome oxidase subunit 1, 28S rRNA and 18S rRNA gene sequence fragments, spicule analysis, and histological sections with SEM. Unlike previous sponge pairs, Xestospongia spp. not only grew as a thin veneer of tissue over the Plakortis host sponge but through the mesohyl, forming inner channels (0.1–1 cm) that may provide a benefit by facilitating more efficient water transport through the dense Plakortis tissue. Symbioses with both Plakortis spp. were documented from an early recruit stage through adulthood. Spicule measurements conducted on symbiotic versus free-living X. deweerdtae revealed significantly smaller spicule sizes for symbiotic individuals, suggesting a cost in terms of silicon availability, or a benefit in terms of a lower investment in skeleton synthesis for support. This study reveals new specialized symbiotic associations between distantly related sponge genera that likely represent an alternative strategy of adaptation for life in reef caves and mesophotic reefs.     

Biochemical genetic evidence for a third species of Metridium (Coelenterata: Actiniaria)

Fine-structural analysis of the tissues of the marine demosponge Callyspongia diffusa was carried out using scanning electron microscopu and ethanol cryofracture. Micrographic data reveal the pathway of water movement through the sponge, and allow accurate measurement of the dimensions of successive structural filters in the aquiferous system. Understanding the organization and cytoarchitecture of the normal tissues of this sponge provides a basis for comparison where histopathology is being investigated, e.g. in allograft rejection reactions.     

Isolation of a new toxin from the sponge Latrunculia magnifica in the Gulf of Aquaba (Red Sea)

The sponge Latrunculia magnifica was found to be toxic for fish. A toxin has been isolated from this sponge by organic extraction-column chromatography and thin-layer chromatography. Several chemical properties of the toxin were determined by spectroscopic analysis. Toxicity tests were performed on the fish Gambusia affinis. In vitro experiments showed the toxin to be a cholinesterase inhibitor.     

A brominated secondary metabolite synthesized by the cyanobacterial symbiont of a marine sponge and accumulation of the crystalline metabolite in the sponge tissue

The dictyoceratid marine sponge Dysidea herbacea (Keller, 1889) is common in shallow waters of the tropical Pacific Ocean. Polybrominated biphenyl ethers such as 2-(2,4-dibromophenyl)-4,6-dibromophenol (1) are characteristic secondary metabolites of some specimens of this sponge and may represent as much as 12% of the dry weight. We have found 1 to be deposited as conspicuous crystals throughout the sponge tissue. The dominant prokaryotic endosymbiont in the mesohyl of the sponge is a filamentous cyanobacterium (Oscillatoria spongeliae), although a vacuole-containing, heterotrophic bacterium is also present. The cyanobacteria were separated from the sponge cells and heterotrophic bacteria by flow cytometry. Coupled gas chromatography—mass spectrometry and proton nuclear magnetic-resonance spectroscopy revealed that the major brominated Compound 1 isolated from the intact symbiotic association is found in the cyanobacteria and not in the sponge cells or heterotrophic bacteria. This suggests that the production of the compound is due to the cyanobacterium, and not to the sponge or symbiotic heterotrophic bacteria, as had been suggested earlier.     

Contribution of morula cells to allogeneic responses in the colonial urochordate Botryllus schlosseri

Morula cells (MCs), ubiquitous ascidian cells which participate in alloimmune reactions, were studied in allogeneic and xenogeneic assays performed with Botryllus schlosseri (Pallas, 1766) colonies from the Mediterranean and the Pacific coast, USA. Experiments were performed on the morphological level, on blood cells sampled or vitally labeled in situ and on histological sections. In non-interacting B. schlosseri during blastogenic cycles A to C, MCs congregate in tentacles of the zooids' siphons. During the takeover phase of blastogenesis they disappear, appearing again in the siphons of the newly developed generation of zooids. In both compatible and incompatible allogeneic reactions their numbers in interacting ampullae increased fourfold within 2 h after first contacts, reaching up to 50% of the total blood-borne cells in ampulla lumens. In rejection processes most of these cells died, while in autologous or allogeneic fusions they disappeared from interacting ampullae within days of the reaction. During allogeneic rejections, we followed cases (up to 1 week) in which MCs crossed all morphological/physiological barriers between noncompatible colonies and entered the tunic matrices and blood systems of the interacting partners, forming successful microchimerism. In xenogeneic assays with Botrylloides sp., MCs concentrated at the xenogeneic boundary, but they never crossed into the other species. One week after fusion or rejection interactions, large numbers of macrophages clearing dead cells were found in contact areas. This is the first evidence for compartmentalization of specific cellular defense reactions in the tunicate circulatory system. Received: 23 October 1997 / Accepted: 17 February 1998     

Ecology of the northern Red Sea crinoids and their Epi- and Endozoic fauna

Fourteen crinoid species are found along the coral reefs of the northern Red Sea that form aggregations of different species at various depths. The shallowest aggregation consists partly of Lamprometra klunzingeri and Capillaster multiradiatus, occurring subtidal to a depth of 2 to 5 m. Of this group, Heterometra savignii inhabits depths down to 12–15 m. Further down, another group of 10-armed crinoids occurs, dominated by Decametra chadwicki and Oligometra serripinna. The deepest aggregation of crinoids occurs at 45 m; its most common members are Colobometra arabica and Comaster distinctus. Feeding on micro- and nanoplankton, shallow-water crinoids show a circadian activity rhythm; in deeper aggregations (10 to 12 m), this behaviour changes with decreasing illumination, to a diurnal activity rhythm. The symbiotic animals living on crinoids comprise 27 taxons, among them Copepoda (6 species), Mollusca (2 species), Polychaeta (11 species, especially Myzostomida); Ophiurida (1 species), Crustacea, Decapoda (6 species); and the clingfish Lepadichthys lineatus. These symbiotic animals form food webs at various depths, according to the distribution of their crinoid host. The occurrence of Indo-West Pacific and Mediterranean commensals on the same crinoid in the Gulf of Aqaba is of special interest.     

Neoplasia,regeneration and growth in the reef-building coral Acropora palmata

Abnormal processes of calcification, such as regenerating lesions and neoplasia, situated near the tips(<25 cm) of colonies of Acropora palmata (Lamarck) suppressed normal linear growth. Branches having neoplasia at a larger distance from the tip do not grow significantly differently from controls. This indicates a functional minimal area in terms of energy supply. Neoplasia are pure aragonite and have the same coenosteal structure as regenerative skeletal material. Regeneration of tissue as well as tissue+skeleton lesions involves the simultaneous formation of tissue and regenerative skeleton, trapping foreign material under the regenerated surface. Recovery of a damaged surface slows down with time and this may, in other coral species, result in permanent lesions. A. palmata recovered from all lesions (n=32) within 80 d and appears to be a superior regenerator among Caribbean corals. This is consistent with other life-history characteristics of this highly specialized coral species.     

Exudation of biologically-active metabolites in the sponge Aplysina fistularis

Specimens of the demosponge Aplysina fistularis forma fulva (Pallas) from the intertidal zone at La Jolla, California, USA, contain two antimicrobial metabolites, aerothionin (1) and homoaerothionin (2). Both metabolites are exuded into seawater. The rates of exudation into artificial seawater were measured under near in situ conditions (7.7x10^-4 g aerothionin min^-1 g^-1 dry weight of sponge) and in an aquarium (8.9x10^-3 g min^-1 g^-1) for undamaged sponges. Sponges responded to a simulated injury by exuding 10 to 100 times as much of these metabolites. The exudation of aerothionin and homoaerothionin may inhibit surface overgrowth by fouling organisms and tissue damage by mobile animals.Please address requests for reprints to Dr. J. E. Thompson     

Biochemical and fine structure evidence for cellular specialization in a large spumellarian radiolarian Thalassicolla nucleata

Thalassicolla nucleata is a skeletonless, large spumellarian radiolarian (ca 3 mm diameter) occurring abundantly in the surface water of the Sargasso Sea. It has a complex cellular organization consisting of (1) a well-defined central capsule surrounded by a non-living capsular wall perforated by numerous cytoplasmic strands and (2) an extracapsulum containing a frothy layer of alveolate cytoplasm penetrated by numerous rhizopodia. Evidence is presented for physiological specialization complementing this structural compartmentalization. Acid acryl phosphatase activity (a digestive vacuole marker enzyme) is approximately 3 times greater in the extracapsulum compared to the intracapsulum; whereas, cytochrome oxidase (a respiratory marker enzyme) is approximately 1.5 times greater in the intracàpsulum compared to the extracapsulum. Furthermore, cytochemical and electron microscopic evidence indicates that the extracapsulum, containing large vacuoles and copious amounts of acid phosphatase reaction product, is a major site of catabolism; while the intracapsulum, containing the nucleus, numerous Golgi bodies, and a rich supply of mitochondria, is a substantial site of anabolism, lysosomal secretory activity, and food product storage. This marked level of cellular specialization in T. nucleata may enhance its biological efficiency and thus partially account for its abundance in oligotrophic environments.     

Dimethyl disulfide and dimethyl trisulfide: so similar yet so different in evoking biological responses in saprophilous flies

Dimethyl disulfide (DMDS) and dimethyl trisulfide (DMTS) are used by saprophilous insects to locate breeding sites (decaying organic matter), and by brood-site deceptive flowers to attract such insects. However, little is known about the relative importance of these two compounds in eliciting electrophysiological and behavioral responses in the insects. Here, we compared the relative attractiveness of DMDS and DMTS to saprophilous flies in field choice experiments and tested whether potential differences in field responses can be explained by differences in electrophysiological antennal responses to these compounds. Field experiments revealed that the attractiveness of a mixture of these compounds is due to DMTS alone. This result was confirmed by electroantennographic recordings in which flies of four tested species of Calliphoridae (Lucilia sericata, L. caesar, Calliphora vicina, Protocalliphora azurea) and one Muscidae (Musca domestica) respond clearly to DMTS, but not to DMDS. In house flies, however, DMTS elicited electrophysiological responses only, not reflected in behavioral assays. Despite the fact that DMTS and DMDS exhibit similar chemical structures, both the electroantennographic and field responses from saprophilous flies to these two compounds strongly differed. Our study suggests that oligosulfide-responsive saprophilous flies rely on DMTS and not DMDS for finding appropriate breeding sites and that DMTS and not DMDS could act as a key mediator for pollinator attraction in brood-site deceptive plants.     

Biochemical genetic divergence and systematics in sponges of the genera Corticium and Oscarella (Demospongiae: Homoscleromorpha) in the Mediterranean Sea

The sponge sub-class Homoscleromorpha is generally considered to include just two families, the Oscarellidae (without spicules) and the Plakinidae (with simple spicules). In May 1990, an unusual sponge was found deep inside a submarine cave in the western Mediterranean Sea. On the basis of externally visible characters this sponge appeared indistinguishable from the common plakinid species Corticium candelabrum Schmidt, 1862. However, on closer examination in the laboratory the new sponge proved to be devoid of spicules. Therefore, despite great morphological similarities to C. candelabrum, the new sponge should, by taxonomic convention, have been placed in the Oscarellidae. On the basis of other criteria, the similarities to C. candelabrum were great and the new sponge was at first considered to be conspecific. Thus, the taxonomic position of the new sponge and its relationship to C. candelabrum are highly confusing. It could be an aspiculate morph of C. candelabrum, or a new and undescribed related species or, lacking spicules, it could justifiably be placed in a different family (Oscarellidae). The relationship of the new sponge to C. candelabrum and also to two species of Oscarella (Oscarellidae) was assessed by the use of enzyme electrophoresis to estimate genetic divergence between species. It was found that the new sponge was reproductively isolated from sympatric C. candelabrum, with 6 of 16 loci proving diagnostic. Thus it is clear that the new sponge belongs to a different biological species. Surprisingly it was also found that, although this new species was fairly closely related to C. candelabrum (level of genetic identity, I0.47), the two Oscarella species were similarly closely related to C. candelabrum (I0.31 to 0.41) and rather less closely to the new species (I0.17 to 0.28). Indeed from genetic identity estimates, O. tuberculata is more closely related to C. candelabrum than it is to O. lobularis. It is concluded that all homoscleromorph sponges should be placed in the single family Plakinidae.     

Location of toxicity within the Mediterranean sponge Crambe crambe (Demospongiae: Poecilosclerida)

Within-specimen location of toxicity in Crambe crambe (Schmidt) has been addressed by complementary procedures on specimens collected in north-east Spain (Western Mediterranean) in winter of 1993. The toxicity of the distal (ectosome) and basal (choanosome) sponge parts have been analysed and the main cellular types present in these two layers have been studied by light and electron microscopy. The toxicity of the three main cell types, separated by the gradient-density method, has also been analysed. Three main fractions, each of them enriched in a different cellular type, were obtained: Fraction 1 (interface between 2 and 5% Ficoll) contained 90±0.9% (mean±SE) of spherulous cells and 10% of different cell types consisting of choanocytes (5±0.54%), and unidentified cells or cell debris (5±0.84%); Fraction 2 (interface between 5 and 8% Ficoll) was enriched in choanocytes (70±0.95%), and also contained spherulous cells (11.8±0.73%), archeocytes (6.2±0.74%) and unidentified sponge cells (12±0.74%); Fraction 3 (interface between 8 and 11% Ficoll) mainly consisted of archeocytes and archeocyte-like cells (75±0.66%), together with spherulous cells (7±0.74%) and other unidentified sponge cells and cell aggregates mainly formed by choanocytes (18±0.41%). Toxicity [measured in toxicity units, TU, using the Microtox^® procedure] was significantly higher in the sponge ectosome (12.45±1.4 TU) than in the choanosome (2.58±0.92 UT). Only the abundance of spherulous cells in the sponge tissues correlated well with the pattern of toxicity observed, and this was corroborated by the toxic behaviour of the three cellular fractions obtained: the one enriched in spherulous cells was highly toxic (9.08 UT), whereas those enriched in choanocytes and in archeocytes were almost inactive (0.48 UT) or totally innocuous, respectively. All these results point to the spherulous cells being responsible for the storage (and possibly production) of the toxic compounds in C. crambe. Toxicity is concentrated in the sponge periphery. Spherulous cells are also concentrated in this area and can also be observed outside the sponge exopinacoderm. These results correlate well with the assumption of a defensive role of toxicity, since encounters with potential epibionts, predators and competitive neighbours take place through this peripheral zone. However, we found two types of spherulous cells (orange and colourless, respectively) coexisting in the same sponge zones as well as in Cell Fraction 1. Thus, we cannot at present determine whether one or both types are responsible for the toxicity encountered, although it is likely that the two correspond to different states of the same cell type.     

Large-scale spatial variation in epilithic algal matrix cryptofaunal assemblages on the Great Barrier Reef

Spatial variation in the epilithic algal matrix (EAM) cryptofauna was investigated at three locations on the Great Barrier Reef: two inner shelf—Orpheus Island and the Turtle Island group—and a mid-shelf location, Lizard Island. Although the EAM appears to be a relatively simple and consistent habitat, significant differences in cryptofaunal assemblages were found between locations. EAM assemblages from Orpheus Island were markedly different. This appears to be a function of the sediment profile characteristics (grain size >60 µm) at Orpheus Island, as many cryptofaunal taxa displayed positive relationships with sediment volume. However, sediment volumes did not differ significantly between the three locations, highlighting the possibility of cyclonic activity affecting the sediment profile at Orpheus Island in the months preceding the study, in addition to the nutrient input from major terrigenous sources. The results of this study show that EAM cryptofaunal assemblages are not uniform across the Great Barrier Reef and suggest that dissolved nutrients, sediment loads and distance from river systems may be significant drivers of cryptobenthic faunal compositions.     

Localization and biochemical characterization of pharyngeal protease in the polychaetous annelid Glycera convoluta

In Glycera convoluta Keferstein, pharyngeal protease is secreted by the glandular epithelial cells, as clearly demonstrated by microscopic observation of the digestion of a prestained gelatin film by fresh tissue sections of the organ. The enzyme, extracted by affinity chromatography on Sepharose-?-aminocaproïc-D-tryptophan, acts on substrates hydrolyzable by α-chymotrypsin such as N-benzoyl-L-tyrosine ethyl ester and carboxyl-propionyl-phenylalanine-p-nitroanilide, and can be considered as a chymotrypsin-like enzyme.     

Detrital pathways in a coral reef lagoon

Coral reef lagoons are generally regarded as zones of net heterotrophy reliant on organic detritus generated in more productive parts of the reef system, such as the seaward reef flat. The abundance and biomass of sediment infauna were measured seasonally for one year (1986) within the lagoon of Davies Reef, central Great Barrier Reef, to test the hypothesis that macrofaunal biomass and production of coral reef lagoons would decrease with distance from the reef flat and would change seasonally. In general, there were no simple relationships between infaunal standing stock or production and distance from the reef flat or season. Bioturbation by callianassid shrimps negatively affected the abundance of smaller infauna, suggesting a community limited by biogenic disturbance rather than by supply of organic material. Polychaetes and crustaceans were dominant amongst the smaller infauna (0.5 to 2mm) while larger animals (> 2 mm) were mostly polychaetes and molluscs. Mean biomass of infauna at both sites and all seasons was 3 181 mg C m^?2. The smaller animals (0.5 to 2 mm) contributed about 40% of total macrofaunal respiration and production although they represented only 15% of the total macrofaunal biomass. The biomass of macrofauna was about equal to that of the bacteria and meiofauna, while respiration represented 10 to 20% of total community respiration. Consumption by macrofauna accounts for only 3 to 11% of total organic inputs to sediment, with a further 14 to 17% being lost by macrofaunal respiration.     

Response of Asterias vulgaris to chemical stimuli

Groups of the sea star Asterias vulgaris approached a variety of chemical stimuli in a flow tank. Urea, lactic acid, succinic acid, and handsweat were attractive to some animals; some simple acids and amino-acid mixtures were weakly attractive; pH changes and sea-water salts were not attractive. Although the groups were similarly maintained and responded with high internal consistency, they differed in responsiveness to different substances. These variations are not easily accounted for as contamination or effects of prior animal experience. A. vulgaris detects many simple organic substances, but the behavioral response is not constant and species-wide; it depends on nonchemical factors. This sensory/behavioral mode presumably suits a nonspecialist predator, and may be widespread among similar asteroids. Individuals attracted to lactic acid could be induced to cling to and evert their stomachs over a sponge soaked in lactic-acid solutions. The chemicals found atrractive in this study do not account for most of the attractiveness of shellfish tissue extracts studied previously.Contribution No. 2854 of the Woods Hole Oceanographic Institution.     

Investigations of carotenoids in some fauna of the Adriatic Sea. II. Anemonia sulcata and Actinia equina (Coelenterata: Anthozoa)

Investigations have been carried out on the carotenoids in Anemonia sulcata (Pennant) and Actinia equina (L.) (Coelenterata: Anthozoa) from the Adriatic Sea. The presence of the carotenoids was determined by means of columnar and thin-layer chromatography. The following carotenoids were found: Anemonia sulcata: β-carotene, lutein-like (epoxy and free) and astaxanthin; Actinia equina: α-carotene, β-carotene, actinioerythrin, lutein-like (?) and astaxanthin (ester and free).     

Hierarchical modeling of abundance in closed population capture–recapture models under heterogeneity

Hierarchical modeling of abundance in space or time using closed-population mark-recapture under heterogeneity (model \(\hbox {M}_{\text {h}}\) ) presents two challenges: (i) finding a flexible likelihood in which abundance appears as an explicit parameter and (ii) fitting the hierarchical model for abundance. The first challenge arises because abundance not only indexes the population size, it also determines the dimension of the capture probabilities in heterogeneity models. A common approach is to use data augmentation to include these capture probabilities directly into the likelihood and fit the model using Bayesian inference via Markov chain Monte Carlo (MCMC). Two such examples of this approach are (i) explicit trans-dimensional MCMC, and (ii) superpopulation data augmentation. The superpopulation approach has the advantage of simple specification that is easily implemented in BUGS and related software. However, it reparameterizes the model so that abundance is no longer included, except as a derived quantity. This is a drawback when hierarchical models for abundance, or related parameters, are desired. Here, we analytically compare the two approaches and show that they are more closely related than might appear superficially. We exploit this relationship to specify the model in a way that allows us to include abundance as a parameter and that facilitates hierarchical modeling using readily available software such as BUGS. We use this approach to model trends in grizzly bear abundance in Yellowstone National Park from 1986 to 1998.     

Lactate and succinate oxidoreductases in marine invertebrates

Nineteen species of littoral marine invertebrates, representing Porifera, Cnidaria, Ctenophora, Brachiopoda, Mollusca, and Arthropoda, were studied with respect to the ability of tissue extracts to catalyze the lactate and succinate dehydrogenase reactions in both directions. Pyruvate reductase (PR) activity varied tremendously with species, from 0.014 mole/min/g of tissue in the etenophore Mnemiopsis leidyi to 145 -moles/min in leg muscle of the horseshoe crab Limulus polyphemus, a 10,000-fold range. Lactate dehydrogenase (LD) activity varied from 0.010 in the ctenophore to 2.91 in the squid Loligo pealei, a 300-fold range. The ratio PR/LD, indicating the probability of lactic acid production, was 1,968 in muscle of the flounder, the only vertebrate studied. It was very much lower in all invertebrates; in a brachiopod, Terebratulina septentrionalis, the ratio was only 0.68. Fumarate reductase (FR) and succinate dehydrogenase (SD) activities varied less widely. The extremes of the ratio FR/SD, indicating the probability of succinic acid production, were 0.24 in the clam Mercenaria mercenaria, and 7.6 in the oyster Crassostrea virginica. PR/LD appears related to the capacity for vigorous muscular activity, sustaining rapid movement of larger animals, and FR/SD appears related to tolerance of temporary anaerobiosis, such as found in sessile animals that close their valves tightly on exposure to air during low tide.