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.     

Morphological correlates of intraspecific grafting reactions in the marine demosponge Callyspongia diffusa

There are profound differences in the ways that the sponge Callyspongia diffusa reacts to self versus non-self tissue contact. Syngeneic or isogeneic contacts result in rapid tissue fusion and persistent maintenance of normal sponge structure. However, allogeneic contacts result in immune-type rejection reactions leading to tissue death at the interface. Using grafted sponge tissues, both types of response were subject to fine-structural analysis by scanning electron microscopy. Isografts showed no overt cellular reactions other than compatible fusion, whereas sponge tissues at allograft interfaces showed incompatibility reactions. The major steps in the histopathologic sequence of events in allograft reactions may be summarized as follows: (1) immediate allorecognition occurs accompanied by microscopic cellular rearrangements; (2) macroscopic tissue bridges form across the graft interface; (3) massive cellular infiltration towards graft sites, with cells often passing into a graft partner through the tissue bridges; (4) cellular hyperplasia and then cell death occurs at the interface; and (5) sloughing of dead tissue leaves areas of vacant skeleton between the two grafted individuals. Allograft rejection reactions in sponges have many of the hallmarks of histoincompatibility reactions in higher animals. Although there could be different alloimmune mechanisms operating in different animals, the salient events of allorecognition and antagonistic rejection appear strikingly similar among diverse multicellular animals.     

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).     

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.     

Reproductive success of parasitized males in a marine reef fish

Parasitism is hypothesized to reduce reproductive success in heavily parasitized males because females may preferentially mate with less parasitized males (parasite-mediated sexual selection) or parasites may compromise male competitiveness. In marine systems, this hypothesis is largely unexplored. This paper provides the first confirmed record of a copepod ectoparasite (Caligus buechlerae Hewitt 1964) on the common triplefin (Forsterygion lapillum) and evaluates the hypothesis that males parasitized with C. buechlerae experience lower reproductive success than unparasitized males (as determined by the presence and area of eggs within male nests). We found that 38 % of males we surveyed were infected with at least one C. buechlerae, with a median of two individuals per infected male. About 32 % of males were defending eggs, with 62.5 % of those males infected with at least one parasite. Males of greater total length (TL) were both more likely to be infected and more likely to be defending eggs. However, when statistically accounting for the effects of TL, parasite infection had no effect on the probability of defending eggs, or the average surface area of eggs when present. Positive covariation in fish length, the presence of eggs and parasite infection observed here potentially suggest that the importance of parasitic infection on reproductive success may depend upon the strength of selection for larger male body size. Our study is one of the few studies to investigate the effects of ectoparasites on reproductive success in reef fish and also provides a quantitative measure of infection for a widespread species within New Zealand.     

Assimilation,inter-organ transfer and excretion of americium in two teleost fish

Radiotracer experiments were performed (February–April, 1982) to study the assimilation and metabolism of the transuranium nuclide americium-241 in the marine teleosts Serranus scriba (Linnaeus, 1758) and Scorpaena notata Rafinesque, 1810, caught off the Monaco coast. Fish fed with ²⁴¹Am-labelled food showed that assimilation of this radionuclide takes place through the gastrointestinal walls and that the small fraction accumulated is incorporated mainly in the skin, muscle and skeleton. Gut-transfer coefficients were similar in both species and averaged 0.7% (range 0.1 to 1.7%) of the ingested activity. The calculated biological half-lives for loss of the absorbed fraction ranged between 49 and 61 d for Serranus scriba and 12 and 117 d for Scorpaena notata. Results from an intramuscular injection experiment indicated that ²⁴¹Am was retained mainly in the liver, skin and skeleton; the fraction accumulated by muscle was very low. Liver displayed a relatively short biological half-time for ²⁴¹Am loss of roughly 24 d. Routes of ²⁴¹Am excretion from the teleosts appear to be through the kidneys, gills and feces with bile serving as a possible excretion route from the liver. From the limited amount of published information available for comparison, experimental evidence is presented which suggests that ²⁴¹Am taken up via the food chain is more biologically available to marine fish than is plutonium.     

Effects of gamma-aminobutyric acid on the settlement of larvae of the black chiton Katharina tunicata

Laboratory-cultured larvae of the black chiton Katharina tunicata (Wood), collected from central California in May and June of 1979 and 1980, settled preferentially on the encrusting coralline alga Lithothamnium sp. Metamorphosis, which involves the loss of the prototrochal ciliary band, occurred within a period of 2.5 h after larvae began crawling upon the alga. In response to gamma-aminobutyric acid (GABA) at a concentration of 10^-6 M, the lecithotrophic trochophore larvae ceased swimming and settled rapidly. Developmental metamorphosis did not follow settlement in the absence of encrusting coralline alga. However, when both GABA and Lithothamnium sp. were present, larval metamorphosis occurred within 2 h of settlement. Significantly different rates of settlement exist for sibling larvae of different ages; 12 d-old larvae responded more rapily and in greater numbers to treatment with GABA than 10 d-old larvae. Differences in settling rates are attributed to the onset of metamorphic competence.     

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.     

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.     

Molecular characterization of symbiotic algae (Symbiodinium spp.) in soritid foraminifera (Sorites orbiculus) and a scleractinian coral (Orbicella annularis) from St John,US Virgin Islands

The exchange of Symbiodinium symbionts among scleractinian and soritid hosts could facilitate acclimatization to changing conditions by establishing novel symbiotic unions better tuned to prevailing conditions. In this study, we compare the communities of Symbiodinium spp. in neighboring populations of Orbicella annularis and Sorites orbiculus from St. John, US Virgin Islands, using operational taxonomic unit (OTU) clustering of cloned internal transcribed spacer 2 (ITS-2) rDNA sequences. We tested for partitioning of Symbiodinium OTUs by host and depth within and between two sites to explore the potential for symbiont exchange between hosts and light-dependent microhabitat specialization. An apparent lack of overlap in Symbiodinium communities (13 OTUs representing 7 clades) hosted by O. annularis and S. orbiculus suggests that exchange among these hosts does not occur. A low number of novel clade G ITS-2 sequences were found in one O. annularis and one S. orbiculus. A phylogenetic analysis of these sequences revealed them to be sub-clade G2 Symbiodinium, which are most commonly hosted by excavating clionid sponges. A permutational MANOVA revealed within host differences in the partitioning of Symbiodinium OTUs by site but not depth. This finding highlights the potential roles of either dissimilar environmental conditions between sites, or at least partial separation between populations, in determining the types of Symbiodinium contained in different hosts on a spatial scale of a few kilometers.     

Habitat selection in the tropical polychaeteSpirobranchus giganteus

Total body weight, tube length, abdomen weight and branchial crown weight of individualSpirobranchus giganteus (Pallas) living on four different coral species on the bank reef on the west coast of Barbados were investigated in 1986. Worms onDiploria strigosa were larger in all size parameters than those onMontastrea annularis, which were larger than those onMontastrea cavernosa, which were larger than those onPorites porites. The differences between worms onM. annularis andM. cavernosa were not significant. Variation in worm size on the different corals could result from variation in mortality and/or variation in growth. Whichever the case, larger worms may have higher lifetime reproductive success. Abdomen weight is an index of gamete production inS. giganteus, and increases with increasing body weight for worms on all corals. Moreover, larger worms do not have lower abdomen weight at a given body size than smaller worms. This may imply that faster growth does not reduce gamete production at body size. The coral species on which worms are largest are those most preferred by worm larvae in the laboratory and most heavily colonised by adult worms in the field. The results suggest adaptive habitat selection by planktonic larvae ofS. giganteus.     

Exceptionally high concentrations of the insect repellent N,N-diethyl-m-toluamide (DEET) in surface waters from Jakarta,Indonesia

Jakarta is a booming coastal megacity in Indonesia with over 10 million inhabitants. The rivers flowing through the city district receive enormous amounts of untreated wastewaters from households and industries and discharge high pollutant loads into Jakarta Bay. Applying a screening approach for the identification of characteristic site-specific and harmful organic contaminants, we frequently found the insect repellent N,N-diethyl-m-toluamide (DEET) in river water and seawater samples from Jakarta. The compound was previously reported as persistent aquatic contaminant in industrial countries, and we present here the first data set from a tropical megacity. Concentrations in river water and seawater from Jakarta were exceptionally high, up to 24,000 ng L^?1, and exceeded by far all published concentrations in surface waters worldwide. We explained this with massive usage of the compound, lack of wastewater treatment and low average river flow as compared to rivers in other tropical megacities. The usage and properties of DEET indicate its suitability as molecular marker of municipal wastewaters. Such markers are useful to trace emissions from specific pollution sources in aquatic systems as a basis for the investigation of related impacts. We show here that DEET is in particular useful to trace the long-range distribution of municipal wastewaters in tropical freshwater and coastal systems. This application is of great value for tracing such inputs in tropical coastal habitats which are sensitive to changing water quality like coral reefs. This assists to uncover whether specific conditions in these systems could be related to pollutant inputs from land.     

Cadmium kinetics in oysters — a comparative study of Crassostrea gigas and Ostrea edulis

The accumulation of cadmium was investigated in two species of oysters [Crassostrea gigas (L.) and Ostrea edulis (L.)] from the same environment and in oysters of the same species (O. edulis) from two different environments (contaminated and uncontaminated), under controlled laboratory conditions (33‰ salinity, 10°C, 100 μg Cd l^-1) for up to 111 d in 1982. C. gigas accumulated cadmium twice as fast as O. edulis (1.07 vs 0.52 μg Cd g^-1 wet wt d^-1). Furthermore, O. edulis from an uncontaminated environment accumulated cadmium faster than O. edulis from a metal-contaminated environment (0.52 vs 0.34 μg Cd g^-1 wet wt d^-1). There was no effect of cadmium exposure on total soft-tissue copper and zinc concentrations. Investigation of cytosolic metal-binding using Sephadex G-75 gel-permeation chromatography indicated that binding to very low molecular weight ligands (MW<1000) accounted for>70% of the cytosolic zinc in all oysters and>40% of the cytosolic cadmium in all oysters except O. edulis from Conwy at 83 d. In copper-contaminated oysters, excess copper was also associated with very low molecular weight ligands. Intermediate molecular weight cadmium/copper-binding proteins (similar to metallothionein in molecular weight) were observed in the cytosol and were shown to differ between species in terms of their behavior on Sephadex G-75. Finally, the distribution of accumulated cytosolic cadmium in O. edulis from the contaminated environment was shown to have a unique distribution, i.e., there was no cadmium associated with high molecular weight cytosolic macromolecules. The data indicate that both genetic and environmental factors influence cadmium accumulation in oysters.     

New ecological and ultrastructural data on the dinoflagellate Dinophysis sp. from the French coast

In situ phytoplankton sampling over 24h was carried out in July 1985 during part of a monitoring program established by the Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER) to survey the blooming of toxic dinoflagellates off the French coast. Analysis of the data suggested a vertical migration of Dinophysis sp. (acuminata?) populations through the sea-water column. These diurnal displacements should be taken into account in the course of monitoring surveys of diarrhetic shellfish poisoning (DSP). Culture assays which were performed in parallel remained unsuccessful. However, Dinophysis sp. survived in an enriched sea-water medium for 4 to 5 wk under low light intensity (8 to 10 W m^-2) and constant temperature (16° to 18 °C). Cell ultrastructure, in pariticular the organization of chloroplasts, is described. All the combined results tend to confirm the photosynthetic capacity of this species.     

Differences in the species- and size-composition of fish assemblages in three distinct seagrass habitats with differing plant and meadow structure

Fish faunas were sampled seasonally using a large and a small beam trawl in three seagrass habitats comprising predominantly Amphibolis griffithii or Posidonia sinuosa or Posidonia coriacea, which differ in seagrass and meadow structure. Amphibolis griffithii and P. sinuosa both produce a relatively dense leaf canopy, but the former exhibits a distinct architecture, with the leaf canopy overlying relatively open spaces surrounding woody stems, compared to the uniformly dense blade-like leaves of P. sinuosa which emerge directly from the sediment. In comparison, P. coriacea provides a landscape of patchy seagrass amongst areas of bare sand. Since the latter seagrass habitat contains large areas of sand, fish were also sampled in adjacent unvegetated areas. The number of species and density of fish were greater (P<0.05) in P. sinuosa than in either A. griffithii or P. coriacea. The mean number of species caught using the large trawl ranged from 16 to 24 in the first of these habitats compared to 14–21 and 9–15 in the last two habitats, respectively, and the mean densities ranged between 78 and 291 fish 1000 m^?2 in P. sinuosa compared to 31–59 fish 1000 m^?2 in A. griffithii and 31–59 fish 1000 m^?2 in P. coriacea. The biomass of fish was greater (P<0.05) in both P. sinuosa and A. griffithii than in P. coriacea (4.2–5.3 kg and 3.3–6.2 kg versus 0.7–1.9 kg 1000 m^?2, respectively). Furthermore, the size-structure of fish differed among these habitats, where the median weight of fish was 72.1 g in A. griffithii, compared to 7.5 g and 19.8 g in P. sinuosa and P. coriacea, respectively. Ordination and ANOSIM demonstrated that the species-composition differed markedly among the three seagrass habitats (P<0.001), suggesting that fish species display a distinct preference for particular seagrasses characterised by different architecture. Differences in species-composition among the seagrass habitats partly reflected the size-composition of fish in each habitat. The open space below the canopy of A. griffthii is likely to allow larger fish to occupy this habitat, whereas only small fish would be able to penetrate the dense foliage of P. sinuosa. Differences in species- and size-composition of fish among these habitats may be the result of settlement-sized larvae discriminating between particular seagrass and meadow structures, or fish being subject to different levels of predation and/or accessibility to food or space. The species-composition in P. coriacea was highly dispersed and did not differ from that of unvegetated areas. While several species were associated with both P. coriacea and bare-sand habitats, some species did display a high affinity with the seagrass P. coriacea. This may reflect an association with the sparse and narrower leaves of this seagrass or with the patchy occurrence of the seagrass Heterozostera tasmanica, which commonly occurs as an understorey in this habitat.     

Growth and form in the reef-building coral Montastrea annularis

The in-situ growth rate of the reef coral Montastrea annularis on a reef at Jamaica, W. Indies was determined for a 1-year period using Alizarin Red-S staining techniques. Growth rate is correlated with water depth and growth form. The flattened growth form of M. annularis allows for continued rapid increase in colony surface area at low light intensities. The geomorphology of Jamaican reefs may in part be controlled by the population ecology of M. annularis.     

Estimation of coral growth-rates from laboratory 45Ca-incorporation rates

Laboratory ⁴⁵Ca-incorporation rates in hermatypic coral skeletons have previously been used successfully as an index of physiological function. This laboratory method would become more meanigful if it also provided an absolute measure of coral growth rates. In two coral species, Porites compressa and Pocillopora damicornis, ⁴⁵Ca incorporation rates were obtained from short (0.5 h) laboratory incubations using apical (determined as fast growing) portions of freshly collected coral branches. ⁴⁵Ca exchange across the coenosarc was not significant and not corrected for, whereas diurnal fluctuation in ⁴⁵Ca in Pocillopora damicornis was significant and a necessary correction. A calculated surface area is used to express calcification rate. Typical growth rates calculated from the ⁴⁵Ca-incorporation rates were 20 and 6 mm/year for Porites compressa and Pocillopora damicornis, respectively. These rates are considerably higher than those previously obtained in the laboratory, and compare favorably with field growth rates — 24 and 14 mm/year, respectively.     

A light and electron microscope investigation of gametogenesis in Nicolea zostericola (Polychaeta: Terebellidae)

A light and electron microscope study was conducted on Nicolea zostericola (Oersted: Grube, 1860) to describe the processes of gametogenesis. N. zostericola is a monotelic species which spawns from 2 to 5 times over a period of 2 weeks at the end of its 1-year life span. The gonads consist of plates of cells bulging from beneath the peritoneum in the thoracic region of the body. Oogenesis has been divided into 3 phases: an ovarian phase in which gametogonia and primary oocytes are retained within the ovary, a follicular phase, in which oocytes are ovulated into the coelom surrounded by several layers of follicle cells and the vitellogenic phase, where individual oocytes rupture through the follicle cells and enter the coelomic fluid where cell growth and yolk synthesis occur. The combined ovarian and follicular phases have a duration of about 3 to 5 weeks and the vitellogenic phase about 5 to 6 months. Vitellogenesis is described on the ultrastructural level. Yolk synthesis involves the participation of the Golgi apparatus and endoplasmic reticulum of the oocyte in possible combination with nutrient absorption from the coelomic fluid. Spermatogenesis involves the rupturing of masses of spermatogonia into the coelom from the testis, surrounded by peritoneal cells. Smaller clusters of spermatocytes are later released into the coelomic fluid where mitotic and meiotic divisions eventually produce flattened plates of sperm. The mature spermatozoan possesses an elongate head, atypical for most polychaetes.