Chthamalus stellatus (Poli) und C. depressus (Poli) in der adria

A study has been made of the ecology of Chthamalus stellatus (Poli) and C. depressus (Poli) in the region of Rovinj (Yugoslavia). The distribution has been examined at several localities of different habitat conditions particularly with respect to wave action.     

A histological and scanning electron microscope study of the formation of the wall plates in Chthamalus depressus (Poli)

Because of the small amount of pigmentation the difficulties associated with earlier histological work on Chthamalus stellatus (Poli) are absent in extreme hypobiotic C. depressus (Poli). The formation of the wall plates has been investigated by normal histological techniques and supported by scanning electron microscopy. The wall plates are covered by epicuticle which in its continuity resembles that of Acasta spongites; the epicuticle is strongly ribbed and the plate has more or less regularly spaced, volcano-like outgrowths. The various cell-types and the part they play in the expansion of the basis and growth of the wall plate are described. A series of ‘bridging’ cells are present and lie between the lower part of the last completely formed ‘scale’ and the basal cells. Growth is considered from the evolutionary point of view and in relation to the forms assumed under natural conditions, in particular to the capacity of the animal to adapt to changes in the rock surface.     

The organic and inorganic composition of some cirripede shells

The protein, chitin, calcium, and magnesium present in the shells of several species of cirripedes have been determined; the powdered shell material was also examined by differential thermal analysis (DTA). Chthamalus sp., in which lamina of epicuticular matter are present within the shell, show the greatest organic content. When the organic material is separated into its protein and chitin components the latter is present in similar quantities in all species; this reflects a similar quantity of the chitin-protein matrix. Reduction in the protein content of heavily eroded C. depressus seems to be due to the removal of protein by endolithic algae. The $\text{Ca}\text{Mg}$ ratio increases from extreme hypobiotic to exposed C. depressus. There is a marked correlation between the $\text{Ca}\text{Mg}$ ratio and the organic content and it is suggested that the magnesium is largely associated with protein rather than with the calcitic lattice. This receives support from the thermal analyses. Small quantities of quartz were detected by X-ray analysis.     

Studies in the biochemistry of cirripede eggs. V. Changes in the general biochemical composition during development of Chthamalus stellatus (Poli)

The biochemical composition of the eggs of Chthamulus stellatus (Poli) during their development has been investigated. The eggs are incubated within the mantle cavity of the adult but no substrates are contributed by the latter. Carbohydrates, protein, and lipid are all utilized. In contrast to two cold-water species, Balanus balanoides and B. balanus perviously investigated lipid rather than protein is consumed during the early stages. Possible explanations for this are considered.     

Distribution and abundance of co-occurring chthamalid barnacles Chthamalus montagui and Chthamalus stellatus (Crustacea,Cirripedia) on the southwest coast of Portugal

Two co-occurring chthamalid barnacle species occur on the rocky shores of continental Portugal: Chthamalus stellatus (Poli) and Chthamalus montaguiSouthward. In the present study, patterns of distribution and abundance (density and percentage cover), both vertically (tidal level) and horizontally (wave action), were studied for each species on headlands (more wave action) and not on headlands (less wave action) and at two spatial scales (shore and site) and three tidal levels (low, mid and upper). Chthamalus montagui was significantly more abundant than C. stellatus in both degrees of wave action and at all tidal levels. Despite this great difference in abundance and considering each species individually, C. montagui was more abundant at mid tide-level, while C. stellatus was more abundant at the low tide-level, and C. montagui was less abundant on headlands, while C. stellatus was more abundant on headlands. Small-scale variability (between sites, tens of meters) of abundance of each species was detected, while differences on a larger scale (between shores, tens of kilometres) were not significant.     

Effects of Endolithic Parasitism on Invasive and Indigenous Mussels in a Variable Physical Environment

Biotic stress may operate in concert with physical environmental conditions to limit or facilitate invasion processes while altering competitive interactions between invaders and native species. Here, we examine how endolithic parasitism of an invasive and an indigenous mussel species acts in synergy with abiotic conditions of the habitat. Our results show that the invasive Mytilus galloprovincialis is more infested than the native Perna perna and this difference is probably due to the greater thickness of the protective outer-layer of the shell of the indigenous species. Higher abrasion due to waves on the open coast could account for dissimilarities in degree of infestation between bays and the more wave-exposed open coast. Also micro-scale variations of light affected the level of endolithic parasitism, which was more intense at non-shaded sites. The higher levels of endolithic parasitism in Mytilus mirrored greater mortality rates attributed to parasitism in this species. Condition index, attachment strength and shell strength of both species were negatively affected by the parasites suggesting an energy trade-off between the need to repair the damaged shell and the other physiological parameters. We suggest that, because it has a lower attachment strength and a thinner shell, the invasiveness of M. galloprovincialis will be limited at sun and wave exposed locations where endolithic activity, shell scouring and risk of dislodgement are high. These results underline the crucial role of physical environment in regulating biotic stress, and how these physical-biological interactions may explain site-to-site variability of competitive balances between invasive and indigenous species.     

The vertical distribution of Chthamalus montagui and Chthamalus stellatus (Crustacea,Cirripedia) in two areas of the NW Mediterranean Sea

The Mediterranean Sea is characterised by a small tidal range (0.3–1 m). Despite this, intertidal communities are well established and their upper limits often extend above mean high water level. Organisms living in the intertidal region and in the supralittoral zone rely on both tides and wave action to perform their biological functions. Lack of food, desiccation and predation are common stresses in such a harsh environment. The present study deals with the vertical distribution of two species of intertidal barnacles, Chthamalus montagui Southward and Chthamalus stellatus (Poli), which are the main constituents of the barnacle belt along Mediterranean rocky shores. Previous work, carried out in the Atlantic, showed that where the distribution ranges of the two Chthamalus species overlap, C. montagui is more common in the upper barnacle zone while C. stellatus is dominant lower down. The main aims of our study are: (1) to establish if there is a relationship between position and extension of the barnacle belt on the shore and tidal range and/or wave exposure, (2) to test the hypothesis that in the study areas C. montagui is more abundant than C. stellatus high on the shore, and that the pattern is reversed lower down. Barnacle populations were monitored in summer 1998 in the Gulf of Genoa (Ligurian Sea) and in the Gulf of Trieste (North-Adriatic Sea). The two areas differ in tidal range and hydrodynamism, the former presenting quite strong wave action and a tidal range of 30 cm, the latter having limited wave action and 1 m tidal range. Three shores were randomly selected in each gulf and two transects on each shore. Counts of barnacles in 10 ^* 10 cm quadrats were done at different shore heights along each transect. The data was subjected to analysis of variance. Results showed that a more pronounced hydrodynamic regime corresponded to a shift of the barnacle belt towards the higher shore (Gulf of Genoa), while in more sheltered areas (Gulf of Trieste), the barnacle distribution was confined to the intertidal region. The relative spatial distribution of C. montagui and C. stellatus within the barnacle belt varied locally, even between transects on the same shore, and this obscured the distribution pattern along the vertical gradient. Nevertheless, it was still possible to conclude that at mid and high shore in Genoa, C. stellatus was more abundant than C. montagui, while in Trieste the pattern was reversed.     

The responses during development of the embryos of some common cirripedes to wide changes in salinity

The effect of hypo- and hypersaline media on the development of the embryos of the common cirripedes, Balanus balanoides, (L.), B. crenatus Brug., B. balanus (L.), B. perforatus Brug., Chthamalus stellatus (Poli), and Elminius modestus Darwin has been examined. These species represent littoral and sublittoral, boreo-arctic and warm-temperate, relatively steno- and euryhaline, and steno- and eurythermal forms. The range of salinity over which the embryos would develop to give free-swimming stage I nauplius larvae, no matter at what stage of development the cultures were started, was similar in all species, namely 15–20 to 40%. Low-salinity media cause cytolysis while high salinity media give grossly abnormal embryos which may, however, develop further. There seems little direct relation between salinity tolerance and that of the habitat in which the animals are found; a capacity for acclimation may be more important. The causes underlying the production of abnormalities are discussed.     

Endolithic chlorophyll d-containing phototrophs

Cyanobacteria in the genus Acaryochloris are the only known oxyphototrophs that have exchanged chlorophyll a (Chl a) with Chl d as their primary photopigment, facilitating oxygenic photosynthesis with near infrared (NIR) light. Yet their ecology and natural habitats are largely unknown. We used hyperspectral and variable chlorophyll fluorescence imaging, scanning electron microscopy, photopigment analysis and DNA sequencing to show that Acaryochloris-like cyanobacteria thrive underneath crustose coralline algae in a widespread endolithic habitat on coral reefs. This finding suggests an important role of Chl d-containing cyanobacteria in a range of hitherto unexplored endolithic habitats, where NIR light-driven oxygenic photosynthesis may be significant.     

Comparison of phototrophic shell-degrading endoliths in invasive and native populations of the intertidal mussel Mytilus galloprovincialis

The intertidal mussel Mytilus galloprovincialis is a successful invader worldwide. Since its accidental introduction onto the South African west coast in the late 1970s, it has become the most successful marine invasive species in South Africa. One possible explanation for this phenomenon is that M. galloprovincialis suffers less from phototrophic shell-degrading endoliths in its invasive than in its native range. We assessed photoautotrophic endolithic pressure on M. galloprovincialis in native (Portugal) and invasive (South Africa) ranges. Invasive populations were more heavily infested than native populations. In Portugal, only the biggest/oldest mussels displayed endolithic erosion of the shell and the incidence of infestation was greater at higher shore levels where more prolonged exposure to light enhances endolith photosynthesis. In South Africa, even the smallest size classes of mussels were heavily infested throughout the shore. In Portugal, endolithic-induced mortality was observed at only one location, while in South Africa it occurred at all locations and at significantly higher rates than in Portugal. Important sub-lethal effects were detected in infested native mussels, confirming previous studies of invasive populations and suggesting an energy trade-off between shell repair and other physiological constraints. We observed a positive relationship between infestation rates and barnacle colonization on mussel shells, suggesting possible facilitation of barnacle settlement/survival by shell-boring pathogens. Identification of endoliths revealed common species between regions. However, two species were unique in the invasive range while another was unique in the native region. Different levels of endolithic infestation in the invasive and the native range were not explained by the effect of major environmental determinants (Photosynthetically Available Radiation and wave height). The results reject our initial hypothesis, indicating that invasion success of M. galloprovincialis is not simply explained by escape from its natural enemies but results from complex interactions between characteristics of the invaded community and properties of the invader.     

Non-native parasite enhances susceptibility of host to native predators

Parasites often alter host physiology and behavior, which can enhance predation risk for infected hosts. Higher consumption of parasitized prey can in turn lead to a less parasitized prey population (the healthy herd hypothesis). Loxothylacus panopaei is a non-native castrating barnacle parasite on the mud crab Eurypanopeus depressus along the Atlantic coast. Through prey choice mesocosm experiments and a field tethering experiment, we investigated whether the predatory crab Callinectes sapidus and other predators preferentially feed on E. depressus infected with L. panopaei. We found that C. sapidus preferentially consumed infected E. depressus 3 to 1 over visibly uninfected E. depressus in the mesocosm experiments. Similarly, infected E. depressus were consumed 1.2 to 1 over uninfected conspecifics in field tethering trials. We evaluated a mechanism behind this skewed prey choice, specifically whether L. panopaei affects E. depressus movement, making infected prey more vulnerable to predator attack. Counter to our expectations, infected E. depressus ran faster during laboratory trials than uninfected E. depressus, suggesting that quick movement may not decrease predation risk and seems instead to make the prey more vulnerable. Ultimately, the preferential consumption of L. panopaei-infected prey by C. sapidus highlights how interactions between organisms could affect where novel parasites are able to thrive.     

Establishment of endolithic populations of extremophilic Cyanidiales (Rhodophyta)

Background  

Cyanidiales are unicellular extremophilic red algae that inhabit acidic and high temperature sites around hot springs and have also adapted to life in endolithic and interlithic habitats. Comparative genomic analysis of Cyanidioschyzon merolae and Galdieria sulphuraria predicts that the latter may be more broadly distributed in extreme environments because its genome contains membrane transporters involved in the uptake of reduced carbon compounds that are absent from C. merolae. Analysis of an endolithic site in the Phlegrean Fields near Naples, Italy is consistent with this prediction showing this population to be comprised solely of the newly described lineage Galdieria -B and C. merolae to be limited to humid habitats. Here, we conducted an environmental PCR survey of another extreme environment in Tuscany, Italy and contrasted Cyanidiales population structure at endolithic and interlithic habitats in Naples and Tuscany.     

Nd-YAG laser irradiation damages to Verrucaria nigrescens

Epilithic and endolithic microorganisms and lichens play an important role in stone biodeterioration. The structural and physiological damage caused by nanosecond pulsed laser of 1064 nm from Nd:YAG laser to Verrucaria nigrescens lichen as well as to endolithic algae and fungi were investigated in the present study. Ultrastructural laser effects on lichen and endolithic microorganisms were study without disturbing the relationship between lichen and lithic substrate by taking lichen-containing rock fragments and processing both together. SEM-BSE, LT-SEM and FM were used to determine cell integrity and ultrastructure, which reflect microorganism viability. Photobiont vitality was determined using a PAM chlorophyll fluorescence technique. The lichen thalli were completely removed by irradiation with 5 ns pulses at a fluence of 2.0 J/cm² with no stone damage as showed by micro-Raman spectroscopy. The fungal and algal endolithic cells located below were completely destroyed or presented a high plasmolysis degree resulting from heating their microenvironment. The lichen and endolithic mycobiont near the irradiated zone were also damaged. Algal photosynthetic damage prevents fungal survival and lichen viability. This is the first report of laser removal and inactivation of lichen and lithic microorganisms, and thus provide an environmentally friendly and efficient method to control stone biodeterioration.     

Functional diversity of microboring Ostreobium algae isolated from corals

The filamentous chlorophyte Ostreobium sp. dominates shallow marine carbonate microboring communities, and is one of the major agents of reef bioerosion. While its large genetic diversity has emerged, its physiology remains little known, with unexplored relationship between genotypes and phenotypes (endolithic versus free-living growth forms). Here, we isolated nine strains affiliated to two lineages of Ostreobium (>8% sequence divergence of the plastid gene rbcL), one of which was assigned to the family Odoaceae, from the fast-growing coral host Pocillopora acuta Lamarck 1816. Free-living isolates maintained their bioerosive potential, colonizing pre-bleached coral carbonate skeletons. We compared phenotypes, highlighting shifts in pigment and fatty acid compositions, carbon to nitrogen ratios and stable isotope compositions (δ¹³C and δ¹⁵N). Our data show a pattern of higher chlorophyll b and lower arachidonic acid (20:4ω6) content in endolithic versus free-living Ostreobium. Photosynthetic carbon fixation and nitrate uptake, quantified via 8 h pulse-labeling with ¹³C-bicarbonate and ¹⁵N-nitrate, showed lower isotopic enrichment in endolithic compared to free-living filaments. Our results highlight the functional plasticity of Ostreobium phenotypes. The isotope tracer approach opens the way to further study the biogeochemical cycling and trophic ecology of these cryptic algae at coral holobiont and reef scales.     

Spatial variation in the recruitment of the intertidal barnacles Chthamalus montagui Southward and Chthamalus stellatus (Poli) (Crustacea: Cirripedia) over an European scale

Spatial variation in the recruitment of the intertidal barnacles Chthamalus montagui and Chthamalus stellatus was examined over an European scale. The study was carried out using standardised protocols at a series of locations. The five locations chosen (SW Ireland, NW Spain, SW Portugal and NW and NE Italy) span a large part of the range of these species in Europe. The spatial scales were location (hundreds of kilometres) and shore (thousands of metres).Estimates of total cumulative recruitment (cyprids and metamorphs) summed over the year (April 1997 to March 1998) showed substantial variation between locations which was dependent on the species. Recruitment was highest in SW Portugal for C. montagui and in SW Ireland and NW Spain for C. stellatus. Overall recruitment of C. montagui was higher than that of C. stellatus at all locations except SW Ireland, where recruitment of the two species was not significantly different. There were significant differences among shores in each location.The recruitment period of both species varied with location, with recruitment beginning earlier further south. In general, recruitment of C. montagui and C. stellatus was recorded in 8 months in NW Spain and NE Italy, while only in 7 months in SW Ireland. Recruitment of C. montagui occurred in 10 months in SW Portugal, but no recruits of C. stellatus were found. In all locations there was at least one distinct peak of recruitment. In SW Ireland both species showed only one peak of recruitment, a month after initiation. At the more southerly Atlantic locations, as well as in the Mediterranean, two unequal peaks of recruitment were generally seen. During recruit census, the number of cyprids, in comparison to metamorphs, found at any location was very low. In SW Ireland and NW Spain cyprids of both species were found, while in SW Portugal and in the Mediterranean, only cyprids of C. montagui were found.     

Phototrophic microendoliths bloom during coral “white syndrome”

Following rapid lesion progression of white syndrome in tabular Acropora spp., the white bare skeleton gradually changes to green, a result of endolithic algae blooms (primarily Ostreobium spp.). Endolithic algal biomass and chlorophyll concentration were found to be an order of magnitude higher in the green zone compared with healthy appearing parts of each colony. Chl b to Chl a ratio increased from 1:1.6 in the healthy area to 1:2 and 1:3.5 in the white exposed skeleton and green zones, respectively. These observations together with pulse amplitude modulated (PAM) fluorometry suggest photoacclimation of the endoliths in the green zone. Histopathological microscopy revealed that the endolithic algal filaments penetrate the coral tissue. This study highlights the interaction of endolithic algae with both the skeleton and host tissue. This may have a critical role in the processes that accompany the post-disease state in reef-building corals.     

In vitro receptivity of carbonate rocks to endolithic lichen-forming aposymbionts

Sterile cultured isolates of lichen-forming aposymbionts have not yet been used to investigate lichen-rock interactions under controlled conditions. In this study mycobionts and photobiont of the endolithic lichens Bagliettoa baldensis and Bagliettoa marmorea were isolated and inoculated with coupons of one limestone and four marbles commonly employed in the Cultural Heritage framework. After one year of incubation, microscopic observations of polished cross-sections were performed to verify if the typical colonization patterns observed in the field may be reproduced in vitro and to evaluate the receptivity of the five lithotypes to endolithic lichens. The mycobionts of the two species developed both on the surface of and within all the lithotypes, showing different penetration pathways which depend on mineralogical and structural features and highlight different receptivity. By contrast, algae inoculated with the coupons did not penetrate them. Observations suggest that the hyphal penetration along intrinsic discontinuities of rocks is a relatively fast phenomenon when these organisms are generally considered as slow-growing. Samples from limestone outcrops and abandoned marble quarries, colonized by the same species or other representatives of Verrucariaceae, showed penetration pathways intriguingly similar to those reproduced in vitro and highlighted that lichen-driven erosion processes only increase the availability of hyphal passageways after a long-term colonization. These results show that in vitro incubation of sterile cultured lichen-forming ascomycetes with rock coupons is a practicable experimental system to investigate the lichen-rock interactions under controlled conditions and, together with analysis in situ, may support decisions on conservative treatments of historical and cultural significant stone substrata.     

Impact assessment of an invasive flatworm, Convoluta convoluta, in the Southern Gulf of Maine

Convoluta convoluta (Abildgaard 1806) is a small (2-3 mm long) acoellous turbellarian flatworm from Europe that has invaded the Gulf of Maine within the last 5 years. Although it has been reported in densities of up to 19 individuals/cm², its ecological impact remains unknown. In its native habitat, it consumes harpacticoid copepods and primary settling mussels <0.5-mm shell length. This study estimated the impact of C. convoluta on juvenile blue mussel populations (Mytilus edulis Linnaeus 1758) around the Isles of Shoals in the southern Gulf of Maine, USA as well as looking at their distribution in their new habitat. We surveyed worm densities at sites of differing wave exposure over three substrates (hard substrates, bladed algae, filamentous algae) to quantify patterns of worm abundance. We found worms on all substrate types with their highest abundances occurring in areas of maximal sunlight exposure and minimal physical disturbance. We showed a definite pattern of consumption of mussels in the lab and found C. convoluta to consume up to 35% of primary settling mussels in the field, but only under certain conditions. Per capita impact on juvenile mussels was found to vary greatly in correlation with mussel recruitment rate and water temperature, but not with the consumption of harpacticoids. Our results also suggested that per capita interaction strength was reduced by intraspecific density-dependent competition and water temperature. The overall impact of C. convoluta on mussel populations in the southern Gulf of Maine is therefore estimated to be minimal.     

Stable isotopic records of bleaching and endolithic algae blooms in the skeleton of the boulder forming coral Montastraea faveolata

Within boulder forming corals, fixation of dissolved inorganic carbon is performed by symbiotic dinoflagellates within the coral tissue and, to a lesser extent, endolithic algae within the coral skeleton. Endolithic algae produce distinctive green bands in the coral skeleton, and their origin may be related to periods of coral bleaching due to complete loss of dinoflagellate symbionts or “paling” in which symbiont populations are patchily reduced in coral tissue. Stable carbon isotopes were analyzed in coral skeletons across a known bleaching event and 12 blooms of endolithic algae to determine whether either of these types of changes in photosynthesis had a clear isotopic signature. Stable carbon isotopes tended to be enriched in the coral skeleton during the initiation of endolith blooms, consistent with enhanced photosynthesis by endoliths. In contrast, there were no consistent δ¹³C patterns directly associated with bleaching, suggesting that there is no unique isotopic signature of bleaching. On the other hand, isotopic values after bleaching were lighter 92% of the time when compared to the bleaching interval. This marked drop in skeletal δ¹³C may reflect increased kinetic fractionation and slow symbiont recolonization for several years after bleaching.