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See detailImpairment of symbiont photosynthesis increases host cell proliferation in the epidermis of the sea anemone Aiptasia pallida
Fransolet, David ULg; Roberty, Stéphane ULg; Plumier, Jean-Christophe ULg

in Marine Biology (2014)

Corals exposed to environmental stresses need to engage appropriate physiological strategies to survive. Here we examined tissue modifications following algal dysfunction. Aiptasia pallida was exposed ... [more ▼]

Corals exposed to environmental stresses need to engage appropriate physiological strategies to survive. Here we examined tissue modifications following algal dysfunction. Aiptasia pallida was exposed during one week to 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), the herbicide called Diuron. DCMU treatment produced a drastic loss in photosynthetic efficiency and a subsequent diminution of algae density over the following days. Cell proliferation evaluated by measuring the number of cells labeled with a thymidine analogue (EdU) revealed a significant increase in EdU+ cells in the epidermis after one week of DCMU incubation and in the gastrodermis at four weeks. TUNEL histology showed that the extent of cell death was however similar in the epidermis of control and treated specimens. In addition we noticed a significant effect of DCMU treatment on the density of epidermal mucocytes after one, two and four weeks. These results show that inhibition of Symbiodinium photosynthesis in the absence of any known direct effect of DCMU on host cells can induce an increase of epidermal host cell proliferation in both the epidermis and the gastrodermis. While new host gastrodermal cells are likely to promote tissue regeneration in order to recruit new algae, the new host epidermal cells may contribute to tissue adaptation following a decrease in energy income. Some of these new epidermal cells, such as mucocytes, may contribute to an eventual increase of the host heterotrophic ability until restoration of algal autotrophic contribution. [less ▲]

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See detailTrophic diversity of idoteids (Crustacea, Isopoda) inhabiting the Posidonia oceanica litter
Sturaro, Nicolas ULg; Caut, Stéphane; Gobert, Sylvie ULg et al

in Marine Biology (2010), 157(2), 237-247

The coexistence of three idoteid species in Posidonia oceanica litter raises the question of trophic diversity and their role in the litter degradation process. Hence, diet composition of Idotea balthica ... [more ▼]

The coexistence of three idoteid species in Posidonia oceanica litter raises the question of trophic diversity and their role in the litter degradation process. Hence, diet composition of Idotea balthica, Idotea hectica and Cleantis prismatica was studied using a combination of gut contents and stable isotopes analysis. Gut content observations indicate that P. oceanica dead leaves are an important part of the ingested food for the three species, although their tissues are constituted of only a small to medium fraction of P. oceanica carbon. Our results also underlined the potential role of these species in the degradation of P. oceanica litter by mechanically fragmenting the litter and by assimilating a small to medium fraction of carbon. Moreover, we showed that there were considerable inter- and intra-specific differences in diet composition. Diet differed between juveniles and adults for I. balthica. Crustaceans are an important food source for adults of I. balthica, while I. hectica indicated a major contribution of algal material. C. prismatica showed an intermediate diet. This trophic diversity is probably one of the factors allowing these species to coexist in the same biotope. [less ▲]

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See detailDiversity and complexity in the acoustic behaviour of Dacyllus flavicaudus (Pomacentridae)
Parmentier, Eric ULg; Kever, Loïc ULg; Casadevall, Margardia et al

in Marine Biology (2010), 157(10), 2317-2327

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See detailWood-based diet and gut microflora of a galatheid crab associated with Pacific deep-sea wood falls
Hoyoux, Caroline ULg; Zbinden, Magali; Samadi, Sarah et al

in Marine Biology (2009)

Wood falls in the deep sea have recently become the focus of studies showing their importance as nutrients on the deep-sea Xoor. In such environments, Crustaceans constitute numerically the second-largest ... [more ▼]

Wood falls in the deep sea have recently become the focus of studies showing their importance as nutrients on the deep-sea Xoor. In such environments, Crustaceans constitute numerically the second-largest group after Mollusks. Many questions have arisen regarding their trophic role therein. A careful examination of the feeding appendages, gut contents, and gut lining of Munidopsis andamanica caught with wood falls revealed this species as a truly original detritivorous species using wood and the biofilm covering it as two main food sources. Comparing individuals from other geographic areas from substrates not reported highlights the galatheid crab as specialist of refractory substrates, especially vegetal remains. M. andamanica also exhibits a resident gut microXora consisting of bacteria and fungi possibly involved in the digestion of wood fragments. The results suggest that Crustaceans could be full-fledged actors in the food chains of sunken-wood ecosystems and that feeding habits of some squat lobsters could be different than scavenging. [less ▲]

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See detailFurther insight on carapid - holothuroid relationships
Parmentier, Eric ULg; Vandewalle, Pierre ULg

in Marine Biology (2005), 146(3), 455-465

Carapidae (or pearlfish) are eel-like fishes that live inside different invertebrates, such as holothurians, sea stars, or bivalves. Those of the genus Carapus are commensal and use their host as a ... [more ▼]

Carapidae (or pearlfish) are eel-like fishes that live inside different invertebrates, such as holothurians, sea stars, or bivalves. Those of the genus Carapus are commensal and use their host as a shelter, while Encheliophis species are parasitic and eat the host's gonads. In areas where they live in sympatry, C. boraborensis, C. homei, C. mourlani and E. gracilis are able to inhabit the same host species. Infestation is considered as monospecific when several conspecifics are observed in the same host. However, many aspects of this particular relation remain obscure, e.g. communication between carapids and the defence systems of the different protagonists (carapids and hosts). Experiments have been conducted in the field and laboratory to investigate several aspects of the carapids' relationships with their hosts. Sampling carried out in the Bay of Opunohu (Moorea, French Polynesia) determined the sex ratio of C. boraborensis (3:1) and C. homei (1:1) and their distribution rate within different Echinodermata. Our study showed that neither species was capable of determining whether a heterospecific already occupied a sea cucumber or not. They were, however, able to locate the sea cucumber's cloaca, due to the excurrent resulting from respiration. The sea cucumber's defence system (Cuverian tubules) minimises predator attacks, but is not effective against carapid intrusion. The Carapidae defence system is twofold. Due to a passive system related to the sea cucumber's low cloacal position, the Cuverian tubules are not expelled when fish enter the cloaca. Moreover, carapids resist sea cucumber toxins better than other reef fish. Their increased resistance might be related to their gills rather than to their mucus coating; however, the latter may assist the fish in resisting the sticky substances emitted by the Cuverian tubules. [less ▲]

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See detailComparative degradation rates of chitinous exoskeletons from deep-sea environments
Ravaux, J.; Zbinden, M.; Voss-Foucart, M. F. et al

in Marine Biology (2003), 143(2), 405-412

Hydrothermal vent environments, particularly those associated with the vestimentiferan Riftia pachyptila, are believed to be among the highest chitin-producing systems. In order to elucidate the chitin ... [more ▼]

Hydrothermal vent environments, particularly those associated with the vestimentiferan Riftia pachyptila, are believed to be among the highest chitin-producing systems. In order to elucidate the chitin cycle in these environments, we estimate the in situ chitin degradation rates of tube-worm exoskeletons. Our in situ experiments show that the tubes of Riftia are highly stable structures. Comparative measurements of the degradation rates of Riftia tubes and crab shells immersed at deep-sea vents show that the tubes would be degraded within 2.5 years, whereas the time for the total degradation of the vent crab (Bythograea thermydron) carapaces would not exceed 36 days. The importance of the microbial participation in this degradation was estimated for Riftia tubes. Based on previous work, we calculated chitin production by a population of Riftia tubes of about 750 g m(-2) year(-1) (763). From our in situ experiments, we estimated a microbial chitinolysis rate of about 500 g m(-2) year(-1) (496) (65% of the chitin produced). Exoskeletons containing beta-chitin appear more stable in natural environments than those containing alpha-chitin and would thus be less available as carbon and nitrogen sources. In contrast, isolated beta-chitin was hydrolysed faster than alpha-chitin during in vitro degradation experiments; for instance, Riftia beta-chitin was degraded about 3- to 4-fold faster than Bythograea alpha-chitin. A stabilization process by disulfide bonds of the proteins-chitin link, rather than the crystalline form of the chitin (alpha/beta), accounts for the resistance of Riftia tubes to enzymatic attacks. [less ▲]

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See detailRelationships between inner ear and sagitta growth during ontogenesis of three Carapini species, and consequences of life-history events on the otolith microstructure
Parmentier, Eric ULg; Lagardère, Françoise; Vandewalle, Pierre ULg

in Marine Biology (2002), 141(3), 491-501

Three species of Carapidae have in common a tenuis larval stage, during which they settle in the lagoon and take refuge in the same species of holothurold. From the juvenile stage, Carapus homei and C ... [more ▼]

Three species of Carapidae have in common a tenuis larval stage, during which they settle in the lagoon and take refuge in the same species of holothurold. From the juvenile stage, Carapus homei and C. boraborensis are commensal, whereas Encheliophis gracilis is parasitic. The aims of this study were to analyse to what extent the ontogenctic changes of the otic capsule affected the shape of the inner ear and how environmental cues, due to the above-mentioned life history and the style, could influence the structure of the sagitta. Sagittal sections revealed a three-dimensional asymmetry with a nucleus close to the proximal surface. Observations of the growth axis of the sagitta suggest it has a morphogenetic impact on the otic cavity. Each sagitta contains three main zones related to the life stages of the fish. Bands and checks were observed in the third zone in C. homei and C. boraborensis, but this pattern was less discernible in E. gracilis. These structural differences in zone 3 could be related to the commensal and parasitic life styles of these fishes. Further studies dealing with otosac features and otolith functions are suggested. [less ▲]

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See detailIdentification of tenuis of four French Polynesian Carapini (Carapidae : Teleostei)
Parmentier, Eric ULg; Lo-Yat, A.; Vandewalle, Pierre ULg

in Marine Biology (2002), 140(3), 633-638

Four species of adult Carapini (Carapidae) occur on Polynesian coral reefs: Encheliophis gracilis, Carapus boraborensis, C. homei and C. mourlani. Samples collected in Rangiroa and Moorea allowed us to ... [more ▼]

Four species of adult Carapini (Carapidae) occur on Polynesian coral reefs: Encheliophis gracilis, Carapus boraborensis, C. homei and C. mourlani. Samples collected in Rangiroa and Moorea allowed us to obtain different tenuis (larvae) during their settlement phases or directly inside their hosts. These were separated into four lots on the basis of a combination of pigmentation, meristic, morphological, dental and otolith (sagittae) features. Comparison of these characters with those of the adults allows, for the first time, taxonomic identification of these tenuis-stage larvae. [less ▲]

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See detailRelative impact of a seagrass bed and its adjacent epilithic algal community in consumer diets
Lepoint, Gilles ULg; Nyssen, Fabienne ULg; Gobert, Sylvie ULg et al

in Marine Biology (2000), 136

The aim of this work was to identify and compare, using nitrogen and carbon stable isotope data, the food sources supporting consumer communities in a Mediterranean seagrass bed (Gulf of Calvi, Corsica ... [more ▼]

The aim of this work was to identify and compare, using nitrogen and carbon stable isotope data, the food sources supporting consumer communities in a Mediterranean seagrass bed (Gulf of Calvi, Corsica) with those in an adjacent epilithic algal dominated community. Isotopic data for consumers are not significantly different in the two communities. Particulate matter and algal material (seagrass epiflora and dominant epilithic macroalgae) appear to be the main food sources in both communities. Generally, the 13C of animals suggests that the seagrass Posidonia oceanica (L.) Delile represents only a minor component of their diet or of the diet of their prey, but the occurrence of a mixed diet is not excluded. P.oceanica dominates the diet of only of few species, among which holothurians appear as key components in the cycling of seagrass material. [less ▲]

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See detailOn endostyle ultrastructure in two new species of doliolid-like tunicates
Compère, Philippe ULg; Godeaux, Jean

in Marine Biology (1997), 128

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