References of "Eeckhaut, Igor"
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See detailIsotopic tracing of sediment components that are assimilated by epibiontic juveniles of Holothuria scabra (Holothuroidea)
Plotieau, Thomas; Lepoint, Gilles ULg; Lavitra, Thiery et al

in Journal of the Marine Biological Association of the United Kingdom (in press)

Despite H. scabra’s wide distribution and status as one of the best candidates for sustaining the development of tropical sea cucumber aquaculture, very few data are available regarding the organic ... [more ▼]

Despite H. scabra’s wide distribution and status as one of the best candidates for sustaining the development of tropical sea cucumber aquaculture, very few data are available regarding the organic fraction it assimilates in practice. In this study we report experimental results where H. scabra’s diet was supplemented with various 15N-labelled organic fractions of sediment. We used juveniles weighing between 38- 88 mg at the beginning of the experiment (ca. 2 cm long and 30 days old). Their growth was measured over a four week period and their 15N composition recorded. The results showed that H. scabra juveniles assimilated all added organic components from both dissolved and particulate fractions of the sediment. Bacteria seem to be an important food source for juveniles, even more so than microphytobenthos (diatoms). [less ▲]

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See detailThe diet of the Harlequin crab Lissocarcinus orbicularis, an obligate symbiont of sea cucumbers (holothuroids) belonging to the genera Thelenota, Bohadschia and Holothuria
Caulier, Guillaume; Lepoint, Gilles ULg; Van Nedervelde, Fleur et al

in Symbiosis (2014)

The present paper characterizes, for the first time, the diet of the Harlequin crab, Lissocarcinus orbicularis an obligate symbiotic crab that associates with sea cucumbers (holothuroids) belonging to the ... [more ▼]

The present paper characterizes, for the first time, the diet of the Harlequin crab, Lissocarcinus orbicularis an obligate symbiotic crab that associates with sea cucumbers (holothuroids) belonging to the genera Thelenota, Bohadschia and Holothuria. These tropical holothuroids host a rich symbiotic community in the Indo-West Pacific Ocean of which the Harlequin crab is the best known. The diet of L. orbicularis was characterized by analyzing the microscopic, molecular and isotopic signatures obtained from its gastric content. The presence of sea cucumber ossicles in the gastric mills of the crabs suggests that symbionts eat the superficial integument of their host and this was suppoarted by the fact that Holothuroid DNA was detected in the stomach of L.orbicularis after DGGE and sequencing of the 18S rDNA gene. The stable isotopic δ13C and δ15N values of crab tissues were compared with diverse potential food sources including the three holothuroids, three algae, one sea grass as well as the organic matter contained in the water column, in the sediment, and the second most abundant symbiont, the polychaete Gastrolepidia clavigera. The low δ15N values of crabs suggest that the crabs do not exclusively feed on sea cucumber tissue but assimilate diverse food sources such as sea grasses and organic matter contained in sediment that have similar δ13C values. There were no difference between the feeding of males and females but there was a positive correlation between the carapace length and the stable isotopic values indicating a shift of the food source as crabs grow larger. [less ▲]

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See detailCharacterization of a population of the Harlequin crab, Lissocarcinus orbicularis Dana, 1852, an obligate symbiont of holothuroids, in Toliara bay (Madagascar)
Caulier, Guillaume; Parmentier, Eric ULg; Lepoint, Gilles ULg et al

in Zoosymposia (2012), 7

Harlequin crabs, Lissocarcinus orbicularis, are commensals found on the integument and in the buccal/cloacal cavity of several species of holothuroids. The population of these crabs was investigated on ... [more ▼]

Harlequin crabs, Lissocarcinus orbicularis, are commensals found on the integument and in the buccal/cloacal cavity of several species of holothuroids. The population of these crabs was investigated on holothuroids of the barrier reef of Toliara (South-West of Madagascar) from 2002 to 2008. Seventeen holothuroid species were observed and eight were crab hosts. There is generally one adult crab or a heterosexual pair per infested holothuroid but up to ten juveniles were recorded on a Thelenota ananas. Carapace length of the observed L. orbicularis was from 0.3 to 1.4 cm from the tip of the rostrum to the end of the cephalothorax, with a mean length of 0.85 cm. L. orbicularis is characterized by a weak sexual dimorphism (females are bigger than males) and the presence of pereiopods morphologically adapted to fixation on the host integument. Gravid females were observed at each month of the survey indicating that the crab reproduces all the year. Considering our results and personal observations, we also discuss the monogamy mating system of the Harlequin crab. [less ▲]

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See detailUnique morphologies of Encheliophis vermiops (Carapidae) with revised diagnosis of the genus
Parmentier, Eric ULg; Lanterbecq, Déborah; Todesco, Maité ULg et al

in Ichthyological Research (2010), 57(1), 85-90

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See detailResistance of pearlfishes to saponins
Maïté, Todesco; Parmentier, Eric ULg; Eeckhaut, Igor

Poster (2009)

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See detailVariations in the sound producing mechanism in the pearlfish Carapini (Carapidae)
Parmentier, Eric ULg; Lagardère, Jean-Paul; Chancerelle, Yannick et al

in Journal of Zoology (2008), 276

Sound production in Carapus boraborensis results from the action of different sonic muscles terminating in complex tendons, which have hooks that fit over a tubercle on the swimbladder wall. The primary ... [more ▼]

Sound production in Carapus boraborensis results from the action of different sonic muscles terminating in complex tendons, which have hooks that fit over a tubercle on the swimbladder wall. The primary sonic muscles (PSM) draw progressively the forepart of the swimbladder until the hook releases the tubercle. This allows the swimbladder to snap back to its resting position, which initiates the onset of the sound. In the present study, the morphology of the C. boraborensis sound-producing apparatus and the resulting sounds were compared with Encheliophis gracilis and Carapus homei. The main difference concerns the direct insertion of the PSM on the swimbladder in C. homei and E. gracilis and, concurrent sonic characteristics. These morphological features also allow both fish to produce an additional kind of sound with more compact pulses, each being clearly composed of two parts and each having a different frequency. The sound producing system could be compared with a guitarist who makes a sound in releasing a guitar string and modulates it by moving his/her finger along the string. However, E. gracilis possess more filtered sounds than C. boraborensis and C. homei, probably because of the unusual shape of its swimbladder. This study highlights the diversity and plasticity of sonic mechanisms and their implication in the development of sonic repertoire in evolving species. [less ▲]

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See detailAssessment of trophic relationships between symbiotic tropical ophiuroids using C and N stable isotope analysis
Fourgon, Didier; Lepoint, Gilles ULg; Eeckhaut, Igor

in Journal of the Marine Biological Association of the United Kingdom (2006), 86(6), 1443-1447

Analyses of the natural abundance of carbon and nitrogen stable isotopes were performed to investigate the feeding habits of two ophiurolds, Ophiomastix venosa and Ophiocoma scolopendrina, and to assess ... [more ▼]

Analyses of the natural abundance of carbon and nitrogen stable isotopes were performed to investigate the feeding habits of two ophiurolds, Ophiomastix venosa and Ophiocoma scolopendrina, and to assess the potential benefit obtained by the symbiotic Ophiomastix venosa juveniles. A tracer experiment was also carried Out to clarify the contribution of algae to the nitrogen uptake amongst the tested ophiurolds. Our results suggest that Ophiocoma scolopendrina adults occupy a higher position in the food web than Ophiomastix venosa and mainly feed on neuston. In contrast, O. venosa adults feed on the alga Sargassum densifolium, and on organic matter associated with sediment. Free juveniles and symbiotic juveniles of O. venosa have intermediate PC values between both adult species. The high proportion of C-13 in the symbiotic juveniles compared to the one in their conspecific adults indicates that their diet slightly differs from the latter and is closer to that of Ophiocoma scolopendrina. This raises the hypothesis that symbiotic juveniles steal neuston front their associated host, O. scolopendrina. [less ▲]

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See detailParasites and biotic diseases in field and cultivated sea cucumbers
Eeckhaut, Igor; Parmentier, Eric ULg; Becker, P. et al

in Lovatelli, A.; Conand, C.; Purcell, S. (Eds.) et al Advances in sea cucumber aquaculture and management (2004)

Amongst echinoderms, the Holothuroidea represents the class that is the most infested by parasites. Parasites of holothuroids are Bacteria, Protozoa and Metazoa. There are about 150 species of metazoans ... [more ▼]

Amongst echinoderms, the Holothuroidea represents the class that is the most infested by parasites. Parasites of holothuroids are Bacteria, Protozoa and Metazoa. There are about 150 species of metazoans which parasite holothuroids. Most of them are turbellarians, gastropods, copepods, crabs or fishes. The main body compartments suffering of the infestations are the digestive system and the coelom. The diseases induced by metazoan parasites are mostly structural: they create galls at the surface of the epidermis, pierce the respiratory tree or dig into the body wall down to the coelom. Most metazoans that live in the digestive system do not induce obvious diseases and their relationship with their hosts is probably close to commensalism. Most Protozoa that parasite holothuroids are sporozoans. They occur mainly in the coelom and/or the haemal system, one species having been reported infesting the gonads. Even in heavily infested hosts, the signs of disease induced by sporozoans are low: at most, host haemal lacuna is occluded by trophozoites or cysts are formed into the coelomic epithelium. The most pathogen agents reported from cultured sea cucumbers are Bacteria. Cultivated holothuroids may suffer from a bacterial disease, called skin ulceration disease, that affects their body wall. In particular, juvenile Holothuria scabra reared in the Aqua-Lab hatchery of Toliara, Madagascar, suffered from such a disease that caused death within three days. The first sign of the infection is a white spot that appears on the integument of individuals, close to the cloacal aperture. The spot extends quickly onto the whole integument leading to the death of individuals. The lesions consist in a zone where the epidermis is totally destroyed and where collagen fibres and ossicles are exposed to the external medium. This zone is surrounded by a border line where degrading epidermis is mixed with connective tissue. Lesions include three bacterial morphotypes: rod-shaped bacteria, rough ovoid bacteria, and smooth ovoid bacteria. Three species of bacteria have also been put in evidence in the white spot lesions thanks to biomolecular analyses (DGGE and sequencing): Vibrio sp., Bacteroides sp., and an a-Proteobacterium. [less ▲]

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