Jean-Claude Bussers

Chitinous cuticle and systematic position of tardigrada

Abstract The chitinous nature of the cuticle, jaws and stomodaeum of three species of Tardigrada has been definitely proven using a specific micromethod involving a preparation of purified chitinase. These chemical characteristics are in favour of the phylogenetic closeness between Tardigrada and the Arthropoda.

Ultrastructural localization of chitin in the cystic wall of Euplotes muscicola Kahl (ciliata, hypotrichia)

The ultrastructural localization of chitin in the cyst walls of Euplotes muscicola was carried out after deproteinization and by specific labelling with WGA-gold complex. The overall ectocyst contains chitin that alone can sustain the exact profile of this cystic layer. In the endocyst, electron clear sublayers include chitin and alternate with other sublayers probably of proteic nature.

Biomonitoring of the Water Quality in the River Warche (Belgium): Impact of Tributaries and Sewage Effluent

Between March 1994 and March 1995, sampling campaigns were carried out each fortnight in order to determine the physical, chemical and biological quality of the water in the river Warche. Macroinvertebrate and rotifer biomonitoring (based on the global and Belgian biotic index and on the Sladecek index respectively) were used as bioindicators. These biotic indices were related to the main physical and chemical parameters monitored between the source and the town of Malmedy (i.e., a river length of 40 km). Important seasonal and longitudinal changes of physical, chemical and biological water quality occur. The deterioration of the water quality in the river Warche is obvious in two sectors of the river. Strong organic pollution and eutrophication were observed between the source and the sampling station located downstream of Bullingen. Indeed, along this sector, tributaries, sewage and dairy effluent flow into the Warche and induce significant increase of nitrate, nitrite, ammonium and phosphate concentrations. As a consequence, biotic indices decrease significantly downstream of Bullingen and the most abundant rotifer species are clearly eutrophic indicators. Another important decrease of water quality was observed downstream of an important paper mill effluent which induces a significant increase of temperature and of nitrite and sulphate concentrations. The presence of two lakes along the Warche course induces downstream either a restoration of the water quality during a mixing period of the lake or an increase of ammonium and phosphate concentrations after water stratification as a result of a temperature gradient in the lake.

Morphology of the buccal apparatus and related structures in four Carapidae

The aims of this study were (1) to compare the morphology of the buccal apparatus, the suspensorium and the opercle in four species of Carapidae (Carapus acus, Encheliophis boraborensis, Encheliophis homei and Encheliophis gracilis) and (2) to investigate the relationships between their cranial anatomy, their carnivorous diet, and their well known ability to enter holothurians. The complex and strong dentition and the wide hyomandibular with thickenings that seem to suit the constraints of the adductor mandibulae muscles partly inserted on the neurocranium are signs of a carnivorous diet. C. acus, E. boraborensis and E. homei have extremely strong buccal pieces and can protrude their upper jaws. However, in E. gracilis, the jaws are more slender, and the insertions of the A1 along the entire length of the maxillary associated with the lack of mobility between the maxillary and the premaxillary prevent buccal protrusion. These differences could be related to the diet: C. acus, E. boraborensis and E. homei can feed on fishes and crustaceans, whereas E. gracilis feeds only on holothurian tissue. The cephalic morphology of the four species is not incompatible with entering the host. However, the neutralisation of the suboperculum spine by ecartilaginousi tissue could be considered to be a particular adaptation to this behaviour.

Chitin Degradation in Natural Environment (Mollusk Shells and Crab Carapaces)

Most marine sediments are organodetritic in nature, and many particles of the coarser fraction are constituted of more or less stable remains of biological origin (skeletal pieces of benthic or planctonic animals, plant remains,…)(1). In this respect, dead crustacean cuticles and mollusk shells introduce into the sediments the chitinoproteic compounds of their matrix, closely associated to calcified crystallites.

Chitin Production by Animals and Natural Communities in Marine Environment

Since the discovery of the remarkable properties of chitin and of its derivative, chitosan, offering a wide range of possible industrial and agricultural applications 1,2,3, the need of new and trusting sources of chitin for its isolation on an industrial scale was claimed.