Morphological and functional adaptations of nematodes to habitat types

Sediment grain-size is a key factor in structuring meiofaunal and nematode assemblages. Accordingly, a statistical analysis was carried out on a data set of samples collected in two different scientific cruises in the Maldivian archipelago. We tested possible variations of some morphological and functional characters of marine nematodes (buccal cavity, amphid shape, cuticle ornamentation, tail shape, and life strategy) to variations in sediment grain size and hydrodynamic conditions. In the first survey, possible changes of morphological and functional characters were analysed in fine to very coarse sands. All the characters were significantly different between the sediment types. In particular, medium-coarse sands appeared the most diversified sediments both in taxonomical and morpho-functional diversity. Cuticle ornamentation and life strategy were well diversified also in very coarse sands, while tail shape was especially diversified only in fine sediments. When the same traits were analysed to test the influence of different levels of hydrodynamism, all of them(with the exception of tail shape) were significantly different and more diversified in intermediate energy conditions. In conclusion, medium-coarse sands, and habitats with intermediate energy level appeared to favour not only a great taxonomical diversity, but also a great diversity of morphological and functional adaptations that reflects their great heterogeneity in micro-niches.