Body size distribution of free-living marine nematodes from a Caribbean coral reef

Abstract

Body size is a fundamental property of organisms but its distribution is almost unknown for marine nematodes. We measured the length and width of 7446 nematodes of 186 species to describe their morphological landscape and the relationship between abundance and body size. The body shape has a bimodal distribution with two morphotypes, suggesting adaptations to lifestyle. In fine sediments (seagrass bed), slender nematodes dominated, whereas sandy sediments had mostly stout nematodes but also slender forms. Seaweed turf from hard bottom substrates may favour mostly slender nematodes, whereas dead coral harbours both morphotypes, probably as a result of high heterogeneity of the substrate. The size spectra of abundance vs mass class shows a negative exponential relationship, suggesting that the energetic equivalence hypothesis holds for nematodes. The shape and position of the size spectra depended on the type of habitat. Body size is an important organismal trait that offers valuable information for disentangling ecological patterns in Nematoda.