Meeting Abstract
Many soft-bodied invertebrates are remarkably effective burrowers despite their reliance on a flexible, fluid-filled hydrostatic skeleton. The aim of this study was to compare the shape and ontogenetic scaling of surface-dwelling and burrowing earthworm ecotypes to explore adaptations for burrowing in hydrostatic skeletons. We compared the external morphology of adult lumbricid earthworms across species and ecotypes to examine aspects of shape that are significantly associated with ecotype. We also compared the ontogenetic scaling of internal and external morphology of a burrowing species, Lumbricus terrestris, and a surface dwelling species, Eisenia fetida, using glycol methacrylate histology. We found that burrowing species had higher length-to-diameter ratios than surface dwellers, and that L. terrestris was thinner at any given body mass compared with E. fetida. We also found the differences in the size and development of the musculature between the two species that are likely correlated with surface crawling or burrowing. Our results suggest that adaptations for burrowing in soft-bodied animals include: a disproportionately thin body, robust anterior segments, and elaborate longitudinal musculature.
