Meeting Abstract
Sessile rotifers of the clade Gnesiotrocha secrete a wide variety of gelatinous tubes around their bodies that function as refugia from predators. Based on previous results using energy dispersive x-ray spectroscopy (EDS), we found that these secretions consist mostly C and O, with smaller proportions of other elements such as N, Si, Na and Mg, among others. Here we examine the ultrastructure of the tubes from three species (Floscularia conifera, Limnias sp., and Stephanoceros millsii) to characterize their composition and determine whether they possess features that provide insights into their physical appearance. Results for F. conifera confirm earlier observations that the tubes consist of an inner lining of “mucus” and outer construction of pellets. The “mucus” lining is electron dense and up to 0.5 μm thick. The pellets are lined by a thin membrane and are heterogeneous in content. By contrast, the hardened tube of Limnias is somewhat fibrous and of homogeneous construction, with a smooth inner surface and an outer surface of ridges. The soft gelatinous tube of S. millsii differs from the others in that it is mostly electron lucent and with a layered construction – the outermost layer is slightly more electron dense than the underlying layers – all of which contain fibers that loosely interconnect and may provide structure to the gelatinous mass. These tube characteristics are being used as part of a larger ongoing study of the evolution of the sessile lifestyle in gnesiotrochans.
