P3.181 Friday, Jan. 6 A comparison of tardigrade muscular organization between species with different body form and habitat GROSS, Vladimir*; HOCHBERG, Rick; ATHERTON, Sarah; University of Massachusetts, Lowell; University of Massachusetts, Lowell; University of Massachusetts, Lowell Vladimir_Gross@student.uml.edu
Tardigrades (aka water bears) are microscopic, eight-legged, barrel-shaped invertebrates that dwell in permanently or temporarily wet environments. Tardigrades were first described over 200 years ago and to this day are characterized primarily by their external morphology. At present, most tardigrade research is focused on cryptobiosis and tardigrade relationships to arthropods, onychophorans and various “aschelminth” taxa. However, morphological studies intending to gain insight into the structure of organ systems or their utility in understanding intra-phyletic relationships are relatively rare. In this study, the muscular system of an intertidal marine tardigrade, Batillipes pennaki (Heterotardigrada, Arthrotardigrada), is compared to that of a semi-terrestrial species in an attempt to understand how this relatively conserved organ system may vary with body form and habitat. The study was performed using fluorescent labeled phalloidin and confocal laser scanning microscopy (CLSM) to create a 3D reconstruction of the muscular system of each species. Characters of the muscular system were then mapped onto a phylogeny of the Tarigrada – using newly generated molecular sequences - to view evolutionary trends in the architecture of the tardigrade muscular system. Because of a lower degree of variability compared to external characters, internal morphology of organ systems such as the musculature may be a more useful tool for gaining insight into the evolutionary history and intra-phyletic relationships of tardigrades.