Meeting Abstract
Mystacocarida is a poorly known group of marine microscopic crustaceans characteristic of the interstital (meiobenthic) environment. While only 13 species are described worldwide, the taxon figures prominently in discussions of crustacean relationships because of their presumably plesiomorphic morphology. In this study, we examined the architecture of the musculature in Brazilian specimens of Ctenocheilocaris armata to determine if muscle patterns could contribute to our understanding of mystacocarid behavior and phylogeny. Using a filamentous actin marker in combination with confocal laser scanning microscopy and 3D reconstructive software, we mapped the somatic musculature of the appendages, cephalon, thorax and abdominal regions, and the splanchnic musculature of the fore-, mid- and hindgut. Our results show that the somatic musculature is dominated by longitudinal muscles that form three distinct patterns: an anterior-posterior pattern with muscles that span the length of the thorax and abdomen; a dorsoventral pattern wherein dorsal longitudinal muscles make segmental, ventrolateral insertions; and a ventrodorsal pattern wherein ventrolateral longitudinal muscles make dorsolateral insertions. We confirm earlier observations about the complex musculature of the intestine in mystacocarids, which includes strong dilator and circular muscles around the foregut, while mid- and hind-gut regions are dominated by numerous circular muscles. The layering of the circular and longitudinal muscles appears to differ from that described for species of Derocheilocaris. Additional details of the musculature are presented and compared to previous results on additional species.
