Master of Science in Education (MSEd)
Semester of Degree Completion
Frederick R. Schram
Two species of peracarid malacostracans, a mysid, Neomysis americana, and an oniscid isopod, Trachelipus cf. rathkei, were used to study the skeletomusculature system. Serial sections, whole mounts, and gross dissections were made. Coxal promotors and remotors and basal adductors and abductors were the muscle groups examined.
The promotor and remotor muscles of N. americana were found to be numerous, well developed, taking origin primarily from the dorsal thoracic wall, and extending nearly ventrally to insert in the coxa; the adductor muscle and two abductor muscles are weakly developed. The coxa in T. cf. rathkei is incorporated completely into the pleura of the thorax and is not directly functional in locomotion. Coxal muscles were observed in the isopod, but could not be easily distinguished due to this incorporation. Many large muscle bands, originating from the dorsal and dorsolateral thoracic wall, were observed. Some of these muscles are coxal and some are strictly thoracic. The basis of T. cf. rathkei is quite large and held parallel to the body during locomotion. The adductor series is composed of several relatively small muscle bundles. The abductor series has fewer elements, but the muscle bundles are large.
These muscle patterns reflect functional adaptations that occurred during specialization from a primitive, generalized form to an advanced, specialized form. These muscles were selected for modification and improvement in accordance with their functional possibilities during the peracarid adaptive radiation.
Gill, Donna R., "A Study of Thoracic Skeletomusculature in Peracarida (Crustacea)" (1972). Masters Theses. 3916.