title: Heart ultrastructure in Lepidurus arcticus Pallas (Crustacea, Branchiopoda, Notostraca).
abstract: The heart of Lepidurus arcticus consists of an epicardium and a single layer of strongly polarized myocardial cells, 10-50 micron thick, with the myofibrillar part facing the epicardium. The Z-bands are diffuse and some Z-material forms attachment plaques. Relaxed sarcomeres show a hexagonal arrangement of thick filaments and 6 thin filaments in orbit, but filaments often diverge in their orientation. The sarcolemma invaginates from both the epicardial and the endocardial side of the cell, forming clefts and T-tubules. The sarcoplasmic reticulum is loosely reticular, cisternae associate with sarcolemma to form large and typical peripheral and interior couplings. The latter are of the "button-to-button" type and they tend to be located at the A-I level.
mesh_terms: D000818:Animals; D003445:Crustacea / Q000648:ultrastructure*; D003599:Cytoskeleton / Q000648:ultrastructure; D008929:Mitochondria, Heart / Q000648:ultrastructure; D009206:Myocardium / Q000648:ultrastructure; D009210:Myofibrils / Q000648:ultrastructure; D012508:Sarcolemma / Q000648:ultrastructure; D012519:Sarcoplasmic Reticulum / Q000648:ultrastructure