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MYOCARDIAL ULTRASTRUCTURE OF TANAIS CAVOLINII (CRUSTACEA: TANAIDACEA) AND SOME PHYLOGENETIC CONSIDERATIONS

1986; Oxford University Press; Volume: 6; Issue: 2 Linguagem: Inglês

10.1163/193724086x00028

1937-240X

Are Nylund,

Marine Biology and Ecology Research

The heart of Tanais cavolinii is tubular and consists of an epicardium and a myocardium. The heart myofibers run from the dorsal to the ventral part of the heart tube. They are connected dorsally and ventrally by intercalated discs. The sarcolemma invaginates mainly towards the Z levels where a Tz-system is formed. Longitudinal tubules branch off from the Tz-system and expand as junctional cisternae at the H level. A few invaginations directly to the H level have been found. The sarcoplasmic reticulum forms a fenestrated sheath around the myofibrils, and it is modified at the H level where it participates in couplings. This arrangement of the membrane systems in T. cavolinii is similar to that of other eumalacostracans with the exception of isopods. This fact suggests a reshuffle of the traditional eumalacostracan systematics, where the tanaidaceans and the isopods are classified close to each other.