title: Correlations between ultrastructural features and contraction rates in rotiferan muscle. I. Preliminary observations on longitudinal retractor muscles in Trichocerca rattus.
abstract: The Rotifer Trichocerca rattus has striated longitudinal retractor muscles. These muscles can be divided into two categories: 1. The central and ventral retractor muscles which, after fixation, are found in a supercontracted state: they probably contract very quickly. 2. The lateral retractor muscles which are in a relaxed state after fixation. However, if the animal is mechanically stimulated before fixation, these are also fixed in a contracted state: so, normally, these muscles probably contract more slowly than the first category. In the relaxed state, thin myofilaments of the lateral retractor muscles are folded at the I band level; this a consequence of their compression provoked by the contraction of central and ventral retractor muscles. In muscles of the first type, the thick myofilaments are shorter (less than 2 mu) than in the second type (2.5 mu).
mesh_terms: D000818:Animals; D009119:Muscle Contraction; D009132:Muscles / Q000648:ultrastructure*; D051381:Rats; D012403:Rotifera / Q000033:anatomy & histology*; D013997:Time Factors