HISTOCHEMISTRY OF MUSCLE SPINDLES IN SNAKES OF NATRIX SPECIES

Abstract

The muscle spindles of snakes consist of a single intrafusal fiber; in addition to this, two types of spindles are found. We have studied the histochemistry of the snake intrafusal fibers. One type of spindle, the long capsule spindle intrafusal fiber, is characterized by high levels of the enzymes myosin adenosine triphosphatase, succinic dehydrogenase and phosphorylase; the other type, the short capsule spindle intrafusal fiber, is characterized by low levels of myosin adenosine triphosphatase and phosphorylase and an intermediate level of succinic dehydrogenase. The short capsule spindle intrafusal fiber is thus histochemically similar to the tonic extrafusal fibers, whereas the long capsule spindle intrafusal fiber is similar to the twitch extrafusal muscle fibers. The long capsule spindle is concerned mainly with monitoring static length, the short capsule spindle with monitoring changes in length. It is interesting that the histochemical profiles of long and short capsule spindle intrafusal fibers are similar to the mammalian bag and chain fibers, respectively.