title: The morphology and maturation of the optic tectum of the small shark (Hemiscyllium plagiosum): a morphometrical, ultrastructural and histochemical study.
abstract: The morphometrical, ultrastructural and histochemical aspects of the optic tectums of the sharks (Hemiscyllium plagiosum) of different sizes were studied. The 1,000 g animals revealed 2 areas of heavy neuronal concentration. Ultrastructural studies showed an increase in the sizes of tectal neurons and in the sizes of myelinated fibers as well as an increase in the branching system of neurons as the animal matured. A change in the ratio of the types of synaptic contacts was evident in the larger animals. 3 types of glia cells were also observed in these animals. Histochemical studies indicated very little difference between the animals of different sizes except a possible increase of cytochrome oxidase activity.
mesh_terms: D000818:Animals; D008854:Microscopy, Electron; D012754:Sharks / Q000033:anatomy & histology*; D013477:Superior Colliculi / Q000166:cytology / Q000254:growth & development / Q000648:ultrastructure*