The pineal gland structure and ultrastructure in the Northern (Blarina brevicauda) and Southern short-tailed shrew (Blarina carolinensis) are described by light and electron microscopy. Results observed were similar to other mammals of Insectivora described previously, specifically, the hedgehog (Erinaceus europaeus) and the Old World mole (Talpa europea). Two different types of pinealocytes were noticed by electron microscopy, in addition to relatively few glial cells. Granular vesicles were not noticed in abundance. The granular endoplasmic reticulum was observed and studded with vesicles. The golgi apparatus was well developed and appeared often. Synaptic ribbons were observed in several different formations consisting of ribbons and/or rods. The ciliary derivative, the rudimentary photoreceptor structures found in the pinealocytes of population I, was noticed in a 9 + 0 tubular pattern. Within these semifossorial shrews, the relationship between specific intracellular organelles and their function was discussed.
Keywords: Electron microscopy; Hedgehog; Light microscopy; Mole; Pineal gland; Shrew; Ultrastructure.