On the morphology and organization of the eye of unfed adult Rhipicephalus evertsi mimeticus (Acari: Ixodidae).

Investigations by scanning and transmission electron microscopy and freeze-etching revealed that eyes of adult Rhipicephalus evertsi mimeticus consist of a lens and photoreceptor cells, which are separated by an acellular layer and the hypodermis. The lens contains numerous pore channels, which open beneath the epicuticula of the outer portion, converge uninterrupted to the inner closure and end in approximately 420 pore fields. The inner closure of the lens is formed as a deep circular invagination. Beneath the hypodermis and perpendicular to the lens, a group of approximately 20 highly differentiated photoreceptor cells in a rosette-like arrangement is localized within the invagination of the lens. Each photoreceptor cell is characterized terminally by numerous, tightly packed and parallel-running microvilli, which are oriented perpendicularly to the lenticular pore channels.