Salivary glands from males of 3 Dermacentor species (D andersoni, D variabilis and D occidentalis) that were infected with either the Virginia or Idaho isolate of Anaplasma marginale as nymphs or adults were examined for colonies of A marginale by use of light and electron microscopy. Prior to dissection of salivary glands, exposed ticks were held at 25 C for 15 to 18 days, followed by a 3-day incubation at 37 C. Ticks of 2 species transmitted A marginale to calves; the third tick species was confirmed infected by demonstration of typical colonies in tick gut cells, but transmission was not attempted; Colonies of A marginale were seen with light microscopy in salivary glands of all 3 species of ticks; they were located in acinar cells that contained simple granules. Colonies varied morphologically from small, compact ones to larger structures that contained distinct organisms and often were adjacent to the host cell nucleus. Electron microscopy confirmed that the colonies were rickettsial organisms. Morphologic features of A marginale varied and included reticulated forms, forms with electron-dense centers, and small particles; these various forms were similar to those described previously in midgut epithelial cells of ticks. We believe that the organism seen within tick salivary glands may replicate in the glands before its transmission to the vertebrate host.

Ixodes signatus nymphs were subjected to the scanning electron microscopy for the observation of the major physiological sense organs including Haller's organ. Funger prints and variable sensory setae were found on the body surface, and especially well developed setae were identified on the article IV and on the anal lobes. A central button-like organelle and numerous small holes were found in the spiracular plate. The Haller's organ was identified at the distal point of the tarsus I and regarded as the major sensory organ, chemoreceptor. Two types of sensory setae were observed, the shorter ones in front of the organ and the longer ones in distal front as well as behind the organ. The fully opened organ was ellipsoidal and a total of seven basiconic sensory pegs rooted deeply and shaped like well arranged hooks were found inside the organ