Comparative anatomy of the ciliary body of the West Indian manatee (Trichechus manatus) and selected species

OBJECTIVE: To examine the anatomy of the ciliary body in the West Indian manatee (Trichechus manatus), paying close attention to its vascularization and to compare to those of its distant relative, the African elephant (Loxodonta africana), the amphibious hippopotamus (Hippopotamus amphibius) and the aquatic short-finned pilot whale (Globicephala macrorhynchus). PROCEDURE: Specimens from each species were preserved in 10% buffered formalin, and observed stereomicroscopically before being embedded in paraffin, sectioned and stained by Masson trichrome, hematoxylin and eosin, and periodic acid-Schiff for light microscopic evaluation. RESULTS: The network of blood vessels in the ciliary processes of the West Indian manatee appear to have an intricate pattern, especially with regard to venous outflow. Those of the elephant are slightly less complex, while those of the hippopotamus and whale have different vascular patterns within the ciliary body. Musculature within the ciliary body is absent within the manatee and pilot whale. CONCLUSIONS: In general, there appears to be a direct relationship between the increased development of vasculature and the loss of musculature within the ciliary bodies of the aquatic and amphibious mammals presently studied. Specifically, the ciliary body of the West Indian manatee has a comparatively unique construction, especially with regard to its vasculature.