Abstract

The integument of mammals is in direct contact with an external and influential environment that serves to determine its structure and functions. In marine mammals the skin acts as a barrier to the environment but also has several other roles, such as preventing dehydration, drag reduction, buoyancy control, and temperature regulation. Modifications of the skin can be used for reproductive or feeding purposes as well. Our understanding of the manatee (Trichechus manatus) skin is incomplete. Studying features that pertain to the manatee integument will give a clearer understanding of the roles that the integument can fulfill in an aquatic environment and will allow for a comparison to other marine mammals.

Samples were collected from 10 manatees at 25 sites on the body. These sites included both dorsal and ventral regions where applicable. These samples were analyzed morphologically through paraffin, frozen and plastic embedding, using a variety of stains including special stains for the extracellular matrix and immunohistochemical stains. Patterns can be seen both in the epidermis and the dermis with regard to location on the body. This is also seen in different stages of development. Organization of the epidermis was well developed dorsally and further developed ventrally, especially in the flipper and the fluke. Ventrally in the tip of the flipper, the epidermis has morphology similar to that of cow horns and the coronary band of the equine hoof. In most areas the dermis was well developed and very thick. Patterns in the dermis changed depending on the location on the body. These patterns range from a diagonal weave of collagen fibers to a crisscross pattern that is perpendicular to the epidermis. The only region of the integument that was seen to have glands present was in the eyelid. These glands were tarsal glands that aid in keeping the eye moist and free of pathogens. There is a very obvious amount of melanocytes present in the manatee skin. These melanocytes undergo a developmental pattern from birth to adult. In all samples analyzed, there are melanocytes present below the epidermis. This is normally due to trauma or damage to the basal layer of the epidermis or a deficiency in the immune system. In most mammals this is considered to be abnormal, but in the manatee this appears to be normal due to the fact that it is seen in all the samples analyzed.