Diaphragm structure and function in the Florida manatee (Trichechus manatus latirostris)

Abstract

Relative to many other mammals, little is known about the functional morphology of the four extant species of the order Sirenia. In this study, 166 Florida manatee (Trichechus manatus latirostris) carcasses fresh enough to collect detailed anatomical information were examined to describe the gross anatomy of the diaphragm. Our results show that the Florida manatee's diaphragm differs from those of other mammals in that it: lies in a dorsal plane, rather than in the more typical transverse plane; is located dorsal to the heart and does not attach to the sternum; and attaches medially at the "I"-shaped central tendon to bony projections extending ventrally from the vertebral bodies, forming two distinct hemidiaphragms. The manatee's transverse septum is a separate structure that lies at a right angle to the diaphragm and separates the heart from the liver and other viscera. The extreme muscularity of the diaphragm and the ability of manatees to adjust their position in the water column with minimal external movement suggest that diaphragmatic contractions may change the volume of each pleural cavity to affect buoyancy, roll, and pitch. We also hypothesize that such contractions, in concert with contractions of powerful abdominal muscles, may compress gas in the massive large intestine, and thereby also contribute to buoyancy control.

THE VOCALIZATION MECHANISM OF THE FLORIDA MANATEE (<i>TRICHECHUS MANATUS LATIROSTRIS</i>)

“…Additionally, our silicone modeling technique allowed us to visualize both primary bronchi as well as the secondary and tertiary bronchi. These long, straight primary bronchi were expected because manatees possess unusual elongated dorsal lungs, as well as hemi-diaphragms (Rommel and Reynolds, 2000;Reynolds et al, 2002;Rommel and Lowenstein, 2001). It is also interesting to note the presence of unusually large Eustachian tubes in our model, attached to the pharyngeal region, as observed first by SA Rommel (personal communication).…”

Silicone Modeling of the Interior Spaces of Hollow Organs: Use in Dog and Manatee Respiratory Tract and in a Beef Heart

“…9a), along with secondary and even tertiary bronchi. These long, straight primary bronchi were expected because manatees possess unusual elongated dorsal lungs that run almost the entire length of the body, as well as hemi-diaphragms (Rommel and Reynolds, 2000).…”

Functional morphology of venous structures associated with the male and female reproductive systems in Florida manatees (Trichechus manatus latirostris)†

“…The manatee's intra-abdominal testes lie on the ventral aspects of the hemidiaphragms (as described in Rommel and Reynolds (2000)) and are positioned on the caudolateral margins of the kidneys (Fig. 1).…”

“…The epididymides originate along the craniolateral margins of the testes. The tails of the epididymides extend caudolaterally and slightly ventral to the testes and are positioned in the hypogastric fossae, shallow diverticulae of the abdomen between the last two or three ribs (Murie, 1872;Rommel and Reynolds, 2000). In female manatees, the distal uterine horns, uterine tubes, and ovaries are positioned caudolateral to the kidneys in the hypogastric fossae (Fig.…”

“…1). The ventral skin, fat, and abdominal muscles were removed slightly ventral to the distal tips of the ribs to expose the abdominal organs (Bonde et al, 1983;Rommel and Reynolds, 2000).…”