A

B

C

Bottom resting Feeding

Swimming Courtship

Hartman, 1979

Manatees

•Strategies to stay on bottom at low cost

• Dense and heavy bones

• Dense skin

• Large lungs

Ballast

Maneuverability

•Pectoral flippers or tailfluke

•Contractions of hemidiaphragms

• Position in water column

• Pitch and roll

Rommel and Reynolds, 2000

Rommel and Reynolds, 2000

Manatee diaphragm

Rommel and Reynolds, 2000

Compartmentalization

•Need to be distinct muscular units

• Separated by connective tissue elements

• With separate sources of innervation

•Termed “neuromuscular compartments”

Hypothesis

Manatee hemidiaphragms are compartmentalized.

Methods

•Gross anatomical studies

Connective tissue elements

Phrenic nerve

VC Bundles

Connective tissue elements

VC Bundle

Connective tissue elements

VC Bundles

X XX

Multi-directional fibers

M. Newson, 1996

Manatee Diaphragm

Intrinsic Tongue Muscles

Conclusions

•VC bundles separate diaphragm into 1.0 cm-wide blocks

•Muscle fibers insert into VC bundles

•Branches of phrenic nerve innervate groups of blocks

•Compartments may be composed of groups of blocks

D. Perrine, 2001