California Sea Lion (Zalophus californianus)

For a marine mammal species, we have Zalophus californianus. They, along with seals and walruses, belong to a “fin-footed” group called pinnipeds. They can be found anywhere along the Pacific coast of North America, from Vancouver, Canada to Baja, Mexico. They sometimes gather in large masses to hunt for fish, such as off the coast of San Francisco where some consider them a nuisance. They are usually brownish-gray to silver in color with a thick coat of short fur and a heavy layer of fat under their skin to keep them warm in cold water.  Their bodies are smooth and streamlined which enables them to swim with little resistance.  Once at very dangerously low populations, the California Sea Lion, and all other marine mammals, are now protected by the MMPA (Marine Mammal Protection Act) of 1972.

In Meltmount™ 1.662, notice the unusual continuous globular medulla, with no visible scale pattern; in crossed polarized light there is low birefringence seen (Figure 16 & 17).

click image to enlarge (166K) Figure 16

click image to enlarge (183K) Figure 17

The cross-section shows the hair to be a cigar shape with a narrow medulla.  Some pigmentation can be seen. The medullary index was calculated to be 0.32 (Figure 18).

click image to enlarge (347K) Figure 18

A scale cast was made to determine the scale pattern; the cast shows a distinct, irregular wave pattern, with margins that are near with crenate edges (Figure 19). The SEM image, take at X600, 5 kV, was difficult to capture; the first attempt was unsuccessful because of the absence of a scale pattern. Finding this to be extremely unusual, a second attempt was made with the hairs turned over. The loss of the scale pattern on the exposed side of the hair (first attempt) is due, possibly, to streamlining in the water. The underside, or protected side (second attempt), revealed that there are 16-20 scales per 100 µm and that this sample is ~150 µm in width (Figure 20). The angle at which this image was captured shows the loss of scales occurring toward the top of the image.

click image to enlarge (190K) Figure 19

click image to enlarge (402K) Figure 20