The mechanics of swallowing and the muscular control of diverse behaviours in gopher snakes

Snakes are excellent subjects for studying functional versatility and potential constraints because their movements are constrained to vertebral bending and twisting. In many snakes, swallowing is a kind of inside-out locomotion. During swallowing, vertebral bends push food from the jaws along a substantial length of the body to the stomach. In gopher snakes (Pituophis melanoleucus) and king snakes (Lampropeltis getula), swallowing often begins with lateral bending of the head and neck as the jaws advance unilaterally over the prey. Axial movement then shifts to accordion-like, concertina bending as the prey enters the oesophagus. Once the prey is completely engulfed, concertina bending shifts to undulatory bending that pushes the prey to the stomach. The shift from concertina to undulatory bending reflects a shift from pulling the prey into the throat (or advancing the mouth over the prey) to pushing it along the oesophagus towards the stomach. Undulatory kinematics and muscular activity patterns are similar in swallowing and undulatory locomotion. However, the distinct mechanical demands of internal versus external force exertion result in different duty factors of muscle activity. Feeding and locomotor movements are thus integral functions of the snake axial system.

Coccidian parasites of the California Banded King Snake, Lampropeltis getulus californiae

Three coccidian parasites were found in California Banded King Snakes, Lampropeltis getulus californiae: Isospora crotali, an intestinal Eimeria, and a haemogregarine. Schizogonous stages of the latter occurred predominantly in liver, and were remarkably similar to those described for other blood Coccidia.Dr Charles E. Shaw of the San Diego Zoological Society identified the snakes, and Dr Gordon Ball, Professor of Zoology at the University of California, Los Angeles, kindly reviewed the manuscript.