Richard C. Snyder

Quadrupedal and Bipedal Locomotion of Lizards

SINCE the appearance of previous work on the bipedal running of Basiliscus basiliscus (Snyder, 1949), the motion picture analysis method of studying locomotion has been applied to several species of lizards. High speed motion pictures were taken of Amphibolurus cristatus (Agamidae), Crotaphytus c. collaris, Gambelia w. wizlizenii and Sceloporus u. undulatus (Iguanidae), and Cnemidophorus t. tessellatus (Teiidae). Quadrupedal locomotion of all species was photographed as well as the bipedal running characteristic of Amphibolurus, Crotaphytus and Gambelia. Motion picture photography of running lizards presents several problems. Standard motion picture cameras operating at a maximum speed of 64 frames per second are inadequate to cope with the rapid leg action of the animals and when separate frames are projected for analysis, detail is greatly obscured, particularly in regard to position of the feet. Consequently, photography was done with an Eastman Kodak 16 mm. High Speed Camera equipped with a Kodak Anastigmat 63 mm. f/2.7 lens. Fifty-foot spools of Cine-Kodak Super X panchromatic reversal film were used exclusively. Since it was necessary to provide at least a three-foot running area, and since the high camera speed requires intense illumination, nine reflector photospot lamps were mounted to cover the running track about two feet from the sand on which the lizards ran. It was necessary to place a sheet of heavy, heat absorbing glass between the lights and the running track; otherwise the sand rapidly became too hot for the lizards to tolerate. With this lighting arrangement good results were obtained with a camera speed of between 1000 and 1500 frames per second (exposure time per frame between 1/5000 and 1/5500 second), a speed adequate to fix leg and foot motion completely. Tests made at higher speeds resulted in underexposure. Increasing the illumination by concentrating three or more photospots at any one point solved the underexposure problem but created a new one; the lizards would not perform in such brilliant light. The basic factors influencing the gaits of quadrupedal mammals as well as descriptions of the types of gaits employed have been clearly set forth by Howell (1944) and his assumption that the speed gait of lizards is the trot has been verified by the present studies. The description of quadrupedal locomotion to follow applies basically to all of the five species studied. The action of a hind leg illustrates the basic pattern of movement for all four appendages. The propulsive stroke begins when the foot strikes the ground, at which time the foot and shank are extended and the

Comparative Features of the Life Histories of Ambystoma gracile (Baird) from Populations at Low and High Altitudes

during the first year, others did not metamorphose until the second spring, while still others remained in the water as paedogenic forms for an unknown length of time. While Watney based her conclusion of paedogenesis on a 125-mm. gravid larva and upon longevity records of 2% and 4 years for captive larvae, Slater (1936: 234) has furnished the sole description of egg deposition by a larval animal. In Pierce County, Washington, depending upon season and altitude, egg deposition (by adults) may occur from January to mid-July (Slater, 1936: 235). Carl (1943: 28) indicated that at sea level in British Columbia

Vertebral Counts in Four Species of Suckers (Catostomidae)

RECENTLY, Raney and Lachner (1947) described Hypentelium roanokense, a dwarf species of hog sucker adapted to life in small mountain streams of the upper headwaters of the Roanoke River system. It shares the Roanoke system with Hypentelium nigricans (LeSueur), the widely ranging species sometimes found in the same habitat. It differs from nigricans in having a heavier body with a foreshortened trunk, scales and pectoral rays markedly reduced in number, longer anal and dorsal fins, larger and less inferior mouth, and in several pigmentary features. In addition, the posterior fontanelle is reduced to a narrow slit and the posterior lobe of the air bladder is short and thin. Vertebral counts were made of the above two species of Hypentelium to determine the degree of differentiation that exists, if any, and to discover whether or not the reduction in number of scales of Hypentelium roanokense is paralleled by a reduction in vertebral number. Similar counts were made on Catostomus c. catostomus (Forster) and Catostomus c. commersonnii (Lacepede), since these species also differ in scale counts, the latter having the smaller number in the lateral line. The vertebral counts were made after the manner described by Hubbs and Lagler (1947) by examination of the negatives of roentgenograms, except for those of Catostomus c. commersonnii in which the vertebrae were counted in situ after dissecting off one complete side of the fish. The roentgenograms were made of the lateral aspects of the fish with a Westinghouse 150 KV pedestal-mounted X-ray unit on 14 X 17 Type M industrial film. All fish were X-rayed at 50 KV, 15 milliamps at 45 seconds for the larger fish and 40 seconds for very small ones (60 mm. or less). The best results were obtained by omitting the use of a lead screen between the film and the fish. Gosline (1948) and Bailey and Gosline (1948) have recently indicated the value of using X-rays for ichthyological work. At first, some difficulty was experienced in counting the vertebrae due to the presence of the Weberian ossicles. Krumholz (1943) stated that in ostariophysine fishes these structures are derived from the first four vertebrae. Watson (1939) noted that in the goldfish, Carassius auratus (Linnaeus), the fourth vertebra bears a rib. Studies of suckers, cleared and stained with alizarine, confirm the findings of both. The vertebrae of these suckers were counted by beginning with the fourth (the first rib-bearing) vertebra and then adding three to the total. The distribution of the vertebral counts is shown in Table I. The range in numbers of vertebrae for all four species is from 38 to 48, a considerably greater range than the numbers (45 to 47) given by Jordan and Gilbert (1882) and Jordan and Evermann (1896) for all Catostomus (including IHypentelium nigricans). Guinther (1868) stated that there are 47 vertebrae in Catostomus commersonnii (teres).