A Comparative Study of Endoparasitism among some Southern California Lizard Populations

Abstract

A total of 1485 lizards from southern California, Mexico, Baja California, and nearby islands along the Pacific Coast and in the Gulf of California was examined between March 1962 and May 1964. Of these, 738 were collected from three plant communities in the San Jacinto Mountains. The lizards represented 7 families, 18 genera, and 26 species. The results suggest that differing prevalences of parasites at different altitudes may be attributed to: '(1) specificity to altitudinally zoned definitive or intermediate hosts; (2) presence of single or multiple poten- tial host species; (3) possible influence by humidity and temperature ranges of air and substrate, as indicated by altitudinal changes in plant communities. Significant differences in infection rates between the sexes occur only in haemosporozoan infections. There are two age group distributional patterns of parasites: high initial infection rates in young animals that show little or no decline with age, and a progressive increase of infection rates with host age. Hatchling lizards often acquire multiple protozoan infections almost immediately following hatching. Distributional patterns probably depend upon trans- mission sites, host behavioral changes with age, and vector seasonality. Certain flagellates show decreased infection rates in correlation with concurrent infection by pharyngodont nematodes, possibly dependent upon number of worms present. Seasonal fluctuation, where present, seems related to distributional patterns among host age groups, vector seasonality, changes in host phys- iology associated with reproduction, or the parasites' reproductive cycle. Host specificity exists at infraordinal, familial, generic, and specific levels, with coccidians, oxyurid nematodes, and some cestodes showing the most limited host distribution. Restriction to certain hosts is influ- enced by phylogeny, diet, habits, and habitat of hosts. The following parasites were found: at least seven flagellates Proteromonas, Monocercormonas, Hexamastix, Tritrichomonas, Chilo-