Journalof Herpetology,Vol. 20, No. 3, pp. 318-324, 1986 Copyright 1986 Society for the Study of Amphibians and

Prevalence and Virulence of a HaemogregarineParasite of the Aruban Whiptail T.izard, arubensis

Jos. J. SCHALL

Departmentof Zoology, University of Vermont,Burlington, Vermont 05405, USA

ABSTRAcr. - Cnemidophorus arubensis, an endemic teiid of Aruba island, Netherlands An- tilles, is parasitized by a haemogregarine protozoan. The proportion of infected (preva- lence) was greater for males than females and for adults compared to juveniles. Brightly colored males were more likely to be infected than blandly colored males of the same body size. Percent of erythrocytes infected with parasite gametocytes, and parasite prevalence, were similar in both wet and dry seasons. Infected and noninfected were similar for several hematological, phys- iological, anatomical, and behavioral measures of parasite virulence. The Aruban haemogregarine appears to have an avirulent effect on Cnemidophorus arubensis.

Most lizard populations harbor a undergo asexual reproduction in the broad variety of parasites, including liver and produce sexual cells, or ga- protozoans, helminths, and ectoparasit- metocytes, which infect host erythro- ic arthropods (see Telford [1970] for an cytes. Some haemogregarines are example of a model survey). Despite the known to cause severe liver damage in abundance of lizard-parasite associa- mammalian hosts (Miller, 1908; Hoogs- tions, reliable data on the effects of par- trahl, 1961; Furman, 1966); their effects asites on their saurian hosts are scarce. on lizards are unknown. Some parasites, though, do play a sig- Here I examine the patterns of prev- nificant role in the biology of lizards. alence (%of hosts infected) and the vir- For example, infection with the malar- ulence of a haemogregarine that infects ial parasite Plasmodium mexicanum re- the Aruba island whiptail lizard, Cne- sults in severe hematological, physio- midophorus arubensis. Comparisons in logical, behavioral, and reproductive prevalence are made between wet and consequences for its vertebrate host, dry seasons, between male and female Sceloporusoccidentalis (Schall et al., 1982; hosts, and among host size classes and Schall, 1983a, b). P. mexicanummay be a color patterns of males. The latter is in- typical protozoan blood parasite in its teresting because adult male C. arubensis effects on its host, or it may be an un- are polymorphic in color, ranging from usually virulent species. The lack of bright blue with white spots to brown comparative data on other species of with brown stripes (Schall, unpubl. ob- parasites makes general statements on ser.). Hamilton and Zuk (1982) have the virulence of lizard parasites highly proposed that bright colors in male an- speculative. imals may vary with parasite burden The haemogregarines are among the and provide females with information most common protozoan parasites of on the fitness of potential mates. Final- lizards. These organisms are related to ly, I examine several measures of para- Plasmodiumand may resemble the an- site virulence; most of these measures cestral form of the malarial parasite are similar to those used in the studies (Manwell, 1977). Haemogregarines most of malaria in Sceloporusand thus pro- often utilize two hosts, a blood-feeding vide comparative information on the invertebrate and a vertebrate, such as a virulence of protozoan parasites of liz- lizard. Most haemogregarines of lizards ards.

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MATERIALS AND METHODS and fat mass were corrected for size as organ mass/body mass. The mass Cnemidophorusarubensis is a common of internal organs of vertebrates typi- endemic teiid of the island of Aruba, cally do not scale linearly with body Netherlands Antilles. Aruba experi- mass (Calder, 1984), so only the largest ences a pronounced wet-dry seasonal lizards of each sex were used for anal- cycle; the rainy period commences in ysis (&6,mass > 20 g; $9 mass > 9.5 g). September and ends in February. Liz- Live whiptail lizards were brought ards for this study were observed and into the laboratory and maintained in collected during October 1980, March large pens, 2m x 1 m, or 2 m x 0.5 m 1984, and November 1984, thus cover- in size, outfitted with a substrate of soil, ing both wet and dry seasons. As indi- sand, rocks, logs, and cardboard hiding cated in the Results section, not all kinds places. Overhead were heat lamps and of data described below were gathered full-spectrum fluorescent fixtures. Dog- for each sample period. food, and occasionally crickets, were Aruban whiptails were collected by provided daily. noosing or in funnel traps baited with After starving the animals for two tomato and canned tuna. That same days, resting 02 consumption, maximal evening, a blood sample was extracted 02 consumption, and running stamina from the postorbital sinus of each liz- were measured using methods adapted ard, using a heparinized capillary tube. from Bennett and Gleeson (1976) and Thin blood smears were made, fixed in Bennett (1980). For determination of absolute methanol, and later stained for resting 02 consumption, male lizards 50 minutes with Giemsa 1:10 at pH 7.2. were placed in a 232 ml airtight glass Hemoglobin concentration of the blood chamber within a darkened incubator was determined using a colorimetric set at 39?C, the typical body tempera- method (Brown, 1984). Five ml of cyan- ture of active Cnemidophorus (Schall, methemoglobin reagent and 0.02 ml 1977). Tubes entering and leaving the whole blood were mixed and read at chamber passed through a peristaltic 540 nm on a Bausch & Lomb Mini 20 pump, then through columns of drier- spectrophotometer. Readings were ite to remove water vapor and ascarite compared to those taken with dilutions to remove CO2, and finally to a Beck- of a hemoglobin standard (Hycel, Inc.). man E2 oxygen analyzer. The system Each collected animal was sexed, remained open for at least one hour, and measured (SVL), and scored for dorsal then closed to record 02 consumption. color pattern. The March 1984 sample Approximately 400 ml of air circulated was scored from living animals using through the closed system; the exact four color classes: (1) bright blue with volume depended on the volume of the pale blue spots on flanks; (2) blue-brown enclosed animal. When a very tight lin- with white spots; (3) brown with blue ear drop in 02 content of the contained spots; (4) brown with brown stripes. The gas indicated the animal was at rest, October 1980 sample was scored from readings commenced and were taken preserved animals which had experi- over at least an hour. enced color fading; therefore, color Maximal oxygen consumption was classes 2 and 3 had to be combined. C. indexed using animals that had been arubensisis easily sexed by the presence starved several days. Each lizard was in- on males of spur-like anal scales. A sam- dividually placed into a cloth sack, then ple of animals was preserved in 10% stored for several hours in an incubator formalin solution, and later dissected to set at 39?C. The lizards were then taken determine mass of the liver, inguinal individually into an environmental fat bodies, and testes (for males). Liver chamber set at the same temperature.

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Each animal was chased around a card- metocytes measured were: length 15.0 , board running track (5.7 m around x (SD = 1.3) and width 6.0 A (SD = 0.64). 17 cm wide) for 30 sec at its maximal Lengths ranged from 12.8 , to 16.8 ,. running speed. The observer promptly Parasitemia of gametocytes in eryth- placed the lizard into a 235 ml glass ves- rocytes was low. Of 60 randomly se- sel outfitted with sampling ports. After lected infected lizards, 39 showed par- 2 min, a sample of gas could be extract- asitemia <1/10,000 red blood cells ed and compared to a sample taken just (RBC) and the highest seen was only before the trial began. Results for both 394/10,000 RBC. Samples from the wet resting and maximal oxygen consump- season of 1980 and dry season of 1984 tion are corrected to STP conditions and showed very similar parasitemia: 19/30 reported as ml per g of lizard per h infections in the wet season and 20/30 (VO2/g h). in the dry season had parasite loads < 1/ Each animal was returned to the in- 10,000 RBC. There was no significant cubator the next day for several hours difference between seasonal samples for of rest in individual cloth sacks and then those infections with measurable para- run at maximal speed around the track. sitemia (Mann-Whitney U test; P > Distance run by the lizard was recorded 0.05). after 30 sec and 2 min of running. This Haemogregarine prevalence did not measure of locomotive stamina, though differ between wet and dry season sam- simple, is reproducible among animals ples (Table 1; x2 tests, P > 0.05). Parasite (Bennett, 1980). prevalence was higher for male than fe- Blood smears were scanned for pres- male lizards (Table 1). In males, preva- ence of parasite gametocytes in the lence increased with body size, but blood cells. False negatives were possi- leveled off as lizards reached adult size ble if the infection had not yet begun (Fig. 1). There was no significant differ- to shed gametocytes into the blood. Par- ence in body size for infected and non- asitemia in blood is expressed as para- infected females (Fig. 1 and U tests, P > sites/ 10,000 erythrocytes (RBC). We also 0.05). Because of the leveling off in recorded the percent of immature cells prevalence in larger males, there was (iRBC) among the erythrocytes. These no overall difference in prevalence are easily distinguished when stained based on male body size (U tests; P > with Giemsa by their color and mor- 0.05) phological features (Schall, 1983a). Female C. arubensisare all brown with brown stripes, whereas males, includ- RESULTS ing the largest animals, can be of any Parasitemia and Prevalence. Haemo- of the color classes. However, because gregarine gametocytes are very obvious juvenile males resemble females, I se- in C. arubensis erythrocytes that have lected only males > 100 mm SVL for the been stained with Giemsa. As no hae- following analyses. Differences among mogregarine has ever been described individual lizards in growth rate are from C. arubensis,I describe this species' unknown; by choosing only the largest gametocytes here. It is probably a males I hoped to compare samples of species of Hepatozoon,but should not be infected and noninfected lizards that given a species designation without were of similar age distributions. For the knowledge of the full life cycle (Man- 1984 sample (scored from live animals), well, 1977). Gametocytes are sausage- infected adult male lizards had a sig- shaped, the cytoplasm stains very light- nificantly different color distribution ly purple, and the centrally located than that of noninfected animals (x2 = nucleus stains deeply purple. The host 7.84, P < 0.05, N = 83). Infected animals cell nucleus is displaced to accommo- fell more often into color classes 1 and date the parasite. Mean sizes of 10 ga- 2 (60%), and noninfected ones into

This content downloaded on Thu, 28 Feb 2013 10:35:29 AM All use subject to JSTOR Terms and Conditions ENDOPARASITE OF CHEMIDOPHORUSARUBENSIS 321 classes 3 and 4 (69%). Thus, more col- TABLE1. Numbers of Cnemidophorusarubensis orful males were more likely to be in- infected with a haemogregarineparasite for two October 1980 season on the fected with the haemogregarine, re- sample periods, (wet island of Aruba)and March 1984 season). gardless of their body size. The 1980 (dry sample was scored from 91 preserved Not adult males. Once again, more colorful Infected infected males were more likely to be infected Females 1980 11(18%) 49 (36% of infected males were class 1, and 1984 11 (18%) 49 only 17% of noninfected males were Males 1980 21(36%) 38 color class 1), although the difference 1984 20 (33%) 41 between infected and noninfected males was not significant (X2= 5.08, P = 0.079). Hematological Effects.-Percent imma- (U test, P < 0.05), so comparisons of in- ture erythrocytes (iRBC) was scored for fected and noninfected lizards were four groups: noninfected lizards col- conducted separately for each sex. Both lected in 1984 dry season (x iRBC = infected and noninfected males had rel- 0.70%, SD = 1.03), noninfected animals ative fat mass at 0.8% of body mass, and collected in 1980 wet season (x = 0.97%, both groups of females stored fat equal SD = 1.02), infected lizards with para- to 0.5% of body mass (U tests, P > 0.05). sitemia < 1 /10,000 RBC (x = 0.78%, SD = Similarly, there was no difference be- 1.21), and infected lizards with parasit- tween groups in relative liver mass (for emia >1/10,000 RBC (x = 0.66%, SD = males 2.6% of body mass, for females 0.96). Sample sizes were 30 for each 4.0% of body mass; U tests, P > 0.05). group. All four groups displayed simi- Lastly, mean relative testis weight was lar, low-level percentages of immature larger for noninfected whiptail lizards cells, indicating the parasite does not (0.2% of body mass vs. 0.1%, but the dif- cause measurable host erythrocyte de- ference was also not significant (U test, struction (Kruskal-Wallis test, P > 0.05). P > 0.05). Hemoglobin concentration in whole Physiological and Behavioral Effects.- blood was determined only for the Table 2 reveals that haemogregarine in- March 1984 sample and did not differ fection does not have substantial im- significantly between sexes of C. aruben- pact on an important physiological sis (x for males = 8.4 g/100 ml, N = 58, function, consumption of oxygen by and for females 8.9 g/100 ml, N = 56; tissues, and its behavioral correlate, U test, P > 0.05); thus, data were com- running stamina. However, infected C. bined to compare infected and nonin- arubensisdisplayed significantly higher fected lizards. These two groups did not consumption of oxygen when at rest. differ in content of the hemoglobin DISCUSSION blood (x for both groups = 8.7 g/100 ml, infected N = 36, noninfected N = The effect of parasites on their hosts 114; U test, P > 0.05). Parasitemia and ranges from severely pathogenic, in hemoglobin concentration were not which host fitness is substantially re- correlated (Spearman correlation, P > duced, to a benign association ap- 0.05). Several animals collected in March proaching commensalism. The evolu- 1984 were very thin and slow moving. tionary origin of variation in parasite These animals had low hemoglobin pathogenicity, which occurs even concentrations (~5 to 6 g/100 ml blood), among closely related species of para- but this group contained both lizards sites, is of considerable theoretical in- infected and not infected with the hae- terest (Ewald, 1983). However, a gen- mogregarine. eral explanation for this variation may Organ Weights.--Mean relative fat be elusive. Of more prosaic interest is mass and liver mass differ between sexes the realization that parasites can add an

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35 28

30 MALES

0 LAJ 25 40 H b=i U C) 20 CLA bAJ C) wL 15 FEMALES

10

<76 76-85 86-95 96-105 106-115 SIZECLASS OF LIZARDSIN MM SVL FIG.1. Percentof male and female Cnemidophorusarubensis infected with a haemogregarineparasite by body size class. The figure demonstratessexual dimorphismin which adult males are substantially largerthan females. unexplained source of variation to data Damage to the liver was measured only (Schall, 1983a). The measured effects of in a crude way by simply weighing the Plasmodium on fence lizards demon- organ. Pathology at the histological or strate that the presence of parasites can biochemical level, though, should have seriously compromise results from eco- been evident from the amount of fat tis- logical or physiological studies. sue stored or from a reduction in be- Despite the fact that haemogrega- havioral performance. Although any rines can be severely pathogenic to some destruction of liver tissue is critical for hosts (Maxwell, 1977), the Aruban hae- a vertebrate, such damage would be of mogregarine appears to have little, if primary significance for the Aruban any impact on Cnemidophorusarubensis. whiptail lizard because of its diet. C. The lack of hematological pathology is arubensisis primarily a herbivore and not surprising because the parasite does consumes several kinds of highly toxic not undergo reproduction in the blood plants (Schall, 1986). Vertebrates neu- cells, but only casts relatively few ga- tralize toxic substances in their diets via metocytes into erythrocytes. However, mixed function oxidase systems in the as the Aruban haemogregarine presum- liver (Rhoades, 1979), so disruption of ably undergoes proliferation in the liv- liver function could severely alter the er of the lizard, I expected the parasite whiptail's ability to process toxic plant to have measurable impact on its host. material in its diet.

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TABLE 2. Physiological and behavioral performance of Cnemidophorusarubensis infected and not infected with a haemogregarine parasite. Oxygen consumption when animal was at rest, for two min after 30 sec of maximal activity, and the difference between the two are given as ml O2/g'h. Also presented is the distance run in meters in an oval running track in 30 sec and 2 min when chased. Means are followed by SD and sample size. Not infected Infected U-test

Resting VO2 0.265 (0.067) 6 0.294 (0.077) 6 P < 0.05 Maximal VO2 0.960 (0.243) 74 0.936 (0.233) 14 ns Increment VO2 0.544 (0.136) 6 0.498 (0.133) 6 ns Distance run in 30 sec 24.06 (6.40) 61 23.57 (6.64) 14 ns Distance run in 2 min 46.16 (10.36)61 45.37 (12.42) 14 ns

The presence of haemogregarine ga- tually positively associated in males. metocytes, which are the only infective Brightly colored C. arubensis males ap- stage, in very similar numbers in both pear more aggressive and frequently wet and dry seasons suggests that trans- engage in chases (Schall, unpublished mission takes place year-round. If so, observations). Perhaps these animals are this fact would help in discovering the simply more frequently exposed to at- vector. However, C. arubensisblood cells tack by the biting arthropod that is the might live a long time (autoradiogra- vector of the haemogregarine. Alterna- phy of radioisotope labelled erythro- tively, the more colorful animals might cytes reveals they can live at least 48 simply be older and have had a longer days; Maizels, 1980), so those seen in exposure to the vector. I attempted to one season could simply be aging cells eliminate this possibility by using only cast into the blood some months earlier. the largest males in the analysis. Al- The prevalence distribution among though Hamilton and Zuk have pro- size classes seen in Fig. 1 approximates posed an intriguing hypothesis, proper one that emerges from simple models testing requires a sophisticated under- of the dynamics of parasite infection in standing of the particular parasite-host which the chance of infection per time system. period is constant, there is no mortality -Rene W. Schall the and infection is Acknowledgments. caused by parasite, assisted with the field work. The chance of greatly My life-long (Cohen, 1976). assistants were invaluable: infected with the Aruban laboratory becoming Lord, Steve Lauri must be stable Cynthia Thompson, haemogregarine very Steve Ressel, Ross and because Harvie, Nayduch, over time for C. arubensis para- Terri Gutterson. The research was fund- site was very similar for wet prevalence ed by grants from the American Philo- and dry season samples taken almost the Whitehall Foun- four sophical Society, years apart. dation, and NSF (BSR-8306925). Hamilton and Zuk (1982) propose that LITERATURECITED sexually dimorphic traits remain im- of portant in female choice of mates even BENNETT,A. F. 1980. The thermal dependence after of sexual selection lizard behavior. Anim. Behav. 28:752-762. long periods AND T. T. GLEESON. 1976. me- information about Activity because they provide tabolism in the lizard Sceloporus occidentalis. the ability of males to elude parasitic Zoology 49:65-76. attack. Thus, infected males could ap- BROWN,B. 1984. Hematology: Principles and Procedures. Lea & 405 pear scrofulous, or simply less colorful, Febiger, Philadelphia. when In the Aruban PP. parasitized. whip- CALDER, W. A. 1984. Size, Function, and Life tail lizard, however, infection with hae- History. Harvard Univ. Press, Cambridge. 431 mogregarines and bright colors are ac- PP.

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COHEN,J. E. 1976. Schistosomiasis: a human-host RHOADES,D. F. 1979. The evolution of chemical parasite system. In R. M. May (ed.), Theoretical defense against herbivores. In G. A. Rosenthal Ecology: Principles and Applications. Pp. 237- and D. H. Janzen (eds.), Herbivores, Their In- 256. W. B. Saunders, Philadelphia. teraction with Secondary Plant Metabolites. Pp. EWALD,P. W. 1983. Host-parasite relations, vec- 4-55. Academic Press, New York. tors, and the evolution of disease severity. Ann. SCHALL,J. J. 1977. Thermal ecology of five sym- Rev. Ecol. Syst. 14:456-486. patric species of Cnemidophorus(Sauria: ). FURMAN,D. P. 1966. Hepatozoonbalfouri (Laveran Herpetologica 33:261-272. 1905) sporogonic cycle, pathogenesis, and .1983a. Lizard malaria: Parasite-host transmission by mites to jerboa hosts. J. Par- ecology. In R. B. Huey, E. R. Pianka, and T. W. asitol. 52:373-382. Schoener (eds.), Lizard Ecology: Studies of a HAMILTON,W. D., ANDM. ZUK. 1982. Heritable Model Organism. Pp. 84-100. Harvard Uni- true fitness and bright birds: A role for para- versity Press, Cambridge, Mass. sites? Science 218:384-387. 1983b. Lizard malaria: Cost to vertebrate HOOGSTRAHL,H. 1961. The life cycle and inci- host's reproductive success. Parasitology 87: dence of Hepatozoonbalfouri (Laveran 1905) in 1-6. Egyptian jerboas (Jaculus spp.) and mites. J. . 1986. Toxic plant compounds and the Protozool. 8:231-248. diet of the herbivorous whiptail lizard, Cne- MAIZELS,C. S. 1980. The cell kinetics of the pe- midophorusarubensis. In J. Wright (ed.), Biology ripheral blood of the Aruban whiptail lizard, of Cnemidophorus.Los Angeles Co. Mus. Nat. Cnemidophorusarubensis. MS thesis, Immaculate Hist. In press. Heart College, Los Angeles. 58 pp. , A. F. BENNETT,AND R. W. PUTNAM.1982. MANWELL,R. D. 1977. Gregarines and haemo- Lizards infected with malaria: Physiological gregarines. In J. P. Kreier (ed.), Parasitic Pro- and behavioral consequences. Science 217: tozoa III. Pp. 1-32. Academic Press, New York. 1057-1059. MILLER,W. W. 1908. Hepatozoonperniciosum (n.g., TELFORD,S. R. 1970. A comparative study of en- n. sp.) a haemogregarine pathogenic for white doparasitism among some southern California rats; with a description of the sexual cycle in lizard populations. Amer. Midi. Natur. 83:516- the intermediate host, a mite (Laelaps echidni- 554. nus). Bull. Hyg. Lab., Treas. Dept., Washington 46. Accepted: 18 October 1985.

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