Tox!con, 1964, Vol . 2. pp. 201-203 .

Per~amon Preaa Ltd . Painted in Greet Hntam

COMPARATIVE LETHALITY OF SEVERAL LATRODECTUSVENOMS

J. D. McCitorre

Florida Presbyterian College, St. Petersburg, Florida, U.S.A.

Abetrad-Four apociea of the blacdc-widow spider genus Latradectns are known to occur inNorth America. They are L . rn~actans ~etans, L. geometrieus, L. vnrtolus and L. blsleopf.The oomparafive lethality of the venons of these species and of the European sub-speciesL. rractana trcdeclmguttatus was evaluated. All have very potent venoma although there arespecies differentxa in venom lethality and the average amount of venom obtained.

INTRODUCTIONIx ><-ns revision of the black-widow genus Latrodectus, Lsvt [1] recognized three NorthAmerican species L. mactans mactans (Fabricius, 1775), L. geometricus C. L. Koch, 1841,and L. curacaviensis (Muller, 177 . Subsequent field work, laboratory studies, and theacquisition of additional specimens have revealed that the North American specimensconsidered to be L. curacaviensis actually belong to two species, L. variohts Walckenaer,1837 and L. bishopi Koston, 1938 [2].

This paper presents the results of a study of the comparative lethality of the venomsof each of the four North American species and of the European subspecies L. mactanstredecimguttatus .

MATERIALS AND METHODSThe venoms were prepared by dissecting out the venom glands from groups of 20-30

mature female spiders and homogenizing them in distilled water with a Servall micro-homogenizer. . The homogenate was then centrifuged at 7200 rev/min for 20 min. Theglands and homogenate were kept cold during these operations. The clear, viscous super-natant obtained by centrifugation was then lyophilized in a serum bottle with a Virtisdry ice freeze-dryer. This lyophilized material, henceforth referred to as venom, wasweighed and then was stored in a dessicator kept at -1 ~5° in a deep freeze .

Kt~Ax et al. [3] have reported that there is seasonal variation in the lethality of L.mactans mactans venom. In order to eliminate this variable, all of the venoms used werecollected during the Summer of 1963 . Also, all of the spiders used, with the exceptionof the L. macrons tredecimguttatus which were obtained from Israel, came from the samegeographical area, the state of Florida.

The method of Lrrcl~.n and WILCOXON [4] was used to determine the LDao of eachvenom in mice. Groups of six 20-30 g white mice of a single strain obtained from acommercial source were injected intraperitoneally with varying doses of venom dissolvedin a constant volume (0~2 mI) of physiological saline . Death or survival at the end of48 hr was considered the endpoint . In this study 48 hr was used for the following reason.The ütijected mice passed through two fairly distinct crises. The fast occurnd within

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J.D. McCRONE

6-8 hr after injection, the other 188 hr after injection. Autopsy of the animals thatdied within 6-8 hr revealed no gross pathological changes, although the lungs were paleand inüated. Those animals which died later, however, showed marked gross pathologicalchanges. The lungs had a reddish marbled appearance with numerous petechiae and therewas often extensive hemorrhaging in the abdominal cavity . If an animal survived thesetwo crises and lived for 48 hr it would eventually recover in most cases .

RESULTSThe average amount of venom obtained per spider for each species and the LD6o for

each venom are given in Table l . The average amount obtained per spider was calculated

TAaLE 1. AVaIeAa$ AlSOUNT OF VBNOM OH'rAINBD AND LETHALITY DATA FOR SEVERAL La1rOdLCINS SP8CIES .

by dividing the total amount ofvenom extracted from each species by the number of spidersused of that species. Since the effectiveness of a venom is a function of both the amountof venom obtained and the venom lethality, a lethality factor similar to the toxicity factorused by WfnzTEMOxs and IRAN [5] was calculated for each species (Table 1) . Thisvalue represents the number of LD6o per average amount of venom obtained .

DISCUSSIONThe presence of gland material in the venom gland extract probably results in a very

conservative estimate of the actual lethality of the venoms studied ; however, the LD 6ovalues reported here do give a fairly accurate estimation of the relative lethality of thevenoms .

It is difficult and probably meaningless to compare my lethality values with thosepreviously published by other workers because of the marked differences in experimentalconditions. An exception is the LD6o value given by BEITINI and Tosctll-1ÏtONTALI [6] forthe L. mactans trea!ecimguttattts found in Italy . Using slightly different methods, theyobtained an LD6o value for mice of 0 ~9 mg per kg while I obtained a value of 0"59 mg

SpeciesNo . ofspidersused

Avera®e Amount ofvenom obtained

(mg/spider)

Mouse LD,O in mg/kg(95 ~Confidence

interval)

Lethality factor(LD,o s/avera®eamount of venom

obtained)

L. mactans t~tatus 30 0238 0~59(0~33-1 ~06) 0~404

L. gonmetricus 255 00970 043(031-0~59) 0226

L. tiarblus 74 0254 1 ~80(120-2 ~70) 0l41

L. maetans mactans 49 0l90 1 ~30(120-2 ~70) 0106

L. bfshopi 70 0l57 220(129-3~74) 0~071

Comparative Lethality of Severnl latrodectus Venons

203

per kg . The small difference may be due to one or more .of the following factors. First,the spiders canoe from different geographical areas. Secoàd, the difference could just bethe result of experimental error since their value falls within my 95 per cent confidenceinterval. Third, they used a shorter assay period which would tend to raise their value.

The most surprising result of this study is the finding that the brown widowL. geometricus has one of the most lethal of the Latrodectus venous. It has never beenconsidered a particularly dangerous species although there have been reports of peoplebeing bitten with fairly severe results [7, 8j . Two factors probably account for the factthat more cases have not been reported . One is that the average amount ofvenom obtainedper spider is very low, the other is that L. geometricus is much less aggmssive and irritablethan any of the other species studied .

SUMMARY(1). The average amount of venom obtained per spider, the LDso vahu itt mice of

the venom, and a lethality factor was determined for Latrodectus mactats macrons, L.macrons tredecimguttatus, L. variolus, L. bishopi and L. geometricus using lyophilizedvenom gland extract.

(2). All have very potent venons, but there are species differences in the three attributesthat were measured .

Ackrrowledgmuus-I wish to thank Mr. M. L. NsrztoFt+ for txhnical aid. Dr. H.W. Lsvl ofthe Museumof Comparative Zoology, Harvard University and Dr. A. Ssvtov of the Hebrew University, Jerusalemkindly helped me obtain ogg sacs of L mactau tredecirnquttatw. This study was supported by PublicHealth Service Cirant C3M 11206-01 from the National Institute of (leaeral Medical 3cd~oes.

RBFBRENCBS[1]

Lsvr, H. W., The spider genus Latrodectur (Amusas, Theridüdae) . 7Yars. Amer. nier. Soc., T1, 7,1959.[2]

McCx~oxs, J. D. and LBVr, H.W., North American widowepideas oftheLatrodatrv cmwcavlensis group(Araneae : Theridüdae). Psyche (in press).

[3]

IC~aex, H. L., W

ei and H>m~v, RA., Seasonal variation in venom ofblack widow spiders.Amer.1. Tlrop. Med. Hyg., 10, 477, 1960.

[4] Lrrc~~n, J. T. and Wu eoxox, F., A simplified method of evaluating dosaeffect experiments.1. Pharnmcol., 96, 99, 1949.

[S] Wi~rr>~oaB, F. W. and IC~a.~x, H. L., Medtaaify Emportant scorpions fie tira Pacffrc Aras in Yerromoarand Poisonous Animais and Noxious Piaule of the Pacf/rc Region, H. L. IC~~ sud W. V.MxcF~eur~, Eds. New York : Macneillan, p. 107, 1963 .

[6] lisrzau, S. and Taecm-Fnoxrus,N., Sioch

l and Toxicological aspects ofIatrodectw tredecinrguttatus venom. XI. Iru. Songr. F. Ertom. Wetn Werh. B., 3, 1960.

[7]

Bra, W. 7., The black widow and five other venomous spiders in the United States . Ark. Agr. exp.Sta. Bui., 608, 1959 .

[8l

MtePx~esox, J. W. E., A poisonous spider. 1. mad. Assoc. S. ~., 3, 691, 1929 .