DECEMBER1991 DEVELOPMENT INO SUNVTVIT- OF EGYPTIAN ANOPHELINES 551

DEVELOPMENT AND SURVIVAL OF ANOPHELES PHAROENSIS AND AN. MULTICOLORFROM ,

MOHAMED A. KENAWY

Researchand Training Center on Vectorsof Diseases,Ain Shnms lJniuersity, Abbossia,, A.R. Egypt

ABSTRACT. Adults ofAnophzbspharoensis andAn. multicolnrwere heldunder cycling environmental conditions in the laboratory'to eiamine the duration of the gonotrophic cycles, survival and lifl expectancy,and to examineihe life table characteristics of Fr larvae. The first gonotrophic cycle took 6.i4 and Z.5Zdays for An. phnroensisandAn. multicolor, respectively.Subsequent gonotrophic.cycles for the 2 specieswire shorter'.Daily survival rates of An. pharoensis and-An. multicolor in the laboratory were 0.'9Sand 0.93, respectively.The parity rate of field-collectedfemales and estimatesof the duration of the gonotrophic'cycleyielded daily survivorship estimatesof 0.89 and 0.80 fot An. phnroensisand An. i"iii"]tor, resiectivlly. [4ean life eipectancy at-emergencewas 19.0 day_sfor An. phnroensiscompared with 1?.9 days for Ai. multicolor. Survivorship from egg eclosionto adult emergenceand developme.nt time were similar for both species.Both the duration of gonotrophic cycles and mean life expectarcies indicated that A n. pharoensishad a greater potential to serveas a malaria vector than An mriti'colnr.

INTRODUCTION mine parity based on the coiling of ovarian tracheoles (Detinova 1962). In Cairo, observa- Anophclcs pharoensis Theobald, An' multi' tions were made on fed mosquitoes and the colar Cambouliu and An. sergentii (Theobald) resultant F, progeny in a room with naturally are common mosquito speciesin Faiyum Gov- cycling conditions of temperature (mean--= ernorate, Egypt, an agricultural oasis where i5.7",-rurrg" : 17.6-33.8'C), relative humidity Plasmodium uiuox and P. falciparum are en- (mean = 77.6%, range = 60-957o) and illumi- demic. Anophelespharoensis and An. sergentii nation to simulate the field conditions. For com- are proven malaria vectors, but An. multicol'or parison, development of immature stagesfrom has never been found infected in nature (Barber eclosion to adult emergencealso was studied in and Rice 1973, Halawani and Shawarby 1957, an insectary maintained at constant conditions El Said et al. 1983, 1986).Anophel.es multicolor of 25 + 2"C temperature, 70 + 5% RH anc has long been considereda suspectedvector due illuminated by fluorescent lighting for ca. 8 h to its relative abundance and susceptibility to daily. (El infection under experimental conditions Gonotrophiccycle, femnle suruiuorship and life Said and Farid 1982).In Egypt, life table studies expectancy:Blood-fed femalesof An. phnroensis have only examined the survivorship and repro- h-- 42\ andAn. multicolnr (n: 66) were placed ductive potential of An. sergentii under labora- individually in 60 ml screenedplastic vials lined tory conditions (Beier et al. 1987a). with frlter paper and containing 10 ml fistilled The present study compared the duration of water for oviposition. The length of the gono' the gonotrophic cycle,daily suwivorship and life trophic cycle (g) was determined as the time expectancyof field-collectndAn. pharoerxis and from blood feeding (in the freld) to oviposition. An. rnulticolnr adult femalesthat were held un- After oviposition, females were provided with der insectary conditions simulating field condi- LTVosugar solution on cotton (changed daily) tions. Both larval and adult life table parameters and observeddaily for mortality. Dead females were determined for these 2 mosquito speciesto were dissected and ovarian dilatations were explain why An. rnultirolor apparently is not a counted to determine the number of the gono- malaria vector in Egypt. trophic cyclescompleted (Detinova 1962).Based on the number and duration of the respective plus maturity period MATERIALS AND METHODS gonotrophic cycles a 2 day prior to the first blood meal, the calendar ageof Adult collectionand, processing: Adult females each female at the time of collection was deter- of An. pharoensls and An. multicobr were col- mined. Age-specific suwivorship (S) and life lected during October and November 1990 in expectancy at emergence (er) in days for each Tersa, a malaria-endemic village in parous gtoup and the mean for all femaleswere District, Faiyum Governorate,Egypt. Mosquito calculated according to methods described by were collected every 2 h throughout the night Walter and Hacker (1974)and Reisenand Mah- using a donkey-baitcd trap. A sample of the mood (1980). For comparison,the survivorship mosquitoeswere dissectedimmediately to deter- under field conditions, as expressedby the daily

L JouRuer,or rnr AunRrceN Mosqurro CoNTRoLAssocrerron Vor,.7, No. 4

Table 1. Duration of gonotrophic cycles of field-collected blood-fed females of Anopheles pharoensis and An. multicolor.*

An. pharoensis An. muLticolor No. ovi- Mean du- No. ovi- Mean du- Gonotrophic posited ration posited ration cycle females days + SE females days + SE lst (1-parous) 27 6.14-f 0.14 54 7.37+ 0.62 2nd (2-parous) 18 5.50+ 0.56 12 5.50+ 0.50 3rd (3-parous) 3 4.00+ 0.00 0 Total 42 5.71** 66 7.03** * Kept at meancycling temperature of 25.7'Cand RH of 77.6%. ** Weighted mean for all females.

daily on the water surface.Pupae were removed daily from rearing pans and placed in 400 ml screenedemergence cups, kept separatedby pan : and date. Emerged adults were counted and = sexed.Immature developmentalattributes were B calculatedaccordingtoReisen et al. (1982).Sur- vivorship (S) from egg eclosion to pupation, pupation to adult emergenceand total S from eclosion to emergencewere estimated by the I expressions P/1, A/P and A/I, respectively, where P : no. of pupae, A : no. of emerged adultsand I: no. of lst instar larvaeoriginally counted in the rearing pans. Median times to pupation (Pso)and adult emergencefor each sex Fig. 1. Age-specific survivorship of females per day (Eso)were calculated by regression (I1) plotted as a function of age (X) in days for as for Hso. Anopheles pharoensis (n: 42) and An. multirolnr (n = 66). RESULTS probability of survival (P), was calculated for Gonotrophiccycle, female suruiuorshipand life the field-collected females (Davidson 1954) by expectancy:The mean duration of the 1st gono- the expression P = *rfi where p : proportion trophic cycle was 6.14 days for An. pharoensis parous and g : the mean duration of the gono- and 7.37days for An. rnulticolor(Table 1). Sub- trophic cycle. sequent cycles for both species were shorter. Egg hntch rates and duratinn: Eggs from in- Dissections immediately after death indicated dividual femaleswere counted and placed in 200 that 7.1% (3/42) ot An. pharoensisfemales had ml paper cups lined with filter paper and con- 3 dilations (3rd gonotrophic cycle), but none of taining distilled water. Hatched 1st instar larvae the 66 An. multicolnr females had more than 2 were removed and counted daily. Egg hatch rates dilations. and duration in days were determined under The mean survivorship rates (S) were 0.95 + cycling and constant temperatures.Median time 0.01 per day for An. pharoensis(0.95 for l-p and until hatching (Hro) was calculated by fitting a 0.96 for 2-p females) and 0.93 + 0.002 per day regressionofthe form P: a * b ln X (where for An. multicolor(0.93 for 1-p and 2-p females). P : cumulative proportion hatching on eachday The age-specificsurvivorship curves for the 2 (X) transformed to probits) and solving the speciesare shown in Fig. 1. The mean life ex- equationforP = 507o. pectancy (er) at emergencewas 19.04 + 3.26 Irnrnature deuelnprnent:Ten and 15 cohorts of days for Ai. pharoensrs(15.78 and 22.30 days 100 first instar Iarvae ofAn. pharoensis and,An. for 1-p and 2-p females,respectively) and 17.90 rnulticolnr, respectively, were reared under cy- + 2.10 days for An. multicolor (15.80and 20.0 cling temperatures (mean : 25.7"C) in 30 cm days for 1-p and 2-p females,respectively). The diam round enamelpans containing 2 liters mud proportion parous (P) determined by dissection slurry solution (Beier et al. 1987a).Five cohorts of field collected femaleswas 0.50 for An. phar- (100 larvae each) ofeach specieswere reared at oensis (n : 106) and 0.20 fot An. multicolar constant temperature (25 + 2"C). Larvae were (n: 150).Based on these and gonotrophic cycle fed powdered Tetramin@ frsh food sprinkled of 5.7 days for An. pharoensisand 7.03 days for DEcEMBER 1991 DnvuoprvrnNr eNo SuRvIvel or Ecvprret ANopHsI-lNns

An. multicolnr (weightedmeans for all females), respectively)was similar (t : 0.96, d.f. : 23, the daily probability of survival (P) was 0.89 P > 0.05). Median emergencetime (En,,)for and 0.80for the 2 species,respectively. males was significantly shorter for An. multi' Egg hatch rates and duration: Under cycling color (18.5days) than for An. pharoensis(21.0 temperature with a mean of 25.7"C, egg hatch days)(t :2.82, d.f. : 23,P < 0.01).Likewise, rates of 79.8% and 85.07owere obtained over a En,,for femaleswas shorter for An. multicolor meanperiod of 4.02and 3.32days for An. phar- (19.5days) than for An. pharoensis(22.0 days) oensisandAn. multicolnr, respectively(Table 2). (t :2.69, d.f.: 23,P < 0.05).Sex ratios of both The median time for 50% hatching (Hso) was speciesdid not differ significantly(x' : 0.32for similar (t = 1.47,d.f. : 35, P > 0.05) for An. An. pharoenslsand 1' : 0.00for An. multicolor, multicolor (2.7 days) and An. phnroensis(3.1 d.f. : 1, P > 0.05)from the expected1:1 ratio. days). At 25"C constant temperature, eggs of Under constant temperaturc the 2 specieshad An. multicolor hatched in shorter periods than similarsurvivorship A/I rates(t:0.25, d.f.: 8, at the mean cycling temperature. P > 0.05)and Eso(9-d) periods (t : 0.11,d.f. : Immature deuelnpment:Seven developmental 8, P > 0.05 for femalesand , : 0.01,d.f. : 8, attributes were examined for immatures of An. P > 0.05 for males). The 2 speciesalso had pharoensis and An. multicolar, reared under the similar Eso (9-d) times and survivorship A/l cycling room temperature (Table 3). Survivor- ratesat constantand cyclingtemperatures. ship rates from eclosionto adult emergence(A/ : : I) weresimilar (t L.27,d.f. 23,P > 0.05)for DISCUSSION An. pharoensrs(0.13) andAn. multicolor(0.22). Developmental time to pupation (Pso)was sig- Daily survivorshiprates for field-collectedfe- nificantly faster (t : 5.56,d.f. : 23, P < 0.01) malesof An. pharoensisandAn. multicolnr based fot An. multirolnr (16.5 days) thanfor An. phar- on parity rates averaged0.89 and 0.80for the 2 oensis(20.0 days),but survivorship to the pupal species,respectively. The age-specificsurvivor- stage (P/I = 0.14 and 0.24 for the 2 species, ship rates of 0.95 and 0.93 determined for An.

Table 2. Egg hatching rates and duration for Anophelespharoensis andAn. multicoLorat cycling (mean : 25.7'C) and constant (25 + 2"C) temperatures. Species/tem- No. eggs % Hatch Hatch days Hso (days)* perature n (Mean + SE) (Mean -r SE) (Mean + SE) (Mean + SE) An. pharoercis Cycling 15 209.2+ 36.8 74.8a 5.49A 4.07+ 0.50A 3.10+ 0.31A Constant 10 73.3a 16.9 86.0+ 2.55A 3.50+ 0.08A 2.73+ 0.05A An. multicolnr Cycling 22 164.8+ 61.5 85.0+ 3.6 A 3.32+ 0.22A 2.70+ 0.10A Constant 10 75.0+ 15.8 88.6+ 2.4A 2.33+ 0.27B 1.41+ 0.28A + Hso: median time to 50% hatch. ** Means with sameletters in each column are not sigrrificantly different (t : test), P > 0.05.

Table 3. Immature developmentattributes of Anophelespharoensis and An. multicolor reared at cycling (mean : 25.7'C\ and constant (25 + 2"C) temperatures.

Cycling tempetature++ Constant temperature** An. phnroensis An. multicohr An. pharoensis An. multicolor Attributes* (Mean + SE) (Mean + SE) (Mean + SE) (Mean + SE) Survivorship (P/I) 0.14+ 0.03A 0.24+ 0.06A Pso(days) 20.00+ 0.60A 16.50+ 0.30B Survivorship (A/P) 0.83+ 0.06A 0.85+ 0.04A Ero oo 21.00+ 0.93AC 18.50+ 0.34BC 18.40+ 2.32C 18.38+ 2.18C aa 22.00+ 0.85AC 19.50+ 0.47BC t9.53+ 2.32C 19.01+ 2.63C Total survivorship (A/I) 0.13+ 0.04A 0.22+ 0.05A 0.16+ 0.07A 0.18+ 0.04A Sex ratio (99/total)*** 0.45+ 0.04NS 0.51+ 0.04NS *Abbreviations:I: lst instar larvae;P: pupae;A: adults;Pso: mediantime to 50% pupation;E5o: median time to 50% adult emergence. ** Means with the sameletters in each row are not significantly different (t-test), P > 0.05). *** Sex ratios tested for departure from 1:1 by x'; NS : not signifrcant (P > 0.05). JouRrlt, oF THE AMERIcAN MosQuIto CorqrRol AssocleuoN Vol. 7, No. 4 pharoensis and An. rnulticolnr females, respec- survival is a major factor which may limit the tively, under the experimental conditions were capability of An. rnulticolor to transmit malaria. similar to rates ranging from 0.92 to 0.95 re- Theseresults likely explain why An. multicolor ported for An. sergentii femalesheld at 27'C has never been found naturally infected (Ken- (Beieret al. 1987a).These rates for survivorship awy 1988).Studies on the longevity of these 2 under field and cycling conditions indicate that speciesin the field are neededto verify the above moreA n. pharoensis than A n. multicolor females hypothesis. would survive to becomeinfective for malaria. To transmit Plasrnodium uiuax and P. fabi- ACKNOWLEDGMENTS parum, the anopheline female must survive for ca. 9 and 11 days, respectively (at 25.7"C\, after The author is grateful to M. Soualem (Ain taking an infective blood meal (Macdonald Shams Center) for his assistance in the field 1957). Assuming that females take the first collections and laboratory experiments,to S. El blood meal 2 days after emergence,then the Said (Ain Shams Center), A. Merdan (Ain potentially infective femaleswill not be lessthan Shams Center) and R. Gwadz (NIH) for their 11-13 days of age required for P. uiuax and,P. support in facilitating this research, and to J. falciparum transmission, respectively. Under Beier (The Johns Hopkins University) for com- field conditions, the proportion of female popu- ments on the manuscript. This study was supported by the Regional Iations surviving to infective age for P. uiuax "Epidemiology and P. fabiparunz transmission would be 31.4% Project entitled: and Control of and25.4% for An. pharoensisand8.6Vo and5.5% Arthropod-Borne Diseases in Egypt-Nol AI f.orAn. multirolor, respectively.Life expectancy 22667"betvteen the Researchand Training Cen- at 11 and 13 daysaveraged 10.89 and 9.80 days ter on Vectorsof Diseases,Ain ShamsUniver- f.orAn. pharoensisand 6.02 and 5.21 days for sity, Abbassia, Cairo, Eglpt and, the National An. multicolor, respectively.Based on gono- Institutes of Health (NIH), National Institute trophic cyclesof5.3 daysforAn. pharoensisand of Allergy and InfectiousDiseases (NIAID), Be- of 5.5 days for An. multicolor (weighted average thesda,MD, USA. for all females from the 2nd cycle), it appears that mosquito femaleswill take only 2 and one REFERENCES CITED additional blood meals,for the 2 species,respec- Barber,M. A. andJ. B. Rice.1973. A surveyof malaria tively, after completing the sporogonic cycle if in Egypt.Am. J. Trop.Med. Hyg. 17:413-436. Plnsmodium infection was acquired during the Beier,M. S.,J. C.Beier, A. A. Merdan,B. M. El Sawaf first blood meal. In comparison, An. sergentii and M. Abdel Kadder.1987a. Laboratory rearing has the potential to imbibe up to 4 blood meals techniquesand adult life table parametersfor afbercompleting sporogony (Beier et al. 1987a). Anophelessergentii from Eg5rpt.J. Am. Mosq.Con- The developmental rates of immature An. trol Assoc.3:266-270. A. Kenawy, El multicolnr under cycling temperature based on Beier,J. C., J. H. Zimmerman,M. S. Said and M. M. Abbassy.1987b. Host feeding pat- Psoand 856values were significantly higher than terns of the mosquito community (Diptera: Culici- those of An. ph,aroensis,but survivorship of the dae) in two Faiyum Governorate villages. J. Med. different stages was similar for the 2 species. Entomol. 24:28-34. Adults of both speciesemerged at shorter pe- Davidson, G. 1954. Estimates of survival rate of an- riods (Eso9-d) under constant than under cy- opheline mosquitoesin nature. Nature 174:792-793. cling temperature, but their survivorship rates Detinova, T. S. 1962.Age groupingmethods in Diptera (A/I) were similar under both temperatures. of medical importance. World Health Organization, results were obtained by Reisen et al. Geneva. Similar H. Farid. 1982. Experirnental trans- (1982) El Said, S. and for An. culicifacbs. Under both the con- mission of Plosmodiutn uiuax by Anophcles multi- stant and cycling temperatures,An. rnulticolnr color under laboratory conditions and the effect of immatures developed at higher rates and in temperature on the sporogoniccycle. J. Egypt. Pub- shorter periods than An. ph.aroensis.Similarly, lic Health Assoc.5?:512-540. An. multicolar hatched more eggs and in less El Said, S., B. EI Sawaf,M. Gebril, M. A. Kenawy and time than An. pharoensiseggs. Such higher egg A. Azzab.1983.Bionomics of anophelinemosquitoes hatching rates together with the observedfaster in the Faiyum Governorate, Egypt, in relation to and control of malaria. J. development of An. multicolor may explain the malaria transmission Egypt. Public Health Assoc.58:189-241. abundanceof its immature stagesin the field. El Said, S., J. C. Beier, M. A. Kenawy, Z. S. Morsy In Egypt An. pharoensrsand An. multicobr and A. I. Merdan. 1986.Atnpheles population dy- are zoophilic (Beier et al. 1987b,Kenawy et al. namics in two malaria endemic villages in Faiyum 1987). Although immature stagesof An. multi- Governorate, Egypt. J. Am. Mosq. Control Assoc. color develop faster than An. pharoerwls, adult 2:158-163. DECEMBER1991 DEVELoPMENT eNo SuRvIveL on EcYprIlrq ANoPHELINES 555

Halawani,A. and A. A. Shawarby.1957. Malaria in Reisen,W. K. and F. Mahmood.1980. Horizontal life Eg1pt.J. Egypt. Med. Assoc.40:753-792. table characteristics of the malaria vectorsAnoph- Kenawy,M. A. 1988.Anopheline mosquitoes (Diptera: elesculicifacies and An. stephensi(Diptera: Culici- "His- Culicidae)as malaria carriersin A.R. Eglpt: dae).J. Med. Entomol. 17:211-217. tory and present status." J. Eg,"t. Public Health. Reisen,W. K., K. Azra and F. Mahmood. 1982.Arnph- Assoc.63:67-85. el.esculicifacies (Diptera: Culicidae): horizontal and Kenawy,M. A., J. C. Beier, J. H. Zimmerman,S. El vertical estimates of immature development and Said and M. M. Abbassy. 1987. Host feeding pat- survivorship in rural Punjab Province, Pakistan. J. terns of the mosquito community (Diptera: Culici- Med. Entomol. 19:413-422. dae) in Governorate, Eg1pt. J. Med. Ento- Walter, N. M. and C. S. Hacker. 1974.Variation in mol. 24:35-39. Iife table characteristics among three geographic Macdonald, G. 1957.The epidemiologyand control of strains of Culex pipiens quinqucfasciatw. J. Med. malaria.Oxford Univ. Press,London. Entomol.11:541-550.