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1 Acarologia A quarterly journal of acarology, since 1959 Publishing on all aspects of the Acari All information: acarologia@supagro.inra.fr Acarologia is proudly non-profit, ith no page charges and free open access Please help us maintain this system by encouraging your institutes to subscribe to the print version of the journal and by sending us your high quality research on the Acari. Subscriptions: Year 218 (Volume 58): 38 Previous volumes (21-216): 25 year (4 issues) Acarologia, CBGP, CS 316, MONTFERRIER-sur-LEZ Cedex, France The digitalization of Acarologia papers prior to 2 as supported by Agropolis Fondation under the reference ID through the «Investissements d avenir» programme (Labex Agro: ANR-1-LABX-1-1) Acarologia is under free license and distributed under the terms of the Creative Commons-BY-NC-ND hich permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original author and source are credited.

2 OVIPOSITION OF BOOPHILUS MICROPLUS (CANESTRINI) (ACARIDA : IXODIDAE) I. INFLUENCE OF TICK SIZE ON EGG PRODUCTION BY GORDON F. BENNETT 1 RÉSUMÉ La production d'œufs par les femelles de Boophilits microplus (Canestrini) de tailles différentes est linéaire. Les petites femelles ont une production inférieure à celles dont le poids est optimal (de 16 à 3 mg.) La durée de la période d'oviposition varie avec la température et présente un pic au début du cycle. Les œufs pondus au début et à la fin de la période d'oviposition (représentant IO % du total) sont plus longs à éclore et ne sont pas aussi viables que les autres. La longueur et la largeur des œufs ne varie pas sensiblement au cours de la période de ponte, mais leur poids diminue vers la fin du cycle. ABSTRACT Egg production by Boophilus microplus (Canestrini) of different sizes has been shon to be linear ; small ticks ere found to be Jess efficient in producing eggs than ticks in the optimal eight range of 16 to 3 mg. The duration of the oviposition period varied ith temperature, the peak occurring early in the cycle. Eggs laid at the beginning and end of oviposition (representing IO % of the total) required a longer period until eclosion and ere not as viable as eggs laid during the peak. Length and breadth of the eggs did not vary markedly throughout oviposition but the eight decreased toards the end of the cycle. INTRODUCTION The free-living portion of the life cycle of the cattle tick, Boopliilus microplits, is acted upon by anumber of unavoidable climatic factors. The effect of some of these factors has been reported by a number of orkers (LEGG, 193; WILKINSON and WILSON, 1959; HARLEY, 1966; lviccul LOCH and LEWIS, 1968) and summarized by WILKINSON (197). With the exception of HITCHcocK's (1955) and K1TAOKA and Y AJIMA's (1958) publications, fe detailed studies have been made of the oviposition of B. microplits under controlled laboratory conditions. Such studies provide basic information essential to the interpretation of field experiments. It is generally conceded that large B. microplits lay more eggs than do small individuals. KITAOKA and YAJIMA (1958), orking ith B. caudatus (=B. microplits), demonstrated a linear relationship beteen the eight of the engorged female and the number of eggs laid. Hoever, r. Department of Biology, Memorial University of Nefounclland, St. John's, Nefoundland, Canada. Acarologia, t. XVI, fasc. r, 1974.

3 -53 - since the J apanese and Queensland populations of B. niicroplits are undoubtedly genetically isolated, Kitaoka and Yajima's ork as repeated, using Queensland material. On the basis of the studies of HITCHCOCK (r955) and KITAOKA and YAJIMA (r958), it could be concluded that all ticks, regardless of size, folloed a similar pattern of both pattern and efficiency of oviposition hen held at the same temperature. Hoever, preliminary observations suggested that small ticks folloed a different pattern and this aspect as further investigated. In addition, data on the dimensions, eight, prehatch period and viability of the eggs laid on each day of the oviposition cycle are presented. HITCHCOCK (r955) indicated to peaks of egglaying and Tatchell (pers. comm.) concurred. These studies, using groups rather than individual ticks, did not support these findings, and the matter as studied in greater depth. iviaterials AND lviethods Ticks of the acaracide-susceptible Yeerongpilly reference strain (Y strain) ere used throughout as the basis of this study. The ticks ere obtained each morning from a variety of susceptible and resistant British and Zebu breeds of cattle. The majority of the ticks engorged and dropped from the host in the early hours of the morning (WHARTON and UTECH, r968), probably 6-8 hours before use in an experiment. All ticks ere used individually or in groups of 5 or more and ere selected from ticks in the eight range of r75-25 mg. Specific techniques are cited, here appropriate, in text. A. General Pattern of Oviposition (i) Pattern at 85op, RESULTS AND DISCUSSION In this study, essentially the same approach as that used by KITAOKA and YAJIMA (r958) as employed, but the eight of eggs, rather than the number, as the basis of comparison. The eight of eggs laid per day as expressed as the accumulated percentage of the total eight of eggs produced. In this study, three groups of 5 ticks ere held at 85 F. and as the results for the three groups ere closely similar, the data as pooled and the curves (Fig. r) obtained. From this oviposition curve it can be seen that the majority of eggs are laid during the early portion of the cycle, peak egg-laying occurring on the fourth and fifth day folloing engorgement. The accumulated percentage curve shos that 5 % of the eggs ere laid by day 5 and 95 % by day ro ; oviposition as completed by day r6. The results of HITCHCOCK (r955) indicated that some ticks have to peaks of egg-laying; Tatchell (pers. comm.) concurs. K1TAOKA and YAJIMA (r958) indicate to peaks of oxygen consumption and Cherry (pers. comm.) found to periods of increased ax deposition on the cuticle of ovipositing ticks. In the face of this evidence, the results (Fig. r) appear anomalous. Possibly, by using groups of 5 or more ticks, the performance of the individual as masked. This possibility as further studied by eighing the eggs laid each day by 57 individual ticks, held at 8o F., the same temperature that HITCHCOCK (r955) reported to peaks of oviposition. The results of this study (Table I) indicated that only ro individuals (r8 %) of the group shoed to or more peaks of oviposition. The other individuals laid eggs in a pattern similar to that illustrated (Fig. r). On the basis of these results there is no indication that a to-peak oviposition cycle is of normal occurrence for B. microplus, but it can happen in some individuals.

4 -54 - ~ 2 u :: 1 o z u :: 4 o DAYS FrG. r. - Oviposition and accumulatecl percentage oviposition curves for 15 ticks held at 85 F. in darkness. TABLE I. - Number of peaks of oviposition by ticks of various eights maintained at 8o F. No. of Peaks Shon r Peak z Peaks 3 Peaks Number 47 9 % of total 82 % 16 % Av. day of peak(s) ,9 I 2% 5, 8, IO

5 (.f) z <i ::: l9 ::: u 2: 5 WEIGHT LENGTH y (.f) z ::: u WIDTH --- ' '.,; ' DAYS 15 2 FIG 'Veight, length and idth of eggs during oviposition cycle.

6 - 56 (ii) Size and eight of eggs throitghoitt oviposition. KITAOKA and YAJIMA (1958) indicated that the average eight of the egg increases slightly as oviposition proceeds but gave no indication of any changes in length or breadth although illustrating changes in length, breadth and eight of eggs of Haemophysalis ias. These studies ere repeated on the Queensland strain of B. mùroplits (Fig. 2), held at both constant and diel temperatures of 75 F. (diel temperature = 12 hours at 67.5 F., 12 hours at 82.5 F. to average 75F.) and a relative humidity of 8-85 % The data (based on individual measurements of 6 eggs per day) ere pooled and the mean range illustrated (Fig. 2). The eight of the eggs laid throughout the course of the oviposition cycle ere studied on ticks maintained at a constant 8 ± lof. and at a relative humidity of 8-85 % The results (Fig. 2) indicated that there as little change in the mean length (484 microns) or idth (356 microns) of the eggs throughout the oviposition cycle. The range, hoever, did tend to increase toards the end of th~ cycle. A mean eight of 45 micrograms per egg as also relatively constant during the first half of the cycle but egg eight decreases as egg-laying termina tes. (iii) Prehatch period and viability of eggs laid throitghoitt cycle. Samples of the eggs produced each day by ticks under constant and diel temperatures of 75F. ere compared for (a) duration of prehatch period and (b) viability. The experiment as replicated three times and as the prehatch periods did not vary by more than one day for any given day of the cycle, the results of the three replicates ere pooled (Table II). Under the above conditions, the prehatch period for eggs laid each day of the first 17 days of the cycle ere similar, averaging 29 days from laying to eclosion ; the pre-hatch period increased for eggs laid near the end of the cycle. Under diel conditions, the pattern as similar to the preceding but averaged 3.5 days over the same 17 da.ys. Again, eggs laid near the end of the cycle required a longer pre-hatch period. The viability of the cggs shoed more variation than the pre-hatch period; eggs laid under both constant and diel conditions shoed a similar pattern. Eggs laid on the first day of the cycle had lo viability but eggs laid from the znd through the l2th day had a hatch rate of 75-1 %. Viability then decreased sharply and only o-ro % of the eggs laid near the end of the cycle hatched; hoever, this lo viability involved only l-12 % of the total eggs laid. B. Effect of initial tick eight on oviposition (i) Pattern of oviposüion of #cks of different initial eight. The engorged female tick is essentially a sac filled ith nutrient (blood) and the necessary organs and metabolic pathays to convert the nutrient to eggs. At the end of the egg-laying cycle there is little left of the tick except the exo-skeleton, residual reproductive tissues, and the by-products of metabolism. The differential in eight beteen the initial eight and the residual eight of the tick is thus close to the eight of the nutrient available for conversion to eggs. To expressions of the efficiency of this conversion are used throughout this study. (a) Egg proditction index (Apparent conversion index). This measure is obtained by the formula Weight of eggs _..,... h f d. k X roo - egg product1n mdex. Imtia 1 e1g t o engorge tic

7 -57 - TABLE II. - Viability and pre-hatch period of eggs laid throughout the oviposition cycle by ticks held under constant and 12 hour diel cycle of temperatures averaging 75 F. Day of oviposition cycle Prehatch period clays Constant Percent hatched Prehatch periocl da ys Diurnal Percent hatchecl IO Sr II I r I 32 2 r I II This as a useful means of obtaining the expected eight of eggs from a knon eight of engorged females. (b) Nutrient index (Real conversion i!ldex). This measure of egg production is obtained by the formula Weight of eggs x roo = nutrient index. Initial eight of engorged tick - residual eight of tick This formula as a definition of the ay in hich blood ingested as converted into eggs as measured by eight. Thus the egg production index and nutrient index of the ticks (Fig. r) ere 62 % and 86 % respectively. The latter figure indicates a high efficiency in that only 14 % of the total nutrient available as expended in converting the remainder to eggs. Preliminary observations suggested that ticks of different eights did not oviposit similarly at the same temperature. This aspect as further studied by comparing the pattern of oviposition of four groups of ticks (Table III) of different eights ith that illustrated in Fig. r. Three differences ere noted beteen the performances of the groups : (a) the smallest females laid all their eggs in a shorter time span than the others; (b) groups I, II and V had lo egg production indices; (c) groups I and II had lo nutrient indices and group V had a loer e:fficiency

8 -58 - of conversion than groups III and IV. From these results it as concluded that ticks in the eight range of I8-225 mg. ere of optimal size and that small ticks, particularly those 5 mg. or less, ere inefficient. The largest number of eggs laid per day (day 4) as the same for each group, suggesting that the rate of oviposition as the same for all groups. The small ticks, having less nutrients to convert to eggs, completed oviposition in the shortest time. TABLE III. - Pattern of oviposition of five groups of ticks of different eights. Group IV are those illustrated in Figure r. Mean initial eight of groups I II III IV V 5 mgm. 112 mgm. 182 mgm. 225 mgm. 262 mgm.. Day of ISt eggs laid Day 25 % eggs laid Day 5 % eggs laid Day 75 % eggs laid Day 99 % eggs laid 8 9 IO II 9 Day finished laying 9 II 13 I4 14 Peak egg laying Apparent conversion 4.7 % 48.9 % 54.2 % 62. % 59.9 % Real conversion 67.1 % 75.5 % 83.8 % 86.o % 8r.5 % No. ticks involved IO (ii) T1:ck sfae and eight of eggs laid. KITAOKA and YAJIMA (1958) demonstrated linearity beteen the initial cight of the engorged tick and the number of eggs laid. Their experiment as repeated but the basis of comparison as eight, rather than number, of eggs laid. In addition, both the egg production and nutrient indices ere calculated. Over 45 ticks, ranging in eight from II to 56 mg. ere maintained at 85 F. for I7 days. The total egg production of each tick as then plotted against its initial eight. The ticks ere then grouped into 2 mg. eight classes, the mean egg eight and standard deviation per class calculated and plotted on the same diagram. The data ere analysed again folloing removal from the analysis of all ticks hich lay outside to standard deviations about the mean. A ne mean (Fig. 3) and standard deviations ere obtained. Telve percent of the original sample no lay outside the ne mean ± to standard deviations, I % above and II % belo. The corrected mean (Fig. 3) is virtually linear, thus confirming the ork of Kitaoka and Yajima (I958). The smallest tick to oviposit eighed I7 mg. but only one of five ticks eighing less than 2 mg. oviposited ; all ticks over 2 mg. laid eggs. The mean egg production and nutrient indices, based on the corrected sample, are also illustrated (Fig. 3). It is clear that ticks IOO mg. or less are not as efficient in converting the blood meal to eggs. Ticks in the range 1-37 mg. have a remarkably uniform efficiency of conversion and the standard deviation as small. A single specimen eighing 56 mg. as studied but omitted from the curve (Fig. 3) ; egg production and nutrient indices of 42 % and 72 % ere obtained.

9 1-- z u :: a f ",,,, o- _.... _--_ o _-... ~ - _, _... E 1 E (.{') <.9 <.9.i..L 1-- I < ORIGINAL WEIGHT mgm FIG. 3 - Relationship beteen egg production and initial eight of ticks. Egg production and nutrient indices at top of figure : egg production index - clotted line; nutrient index - solid line. The II % of the original sample hich returned unexpectedly lo conversion efficiencies ere of considerable interest. This II % as evenly distributed over the eight range under study and not confined to a specific eight class. This suggested that the factors responsible for the lo pro ductivity ere not eight dependent but occurred naturally in about II % of the tick population. One possible explanation as that this portion of the tick population had some fault in "the blood-concentrating mechanisms. Thus these ticks, although fully engorged, contained a hi~her proportion of ater in the blood meal (and hence a loer nutritional store for egg production) than the rest of the population. If this hypothesis as correct, then a similar sample from th..e same parental line of ticks, reared on the same hosts, should sho a similar proportion of indi viduals unable to fully concentrate the blood meal.

10 -6 - This hypothesis as tested by randomly selecting some 18 freshly engorged females over the eight range mg. Each female as placed in a vial and dried in an oven at l5 F. for six days and then eighed again. The loss of eight (i. e. - moisture) expressed as a percentage of the initial eight, as remarkably uniform (Table IV). Generally, most ticks (89.3 %) ~o~t. bet~en 55 and 6I % (mean 59 %) of their initial eight; no tick lost less than 55 % of the mihal eight. Significantly, 1.7 % of the sample lost 64 % or more of their initial eight, indicating that these ticks had, initially, a higher ater content, and presumably did not conc~ntrate their blood meal as efficiently as the others. This figure compares most favourably ith the figltre of II % of the ticks hich laid less than the expected eight of eggs. The loer conversion values and smaller number of eggs laid by small ticks is also of interest. It has been Our experience that engorged ticks from resistant hosts are consistently smaller than thos~ fr~m Susceptible animals ; Zebu (Bos indicits) and Zebu crossbred animals (Bos taitros X Bos indicus) tend to be resistant to tick infestation and ticks from these animals tend to be small (WILKINSON, 1962; ROBERTS, 1968). Use of such animals, together ith Bos taitros breeds s:lected for l"esistance, ould produce feer ticks hich ould not have the reproductive potenhal of the lctrger ticks produced on susceptible hosts. Thus an additional degree of biological control coulci be exerted on the B. microplus population. TABLE IV. - Percent loss of eight of engorged B. microplits dried at l5 F. for seven days. Percell.t Loss \Veirrht " Number of ticks in class 67 -> I.7 % l lz t 1 54 %.l 89.3 % >- 54 Sotal No. =.=c=--=-- z 187 t % +

11 -6I - AcKNOWLEDGEMENTS This ork as carried out hen the author as ith the Division of Entomology, CSIRO, Long Pocket Laboratories, Indooroopilly, Queensland, Australia. It is a pleasure to acknoledge the advice and encouragement offered by Dr. R. H. WHARTON throughout this study, as ell as the assistance of all my colleagues, especially Dr. Roger TATCHELL. Particular thanks are due to Misses Diana McBRYDE and Gloria lviulligan and to lvir. Robin CARNELL, ho efficiently carried out the mechanics of the study. Professor John PHIPPS, Dr. Roger PICKAVANCE and lvir. Paul WILKINSON shoed great patience in editing the manuscript. Mrs. A. Gillian CAMPBELL prepared the illustrations. LITERATURE CITED HARLEY (K. L. S.), Studies on the survival of the non-parasitic stages of the cattle tick Boophilits microplus in three climatically dissimilar districts of North Queensland. - Aust. J. Agric. Res., 17 : 387-4ro. HITCHCOCK (L. F.), Studies on the non-parasitic stages of the cattle tick, Boophilits miàoplits (Canestrini) (Acarina : Ixodidae). - Aust. ]. Zool., 3 : 293-3rr. KITAOKA (S.) and YAJIMA (A.), Physiological and ecological studies on some ticks. II. Phase change of ovipositing ability ith blood-sucking quantity. - Bull. Nat. Inst. Animal Health (Tokyo) 34 : LEGG (].), Sorne observations on the life history of the cattle tick (Boophilits australis). - Proc. R. Soc. Queen., XLI : :tvicculloch (R. N.) and LEWIS (I. J.), Ecological studies of the cattle tick, Boophilus microplits in the north coast district of Ne South Wales. - Aust. ]. Agric. Res., 19 : 689-7ro. ROBERTS (].), Resistance of cattle to the tick Boophilits microplits (Canestrini). I. Development of ticks on Bos tauros. - ]. Parasit., 54 : WHARTON (R. H.) and UrncH (K. B. \iv.), The relation beteen engorgment and dropping of Boophilits microplus (Canestrini) (Ixodidae) to the assessment of tick numbers on cattle. - ]. Aust. Ent. Soc., 9 : WILKINSON (P. R.), Selection of cattle for tick resistance, and the effect of herds of different susceptibility on Boophilits populations. - Aust. ]. Agric. Res., 13 : WILKINSON (P. R.), Factors affecting the distribution and abondance of the cattle tick in Australia : observations and hypotheses. - Acarologia XII : WILKINSON (P. R.) and WILSON (]. T.), Survival of cattle tick in central Queensland pastures. - Aust. ]. Agric. Res., 1 :