1998. The Journal of Arachnology 26:330-334DRAGLINE-MEDIATED MATE-SEAR - PDF document

1998. The Journal of Arachnology 26:330-334DRAGLINE-MEDIATED MATE-SEARCHING INTRITE PLANICEPS(ARANEAE, SALTICIDAE)Phillip W. Taylor':Department of Zoology, University of Canterbury, Private Bag4800, Christchurch 1, New ZealandABSTRACT.Trite planicepsSimon 1899, a common New Zealand jumping spider (Salticidae), livesin the cavities formed by rolled-up leaves of New Zealand flax TAYLOR-SALTICID MATE-SEARCHINGFigure1.-Trite planicepsmale entering the cav-ity formed by a rolled-up leaf of New Zealand flax(Phormium tenax).Spider's body length = 11 mm.were maintained using standard methods(Jackson & Hallas 1986). Voucher specimensofT.planicepshave been deposited by RobertJackson at the Florida State Collection of Ar-thropods (Gainesville).Procedures closely resemble those used byClark & Jackson (1994). The arena was con-structed from a 90 mm-diameter plastic petridish (Fig. 2). The petri dish (base and lid) wascut in half, and an opaque plastic screen wasglued into each half-base midway between thecut edge and the point of greatest distance tothe cut edge. A 10 mm-diameter half-circlehole was melted into the cut edge of each halfpetri dish immediately adjacent to the wall atthe end to which the screen was fixed.One 'half-arena' was selected at random tobe 'draglined'. The half-circle hole and openside of this half-arena were taped over and a`source spider' was introduced. The sourcespider was left for 2 h to deposit draglines.After removing the source spider, the drag-lined half-arena was used in a test within thefollowing 2 h.To begin a test, the draglined half-arena wasmatched up with a clean half-arena so that thehalf-circle holes on the edge of the half-arenasACBA331Figure 2-Diagram showing the arena used totest substrate preferences (viewed from above withthe two `half arenas' separated). (A) Opaque plasticscreens. (B) 10 mm diameter hole for insertion ofthe transfer tube.formed a single 10 mm-diameter hole in thefloor. The `test spider' was placed in a clearplastic `transfer tube' (40 mm X 10 mm ex-ternal diameter) which was then corked atboth ends. The transfer tube was inserted intothe hole in the arena floor so that the tubeprotruded 1-2 mm into the arena and was heldin place by the two half-arenas pressing to-gether. The cork protruding into the arena wasthen removed and the two half lids were slidinto place. The test spider climbed up out ofthe transfer tube into the arena, and the testbegan when the spider's palps were above thearena surface. The amount of time that the testspider spent on each side of the arena wasrecorded for 10 min, using the palps as thepoint of reference for location. If a spiderstood with one palp on each side of the arena,it was counted as still being on the side pre-viously occupied by both palps(i.e.,failing tomove to the other side). Each spider was usedonly once as a test spider or source spider forany particular treatment(e.g.,male on maledraglines).Mate-searching on rolled-up leaves.-This experiment was designed to investigatewhether mate-searching byT.planicepsmalesis facilitated by draglines left by conspecificfemales on leaf surfaces in the laboratory, andwhether similar cues are present in nature.Freshleaf tests:Twenty rolled-up flax 332Figure 3.-Diagram showing the arena used totest the effects of dragline cues on mate-searchingefficiency. (A) Arrows indicating two dried leavesthat are not rolled-up. (B) Rolled-up leaf. (C) Arrowindicating the opening of the cavity within therolled-up leaf. The same spatial arrangement ofleaves was adopted for all tests.leaves containingT.planicepsnests and ma-ternal females were collected on the eveningprior to testing. Fresh leaves would typicallybe covered by draglines deposited by residentfemales in nature. Because many salticid pher-omones are water-soluble (Jackson 1987), andtherefore susceptible to being depleted byrain, leaves were collected at least 5 days afterthe most recent rainfall. Residents were re-moved, and the rolled-up leaves were cut to500-550 mm long with the opening near themiddle.On the day of testing, each rolled-up leafwas mounted (using plastic insulating tape) ona tripod with two other dried leaves (500-550mm long) that were not rolled up (Fig. 3). Thetripod and attached leaves were placed in aclean glass tank (300 mm X 300 mm floor,600 mm high). The opened cage of aT.plan-icepsmale was placed on the tank floor andthe tank was sealed with a glass lid. All ex-periments were started in the middle 2 h ofthe laboratory light phase (12L:12D). Afterthe male left his cage 1 recorded, at 5 minintervals for a maximum period of 5 h, wheth-THE JOURNAL OF ARACHNOLOGYer the male had entered the cavity within therolled-up leaf. If the male could not be seenin the tank, the rolled-up leaf was carefullyunrolled to confirm that the male was inside(end of test). Each leaf was used only once(i.e.,20 tests in total).Cleaned leaf tests:After fresh leaf testsended, the glass tanks, tripods and leaves(each of the 20 tripod and leaf setups werekept intact) were thoroughly washed with dis-tilled water and then ethanol to remove drag-lines and pheromones. They were then left for7 days, so that remaining pheromones coulddissipate, and the testing procedure was re-peated. This treatment's title `cleaned leaves'was justified because, in other salticids, agingand washing with polar solvents such as wateris known to eliminate the effectiveness ofdraglines at eliciting associative behavior andcourtship of males (Jackson 1987; Clark &Jackson 1995).Lab-draglined leaf tests:After cleaned leaftests the 20 tanks, tripods and leaves (tripodand leaf setups still intact) were washed againand allowed to dry for 24 h. The adult femalethat was in the leaf in nature was then re-placed in the leaf, left for 7 days in the closedtank, and testing was repeated again. On theday before testing a lab-draglined leaf, the res-ident was removed and the whole arena (tank,tripod, leaves), except the rolled-up leaf, waswashed.The same group of 20 males was used forthe 20 tests using fresh, cleaned, and lab-drag-lined leaves, but each male was used onlyonce per treatment and the same male was notused for more than one treatment of a partic-ular leaf. To ensure that results were not con-founded by shrinkage of the openingsofrolled-up leaves during the interval betweentreatments, maximum width and length ofopenings were measured to the nearest milli-meter following the first and third treatments,and compared.RESULTSSubstrate preferences.-Malesspent moretime on the side of the arena containing drag-lines of conspecific females than on the cleanside but there was no evidence that females(mated or virgin) either associated with oravoided draglines deposited by males (Table1). Also, neither males nor females showed TAYLOR-SALTICID MATE-SEARCHINGTable 1.-Proportions of total time spent on the draglined half-arena vs. clean half-arena. Comparisonsare by Wilcoxon signed ranks test.any tendency to associate with or avoid drag-lines of same-sex conspecifics (Table 1).Mate-searching on rolled-up leaves.-Males found the openings and entered the cav-ities within rolled-up leaves during the.5 htesting period in all tests using fresh(n = 20)or lab-draglined leaves(n = 20),and in18 of20tests using cleaned leaves (Fisher exact�test, P 0.3).However, latency until enteringcleaned rolled-up leaves (median83min;quartiles33-136min) was greater than forfresh leaves (median23min; quartiles12--42min; Wilcoxon signed ranks test, P 0.005)or lab-draglined leaves (median18min; quar-tiles11-25min; Wilcoxon signed ranks test,P .001). There was no evidence that la-tency to entry of rolled-up leaves differed forfresh and lab-draglined leaves (Wilcoxon&#x 000;signed ranks test, P 0.2).Also, there wasno evidence that length or width of the open-ings to rolled-up leaves changed during thethree week interval between tests (Wilcoxon&#x 000;signed ranks test, for both dimensions P 0.9).DISCUSSIONMales of some salticids begin courtingwhen they come into contact with draglinesdeposited by conspecific females (Jackson1987).Although females' draglines do notelicit courtship inT.planicepsmales (Jackson1987),the present study shows that females'draglines do elicit associative behavior inmales of this species. In this respect,T.plan-icepsresemblesPortia fimbriata(Doleschall1859)and P.labiata(Thorell1882),the onlyother salticids for which comparable data areavailable (Jackson1987;Clark & Jackson1995).Although other possibilities cannot beruled out, related studies suggest the specificrelevant cues eliciting association inT.plan-icepsmales are pheromones loosely bound to333the nest and dragline silk of females (Jackson1987,Oden1981in Pollard et al.1987,Clark& Jackson1994).In addition to associating with females'draglines in choice tests,T.planicepsmalesfound females' nesting sites sooner when fe-males' draglines were present on rolled-upleaves. Although increased success at mate-searching may be explained by associative be-havior alone, we should also consider the pos-sibility thatT.planicepsmales activelysearched for the openings of rolled-up leaveswhen they contacted the draglines. Femalesalticids typically build their nests in only anarrow range of easily identified microhabitats(Hallas & Jackson1986)and commonly re-side at a single nesting site with their devel-oping young for many weeks (Jackson1979;Taylor1997).Brooding females deposit drag-lines as they move about near their nests, andthis would be the most common natural con-text in which an area would be densely cov-ered by draglines. Male salticids that encoun-ter dragline-covered areas might next searchvisually both for females directly and for typ-ical nesting microhabitats.The present study ofT.planicepshas animportant feature that emulates nature morecompletely than previous studies using othersalticids. In addition to using draglines depos-ited in the laboratory (all tests of associationand 'lab-draglined leaves'), I also used leaveson which draglines had been deposited in na-ture (`fresh leaves'). Identifying a similar re-sponse to lab-draglined and fresh leavesstrengthens the assertion that dragline cues arepresent and used byT.planicepsmalessearching for mates in nature. The need forsuch confirmation was highlighted by Persons& Uetz(1996)in the context of predation.These authors found that a lycosid spider,Test spiderSource spidernmedianUpperquartileLowerquartilePMaleMated female470.780.910.52.001Mated femaleMale370.480.770.30�0.3Virgin femaleMale370.470.630.34�0.5MaleMale560.510.680.34�0.4Mated femaleMated female920.560.690.36�0.5 334Schizocosa ocreata(Hentz1844),associateswith areas recently occupied by large numbersof crickets but express doubt that adequateconcentrations of the kairomones responsiblewould occur naturally. Similar doubts couldbe expressed about studies of how salticidsuse dragline-cues, as none have confirmed thatsimilar cues are present in adequate density innature. Results of this study provide some as-surance that laboratory assays of salticid re-sponses to dragline-cues produce results thatare indeed relevant in nature.ACKNOWLEDGMENTSThis research was carried out with supportfrom a New Zealand Universities Postgradu-ate Scholarship. The manuscript was preparedwith additional support from Binational Sci-ence Foundation grant 93-125 to Oren Hassonand David Clark. Allon Bear, Robert Clark,Robert Jackson and Mary Whitehouse provid-ed useful discussions and comments on themanuscript.LITERATURE CITEDBlest,A.D.,D.C. O'Carroll & M. Carter.1990.Comparative ultrastructure of layer I receptormosaics in principal eyes of jumping spiders: theevolution of regular arrays of light guides. CellTiss. Res., 262:445-460.Clark, D.L. 1994. Sequence analysis of courtshipbehavior in the dimorphic jumping spiderMae-via inclemens(Araneae, Salticidae). J. Arachnol.,22:94-107.Clark, R.J. & R.R. Jackson. 1994. 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