1998. The Journal of Arachnology 26:113-116

RESEARCH NOTE

THE EFFECTS OF REPRODUCTIVE STATUS ON SPRINT SPEED IN THE SOLIFUGE, EREMOBATES MARATHONI (SOLIFUGAE, EREMOBATIDAE)

Costs associated with reproduction are de- gravid females of the solifuge Eremobates lineated by trade-offs between the current re- marathoni Muma 1970 . To my knowledge, no productive capacity of an animal and the prob- previous data on sprint speed or the relation- ability of its future survival and reproductive ship between sprint speed and reproductive success (Williams 1966) . The successful anal- status exist for the Solifugae . ysis of life history parameters depends on our Eremobates marathoni is a common inhab- ability to identify proximate mechanisms by itant of the Big Bend region of Trans Pecos which such costs are mediated . Documented Texas (Punzo 1997), which lies within the costs associated with reproduction include de- northern confines of the Chihuahuan Desert. I creased survivorship resulting from physio- collected gravid (G) and nongravid (NG) fe- logical or behavioral changes that accompany males by hand at night with the aid of a head reproduction (Hirshfield & Tinkle 1975 ; Bell lamp as they wandered over the surface of the 1980). For example, if escape from a predator ground, or through the use of pitfall traps as depends on the speed or endurance of a po- described previously (Punzo 1994a) . All so- tential prey organism, then any reduction in lifuges were collected within a 3 km radius of the locomotor performance of gravid females Marathon, Texas (Brewster County) during could increase the risk of predation . Loco- July 1996 . A detailed description of the ge- motor performance has been correlated with ology and dominant vegetation of this area is survivorship in many species of vertebrates given by Tinkam (1948) . (Shine 1980; Punzo 1982 ; Huey et al . 1984 ; Solifuges were transported back to the lab- Svensson 1988; Brodie 1989 ; Jayne & Ben- oratory, housed individually in plastic con- nett 1990; Plummer 1993) but little informa- tainers (30 X 15 X 10 cm), and fed on a diet tion exists for arthropods in general (Winfield of crickets and mealworm larvae as described & Townsend 1983 ; Crowl & Alexander 1989; by Punzo (1997b). Gravid females were iden- Punzo 1989) or for arachnids specifically tified by the presence of embryos visible (Moffett & Doell 1980 ; Shaffer & Formanow- through the ventral body wall . I recorded the icz 1996). following measurements for each G and NG Solifuges are common representatives of female : body length (BL) in mm ; width of the arachnid fauna in desert regions world- propeltidium (WP) in mm, and body weight wide (Turner 1916 ; Muma 1967 ; Cloudsley- (BW) in grams . Adult solifuges, as well as Thompson 1977 ; Wharton 1987) . These pred- eggs, were maintained at 25-27 °C and 70- ators may forage over a considerable area ac- 72% relative humidity in a Percival Model tively searching for prey (Muma 1966 ; Whar- 816 environmental chambers (Boone, Iowa). ton 1987 ; Punzo 1994b, 1995a), and rely on Adult females were removed from these speed to escape from encounters with aggres- chambers only when subjected to sprint speed sive conspecifics or potential predators analyses . Voucher specimens have been de- (Cloudsley-Thompson 1977 ; Wharton 1987 ; posited in the Invertebrate Collection at the Punzo 1995b, 1997) . In the present study, I University of Tampa . compared the sprint speeds of gravid and non- I measured the sprint speed of 20 solifuges 113 1 14 THE JOURNAL OF ARACHNOLOGY

Table 1 .-Measurements for body length (BL) and width of propeltidium (WP) in millimeters, body weight in grams, and sprint speed (cm/sec) for females of Eremobates marathoni . Data represent means (+SD) for 20 females for each of the following groups : nongravid females ; gravid females while carrying embryos and 24 hours post-oviposition .

Nongravid Gravid Post-oviposition Body length 23 .8 (2 .1) 22 .7 (1 .5) 23 .1 (2 .7) Propeltidium width 5.71 (0 .4) 6.14 (0 .6) 5.84 (0 .2) Body weight 3.49 (0.2) 4.62 (0 .1) 3.71 (0 .3) Sprint speed (em/sec) 23.6 (2 .4) 14.5 (1 .3) 21.7 (1 .9)

in a linear race track (length = 90 cm ; width gentle stream of compressed air was intro- = 6 cm) . The floor of the track was construct- duced through the intake valve . In response to ed of wood and covered with coarse plastic the air flow, the solifuge would immediately carpet material . The floor was marked at 10 begin to run out of the start chamber and into cm intervals with black tape . I attached a the runway . Since preliminary observations piece of clear acrylic tubing (5 cm diameter) had indicated that solifuge sprint speed was that was cut in half lengthwise to the bottom fastest over the first 40 cm, I used the data for of the floor. This prevented the solifuges from locomotor performance over this distance for climbing or escaping while running and also all statistical analyses . I used a stopwatch to eliminated shadows . One end of the track was record the amount of time required for a so- closed by a plastic panel and designated as the lifuge to cross the 40 cm mark on the runway. start chamber (10 cm in length) where the so- Data on sprint speeds were expressed in lifuge was restrained from entering the run- cm/sec . way (80 cm) by a hemispherical cardboard All statistical analyses used in this study gate positioned between slits in the tube . The follow procedures described by Sokal & Rohlf plastic panel was fitted with an intake valve (1981) and Wilkinson (1984) . They were con- through which a gentle stream of compressed ducted using Stat View (Abacus Concepts, air could be introduced in order to initiate run- Inc., Berkeley, California) and SYSTAT ning (Punzo 1989) . The track was placed un- (SYSTAT, Inc ., Evanston, Illinois). der a 50 W fluorescent lamp . Animals were Gravid (G) females ran at a significantly deprived of food for 48 h prior to testing . slower speed than nongravid (NG) females Sprint speed trials were conducted on 20 (Table 1 ; t = 7.14, P < 0.01). Following ovi- NG females and 20 G females . All of the NG position, post-oviposition (PO) females ran females were tested once. Each of the G fe- significantly faster than they did while carry- males was also tested once at each of two re- ing embryos (Wilcoxon matched pairs test ; z productive states : gravid, but prior to ovipo- = 3.27, P < 0.01). There was no significant sition (G), and within 24 h after oviposition difference between the sprint speeds of NG (post-oviposition, PO) . The amount of time and PO females . between the initial testing of gravid femles There were no significant differences in and oviposition ranged from 8-14 days . The body length (BL) (t = 0.53, P > 0.50), and first trial for all animals occurred within 4-7 width of propeltidium (WP) (t = 0 .65, P > days after being brought to the laboratory. The 0.35) between G and NG solifuges used in this second trial for PO females occurred two days study . The mean body weight (BW) of G fe- after oviposition . Each female was weighed males was 38 .5% higher than that of NG fe- immediately following the running trials on a males due to the weight of the embryos and Metler electronic analytical balance and re- associated body fluids . The number of eggs turned to its holding cage . oviposited per G female ranged from 19-46 At the start of each trial, a solifuge was with a mean of 26.6 ± 3 .8 SD . The number placed in the start chamber with its head fac- of nymphs per female that successfully com- ing the runway and allowed to habituate for 2 pleted embryonic development and hatched min prior to running . Following this period, ranged from 9-32 with a mean of 17 .7 ± 2 .9 the cardboard gate was lifted manually and a SD . PUNZO-REPRODUCTIVE STATUS AND SPRINT SPEED 1 1 5

The results of this study, the first reported tion and the evolution of reproductive effort . for a solifuge, indicate that pregnancy results Proc . Nat. Acad. Sci ., USA, 72 :2227-2231 . in a significant reduction in locomotor perfor- Huey, R.B ., A.E Bennett, H. John-Alder & K .A. mance . This has important ecological impli- Nagy . 1984 . Locomotor capacity and foraging behavior of Kalahari lacertid lizards . Anim. Be- cations because a decrease in sprint speed may hav., 32:41-50 . increase the risk of predation in a significant Jayne, B .C. & AT Bennett . 1990. Selection on lo- way . Solifuges frequently utilize their loco- comotor performance capacity in a natural pop- motor capacities to escape predation . (Preda- ulation of garter snakes . Evolution, 44 :1204- tors include scorpions, theraphosid spiders, 1229 . other solifuges, centipedes, road runners, and Moffett, S . & G .S . Doell . 1980. Alteration of lo- badgers (pers . obs .)) . Similar results have comotor behavior in wolf spiders carrying nor- been reported for the striped scorpion, Cen- mal and weighted cocoons . J . Exp. Zool ., 213 : truroides vittatus (Say 1887) by Shaffer & 219-226 . Formanowicz (1996) . In this study, sprint Muma, M .H. 1966 . Feeding behavior of North speed was determined for each female at each American Solpugida . Florida Entomol ., 49 :199- of three reproductive states (pregnant, while 216 . carrying young on her back, and after neo- Muma, M .H. 1967 . Basic behavior of North Amer- ican Solpugida. Florida Entomol ., 50 :115-123 . nates had dispersed from her back) . Sprint Plummer, M .V 1993 . Thermal ecology of arboreal speed for pregnant scorpions averaged 84% of green snakes, Opheodrys aestivus. J. Herpetol ., post-dispersal speeds . Sixty five percent of the 27:254-260. scorpions carrying young on their backs did Punzo, F 1982 . Tail autotomy and running speed not run at all when disturbed and assumed a in the lizards Cophosaurus texanus and Uma no- defensive posture while standing their ground . tata . J. Herpetol ., 16 :329-331 . Sprint speeds for the remaining 35% that did Punzo, E 1989 . Effects of hunger on prey capture run with young on their backs averaged only and ingestion in Dugesiella echina Chamberlin 61% of their post-dispersal speeds . (Orthognatha, Theraphosidae) . Bull . British Ar- achnol. Soc ., 8 :72-79. ACKNOWLEDGEMENTS Punzo, F 1994a . Trophic and temporal niche inter- I wish to thank J . Bottrell and B . Trivett for actions in sympatric populations of Eremobates Fichter and (Roew- assistance in collecting solifuges in the field, palpisetulosus E. mormonus er) (Solpugida: Eremobatidae) . Psyche, 101 :187- T. Punzo for assistance in maintaining soli- 194. fuges in the laboratory and construction of the Punzo, F 1994b . An analysis of feeding and opti- runway, B . Garman and A . Zenjarli for con- mal foraging behavior in the solpugid, Eremo- sultation on statistical analyses, J . Smith, P bates mormonus (Roewer) (Solpugida, Eremo- Sierwald, J . Berry, D . Formanowicz and batidae) . Bull . British Arachnol . Soc., 9 :293- anonymous reviewers for comments on an 298 . earlier draft of the manuscript, and the Uni- Punzo, E 1995a. Feeding and prey preparation in versity of Tampa for a Faculty Development the solpugid, Eremorhax magnus (Solpugida : Er- Grant which made much of this work possi- emobatidae) . Pan Pacific Entomol ., 71 :13-17. ble. Punzo, F 1995b . Intraspecific variation in life his- tory traits between sympatric populations of Er- LITERATURE CITED emobates palpisetulosus Fichter and Eremobates Bell, G . 1980. The costs of reproduction and their mormonus (Roewer) (Solpugida, Eremobatidae) . consequences . American Nat ., 116 :45-76. Bull . British Arachnol. Soc ., 10:109-113 . Brodie, E .D. 1989 . Behavioral modification as a Punzo, F 1997 . Dispersion, temporal patterns of means of reducing the costs of reproduction . activity, and the phenology of feeding and mat- American Nat ., 134 :225-238 . ing behavior in Eremobates palpisetulosus Fi- Cloudsley-Thompson, J .L . 1977. Adaptational bi- chter (Solifugae, Eremobatidae) . Bull . British ology of Solifugae . Bull . British Arachnol . Soc ., Arachnol . Soc ., 10(8) :303-307 . 4:61-71 . Shaffer, L .R . & D .R. Formanowicz. 1996 . A cost Crowl, TA . & J .E . Alexander. 1989 . Parental care of viviparity and parental care in scorpions : Re- and foraging ability in male water bugs (Belas- duced spring speed and behavioral compensa- toma flumineum) . Canadian J . Zool., 67 :513- tion . Anim . Behav., 51 :1017-1024 . 515 . Shine, R . 1980 . "Costs" of reproduction in rep- Hirshfield, M .E & D . Tinkle. 1975. Natural selec- tiles . Oecologia, 46 :92-100 . 1 16 THE JOURNAL OF ARACHNOLOGY

Sokal, R .R. & EJ . Rohlf. 1981 . Biometry . 2nd ed . dae) compared with that of nocturnal species . J. W.H . Freeman, San Francisco . Arachnol ., 14 :363-383 . Svensson, I . 1988 . Reproduction costs in two sex- Wilkinson, L . 1984 . SYSTAT : The system for sta- role reversed pipefish species (Syngnathidae) . J. tistics . Systat Inc ., Evanston, Illinois . Anim. Ecol ., 57 :929-942 . Williams, G .C. 1966 . Adaptation and natural se- Tinkam, E .R. 1948 . Faunistic and ecological stud- lection. Princeton Univ . Press, Princeton, New Jersey. ies on the Orthoptera of the Big Bend Region of Winfield, I .J. & C .R. Townsend . 1983 . The cost of Trans Pecos Texas . American Mid] . Nat ., 40 : copepod reproduction : Increased susceptibility 521-583 . to fish predation. Oecologia, 60 :406-411 . Turner, C .H . 1916 . Notes on the feeding behavior and oviposition of a captive American false-spi- Fred Punzo : Department of Biology, Box der (Eremobates fornicaria Koch). J. Anim . Be- 5F, University of Tampa, 401 W. Kennedy hav ., 6 :160-168 . Blvd., Tampa, Florida 33606 USA Wharton, R .A. 1987 . Biology of the diurnal Me- Manuscript received 13 March 1997, accepted 27 tasolpuga picta (Kraepelin) (Solifugae, Solpugi- May 1997.