The whip scorpion, Mastigoproctus giganteus (Uropygi: Thelyphonidae), preys on the chemically defended Florida scrub millipede, Floridobolus penneri (Spirobolida: Floridobolidae).
Floridobolus, like most millipedes, is well protected from predators. When disturbed, it quickly coils into a tight spiral, shielding its head and all of its appendages with its smooth, hard integument and may remain coiled for a long time, for an average of 4.6 [+ or -] 0.7 min (n = 10, [+ or -] SEM) in laboratorytests. In response to mild to strong provocation, such as squeezing or biting, Floridobolus discharges large amounts of a liquid defensive secretion from paired glands that open along the sides of its body (Attygalle et al. 1993; Eisner et al. 1998). The volatile exudate, a blend of six 1, 4-benzoquinones, appears to act as a conventional repellent to invertebrate and vertebrate enemies and the quinone vapors are potent irritants of the eyes of mice, birds, and humans (Eisner et al. 1978). Prior to this publication, the only known predator of Floridobolus is the larva of a phengodid beetle, Phengodes laticollis meridiana Wittmer. The larva instantly paralyzes the millipede by biting its neck with sharp mandibles and the defensive quinones remain sealed in the glands while the larva eats the uncontaminated internal tissues, starting at the neck and moving toward the anus, leaving behind empty rings of armored body segments (Eisner et al. 1998; Eisner et al. 2005).
We now report that the giant whip scorpion, Mastigoproctus giganteus (Lucas) (Arachnida: Uropygi) consumes Floridobolus, even if the quinone-based secretion is released upon attack. In Aug-Sep 2008 we collected millipedes at 3-day intervals in 96 pitfall traps arranged in sets of 12 each at 8 randomly chosen sites in scrubby flat-woods near the southern end of the Archbold Biological Station, Highlands County, Florida (ranging from 27[degrees]08" 20" N, 81[degrees]21' 18" W to 27[degrees]07' 19" N, 81[degrees]21' 54" W elevation 40-43 m). Each trap consisted of a plastic bucket (17.5 cm diameter x 19 cm depth, 3.8 liter capacity) placed in the ground so that the rim was flush with the sandy soil and filled with 3-5 cm of sandy soil. During the first 2 weeks of Aug, while checking all of the buckets on 4 different days, we found 17 M. giganteus individually in the traps. In 6 instances there were partially consumed Floridobolus with them, 6 traps contained both M. giganteus and 1 or more living Floridobolus, and 5 had M. giganteus and no millipedes. An additional 35 traps each contained 1-4 living but zero dead Floridobolus on the days they were checked. In addition, at this time we never found dead or injured Floridobolus in the approximately 100 traps containing large carnivorous carabid beetles, Pasimachus strenuus LeConte, or in about 30 traps containing very large lycosid spiders, Hogna osceola (Gertsch and Wallace). Our field data suggested that millipede mortality was highly correlated with the presence of giant whip scorpions: dead, partially consumed millipedes were found only in buckets where M. giganteus were present. This conclusion subsequently was reinforced when on 3 occasions in the field we discovered a giant whip scorpion holding a millipede in its powerful pedipalps while it bit the prey middorsally at an intersegmental membrane (Fig. 1).
Fig. 1 shows sand grains adhering to the cuticle of the millipede, a sign that the prey may have discharged its defensive secretion in response to squeezing or biting inflicted by the giant whip scorpion. Secretory discharge was confirmed when several, but not all millipedes, were quickly attacked as they slowly approached M. giganteus during laboratory trials staged in sand-filled arenas. In some instances the predator's attack did not evoke release of secretion by the millipede (Fig. 2). Microscopic examination of the interior of the segmental rings a day after the millipedes were eaten, with the technique of Eisner et al. 1998, confirmed the presence of replete defensive glands.
[FIGURES 1-4 OMITTED]
However, in some instances a giant whip scorpion's powerful pedipalpal grasp and subsequent middorsal bite caused the millipede immediately to discharge quinones from many glands (Fig. 3), but the predator was not deterred. The odor of the secretion was very noticeable to us at this time. In all instances, within 15-30 min after an attack commenced, the whip scorpion had inflicted a fatal incision between 2 segments of its prey and liquefied tissues were ingested (Fig. 4).
Although we showed that Floridobolus is highly vulnerable to attack by M. giganteus, Florida scrub millipedes spend most of their lives underground and giant whip scorpions are not common predators in scrub, so we suspect the rate of predation might be low in the field. Our results extend the dietary diversity of M. giganteus beyond insects, arachnids, and amphibians (Cloudsley-Thompson 1958, Punzo 2000) to the diplopods.
We thank Jan Weaver, Nicola Ihasz, Alan Rivero, and Whitney Hummel for assistance in the field, M. Deyrup and H. M. Swain for advice and encouragement, Archbold Biological Station for research facilities and a variety of services, and the helpful comments of 2 anonymous reviewers. This study was supported by the Archbold Biological Station, by the Development Fund of Missouri University, and by Rinker Materials and Walt Disney World Hospitality and Recreation Corporation awarded to H. R. Mushinsky and E. D. McCoy at the University of South Florida.
On several occasions in Aug-Sep 2008 we detected giant whip scorpions, Mastigoproctus giganteus, feeding on rare Florida scrub millipedes, Floridobolus penneri, in bucket-style pitfall traps in the field. Subsequently in laboratory feeding trials we determined that M. giganteus will readily attack, kill, and consume F. penneri even if the prey discharges its irritating defensive secretion.
Attygalle, A. B., Yu, S.-C., Meinwald, J., and Eisner, T. 1993. Defensive secretion of the millipede Floridobolus penneri. J. Nat. Prod. 56: 1700-1706.
Cloudsley-Thompson, J. L. 1958. Spiders, Scorpions, Centipedes and Mites. Pergammon Press, London. 118 pp.
Deyrup, M. 1994. Florida scrub millipede Floridobolus penneri Causey, pp. 254-256 In M. Deyrup and R. Franz [eds.], Rare and Endangered Biota of Florida, Volume IV Invertebrates. University Press of Florida, Gainesville, Fl. 798 pp.
Eisner, T., Alsop, D., Hicks, K., and Meinwald, J. 1978. Defensive secretions of millipeds, pp. 41-72 In S. Bettini [ed.], Arthropod Venoms. Springer-Verlag, Berlin. 977 pp.
Eisner T., Eisner, M., Attygalle, A. B., Deyrup, M., and Meinwald, J. 1998. Rendering the inedible edible: circumvention of a millipede's chemical defense by a predaceous beetle larva. Proc. Natl. Acad. Sci. USA. 95:1108-1113.
Eisner, T., Eisner, M., and Siegler, M. 2005. Secret Weapons: Defenses of Insects, Spiders, Scorpions, and Other Many-legged Creatures. Belknap Press of Harvard University Press, Cambridge, MA. 372 pp. Punzo, E 2000. Diel activity patterns and diet of the giant whipscorpion Mastigoproctus giganteus (Lucas) (Arachnida, Uropygi) in Big Bend National Park (Chihuahuan Desert). Bull. British Aracnol. Soc. 11: 385-387.
Shelley, R. M. 2000. Annotated checklist of the millipeds of Florida (Arthropoda: Diplopoda). Insecta Mundi 14:241-251.
James E. Carrel (1) and Eric J. Britt (2,3)
(1) University of Missouri, Division of Biological Sciences, 209 Tucker Hall, Columbia, MO 65211-7400 USA
(2) University of South Florida, Division of Integrative Biology, 4242 East Fowler Avenue, SCA 110, Tampa, FL 33620 USA
(2, 3) Current address: Archbold Biological Station, 123 Main Drive, Venus, FL 33960
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|Title Annotation:||Scientific Notes|
|Author:||Carrel, James E.; Britt, Eric J.|
|Date:||Sep 1, 2009|
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