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Predation of the Freshwater Crayfish Orconectes cristavarius by the Fishing Spider Dolomedes scriptus
R. Katie Scott, Zachary W. Dillard, David A. Foltz, and Zachary J. Loughman

Southeastern Naturalist, Volume 15, Issue 3 (2016): N37–N39

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N37 2016 Southeastern Naturalist Notes Vol. 15, No. 3 R.K. Scott, Z.W. Dillard, D.A. Foltz, and Z.J. Loughman Predation of the Freshwater Crayfish Orconectes cristavarius by the Fishing Spider Dolomedes scriptus R. Katie Scott1, Zachary W. Dillard1, David A. Foltz2, and Zachary J. Loughman1,* Abstract - Herein we detail a predation event on Orconectes cristavarius (Spiny Stream Crayfish) by Dolomedes scriptus (Striped Fishing Spider). On 12 July 2015, we discovered a female Striped Fishing Spider along the banks of Knox Creek, Buckhannon County, VA, feeding on a young-of-the-year Spiny Stream Crayfish. The spider had ingested the majority of the crayfish’s abdomen at the time of discovery, and had used silk to anchor the crayfish to the undersurface of the rock where feeding was taking place. We discuss the possible role of crayfish in the diet of Dolomedes spiders and provide a detailed description of the spider ’s microhabitat. Orconectes freshwater crayfish are confirmed prey items for various aquatic and semiaquatic animals throughout North America. Several fishes, turtles, snakes, mammals, and Cryptobranchus alleganiensis (Daudin) (Hellbender Salamander) have been recorded as predators of Orconectes crayfish (Jezerinac et al. 1995, Pfleiger 1996, Taylor and Shuster 2004); arthropods other than crayfish have not historically been recorded as Orconectes predators. Here we describe an observed predation event on a young-of-theyear Orconectes cristavarius (Taylor) (Spiny Stream Crayfish) by an adult Dolomedes scriptus (Hentz) (Striped Fishing Spider; Family Pisauridae). The Striped Fishing Spider is a large, semiaquatic fishing spider found throughout eastern and central North America that frequents boulder fields and debris snags along larger-order stream banks (Bradley 2013, Carico 1973). Like other Dolomedes species, the Striped Fishing Spider is an opportunistic predator that preys on small aquatic or terrestrial invertebrates and vertebrates. This spider hunts for prey freely over water rather than capturing meals in a web (Barbour 1921, Carico 1973), discovering prey items through disruptions of surface tension of the water (Bleckmann 1988). The Spiny Stream Crayfish is a freshwater crayfish endemic to the central Appalachians’ Big Sandy, Guyandotte, Kentucky, and New river basins, where it occurs in small streams to large rivers, often in considerable numbers (Taylor 2000, Taylor and Shuster 2004). We observed a female Striped Fishing Spider feeding on a young-of-the-year Spiny Stream Crayfish along the banks of Knox Creek, Buckhannon County, VA, on 12 July 2015 at 15:30 h. We overturned the rock maintaining the spider and crayfish while we were sampling for crayfish near the stream edge in a shallow (less than 25 cm), low-velocity run with minimum canopy coverage (0–10%) and a low-gradient bank composed of several small to moderately sized boulders. The spider was resting upside down on the undersurface of a 25 cm x 30 cm sandstone slab within 0.5 m of the stream. Substrate under the boulder was composed of gravel and cobbles, as well as a small amount of spring-fed water that formed a shallow eddy. We could not determine where the spider made initial contact with its prey, though it is likely that the eddy present under the rock where we found the spider was the place of predation. Both the crayfish and spider were upside down near the outer margin of the slab 1West Liberty University, Department of Natural Sciences and Mathematics, 208 University Drive, West Liberty, WV 26074. 2Civil and Environmental Consultants, Inc., 333 Baldwin Road, Pittsburgh, PA 15205. *Corresponding author - Manuscript Editor: Bronwyn Williams Notes of the Southeastern Naturalist, Issue 15/3, 2016 2016 Southeastern Naturalist Notes Vol. 15, No. 3 N38 R.K. Scott, Z.W. Dillard, D.A. Foltz, and Z.J. Loughman (Fig. 1). The spider had employed silk threads (Fig. 1) to help anchor the crayfish to the bottom of the rock. At the time of discovery, the female Striped Fishing Spider was grasping the crayfish at the cephalthorax/abdomen junction with her chelicerae and fangs, with the ventral surface of the crayfish facing her. The female spider’s chelicerae were bored into the ventral side of the prey’s upper abdomen, and most of the telson and abdomen of the crayfish had been ingested (Fig. 1). Following disturbance, the spider showed no interest in releasing its prey, and remained motionless for our 10-min observation. We returned the rock to its original placement so as not to further disturb the feeding event. Fish predation by semi-aquatic spiders is geographically widespread (Carico 1973, Nyffeler and Pusey 2014), and Dolomedes spp. (fishing spiders) frequently consume small vertebrates (Carico 1973, Kissane 2001, Machado and Lipinski 2014). However, records of freshwater crayfish predation by fishing spiders are rare. Figiel (1995) used juvenile Procambarus sp. (crayfish) as prey for Dolomedes triton (Walckenaer) (Six-spotted Fishing Spider) in a captive environment. Our observation may represent the first published predation event of a Dolomedes species feeding on crayfish in a natural situation. During certain times of the year, crayfish may represent an important food source for Striped Fishing Spiders as well as other fishing spiders that prefer lotic waterways (i.e., Dolomedes vittatus Walckenaer and Dolomedes tenenbrosus Hentz [Dark Fishing Spider]). Many crayfish in the genus Orconectes employ a life-history strategy that involves saturating streams with large numbers of young-of-the-year individuals in April through June (Moore et al. 2013, Taylor and Shuster 2004). Juvenile crayfish seek out slack-water environments and are frequently encountered near stream margins and within shallow eddies along runs and pools (Jezerinac et al. 1995, Taylor and Shuster 2004) and also frequent Figure 1. Dolomedes scriptus with young of the year Orconectes cristavarius as prey. N39 2016 Southeastern Naturalist Notes Vol. 15, No. 3 R.K. Scott, Z.W. Dillard, D.A. Foltz, and Z.J. Loughman shallow pools isolated from main channels during periods of drawdown. All of these environments are confirmed hunting locations of lotic fishing spiders. Dolomedes spiders are probably alerted to the presence of crayfish by the high level o f activity of the latter. It seems that crayfish would be able to fend off an attack through use of their chelipeds. However, if fishing spiders engage crayfish with the same strategy described for fish predation, in which the spiders grasp fishes in the back of the head and wrap their legs around their prey, the chelipeds of crayfish could be easily rendered useless following a venomous bite (Nyffler and Pusey 2014). Further investigation is needed t o determine the overall importance of crayfish as prey for fishing spiders, as well as any impacts this predation may have on young-of-the-year crayfish cohorts. Crayfish are the largest freshwater arthropods in North America; it is only fitting that one of the largest araenomoprh spiders in North America has now been confirmed to include them as prey . Acknowledgments. We thank David Howard, Troy Hubbard, Luke Sadecky, and Nicole Sadecky for assistance in the field. Literature Cited Barbour, T. 1921. Spiders feeding on small cyprinodonts. Psyche 28:131–13 2. Bleckmann, H. 1988. Prey identification and prey localization in surface-feeding fish and fishing spiders. Sensory Biology of Aquatic Animals. 619–641. Bradley, R.A. 2013. Common Spiders of North America. University of California Press, Oakland, CA. 288 pp. Carico, J.E. 1973. The Nearctic species of the genus Dolomedes (Araneae: Pisauridae). Bulletin of the Museum of Comparative Zoology 144:435–488. Figiel, C.R. 1995. Foraging tactics of a semi-aquatic spider, Dolomedes triton. Ph.D. Dissertation. University of Mississippi, University, MS. 94 pp. Jezerinac, R.F., G.W. Stocker, D.C. Tarter. 1995. The Crayfishes (Decapoda: Cambaridae) of West Virginia. Bulletin of the Ohio Biological Survey Bulletin 10(1). 1 93 pp. Kissane, K.C. 2001. Slug eating by the pisaurid spider Dolomedes tenebrous Hentz, 1843. British Arachnological Society Newsletter 91:4–5. Machado, M., and V.M. Lipinski. 2014. Predation event on tadpole of Scinax aromothyella (Anura: Hylidae) by the fishing spider Thaumasia velox (Araneae: Pisauridae) in a rainforest of Southern Brazil. Herpetology Notes 7:517–518. Moore, M.J., R.J. DiStefano, and E. Larson. 2013. An assessment of life-history studies for USA and Canadian crayfishes: Identifying biases and knowledge gaps to improve conservation and management. Freshwater Science 32(4):1276–1287. Nyffeler, M, and B.J. Pusey. 2014. Fish predation by semi-aquatic spiders: A global pattern. PLoS ONE 9(6):e99459. doi:10.1371/journal.pone.0099459. Pflieger, W.L. 1996. The Crayfishes of Missouri. Missouri Department of Conservation, Jefferson City, MO. 152 pp. Taylor, C.A. 2000. Systematic studies of the Orconectes juvenilis complex (Decapoda:Cambaridae), with descriptions of two new species. Journal of Crustacean Bio logy 20:132–152. Taylor, C.A., and G.A. Schuster. 2004. Crayfishes of Kentucky. Illinois Natural History Survey, Champaign, IL. Special Publication 28. 219 pp.