Nymphal Cicadas (Hemiptera: Cicadidae) as a Prey Item of Shovelnose Sturgeon (Scaphirhynchus platorynchus) in the Lower Mississippi River Audrey B. Harrison1,*, Steven G. George1, and William T. Slack1 Abstract - Stomach contents of 3 Scaphirhynchus platorynchus (Shovelnose Sturgeon) collected in the Lower Mississippi River in January 2010 yielded 44 specimens of cicada nymphs, Diceroprocta sp. The fish were collected during a sudden rise in water level. The floodplain-dwelling cicada were likely washed out of their terrestrial habitat and into the river, where opportunistic sturgeon were foraging. Hemiptera: Cicadidae (Cicadas) are terrestrial insects that are fossorial as nymphs. Members of the genus Diceroprocta are annual cicadas that commonly occupy woodland and riparian habitats and have been reported to emerge from areas previously covered in water (Davis 1928, Ellingson et al. 2002). Previous dietary studies of Scaphirhynchus platorynchus Rafinesque (Shovelnose Sturgeon) show that members of this species feed primarily on benthic invertebrates, with larval Trichoptera, Ephemeroptera, and Diptera comprising the majority of their food intake. Terrestrial invertebrates have been recorded in dietary analyses of sturgeon, but such reports include only commonly occurring insects and spiders that were most likely swept into the waterway. Previous studies do not list nymphal cicadas as a dietary item for this species (e.g., Hoover et al 2007, Modde and Schmulbach 1977, Wanner et al. 2007). Sturgeon specimens were obtained 27–29 January 2010 for a contaminant study that focused on organs and tissue. Sturgeon were collected near the sandy bank of the river, along a 14.48-km stretch of the lower Mississippi River (river kilometers 497.29–511.77), using trotlines baited with worms. Morrow et al. (1998) illustrated the effectiveness of trotlines in capturing Shovelnose Sturgeon in big-river environments, and their use for sampling Scaphirhynchus spp. (river sturgeon) has subsequently been established by numerous other works (Bettoli et al. 2009, Killgore et al. 2007, Murphy et al. 2007, Phelps et al. 2009). Stomachs of 14 Shovelnose Sturgeon (327–681 mm FL) were dissected, and 3 individuals (484, 560, and 672 mm FL) contained nymphal cicadas. The trotlines containing sturgeon with ingested cicadas were set 34.7, 37.5, and 55.8 m from shore along low-sloping sand flats, and the near-shore habitat included willows and bottomland hardwoods. The total number of cicada nymphs ingested was 44. Using a key to the genera and sex for last instar nymphs and cast nymphal skeletons of Eastern North American Cicadidae (Moore 2010), all were identified as Diceroprocta sp. One fish fed heavily on cicadas—its stomach contained 41 cicadas, while the other two sturgeon had a total of three combined. Stomachs of all 14 sturgeon examined also contained other invertebrates, including: Trichoptera, aquatic Diptera, aquatic Coleoptera, Ephemeroptera, and Crustacea, which are all typical prey items of Shovelnose Sturgeon (Hoover et al. 2007, Modde and Schmulbach 1977). Of the 44 cicadas collected, 22 were males, 15 were females, and 7 were of undetermined sex. Eleven were retained as voucher specimens and were deposited in the Mississippi Museum of Natural Science (MMNS) and the Sanborn Collection (AFSC). Most ingested cicadas were in excellent condition for 1US Army Corps of Engineers, Engineer Research and Development Center, Environmental Laboratory, 3909 Halls Ferry Road, Vicksburg, MS 39180. *Corresponding author - Audrey.B.Harrison@ usace.army.mil. Notes of the Southeastern Nat u ral ist, Issue 10/2, 2011 371 372 Southeastern Naturalist Vol. 10, No. 2 preservation. Specimens were relatively equal in size, with a mean total length of 19.44 mm and a mean head width of 6.81 mm. It is unusual that sturgeon could access nymphal cicadas because of the fossorial lifestyle of the immature insect. Shovelnose Sturgeon are known to feed along the benthic substrate of the river, opportunistically consuming aquatic invertebrates, making cicada nymphs an atypical prey item. However, river stage prior to and during the sample period ranged from 11.9 m to 13.8 m, only 1.6 m below flood stage (USGS 07294800, 23–29 January 2010; NGVD29). This rise in river level of almost 2 m could have washed cicadas from near-shore erosional areas, or near-shore habitat could have been inundated by the rising river, providing Shovelnose Sturgeon access to additional forage areas not available during lower river stages. Both scenarios seem plausible, since cicadas collected were all last instar nymphs, likely making their way to the soil surface for emergence in the summer months, and since the condition of the near-shore habitat (i.e., willows and bottomland hardwoods) is typical of Diceroprocta. Acknowledgments. This project was supported by three US Army Corps of Engineers offices: the Mississippi Valley Division, the New Orleans District, and the Dredging Operation and Environmental Research Program of the ERDC. We thank the US Army ERDC-EL Fish Ecology Team, Vicksburg, MS for their work in the field collecting and processing the sturgeon used in this analysis. Dr. Bill Stark of Mississippi College and Dr. Allen Sanborn of Barry University confirmed the identification of the cicadas. The manuscript was reviewed by Bill Stark, Jan Hoover, and Jack Killgore. Permission was granted byt the Chief of Engineers to publish this information. Literature Cited Andersen, D.C. 1994. 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