Coleman & Zigler

The rediscovery of Caecidotea nickajackensis in Tennessee and Alabama

William T. Coleman1,2 & Kirk S. Zigler1,3

1Department of Biology, Sewanee: The University of the South, 735 University Avenue, Sewanee, Tennessee, 37383, USA [email protected] [email protected] (corresponding author)

Key Words: Caecidotea nickajackensis, Caecidotea richardsonae, Nickajack Cave, Marion County, Horseskull Cave, Jackson County, Raccoon Mountain Caverns, Pan Gap Cave, Hamilton County, Alabama, Tennessee, United States, Isopoda.

Nickajack Cave in Marion Co., Tennessee has a colorful history. Located along the Tennessee River with “probably the largest cave entrance in the eastern United States,” it was used by Native Americans and river pirates, mined for saltpeter, operated as a commercial cave and even visited by Johnny Cash. The cave was flooded after the completion of Nickajack Dam in 1967, leaving only a portion of the entrance above water (Barr 1961; Matthews 2007). Nickajack Cave was one of the first caves in the United States studied by biologists (Cope and Packard 1881) and is the type locality for six troglobionts: the crayfish Cambarus hamulatus (Cope, 1881), the amphipod Crangonyx antennatus Cope and Packard, 1881, the isopods Caecidotea nickajackensis Packard, 1881 and Caecidotea richardsonae Hay, 1901, the beetle Pseudanophthalmus nickajackensis Barr, 1981, and the pseudoscorpion Lissocreagris nickajackensis (Muchmore, 1966). Three of these species—Crangonyx antennatus, Cambarus hamulatus, and Caecidotea richardsonae—have broad distributions. Lissocreagris nickajackensis is known from one other cave (Peck 1989). The flooding of Nickajack Cave caused the disappearance of the only known habitat of Caecidotea nickajackensis and Pseudanophthalmus nickajackensis. Both species have been presumed extinct (Lewis 2009). This paper amends that record in light of the rediscovery of Caecidotea nickajackensis from sites in Alabama and Tennessee.

Caecidotea nickajackensis was described in Cope and Packard (1881) with brief comments and drawings of the habitus and slightly enlarged first antenna and uropods. The type specimen was lost after Cope and Packard (1881) failed to document its storage site. Hay (1901) subsequently collected a second isopod species from Nickajack Cave and described it as C. richardsonae. Stewart Peck made a final collection of isopods from Nickajack Cave in April 1967. Peck’s collection included both C. nickajackensis and C. richardsonae, confirming Hay’s finding that the cave contained two species (Lewis 2009). Lewis (2009) redescribed C. nickajackensis, designating one of Peck’s 1967 specimens as the C. nickajackensis neotype, replacing Cope and

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Packard’s (1881) lost holotype. Caecidotea nickajackensis and C. richardsonae are morphologically similar but can be distinguished by the palmar margin of the propodus of the gnathopod, where C. nickajackensis has large processes that C. richarsonae lacks (Lewis 2009).

We conducted biological surveys of caves near the intersection of Tennessee, Alabama, and Georgia during 2013. In the course of this work, we collected Caecidotea isopods from several caves. While morphologically similar to C. richardsonae, microscopic examination indicated that specimens from Horseskull Cave (Alabama Cave Survey no. AJK613), Jackson Co., Alabama and Raccoon Mountain Caverns (Tennessee Cave Survey no. THM4), Hamilton Co., Tennessee, had processes on the propodus palmar margin, whereas specimens from Pan Gap Cave (Tennessee Cave Survey no. THM11), Hamilton Co., Tennessee, did not (Figure 1). Based on this difference, we suspected that the specimens from Horseskull Cave and Raccoon Mountain Caverns were C. nickajackensis, and these identifications were subsequently confirmed by Julian Lewis.

Figure 1. Gnathopods of (A) Caecidotea nickajackensis from Horseskull Cave (8 mm male) with two distinct processes on the propodus palmar margin and (B) C. richardsonae from Pan Gap Cave (12 mm male) lacking such processes.

Our collections also provide some information about the life history and ecology of C. nickajackensis. We made the first observation of an ovigerous female (Raccoon Mountain Caverns, Hamilton County, Tennessee, 18 July 2014, 20 immatures). This is consistent with the reproductive period and brood size observed in other stygobiotic Caecidotea (Fong 2009; Zigler and Cooper 2011). Although C. nickajackensis and C. richardsonae can be found in the same cave (as in Nickajack Cave), there is some evidence that they are found in distinct habitats. The C. nickajackensis specimens collected by Peck in 1967 were from a rimstone pool (Lewis 2009), and our collections of C. nickajackensis from Horseskull Cave and Raccoon Mountain Caverns were both

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from drip pools. In contrast, we collected C. richardsonae in Pan Gap Cave from the cave stream. This suggests the possibility that C. nickajackensis is an epikarst species, whereas C. richardsonae may be more commonly found in cave streams. Further studies of various aquatic cave habitats in other caves could determine whether this is a consistent pattern.

The records of Caecidotea nickajackensis are significant as they indicate the species did not go extinct after the flooding of Nickajack Cave. Our collections are the first observations of C. nickajackensis since 1967. The range of C. nickajackensis is now known to extend from southern Marion and Hamilton Counties in Tennessee into northeastern Jackson County, Alabama (Figure 2). Although currently known only from three caves on the southeastern edge of the Cumberland Plateau, C. nickajackensis is likely present in other caves in the region.

Figure 2. Records of Caecidotea nickajackensis and C. richardsonae near the junction of Tennessee, Alabama, and Georgia. Dark circles overlapping light circles represent caves with records of both species. Counties where C. nickajackensis has been collected are labeled. The range of C. richardsonae extends northeast to Virginia and further south in Alabama.

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Collection Information

Specimens were collected by hand, placed in 90% ethanol, and stored at -20°C. Specimen length was measured from the front of the head to the end of the pleotelson. 1. Caecidotea nickajackensis, Horseskull Cave, Jackson County, Alabama, 8 mm male (Figure 1A) collected 14 July 2013, W.T. Coleman and K.S. Zigler. 2. Caecidotea nickajackensis Raccoon Mountain Caverns, Hamilton County, Tennessee, 14 mm male, 2 females (one ovigerous) collected 18 July 2013, W.T. Coleman and K.S. Zigler. 3. Caecidotea richardsonae Pan Gap Cave, 12 mm male collected 28 June 2013 (Figure 1B), W.T. Coleman and K.S. Zigler.

Acknowledgments

We thank the Southeastern Cave Conservancy for permission to work in Horseskull Cave, Steve Perlaky for permission to work in Raccoon Mountain Caverns, and Patty Perlaky for assistance surveying in Raccoon Mountain Caverns. We also thank Julian Lewis for confirming our species identifications.

Literature Cited

Barr, T.C. 1961. Caves of Tennessee. State of Tennessee, Department of Environment and Conservation, Division of Geology, Bulletin 64: 1–567.

Cope, E.D., and Packard, A.S. 1881. The fauna of Nickajack Cave. American Naturalist 15: 877–882.

Fong, D.W. 2009. Brood size of the stygobiotic asellid isopod Caecidotea pricei from a spring run in West Virginia, USA. Speleobiology Notes 1: 1–2.

Hay, W.P. 1901. Two new subterranean crustaceans from the United States. Proceedings of the Biological Society of Washington 14: 179–180.

Lewis, J.J. 2009. On the identity of Caecidotea nickajackensis (Crustacea: Isopoda: Asellidae). Proceedings of the Biological Society of Washington 122: 215–224.

Matthews, L.E. 2007. Caves of Chattanooga. National Speleological Society, Huntsville, Alabama, USA. 192pp.

Peck, S.B. 1989. The cave fauna of Alabama: Part I. The terrestrial invertebrates (excluding insects). National Speleological Society Bulletin 51: 11–33.

Zigler, K.S., & Cooper, G.M. 2011. Brood size of the stygobiotic asellid isopod Caecidotea bicrenata bicrenata from Franklin County, Tennessee, USA. Speleobiology Notes 3: 1–3.

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