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First Record of the American Alligator (Alligator mississippiensis) as a Host to the Sea Turtle Barnacle (Chelonibia testudinaria)
James C. Nifong and Michael G. Frick

Southeastern Naturalist, Volume 10, Issue 3 (2011): 557–560

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First Record of the American Alligator (Alligator mississippiensis) as a Host to the Sea Turtle Barnacle (Chelonibia testudinaria) James C. Nifong1,* and Michael G. Frick2 Abstract - Chelonibia testudinaria (Sea Turtle Barnacle) and other closely related barnacle species of the genus Chelonibia are known to utilize a variety of organisms for their attachment substrate. These include the calcified exoskeleton of marine crustaceans and chelicerids, the epidermis of manatees, and the carapace regions of all extant sea turtle species. Here, we present the first records of an Alligator mississippiensis (American Alligator; Alligatoridae) as a host for C. testudinaria. Introduction. The 23 extant species of crocodilians, including Alligator mississippiensis Daudin (American Alligator), are known to serve as hosts to a variety of parasitic organisms. These include endo-parasites such as blood helminths, pentastomids, and nematode worms (Junker and Boomker 2006, Moravec 2001, Riley and Huchzermeyer 2000) and ecto-parasites such as leeches and ticks (Monroe and Garret 1979, Rainwater et al. 2001). While endo-parasites are more prevalent by frequency of occurrence and total parasitic biomass (Gabrey et al. 2008), high concentrations of ecto-parasites can occur and potentially cause detrimental impacts to the health of an individual. For example, ticks and leeches are reported to attach to the surface of crocodilian eyes, nictitating membranes, ear-drum/ear-opening, cloaca, and soft portions of the epidermis, causing damage to blood capillaries and soft tissues, and potentially harboring bacteria/ viral infections (Rainwater et al. 2001). A number of ecto-parasites are reported to occur on American Alligators, the most frequently encountered are various species of freshwater leeches (Class: Hirudinea), usually found attached to portions of the skin between hardened scutes and other soft tissues of the mouth, ear openings, cloaca, and eyes. A few observations of ticks attaching to soft tissues under the ear flap (Kent Vliet, University of Florida, Department of Biology, Gainesville, FL, pers. comm.) have been made, but ticks do not seem to be prevalent ecto-parasites in wild populations of crocodilians (Rainwater et al. 2001). Conversely, the occurrence of non-parasitic, commensal epi-bionts other than various aquatic plants and algae is rare. To our knowledge, the only previous record of a crocodilian hosting a non-plant commensal epi-biont is of two Chelonibia testudinaria L. (Sea Turtle Barnacle) from a single Crocodylus porosus Schnieder (Estuarine Crocodile) inhabiting coastal northern Australia (Monroe and Garret 1979). Here, we present novel observations of C. testudinaria (Subphylum: Crustacea, Class: Maxillopoda), utilizing American Alligators as a host in a coastal estuary of northeastern Florida. In addition, this epi-biont is the first organism to successfully utilize the hardened keratinized portions of scute tissue and/or osteoderms of American Alligators for an attachment substratum. Observations. During night-time captures on 16 June 2010 at 2320 within Guana Lake, an estuarine impoundment located within the Guana River Wildlife Management Area, Ponte Vedra, fl(N 30.07052, W -81.34116), a large adult male American Alligator (tail tag: GTM 125, total length [TL]: 292.5 cm, snout-to-vent length [SVL]: 1University of Florida, Department of Biology, PO Box 118525, Gainesville, fl32611. 2Friends of the National Zoo, Smithsonian National Zoological Park, PO Box 37012, MRC 5516, Washington, DC 20013-7012. *Corresponding author - Notes of the Southeastern Nat u ral ist, Issue 10/3, 2011 557 558 Southeastern Naturalist Vol. 10, No. 3 Figure 1. Photograph of Chelonibia testudinaria (Sea Turtle Barnacle) attached to the caudal scute whirl of a 2.9-m Alligator mississippiensis (American Alligator) captured in Guana Lake, Ponte Vedra, FL. Inset: magnified view of the attached barnacle. Figure 2. Photograph of wound with remains of embedded Chelonibia testudinaria (Sea Turtle Barnacle) damaged during capture of a sub-adult Alligator mississippiensis (American Alligator) in Guana Lake, Ponte Vedra, FL. 2011 Southeastern Naturalist Notes 559 148.6 cm) was captured. Upon inspection, the individual was found to host a single large Sea Turtle Barnacle (2.5 cm diameter x 1.5 cm height) attached to the center of a scute located on the lateral edge of a caudal tail whirl (Fig. 1). The second observation of Sea Turtle Barnacle attachment was during the capture of a sub-adult male American Alligator (tail tag: GTM136, TL: 149.4 cm, SVL: 74.6 cm) on 8 September 2010 within the same general location in Guana Lake (N 30.02322, W -81.33223). Following capture, an odd-shaped wound was located on the median scute of the first dorsal caudal tail whirl (Fig. 2), this wound contained pieces of broken shell determined to be the remnants of a barnacle likely to have been broken off during capture. Discussion. These observations represent the first published record of a crustacean using a host species within the family Alligatoridae for attachment. Furthermore, molecular work is being performed on the Chelonibia species complex that also use manatees and crabs as hosts in order to determine the degree of species host-specificity and variation in use of particular attachment substrata (i.e., hard calcified shell, keratinized epidermis, soft tissues). We believe that the occurrence of Sea Turtle Barnacles on American Alligators in this location is due to the broad range of salinities (0–40 ppt) contained within the Guana Lake impoundment and its proximity to the ocean via the nearby St. Augustine Inlet, which supplies the adjacent estuary. Sea Turtle Barnacles are a common shell epibiont found to colonize multiple sea turtle species, including those found within estuarine habitats (Zardus and Hadfield 2004). Of these species, Chelonia mydas (L.) (Green Sea Turtle) is highly abundant within the estuary adjacent to the Guana Lake impoundment and are potentially the source of C. testudinaria populations. Personal observations by one of the authors (J.C. Nifong), indicate resident alligators within the Guana Lake impoundment rarely leave the aquatic habitat for long periods of time (>12 hours), potentially permitting the settlement and propagation of marine epi-bionts. The prevalence of Sea Turtle Barnacle attachment in this population has yet to be determined. However, surveys to establish baseline data on the overall frequency and abundance of barnacle epi-bionts on resident American Alligators in Guana Lake are planned for 2011, as well as broad-scale surveys to establish the frequency of epi-bionts in other estuarine-inhabiting populations. Assessments of American Alligators performed in fully marine (34 ppt) salt marshes surrounding Sapelo Island, GA and estuary habitats (salinity ranging from 10–40 ppt) within Cape Canaveral, flhave not provided evidence of Sea Turtle Barnacle attachment. Through radio and GPS telemetry studies in these locations, we have found that American Alligators repeatedly travel to and from freshwater wetlands for re-hydration and possibly shed those epi-bionts intolerant of freshwater, acquired while using marine and/or estuarine habitats. These findings indicate there is much to be learned from the study of American Alligator ecology and the role that they play as hosts to marine invertebrates. Acknowledgments. These findings were produced while conducting research under an award from the Estuarine Reserves Division, Office of Ocean and Coastal Resource Management, National Ocean Service, National Oceanic and Atmospheric Administration at the Guana Tolomato Matanzas Estuarine Research Reserve Ponte Vedra, FL. Additionally, we thank Justin Ellenberger, Tyler Mosteller (Guana River Wildlife Management Area), and Kevin Torregrosa (St. Augustine Alligator Farm Zoological Park) for assistance during alligator captures. All captures were performed under FWC Special Use Permit # SPGS- 10-43 and University of Florida IACUC Permit # 201005071. Special thanks are due to two anonymous reviewers and John D. Zardus for comments on this manuscript. 560 Southeastern Naturalist Vol. 10, No. 3 Literature Cited Gabrey, S., K. Franklin, and M. Bodri. 2008. Preliminary investigation in the use of logistic regression to predict parasite intermediate hosts. Case study: Dujardinascaris waltoni (Nematoda: Ascarididae) in the American Alligator (Alligator mississippiensis). Georgia Journal of Science 66:85–96. Junker, K., and J. Boomker. 2006. A Check-list of the pentastomid parasites of crocodilians and freshwater chelonians. Onderstepoort Journal of Veterinary Research 73:27–36. Monroe, R., and R. Garrett. 1979. Chelonia testudinaria (L.) (Cirripedia, Coronulidae) on Crocodylus porosus Schneider, a new host record. Crustaceana 36:108. Moravec, F. 2001. Some helminth parasites from Morelet’s Crocodile, Crocodylus moreletii, from Yucatan, Mexico. Folia Parasitologica 48:47–62. Rainwater, T.R., S.G. Platt, R.G. Robbins, and S.T. McMurry. 2001. Ticks from a Morelet’s Crocodile in Belize. Journal of Wildlife Diseases 37:836. Riley, J., and F.W. Huchzermeyer. 2000. Diet and lung parasites of swamp forest Dwarf Crocodiles (Osteolaemus tetraspis osborni) in the Northern Congo Republic. Copeia 2000:582–586. Zardus, J.D., and M.G. Hadfield. 2004. Larval development and complemental males in Chelonibia testudinaria, a barnacle commensal with sea turtles. Journal of Crustacean Biology 24:409–421.