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First Record of the American Alligator (Alligator
mississippiensis) as a Host to the Sea Turtle Barnacle
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 - firstname.lastname@example.org.
Notes of the Southeastern Nat u ral ist, Issue 10/3, 2011
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
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