Spatial variation of parasite infracommunities in the american alligator (alligator mississippiensis).
Our present study describes nematode, trematode, and pentastomid prevalence, intensity, and species richness of American alligators harvested in 2012 in Texas. We compared our results with previous findings of parasitism of alligators collected during the harvests in 2011 from Louisiana and Florida (Tellez, 2014) to assess similarities and differences in the pattern and distribution of alligator parasitism throughout the range of the host.
We collected a total of 17 alligator specimens from southeastern Texas near J. D. Murphree Wildlife Management Areas (29[degrees] 53'18"N, 94[degrees] 2'4"W) from legal hunters. We identified all of the alligators in this study as adults (total lengths from the tip of the snout to end of the tail were [greater than or equal to] 180 cm). We examined the gonads of some individuals during necropsies to determine sex (seven males, four females, six unknown). We removed the lungs, stomachs, and intestines from alligator corpses within 2-48 h of sacrifice and then transported the organs to McNeese State University, Lake Charles, Louisiana in a cooler. Upon arrival we placed the samples in a -80[degrees]C freezer until dissection. Upon dissection, we collected the parasites from respective organs, cleaned them in distilled water, and placed them in vials of 70% ethanol. We followed the guidelines of Daily (1996) for our parasite identification and preservation process.
We used Fisher's exact test in Quantitative Parasitology 3.0 (Quantitative Parasitology 3.0., Budapest, Hungary) to 1) examine parasite prevalence and mean intensity for Texas alligators, and 2) compare the prevalence variation of lung pentastomids, gastric nematodes, and intestinal helminths among alligators from Texas (TX), Western
Louisiana (LAW, n = 28), Eastern Louisiana (LAE, n = 17), and Florida (FL, n = 10). Global positioning system points of LAW, LAE, and FL collection sites are described in Tellez (2014). We also used Kruskal-Wallis tests in program R (R Foundation for Statistical Computing, Vienna, Austria, http://www.R-project.org) to analyze variation of parasite mean intensity as well as trematode and nematode species richness among locations. All tests were considered significant at P < 0.05.
We found 1,309 parasites (lung pentastomids, n = 22; gastric nematodes, n = 181; intestinal nematodes, n = 81; intestinal trematodes, n = 1,025) in concomitance with 100% parasite prevalence among TX alligators. Overall, the prevalence and intensity of Dujardinascaris waltoni was greater relative to other species parasitizing TX alligators (Table 1). Prevalence of the lung pentastomid Sebekia mississippiensis was 52.9%. We identified gastric and intestinal nematodes as Dujardinascaris waltoni (58.8%), Ortleppascaris antipini (29.4%), Brevimulticaecum tenuicolle (11.8%), and Brevimulticaecum baylisi (5.9%). We identified intestinal trematodes as Acanthostomum species (35.3%), Acanthostomum diplorum (35.3%), Acanthostomum gonotyl (5.9%), Acanthostomum pavidum (35.3%), Acanthostomum scyphocephalum (47.1%), Cryptogonomid (5.9%), Proctocaecum species (52.9%), Pseudocrocodillicola americanense (11.8%), and Timoniella loosi (11.8%; Appendix 1).
Our investigation of the parasite component community in alligators of Southeast Texas provides the first report of O. antipini, A. diplorum, A. gonotyl, A. scyphocephalum, and P. americanense from this region. Our finding of 100% parasite prevalence is unique and exceptional for a parasitic study, as parasites usually aggregate within a host population, i.e., infections are right-skewed because only a few individuals are heavily infected and the rest of the population possesses zero or few parasitic infections (Bush et al., 1997; D. Buth, pers. comm.). A previous study reported parasite prevalence of Southeast Texas alligators at 92% (Scott et al., 1997); thus, the data would suggest parasitic infection among alligator hosts in this region has remained marginally similar in 20 y. However, the prevalence of parasite species identified in Scott et al. (1997) has changed. Prevalence of the nematode species B. baylisi (40%) and B. tenuicolle (44%) documented in the 1990s has decreased from 40-5.9%, and 44-11.8%, respectively, in the current study. This perhaps reflects a decrease of the intermediate host for Brevimulticaecum spp. in the region. In contrast, prevalence of S. mississippiensis, D. waltoni, T. loosi, and A. pavidum increased significantly from 12-52.9%, 44-58.8%, 411.8%, and 8-35.3%, respectively. The increase of the aforementioned parasites may reflect wetland restoration implemented in 2000 in some areas of the J. D. Murphee Wildlife Management Area. Restoring marshland perhaps favored the increased abundance of the above parasites' primary intermediate hosts (particularly crab; Tellez and Nifong, 2014), consequently increasing the frequency of consumption and parasitic infection of alligators.
When we combined our results from TX alligators with LAW, LAE, and FL, collectively lung pentastomids illustrated a greater prevalence (77.2%) overall in comparison to intestinal helminths (70.7%) and gastric nematodes (58.8%), yet no significant difference was found (Fisher's exact test, P = 0.368). Florida alligators exhibited the greatest pentastomid prevalence and mean intensity (Fisher's exact test, P = 0.002; Kruskal-Wallis, P = 0.044) in addition to illustrating higher stomach prevalence and intensity relative to other locations (Kruskal-Wallis, P = 0.026; Fisher's exact test: P < 0.001). In contrast, prevalence and mean intestinal parasitism of LAW significantly differed from other locations (Fisher's exact test, P = 0.015; Kruskal-Wallis, P = 0.034).
En masse, we identified 14 species of trematodes and 7 species of nematodes among TX, FL, LAW, and LAE alligators (Appendix 2). The trematode species richness of LAE significantly differed in comparison to FL, TX, or LAW (Kruskal-Wallis, P = 0.042), where there was no significant difference in nematode species richness observed across the examined locations (Kruskal-Wallis, P > 0.05). Interestingly, we only found the presence of the nematode species Brevimulticaecum baylisi in TX alligators, Eustronglyides species in LAE and FL alligators, and Goezia species in FL alligators. Furthermore, the presence of the trematode species A. scyphocephalum and A. gonotylwas only found in TX alligators and not in other described locations. We found no trematodes in FL alligators.
In summary, lungs of Texas alligators are depauperate in species richness (similar to alligator populations from Louisiana and Florida) whereas the stomach and intestines are parasitized by a diversity of endoparasites. Secondly, the variation of lung, stomach, and intestinal parasite prevalence and intensity we found across the range of the alligators likely reflects the dissimilarity of intermediate host abundance and environmental parameters of host habitat. For example, the distinction between the relative parasite communities was most apparent between the alligators from Florida and Texas. The majority of alligators collected from Texas were from populations close to brackish or estuarine water systems whereas Florida alligators from this study were collected from freshwater inland aquatic microhabitats. Given that abiotic variables such as salinity, pH, temperature, and precipitation can affect the success of parasite transmission and fitness (Sures, 2004; Loreau et al., 2005; Poulin and Mouritsen, 2006; Campiao et al., 2012), it is likely the differential distribution and intensity of alligator parasitism is a consequence of these factors.
We would like to thank Dr. M. Merchant from McNeese State University for assisting us with the collection of alligator specimens from Texas and Dr. P. Siroski for his assistance with the Spanish abstract. We would also like to extend our gratitude to C. Choi for her lab assistance with dissections, parasite preparation, and identification.
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Submitted 24 April 2016.
Acceptance recommended by Associate Editor, Frederic Robert Govedich,
19 September 2016.
Helen Sung and Marisa Tellez *
Department of Ecology and Evolutionary Biology, University of California, Los Angeles, Los Angeles, CA 90095 (HS) Marine Science Institute, University of Santa Barbara, Santa Barbara, CA 93106 (MT)
* Correspondent: firstname.lastname@example.org
Table 1-Prevalence, mean intensity, and median intensity for lungs (Pentastomid), stomach (Nematode), and intestinal (Nematode, Trematode, and Acanthostomid) parasites of American alligators across Texas, Florida, Louisiana West (LAW), and Louisiana East (LAE) locations. Location Body location Parasite Prevalence (%) Texas Lungs Pentastomid 52.9 Stomach Nematode 47.1 Intestine Total 94.1 Nematode 64.7 Trematode 94.1 Florida Lungs Pentastomid 86.7 Stomach Nematode 90 Intestine Total 26.7 Nematode 26.7 Trematode 0 LAW Lungs Pentastomid 92.9 Stomach Nematode 28.6 Intestine Total 89.3 Nematode 28.6 Trematode 85.7 LAE Lungs Pentastomid 58.5 Stomach Nematode 63 Intestine Total 94.1 Nematode 58.8 Trematode 94.1 Location Body location Parasite Mean intensity Texas Lungs Pentastomid 2.44 Stomach Nematode 22.63 Intestine Total 69.13 Nematode 7.36 Trematode 64.04 Florida Lungs Pentastomid 33.19 Stomach Nematode 228.5 Intestine Total 9.13 Nematode 9.13 Trematode 0 LAW Lungs Pentastomid 12.42 Stomach Nematode 37.75 Intestine Total 106.5 Nematode 19.75 Trematode 176.29 LAE Lungs Pentastomid 17.9 Stomach Nematode 46.47 Intestine Total 175.64 Nematode 10.1 Trematode 100.19 Location Body location Parasite Median intensity Texas Lungs Pentastomid 2 Stomach Nematode 27 Intestine Total 42 Nematode 3 Trematode 35 Florida Lungs Pentastomid 30 Stomach Nematode 140 Intestine Total 6.5 Nematode 6.5 Trematode 0 LAW Lungs Pentastomid 10 Stomach Nematode 9.5 Intestine Total 51 Nematode 5.5 Trematode 44.5 LAE Lungs Pentastomid 15 Stomach Nematode 3 Intestine Total 55.5 Nematode 4 Trematode 52.5 Appendix 1-Nematode and trematode species richness from Alligator mississippiensis across Texas, Florida, Louisiana West Zone (LAW), and Louisiana East Zone (LAE) locations including total abundance, prevalence in percentage, and mean intensity (MI; mean number of parasites found in the infected hosts). Alligators from Texas were collected in 2012 and alligators from Florida, LAW, and LAE were collected in 2011. Texas Prevalence Species Total (%) MI Dujardinascaris waltoni 180 58.8 16.5 Ortleppascaris antipini 15 29.4 4 Brevimulticaecum tenuicolle 3 11.8 1.6 Brevimulticaecum baylisi 1 5.9 1 Goezia species 0 0 0 Eustronglyides species 0 0 0 Terranova lanceolata 0 0 0 Acanthostomid species 16 35.3 263.5 Acanthostomum diplorum 13 35.3 1 Acanthostomum gonotyl 5 5.9 5 Acanthostomum pavidum 10 35.3 1 Acanthostomum 16 47.1 1.5 scyphocephalum Cryptogonomid 1 5.9 1 Proctocaecum species 30 52.9 3 Pseudocrocodillicola 3 0 0 americanense Timoniella loosi 2 11.8 1 Archaeodiplostomum 0 0 0 acetubulata Cyathocotyle crocodili 0 0 0 Pseudocrocodillicola 0 0 0 georgiana Polycotyle ornata 0 0 0 Pseudocrocodillicola species 0 0 0 Florida Prevalence Species Total (%) MI Dujardinascaris waltoni 1,800 90 196 Ortleppascaris antipini 263 70 3 Brevimulticaecum tenuicolle 234 20 117 Brevimulticaecum baylisi 0 0 0 Goezia species 1 10 1 Eustronglyides species 3 10 3 Terranova lanceolata 0 0 0 Acanthostomid species 0 0 0 Acanthostomum diplorum 0 0 0 Acanthostomum gonotyl 0 0 0 Acanthostomum pavidum 0 0 0 Acanthostomum 0 0 0 scyphocephalum Cryptogonomid 0 0 0 Proctocaecum species 0 0 0 Pseudocrocodillicola 0 0 0 americanense Timoniella loosi 0 0 0 Archaeodiplostomum 0 0 0 acetubulata Cyathocotyle crocodili 0 0 0 Pseudocrocodillicola 0 0 0 georgiana Polycotyle ornata 0 0 0 Pseudocrocodillicola species 0 0 0 LAW Prevalence Species Total (%) MI Dujardinascaris waltoni 85 20 9 Ortleppascaris antipini 205 20 5 Brevimulticaecum tenuicolle 82 24 1 Brevimulticaecum baylisi 0 0 0 Goezia species 0 0 0 Eustronglyides species 0 0 0 Terranova lanceolata 4 4 2 Acanthostomid species 543 8 2 Acanthostomum diplorum 0 0 0 Acanthostomum gonotyl 0 0 0 Acanthostomum pavidum 1,279 68 14.5 Acanthostomum 0 0 0 scyphocephalum Cryptogonomid 361 52 12 Proctocaecum species 266 76 14 Pseudocrocodillicola 312 36 13 americanense Timoniella loosi 57 12 5 Archaeodiplostomum 167 20 14.5 acetubulata Cyathocotyle crocodili 1 4 1 Pseudocrocodillicola 98 28 10 georgiana Polycotyle ornata 38 16 7.5 Pseudocrocodillicola species 266 28 27 LAE Prevalence Species Total (%) MI Dujardinascaris waltoni 54 20 3 Ortleppascaris antipini 100 20 4 Brevimulticaecum tenuicolle 153 8 15.5 Brevimulticaecum baylisi 0 0 0 Goezia species 0 0 0 Eustronglyides species 2 8 1 Terranova lanceolata 4 4 4 Acanthostomid species 61 10 5 Acanthostomum diplorum 19 10 9.5 Acanthostomum gonotyl 0 0 0 Acanthostomum pavidum 1,077 60 7 Acanthostomum 0 0 0 scyphocephalum Cryptogonomid 940 85 20 Proctocaecum species 2,320 75 40 Pseudocrocodillicola 65 35 7 americanense Timoniella loosi 401 25 9 Archaeodiplostomum 206 30 18.5 acetubulata Cyathocotyle crocodili 0 0 0 Pseudocrocodillicola 331 45 17 georgiana Polycotyle ornata 8 5 6 Pseudocrocodillicola species 313 15 64 Appendix 2-Listed P-values are those found indicating significant differences in intraspecific prevalence of trematode and nematode species in Alligator mississippiensis across host locations. Texas alligators were collected in 2012 and the Florida, Louisiana West Zone (LAW), and Louisiana East Zone (LAE) alligators were collected in 2011. Host Location Species P-value Texas Acanthostomum diplorum 0.001 Acanthostomum species 0.01 Acanthostomum scyphocephalum 0.001 Florida Dujardinascaris waltoni 0.001 Ortleppascaris antipini 0.05 LAW Acanthostomum pavidum 0.001 Proctocaecum species 0.001 Pseudocrocodillicola americanense 0.001 Polycotyle ornata 0.05 Pseudocrocodillicola species 0.01 LAE Cryptogonomidae 0.001 Proctocaecum species 0.001 Pseudocrocodillicola americanense 0.001 Archaeodiplostomum acetubulata 0.05 Timoniella loosi 0.01 Pseudocrocodillicola georgiana 0.001
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|Author:||Sung, Helen; Tellez, Marisa|
|Date:||Dec 1, 2016|
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