• wallacejnichols
• May 13, 2005
• • Publications

Wallace J. Nichols and Susan C. Gardner

Summary

Since 2001 we have conducted sea turtle monitoring at six in-water sites along the Baja California peninsula. The goal of this project has been to train and involve local communities in the stewardship of their resources and in the protection of endangered species. In August 2002 the US Fish and Wildlife Service and National Marine Fisheries Service sponsored a health assessment workshop to introduce monitoring teams to a variety of measures used to describe sea turtle health. The result of this workshop has been collaboration between monitoring teams and researchers at CIBNOR, La Paz. The first phase of collaborations have now produced results of health assessment in sea turtles, in particular the black turtle. The results provide the start of needed baseline levels and suggest areas where more research is warranted. Further health assessment work will continue as collaboration between WiLDCOAST, Grupo Tortuguero de las Californias, CIBNOR and Wildlfe Trust.

Toxicology

Worldwide declines of sea turtle populations have been attributed in part to environmental contaminants and contaminant-related diseases ( e.g. fibropapillomatosis). However, very little information useful to management is available for baseline levels of contaminants and effects on sea turtle populations. Organochlorine residues were measured in 3 species of sea turtles from the Baja California peninsula, Mexico (Gardner et al. 2003). Seventeen of 21 organochlorine pesticides analyzed were detected, with heptachlor epoxide and g- hexachlorocyclohexane the most prevalent [14 (40%) and 11 (31%) of the 35 tissue samples, respectively]. PCBs were detected in all but one of the 9 turtles studied, with congener 18 as the most commonly detected [8 (23%) of the samples]. The dioxin-like congeners 118 and 180 were detected in 4 (11%) and 3 (9%) of the samples, respectively . Percent contribution of congeners was negatively correlated to their octanol-water partition coefficients, with kidney and muscle containing more lower-chlorinated congeners than liver or adipose samples. Levels of organochlorines detected in the present study were low, potentially attributable to the feeding habits of the predominant species collected in this study (herbivorous) and/or the samples obtained in an unindustrialized region. While there were an insufficient number of samples to assess differences among species, qualitative evaluation indicates the potential effects of dietary differences among the herbivorous green turtles and the carnivorous olive ridley. This is an area that requires further investigation.

Physiological Condition:

Biomarkers of oxidative stress have been used successfully as indicators of contaminant exposure in a variety of species; however, a basic understanding of oxidative processes in sea turtles is lacking. Recent studies conducted on black turtles Chelonia mydas agassizii from Baja California (Valdivia, 2003) demonstrate that O 2 .- production in kidney and heart was lower than in liver, lung and muscle; however, there were no statistically significant differences in the level of lipid peroxidation among tissues. Generally, liver presented the highest levels of O 2 .- and lipid peroxidation, perhaps due to elevated xenobiotic metabolism in this tissue. It is possible that the antioxidant system could buffer against oxidative damage in sea turtle tissues, especially in those presenting higher O 2 .- production. The results suggest that further study of antioxidant systems in sea turtles and the potential use of oxidative metabolism as a biomarker in population health assessments is warranted.

Parasitology

Spirorchiid trematode infections occur frequently in sea turtles, with reports of up to 85% of examined turtles infected by eggs or adult trematodes. The life cycle of marine spirorchiids is not well known; adult forms are frequently located in heart chambers, while the eggs (with similar form and size for different genera) can be located in blood vessels of any organ. Learedius learedi Price, 1934 was re-described from specimens obtained from the heart of the black turtle Chelonia mydas agassizii found in Magdalena Bay, Baja California Sur, Mexico (Inohuye-Rivera et al. 2004). The re-description is consistent with the original, but provides an unreported range of variation in testes shape and position; adding new information about the reproductive systems. From the four hearts examined, only one was free of parasites. A total of 128 parasites were found, leaving a mean intensity of 43 parasites per infected heart. This is the first record of occurrence of Learedius learedi in C. m.agassizii in Mexico, expanding the known range of the parasite to the Baja California Peninsula (Inohuye-Rivera et al. 2004).

Black turtle carcasses, recovered as a result of incidental capture in Magdalena Bay, Mexico, revealed invasion by spirorchiid trematode eggs in liver, kidney, intestines, muscle, heart, pancreas and duodenum (Cordero-Tapia et al. in press). Most of the organs showed a mild or absent inflammatory response in histological sections, with the exception of a pancreatic-duodenal section that revealed severe lymphocyte and phagocyte infiltration associated with an infestation of more than 200 eggs. A linear formation of 35 eggs from the pancreas toward the intestinal lumen is described as resembling migration (Cordero-Tapia et al. in press).

Infection by trematodes has been associated with several diseases and suspected as the cause of death in stranded sea turtles. In Hawaii, reports that 94% of the sea turtles with clinic manifestation of fibropapillomatosis contained trematodes eggs raised the question of whether there might be an association between spirorchiid infection and this disease (Aguirre et al., 1998). However, the high prevalence of Learedius learedi infection in Mexican turtles, and absence of any clinic evidence of fibropapillomatosis in the black turtle population in Mexico, argues against the hypothesis that such an association exists. This finding agrees with others (Graczyk et al.,1995), who reported that 85% of the Hawaiian turtles with fibropapilloma were negative to spirorchiids.

Virology

Infectious diseases produced by virulent agents are common in most reptile species, however they represent a greater threat when encountered in species that are endangered or threatened with extinction. Herpesvirus similar to the human Herpesvirus simplex 1 and 2, has been associated as etiologic agents of fibropapillomatosis in sea turtles. This disease has affected to diverse green turtles populations ( Chelonia mydas ) in epidemic proportions, and to a lesser degree, olive ridley turtles ( Lepidochelys olivacea ) and loggerhead turtles ( Caretta caretta ) at global level. In order to evaluate the presence of Herpesvirus associated to the fibropapillomatosis, as well as Herpesvirus causing Lung-Eye-Trachea disease and Grey Patch disease in marine turtles from Baja California, samples of tissues and organs of the Eastern Pacific green turtles ( Chelonia mydas agassizii ), olive ridley turtles and loggerhead turtles from four areas located throughout the Baja California peninsula were analyzed (Castelán Martínez, 2004). Herpesvirus was detected using sequential nested concensus-primer PCR to amplify an internal region of the Herpesvirus DNA polymerase gene. Herpesviral presence was detected in three black turtles collected from Magdalena Bay. The sequences obtained were compared with other herpesviral sequences released to GENBANK by using the Local Basic Alignment Search Tool (BLAST) of the National Center for the Biotechnological Information, finding 75% of similarities with bovine Herpesvirus 2. This represents the first reported Herpesvirus in black turtles from the Baja California peninsula (Castelán Martínez, 2004). The results obtained send to the conclusion that the black turtles are not threatened by Herpesvirus associated with the mentioned pathologies. Although,the two other species were negative to the herpesviral detection test, since sample sizes were low, (n=5 loggerhead and n= 10 olive ridley) more extensive analysis is warrented in order to determine if these populations have been affected by fibropapillomatosis.