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Keywords:

  • Diplostomatidae;
  • endangered species;
  • life history;
  • parasite;
  • translocation

Summary

  • 1
    We used field and experimental data to test if white grub parasites (Diplostomatidae) are costly to White Sands pupfish (Cyprinodon tularosa), a threatened species restricted to four sites in the Chihuahuan desert, New Mexico.
  • 2
    Of the four populations of C. tularosa, two are native and two are introduced. The two native populations (Malpais Spring and Salt Creek) are genetically distinct and have been isolated historically in dissimilar aquatic habitats (brackish spring and saline river, respectively). Two populations were established c. 1970 from translocation of Salt Creek fish to another saline river (Lost River) and another brackish spring (Mound Spring).
  • 3
    Physid snails (Physidae) occur in the two brackish spring habitats but not the saline river habitats. These snails are first intermediate hosts for white grubs (Diplostomatidae). Therefore, the two freshwater populations are infected by diplostomatids. For the Mound Spring population, the ecological relationship of C. tularosa and diplostomatids has only recently occurred.
  • 4
    In 1995, a population crash occurred for C. tularosa at Mound Spring, associated with a parasite outbreak. Diplostomatids were the presumptive cause of this crash, but this was inferred from observation of infection in collected fish.
  • 5
    Two years of seasonal sampling of the two populations revealed that all collected fish were infected. Parasite intensities were significantly lower in winter compared to summer, suggesting that heavily infected fish were lost from the population on a seasonal basis.
  • 6
    We conducted an artificial infection experiment to assess the costs of parasitism for previously uninfected C. tularosa females for various life-history traits. Under experimental conditions, diplostomatid infection caused increases in C. tularosa mortality and decreases in growth and fat storage. Individual-level costs of parasitism may translate to population-level patterns of parasitism for C. tularosa populations. Results from this study suggest that parasites may impact host overwinter survival, which is consistent with lower parasite intensities found during winters in wild populations.