Geology topics

S. P. Hansen

Publications and source records attributed to S. P. Hansen.

3 recordsLinked to original sources

USGS2007

Evidence of experimental postcyclic transmission of Bothriocephalus acheilognathi in bonytail chub (Gila elegans)

We examined the role that predation of infected conspecific fish and postcyclic transmission might play in the life cycle of the Asian fish tapeworm, Bothriocephalus acheilognathi (Cestoda: Pseudophyllidea) Yamaguti, 1934. Young-of-the-year (YOY) bonytail chub ( Gila elegans ) were exposed to copepods infected with B. acheilognathi and subsequently fed to subadult bonytail chub. Within 1 wk after consumption of the YOY chub, subadults were necropsied and found infected with gravid and nongravid tapeworms. This study provides evidence that postcyclic transfer of B. acheilognathi can occur. Postcyclic transmission may be an important life history trait of B. acheilognathi that merits consideration when studying the impact and distribution of this invasive and potentially pathogenic tapeworm.

New Mexico↗

USGS2006

Experimental infection of the endangered bonytail chub (Gila elegans) with the Asian fish tapeworm (Bothriocephalus acheilognathi): impacts on survival, growth, and condition

Bothriocephalus acheilognathi Yamaguti, 1934, a tapeworm known to be pathogenic to some fish species, has become established in the endangered humpback chub (Gila cypha Miller, 1964) in Grand Canyon, USA, following the tapeworm’s introduction into the Colorado River system. The potential impact of this tapeworm on humpback chub was studied by exposing the closely related bonytail chub (Gila elegans Baird and Girard, 1853) to the parasite under a range of conditions that included potential stressors of humpback chub in their natal waters, such as abrupt temperature change and a limited food base. Survival of infected fish under low food rations was considerably lower than that of control fish, and mortality of infected fish began 20 days earlier. Growth of infected fish was significantly reduced, and negative changes in health condition indices were found. No significant negative impacts were revealed from the synergistic effects between temperature shock and infection. Bothriocephalus acheilognathi does present a potential threat to humpback chub in Grand Canyon and should be considered, along with conventional concerns involving altered flow regimes and predation, when management decisions are made concerning conservation of this endangered species.

Arizona↗

USGS2004

Intestinal helminths in mourning doves (Zenaida macroura) from Arizona, Pennsylvania, South Carolina, and Tennessee, U.S.A.

We examined 115 hunter-killed mourning doves ( Zenaida macroura ) from 4 states (Arizona, Pennsylvania, South Carolina, and Tennessee, U.S.A.) in 1998 and 1999 to investigate geographical variation in the prevalence and intensity of intestinal helminth infections. Four intestinal helminth species were identified: Killigrewia delafondi , Ornithostrongylus crami , Ascaridia columbae , and Capillaria obsignata . The number of worms (all helminth species combined) per infected bird ranged from 1 to 166 (mean ± SE = 12.7 ± 7.45, median = 2.0). Filarids, Aproctella stoddardi , were found in 2 birds but were probably adhering to the outside of the intestine. Overall, 18% of the doves were infected with 1 or more species of helminths. The percentage of doves infected with at least 1 helminth species varied from 4% in Arizona to 27% in South Carolina. Mixed infections occurred in only 3 individuals (14% of infected birds). We found no significant differences in prevalence of infection among any of the 4 helminths by host age or sex, and prevalences were too low to test for differences among states. The intensity of O. crami was higher in males than in females but did not differ significantly among states. Intensities of the other 3 helminths did not differ by sex or state, and we found no differences in helminth intensity by age. Intestinal length was significantly greater in infected than in uninfected birds.

Arizona, Pennsylvania, South Carolina, Tennessee↗