Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 1/1/2002
Publication Date: 4/17/2002
Citation: Shappell, N.W., Garber, E., Gackle, N.J., Canfield, J., Larsen, G.L. 2002. Malformation versus mortality, a study of northern leopard frog development in situ. [abstract]. Minnesota Water 2002 Conference, April 17-20, 2002, St. Cloud, MN. Interpretive Summary:
Technical Abstract: Field studies were designed to compare the relative incidence of mortality and malformation of developing northern leopard frogs (NLF, Rana pipiens) at two Minnesota (MN) Lake sites. Selection was based on survey data, a high incidence of malformations at one site (CWBN) versus low incidence at second site (BUT) and similar topographical characteristics. Tadpoles (stage 25) were collected from a pond in North Dakota (ND) with no history of malformations and placed at the sites. After two weeks, significant mortality began to occur at both sites; by 4 weeks ranged from 37% to 85% across MN sites; 0% was exhibited by larvae in the laboratory. Coincubation of larvae from MN sites with healthy larvae indicated mortality was due to a biologically transmissible factor at the BUT site. No larvae surviving to metamorphosis exhibited malformations with the exception of scoliosis, which was equal for all larvae, field- or lab- raised. Water from ND, BUT, ,and CWBN were analyzed using the Frog Embryo Teratogenesis Assay-Xenopus (FETAX). MN waters caused severe developmental delay and 25% reduction in larval length, while ND water was without adverse effect. Concommitant field surveys found three species of tadpoles / metamorphs to be diseased and metamorphs of the two species that over-winter as larvae exhibited malformations at CWBN. Later surveys found no Rana pipiens larvae at CWBN. No NLF adults were found at BUT, while metamorphs from overwintering species were normal. The lack of malformations found in enclosure-raised Rana pipiens may be due to reduced accessibility of larvae to ribeiroia shed from snails. Whatever potential for malformation exists at these sites, issues of mortality are of greater significance in the NLF. FETAX prescreening of potential field sites may aid in evaluating future "clean"