Gills of 194 fountain darters Etheostoma fonticola collected from the Comal River in Texas from May 1997 through May 1998 were found to be parasitized with 8-1,524 metacercarial cysts of a heterophyid trematode tentatively identified as Centrocestus formosanus. The intensity of infection varied among three sites on the Comal River. In contrast, of 130 darters from the nearby San Marcos River that were examined, only 4 (3%) were infected, and these had 1-2 cysts per fish. Of 2,279 Melanoides tuberculata snails from the Comal River that were examined, 139 (6.1%) were infected with the trematode. Only 1 snail in 2,241 from the San Marcos River that were examined was infected. The presence of metacercariae in darters was associated with flared opercula, shortened or thickened gill filaments, epithelial hyperplasia, and engorged lamellae. The normal cartilage support of the filaments was distorted and displaced, leading to severe deformities of filament structure. Gill damage was severe and possibly life threatening for the darters with more than 800 cysts per fish (9% of examined fish). We suspect that fountain darter deaths were caused by the parasite in the Comal River during this study.

The red-rim melania Melanoides tuberculata, a subtropical and tropical snail, is a nonindigenous species that has become established and is spreading in the United States. Of concern is the potential of the red-rim melania to displace native snail populations and to transmit trematodes that cause serious problems. One of these, a fish gill trematode, Centrocestus formosanus, has negatively affected U.S. commercial and wild fish stocks, including some endangered species. The snail has an operculum that can protect it from desiccation and can remain viable for days on dry fisheries equipment. Thus, contaminated fisheries equipment is suspected as one of the ways the snail is being moved from place to place. A study was conducted to find chemical treatments that would kill 100% of the red-rim melania. Thirteen different chemicals and chemical combinations were evaluated at different concentrations and for various exposure periods. Roccal-D-Plus, Hydrothol 191, niclosamide, and Virkon showed promise in 24-h exposures at concentrations of 20 mg/L active ingredient (AI), 80 mg/L AI, 2 mg/L, and 1,600 mg/L AI, respectively. Additionally, Roccal-D-Plus killed all snails exposed to 2,000 mg/L for 1 h and to 600 mg/L for 16 h. Roccal-D-Plus has a history of use as a disinfectant for fishery equipment.

The red-rim melania Melanoides tuberculatus (family Thiaridae), a tropical, nonindigenous aquatic snail, has become established and is spreading in the United States. Concerns associated with the spread of this snail include its potential to displace native snail populations and to transmit trematodes. Of particular concern is the gill trematode Centrocestus formosanus now found in U.S. commercial and wild fish stocks. The snail survives year-round in subtropical ponds and constant-temperature spring runs in Florida and Texas and in geothermal waters of several western and midwestern states. Knowledge of the temperature tolerances of the snail will increase the ability to predict its potential range in North American waters and to control its spread. Under constant temperature conditions in the laboratory, all red-rim melania (15-25 mm shell height [SH]) were killed by exposure to 5ЊC for 1 d, 9ЊC for 2 d, 11ЊC for 8 d, and 13ЊC for 12 d. At 17ЊC and 32.5ЊC, about 10% of the snails died within 27 d, indicating the outer limits of the temperature range for the snail. Waters that attain temperatures less than 18ЊC or greater than 32ЊC will probably not support red-rim melania. All snails (10-20 mm SH) died within 10 h at 40ЊC and within 20 min at 45ЊC. At 50ЊC, all snails (Յ42 mm SH) succumbed within 2.5 min, and the smallest snails (1-4 mm SH) survived for less than 0.5 min. A 4-5-min exposure to 50ЊC or warmer water should kill all red-rim melania on dip nets and other fisheries equipment.

Dry, oligotrophic ecosystems are highly threatened in Europe due to massive changes in land use and eutrophication. The conservation of these xeric habitats has received much attention, whereas the ecotones between xeric habitats and other habitat types are often disregarded. One species which mainly inhabits the transition zone between pine forests and adjacent xeric habitats is the heath grasshopper, Chorthippus vagans. This species is endangered in large parts of Europe. One of the largest populations in northern Germany is found on a degraded inland dune near Hanover. This population is threatened by dense growth of deciduous trees and litter accumulation. We analyzed changes in the distribution of this population after the implementation of conservation measures (thinning out the forest and removal of leaf litter). Moreover, we examined dispersal distances of the species in order to assess its colonization potential. We also studied the microhabitat preferences of C. vagans to assess key factors influencing its local distribution. Our data show a substantial growth in population size, which might be a consequence of the conservation measures. New patches on the dune were colonized, promoting dispersal between the subpopulations. We propose that restoration of forest-dune ecotones should be considered more often in landscape planning and conservation management.

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