Decline of Some West-Central Florida Anuran Populations in Response to Habitat Degradation

Recent reports have suggested that a global decline in amphibian populations has taken place during the past few decades. Urban development is thought to affect the richness and abundances of species and, therefore, could be an important cause of decline. We estimated the richness and abundances of anurans in wetlands at a residential development and in similar wetlands at a nearby undeveloped park. The residential development originally was pine flatwoods habitat, as is the undeveloped park curiently. We also compared the anuran species\u27 composition of the park in 1992 with the composition in 1974. Both richness and abundances of anurans in the residential development were different than those in the undeveloped park. Employing the same amount of sampling effort at both sites, we trapped or observed 11 species at the developement and 15 species at the park, and trapped 569 individuals at the development and 1224 individuals at the park. The anuran species richness at the undeveloped park in 1992 was nearly the same as in 1974; a single rare species apparently was not present in 1992. Of the 15 species present in both surveys, 14 showed higher abundances in 1992 than in 1974. We suggest that the current differences between the residential development and the park have resulted from degradation of both the uplands used by many species during the dry season and the temporary wetlands used by many species for reproduction. Four species especially sensitive to such degradation, Bufo quercicus, Scaphiopus h. holbrookii, Hyla femoralis, and H. gratiosa, were the species missing from the residential development. Not all species of anurans typical of pine flatwoods appeared to be affected adversely by development. Three species of ranids, Rana utricularia, R. grylio, and R. catesbeiana, were found in higher abundances at the residential development than at the park. These ranid species breed in a wide variety of aquatic systems, including the permanent bodies of water that are now abundant in the development, and probably use the uplands less than other anurans. If amphibian decline is international in scope, then the decline could be attributable either to global changes caused by humans, or to local, but widespread, environmental degradation, or to a combination of factors. While much recent popular focus has been on potential global causes of decline, we believe that this emphasis may have caused attention to be taken away from local causes that, as our study demonstrated, may be at least as important. We suggest that in many places, local environmental degradation is insidiously chipping away at amphibian diversity, and that more emphasis should be placed on these local causes than is now the case

Structural simplicity of the Zonula Occludens in the electrolyte secreting epithelium of the avian salt gland

The structure of the zonula occludens in the secretory epithelium of the salt gland of the domestic duck was determined by thin section and freeze-fracture electron microscopy. These glands secrete an effluent with a NaCl concentration four times that of plasma, and thus maintain a steep ionic gradient across their secretory epithelium. Freezefracture replicas from salt stressed ducks demonstrate that the zonula occludens is surprisingly shallow in depth (20–25 nm) and generally consists of two parallel junctional strands which are juxaposed along their entire length. In addition to the simplicity of the junction separating mucosal and serosal compartments, the ratio of junctional length to apical surface area is large since luminal surfaces of secretory cells are narrow and intermesh with one another. The zonula occludens in nonsecreting fresh water-adapted birds is similar to the salt stressed group except that two sets of double strand junctions are seen in addition to junctions consisting of a single set. Based on previous ultrastructural, cytochemical and physiological studies in salt glands and in other epithelia, a model for salt secretion was suggested in which intercellular space Na + , generated by basolateral ouabain-sensitive Na + pumps, reaches the lumen via a paracellular route (Ernst & Mills, 1977, J. Cell Biol. 75 :74). The simplicity of the morphological appearance of the zonula occludens in the salt gland, which resembles that described for several epithelia known to be leaky to ions, is consistent with this hypothesis.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/48028/1/232_2005_Article_BF01869292.pd