Study of helminth parasites of amphibians by scanning electron microscopy

Abstract

Amphibians, like all other animals, are subject to a variety of parasites and diseases, including viral, bacterial and fungal infections as well as some forms of cancer and tuberculosis (Hoff et al., 1984). Various viruses and bacteria such as Pseudomonas or Salmonella, and fungi such as Candida, are recorded as common infectious agents in amphibians, but currently the focus of studies are the fungi of genus Batrachochytrium, agents of the disease known as chytridiomycosis, which is considered as one of the factors responsible for the decline of amphibian populations in many parts of the world (Berger and Speare, 1998). In addition, protozoans of the genera Opalina and Entamoeba in the digestive tract, and trypanosomes in the circulatory system, as well as coccidian protozoa have been recorded in amphibians (Duellman and Trueb, 1986; Duszynski et al., 2007). However, helminths are the most common invertebrate parasites of amphibians. One well known example among trematodes is the monogenean genus Polystoma, which infects the urinary bladder of adult amphibians around the world. Parasitic digenean trematodes include both larval stages (metacercariae) and adults. Cestodes are not common parasites in the gastrointestinal tract of amphibians, but when present may persist for a long time. Adult acanthocephalans adhere to the mucosa of the stomach or intestine. Finally, nematodes are particularly abundant in the digestive tract, lungs and blood vessels of these vertebrates (Pough et al., 2001). Amphibians are also hosts to other groups of less common parasitic invertebrates, such as annelids, pentastomids and arthropods (copepods, ticks, insects) (Tinsley, 1995)