OligochaetaLeechesSpores, ProtozoanProtozoan Infections, AnimalEukaryotaAnnelidaHirudo medicinalisRNA, Ribosomal, 18SGeologic SedimentsAquacultureFish DiseasesFresh WaterSporesVideotape RecordingLeechingPhylogenyEcosystemMolecular Sequence DataIsopodaGanglia, InvertebrateLocomotionGangliaCarbon CycleFossilsAtmosphereBase SequenceTreesBiodiversityGastropodaMeteoroidsBiological EvolutionEarth (Planet)PaleontologyDinosaursSoilGeologyInvertebrate HormonesSwimmingEvolution, PlanetaryExtinction, BiologicalNitrogen CycleExtraterrestrial EnvironmentAquatic Organisms