OligochaetaLeechesAnnelidaSpores, ProtozoanProtozoan Infections, AnimalEukaryotaHirudo medicinalisRNA, Ribosomal, 18SGeologic SedimentsAquacultureFish DiseasesSporesVideotape RecordingPhylogenyFresh WaterInvertebratesLeechingMolecular Sequence DataHemerythrinErythrocruorinsPlatyhelminthsBase SequenceEchinodermataBiological EvolutionArthropodsMolluscaGangliaGanglia, InvertebrateBody PatterningEvolution, MolecularNervous SystemHemoglobinsAmino Acid SequenceLarvaEmbryo, NonmammalianReproduction, AsexualVertebratesInvertebrate HormonesSequence Alignment