LeechesHagfishesLampreysPetromyzonFresh WaterJawReceptors, AntigenVertebratesHirudo medicinalisFishesPhylogenyBiological EvolutionSharksLeechingEvolution, MolecularMolecular Sequence DataGillsPalaemonidaeAmino Acid SequenceSeawaterFreshwater BiologyGangliaRiversGanglia, InvertebrateSnailsWater MicrobiologyPlanktonEcosystemInvertebrate HormonesFish DiseasesSalinityRNA, Ribosomal, 16SElasmobranchiiCatfishesSequence Analysis, DNASkates (Fish)DNA, RibosomalGeologic SedimentsTrematodaWater Pollutants, Chemical