Definition of triclad in US English:



  • A free-living flatworm of an order characterized by having a gut with three branches, including the planarians.

    Order Tricladida, class Turbellaria

    • ‘In fact, there are only two authenticated cases of passive dispersal in freshwater triclads.’
    • ‘The KKEE motif shared between Convoluta and the triclads either is due to convergence or is an artefact of imposed positional homology in the alignment of Berney, Pawloski, and Zaninetti.’
    • ‘The amplified fragment of EF1a varies in size, from 947 nt in the two polyclads to 962 nt in C. roscoffensis to 965 nt in the three triclads.’
    • ‘We have searched for Hox and ParaHox genes in several flatworm groups spanning from freshwater triclads to marine polyclads and, more recently, in the acoels, the likely earliest extant bilaterian.’
    • ‘Despite several attempts, no ParaHox genes have so far been found in triclads.’
    • ‘We have isolated and sequenced eight Hox genes from the freshwater triclad Girardia tigrina and three Hox and two ParaHox genes from the polyclad Discocelis tigrina.’


Late 19th century: from modern Latin Tricladida, from tri- ‘three’ + Greek klados ‘branch’.