Definition of protostome in English:

protostome

noun

Zoology
  • A multicellular organism whose mouth develops from a primary embryonic opening, such as an annelid, mollusc, or arthropod.

    • ‘Once this had appeared, the protostomes could develop.’
    • ‘These animals are all protostomes - the mouth develops before the anus in the young embryo - and they have long been recognized as belonging together as a group.’
    • ‘In the complementary category, the protostomes, which includes annelids and arthropods, the blastopore develops into the mouth.’
    • ‘Arthropods are bilaterally symmetrical protostomes with strongly segmented bodies.’
    • ‘If the ancestor of protostomes displayed a segmentation comparable to annelids and arthropods, this necessarily means that segmentation was lost independently in different protostome lineages.’

Origin

1950s: from proto- ‘primitive’ + Greek stoma mouth.

Pronunciation:

protostome

/ˈprəʊtə(ʊ)stəʊm/