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We use as input one specific developmental stage ontology for each species, and we then merge all these species-specific developmental ontologies into one single multi-species ontology. To do that, we use broad developmental stages described in the Uberon ontology: either we map some of the species-specific stages to these Uberon broad developmental stages (i.e., equivalent classes), or we attach some of the species-specific stages as children of these Uberon developmental stages (i.e., subclasses).
You can find all 'source' species-specific ontologies we develop here. For C. elegans, we rely on the WBls ontology developed by WormBase (we also rely on external ontologies for fly, zebrafish, and xenopus).
In the ontology, developmental stages are ordered thanks to the use of the relations 'preceded_by' and 'immediately_preceded_by'.
An example of apparent non-standard nomenclature arises for C. elegans: a specific C. elegans developmental stage is mapped to a broad Uberon stage. For instance, several WBls stages are mapped to the same Uberon term 'UBERON:0000092' (post-embryonic stage): 'WBls:0000022' (postembryonic Ce), 'WBls:0000093' (Brugia postembryonic stage), 'WBls:0000103' (postembryonic nematode); these mappings are cross-references in the ontology file.
Similarly, some Uberon terms have no equivalent in WBls, as for instance 'UBERON:0007220' (late embryonic stage). In that case, we mapped the terms 'WBls:0000015' (elongating embryo Ce) and 'WBls:0000021' (fully-elongated embryo Ce) as children of 'UBERON:0007220'. As a result, the non-standard term (late embryonic stage) will show up in the nomenclature for C. elegans.