open access

https://hdl.handle.net/2115/60646

Descriptions of the copepodid stages of the mesopelagic copepod, Gaetanus variabilis (Brodsky, 1950) (Calanoida, Aetideidae) from the Japan Sea

英語

2005

Brill Academic Publishers

Crustaceana

78(7)

819-837

Based on specimens collected from the Japan Sea, all copepodid stages of the mesopelagic copepod, Gaetanus variabilis are described and illustrated. Among the family Aetideidae, the development of the body segmentation and of the segmentation of the swimming legs in G. variabilis is more similar to that in Gaetanus kruppii than to that in Aetideopsis armata, Chiridius gracilis, or Euchirella messinensis. A sharp, spine-like crest on the frontal dorsal surface of the cephalothorax is a characteristic feature of copepodid stages II-IV of G. variabilis. This frontal crest of G. variabilis, lost in copepodid stages V-VI, is considered as “convergent morphology”, relative to G. kruppii. Nucleotide sequences of the mitochondrial 16S rRNA gene confirmed that copepodid stages II and III with frontal crest and copepodid stage VI without frontal crest are the same species: Gaetanus variabilis. In the adult male, the mandible, maxillule, and maxilla degenerate, whence no feeding takes place: a phenomenon commonly seen in aetideid copepods.

学術雑誌論文

Accepted Manuscript

0011-216X

1568-5403

AA00139356