TY - JOUR
T1 - Unraveling a 70-year-old taxonomic puzzle
T2 - Redefining the genus ikedosoma (Annelida: Echiura) on the basis of morphological and molecular analyses
AU - Tanaka, Masaatsu
AU - Kon, Takeshi
AU - Nishikawa, Teruaki
N1 - Publisher Copyright:
© 2014 Zoological Society of Japan.
PY - 2014/12/1
Y1 - 2014/12/1
N2 - After a long-standing taxonomic confusion, the echiurid genus Ikedosoma Bock, 1942, endemic to Japan and surroundings, is redefined on the basis of morphological and molecular analyses of many new Japanese materials and some museum specimens. The re-examination of a syntype of I. elegans (Ikeda, 1904), the type species of the genus, first revealed that its oblique muscle layer is continuous throughout and never fasciculate between longitudinal muscle bands, unlike those described in the definitions that have prevailed for ca. 70 years, making this genus indistinguishable from Listriolobus Spengel, 1912. Two Japanese species of Ikedosoma, I. elegans and I. gogoshimense (Ikeda, 1904), which were thus redefined, had also been poorly defined in the past to the point of being nearly indistinguishable from each other, largely due to incomplete descriptions and poor collections. Molecular phylogenetic analyses using 18S and 28S ribosomal RNA, histone H3, and cytochrome c oxidase subunit I (COI) genes clearly confirmed the distinction between these two species, their monophyletic origin, and their distinction from L. sorbillans (Lampert, 1883). The genus Ikedosoma thus validated is morphologically distinguishable from Listriolobus by the absence of a rectal caecum. Ikedosoma elegans and I. gogoshimense also differ in the disposition of gonoduct pairs. The third known species, I. qingdaoense Li, Wang and Zhou, 1994, from Qingdao, North China, lacks information on oblique muscle layers, which makes even its generic affiliation uncertain.
AB - After a long-standing taxonomic confusion, the echiurid genus Ikedosoma Bock, 1942, endemic to Japan and surroundings, is redefined on the basis of morphological and molecular analyses of many new Japanese materials and some museum specimens. The re-examination of a syntype of I. elegans (Ikeda, 1904), the type species of the genus, first revealed that its oblique muscle layer is continuous throughout and never fasciculate between longitudinal muscle bands, unlike those described in the definitions that have prevailed for ca. 70 years, making this genus indistinguishable from Listriolobus Spengel, 1912. Two Japanese species of Ikedosoma, I. elegans and I. gogoshimense (Ikeda, 1904), which were thus redefined, had also been poorly defined in the past to the point of being nearly indistinguishable from each other, largely due to incomplete descriptions and poor collections. Molecular phylogenetic analyses using 18S and 28S ribosomal RNA, histone H3, and cytochrome c oxidase subunit I (COI) genes clearly confirmed the distinction between these two species, their monophyletic origin, and their distinction from L. sorbillans (Lampert, 1883). The genus Ikedosoma thus validated is morphologically distinguishable from Listriolobus by the absence of a rectal caecum. Ikedosoma elegans and I. gogoshimense also differ in the disposition of gonoduct pairs. The third known species, I. qingdaoense Li, Wang and Zhou, 1994, from Qingdao, North China, lacks information on oblique muscle layers, which makes even its generic affiliation uncertain.
KW - Annelida
KW - Echiura
KW - Echiuridae
KW - Ikedosoma
KW - Thalassematinae
KW - molecular phylogeny
KW - revision
KW - taxonomy
UR - http://www.scopus.com/inward/record.url?scp=84918569869&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84918569869&partnerID=8YFLogxK
U2 - 10.2108/zs140155
DO - 10.2108/zs140155
M3 - Article
C2 - 25483798
AN - SCOPUS:84918569869
VL - 31
SP - 849
EP - 861
JO - Zoological Science
JF - Zoological Science
SN - 0289-0003
IS - 12
ER -