日本初記録のイッテンカゴマトウダイ（新称）Cyttopsis cypho（マトウダイ目ベニマトウダイ科）とカゴマトウダイC. roseaとの形態比較

抄録

The parazenid genus Cyttopsis Gill, 1862 includes two valid species, C. rosea (Lowe, 1843), known from the Atlantic and Indo-west Pacific Oceans, and C. cypho (Fowler, 1934) restricted to the eastern Indian and western Pacific Oceans. Around Japan, the former species is common, whereas the latter has not been recorded to date. However, two Cyttopsis specimens [51.6 and 71.8 mm standard length (SL)] collected from Tosa Bay and Enshu-nada, Japan in 2008 and 2019, respectively, have been identified as C. cypho. In addition to previous means of distinguishing between the two species, a faint dark lateral spot posteriorly on the body (absent in C. rosea) and fewer lateral-line scales (55–64) in C. cypho (vs 73–82), the following additional diagnostic characters were found: interspace between spines on 4th and 5th abdominal scutes very narrow (C. cypho) vs. wide (C. rosea); orbit diameter 13.6–16.6% vs. 14.7–19.1% of SL; interorbital width 5.8–6.6% vs. 5.8–8.0% of SL; snout length 21.1–27.4% vs. 17.8–23.3% of SL; and mandible length 22.6–25.6% vs. 22.1–26.9% of SL. The two specimens, representing the first Japanese records of C. cypho (for which the new standard Japanese name “Ittenkagomatodai” is proposed), extend the northern range of the species from off northern Mindanao Island, Philippines (type locality).