Abstract
The aegid isopod Aegiochus spongiophila (Semper, 1867) was recorded from Japanese waters for the first time. The specimens were collected from off Makurazaki, southern Kyushu, Japan, mainly inhabiting the cavity of the hexactinellid sponge Euplectella oweni Herklots & Marshall, 1868. One specimen of A. spongiophila was found in the gill cavity of the sea toad Chaunax abei Le Danois, 1978. Aegiochus spongiophila is characterized by 1) long antenna, reaching the posterior margin of pereonite 6, 2) pentagonal frontal lamina, 1.2 times as long as width, 3) inferodistal lobes produced on the carpus of pereopods 2 and 3, 4) long appendix masculina, 1.7 times as long as endopod of pleopod 2, 5) uropodal exopod narrower, 2.6 times as long as width, mesial and distal lateral margins with 6-8 and 10-12 robust setae, respectively, 6) produced caudomedial point, with 15-17 robust setae on the posterior margin of pleotelson.
