<i>Tregouboviopsis gemmula</i>, a new species of Hydrozoa (Anthoathecata, Ptilocodiidae), with new record of <i>Tregouboviopsis perradialis</i> from Japan

Unidentified hydromedusae were collected from Nagasaki and Okinawa prefectures in western Japan. In the present study, taxonomic investigations, including morphological observations, of the unidentified specimens were conducted. The specimens collected from Okinawa had the following morphological characteristics: umbrella spherical; without tentacles; umbrella margin with nematocyst ring from which centripetal, flat, nematocyst-containing bands run meridionally on exumbrella from umbrella margin to umbrella apex; manubrium large, cruciform base, the four perradial corners of mouth margin without oral tentacles; gonads perradial on manubrium wall. Based on these findings, we describe it as a new species, Tregouboviopsis gemmula. Additionally, we performed a detailed morphological examination of the species Tregouboviopsis perradialis. To date, this species has only been reported from the central and northern regions of the South China Sea. This study provides additional information on the morphology and ecology of these two species of Ptilocodiidae, which constitute two new records for Japanese waters.