New records of two tropical sea cucumbers, <i>Holothuria</i> (<i>Thymiosycia</i>) <i>impatiens</i> and <i>H.</i> (<i>Cystipus</i>) <i>inhabilis</i> (Echinodermata: Holothuriidae)

Two tropical sea cucumber species, Holothuria (Thymiosycia) impatiens and H. (Cystipus) inhabilis, collected from Kushimoto, Wakayama, are reported here for the first time from Japan’s Honshu Island, extending the geographical range of these species northward. Here we describe their external, internal and ossicle morphologies along with the phylogenetic position of the two species. We present DNA sequence data on three Japanese Holothuria species, H. (T.) impatiens, H. (C.) dura and H. (C.) inhabilis, including two from the Cystipus subgenus for the first time. Phylogenetic analysis was performed using two mitochondrial gene markers in combination with sequence data from other Holothuria species. Our phylogenetic tree showed (1) Japanese H. (T.) impatiens formed a monophyletic clade with specimens from other waters, and (2) the two Cystipus species were divided into polyphyletic positions topologically.