A new species of <i>Acanthochondria</i> Oakley, 1930 (Copepoda: Cyclopoida: Chondracanthidae) from <i>Chlorophthalmus albatrossis</i> Jordan & Starks, 1904 (Actinopterygii: Chlorophthalmidae) off western Japan, with notes

The genus Acanthochondria has a global distribution and accommodates 54 valid species. Nineteen of those species have been reported from Japan. A new species of Acanthochondria parasitizing a deep-sea fish Chlorophthalmus albatrossis (Chlorophthalmidae), living at depths of 370 to 400 meters from the Bungo Channel, Japan, is described and illustrated. The new species, Acanthochondria toyoshiomaruae sp. nov., can be distinguished from its other 54 congeners by the following features: (1) short and stout body, 2.2 times as long as wide; (2) trunk stout, 0.9 times as long as wide (excluding the posterior process), 2.6 times wider than head; (3) cephalosome as long as wide; neck slightly narrower than head, as long as cephalosome; (4) funnel-shaped genito-abdomen and the abdomen gradually narrowing posteriorly, with dorsally curved apex; (5) egg strings multiseriate, cylindrical, highly coiled and longer than trunk. This is the first record of this genus from a chlorophthalmid host. A checklist of valid global species of Acanthochondria with hosts and distribution is also provided. Two species of Acanthochondria (A. bicornis and A. sagitta) are deviating from the generic diagnosis and Both of the species are regarded as Chondracanthidae incertae sedis.