Ontogenetic development of a rare liparid, Paraliparis dipterus, collected from Suruga Bay, Japan, with notes on its reproduction

Adult liparid specimens [17.2-47.2 mm standard length (SL)], together with larvae and juveniles (5.6-16.5 mm SL), collected from near-bottom depths of 174-802 m in inner Suruga Bay, southern Japan, were identified as Paraliparis dipterus, previously known only from the holotype. Descriptions of the ontogenetic development of the species, together with their gut contents, are provided, along with notes on ovarian eggs. The present species can be easily distinguished from nine other Japanese species of Paraliparis by the combination of 54-58 dorsal-fin rays, 48-54 anal-fin rays and 6 caudal-fin rays. Ontogeny is characterized by the acquisition of general adult characters by the flexion stage (e.g., fin ray numbers, except pectoral fin, and most body proportions) and indistinct transformation thereafter, with some characters changing gradually throughout the juvenile to adult stages (e.g., elongating upper and lower pectoral-fin rays), as in other known species of Paraliparis. Radiolaria, Harpacticoida and other copepods dominated the gut contents. The months when both yolk-sac larvae and adults possessing "developed" ovarian eggs (≥0.9 mm in diameter) were collected indicated that P. dipterus spawns year-round.[PUBLICATION ABSTRACT]