Redescription of the circumglobal deepwater scorpionfish Setarches guentheri (Setarchidae)

Abstract

Setarches guentheri Johnson 1862 and Setarches longimanus (Alcock 1894) are similar to each other in sharing III, 4–6 (usually 5) anal-fin rays, a moderately deep body (29.8–42.9% of standard length; SL), three sharp spines on the lacrimal, scales absent on the lower jaw, and a fresh body color ranging from dusky-red to scarlet, S. guentheri having been considered distinguishable from the latter due to a well-developed second preopercular spine (absent or reduced in S. longimanus). Newly recognized diagnostic features of S. guentheri include the number of predorsal scales, exposed thoracic and abdominal scales, and number of ventral and caudal vertebrae. Morphological characters, including ontogenetic changes and intraspecific variation, of S. guentheri are described in detail, based on non-type specimens and all available type specimens of nominal species of S. guentheri. The distribution of S. guentheri, including a range extension to the Nazca Ridge, eastern Pacific, is also reviewed, based on previous records and examined specimens. The remarkable low genetic divergence and undefined geographical isolation in S. guentheri between the Indo-Pacific and Atlantic oceans were supported by comparison of 591 bp of the COI gene sequences from 39 and 4 specimens of S. guentheri and S. longimanus, respectively.