Redescription of Bassozetus compressus (Günther 1878), a senior synonym of Bassozetus elongatus Smith and Radcliffe 1913 (Ophidiiformes: Ophidiidae)

Abstract

Re-examination of two deep-sea ophidiid species, Bassozetus compressus (Günther 1878) and Bassozetus elongatus Smith and Radcliffe in Radcliffe 1913, based on specimens from the West Pacific, Atlantic and Indian Oceans, disclosed no morphologically significant differences amongst those from the West Pacific, including the lectotype of B. compressus and holotype of B. elongatus. Two characters considered to distinguish between the species [pelvic-fin length to standard length (SL) ratio and position of a small process on the sagittal otolith] were found to be invalid, leading to the conclusion that B. compressus is a senior synonym of B. elongatus. The remaining specimens from the Atlantic and Indian Oceans, previously reported as B. compressus or B. elongatus, represented one or more as-yet undescribed species. A detailed redescription of B. compressus is provided on the basis of the West Pacific specimens, the species being distinguishable from all other congeners by the following combination of characters: dorsal-fin rays 118-127; pectoral-fin rays 22-26; oblique scales ca. 18-20; vertebrae 11-13 ? 54-58 = 66-69; distance between base of pelvic fin to origin of anal fin 15.8-20.5 % SL; eye diameter 2.0-2.7 times in snout length; a median basibranchial tooth patch; anterior margin of sagittal otolith with a small process, dorsal margin smooth. Two specimens of B. compressus, collected from off Uotsurijima Island, Senkaku Islands and Kumejima Island, Okinawa Islands, represent the first record of this species from Japanese waters.

First Record of the Rare Deepwater Assfish <i>Bassozetus mozambiquensis</i> (Ophidiiformes: Ophidiidae) from the Western South Atlantic

“…30), 63 total vertebrae (vs. 65) and short pelvic-fin, 9.0% SL (vs. 9.5%) (Table 1). The differences in other counts and measurements between the present specimen and B. mozambiquensis (within three and 2.6 points, respectively) are minor, and regarded here as intraspecific variations due to similar ranges existing in other species of Bassozetus (see Nielsen and Merrett 2000;Tomiyama et al 2015Tomiyama et al , 2018Tomiyama et al , 2021. There being no other signifi- (Tomiyama et al 2018(Tomiyama et al , 2021.…”

“…Eye diameter and number of oblique scale (missing during or after collection) rows between the anus and dorsal-fin base followed Nielsen and Merrett (2000) and Tomiyama et al (2018). Preanus, prepelvic, preanal and tail lengths and distance between the pelvic and anal fins followed Tomiyama et al (2015Tomiyama et al ( , 2021, other counts and measurements following Hubbs and Lagler (1958). Vertebral counts were based on radiographs.…”

“…Almost all counts and measurements of B. levistomatus overlap those of B. mozambiquensis, but the latter has 14 or 15 long gill rakers (vs. 9-11 in the former) and a single well-developed basibranchial tooth patch (vs. absent) (Nielsen and Merrett, 2000;Tomiyama et al, 2021). Although B. compressus and B. robustus have been previously recorded from the Atlantic Ocean by several authors (e.g., Nielsen and Merrett 2000), their authentic distributional range were recently revised, being limited to the western Pacific Ocean (Tomiyama et al 2015(Tomiyama et al , 2021.…”

“…The deep-sea ophidiid genus Bassozetus Gill, 1883 currently comprises 16 valid species, excluding Bassozetus elongatus Smith and Radcliffe in Radcliffe, 1913, which has been synonymized under Bassozetus compressus (Günther, 1878) (Nielsen and Merrett 2000;Tomiyama et al 2015Tomiyama et al , 2018Tomiyama et al , 2021. Species of the genus are mainly benthopelagic, inhabiting depths of ca.…”

“…1000-5500 m in tropical to subarctic waters worldwide, although Bassozetus zenkevitchi Rass, 1955 is usually collected from the water column shallower than ca. 2000 m, an indication of its pelagic life style (Nielsen et al 1999;Nielsen and Merrett 2000;Tomiyama et al 2015Tomiyama et al , 2018Tomiyama et al , 2021.…”