Desmodema lorum Rosenblatt & Butler 1977

Martin, Jennifer M. & Hilton, Eric J., 2021, A taxonomic review of the family Trachipteridae (Acanthomorpha: Lampridiformes), with an emphasis on taxa distributed in the western Pacific Ocean, Zootaxa 5039 (3), pp. 301-351 : 345-346

Desmodema lorum Rosenblatt & Butler 1977

Figure 29

Holotype. USNM 216726. 1098 mm SL. Trawled west of northern Baja California, at 400m fishing depth. ( Fig. 29 ).

Material Examined. HUMZ 186218 (986 mm SL, Pacific, Japan, off Miyagi); KPM-NI 0019326 (935 mm TL, Pacific, Japan); NSMT-P 57555 (430 mm SL, Pacific, western north Pacific); NSMT-P 58740 (404 mm SL, Pacific,

Japan, Honshu); NSMT-P 58741 (2 specimens, 765, 827 mm SL, Pacific, Japan, Honshu); USNM 216726 (Holotype, radiograph, 1098 mm SL, Pacific , eastern North Pacific , Mexico); USNM 164325 (4 specimens, 52.3–100.2 mm SL, Pacific , California, west of Santa Cruz, from Alepisaurus stomach) .

Diagnosis. Dorsal-fin rays 197–215; in juveniles first 5 or 6 more stout and elongate than more posterior rays; pectoral 1+ 11–14; pelvic absent in adults, 7–11 elongate rays in juveniles; caudal 4–7, typically 6. Snout length greater than eye diameter in adults, approximately equal in juveniles. Snout-vent length 3.0– 4.1 in SL in adults, 1.4–2.0 in juveniles. Vertebrae: 106–111 total, 21–25 precaudal. Numerous scale types (cycloid, ridged scales both with and without lateral spines) present in juveniles and adults.

Remarks. The caudal region is much more elongate in adult D. lorum with the SL of adult D. lorum comprised of approximately ¾ postanal length (vs. ⅔ postanal length in D. polystictum ). The height of the dorsal fin is proportionately greater in D. lorum than in D. polystictum of similar size ( Rosenblatt & Butler 1977: fig. 8). Additionally, the overall coloration after preservation of juvenile and adult D. lorum is darker than D. polystictum , particularly along the elongate caudal region. In addition to lateral-line scales, several scale types are present in D. lorum , although they are easily overlooked. The most obvious location is the ventral margin between the left and right pectoral girdles, where scales with 1–4 ridges, some possessing 1–5 lateral spines per ridge are present (NSMT 58740). There does not appear to be an ontogenetic or geographic trend regarding placement or morphology of scales based on the available specimens, however examination of more specimens is required.

Distribution. Known only from North Pacific Ocean, from 41° to 29° N in the western Pacific and from 36° to 22° N in the eastern Pacific. Specimens are primarily collected in midwater trawls, with collection depths ranging from depth bins of 0–80 m to 902–933 m, but adults are most commonly collected from 500– 700m.

Geographic variation. Fin-ray counts generally are greater than what has been previously reported for D. lorum , and those specimens with numbers corresponding to the higher end of the range were collected from the western Pacific Ocean. An adult specimen captured from 20–30 m depth off Sagami Bay (KPM NI-0019326, 935 mm SL), has seven caudal-fin rays and 30 total (1+14) pectoral-fin rays, a number previously unreported for the genus.

Figures

FIGURE 29. Desmodema lorum Rosenblatt & Butler 1977. Holotype; USNM 216726; 1098 mm SL.