Hydrolagus melanophasma, James, Kelsey C., Ebert, David A., Long, Douglas J. & Didier, Dominique A., 2009

James, Kelsey C., Ebert, David A., Long, Douglas J. & Didier, Dominique A., 2009, A new species of chimaera, Hydrolagus melanophasma sp. nov. (Chondrichthyes: Chimaeriformes: Chimaeridae), from the eastern North Pacific, Zootaxa 2218, pp. 59-68 : 60-67

publication ID	https://doi.org/ 10.5281/zenodo.189992
DOI	https://doi.org/10.5281/zenodo.6222600
persistent identifier	https://treatment.plazi.org/id/0394E119-FFFF-FFEA-DFBF-1C13FE0EF67C
treatment provided by	Plazi
scientific name	Hydrolagus melanophasma
status	sp. nov.

Treatment

Hydrolagus melanophasma View in CoL sp. nov.

Eastern Pacific Black Ghostshark ( Fig. 1–4 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 ; Tables 1, 2)

Hydrolagus View in CoL sp.: Hubbs et al., 1979:5; Eschmeyer et al., 1983:59; Ebert, 2003:240 –241, Ill.; Love et al., 2005:2.

Holotype: SIO 77-211, adult male, 926 mm TL, 577 mm BDL; Punta Pescadera, Baja California, Mexico, (23°48’N 109°42’W), 30.5 m, 19 May 1977, collected by L. Levinson and K. Martin by hook and line.

Paratype: LACM 39805-1, adult male, 982 mm TL, 631 mm BDL; West of Ensenada, Mexico, in U.S. waters, 915 m, 20 January 1980, collected by Hal Rainwater aboard the boat Juanaloa.

Nontype Specimens: SIO 68-89 (4 specimens), 930–1200 mm TL, Northwest of Isla Angel de la Guarda, Mexico (29°42.0’N 113°56.7’W), 565–644 m, 18 January 1968, by otter trawl. SIO 65-435 (2 specimens), (30°53.2’N 118°4.7’W), 1155 m, 22 September 1965, by trap and setline. LACM 37753-1, (1 specimen), 900 mm TL, California, U.S.A. (32°26.5’N 119°45’W), 1400 m, September 1978, aboard the Califia.

Diagnosis. A species of the genus Hydrolagus based on the absence of an anal fin. Hydrolagus melanophasma sp. nov. is distinguished from other chimaeroids by a blunt snout with minimal sloping from the orbit to the snout tip, a large slightly curved dorsal fin spine (25.9 % BDL) extending beyond first dorsal fin apex, and a long second dorsal fin (77.3–81.1% BDL) of uniform height throughout. The pectoral fins are large, reaching beyond the pelvic fin insertion when laid flat, trifid claspers forked for 27–27.8% of the total clasper length and the preopercular and oral lateral line canals branch separately or together from the infraorbital canal. Coloration after preservation is a uniform black with no distinct mottling or markings.

Description. Morphometric measurements of the holotype and paratype are presented in Table 1; proportional measurements presented below are of the holotype followed by the paratype in parentheses. A medium to large bodied Hydrolagus with a blunt snout that slopes minimally from the orbit to snout tip; eyes moderate size, length 22.2% (26.0%) of head length. Snout-vent length is short, 60.1% BDL (56.9%), nearly equal to pelvic-caudal space, 57.9% BDL (60.1 %). Pectoral-pelvic space, 29.8% BDL (32.2%), is one-half snout-vent length. Skin firm and robust, not deciduous as in some Hydrolagus (Didier 2002, Didier 2008). Pectoral fins large, triangular, anterior margin 40.9% BDL (38.5%), extends to or beyond pelvic fin insertion when laid against the body. Anterior margin of pelvic fins straight, length about one-half of pectoral fin anterior margin, 21.0% BDL (19.5%); pelvic fin posterior margin convex.

H. melanophasma

Holotype (male) Paratype (male)

SIO 77-211 LACM 39805-1 Measurement % BDL % BDL H. melanophasma

Holotype (male) Paratype (male)

SIO 77-211 LACM 39805-1 Measurement % HDL % HDL HDL (mm) 170.0 158.0 ONC 8.2 8.8 LRC 3.8 4.1 LNC 26.0 28.0 IOA 14.9 16.1 OTM 30.6 32.9 OCL 11.1 11.9 STL 14.5 15.6 SPS 16.9 18.2

First dorsal fin preceded by prominent, slightly curved dorsal spine that is attached to the first dorsal fin for 82.8% (87.2%) of spine total length; dorsal fin spine long, 25.9 % BDL (25.9%), height greater than apex of first dorsal fin; posterior edge of spine serrated for last 6.8% (13.1%) of spine length; spine serrations very worn on each specimen. Dorsal spine and first dorsal fin overlap with second dorsal fin when laid flat. First dorsal fin triangular, base short 15.3 % BDL (13.9%), with concave posterior margin. Second dorsal fin long, uniform in height throughout, and its base length 81.1% BDL (77.3%). Depth of second dorsal fin, 4.0% BDL (4.1%), is greater than depth of dorsal lobe of caudal fin, 2.0% BDL (3.3%). There is no measurable separation between insertion of the second dorsal fin and the origin of the caudal fin dorsal lobe. Depth of dorsal and ventral caudal fin lobes is nearly equal. Ventral lobe of caudal fin extends 24.8% (27.0%) of its length beyond the insertion of the dorsal lobe of caudal fin. Anal fin lacking.

Trifid claspers present in mature males along with frontal tenaculum and prepelvic tenacula. Claspers forked for posterior most 27.0% (27.8%) of total clasper length and extend beyond distal edge of pelvic fins. Prepelvic tenacula are 25.1% (17.8%) of total clasper length with 3 or 4 denticles along the medial edge. Frontal tenaculum is 14.8% (14.3%) of HDL with indistinct rows of 35–38 pointed, needle-like denticles.

Lateral line canal measurements of the holotype and paratype are presented in Table 2. The head lateral line canals are open grooves with wide dilation on the snout. There is a distinct space on the holotype between the preopercular and oral canals where they branch separately from the infraorbital canal ( Fig 3 View FIGURE 3 A). The paratype exhibits preopercular and oral canals that share a short common branch from the infraorbital ( Fig 3 View FIGURE 3 B). The preopercular canal is discontinuous after it branches from the oral or infraorbital extending for 24.0% of HDL or less before breaking into consecutively smaller pieces. Trunk lateral line extends the length of the body from junction with post-orbital to whip-like filament and is generally straight with no regular undulations.

Color. Coloration in life as observed in situ by MBARI ROV footage appears uniform black with a lighter band over the snout slightly anterior to the midpoint between the eye and the snout tip ( Fig. 4 View FIGURE 4 ). After preservation specimens are uniform dark brown or purplish, including all paired and unpaired fins, with no distinct markings or mottling. Claspers are slightly lighter in color.

Etymology. The specific name is derived from melano - (Greek prefix) meaning black and – phasma (Greek noun) meaning specter or spirit. Vernacular: Eastern Pacific Black Ghostshark

Comparisons. Hydrolagus melanophasma is the fifth described species of Hydrolagus now known to occur in the eastern Pacific. Three species, Hydrolagus alphus , H. mccoskeri , and H. macrophthalmus , occur in the southeastern Pacific with the former two considered to be endemic to the Galapagos Islands ( Barnett et al. 2006, Quaranta et al. 2006). Hydrolagus alphus is distinct from H. melanophasma in coloration, being uniform brown with a distinct white spot above the pectoral fins, an explicit depressed middle region of the second dorsal fin, a larger eye length (9.5–10.2% BDL vs. 6.5 % BDL), a shorter second dorsal fin base length (66.3–70.5% BDL vs. 77.3–81.1% BDL), and a longer dorsal spine height (30.1–33.2% BDL vs. 25.9% BDL) ( Quaranta et al. 2006). Hydrolagus mccoskeri is also distinct from H. melanophasma in coloration, being medium brown dorsally with many irregular circular and elongate white blotches, an indented second dorsal fin, a longer snout-vent length (64–67% BDL vs. 56.9–60.1% BDL), a longer eye length (9–13% BDL vs. 6.5% BDL), and a longer pre-second dorsal fin length (54% BDL vs. 47.4–47.8% BDL) ( Barnett et al. 2006). Hydrolagus macrophthalmus is known only from off the coasts of Chile and Peru ( Quaranta et al. 2006). It is distinct from H. melanophasma in coloration, being uniform brown with no white markings, bluish fins, a second dorsal fin height that is higher at the anterior and posterior ends with a depressed mid-section, a shorter head length (18.6–22.2% BDL vs. 25–29.5% BDL), smaller pectoral fins with the anterior edge measuring 31.9–35.3% BDL (vs. 38.5–40.9% BDL), and a longer spine (26.3–31.1% BDL vs. 25.9% BDL) (K.L. Quaranta, Moss Landing Marine Laboratories, pers. comm.).

Hydrolagus colliei is the only Hydrolagus species, besides H. melanophasma , known to occur in the eastern North Pacific. The distribution of H. colliei is from southeastern Alaska to Baja California and the northern Gulf of California. Hydrolagus colliei is distinct from H. melanophasma in coloration, being uniformly dark brown to reddish-brown with numerous white spots on the head and trunk, a strongly indented second dorsal fin, a shorter second dorsal fin base length (57–72% BDL vs. 77.3–81.1% BDL), a longer distance from origin of the second dorsal fin to origin of pectoral fin (37–53% BDL vs. 16.4–19.6% BDL), and a longer snout-vent length (67–93% BDL vs. 56.9–60.1% BDL) ( Didier and Rosenberger 2002).

Hydrolagus melanophasma is known from southern California and Baja California with most records from the Gulf of California. Hydrolagus melanophasma is considered a deep-water species despite the shallow depth of the holotype collection. It typically occurs deeper than H. colliei , which is known to occur from surface waters in the northern part of its range to 971 m at the southern end of its range ( Ebert 2003). Documented collections of H. melanophasma are as follows: the holotype at 30.5 m, the paratype at 915 m, four specimens (SIO 68-89) between 565 and 644 m, two specimens (SIO 65-435) at 1155 m, and one specimen (LACM 37753-1) at 1400 m. MBARI ROV footage captured individuals between 1549 and 1667 m.

Remarks. Several live individuals of H. melanophasma were observed on ROV video footage from MBARI surveys of the Gulf of California in 2003 ( Fig. 4 View FIGURE 4 ). Geographic coordinates of the underwater footage are 455 km north of where the holotype was collected and 335 km south of known collections of H. melanophasma in the Gulf of California ( Figure 5 View FIGURE 5 ). Live specimen observations led to insight on coloration in life, habitat selection and behavioral associations and traits.

ROV observations from four transects suggest that H. melanophasma individuals typically occur over soft-bottom habitats or cobble patches with minimal vertical relief. Each specimen had a close association with the sea floor, within a few meters, but was not resting on the bottom. Most observations were over flat, soft-sediment habitat. One individual was observed over a small cobble patch surrounded by soft substrate. This is in contrast to other species of eastern Pacific Hydrolagus , such as H. alphus ( Quaranta et al. 2006) and H. mccoskeri ( Barnett et al. 2006) , that are known to associate with areas of high rocky relief. Water clarity of H. melanophasma observations was always poor with the presence of large suspended particulate matter.

The behavior of H. melanophasma individuals was to take flight and quickly swim away when approached by the ROV. All individuals of H. melanophasma were observed swimming, never resting on the seafloor. Movements were quick and most often directed away from the ROV; if the ROV attempted to follow an individual, it would rapidly swim out of the field of view. This behavior towards the ROV is in contrast to other species of chimaera that appear either indifferent to its presence, e.g. Harriotta raleighana , or in fact would approach it, e.g. Hydrolagus spp., which were video-taped around seamounts off central California ( Ebert 2003), and were observed to approach the ROV, swimming back and forth around it, and even bumping it.

Hydrolagus melanophasma was documented to co-occur with conspecifics and other species of chimaeras. On one ROV transect, two individuals of H. melanophasma were observed together before both left the camera’s field of vision. On another transect an individual of H. melanophasma was seen shortly after Harriotta raleighana , with both individuals occurring over soft-bottom substrate at about 1550 m. Underwater surveys, like those conducted by MBARI, are essential to further our understanding of the deepsea and its diverse inhabitants.

Comparative Material. Hydrolagus mccoskeri – 2 specimens. CAS 86558, holotype juvenile female, 381 mm TL, 211 mm BDL, southeast of San Cristobal Island, Galapagos (01°5.981’S 89°12.235’W), 296.24 m, collected by J.E. McCosker (CAS), R. Grant Gilmore (Harbor Branch Oceanographic Institution) and Bruce Robison (MBARI), 17 Nov. 1995 (JSL dive 3934); CAS 223971, paratype, juvenile female, 227 mm TL, 107 mm BDL, off Isla Española, Galapagos, (01°5.981’S, 89°45.5’W), 505.97 m, collected by J.E. McCosker (CAS), and John Ross (Smithsonian Magazine), 6 Jul. 1998 (JSL dive 3094).

Hydrolagus alphus – 2 specimens. CAS 201902, holotype, adult male, 419 mm TL, 249 mm BDL, North end of Seymour Island, Galapagos (0°21’42”S, 90°15’0”W), 648 m, collected by J.E. McCosker (CAS) and Carole Baldwin ( United States National Museum), 25 July 1998 (JSL dive 3113); CAS 86425, paratype, subadult female, 480 mm TL, 244 mm BDL, Fernandina Island, Galapagos (0°14.461’S 91°26.535’W – 0°14.820’S 91°26.410’W), 731.52 m, collected by J.E. McCosker (CAS), R. Grant Gilmore (HBOI) and Bruce Robison (MBARI), 17 Nov. 1995 (JSL dive 3958)

Hydrolagus macrophthalmus – 4 specimens. MNHNC P. 7282, holotype, adult male, 385 mm TL, 296 mm BL, preabyssmal zone off Valparaiso, January, 1959; MNHNC P. 5724, adult male, 445 mm TL, 296 mm BDL, off Valparaiso (33°02’S, 71°39’W), 15 Sept. 1974; MNHNC P. 6421 (A), adult female, 627 mm TL, 355 mm BDL, vessel R/V Academic Knipovich (41°04’5”S, 74°16’1W), 300 m, 0 2 Mar. 1973; MNHNC P. 6421 (B), adult female, 572 mm TL, 424 mm BDL, vessel R/V Academic Knipovich (4104’5”S, 74°16’1”W) 300 m, 0 2 Mar. 1973.