Etmopterus abernethyi Garrick, 1957

Etmopterus abernethyi Garrick, 1957 View in CoL

( Figs 2 View Figure 2 , 3 A View Figure 3 , 4 A View Figure 4 , 5 A View Figure 5 , 6 A, C View Figure 6 , 7 A, C View Figure 7 , 8; File S 2: Table S 1 View Figure 8 )

Etmopterus abernethyi Garrick, 1957: 183, figs 3–4 (holotype: NMNZ P.01951, from off south Kaikoura, New Zealand; 1 paratype from off south Kaikoura, New Zealand); Yamakawa et al. (1986): 199 (listed); Last and Stevens (1994): 82 (listed); Last and Stevens (2009): 82 (listed); Dyldin (2015): 55 (listed); Ebert et al. (2021): 11 (listed). View in CoL

Etmopterus abernathyi [sic]: Bigelow and Schroeder (1957): 54, 59, 62 (in text and key); Compagno (1984): 79 (listed).

Etmopterus lucifer View in CoL (not Jordan & Snyder, 1902): Last and Stevens (1994): 81–82, plate 7, fig. 8.23 (listed from around Australia and New Zealand, with brief description); Last and Stevens (2009): 82, fig. 10.9 (listed from around Australia and New Zealand, with brief description); Straube et al. (2013): 261 (listed, New Zealand); Last and Stevens (2015): 143, fig. 25.3 (1 specimen, NMNZ P.037103 from southeastern Tuatoru Knoll, northern New Zealand); Weigmann (2016): 896 (listed, southwestern Pacific); Duchatelet et al. (2021): 825, fig. 2 (figure showing ventral side of body with bioluminescence).

Materials examined.

51 specimens. Holotype: NMNZ P.01951 , immature male 330 mm TL, off south Kaikoura, New Zealand, 42°58'S, 173°40'E, 366 m, November 1955. Paratype: MCZ 39714 , female 267 mm TL, off south Kaikoura, New Zealand, 42°50'S, 173°41'E, 180 m, February 1956. Non-types: AMS E.5530 , female 355 mm TL, south of Gabo Island, southeastern Australia, 37°00'S, 149°54'E, 6 October 1914; AMS E.5531 , female 301 mm TL, southeast of Gabo Island, southeastern Australia, 37°00'S, 150°00'E, 15 September 1914; AMS I.12820 , mature male 403 mm TL, Great Australian Bight, southern Australia, 32°00'S, 129°28'E, 14 May 1913; AMS I.15994 -003, female 346 mm TL, south of Eden, southeastern Australia, 37°43'S, 150°15'E, 30 July 1971; AMS I.20096 -003, female 389 mm TL, southeast of Gabo Island, southeastern Australia, 37°38'S, 150°20'E, 30 November 1977, coll. K. Graham; AMS I.26000 -009, female 422 mm TL, off Broken Bay, southeastern Australia, 33°30'S, 152°09'E, 12 February 1986, coll. K. Graham; AMS I.40290 -003, juvenile male 206 mm TL, off Bermagui, southeastern Australia, 36°27'S, 150°18'E, 2 May 2000, coll. K. Graham; AMS I.42746 -003 (3 specimens), mature males 388–402 mm TL, western Norfolk Ridge, Tasman Sea, 33°49'S, 167°03'E, 27 May 2003; AMS I.44903 -001 (2 specimens), 323–363 mm TL, Taupo Seamount, Tasman Sea, 33°21'S, 156°07'E, 11 September 2009, coll. K. Graham; AMS I.44991 -004 (4 specimens), 386–415 mm TL, north of Sydney closure, southeastern Australia, 33°39'S, 151°57'E, 15 September 2009, coll. K. Graham; AMS I.45667 -013, mature female 432 mm TL, Ulladulla slope, southeastern Australia, 35°25'S, 150°51'E, 4 November 2011, coll. K. Graham; AMS I.46064 -001 (2 of 5 specimens), mature female 473–492 mm TL, Gascoyne Seamount, southeastern Australia, 36°10'S, 156°12'E, 11 June 2012, coll. K. Graham; CAS 218737 (2 specimens), 307–377 mm TL, Tasman Sea, 32°42'S, 162°34'E, 850–872 m, 25 May 2003; CSIRO H 2353-01 , mature male 395 mm TL, northwest of Bunbury, western Australia, 32°52'S, 114°35'E, 517 m, 25 December 1989; CSIRO H 6042-13 , female 472 mm TL, CSIRO H 6042-14 , female 396 mm TL, CSIRO H 6042-15 , female 420 mm TL, Lord Howe Rise, Tasman Sea, 32°41'S, 162°33'E, 855–874 m, 25 May 2003; CSIRO H 6044-09 , immature male 209 mm TL, Lord Howe Rise, Tasman Sea, 34°01'S, 162°36'E, 812–818 m, 25 May 2003; CSIRO H 7051-14 , female 451 mm TL, east of Wollongong, southeastern Australia, 34°18'S, 151°25'E, 440 m, 20 September 2009; CSIRO H 7052-5 , immature male 287 mm TL; CSIRO H 7052-6 , immature male 321 mm TL; CSIRO H 7052-7 , female 333 mm TL; CSIRO H 7052-8 , female 405 mm TL; CSIRO H 7052-9 , female 388 mm TL; H 7052-10, female 386 mm TL; CSIRO H 7052-11 , female 437 mm TL, northeastern Flinders Island, Tasman Sea, 39°34'S, 148°50'E, 450–570 m, 3 October 2009; CSIRO H 7059-03 , female 406 mm TL; CSIRO H 7059-04 , female 438 mm TL, east of Sydney, southeastern Australia, 33°40'S, 151°55'E, 530 m, 15 September 2009; CSIRO H 7174-01 , juvenile male 383 mm TL, Lord Howe Rise, Tasman Sea, 34°05'S, 162°49'E, 560 m, 14 April 2003; CSIRO H 8866-01 , female 391 mm TL, east of Eaglehawk Neck, Tasman Sea, 43°06'S, 148°15'E, 490 m, 16 February 2022; CSIRO H GT 6242, female 372 mm TL, presumably Australia; CSIRO T 598, mature male 371 mm TL, Great Australian Bight, southern Australia, 33°26'S, 129°05'E, 425–545 m, 4 June 1983; NMMZ P.20893 (1 of 3 specimens), mature male 329 mm TL, southern Mernoo Bank, New Zealand, 43°44'S, 174°56'E, 423 m, 6 May 1987; NMMZ P.27020 , female 527 mm TL, Auckland Island Rise, New Zealand, 49°40'S, 168°25'E, 636–648 m, 20 October, 1990; NMNZ P.031152 (1 of 3 specimens), pregnant female 439 mm TL, northeastern Chatham Rise, New Zealand, 42°52'S, 178°09'E, 505–510 m, 26 May 1994; NMMZ P.47326 , female 461 mm TL, central southern Chatham Rise, New Zealand, 44°21'S, 178°15'W, 507–513 m, 31 December 2006; NMNZ P.054695 , female 319 mm TL, southern Hokitika Canyon, New Zealand, 42°48'S, 169°51'E, 555 m, 4 August 2012; NMNZ P.057055 , female 235 mm TL, Hokitika Canyon, New Zealand, 42°51'S, 170°31'E, 650 m, 27 July 2014; NMNZ P.058027 , female 294 mm TL, east coast of North Island, New Zealand, 15 June 2015; NMMZ P.60912 , female 461 mm TL, Chatham Rise, New Zealand, 43°47'S, 178°18'W, 407–416 m, 27 July 2015. USNM 318374 (1 of 7 specimens), immature male 240 mm TL, Mernoo Bank, New Zealand, 300–800 m, May 1990.

Diagnosis.

A moderately large Etmopterus belonging to the E. lucifer group by having elongated anterior and posterior branches of lateral flank marking, and differing from other members by the following combination of characters: hook-like dermal denticles not overlapping each other, in well-defined rows; origin of second dorsal fin anterior to origin of base of flank-marking; infracaudal marking connected with caudal-fin base marking through pair of luminous lines; posterior caudal-fin marking long, length 30.2–46.5 % caudal-fin length; and ventral pectoral marking strongly curved.

Redescription.

Morphometric information is provided in File S 2 (Table 1 View Table 1 ). Proportional measurements and tooth counts are provided as ranges for the paratype and the non-types, followed by the holotype in parentheses. A precise tooth count of the lower jaw teeth is not possible in the holotype as several teeth are missing.

Trunk sub-cylindrical, body width narrower than to slightly wider than body height; abdomen longer than lower caudal peduncle; head subconical, slightly depressed. Snout moderately short (Fig. 2 View Figure 2 ), narrowly rounded in lateral and dorsal view. Eye oval. Spiracle bean-shaped. Gill openings small, nearly straight. Mouth broad, very slightly arched.

Teeth dissimilar in upper and lower jaw, with strong ontogenetic change and sexual dimorphism; upper teeth multicuspid, in three functional series; in lower jaw unicuspid, in three series, one functional; lower teeth blade-like, with strongly oblique cusp. No distinctive symphyseal and intermediate teeth. Upper teeth central cusp rather thick; immature males and females with 1–2, rarely 3, cusplets on each side of the upper-teeth cusp, but mature males with 3–4 cusplets, rarely 2 (Fig. 3 A View Figure 3 ); in mature individuals, longest cusplet length about two-third of the cusp in mature individuals; cusp and cusplets of upper teeth narrowly triangular, lower teeth of mature individuals not erected. Tooth count of upper jaw 22–28 (23), lower jaw 32–42, total count 54–70.

First dorsal fin (D 1) long and rather small, with round apex, origin just below to posterior to a vertical line through pectoral-fin (P 1) free rear tip. Second dorsal fin (D 2) larger than D 1, apex angular, posterior margin especially concave, free rear tip moderately elongated; D 2 spine long and curved. P 1 moderate in size, with angular free rear tips, base narrow, posterior margin slightly concave. Pelvic fin (P 2) narrowly triangular. Clasper of mature males rather long. Caudal fin elongate, caudal fork not especially developed; terminal lobe broad.

Dermal denticles hook-like, rather high, recurved (Fig. 4 A View Figure 4 ), widely-spaced, not overlapping, giving a rough texture of the skin, in defined rows; denticles present on underside of snout, except for a broad area around mouth; underside of gill slits fully covered with denticles (small bare patch rarely present between underside of gill slits); P 1 inner margin with a broad naked area, D 1, D 2 and P 2 inner margins with narrow naked areas; denticles present on fin bases; denticles scarcely distributed on fins in juveniles, increasing the coverage to most of the areas of ceratotrichia with increasing size, especially prominent on D 2 (Fig. 5 A View Figure 5 ).

Body lateral side with short, dash-like markings; head dorsal surface with scattered dot-like markings; dorsal contour of the body with a single line of dot-like markings, extending mid-dorsally from about the level of anterior fontanelle to origin of D 2; ventral pectoral marking elongated and arched (Fig. 6 A, C View Figure 6 ), its tip falling short of P 1 insertion. Flank markings well defined, with elongated anterior and posterior branches; anterior flank marking slender, slightly curved, extending above P 2 origin; posterior flank marking straight, slightly thicker, usually shorter than anterior flank marking (rarely longer than anterior flank marking); anterior flank marking length 92.1–182.5 (132.7) % posterior flank marking; posterior flank marking usually not extending beyond D 2 free rear tip; flank marking base rather narrow, origin well posterior to D 2 origin. Infracaudal marking prominent, extending from flank marking base to about the same level of posterior flank marking tip, connecting to the caudal-base marking by a pair of lines formed by bioluminescent melanophores (Fig. 7 A, C View Figure 7 ; see also Duchatelet et al. 2021); caudal-base marking broad, with a moderately thick, slender extension, bifurcate before lower caudal-fin origin, length 17.4–31.3 (30.5) % caudal-fin length. Posterior caudal-fin marking very long, its length 30.2–46.5 (38.9) % caudal-fin length.

Coloration.

When fresh, body generally shiny grey to dark grey, black ventrally; transition between lateral and ventral sides strongly demarcated. Dorsal midline with pale stripe; P 1 and P 2 generally translucent, with darker bases; dorsal fins mostly pale grey in the proximal two-thirds of ceratotrichia. Caudal-fin dorsal and postventral margins black, without a dark blotch on mid-caudal fin. No black blotch between infracaudal marking and caudal-base marking. Caudal fin with distinct black tip at terminal margin.

After preservation, body coloration slightly darker, yet most of markings remaining distinct. Transition between lateral and ventral sides becoming less demarcated.

Variant.

One specimen ( NMNZ P.031152 , 1 of 3 specimens, pregnant female 439 mm TL) with an extremely long posterior flank marking, anterior flank marking 74.6 % posterior flank marking, with tip almost extending to lower caudal-fin origin (Fig. 8 View Figure 8 ), but otherwise identical to other E. abernethyi .

Size.

Up to 527 mm TL and 403 mm TL for females and males, respectively. Smallest mature male 325 mm TL; smallest of five mature females 432 mm TL. Smallest specimen studied here without umbilical scar measuring 206 mm TL.

Distribution.

Southwestern Pacific and also southeastern Indian Ocean, known from southeastern, southern, and southwestern Australia, the Tasman Sea, and around New Zealand, at depths of 180– 872 m. Common at catches in research cruises in Australian waters (K Graham pers. comm.), uncommon in commercial trawlers around New Zealand (Roberts et al. 2015).

Nomenclatural discussion.

Etmopterus abernethyi was described from off New Zealand by Garrick (1957). Soon afterwards, Garrick (1960) recognized that the diagnostic characters of E. abernethyi in Garrick (1957) were actually due to ontogenetic and intraspecific variations and that this species was not separable from E. lucifer . Despite direct comparisons with E. lucifer specimens from Japan and E. molleri from southwestern Australian waters, Garrick (1960) was not able to find morphological differences between the two species, although he mentioned that most of the New Zealand specimens possess a distinct shape of their luminescent areas on the ventral surface of the caudal peduncle. Thus, he synonymized E. abernethyi and E. molleri with E. lucifer . Subsequently, the former was generally considered a junior synonym of E. lucifer (e. g., Compagno 1984 [as E. abernathyi ]; Yamakawa et al. 1986; Last and Stevens 1994; Weigmann 2016). In contrast, Yamakawa et al. (1986) resurrected E. molleri , and further identified the sole paratype of E. abernethyi as belonging to E. molleri .

Re-examination of the type series and numerous non-types of E. abernethyi and E. lucifer shows distinct character differences separating the two species. The types of E. abernethyi as well as other specimens from the southwestern Pacific previously identified as E. lucifer , are all characterized by an elongated and arched ventral pectoral marking, which is strongly contrasted with the stout and knife-shaped ventral pectoral marking in specimens of E. lucifer from the northwestern Pacific (Fig. 6 A, C View Figure 6 ). Another consistent character difference between the two species is the shape of the infracaudal marking, which is connected to the caudal-base marking by a pair of lines in the types of E. abernethyi and the other southwestern Pacific specimens, but is not connected in the northwestern Pacific E. lucifer (Fig. 6 B, D View Figure 6 ). These luminescent lines are especially prominent in life (see Duchatelet et al. 2021: fig. 2 [as E. lucifer ]).

Although very similar to each other morphologically, the consistency of the small differences in markings warrants specific separation. The genetic evidence further supported the separation of the two lineages. As a result, E. abernethyi is resurrected here to represent records hitherto assigned to E. lucifer in the southwestern Pacific.

Remarks.

Yamakawa et al. (1986) identified the paratype of E. abernethyi as a specimen of E. molleri . our re-examination of this paratype, however, reconfirms its conspecificity with E. abernethyi evidenced by having the origin of flank marking base behind a vertical line through D 2 origin, and the infracaudal marking connected to the caudal-base marking by a pair of lines.

Comparisons.

Etmopterus abernethyi belongs to the E. lucifer group, as defined by Straube et al. (2010), in having elongated anterior and posterior branches of the flank marking. It is most similar to E. lucifer , with both having a combination of hook-like denticles, the origin of flank marking base behind a vertical line through D 2 origin, and a rather long posterior caudal-fin marking. They are also similar in morphometric characters and overlap in vertebral counts. Etmopterus abernethyi can be distinguished from E. lucifer by an elongated and arched ventral pectoral marking (vs. ventral pectoral marking stout and knife-like in E. lucifer ; Fig. 6 View Figure 6 ), and the infracaudal marking connected to the caudal-base marking by a pair of lines (vs. not connected; Fig. 7 View Figure 7 ). In addition, the ratio of the lengths of the anterior flank-marking branches relative to that of the posterior branches is significantly lower in E. abernethyi than E. lucifer (Mann-Whitney U test, p <0.01). This means that the anterior branch is usually slightly longer than the posterior branch in E. abernethyi , while the anterior branch is usually significantly longer than the posterior branch in E. lucifer (Fig. 9 View Figure 9 ). Further, E. abernethyi has a broad distribution from the southeast to southwest Australia, the Tasman Sea, and around New Zealand, while E. lucifer is found from subboreal Northwest Pacific off Japan to the tropical northern South China Sea.

In the southwestern Pacific, E. abernethyi may be confused with the sympatric E. molleri . The former is readily distinguished from the latter by having the origin of the flank marking base behind a vertical line through D 2 origin (vs. the origin of the flank marking base well before a vertical line through D 2 origin in E. molleri ), the infracaudal marking connected to the caudal-base marking by a pair of lines (vs. not connected), fewer diplospondylous trunk vertebrae (11–18 vs. 20–21) and dorsal fins heavily covered with denticles in adults (vs. largely naked). The length of anterior branch of flank marking relative to the posterior branch is also significantly higher in E. abernethyi than in E. molleri (Mann-Whitney U test, p <0.01, Fig. 9 View Figure 9 ).