Heteroclinus argyrospilos, Hoese & Pogonoski, 2021

Hoese, Douglass F. & Pogonoski, John J., 2021, Description of a new deep-water species of Heteroclinus (Pisces: Teleostei: Clinidae) from southern Australia, Zootaxa 5082 (3), pp. 286-293 : 287-290

Heteroclinus argyrospilos , n. sp.

Figures 1–3 , Table 1

Holotype. CSIRO H 7641-01 , 31.5 mm SL female, south-west of Point D’Entrecasteaux, 34°53.16’S, 115°30.42’E to 34°53.03’S, 115°29.94’E, Western Australia, 21 November 2005, CSIRO, FRV Southern Surveyor, Sherman sled, 95–100 m.

Paratype. AMS I.50055-001 (formerly CSIRO H 5338-09 ), 33.5 mm SL, Great Australian Bight, approximately 300 km west of Ceduna, 31°50.05’S, 130°45.90’E to 31°50.32’S, 130°45.10’E, South Australia, 14 May 2000, A. Williams, aboard FRV Southern Surveyor , benthic dredge, 55 m.

Diagnosis. Dorsal fins III, XXV, 2; anal-fin rays II, 17–18; segmented caudal-fin rays 8; pectoral-fin rays 11, uppermost ray short, about half length of second ray, rays becoming progressively longer ventrally to longest ray 6 or 7; pelvic-fin rays I,3; gill rakers on outer face of first arch 2 + 7 = 9. Lateral line well developed anteriorly only, extending on upper part of arch to near end of pectoral fin, but not extending ventrally to midline; anterior scales overlapping with single, median posterior pore, posterior lateral line scales separate with a median pore at each end. First segmented dorsal-fin ray well separated from last dorsal-fin spine. Circumorbital head pores uniserial (11 pores in both specimens), with anterior infraorbital pores on main canal and not on ventral tubes. Orbital tentacle elongate with a rounded lobe distally, length about equal to eye diameter. Nasal tentacle simple, short, flap length about equal to tubular base length. First dorsal fin slightly elevated, longer than anterior spines of second dorsal fin, slightly shorter than last spine in second dorsal fin; first dorsal fin originating over preoperculum, just before posterior end; fin largely separate from second dorsal fin with membrane attached to body just before or to base of first spine in second dorsal fin. Dorsal-fin spines without fleshy lobes at distal tips. First segmented dorsal-fin ray separated from last dorsal-fin spine by same distance as distance between last two dorsal-fin spines; last dorsal-fin ray connected by membrane to dorsal base of caudal fin. Last anal-fin ray connected by membrane along half its length to caudal peduncle. Body with reddish-brown mottling, a series of distinct dark reddish-brown vertical bars below eye in freshly collected holotype, with large silver spots ventrally on the sides of belly and smaller silver spots present on head; head and body uniformly light brown in preservative.

Description. Based on holotype and paratype. First dorsal III; second dorsal-fin spines 25; segmented dorsalfin rays 2; anal fin-rays II, 17, in holotype, II, 18, in paratype; pectoral-fin rays 11 on both sides; pelvic-fin rays I,3; segmented caudal-fin rays 8, vertebrae 13 + 23 = 36 in holotype; circumorbital pores 11; gill rakers on outer face of first arch 2+ 7 in paratype; pored lateral line scales 19 in holotype, 17 in paratype, (arched portion of line) + 0 on midside. Vomer with conical teeth in inverted V-shape, one main row, with 1–2 smaller teeth behind main row near anterior tip on each side. Morphometrics of the types are given in Table 1 .

Head and body compressed; snout with small indented notch before anterior margin of eye, gently curved ventrally in side view, snout shorter than eye diameter (0.4–0.6 of eye length), eye placed near front of head, about middle of maximum head depth; interorbital narrow, about one-half eye diameter; jaws reaching to below posterior quarter of pupil; anterior nostril at end of short tube, about 2–3 nostril diameters above upper lip, with short thin nasal tentacle, without side lobes or branches; posterior nostril with elevated rim above anterior margin of eye; gill rakers on outer face of first arch short and slender, much shorter than filament length; rakers on inner face of first arch and following arches slightly shorter and pointed; tongue tip broadly pointed; upper jaw with 2 rows of slightly conical teeth anteriorly, tapering laterally to one row; similar sized teeth in lower jaw in 2 rows anteriorly, tapering to one row laterally. Genital valve an indistinct low fold.

Head pores as shown in Figure 1 . Circumorbital and preopercular pores uniserial, infraorbital canal without lateral extensions to pores. Nasal section with a pore before anterior nostril and one before posterior nostril; interorbital section with a pore on each side above anterior half of eye, a single median interorbital or supraorbital commissural pore between interorbital tentacles; a supraorbital pore above dorsoposterior section of eye on each side; a postorbital pore behind eye with canal extending posteriorly toward lateral line; infraorbital canal extending from posterior end of eye to below front of eye; preopercular section extending ventrally from postorbital canal section with 8 pores, two lower pores at end of short tube off main canal, continuing to mandibular section below jaws with 5 pores; an occipital canal section extending dorsally from postorbital section, with two pairs of pores extending from main canal and a median occipital commissural pore.

Head largely naked, body scales small and cycloid extending forward to above operculum below middle of first dorsal fin; many body scales apparently missing in random patches on body, where present scales overlapping and forming distinct rows, becoming non-imbricate posteriorly on caudal peduncle; pectoral fin base covered with small embedded scales, scales apparently not extending onto base of fin; scales not covering bases of dorsal-fin spines and membranes between spines; scales not extending onto anal fin; scales extending onto anterior base of caudal-fin rays.

All unsegmented fin-rays unbranched; first dorsal fin connected to body just before base of second dorsal fin or to just above base of first spine of second dorsal fin; first dorsal fin elevated and subequal in height to second dorsal fin (varying from slightly longer than anterior spines of second dorsal fin to slightly shorter than remaining spines in second dorsal fin), second spine longest, with first spine slightly longer than third spine; second dorsal origin above a point near posterior end of operculum, above or in front of pectoral insertion and well behind pelvic insertion; first spine of second dorsal slightly shorter than following spine, spines becoming progressively longer posteriorly, with last spine longest; two segmented dorsal rays shorter than last dorsal-fin spine separated from last spine by a greater distance than distance between last two spines; anal-fin origin below 9 th to 10 th spine of second dorsal fin; anal-fin spines distinctly shorter than segmented rays, first spine shortest; posterior segmented rays becoming progressively longer, last two rays slightly shorter, closely spaced and more widely separate from anterior rays; caudal fin with truncate to slightly rounded margin, rays unbranched, 10 articulating with epurals, 8 thickened segmented rays, and an upper and a lower slightly smaller, unsegmented ray in paratype and with only 1 upper elongate unsegmented ray in holotype and 1–2 upper and lower very short simple procurrent rays (difficult to discern); pectoral fin with rounded posterior margin, central rays longest, reaching to above first or second anal-fin spine; pelvic fin with hidden spine, 3 developed rays; pelvic-fin rays not reaching to anus, inner ray about one quarter length of second ray.

Coloration of freshly collected holotype ( Figure 2A ): Head and body reddish brown with scattered variably sized, dark brown, irregularly shaped spots; a series of dark brown bars below eye, most breaking into spots immediately below eye; spots and bars with dull white to grey interspaces and a few small silver spots; belly and pectoral-fin base with large, irregularly shaped silver spots, varying from pupil to eye sized; dorsal and anal fins with scattered dark brown spots with translucent patches between spots; caudal fin with three broad vertical dark brown bars; pectoral fin with three dark brown bands; pelvic fin brown at base with two dark cross bars on fin, with silver interspaces.

Coloration in alcohol: Head, body and fins uniformly light brown, without distinct marking ( Figure 2B ).

Distribution. The species is known only from two specimens from south-western Australia. The holotype was collected by a benthic sled in 95–100 m depth from south-west of Point D’Entrecasteaux (ca. 34°53.16’S, 115°30.42’E), Western Australia. The catch was dominated by sponges and other invertebrates, with no other fishes collected. The paratype was collected by benthic dredge in 55 m depth from the central Great Australian Bight, approximately 300 km west of Ceduna (ca. 31°50.05’S, 130°45.90’E), South Australia.The catch consisted of a diverse mix of invertebrates (sponges dominant by biomass) and small fishes. The fish species retained and identified at the CSIRO include the following, with known depth range included in parentheses: Apopterygion alta Kuiter (5–77 m), Austrolabrus maculatus (Macleay) (1–40 m), Crapatalus munroi Last & Edgar (0–18 m), Dipulus multiradiatus (McCulloch & Waite) (0–15 m), Echinophryne crassispina McCulloch & Waite (5–20 m), Ophiclinus ningulus George & Springer (0–20 m), Parapercis ramsayi (Steindachner) (2–97 m), Phyllophryne scortea (McCulloch & Waite) (1–94 m), Pseudophycis breviuscula (Richardson) (4–200 m) and Vincentia badia Allen (1–55 m). The bulk of these species have a wide depth range, but in a few cases the station extends the lower known depth range. In addition, material not retained also included the following genera: Arnoglossus, Capropygia, Gonorynchus, Meuschenia, Maxillicosta, Neosebastes and Upeneichthys . Small-mesh sampling devices such as benthic sleds and beam trawls have proven useful for collecting small fishes beyond normal diving depths, resulting in numerous new discoveries documented in the last decade, e.g. Pseudotrichonotus belos Gill & Pogonoski 2016 and Plectranthias spp. ( Gill et al. 2021).

Etymology. From the Greek argyros = silver + spilos = spot, referring to the silver spots on the belly and lower surface of head and pectoral fin base, treated as a noun in apposition.

Remarks. Heteroclinus argyrospilos n. sp. is distinct from other species in the genus in having the two segmented dorsal-fin rays widely separated from the last dorsal spine ( Figure 3A ). In other species of Heteroclinus , the first segmented dorsal-fin ray is spaced close to the last dorsal-fin spine ( Figure 3B ). Heteroclinus whiteleggii has two segmented dorsal-fin rays, with the first very close to the last dorsal-fin spine, more rounded head, more slender body and only two segmented pelvic-fin rays vs. three in the new species. Rarely, Heteroclinus adelaidae (Castelnau) and H. kuiteri (Hoese & Rennis) have two segmented dorsal-fin rays, but those also have only two segmented pelvic-fin rays. The new species is also distinct in having a short lateral line, without lateral line scales extending ventrally to the midline of the body. A reduced lateral line, with no or only a few lateral line scales along the midline anteriorly on the body is also found in some adult specimens of Heteroclinus adelaidae , H. kuiteri and H. macrophthalmus as reported by Hoese & Rennis (2006). Heteroclinus macrophthalmus Hoese also has only two segmented pelvic-fin rays. The reduced lateral line is not found in larger juveniles and adults of other described species, but its absence in the new species could be due to the small size of the type specimens. In other species, such as Heteroclinus heptaeolus , the lateral line scales are typically not developed on the midline of the body in specimens below 16 mm SL, but are well developed at the size of the specimens of the H. argyrospilos described here. The new species has a strongly compressed head and body, typical of the Heteroclinus heptaeolus complex, which also includes H. wilsoni (Lucas) and three undescribed species, and may be related, having lost the first segmented dorsal-fin ray. That complex is characterized by three rays, with wide separation of the last two dorsal-fin rays from the first dorsal-fin ray, and the first ray very close to the last dorsal-fin spine.

Figures

FIGURE 1. Head of Heteroclinus argyrospilos, showing canals (dashed lines) and pores (open circles) and position of dorsal fins; anterior and posterior nostril at end of short tubes elevated above skin. Letters indicate canal sections: a = nasal, b = supraorbital, c = postorbital, d = infraorbital, e = interorbital, f = preopercular, g = mandibular, h = occipital (median pore not shown), l = lateral line. Drawing by D.F. Hoese based on holotype and paratype.

FIGURE 2. Heteroclinus argyrospilos, CSIRO H 7641-01, holotype, A. Freshly collected (photo by K. Gowlett-Holmes). B. Preserved coloration.

FIGURE 3. Radiographs of Heteroclinus showing insertion of dorsal fins and position of segmented rays. Scale = 1 cm. FSDR = first segmented dorsal-fin ray, FAPT = first anal-fin pterygiophore.A. Holotype of Heteroclinus argyrospilos CSIRO H 7641- 01 (note two dorsal-fin rays) B. Heteroclinus heptaeolus SAMA F.5066 (note three rays).