Pezichthys nigrocilium, Last & Gledhill Csiro, 2009
Last, Peter R. & Gledhill Csiro, Daniel C., 2009, A revision of the Australian handfishes (Lophiiformes: Brachionichthyidae), with descriptions of three new genera and nine new species 2252, Zootaxa 2252 (1), pp. 1-77 : 47-50
treatment provided by
Pezichthys nigrocilium sp. nov.
Diagnosis. Member of the genus Pezichthys with a combination of the following characters: esca small, 11% of illicium length (including esca); illicium short, very slender, without dermal spinules, its length about 16% SL, 3.5 times in head length; head length about 9 times snout length; snout short, length 6% SL; eye large, 5.6 times in head length; body narrow, maximum width 19% SL; interorbital width narrow, about 5% SL; scale bases subcircular with prominent, strongly divergent, bifurcate spinules (except for those closelyassociated with pores of the acoustico-lateralis system); spinules variable in length over body; dorsal-fin elements covered with spinules, outer fin membranes naked; first dorsal-fin base short, length 15% SL; second dorsal-fin rays 15, fin base about 57% SL; length of second dorsal-fin spine 1.4 times length of longest ray of second dorsal fin; anal-fin rays 8; body mainly pale pink with prominent eyelash-like marking radiating from eye; caudal fin plain, without fine spots.
Description. D1 2; D2 15; A 8; Pc 7; Pv i, 4; C 1 + 4 + 4 = 9; Vt 9 + 12 = 21.
Body moderately short, strongly compressed; upper anterior profile almost straight to first dorsal-fin origin, directed posterodorsally, not truncate; not deeply notched behind eye; top of eye close to dorsal margin of head; narrowly oval when viewed anteriorly; nape humped slightly; anterior ventral profile almost straight, slightly concave between pelvic fins; abdomen slightly expanded; caudal peduncle elongate, length 8.9% SL. Head length 55% SL; snout very short, about 9 times in head; eye large, 5.6 times in head length; gill opening small, aperture subequal in size to pupil, located well above and slightly behind insertion of pectoral fin; nostrils very small, openings obscure. Mouth small, terminal, slightly protractile; upper jaw strongly oblique, 4.3 in head; lips fleshy, upper jaw connected laterally to lower jaw by fleshy fold; angle of jaw partly recessing into groove, situated below anterior third of eye. Teeth minute, villiform, in narrow bands in both jaws; mouth not dissected to expose vomer and tongue.
Skin rather thin, not corrugated, covered with mainly bifid, spinulose scales; no separate wart-like patches of skin; no obvious dermal flap on mid-arm of pectoral-fin; dermal flaps absent on body and other fins. Body scales close-set (usually almost touching), not imbricate or arranged in defined rows; distributed over entire body and on rays of dorsal, pectoral and caudal fins; absent on fin membranes, except at bases of dorsal fins; large, naked, vertically oval patch surrounding gill opening, its height about two-thirds of eye diameter; scale bases large (to about a third of pupil diameter), embedded, but not within a prominent mound of thickened skin. Spinules short, well exposed, monospinulate and bifurcate, originating near centres of scales; mainly upright to directed slightly posteriorly; narrowly divergent (length of spines of each spinule usually longer than the distance between their tips), bifurcating above skin surface; tips not connected by integument when undamaged; on belly smaller and less upright than those above; spiny scales present on anterior orbital membrane. Spiny scales on first dorsal fin concentrated on anterior edge of leading spine, posterior edge of third spine and along their lateral edges; in second dorsal fin, spinules concentrated on leading ray and lateral surface of subsequent rays; in caudal fin, along dorsal margin of uppermost ray and along lateral edges of most other rays, absent from ventral edge of lowermost ray; in pectoral fin, restricted to basal halves of rays on their dorsal edges; feeble or absent on anal and pelvic fins. Illicium base and main stem naked, not obviously covered with sheath-like membrane. Scales of acoustico-lateralis system bicuspid, not obviously demarcated from main spinules; scales widely separated and arranged in barely discernable rows; pronounced near mouth, otherwise indistinct on head and body.
Illicium subterminal on snout; well separated from upper jaw, its insertion not confluent with origin of first dorsal fin; short, very slender, 3.5 times in head, 1.7 times in length of second dorsal-fin spine; apex of esca above middle of eye when illicium depressed; not recessible into a groove beside first dorsal fin; esca very small (its length about 9 times in length of illicium), not bulbous, narrow, fleshy, without filamentous branches; illicial base not bulbous. First dorsal fin short-based; second dorsal-fin spine well separated from base of illicium, much longer than third spine; fin membrane thick, expanded around each spine, posterior extension short, membrane terminating forward of origin of pelvic fin; anterior elements of both fins strongly recurved; first dorsal-fin base 3.8 times in second dorsal-fin base. Second dorsal fin low, moderately incised, anterior and penultimate posterior rays longest; rays simple, very fine, their tips very strongly recurved; fin base moderately elongate, 57% SL; longest ray of second dorsal fin 1.4 times in longest dorsal-fin spine; bases of rays embedded slightly, basal fifth of their length covered with flesh and skin. Anal fin tall with short base, rays not fleshy, moderately incised, tips strongly recurved; penultimate posterior rays longest; anal-fin base 2.7 times in second dorsal-fin base. Pectoral fin weakly arm-like, radials moderately elongate, extending slightly beyond gill opening; fin rays digitiform, slender, membranes deeply incised, increasingly so posteriorly, tips flexible, flattened slightly (often recurved distally). Pelvic fin short; rays digitiform, slender, deeply incised; anterior spine short, embedded and indistinct; fin located on ventral surface, usually directed ventrally, base aligned horizontally; interpelvic space almost flat, broad, width 8.5% SL. Caudal fin narrow, almost truncate, middle pair of rays shorter than two adjacent pairs; length 3.2 times caudal peduncle depth.
Coloration. Frozen: Body almost uniformly pale pinkish above, white below; dark markings confined to areas around eye, beneath soft dorsal fin, and on caudal peduncle, caudal-fin base, illicium base, second dorsal-fin spine, and outer pectoral and caudal fins. Dark eyebrow-like markings originating from eyes; markings not bilaterally symmetrical; consisting of two short, dark, vertical streaks above each pupil; a divergent, V-shaped marking originating at posterior margin of left eye (a single horizontal streak at right eye); a broader and longer posteroventrally directed streak at posteroventral margin of left pupil, paired posteroventral streaks on right pupil. Three weak dark saddles beneath dorsal fin; first as parallel vertical streaks (resembling supraorbital marking); posterior markings and those on upper caudal peduncle less well defined; dark, well-defined, vertical streak at base of caudal fin. Illicium translucent with dusky esca and dark blotch at its anterior base. Anterior margin of leading ray of first dorsal fin dark, second ray distinctly paler; base of second ray and leading membrane silvery white. Second dorsal fin mostly translucent, anterior and posterior tips silvery; two fine dark marks distally near middle of fin. Pelvic and anal fins translucent. Eye silvery white, pupil black.
Size. Known only from the holotype, 40.8 mm SL (ca. 54 mm TL). Size of newly hatched young and egg capsule diameter unknown.
Distribution. Demersal, Pieman Canyon, off Granville Harbour, western Tasmania, 41° 48'S, 144° 34'E, at 176 m depth.
Etymology. Epithet based on the Latin niger (black) and cilium (eyelash) in allusion to a dark, eyelashlike markings above each orbit. Proposed vernacular name: Eyelash Handfish.
Comparisons. The distinctive ‘eye-lash like’ markings around the eye are unique to this species. Of members of the genus Pezichthys , P. nigrocilium is most similar to P. amplispinus and P. macropinnis . These species have a small esca (less than a quarter of illicial length) and scales with subcircular (rather than stellate) bases. The holotype of P. nigrocilium appears to differ from these and other Pezichthys in the following ratios: illicium length 28 vs. 33–39% of head length in P. amplispinus , 36–42% in P. compressus , 38–41% in P. eltanini , and 54% in P. macropinnis ).
Pezichthys nigrocilium differs from P. amplispinus , P. compressus , and P. macropinnis in having: a larger eye (horizontal diameter 9.9 vs. 7.0–8.5% SL in P. amplispinus , 6.4–6.6% in P. compressus , and 7.1% in P. macropinnis ); shorter first dorsal-fin base (length 15 vs. 18–20% in P. amplispinus , 26–28% in P.compressus , and 18% in P. macropinnis ), anal-fin base (length 21 vs. 25–28% SL in P. amplispinus , 27–30% in P. compressus , and 24% in P. macropinnis ), snout (length 6.1 vs. 8.4–10% SL in P. amplispinus , 9.6–10% in P. compressus , and 9.1% in P. macropinnis ), and esca (length 1.7 vs. 3.1–4.2% SL in P. amplispinus , 6.8–8.0% in P. compressus , and 3.0% in P.macropinnis ); and a narrower body (maximum width 19 vs. 30–38% SL in P. amplispinus , 25–32% in P. compressus , and 32% in P. macropinnis ) and interorbital (width 4.9 vs. 8.1–11% SL in P. amplispinus , 12–13% SL in P. compressus , and 15% SL in P. macropinnis ).
In addition to the above characters, P. nigrocilium differs from P. amplispinus in having: a more slender tail (depth at anal-fin origin 20 vs. 23–26% SL); a narrower interpelvic space (distance 8.5 vs. 11–16% SL); first dorsal fin with shorter second (length 26 vs. 32–36% SL) and third spines (17 vs. 19–26% SL); and a relatively shorter esca (length 11 vs. 19–21% of illicium length). It also differs in the following ratios: head length 9.0 vs. 4.9–6.2 times snout length, and illicium length 9.1 vs. 4.7–5.3 times esca length.
Pezichthys nigrocilium differs from P. compressus in additional characters: a taller second dorsal fin (longest ray 19 vs. 16–18% SL); more elongate caudal peduncle (length 8.9 vs. 3.5–5.9% SL); shorter maxilla (length 13 vs. 15–16% SL) and illicium (length 16 vs. 19–23% SL); a narrower inter-pelvic space (distance 8.5 vs. 10–12% SL); a shorter pre-illicium length (distance 1.5 vs. 3.6–5.8% SL); a more slender body (depth at anal-fin origin 20 vs. 25–26% SL, depth at origin of second dorsal fin 39 vs. 47–48% SL); and a relatively shorter esca (length 11 vs. 35–36% of illicium length). It also differs in the following ratios: head length 9.0 vs. 5.2–5.4 times snout length, 3.5 vs. 2.4–2.8 times illicium length, 5.6 vs. 8.1–8.3 times eye diameter; illicium length 9.1 vs. 2.7–2.8 times esca length.
In addition to the above characters, P. nigrocilium differs from P.eltanini in the following: a longer caudal peduncle (length 8.9 vs. 3.6–5.1% SL); a shorter first dorsal-fin base (length 15 vs. 25–30% SL), second dorsal-fin base (length 57 vs. 62–63% SL), snout (length 6.1 vs. 9.5–10% SL), maxilla (length 13 vs. 15–16% SL), illicium (length 16 vs. 21–22% SL), and esca (length 1.7 vs. 11–18% SL); a narrower body (maximum body width 19 vs. 31–39% SL) and interorbit (width 4.9 vs. 12–15% SL); and a relatively shorter esca (length 11 vs. 54–82% of illicium length). It also differs in the following ratios: head length 9.0 vs. 5.4–5.5 times snout length, 3.5 vs. 2.4–2.6 times illicium length; illicium length 9.1 vs. 1.2–1.8 times esca length.
Pezichthys nigrocilium and P. macropinnis , although known only from the holotypes, differ markedly in body form and coloration. Pezichthys nigrocilium appears to have a longer head (length 55 vs. 49% SL), pelvic-fin (length 23 vs. 16% SL), and maxilla (length 13 vs. 7.6% SL); a longer interdorsal space (distance between bases of third dorsal-fin spine and second dorsal fin 28 vs. 15% SL); a shorter second dorsal-fin base (length 57 vs. 63% SL); and much shorter pectoral-fin (length 23 vs. 27% SL), illicium (length 16 vs. 26% SL), second dorsal-fin spine (length 26 vs. 33% SL), third dorsal-fin spine (length 17 vs. 42% SL), longest second dorsal-fin ray (19 vs. 35% SL), and caudal fin (length 33 vs. 40% SL).
Remarks. The single known specimen of this species was captured on the outer continental shelf off western Tasmania using a benthic sled deployed from the FRV Southern Surveyor. Its absence in fish collections is probably a function of inappropriate sampling rather than genuine rarity. Nevertheless, the extent of its range needs to be established.
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.