Krefft's Pearleye, Scopelarchoides kreffti Johnson 1972


Other Names: Twin-striped Pearleye

Twin-striped Pearleye, Scopelarchoides kreffti. Source: Australian National Fish Collection, CSIRO. License: CC By Attribution-NonCommercial

Summary:
Blackish stripe extending along the body from behind head to close to tail just above the lateral  line. A silvery pearleye with a black stripe along the side above the lateral line from behind the head almost to the caudal fin, and the bases of the first dorsal and tail fins blackish. 
Krefft's Pearleye has large upward-directed eyes and large scales along the lateral line.

Cite this page as:
Bray, D.J. 2018, Scopelarchoides kreffti in Fishes of Australia, accessed 19 Jan 2020, http://136.154.202.208/home/species/3321

Krefft's Pearleye, Scopelarchoides kreffti Johnson 1972

More Info


Distribution

Southeastern Australia from off Cape Barren Island and the Pedra Branca Seamount, Tasmania. Elsewhere the species is circumglobal in the southern hemisphere..

Features

Dorsal fin 8-9; Pectoral fin 24; Pelvic fin 9; Anal fin 26-27; Caudal fin 10 + 9 (segmented rays), 13-15 ventral procurrent rays; Lateral-line scales 58-59; Vertebrae 55. 

Body elongate, moderately compressed; body depth less than head length. Dorsal profile of head nearly straight, dipping slightly to rounded snout. Eye large, tubular, directed upward; eye diameter less than snout length; pearl organ slightly elongate anteriorly and posteriorly, smaller than pupil diameter. Interorbital space and infraorbitals exposed, not covered with skin. Interorbital space with several longitudinal ridges; its width remarkably narrow, 18.6–20.0 in head length. Posterior margin of opercle wavy; pectoral-fin insertion opposite notch at junction of opercle and subopercle. Mouth large, slightly oblique, forming angle of about 15 degrees with respect to horizontal axis of head and body. Supramaxilla well developed, its height greater than that of deepest portion of dentary. Posterior margin of maxilla just reaching vertical through posterior margin of orbit; posterior tip of maxilla pointed. Lips poorly developed or absent. Lower jaw upcurved anteriorly in lateral view and its anterior tip projecting slightly beyond that of upper jaw when viewed from above. Premaxilla with row of small teeth; no teeth around symphysis. Vomer with pair of small teeth, these longer than premaxillary teeth. Each palatine with row of 7–15 teeth, including tiny teeth interspersed between large teeth; longest tooth shorter than longest dentary tooth. Dentary with 2 rows of teeth; numerous small teeth in outer row, similar in size to those on premaxilla; 6–16 much larger teeth in inner row, second or third tooth longest. Lingua with row of 14 teeth; 11 or 12 teeth on basihyal and 2 or 3 teeth on first basibranchial (9 teeth on basihyal and none on first basibranchial in one specimen); teeth progressively shorter posteriorly.

Dorsal fin with unbranched first ray, other rays branched; length of longest ray greater than orbit diameter; fin origin slightly posterior to vertical through pelvic-fin origin. Adipose fin small, not strongly fleshy; fin base wider than any other part of fin; posterior tip of depressed fin just reaching vertical through last anal-fin ray base. Pectoral fin with thick, unbranched uppermost ray, other rays thin, branched; fifth ray longest, its posterior tip just reaching origin of first pelvic-fin ray; fin base slightly oblique, forming angle of about 20 degrees with respect to horizontal axis of head and body. Pelvic fin with branched rays; third or fourth ray longest; posterior tip of depressed fin not reaching anus; origin of first ray on ventrolateral surface of body. Anal fin with unbranched first and second rays, other rays branched; third ray longest, but still shorter than longest pectoralfin ray. Caudal fin with unbranched uppermost and lowermost segmented rays, other rays branched. 

Lateral-line scales relatively large, height of each scale greater than that of pearl organ (located below eye); all scales, except several lateral-line scales, lost in specimens examined. 

Colour

Upper half of head pale grayish-brown, blackish dorsally; upper and lower jaws pale grayish-brown, black or mottled with black; lower half of head bright greenish-blue, suborbital region darker; pearl organ bright greenish-blue. Black stripe extending from behind eye to base of caudal fin above lateral line; stripe darkest near midlength, paler anteriorly and posteriorly; width of this stripe below first dorsal fin subequal to height of pearl organ; additional faint blackish stripe extending from above base of pelvic fin to base of caudal fin below lateral line, width subequal to that of stripe above lateral line; remaining trunk pale grayish-brown anteriorly, becoming beige posteriorly; abdominal area (bordered by posterior tip of opercle, inner base of pectoral fin, pelvic-fin base, and anal-fin origin) bright greenish-blue; anterior half of ventral abdomen dark greenish-blue; posterior half of ventral abdomen silver, with dense black stripe on ventral margin; bases of first dorsal and caudal fins blackish; base of pectoral fin bluish white; anterior part of anal-fin base blackish. Fin membranes transparent, without distinct markings.

Similar Species

Scopelarchoides kreffti differs from S. danae in having the pelvic-fin origin anterior to a vertical through the first dorsal-fin origin (vs. posterior to it), 23–25 pectoral-fin rays (vs. 20–22), 58 or 59 lateral-line scales (vs. 50–52), 0–3 teeth on the basibranchial (vs. 6–11), and pigment stripes along the lateral line (vs. stripes absent or poorly developed).

Species Citation

Scopelarchoides kreffti Johnson 1972, Archiv für Fischereiwissenschaft 23(1): 37, fig. 1. Type locality: Argentine basin, west South Atlantic [34°01'S, 47°39'W]. 

Author

Bray, D.J. 2018

Resources

Australian Faunal Directory

Krefft's Pearleye, Scopelarchoides kreffti Johnson 1972

References


Johnson, R.K. 1972. Ergebnisse der Forschungsreisen des FFS 'Walther Herwig' nach Südamerika. 21. A new species of Scopelarchoides (Myctophiformes, Scopelarchidae) from the South Atlantic Ocean. Archiv für Fischereiwissenschaft 23(1): 37-42 

Johnson, R. K. 1974. Five new species and a new genus of alepisauroid fishes of the Scopelarchidae (Pisces: Myctophiformes). Copeia 1974: 449–457. 

Johnson, R. K. 1974b. A revision of the alepisauroid family Scopelarchidae (Pisces: Myctophiformes). Fieldiana Zoology (Zoological Series) 66: i–ix, 1–249. 

Johnson, R. K. 1982. Fishes of the families Evermannellidae and Scopelarchidae: systematics, morphology, interrelationships, and zoogeography. Fieldiana Zoology (New Series) 12: i–xiii, 1–252.

Motomura, H., Last, P.R. & Yearsley, G.K. 2007. Scopelarchoides kreffti (Actinopterygii: Aulopiformes: Scopelarchidae) from off Tasmania, Australia: First Records from Outside the South Atlantic Ocean. Species Diversity 12: 9-15 

Post, A. 1990. Scopelarchidae, pp. 134–135. In: Gon, O. & Heemstra, P.C. (eds) 1990. Fishes of the Southern Ocean. Grahamstown : J.L.B. Smith Institute of Ichthyology 462 pp.

Stewart, A.L. 2015. Family Scopelarchidae. pp. 566-574 in Roberts, C.D., Stewart, A.L. & Struthers, C.D. The Fishes of New Zealand. Wellington : Te Papa Press Vol. 2 pp. 1-576.

Quick Facts


CAAB Code:37131006

Depth:600-1000 m

Habitat:Mesopelagic

Max Size:19 cm SL

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CAAB distribution map