Galaxias arcanus, Raadik, 2014

Raadik, Tarmo A., 2014, Fifteen from one: a revision of the Galaxias olidus Günther, 1866 complex (Teleostei, Galaxiidae) in south-eastern Australia recognises three previously described taxa and describes 12 new species, Zootaxa 3898 (1), pp. 1-198 : 37-48

Galaxias arcanus , new species

Riffle Galaxias

Tables 4 to 9, 12 to 14; Figs. 8 to 11

Galaxias olidus (non G. olidus Günther, 1866 )— Koehn, 1987: 3; Morison & Anderson, 1991 (partim); Lintermans, 1998: sites

36 and 47 (partim) and 57; Raadik et al., 2001: 115, 116–117 (partim), 122 (partim), 123, 124 (partim), 125, 126 (partim); Koehn, 2002 (partim); Pollino et al., 2004 (partim); Lintermans, 2007: 44 (partim).

Galaxias sp. nov.–Raadik, 2001: 785, top image p. 786.

Galaxias sp. 2 — Sowersby, 2007; Davies et al., 2008: 338; Gilligan et al., 2010: 7, Lieschke et al., 2013a,b.

Galaxias sp. 3 — Kuiter, 2013: 44.

Conforms to the allozymically defined and morphologically diagnosed taxon ‘RF’ of Adams et al. (2014), and ‘riffle’ of Raadik (2011).

Material Examined.

Holotype. NMV A.30568-3, 86.3 mm LCF (74.9 mm SL), female, Wheelers Creek, just upstream of bridge on Wheelers Creek Logging Road and junction with Zulu Creek , upstream of O’Hagens Campsite , south of Staceys Bridge , Victoria, 36° 32' 23”S 147° 49' 44”E, T.A. Raadik and J. Lyon, 1 April 2008.

Paratypes. NSW: AMS I.32711-002 (4), 50.3–71.2 mm LCF (44.7–62.6 mm SL), Murray River , off Murray River Road, just upstream from junction with Corryong Creek, upstream from Tintaldra, 36° 05' 23”S 147° 59' 00”E, M. Lintermans, 12 March 1992 ; NMV A.30464-1 (1) 81.7 mm LCF (74.5 mm SL), Murray River , 50 m upstream from The Poplars campsite at end of Limestone Creek Track, Alpine National Park, 36° 46' 42”S 148° 06' 25”E, T.A. Raadik and V. Caracher, 22 March 2005 . VIC: AMS I.44935-001 (3), 60.3–63.4 mm LCF (52.1–55.5 mm SL), NMV A.30393-5 (12), 56.3–77.3 mm LCF (50.0– 68.2 mm SL), Corryong Creek , at bridge on Briggs Gap Road, north-west of Corryong, 36° 10' 28”S 147° 51' 52”E, T.A. Raadik, 18 March 2002 ; NMV A.30420-1 (18), 55.3–77.7 mm LCF (48.3–67.7 mm SL), Corryong Creek , same location as NMV A.30393-5, T.A. Raadik, 11 September 2002 ; NMV A.30463-2 (3), 54.2–85.0 mm LCF (47.4–75.3 mm SL), Snowy Creek , behind hotel, Mitta Mitta township, 36° 32' 09”S 147° 22' 40”E, T.A. Raadik, 19 March 2002 ; AMS I.44923-001 (2), 62.3–66.3 mm LCF (54.2–58.4 mm SL) and NMV A.30568-1 (5), 60.3–79.8 mm LCF (52.5–70.0 mm SL), collected with holotype; AMS I.44933-001 (2), 69.7–71.9 mm LCF (61.6–62.8 mm SL), NMV A.30453-2 (6), 67.8–72.5 mm LCF (59.0– 63.8 mm SL) and SAMA F.12142 (2), 64.8–67.5 mm LCF (56.7–59.7 mm SL), Kiewa River , east branch, at bridge on East Kiewa Road, north of Mount Beauty, 36° 43' 29”S 147° 10' 46”E, T.A. Raadik, 20 March 2002 ; AMS I.44934-001 (3), 58.5–63.8 mm LCF (51.1–55.4 mm SL), and NMV A.30462-2 (12), 57.1–65.4 mm LCF (50.0– 57.6 mm SL), Ovens River , off end of track in Braithwaite Plantation, downstream of Porepunkah, 36° 40' 54”S 146° 52' 46”E, T.A. Raadik, 21 March 2002 ; NMV A.30456-2 (5), 58.3–64.6 mm LCF (50.4–56.3 mm SL), Ovens River , at Nimmo Bridge on Buffalo River Road, Myrtleford, 36° 34' 09”S 146° 42' 57”E, T.A. Raadik, 26 June 2002 ; NMV A.30457-2 (4), 59.9–80.3 mm LCF (51.6–71.3 mm SL), Acheron River , at bridge on Glendale Lane , between Taggerty and Buxton, 37° 21' 10”S 145° 42' 25”E, T.A. Raadik and B. Cant, 22 May 2001 ; NMV A.30466-2 (5), 58.9–70.8 mm LCF (51.0– 61.7 mm SL), Little River , off Maroondah Highway at Taggerty, 37° 19' 26”S 145° 42' 46”E, T.A. Raadik and B. Cant, 25 May 2001 ; NMV A.30467-2 (4), 59.4–74.6 mm LCF (51.7–66.6 mm SL), Little River , at bridge on Cathedral Lane, south-east of Taggerty, 37° 20' 05”S 145° 44' 28”E, T.A. Raadik and B. Cant, 23 May 2001 .

Non-type material. NSW: AMS I.32711-006 (6), 41.0– 45.3 mm LCF (36.1–39.8 mm SL), Murray River , collected with AMS I.32711-002; NMV A.30440-1 (4), 46.6–71.6 mm LCF (41.2–63.7 mm SL), Murray River , Clarke Lagoon Reserve, downstream from Tintaldra, 36° 01' 29”S 147° 54' 49”E, TAR, 18 March 2002 . VIC: NMNZ P.045755 (3), 55.8–59.0 mm LCF (49.6–52.1 mm SL), NMV A.30393-4 (37), 36.7–56.3 mm LCF (32.1–48.6 mm SL) and SAMA F.12143 (3), 54.3–56.4 mm LCF (48.0– 49.9 mm SL), Corryong Creek , collected with NMV A.30393-5; NMV A.30420-3 (4), 53.2–57.0 mm LCF (45.9–50.1 mm SL) and TMAG D.3833 to 5 (3), 57.2–59.5 mm LCF (49.2–52.3 mm SL), Corryong Creek, same location as NMV A.30393-5, TAR, 11 September 2002 ; NMV A.30430-1 (10), 49.5–67.3 mm LCF (43.2–58.7 mm SL), Mitta Mitta River , caravan park of Omeo Highway, Mitta Mitta, 36° 32' 12”S 147° 22' 08”E, TAR, 21 June 1992 ; NMV A.30474-1 (4), 54.5–71.3 mm LCF (48.5–62.0 mm SL), Nariel Creek , Stacey Bridge on Benambra / Corryong Road, A.F. Baxter and S. Vallis, 7 March 1978 ; NMV A.30439-1 (4), 67.2–83.3 mm LCF (58.7–73.7 mm SL), Simpsons Creek , Grapolite Gully Track, east of Carmody’s Road, 36° 23' 48”S 147° 47' 04”E, J. Lieschke, 30 March 2005 ; NMV A.30463-1 (7), 40.5–53.4 mm LCF (35.5–46.0 mm SL), Snowy Creek collected with NMV A.30463-2; NMV A.30446-1 (3), 50.2–63.9 mm LCF (44.2–55.6 mm SL), Snowy Creek , off Omeo Highway , 6.6 km upstream from junction with Mitta Mitta River, south-east of Mitta Mitta, 36° 33' 52”S 147° 24' 30”E, D.J. Harrington, 19 May 1992 ; NMV A.30422-1 (1), 67.7 mm LCF (59.0 mm SL), Snowy Creek , Lightning Creek track, south-east of Mitta Mitta, 36° 40' 55”S 147° 26' 38”E, TAR, 20 October 1997 ; NMV A.30458-1 (5), 50.6–63.8 mm LCF (43.9–55.5 mm SL), Snowy Creek , same location as NMV A.30422-1, TAR, 19 March 2002 ; NMV A.30529-1 (1), 56.3 mm LCF (49.0 mm SL), Snowy Creek , west branch, West Branch Track, south-west of Granite Flat, 36° 36' 42”S 147° 22' 38”E, D. Stoessel, 12 March 2008 ; NMV A.30568-2 (13), 40.2–59.3 mm LCF (35.0– 51.6 mm SL), Wheelers Creek , collected with holotype; NMV A.30426-1 (2), 52.4–78.7 mm SL (46.1–67.0 mm SL), Zulu Creek, Zulu Creek Track, 36° 32' 25”S 147° 49' 44”E, JPO, 21 May 1997 ; NMV A.30451-1 (3), 60.9–62.4 mm LCF (53.6–54.6 mm SL), Kiewa River , east branch, East Kiewa ( Damm's ) Road, north of Mount Beauty, 36° 43' 28”S 147° 10' 46”E, JPO, 24 February 1998 ; NMV A.30450-1 (3), 48.2–60.8 mm LCF (42.3–53.2 mm SL), Kiewa River , Ang’s tobacco farm, off Damm’s Road, north of Mount Beauty, 36° 42' 52”S 147° 09' 29”E, JPO, 25 February 1998 ; NMV unregistered (4), 63.7–74.4 mm LCF (56.0– 66.2 mm SL), Kiewa River , same location as NMV A.30450-1, P.S. Fairbrother and W. Koster, 6 March 2007 ; NMV A.30453-1 (30), 39.9–59.2 mm LCF (34.8–51.6 mm SL), Kiewa River east branch, collected with NMV A.30453-2; NMV A.8933 (5), 70.9–78.8 mm LCF (63.7–69.8 mm SL), Buckland River, east branch, off Buckland River Road, 36° 52' 31”S 146° 52' 19”E, A.F. Baxter and S. Vallis, 27 March 1990 ; NMV A.30537-1 (6), 37.8–68.5 mm LCF (33.6–60.3 mm SL), Buckland River , track off Buckland River Road, upstream from Buckland, 36° 50' 23”S 146° 51' 09”E, R.J. Strongman, 16 January 1996 ; NMV A.30425-1 (2), 55.0–59.0 mm LCF (48.5–52.2 mm SL), Buffalo River , at junction with Dandongadale River, 36° 47' 42”S 146° 39' 53”E, D.J. Harrington, 31 March 1992 ; NMV A.30434-1 (7), 56.4–75.5 mm LCF (49.7–67.5 mm SL), German Creek , off Tawonga Gap Road, east from Germantown, 36° 43' 47”S 147° 02' 56”E, A.F. Baxter and S. Vallis, 8 February 1994 ; NMV A.30449-1 (1), 51.0 mm LCF (43.5 mm SL), King River , Burnt Track , Pineapple Flat, north-east from Mt. Stirling, 37° 03' 58”S 146° 29' 54”E, JPO, 18 April 1997 ; NMV A.30421-1 (2), 70.3–77.9 mm LCF (61.4–68.1 mm SL), King River , Speculation Road , west of Mt. Speculation, Alpine National Park, 37° 06' 12”S 146° 34' 23”E, P. Tinkler, 22 February 2007 ; NMV A.30469-1 (11), 45.2–63.0 mm LCF (39.6–55.0 mm SL), King River , at old bridge, Cheshunt, 36° 47' 51”S 146° 25' 33”E, TAR, 17 May 2001 ; NMV A.30462-1 (15), 33.9–56.3 mm LCF (29.5–48.9 mm SL), Ovens River , collected with NMV A.30462-2; NMV A.30456-1 (10), 44.8–56.2 mm LCF (38.2–49.0 mm SL), Ovens River, collected with NMV A.30456-2; NMV A.30423-1 (7), 46.5–64.0 mm LCF (40.3–56.0 mm SL), Ovens River, same location as NMV A.30462-2, B. Zampatti, 23 February 2000 ; NMV A.30454-1 (10), 51.9–70.5 mm LCF (45.6–61.3 mm SL), Ovens River , same location as NMV A.30462-2, B. Zampatti, 4 March 2002 ; NMV A.30424-1 (4), 49.9–70.9 mm LCF (44.0– 62.1 mm SL), Rose River , off Rose River Road upstream of junction with Dandongadale River, 36° 48' 20”S 146° 37' 43”E, D.J. Harrington, 19 March 1992 ; NMV A.30457-1 (10), 36.6–54.1 mm LCF (31.5–47.5 mm SL), Acheron River , collected with NMV A.30457-2; NMV A.8197 (1), 64.8 mm LCF (56.9 mm SL), Acheron River, Taggerty, 37° 19' 15”S 145° 42' 41”E, P.S. Lake, April 1985 ; NMV A.9246 (1), 52.2 mm LCF (45.1 mm SL), and NMV A.8136 (1), 49.8 mm LCF (43.0 mm SL), Acheron River , 4 km north of Taggerty off Keenes Road, 37° 17' 08”S 145° 43' 04”E, P.S. Lake, November 1985 ; NMV A.1040 (2), 64.9–72.7 mm LCF (56.6–63.6 mm SL), Acheron River , T.J. Doeg, 17 October 1988 ; NMV A.30480-1 (15), 62.0– 90.8 mm LCF (55.3–80.1 mm SL), Big River , Reefton Logging Road, 37° 31' 16”S 146° 04' 42”E, D.J. Harrington, 28 February 1990 ; NMV A.30444-1 (3), 55.8–63.2 mm LCF (48.9–55.9 mm SL), Black River , River Track, 37° 31' 13”S 146° 18' 38”E, JPO, 9 December 1997 ; NMV A.30447-2 (3), 73.8–80.2 mm LCF (66.0– 71.5 mm SL), Goulburn River , east of Acheron, 37° 14' 28”S 145° 44' 59”E, R.J. Strongman, 7 May 1996 ; NMV A.30478-1 (2), 71.3–74.2 mm LCF (62.3–65.5 mm SL), and NMV A.30471-1 (4), 50.3–55.5 mm LCF (43.9–48.6 mm SL), Howqua River , off Howqua Road, upstream from Howqua, 37° 13' 38”S 146° 12' 35”E, A.F. Baxter and S. Vallis, 18 April 1978 ; NMV A.30526-1 (6), 70.1–86.9 mm LCF (62.6–77.7 mm SL), Howqua River , Tunnel Bend, upstream from Sheepyard Flat, 37° 11' 16”S 146° 22' 12”E, R.J. Strongman, 31 January 1996 ; NMV A.30433-1 (6), 70.1–86.9 mm LCF (62.2–77.7 mm SL), Howqua River , Tobacco Flat, 37° 13' 04”S 146° 18' 24”E, R.J. Strongman, 31 January 1996 ; NMV A.30532-1 (12), Howqua River , same location as NMV A.30433-1, R.J. Strongman, 16 January 2001 ; NMV A.14018 (1), 75.8 mm LCF (66.9 mm SL), Jamieson River , upstream from Jamieson, 37° 17' 31”S 146° 10' 31”E, R. Gibb, 18 April 1978 ; NMV A.30535-1 (1), 55.9 mm LCF (49.1 mm SL), Jamieson River , south branch, off Silvermine Spur Road, 37° 20' 36”S 146° 22' 21”E, JPO, 16 April 1997 ; NMV A.30466-1 (5), 35.1–35.4 mm LCF (31.1–48.7 mm SL), Little River , collected with NMV A.30466-2; NMV A.30467-1 (3), 32.1–44.6 mm LCF (27.9–39.5 mm SL), Little River, collected with NMV A.30467-2; NMV A.30452-1 (1), 59.1 mm LCF (51.4 mm SL), Little River, same location as NMV A.30467-2, J. Lieschke, 2 March 1999 ; NMV A.30648-2 (5), 41.5–53.6 mm LCF (36.3–47.2 mm SL), Little River , in reserve, upstream of Maroondah Highway, Taggerty, 37° 19' 27”S 145° 42' 48”E, TAR, 18 December 2001 ; NMV A.30472-1 (2), 89.2–98.1 mm LCF (78.6–87.2 mm SL), Rubicon River , access track, Rubicon, 37° 17' 23”S 145° 49' 34”E, J. Lieschke, 1 March 2000 ; NMV A.30477-1 (3), 53.9–80.9 mm LCF (47.3–71.2 mm SL), Rubicon River , same location as NMV A.30472-1, P. Close and G. Aland, March 2001 ; NMV A.30432-1 (3), 46.7–56.8 mm LCF (39.9–48.2 mm SL), Rubicon River , same location as NMV A.30472-1, TAR, 24 May 2001 ; NMV A.30470-1 (13), 57.9–72.9 mm LCF (51.0–65.0 mm SL), Rubicon River , ‘ Tumbling Waters’ picnic area, south of Thornton, 37° 16' 47”S 145° 47' 58”E, R.J. Strongman, 22 February 2002 ; NMV A.30431-1 (2), 68.0– 89.9 mm LCF (60.4–80.4 mm SL), Snobs Creek , Snobs Creek Hatchery, 37° 15' 49”S 145° 52' 24”E, J. Douglas, 17 March 1995 ; NMV A.30539-1 (1), 53.1 mm LCF (45.4 mm SL), Snobs Creek , Goulburn Valley Highway, 37° 15' 32”S 145° 52' 24”E, TAR, 29 March 2001 ; NMV A.30455-1 (2), 44.5–73.3 mm LCF (38.5–64.5 mm SL), Steavenson River , downstream from Buxton / Marysville Road, north of Marysville, 37° 27' 53”S 145° 44' 01”E, TAR, 22 May 2001 ; NMV A.30436-1 (2), 68.8–79.9 mm LCF (60.7–70.9 mm SL), Steavenson River , upstream of Buxton / Marysville Road, north of Marysville, 37° 28' 56”S 145° 45' 05”E, TAR, 22 May 2001 ; NMV A.30438-1 (1), 72.0 mm LCF (63.9 mm SL), Steavenson River , at Buxton / Marysville Road, north of Marysville, 37° 27' 55”S 145° 44' 08”E, J. Lieschke, 2 October 2002 .

Additional material examined (not measured): see Appendix 5.

Diagnosis. Galaxias arcanus sp. nov. is one of the most morphologically distinctive species in the Galaxias olidus complex and differs from all others by a combination of the following characters: shallow body with a straight ventral profile; long and shallow caudal peduncle, the peduncle length greater than the caudal fin length; caudal peduncle flanges poorly developed; a distinctive snout which extends anteriorly from the thick and fleshy upper jaw as a fleshy protrubence, bulbous in lateral profile; nostrils of moderate length, usually not visible from ventral view; subterminal mouth and lower jaw 81.5 (72.9–99.4) % of length of upper jaw; most anterior tip of snout level with about lower 0.3 of eye diameter; head wide and shallow; short PrePel, PecPel and PoHL dimensions; large, ventrally oriented pectoral and pelvic fins (12.1–16.7 and 9.2–13.0 % SL respectively); low mean vertebral count of 51, though range broad (47–55); 0–1 pyloric caecae, short (1.0 % SL) and wide when present; gill rakers of moderate length, thin and sharply pointed; anal fin origin usually under 0.4 distance posteriorly along dorsal fin base; distinctive cryptic colouration; and, lack of black bars along lateral line.

Description. As for the genus and members of the Galaxias olidus complex, except as indicated below, based on 92 specimens, 44.7–75.3 mm SL, and 250 additional, non-type specimens for meristics. See Tables 4 to 9 for frequencies of meristic values and Table 13 for a summary of meristic variation. Segmented dorsal fin rays 9 (8–10), of these 7 (6–8) branched and 2 (1–3*) unbranched; segmented anal fin rays 11 (10–12), of these 9 (7–9; [8*]) branched and 2 (2–3*) unbranched; caudal fin rays 16 (15–16); segmented pectoral fin rays 14 (13–15*), of these 12 (11–13*) branched and 2 (1–2) unbranched; pelvic fin rays 7, of these 6 branched and one unbranched; gill raker total count (lower limb and upper limb) 13 (11–16), lower arch with 9 (8–11) and 3 (3–5; [4*]) on upper, variation on first gill arch 6+3 (1), 7+3 (2), 8+2 (2), 8+3 (37), 8+4 (11), 8+5 (1), 9+2 (6), 9+3 (81), 9+4 (63*), 9+5 (5), 10+2 (4), 10+3 (34), 10+4 (53), 10+5 (7), 11+3 (4), 11+4 (8), 11+5 (2), 11+6 (1); vertebrae 51 (50–53; holotype 52); 0–1* pyloric caecae on stomach.

See Table 14 for comparative value ranges of morphometric characters. Body slender and elongate, body depth through pectoral fin base 8.1 (6.8–9.7) in SL, slightly laterally compressed and dorsal midline sometimes flattened anteriorly between pelvic and pectoral fin bases, depth through pectoral base 1.1 (1.0–1.2) that through vent, dorsal profile evenly arched from snout to dorsal fin, ventral profile straight from snout to anal fin, generally flat anterior to pelvic fins; belly only slightly deepened in maturing individuals, body tapering back to a long, 6.2 (5.3–12.8) in SL, and shallow, 14.1 (8.6–16.7) in SL, caudal peduncle, the peduncle depth about 2.3 in its length; accessory lateral line present. Head of moderate length, 4.6 (4.2–5.0) in SL, and shorter (0.9) than the PelAn distance, shallow and wide, 2.8 (2.3–3.5) and 1.6 (1.4–1.8) in HL respectively, distinctly wider than deep (depth 1.7 (1.6–1.9) in HW), upper profile of head curved, slightly depressed, ventral straight, lateral profile wedge-shaped; eyes moderate, 5.5 (4.8–6.9) in HL and 2.0– 2.1 in HD, situated high on head at or slightly protruding above dorsal head profile, interorbital flat, of moderate width, 2.6 (2.4–3.0) in HL and 2.1 (2.0–2.3) times ED; cheeks expanded below eyes, eye profiles usually visible laterally from ventral view, less so in larger individuals; snout of moderate length, 3.4 (3.0–4.1) in HL and 1.6 (1.2–2.1) times ED, extending anteriorly from jaw as a fleshy protrubence and distinctly narrow anteriorly from in front of eyes in dorsal view, lateral profile dorsally bulbous and anteriorly rounded to bluntly pointed; post-orbital head length short, 1.9 (1.7–2.2) in HL; nostrils moderately long, not visible anterio-laterally from ventral view; mouth subterminal, moderately long, 2.6 (2.3–3.0) in HL, posterior extent reaching back to under about 0.5 ED and 0.6 (0.4–1.0) ED below ventral margin of eye, appears subterminal due to extended snout, cleft slightly oblique, most anterior tip of upper lip level with about 0.3 of ED above ventral margin of eye, gape of moderate width, 2.6 (2.2–3.1) in HL, width about equal to length of upper jaw and 1.6 (1.5–1.7) in HW. Jaws distinctly subequal, lower 0.8 (0.7–0.9) of UJL, upper jaw strongly expanded into a thick, fleshy lip ( Figs. 8c,d , and 9a,b ), thickening extending laterally from premaxilla onto maxilla and broader than snout in anterior view, lower also fleshy but less so, and distinctly wider than deep. Fleshy anterior extension of upper lip increasing anterior extension of snout forward of jaw, no distinct fold separating extent of upper jaw from snout. Pyloric caecae short, usually 1.0 % SL (0.4–2.6 %), wide; gill rakers of moderate length, thin and sharply pointed.

except for LCF and SL).

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Median fins relatively thin and slightly fleshy at bases, paired fins less so, with thickening extending distally over 0.2–0.3 of fin area, extending farther between fin rays, dorsal and anal fin bases of moderate length, dorsal base usually 0.9 in length of anal base, fins of moderate length, anal fin slightly longer, 2nd or 3rd branched ray usually longest, distal tip rounded but posterior margin of fin distinctively straight or slightly convex; anal fin origin usually under 0.43 (0.18–0.66) distance posteriorly along dorsal fin base. Pelvic fins relatively long, 8.5 (7.7–10.8) in SL, paddle-shaped, usually 0.8 (0.7–1.0) of pectoral fin length inserted at about mid-point of standard length and extending about 0.5 distance to anal fin base; pectoral fin large, long and rounded to paddle-shaped, 6.9 (6.0–8.3) in SL, usually extending just over 0.5 distance to pelvic fin base, low on body with dorsal end of fin base level with posterior extent of mouth, lamina of paired fins oriented ventrally, raised lamellae usually present on ventral surface of rays, usually weakly to moderately developed though occasionally strong. Caudal fin of moderate length, 7.1 (6.2–8.5) in SL, emarginate, distinctly shorter 1.2 (0.9–1.4) than caudal peduncle, vertical width of expanded rays usually greater than body depth through pectoral fin base, flanges low and moderately developed, short, usually extending about 0.6–0.9 distance along caudal peduncle to distal margin of rays of adpressed anal fin, occasionally reaching rays.

Size. Recorded to 98 mm LCF and 6 g; commonly to 60–75 mm LCF.

Colour in life. Body overall olive-brown to beige, becoming silvery white on belly, overlain by dark grey, dark brown or almost black, irregularly shaped blotches forming patches or usually coalescing to form irregular shaped bands or marbling, often overlain with shading formed by minute, closely spaced, dark grey spots. Pattern extends over dorsal and lateral surfaces of trunk, caudal peduncle and head, extending onto fin bases and sometimes onto the underside of the head. Head usually darker, with snout and lips often quite dark grey. Trunk with broad, relatively diffuse mid-lateral horizontal band of copper and gold flecks extending from above pectoral fin base onto caudal peduncle; snout and upper lip sometimes with copper and gold flecks, also diffusely scattered over head; sometimes a thin double band of gold flecks mid dorsally, extending from nape to base of dorsal fin and often onto caudal peduncle. Gill cover olive-brown with a small gold patch; fins translucent, yellowish brown, sometimes greyish; iris coppery gold. When stressed, adults can become almost uniformly dark grey to black (see upper image on page 786 in Raadik 2001); occasionally adults may lack dark body pattern.

Juvenile colouration distinct from that of adults ( Fig. 9c ), with paler and less profuse dark patterning over body and head, little body shading, larger gold patch on gill cover, and trunk pattern absent from latero-ventral region. See below for more detailed comments on body pattern.

Colour of preserved material. Base colour of head and body pale lemon-yellow, tan or creamy yellow. Dorsal surface of head and trunk usually overall dark brown, dark grey or black, darkest mid-dorsally, on body fading down sides and occasionally on ventro-lateral surface as light duskiness, belly light cream to creamy yellow, lacking duskiness. Bold cryptic patterning of large, irregularly shaped joined blotches interspersed by contrasting light pale cream spots or thin, separated or connected, irregularly-shaped narrow bands, darker on top and fading down sides, extending over entire dorsal and lateral surface of head and body, absent from ventral surface. Dorsal portion of nape, head, snout, and anterior-dorsal portion of upper jaw with dark grey colouration, becoming paler laterally and extending onto lower jaw, below eyes, cheeks and gill covers, ventral surface of head sometimes also dusky and with patches of fine black spots. Duskiness produced by profuse, very fine pale black spotting. Often minute black spotting also inside operculum and on base of gill filaments.

Colour pattern of juveniles creamy yellow to light tan base colour with dorsal surface and top of head covered with relatively large irregular, discrete or connected dark brown blotches composed of dense fine spots, extending down sides to near ventral surface and onto gill covers and snout, snout cheeks and upper and lower lips with dusky hue.

Eye black, pupil translucent pale orange-yellow or brownish yellow. Teeth translucent yellow to pale orange–yellow, tips orange to orange–red; gill rakers creamy white to pale yellow. Fins generally dusky pale yellow, becoming more translucent on posterior margins, fleshy bases of pelvic and pectoral fins cream. Fin rays translucent, external edges of rays highlighted with very fine black lines, first few rays generally darker; duskiness and patches of fine black spots on dorsal, anal and pectoral fin bases. Base of caudal fin usually with narrow, vertical, diffuse and dark to relatively pale grey band.

Etymology. From the Latin arcanus , meaning cryptic, secret, mysterious, in reference to the cryptic habitat occupied by this species (amongst boulder and cobbles on the stream bed), and its cryptic colouration. Commonly referred to as the ‘Riffle Galaxias’.

Genetics. Allozyme and mtDNA analysis of this species can be found in Adams et al. (2014; taxon code RF). Diagnostic allozyme loci (6–13) between this taxon and the other species in the Galaxias olidus complex are provided in Table 12. Two genetically distinct subpopulations were identified, with fish in the Goulburn River basin differing by one diagnostic allozyme locus from those in the Upper Murray to the Ovens River basins ( Raadik 2011). Morphological variation between these subpopulations was not investigated.

Distribution. See Fig. 11 . Restricted to a thin band on the north of the Great Dividing Range in north-eastern Victoria, including the upper Murray River from near its headwaters and extending westward to the Goulburn River system, at an elevation of between 150–880 m asl. Not known as yet from the Broken River system but may be present, but restricted in range, to the cooler and faster-flowing upland reaches. Currently not recorded from the Murray River downstream from about Albury, or from tributaries of the upper Murray River in NSW. May be restricted in range to steeper-gradient streams in foothill to upland reaches by specific habitat requirements, such as diverse substrates and fast-flows.

Sympatry. Found with other members of the Galaxias olidus complex, primarily with G. olidus and Galaxias . oliros sp. nov, and considered to have been sympatric with Galaxias fuscus in the Goulburn River system, before alien trout substantially altered distributional patterns. Also found with Galaxias rostratus at the lower elevations within its range, and with Galaxias brevipinnis which has colonised the upper Murray and tributaries.

Habitat. Recorded from cold to relatively cool, clear water in flowing creeks to large rivers (1.0–20.0 m average width), usually in shallow (0.1–0.4 m average depth), fast-flowing and high energy riffles and runs ( Fig. 10c ), though juveniles have been recorded moving upstream through slow water along the shallow edges of pools. Substrate in riffles and runs consists predominantly of a complex of abundant cobbles and pebbles, with smaller amounts of bedrock, boulder, gravel and coarse sand. Fish are typically found within the diverse substrate, either amongst or under rocks on the stream bed, or deeper in the interstitial spaces of the substratum. Usually not associated with aquatic vegetation, but have been found amongst small and large timber debris.

General Biology. Confined to freshwater. Collected at a density ranging from <0.01–0.80 fish/m 2 though, as individuals are usually hidden amongst or within the substrate in fast-flowing areas ( Fig. 10c ) which are difficult to sample, these values are considered a gross underestimate of relative abundance. Usually collected with the native species Two-spined Blackfish ( Gadopsis bispinosus ), Galaxias olidus s.s., Murray Spiny Crayfish ( Euastacus armatus ), Alpine Spiny Crayfish ( Euastacus crassus ) and shrimp ( Atyidae ) and including the alien species Brown Trout and Rainbow Trout ( Oncorhynchus mykiss ), and less often with the native species Obscure Galaxias ( Galaxias oliros sp. nov.) and Broadfinned Galaxias . Spawning period is probably spring to summer (October–December and possibly extending into January): adult fish collected from Corryong Creek in the Upper Murray system in early November, and from the Acheron and Little rivers (Goulburn River system) in mid- October to mid-November, were ripe to running ripe, whilst all fish collected post mid-December were at earlier stages of development and usually with their body cavity full of fat deposits through January to March; juvenile 0+ age fish <38 mm LCF have been recorded in all months from December to May; and, the smallest 0+ age individuals recorded have been 16.7 mm LCF in early February (Ovens River system) and 27.9 mm LCF in late May (Goulburn River system). Males mature earlier, with a ripe individual recorded from the Goulburn River in early May (late autumn) and a running ripe male from the Ovens River in late June 2002. Confusingly, some females have been recorded as running ripe in late June 1992 in the upper Murray catchment, and almost ripe in the Goulburn River system in May 2001. The smallest fish which could be reliably sexed were a female at 49.5 mm LCF (Corryong Creek, Upper Murray) and a male at 41.5 mm LCF (Little River, Goulburn River system).

Adults usually solitary; juveniles and younger adults observed in loose shoals of 50+ individuals, moving upstream during the day in shallow, slow-flowing water along the edge of pools, between riffle habitats: fish 38–66 mm LCF recorded moving upstream in the Acheron River and individuals <50 mm LCF observed along the edge in the Steavenson River (Goulburn system) in late May 2001; and, individuals 49–67 mm LCF collected moving upstream along the edge of a long pool in the Mitta Mitta River (upper Murray system) in late June 2002. This suggests active upstream dispersal by younger age-classes of fish. Individuals from the Steavenson River, downstream from Marysville, found with cysts, possibly trematode metacercariae, embedded in the skin of the trunk and fins. Also see Sowersby (2007).

Variation. As noted above, the species is extremely variable in colour pattern, differing between juveniles and adults (cf. Figs. 9c and 10a ). Colour and pattern changes are also evident between populations, and between individuals within populations, and can also rapidly change from the usual strongly patterned colouration to a plain light grey or almost black, depending on the stress level of individual fish. Also exhibits a relatively high amount of variation in meristic characters across its range, particularly in dorsal, anal and pectoral fin ray number, and number of gill rakers and vertebrae.

Remarks. First recognized as an unidentified species in 1986 when a specimen, collected from a riffle in the Acheron River during an aquatic macroinvertebrate ‘kick’ sample, was received by the author. No additional specimens were found in museum collections, except in the unregistered wet specimen collection at the Arthur Rylah Institute in Victoria, which were subsequently deposited at the Museum Victoria (NMV A.10017, NMV A.30474-1). These represented the first recorded collections of the species, in early March 1978. The high-energy habitat usually occupied by Galaxias arcanus , and its crypto-benthic nature, may explain its late discovery.

The unique morphology of Galaxias arcanus , which includes a straight ventral profile, long, low caudal peduncle, a downturned, subterminal mouth and a bulbous nose, suggests an adaptation to a benthic existence within a diverse substrate in a high energy environment. In particular, the subterminal mouth and straight ventral profile may be an advantage for feeding off the substrate or rocks, the bulbous extension to the snout may play a sensory role in prey detection within the substrate, and the overall low body profile may enable easier movement amongst the substrate and in keeping in the quieter water on the stream bed just below the level of fast or turbulent flow.

Galaxias arcanus often lie in a characteristic manner when motionless on the substrate, with the body slightly curved in the horizontal plane when viewed from above. They are also often found propped on the substrate (gravel, rock or timber), with the pectoral and pelvic fins expanded ventrally, supporting and raising the head and front of the body higher than the tail ( Fig. 9c,d ), or propping on the pelvic, pectoral and anal fins. In this position the head can be moved slightly laterally or tilted to some extent downwards, presumably to look for prey. Often found in streams with high densities of alien trout ( Salmo trutta and Oncorhynchus mykiss ), they are presumably able to avoid predation by occupying high energy riffle habitats which may be marginal for trout, and also by their disruptive colouration and remaining hidden amongst habitat on or within the stream bed. Flow regulation, whereby riffle areas can be dewatered or, alternatively, submerged for longer periods than during natural floods, may be a key threat to this species by reducing habitat availability and allowing predators to gain access when riffles are drowned out.

The use of interstitial spaces within the substrate of the streambed may also act as refugia during times of low flow (sensu Dunn & O’Brien 2006) and also provides usable habitat in areas with very low flow. Galaxias arcanus were found within a bank of pebbles (30–50 mm in diameter), in Corryong Creek, which was covered by only 10 mm of water and they could not be depleted from a 2 m 2 area following 60 minutes of electrofishing: individuals kept emerging from amongst the pebbles on each successive pass.

Figures

FIGURE 8. Galaxias arcanus sp. nov. holotype, NMV A.30568-3, 86.3 mm LCF, Wheelers Creek, Wheelers Creek Logging Road, south of Stacey’s Bridge, Victoria: A) line drawing; B) image of preserved specimen (T.A. Raadik); and detail of ventral surface of C) head (T.A. Raadik), and D) jaws (R. Plant). Scale bar = 5 mm.

FIGURE 9. A–B: Anterior view of the unique snout of Galaxias arcanus sp. nov., A) jaws closed and B) jaws open, showing fleshy upper lip; C) juvenile colour pattern and propping; and, D) adult propping on a rock. (T.A. Raadik).

FIGURE 10. A) Galaxias arcanus sp. nov., adult, collected from type locality, ~ 85 mm LCF March 2008; B) Wheeler Creek, at type locality, 1 April 2008. Zulu Creek inflow on right; C) typical habitat of Galaxias arcanus, amongst cobbles in a fastflowing riffle, Steavenson River downstream from Marysville, 22 May 2001. (T.A. Raadik).

FIGURE 11. Distribution of Galaxias arcanus sp. nov. (black circles) and Galaxias fuscus (open circles). (river basins shown—refer to Fig. 1).