Melanotaenia sahulensis, Hammer & Allen & Martin & Adams & Unmack, 2019

Hammer, Michael P., Allen, Gerald R., Martin, Keith C., Adams, Mark & Unmack, Peter J., 2019, Two new species of dwarf rainbowfishes (Atheriniformes: Melanotaeniidae) from northern Australia and southern New Guinea, Zootaxa 4701 (3), pp. 201-234 : 218-224

Melanotaenia sahulensis sp. nov.

Sahul Rainbowfish

(figs 5 & 7; tables 4–5)

Melanotaenia maccullochi non Ogilby, 1915 — Allen (1981) (in part): 87 ( Fig. 5 Pahoturi River, and Fig. 6 Jardine River); Allen & Cross (1982) (in part): 52 (image page 30, Pahoturi River); Merrick & Schmida (1984) (in part): 164 (plate 140, Jardine River); Leggett & Merrick (1987) (in part): 142 (plate 64, Jardine River); Allen (1989) (in part): 98 (plate 28, Pahoturi River); Paxton et al. (1989) (in part): 350; Allen (1991) (in part): 91 (plate 5, no. 6); Allen (1995) (in part): 56 (images on cover and page 43, lower image page 31 “ PNG ” — captions reversed, page 124, PNG); Herbert & Peeters (1995) (in part): 51 (plate 58, Blue Valley Lagoon); Herbert et al. (1995) (in part): 18; Lundberg et al. (2000) (in part): 51 (Figure 26 bottom image); McGuigan et al. (2000) (in part): 715; Unmack (2001) (in part): 1061; Allen et al. (2002) (in part): 152 (image Skull Creek); Hitchcock (2002): 120; Johnson (2003) (in part): 143; Pusey et al. (2004) (in part): 242; Allen et al. (2006) (in part): 692; Allen et al. (2008) (in part): 92 (image of male, Sigabaduru and female, Bensbach River, PNG); Tappin (2010) (in part): 282 (images PNG, Skull Creek); Cook et al. (2012) (in part): 265; Hitchcock et al. (2012): 18; Unmack et al. (2013) (in part): 19; Aland (2014): 815 (image page 813); Graf et al. (2015) (in part): 870; Schmida (2015) (in part): 86 (images Skull Creek, Burster Creek, Moa Island); Pusey et al. (2017) (in part): 39 (point data distribution map).

Material examined (267 specimens, 13.4–48.4 mm SL) .

Holotype: WAM P.26757-001, male, 45.0 mm SL, Pahoturi River, Sigabadu (09° 14.75ʹS, 142° 44.05ʹE), <1.0 m, dip net, R. Moore, 28 September 1979 .

Paratypes: AMS I.21008-005, 105 specimens, 32.4–40.6 mm SL, Bamaga area (19 km NE) (10° 25.2ʹS, 142° 00ʹE), Queensland , seine, G. Webb, 2 September 1972 ; QM I.21792, 24.7 mm SL, Burster Creek (10° 54ʹS, 142° 20ʹE), Queensland , R. Leggett, 2 September 1985 ; QM I.27642, 13 specimens, 24.5–36.2 mm SL, Woomera Ck drainage (billabong), near Lockerbie (10° 52ʹS, 142° 28ʹE), Queensland , J. Short, 28 October 1990 ; QM I.38845, 5 specimens, 30.3–32.9 mm SL, creek on Kubin-St Paul Road, Moa Island (10° 12.5ʹS, 142° 16.4ʹE), Queensland , dip net, G. Aland, 23 March 2011 ; QM I.39247, 7 specimens, 16.1–29.4 mm SL, Scrubby Creek, Silver Plains (13° 44.7ʹS, 143° 28.5ʹE), Queensland , electrofisher, P. Graham, B. Herbert & J. Peeters (QFS), 10 June 1993 ; QM I.39613, 32.9 mm SL, Sand dune lake, near Harmer Creek (11° 57.5ʹS, 142° 56.2ʹE), Queensland , electrofisher, Queensland Fisheries Service /CYPLUS, 29 October 1992 ; QM I.39862, 2 specimens, 23.4–28.1 mm SL, Harmer Creek tributary (11° 58.9ʹS, 142° 50.6ʹE), Queensland , Queensland Fisheries Service , 7 August 1993 ; QM I.39872, 25.3 mm SL, Blue Valley Lagoon, Cody Creek system (10° 50.3ʹS, 142° 28.2ʹE), Queensland , Queensland Fisheries Service , 15 August 1993 ; QM I.39886, 2 specimens, 23.2–25.1 mm SL, Harmer Creek , Shelburne Bay (11° 58.7ʹS, 142° 53.4ʹE), Queensland , Queensland Fisheries Service , 8 August 1993 ; WAM P.26555-001, 11 specimens, 31.4– 40.1 mm SL, Bamaga area (19 km NE) (10°53ʹS, 142°24ʹE), Queensland , seine, G. Webb, 2 September 1972 ; WAM P.26757-002, female, 38.7 mm SL, collected with holotype ; WAM P.27818-001, 43 specimens, 20.6–31.5 mm SL, Bensbach River, side billabong near Lodge (08°51ʹS, 141°13ʹE), seine, G. Allen & J. Paska, 29 September 1982 ; WAM P.28149-002, 9 specimens, 23.3–32.0 mm SL, small tributary of Fly River, Oboe (07°36ʹS, 141°19ʹE), seine, G. Allen & D. Balloch, 15 September 1983 ; WAM P.31342-008, 2 specimens, 25.3–27.2 mm SL, Bensbach River, vicinity of Lodge (08°50ʹS, 141°14ʹE), fine mesh net, G. Hitchcock, 1 May 1997 .

Other material examined: AMS I.21237-027, 19 mm SL, Creek before Jardine River (11° 09ʹS, 142° 22.2ʹE), D. Hoese & G. Allen, 1979 ; AMS I.21247-003, 29 specimens, 17–25 mm SL, Bridge Creek, Jardine River system (11° 13.2ʹS, 142° 22.8ʹE), D. Hoese, 1979 ; NTM S.17828-001, 5 specimens, 28.2–41.1 mm SL, Kia Creek, Moa Island (captive stock) (10° 11.0ʹS, 142° 17.0ʹE), B. Hansen, 2012 ; NTM S.18153-001, 7 specimens, 30.1–48.4 mm SL, Skull Creek, near Bamaga (captive stock) (10° 57.6ʹS, 142° 19.8ʹE), D. Wilson, 2017 ; QM I.17766, 10 specimens, 18.4–21.8 mm SL, Bridge Creek, Jardine River system (11° 14ʹS, 142° 22ʹE), D. Hoese, 1979 ; QM I.21420, 47 specimens, 13.4–20.9 mm SL, Conical Hill Lake, Shelburne Bay (11° 56ʹS, 143° 08ʹE), P. Saenger, 1984 ; QM I.21801, 5 specimens, 20.1–22.4 mm SL, Bamaga Rd , creek north of Sanamere Lagoon (11° 07ʹS, 142° 22ʹE), R. Leggett, 1985 ; QM I.38290, 4 specimens, 25.1–27.0 mm SL, Kai Creek, Moa Island (10° 11ʹS, 142° 17ʹE), G. Aland, 2008 ; QM I.39877, 6 specimens, 24.1–25.9 mm SL, Creek at Temple Bay (12° 14.9ʹS, 143° 04.8ʹE), Queensland Fisheries Service , 1993 ; SMF 12636 , 4 specimens, 28.8–31.2 mm SL, Ditches at Merauke (08° 28ʹS, 140° 20ʹE), A. Werner & E. Frech, 1973 ; WAM P.26381-004, 1 specimen, 22 mm SL, Jardine River , south of crossing (11°10ʹS, 142°22ʹE), G. Allen & party, 1978 ; WAM P.26717-019, 3 specimens, 18–20 mm SL, Small tributary of Jardine River (11°09ʹS, 142°22ʹE), G. Allen & D. Hoese, 1979 ; WAM P.26719-005, 21 specimens, 21–29 mm SL, Bridge Creek, Cape York Road crossing (11°13ʹS, 142°23ʹE), G. Allen & D. Hoese, 1979 ; WAM P.26754-002, 3 specimens, 30–32 mm SL, Sadi Tiperrse Creek, Morehead (08°43ʹS, 141°39ʹE), R. Moore, 1973 ; WAM P.26754-003, 2 specimens, 31–32 mm SL, Sadi Tiperrse Creek, Morehead (08°43ʹS, 141°39ʹE), R. Moore, 1973 ; WAM P.26759-002, 2 specimens, 29–30 mm SL, Sadi Swamp, Morehead (08°42ʹS, 141°39ʹE), R. Moore, 1973 ; WAM P.26760-001, 24 mm SL, Bensbach River, Balamuk (08°57ʹS, 141°15ʹE), R. Moore, 1973 ; WAM P.26767-002, 11 specimens, 19–31 mm SL, Pahoturi River, Sigabadu swamps (09°20ʹS, 142°38ʹE), R. Moore, 1973 ; WAM P.27011-004, 19 mm SL, Creek south of Jardine River crossing (11°10ʹS, 142°22ʹE), G. Allen, 1978 ; WAM P.27816-002, 19 specimens, 18–28 mm SL, Balamuk River , Bensbach (08°54ʹS, 141°17ʹE), G. Allen, 1982 ; WAM P.27817-001, 11 specimens, 22–27 mm SL, Bensbach River, upstream of Lodge (08°51ʹS, 141°13ʹE), G. Allen & J. Paska, 1982 ; WAM P.27823-005, 3 specimens, 22–28 mm SL, Bensbach River, upstream of Lodge (08°53ʹS, 141°12ʹE), G. Allen & J. Paska, 1982.

Diagnosis: A species of Melanotaenia with well-contrasted dark lateral body stripes, distinguished by the following combination of characters: dorsal rays V–VII, I,7–10 (mode 8); total anal rays I,15–17 (mode 16); total procurrent caudal rays 12–16 (mode 13); lateral scales 31–34 (mode 33); cheek scales usually 9–12; total gill rakers on first arch 14–18; vertebrae 32–35 (mode 34); body very deep, greatest depth 2.6–3.7 (mean 3.0) in SL and wide, greatest width 1.7–2.9 (mean 2.0) in HL; maxilla relatively long 3.2–4.2 (mean 3.6) in HL; long predorsal distance 1.8–2.2 (mean 2.0) in SL; colour in life silver to grey body with a series of black lateral stripes; fins with distinct contrasting colour zones separated by a thick dark submarginal band, most pronounced in nuptial males.

Description: Based on 52 specimens, 15.6–48.4 mm SL; counts and measurements that appear in parentheses refer to the minimum and maximum values for the paratypes and other specimens where different from the holotype. Dorsal rays VI (V–VI, rarely VII) + I,8 (8–10, rarely 7; median 8); total anal rays I,16 (15–17, median 16); pectoral rays 13 (11–14); pelvic rays I,5; branched caudal rays 15; total procurrent caudal rays 14, 7 + 7 (12–16, 6–7, rarely 8 + 6–7); lateral scales 32 (31–34, median 33); transverse scales 9 (9–10, rarely 11); predorsal scales 14 (13–17); prepelvic scales 13 (12–17); cheek scales 12 (8–13, median 10); circumpeduncular scales 12 (12–14); gill rakers on first branchial arch 3+13 (2–4 + 12–15), total gill rakers on first arch 16 (14–18); total vertebrae 34 (32–35, median 34), precaudal vertebrae 19 (18–21, median 19). Meristic data are summarised in Table 4 .

Head length 3.6 (3.0–4.4) in SL; body depth 3.2 (2.6–3.7, mean 3.0) in SL; greatest width of body 2.2 (1.7–2.9, mean 2.0) in HL; snout length 3.5 (3.1–4.2, mean 3.6) in HL; eye diameter 3.0 (2.5–3.1) in HL; bony interorbital width 2.6 (2.3–2.9) in HL; depth of caudal peduncle 2.2 (1.8–2.7) in HL; length of caudal peduncle 1.5 (1.2–2.0) in HL.

Jaws about equal, oblique, premaxilla with an abrupt bend between the anterior horizontal portion and lateral part; maxilla ends below anterior edge of pupil or slightly anterior to this level; maxillary length 3.7 (3.2–4.2, mean 3.6) in HL; lips thin; teeth villiform to narrowly conical with slightly curved tips, extending on to outer surface of lips; teeth of upper jaw in about 3–5 irregular rows anteriorly, reduced to 1–2 rows posteriorly where clearly exposed when mouth closed; teeth in lower jaw in about 5–7 irregular rows anteriorly, reduced to a single row posteriorly.

Scales of body cycloid, relatively large, and arranged in regular horizontal rows; scales of midlateral row with small rounded to vertically elongate, shallow pit at centre, beginning at about 9 th– 12 th scale; row of small, truncated scales along bases of dorsal and anal fins, forming a low sheath on anal fin; no scales on membranous portions of fins except 3-6 transverse rows of small scales basally on caudal fin and cluster of several small scales (posteriormost largest) medially at base of pelvic fins; scale margins smooth or with slight crenulations; predorsal scales extending forward to about middle of interorbital space; preopercle (cheek) covered with 8 (8–13) scales; main body of operculum covered with 17 (9–25) scales and with single row of about 5–7 additional small scales on anterior limb (i.e. interopercular directly below lower edge of preopercle).

Predorsal distance 2.0 (1.8–2.2, mean 2.0) in SL (46.3–54.4, mean 49.8 as a % of SL); preanal distance 2.0 (1.6–2.0 in SL); prepelvic distance 2.7 (2.2–2.8) in SL; length of second dorsal fin base 5.7 (4.6–6.7, mean 5.5) in SL; length of anal fin base 3.1 (2.5–3.6) in SL.

First dorsal fin origin slightly anterior to about two-thirds pupil width in front of anal-fin origin; longest spine (usually third or fourth) of first dorsal fin 1.2 (1.0–2.2) in HL, its adpressed tip reaching to base of first to fourth soft ray of second dorsal fin in males and to about origin of second dorsal fin in females; longest (generally penultimate and 1-2 rays anterior to penultimate in male and first in female) rays of second dorsal fin 1.5 (1.2–2.3) in HL, adpressed posterior rays extending about two-thirds to full length of caudal peduncle in males to about one-half length in females and juveniles; longest (about 8 th or 9 th) anal ray 1.5 (1.1–2.5) in HL; pelvic fin tips when adpressed reaching to base of first or second soft anal ray in male and to anal fin origin or slightly beyond in female; length of pelvic fins 1.5 (1.2–2.2) in HL; length of pectoral fins 1.3 (1.1–1.6) in HL; length of caudal fin 1.4 (1.0– 1.5 in HL); caudal fin moderately forked, caudal concavity 2.4–6.9 in HL. A summary of proportional measurements is shown in Table 5 .

Colour in life: Generally silver-white to grey-brown on upper half of body, lower half of body white; seven or eight black body stripes, intensity typically increasing to full and bold as adults; head brownish grey, lips greyish sometimes with hint of yellow or orange; small square shaped red to orange mark on the upper operculum; iris silver; fins colourful, with distinct zonation in the dorsal and anal fins formed by a thick submarginal dark grey to black band; a thin area of colour above the band on the fin margins (white through orange, sometimes red) and below the black band typically an area of yellow to orange (figs 5 & 7). Colour intensifies in nuptial males with more prominent body stripes and bright fin coloration; sexual dimorphism is more obvious than in the other two species treated. A faint and sometimes brighter pale yellow to orange nape stripe can be ‘flashed’ by courting males or to a lesser degree by sparring males.

Colour in alcohol: Generally light brown to yellowish tan with 7–8 brown stripes on side of body as described above, although stripes sometimes faint and barely detectable, especially on long-preserved specimens; fins mainly translucent yellowish to whitish with dark bands on basal and distal portions of dorsal and anal fins frequently evident on male specimens ( Fig. 7 ).

Comparisons: Most easily separated from other Australian members of the maccullochi species group based on silver-grey body colour, bold and full body stripes as adults and tri-tone dorsal and anal fins (see full respective comparisons under other species).

Distribution and habitat: Museum records are displayed in Figure 1 , with M. sahulensis sp. nov. native to northeast Cape York Peninsula, Australia and southern central New Guinea. Locations include the northern tip and east coast of Cape York from the Jardine River, Bamaga area, Shelburne Bay area and around as far south as Scrubby Creek; Torres Strait (Moa Island); Papua New Guinea from the Pahoturi to Bensbach river systems including the mid-Fly; and Indonesia from the Merauke area. This patchy distribution comprises a broad range with regional habitat variation, but includes larger lateral floodplain systems and small swampy creeks including dune lakes, with dense cover. Cape York habitat generally consists of small streams and Pandanus swamps in sand-soil country. During non-flood periods the water is typically clear with ample cover in the form of either log debris or aquatic vegetation. The species also occurs in lily lagoons and is most frequently found in acid waters (pH 5.5–7.0). Information specific to this species has been merged and confused with M. maccullochi s.s. and to a lesser degree M. wilsoni sp. nov. The largest wild fish recorded in this study was 40.6 mm SL (49.7 mm TL: AM I.21008-005), and fish attributable to this form (e.g. Skull Creek) grow larger in captivity (around 50 mm SL or 60 mm TL: NTM S.18153-001).

Remarks: This species has been recognised as a distinct colour form since its discovery ( Allen 1981; Lundberg et al. 2000), with strong genetic divergence noted in mtDNA studies ( Cook et al. 2012; Unmack et al. 2013) and now supported with nuclear genetic markers. Somewhat subtle morphological characters support the striking colour and genetic divergence, with diagnosis apparently masked by large within site/region variability.

There appears to be regional variation in fin colour of this species, with the margin of the dorsal and anal fins, and to a lesser degree caudal and pelvic fins, ranging from white (e.g. Moa Island, Sigabaduru), through whiteorange (e.g. Skull Creek) to red (western Papua New Guinea) — this last colour form was first observed in captive fish in Australia in the 1990s and likely originated from Bensbach or Morehead where fish are known to have been collected and imported. The form with red fin margins could lead to confusion with M. maccullochi s.s. but the thick marginal band creating fin colour zones, black body stripes and silver grey base body colour allow ready identification (genetic examination with mtDNA genetic markers also indicated no major divergence of this colour form with other conspecific populations of M. sahulesnsis sp. nov.).

Etymology: The new species is named sahulensis with reference to the Pleistocene-era continent Sahul which comprised the land masses of Australia and New Guinea connected under low sea-level and is reflected in the modern distribution of the species. It is also a tribute to the Australian and New Guinea Fishes Association (which maintains the journal Fishes of Sahul) that has done much to promote and document native fishes of the region, especially rainbowfishes.

Figures

FIGURE 1. Location map of the Australia and New Guinea region showing Melanotaenia maccullochi s.l. genetic study collection sites (see Table 1) and locations of other museum material examined.

FIGURE 5. Comparative images of freshly prepared specimens of M. maccullochi s.l. species complex rainbowfishes: (top) Melanotaenia maccullochi s.s. (A) 30.0 mm male, Boggy Creek, Trinity Inlet, Cairns, Queensland (NTM S.18178-001) and (B) 41.8 mm female, Boggy Creek (NTM S.18178-001); (middle) Melanotaenia sahulensis sp. nov. (C) 38.2 mm male, Skull Creek, Cape York, Queensland, captive stock (NTM S.18153-001) and (D) 38.3 mm female, Skull Creek captive stock (NTM S.18153-001); and (lower) Melanotaenia wilsoni sp. nov. (E) 26.1 mm male holotype, Sandy Creek, Reynolds River system, Litchfield National Park, Northern Territory (NTM S.17776-001) and (F) 27.6 mm female paratype, Sandy Creek (NTM S.17776-002). Photos MPH.

FIGURE 6. Aquarium and specimen images of Melanotaenia maccullochi s.s. northeast Queensland (A) sparring males, Harvey Creek (wild caught), (B) male courting female, Etty Bay (wild caught), (C) ‘yawning’ male Cape Flattery (wild caught), (D) 42.7 mm SL male, Ninds Creek east, trib. Johnstone River, Etty Bay (QM I.32971), (E) 33.9 mm SL male, Cape Flattery (QM I.27221), and (F) 40.6 mm SL male holotype, Barron River, Cairns (QM I.731). Aquarium photos G. Schmida, specimen photos MPH.

FIGURE 7. Aquarium and specimen images of Melanotaenia sahulensis sp. nov. Queensland and New Guinea (A) displaying males, Skull Creek, Cape York (captive bred), (B) male courting female, Moa Island, Torres Strait (captive bred), (C) sparring males, red fin-edge colour form, Papua New Guinea aquarium stock in Australia early 1990s—sourced from Bensbach or Morehead, (D) 29.9 mm SL male, Scrubby Creek, Silver Plains, southern Cape York (QM I.39247), (E) 27.2 mm male, Bensbach River, Papua New Guinea (WAM P.31342-008), and (F) 45.0 mm SL male holotype, Pahoturi River, Sigabadu, Papua New Guinea (WAM P.26757-001). Aquarium photos G. Schmida, specimen photos MPH.

Tables

TABLE 4. Summary of meristic characters for Melanotaenia maccullochi s.l. study material. Invariant counts included pelvic rays (Pel; I,5*, n = 118) and branched caudal rays (Cr; 15*, n = 115). Character codes (e.g. D1, PreD) match ordination labels in Figure 2. Holotype counts, where known, indicated by *.

First dorsal fin spines (D1)
Species	4			5		6		7		Avg. Med.	n
M. maccullochi M. sahulensis sp. nov. M. wilsoni sp. nov.	1 2			29* 25 12*		21 25* 6		1		5.4 5 5.5 6 5.2 5	51 51 20
Second dorsal fin rays (D2)
Species	7		8		9		10		11	Avg. Med.	n
M. maccullochi M. sahulensis sp. nov. M. wilsoni sp. nov.	1 1 3*		10 26* 9		25* 17 8		14 7		1	9.1 9 8.6 8 8.3 8	51 51 20
Total anal fin rays (A)
Species	13		14		15		16		17	Avg. Med.	n
M. maccullochi M. sahulensis sp. nov. M. wilsoni sp. nov.	1 1		13 10*		23* 16 7		12 33* 2		2 2	15.0 15 15.7 16 14.5 14	51 51 20
Pectoral rays (Pec)
Species	11			12		13		14		Avg. Med.	n
M. maccullochi M. sahulensis sp. nov. M. wilsoni sp. nov.	1 1 9*			25 34 10		19* 15* 1		1 1		12.4 12 12.3 12 11.6 12	46 51 20
Total procurrent caudal rays (ProC)
Species	11	12		13		14		15		16 Avg. Med.	n
M. maccullochi M. sahulensis sp. nov. M. wilsoni sp. nov.	4	20 16 24*		22 12 1		19 15*		2 8		13.0 13 2 13.4 13 11.9 12	63 53 29
Lateral scales (Lat)
Species	29	30		31		32		33		34 Avg. Med.	n
M. maccullochi M. sahulensis sp. nov. M. wilsoni sp. nov.	1	3 8*		13 4 9		21* 14* 3		9 28		31.8 32 3 32.5 33 30.8 31	46 50 20
Transverse scales (Trans)
Species		9			10		11			Avg. Med.	n
M. maccullochi M. sahulensis sp. nov. M. wilsoni sp. nov.		24* 14* 2			24 35 18*		1			9.5 10 9.7 10 9.9 10	48 50 20
Predorsal scales (PreD)
Species	13	14		15		16		17		18 Avg. Med.	n
M. maccullochi M. sahulensis sp. nov. M. wilsoni sp. nov.	3 1	7 4* 5		24 23 8		10 19 7*		4		1 15.0 15 15.4 15 15.1 15	45 51 20