Syncomistes dilliensis, Shelley & Delaval & Le, 2017

Shelley, James J., Delaval, Aurélien & Le, Matthew C., 2017, A revision of the grunter genus Syncomistes (Teleostei, Terapontidae, Syncomistes) with descriptions of seven new species from the Kimberley region, northwestern Australia, Zootaxa 4367 (1), pp. 1-103 : 42-47

Syncomistes dilliensis , new species

( Tables 15 , 16 , S 22 & S 23 ; Figures 14 & 15 )

Corresponds to the nominated taxa code ‘ Syncomistes sp. 3’ of Shelley (2016).

English vernacular name: Dillie Grunter.

Holotype (measured): WAM P.34547.001 (99.1 mm SL), Charnley River at Pearson Creek confluence, Charnley River , 16° 12' 39.63'' S, 125° 30' 17.53'' E, obtained with gill nets in an deep, clear pool over sandstone substrate near a deep rocky overhang by J. J. Shelley and M. C. Le Feuvre, August 4, 2014.

Paratypes (measured): 9 specimens, 24.6–132 mm SL. WAM P.34547.002 (1), 132 mm, NTM S.18113-001 (1), 105 mm SL, NMV A.31453-001 (1), 72.8 mm SL, NMV A.31453-002 (1), 94.8 mm SL, Charnley River at Pearson Creek confluence, Charnley River, 16° 12' 39.63'' S, 125° 30' 17.53'' E, caught alongside the holotype ; WAM P.34535.001 (2), 24.6–40.1 mm SL, Dillie Gorge , Isdell River, 16° 44' 4.09'' S, 125° 22' 59.45'' E, June 23, 2013, obtained with backpack electrofisher in a shallow, swift flowing riffle by J. J. Shelley, M. C. Le Feuvre and S. Bui ; NMV A.31454-001 (1), 112 mm SL, NMV A.31454-002 (1), 74.0 mm SL, NMV A.31454-003 (1), 84.8 mm SL, Calder Gorge , Calder River, 16° 12' 50.62'' S, 125° 11' 18.32'' E, August 4, 2014, obtained with gill nets in a deep, clear pool surrounded by large boulders, by J. J. Shelley and M. C. Le Feuvre.

Diagnosis: A smaller species of Syncomistes (recorded up to 132 mm, commonly 70–100 mm SL). Syncomistes dilliensis sp. nov. differs from all other species within the Syncomistes complex by a combination of the following characters: lower jaw distinctly pointed when viewed from below, making a ‘V-shape’ in individuals> 65 mm ( Fig. 5d ); mouth subterminal; teeth flattened, narrow and short, ‘peg-shaped’ with anterior and posterior edges running straight and parallel from tooth base, tapering slightly at apical region to a rounded point ( Fig. 6h ); jaw of adults (> 65 mm) as wide as it is long or slightly longer when viewed from below; dorsal profile straight from dorsal origin to shallow notch on upper jaw; body lacking stripes; ventral profile only slightly convex; head slightly rounded from juveniles through to adults; jaw relatively short usually <30.0 in HL; mostly black in colour (sometimes bluish); 9–11 anal fin rays (usually 10); 17–19 gill rakers on lower arch (usually 18); postorbital length relatively short, usually <40.0 % HL; found in the Isdell, Charnley and Calder rivers of the western Kimberley region. No horizontal stripes present on body.

Description: See Table 15 for a summary of meristic variation by type material and other material examined and Table S22 meristic variation across all specimens combined. Dorsal fin spines XI (XI–XII), rays 12 (11–12); anal fin spines III, rays 9 (8–9); caudal fin rays 11+8+7+12 (9–12+8–9+7+9–12, n = 6); pectoral fin rays 15 (14– 15); pelvic spines I, rays 5; vertebrae 11+14 = 25 (n = 6); lateral line scales 52 (48–53); scales above lateral line 13 (10–14); scales below lateral line 22 (18–23); pre-dorsal scales 17 (15–21); cheek scale rows 4 (3–4); caudal peduncle scales 34 (33–37); gill rakers on first arch 10+18 = 28 (8–10+17–20 = 26–29); opercular spines 2; preopercular spines 11 (7–13).

See Table 16 for a summary of morphometric variation by type material and other material examined and Table S23 morphometric variation across all specimens combined. Body slightly compressed, with dorsal profile slightly more steeply angled than ventral profile, which is similarly convex. Dorsal profile begins with concave notch behind upper lip, steep rise, convex to dorsal fin origin, convex to just beyond base of last dorsal ray, then horizontal to caudal fin base. Ventral profile on underside of head straight and horizontal, slightly convex from back of head to last soft anal ray, then horizontal to caudal fin base. Lateral line continuous from behind head to base of caudal fin, and approximately parallel to dorsal profile. Body depth at dorsal fin origin 29.1 (26.2–33.4) % SL; body depth at anal fin origin 25.8 (23.0–30.2) % SL; caudal peduncle length 18.7 (17.1–20.8) % SL; caudal peduncle depth 11.2 (10.3–11.9) % SL; pre-anus length 64 (53.6–66.8) % SL. Head length 28.5 (26.7–30.2) % SL; head pointed; snout length 41.2 (34.3–45.6) % HL; upper-jaw length 28.3 (25.6–32.7) % HL; jaws equal throughout development; jaw width 28.2 (23.5–32.6) % SL. Teeth laterally compressed, narrow and short relative to Syncomistes , ‘peg-shaped’ with anterior and posterior edges running straight and parallel from tooth base, tapering slightly at apical region to a rounded point (Tooth Morphotype 4; Fig. 6h ); teeth fitted closely together but not overlapping, laterally pointed in lower jaw, extending beyond outer edge of lip. Outer row of large teeth with 1– 4 inner rows of smaller teeth embedded in jelly-like gum, reducing in size towards back rows; teeth on outer row of upper jaw 64 (28–79) number varying with size, 7.8 (6.8–11.6) / mm when standardised with upper jaw length; teeth on outer row of lower jaw 58 (22–71) number varying with size, 7.8 (6.8–11.6) / mm when standardised with upper jaw length; 4 (1–4) tooth rows behind outer row in upper jaw, 3 (2–4) in lower jaw; toothless medial hump present on dorsal surface at symphysis of lower jaw, opposite toothless region of upper jaw; lower jaw pointed V– shape in adults, rounded in juveniles (<65 mm SL) when viewed from below, wider than it is long (Morphotype 4; Fig. 5d ); lower jaw flattened when viewed laterally. Orbital diameter 24.8 (19.9–34.0) % HL; inter-orbital width 29.8 (25.5–33.6) % HL; inter-orbital smooth and not scaled; post-orbital length 39.7 (38.6–43.2) % HL. Lower opercular spine is longer and more robust than upper opercular spine, sometimes extends beyond edge of opercular membrane; Preopercular spines serrate, reducing in size dorsally and anteriorly, anteriormost spine just behind mid-point of orbit. Intestinal pattern of adults highly convoluted; large amount of looping to left of stomach; juveniles with less convoluted pattern.

Dorsal fin origin posterior to vertical plane through pectoral fin origin, anterior to pelvic fin origin; terminates at base of last dorsal ray; dorsal fin sheath scales 2; 6th (5th–6th) dorsal spine longest, length 11.7 (10.3–13.5) % SL; progressively shorter towards first and last spine; last dorsal spine fully joined to first dorsal ray by membrane; 3rd (2nd–3rd) dorsal ray longest, length 13.5 (12.3–15.4) % SL; dorsal margin of rayed portion is rounded until tip of last ray; dorsal fin base length 50.4 (48.5–53.2) % SL; dorsal fin length 55.5 (51.8–58.3) % SL; pre-dorsal fin length 39.6 (36.3–42.1) % SL. Anal fin origin immediately posterior to base of last dorsal fin spine; terminates at base of last ray; anal fin sheath scales 3 (1–4) anterior to posterior; 2nd anal spine longest, length 12.9 (11.2–15.1) % SL; 1st (1st–2nd) anal ray longest, length 15.2 (13.7–16.5) % SL; rays progressively shorter to last ray; margin of rayed portion is rounded; anal fin base length 15.6 (14.3–17.8) % SL; anal fin length 22.5 (21.2–25.9) % SL; pre-anal fin length 69.3 (60.4–72.0) % SL. Caudal fin slightly emarginate; upper caudal lobe length 24.7 (22.4–25.9, n = 8) % SL; middle caudal ray 18 (17.0–19.1) % SL. Pectoral fin length 18.4 (17.6–19.4) % SL; pre-pectoral fin length 28.3 (26.3–31.4) % SL. Pelvic spine length 9.2 (7.75–10.6) % SL; 1st (1st–2nd) pelvic ray longest, length 17.6 (15.0–19.8) % SL, then progressively shorter; pelvic fin length 19.1 (18.0–20.5) % SL; pre-pelvic fin length 35.9 (34.2–37.6) % SL.

Colour when fresh: Body of juveniles (<65 mm) olive green to blue in overall appearance. Darker dorsally, becoming lighter towards the ventral surface. Scales above the lateral line dark with gold posterior margins, below lateral line light with dark posterior margins. Lateral line scales black. Olive green iridescent tinge along lateral line and on operculum. Olive green to blue tinged stripe running below eye to snout, and a dark spot is present on upper edge of gill cover. Head and body below the lateral line with black speckling. Single black stripe sometimes running straight from the upper opercular spine to the middle of the caudle peduncle. Membranes of spinous dorsal dusky for the basal three-quarters, black at the tips. The membranes of soft are dusky, interrupted by a black stripe that running the length of the fin, close to the base, white at fin margin. Membranes of spinous and soft anal light white with a large dark blotch on middle of rays. Pelvics white with black pigmentation along the membrane between the middle 8 rays. Pectorals clear. Caudal dusky, lighter at fin edge.

Body of adults black in overall appearance, lighter on ventral surface. Scales iridescent olive green to gold, sometimes light black with thick black margins. Iridescent olive green tinge on operculum. Horizontal olive green tinged stripe running below eye to snout. Membranes of spinous dorsal uniformly black. The membranes of soft are black with a slight white margin along fin edge. Membranes of spinous and soft anal black with slight white margin along fin edge. Pelvics black with slight white margin along fin edge. Pectorals clear. Caudal black, slight white margin along fin edge. No stripes are present on the sides of adults.

Colour when preserved: Juveniles and adults uniformly dark brown with hints of pale brownish-orange colouration becoming more dominant towards the ventral region. Mostly pale brownish-orange when viewed ventrally. Lateral line is distinctly pale in colouration. Dorsal and caudal fins uniformly dark brown. Pectoral, pelvic and anal fins light brown with yellowish tinge. Black blotch sometimes present on anal fin. No preserved specimens retained horizontal striping.

Distribution: See Fig. 15 . Found in the Isdell, Charnley, and Calder Rivers. Their range within these rivers cannot currently be determined given the limited sampling in the area.

Ecology: Adults prefers fast flowing sections of creeks and rivers, although often found in deep, slow flowing pools. Juveniles prefer riffle habitat. Found in clear waters over rocky substrates, often where algae is abundant. Juveniles found predominantly in riffle habitat. Nothing is known about its reproductive biology. Diet primarily consists of filamentous algae that is scraped off rocks with its specially modified teeth.

Comparison: Broadly similar morphological grouping to Syncomistes versicolor , Syncomistes dilliensis , and S. rastellus based on the presence of a more pronounced, longer notch behind the upper lip, a more pronounced concave dorsal profile between the notch and the dorsal fin, and a squat V-shaped jaw that is wider than it is long. Unique in appearance although, most closely resembles S. rastellus . Syncomistes dilliensis can be distinguished from by having, on average, less dorsal spines 11 (11–12) and greater counts of the following characters: lateral line scales 52 (48–53), scale rows between the lateral line and dorsal 13 (10–14) and pectoral origin 22 (18–23), dorsal sheath scale rows 2, caudal peduncle scales 34 (33–37), and teeth on the lower jaw (relative to jaw length). Differences in morphology include shorter jaw width 28.3 (26.3–32.6) % HL and smaller fin measurements including: dorsal base length 50.4 (48.5–53.2) % SL, dorsal fin length 55.5 (51.8–58.3) % SL, dorsal spine length 11.7 (10.3–13.5) % SL, anal spine length 12.9 (11.2–15.1) % SL, pectoral fin length 19.6 (17.8–21.2) % SL, and pelvic spine length 9.2 (7.8–10.6) % SL. Body colour is variable, although overall colour ranges from olive green / blue in juveniles to black in adults, rather than silver in juveniles and adults ( Syncomistes holsworthi ), gold in juveniles to black in adults ( Syncomistes dilliensis ), or olive green to light brown in juveniles and adults ( S. rastellus ).

Etymology: The specific name dilliensis refers to the type locality, Dillie Gorge, on the Charnley River, Western Australia.

Remarks: Range does not overlap with a congeneric.

Figures

FIGURE 5.

FIGURE 6.

FIGURE 14.

FIGURE 15.

Tables

TABLE 15. Summary of meristic variation in Syncomistes dilliensis sp. nov. (values for number of teeth of upper and lower jaw are per mm of jaw length).

	Holotype	Paratypes (N = 9)
Character		Mode	Mean	Min.	Max.	S.D.
DS	11	11	11.4	11	12	0.52
DR	12	12	11.7	11	12	0.48
AS	3	3	3.0	3	3	0.00
AR	9	9	8.8	8	9	0.42
PecR	15	15	14.6	14	15	0.52
PelS	1	1	1.0	1	1	0.00
PelR	5	5	5.0	5	5	0.00
UUCR	11	11	10.8	9	12	1.10
UBCR	8	8	8.2	8	9	0.41
LBCR	7	7	7.0	7	7	0.00
LUCR	10	10	10.0	9	12	1.26
LLSc	52	52	50.8	48	53	1.69
LD	14	13	12.6	10	14	1.17
LA	21	22	21.0	18	23	1.70
PDSc	17	17	17.6	15	21	1.78
DSSc	2	2	2.0	2	2	0.00
ASSc	3	3	3.0	1	4	0.82
CScR	4	4	3.9	3	4	0.32
CPSc	34	34	34.7	33	37	1.25
GRup	10	10	9.4	8	10	0.84
GRlow	17	18	18.4	17	20	1.07
GRtot	27	28	27.8	26	29	0.92
PcV	11	11	11.0	11	11	0.00
CV	14	14	14.0	14	14	0.00
TV	25	25	25.0	25	25	0.00
LDR	2	2	2.4	2	3	0.52
LDS	6	6	5.6	5	6	0.52
LAR	1	1	1.2	1	2	0.42
LAS	2	2	2.0	2	2	0.00
LPR	1	1	1.2	1	2	0.42
Tup	7.9	9	9.4	7.6	14.8	2.14
Tlow	7.3	8	8.3	6.8	11.6	1.56
TRup	4	4	3.4	1	4	0.97
TRlow	4	3	3.0	2	4	0.47
OS	2	2	2.0	2	2	0.00
PS	11	11	10.2	7	13	2.10

TABLE 16. Morphometric variation in Syncomistes dilliensis sp. nov. (values are percentages of denominators in ratios, except for SL).

	Holotype	Paratypes (N = 9)
Character		Mean			Min.	Max.	S.D.
SL (mm)	104.9	83.9			24.6	131.9
BDd / SL	31.0	29.1			26.2	33.4	2.18
BDa / SL	26.6	25.8			23.0	30.2	1.97
CPL / SL	19.5	18.6			17.1	20.8	1.21
CPD / SL	11.2	11.2			10.3	11.9	0.51
HL / SL	28.4	28.5			26.7	30.2	1.03
OD / HL	21.1	24.8			19.9	34.0	4.41
IoW / HL	30.5	29.7			25.4	33.6	2.32
PoL / HL	39.4	39.7			38.6	43.2	1.31
SnL / HL	42.4	41.2			34.3	45.6	3.28
JLup / HL	32.7	28.3			25.6	32.7	2.06
JW / HL	30.3	28.2			23.5	32.6	2.46
PDFL / SL	40.3	39.6			36.3	42.1	1.75
PPecL / SL	28.0	28.3			26.3	31.4	1.54
PPelL / SL	36.5	35.9			34.2	37.6	1.04
PAL / SL	65.5	64.0			53.6	66.8	3.93
PAfL / SL	70.0	69.3			60.4	72.0	3.45
DFBL / SL	49.2	50.4			48.5	53.2	1.63
DFL / SL	54.4	55.5			51.8	58.3	2.18
DFRL / SL	13.1	13.5			12.2	15.4	0.97
DFSL / SL	10.6	11.7			10.3	13.5	1.02
AFBL / SL	15.1	15.6			14.3	17.8	1.24
AFL / SL	21.4	22.5			21.2	25.9	1.68
AFSL / SL	12.6	12.9			11.2	15.1	1.48
AFRL / SL	15.2	15.2			13.7	16.5	0.83
PecL / SL	18.9	18.4			17.6	19.4	0.58
PelL / SL	18.8	19.1			18.0	20.5	0.85
PelSL / SL	7.9	9.2			7.7	10.6	0.98
PelRL / SL	16.5	17.6			15.0	19.8	1.35
CLLup / SL	25.6	24.7			22.4	25.9	1.21
CLLmid / SL	18.8	18.0			17.0	19.0	0.67