Syncomistes holsworthi, 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 : 47-52

Syncomistes holsworthi , new species

( Tables 17 , 18 , S 22 & S 23 ; Figures 16 & 17 )

Syncomistes rastellus (non S. rastellus Vari & Hutchins 1978 ): Buckle et al. 2010: 17. Corresponds to the nominated taxa code ‘ Syncomistes sp. 1’ of Shelley (2016).

English vernacular name: Holsworth’s Grunter.

Holotype (measured): WAM P.34530.001 (146 mm SL), Flying Fox Creek , Ord River, 16° 32' 54.258'' S, 128° 22' 13.31'' E, obtained with gill nets in a deep, isolated, turbid pool in the drying streambed of the creek by J. J. Shelley and M. C. Le Feuvre, January 1, 2013.

Paratypes (measured): 18 specimens, 24.5–215 mm SL. WAM P.34530.002 (2), 204–215 mm SL, Flying Fox Creek, Ord River , 16° 32' 54.258'' S, 128° 22' 13.31'' E, January 1, 2013, caught alongside the holotype ; WAM P.34537.001 (2), 85.8–166 mm SL, NTM S.18110-001 (1), 163 mm SL, Croc Hole, Wilson River, Bow River, 16° 38' 49.45'' S, 128° 6' 36.47'' E, July 10, 2013, obtained with gill nets in an large, deep, isolated, and slightly turbid pool (Croc Hole) on the Wilson River by J. J. Shelley and M. C. Le Feuvre ; WAM P.34529.001 (1), 74.3 mm SL, Ord River Gorge, 17° 25' 29.75'' S, 127° 35' 52.63'' E, January 20, 2013, obtained with backpack electrofisher in a fast rapid by J. J. Shelley and M. C. Le Feuvre ; WAM P.34538.001 (2), 41.9–60.8 mm, NMV A.31450-001, 24.5 mm, Bow River road crossing, Bow River , 16° 47' 36.74'' S, 128° 16' 47.59'' E, July 13, 2013, obtained with backpack electrofisher in a riffle by J. J. Shelley and M. C. Le Feuvre ; NTM S.14129-002 (8), 70.8–129 mm SL, Ikymbon River , Victoria River, 15° 16' 0.12'' S, 130° 49' 58.8'' E, September 10, 1981, obtained using a combination of methods by S. H. Midgley.

Diagnosis: A large species of Syncomistes (recorded up to 260 mm SL, commonly 150–200 mm). Syncomistes holsworthi 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. 6f ); 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 silver in colour (sometimes greenish); 7–9 anal fin rays (usually 8); 18–22 gill rakers on lower arch (usually 20); postorbital length relatively long, usually> 40.0 % HL; found in the Durack, Pentecost, Ord and Victoria rivers of the east Kimberley/ Northern Territory boarder region.

Description: See Table 17 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 XII, rays 13 (11–14); anal fin spines III, rays 8 (7–9); caudal fin rays 11+8+7+10 (9–11+8+7+8–12, n = 12); pectoral fin rays 16 (15–16); pelvic spines I, rays 5; vertebrae 11+14 = 25 (11+14–15 = 25–26, n = 12); lateral line scales 50 (48–53); scales above lateral line 12 (10–13); scales below lateral line 22 (19–24); pre-dorsal scales 18 (15–23); cheek scale rows 4 (3–5); caudal peduncle scales 31 (29–35); gill rakers on first arch 11+18 = 29 (6–12+18–22 = 28–34, n = 17); opercular spines 2; preopercular spines 16 (8–23).

See Table 18 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 more steeply angled than ventral profile, which is horizontal. Dorsal profile begins with concave ‘notch’ behind upper lip, steep rise, slightly convex to inter-orbital, convex along nape and to dorsal fin origin, convex until behind base of last dorsal ray, then horizontal to caudal fin base. Ventral profile on underside of head straight or slightly convex, straight or slightly convex from back of head to last soft anal ray, 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 32.1 (29.9–35.0) % SL; body depth at anal fin origin 29.4 (25.8–31.8) % SL; caudal peduncle length 18.1 (16.2–20.3) % SL; caudal peduncle depth 12 (10.8–13.5) % SL. Pre-anus length 65.9 (62.8–68.5) % SL. Head length 30.1 (27.5–33.4) % SL; head pointed; snout length 40 (30.9–43.3) % HL; upper-jaw length 28.5 (25.0–31.1) % HL; jaws equal throughout development; jaw width 32.8 (25.0–38.8) % HL. 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. 6f ); teeth fitted closely together but not overlapping, laterally pointed in lower jaw, extending beyond outer edge of lip. Outer row of large teeth with 2–4 inner rows of smaller teeth on both jaws, embedded in jelly-like gum. Teeth on outer row of upper jaw 92 (25–111) number varying with size, 4.0 (3.0–5.4) when standardised with upper jaw length; teeth on outer row of lower jaw 94 (26–121) number varying with size, 8.1 (5.9–11.3) when standardised with upper jaw length; a toothless medial hump present on dorsal surface at symphysis of lower jaw, opposite toothless region of upper jaw; lower jaw distinctly V-shaped in adults and rounded in juveniles (<65 mm) when viewed from below, wider than it is long (Morphotype 4; Fig. 5d ). Lower jaw flattened when viewed laterally. Orbital diameter 21.6 (15.9–29.6) % HL; inter-orbital width 30.3 (23.5–34.1) % HL; inter-orbital smooth and not scaled; post-orbital length 41.4 (39.3–44.9) % 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 at mid-point, same anterior to posterior; 5th (5th–7th) dorsal spine longest, length 12.6 (11.2–14.1) % SL; progressively shorter towards first and last spine; last dorsal spine fully joined to first dorsal ray by membrane; 5th (1st–7th) dorsal ray longest, length 13.8 (9.0–15.4) % SL; dorsal margin of rayed portion is rounded until tip of last ray; dorsal fin base length 54.9 (51.7–60.0) % SL; dorsal fin length 60.5 (56.5–65.8) % SL; pre-dorsal fin length 39.4 (36.2–41.7) % SL. Anal fin origin immediately posterior to base of last dorsal fin spine; terminates at base of last ray; anal fin sheath scales 5 (2–5), 2–4 rows anteriorly progressing to 5–6 rows posteriorly; 2nd anal spine longest, 13.8 (12.4–16.0) % SL; 2nd anal ray longest (1st–3rd, n = 16), 15.5 (13.3– 16.6, n = 16) % SL; rays progressively shorter to last ray; margin of rayed portion is rounded; anal fin base length 15.1 (13.3–17.0) % SL; anal fin length 22.9 (20.4–26.1) % SL; pre-anal fin length 69.6 (66.0–72.7) % SL. Caudal fin slightly emarginate; upper caudal lobe length 25.6 (16.7–29.0) % SL; middle caudal ray length 17.6 (12.7–20.8) % SL. Pectoral fin length 19.6 (17.8–21.2) % SL; pre-pectoral fin length 38.1 (26.4–32.7) % SL. Pelvic spine length 10.9 (8.7–12.3) % SL; 2nd (1st–2nd) pelvic ray longest, length 19.6 (18.0–21.7) % SL; subsequent rays becoming progressively shorter; pelvic fin length 21.1 (19.0–22.9) % SL; pre-pelvic fin length 38.1 (35.8–41.1) % SL.

Colour when fresh: Body dark bluish-brown overall during wet season, greyish to silver overall during dry season. Darker dorsally, becoming lighter along the ventral surface. Juveniles white on ventral surface. A blueishsilvery stripe running below eye to snout. Opercle and subopercle with a dark blotch extending ventrally from opercular spine. Posterior scale margins have a dark band. All fins dark, occasionally with a purple tinge. No stripes were observed on the sides of juveniles or adults.

Colour when preserved: Juveniles and adults uniformly dark brown with hints of faint hints of pale colouration becoming more dominant towards the ventral region. Mostly pale brown when viewed ventrally. Lateral line is distinctly pale in colouration. All fins dark brown. Dark blotch sometimes present on anal fin. Distribution: See Fig. 17 . Occurs throughout the Ord, Penticost, and Durack rivers in the eastern Kimberley region (WA), and the Victoria River in the Northern Territory.

Ecology: Adults prefer deeper, slow flowing sections of creeks and rivers, as well as still waters and billabongs. Juveniles found in shallow, still waters or occasionally in riffle habitat. Are often observed shoaling in the middle of the water column around snags, sometimes with S. bonapartensis . Found in clear and turbid waters, over rocky and muddy substrates, often where algae is abundant. Recorded in water temperatures up to 36°C. Individuals sexually mature at 90–100 mm and breed during the wet season. Appear to wait until a major flood event to spawn. Eggs are large (~ 3 mm) and non-adhesive. Diet primarily consists of filamentous algae that is scraped off rocks with specially modified teeth.

Comparison: Broadly similar morphological grouping to Syncomistes versicolor , S. 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 at all stages of development, and a squat V-shaped jaw in adults that is wider than it is long (lower U-shaped in juveniles <65 mm).

Although unique, S. holsworthi most closely resembles S. versicolor . Syncomistes holsworthi can be distinguished by having, on average, less anal fin rays 8 (7–9) versus 10 (9–11), more scale rows between the lateral line and pelvic fin base 22 (19–24) versus 20 (19–22), more gill rakers on the lower arch 20 (18–22) versus 18 (17–19) and in total 30 (28–34) versus 28 (27–29), longer postorbital length 41.4 (39.3–44.9) % HL versus 38 (37.8–39.5) % HL, shorter snout length 40.0 (30.9–43.3) % HL versus 45.3 (43.6–47.5) % HL, shorter upper jaw length 28.5 (25.0–38.8) % HL versus 32.5 (31.3–35.3) % HL, and shorter anal ray length 15.5 (13.3–16.6) % SL versus 17.2 (14.7–18.5) % SL. Body colour is variable, although juveniles and adults are generally silver in overall appearance rather than gold in juveniles to black in adults ( S. versicolor ), olive green / blue in juveniles to black in adults ( S. dilliensis ), or olive green to light brown in juveniles and adults ( S. rastellus ).

Etymology: The specific name holsworthi honors Bill Holsworth whose foundation financed the expedition on which this species was found, as well as providing ongoing support for doctoral research into the ecology, management and natural history of Australian wildlife.

Remarks: Lives in sympatry with S. bonapartensis and S. kimberleyensis . Has been misidentified in the Ord and Victoria rivers.. A large survey conducted by Buckle et al. (2010) in the Ord River catchment identified S. rastellus throughout the catchment and these specimens were lodged at NTM (not registered). We inspected these specimens under a dissecting microscope and confirmed that S. holsworthi had been mistakenly identified as S. rastellus . Furthermore, S. H. Midgley in his September 10, 1981 collections identified S. rastellus in the Victoria River. These specimens were included in our morphological analysis (NTM S.14129-002) and it was determined that they were misidentified S. holsworthi . Therefore, the known range of S. rastellus is in fact confined to the Drysdale River.

Figures

FIGURE 5.

FIGURE 6.

FIGURE 16.

FIGURE 17.

Tables

TABLE 17. Summary of meristic variation in Syncomistes holsworthi sp. nov. (values for number of teeth of upper and lower jaw are per mm of jaw length).

	Holotype	Paratypes (N = 17)
Character		Mode	Mean	Min.	Max.	S.D.
DS	12	12	12	12	12	0.00
DR	12	13	13	11	14	0.86
AS	3	3	3	3	3	0.00
AR	8	8	8	7	9	0.73
PecR	15	16	16	15	16	0.51
PelS	1	1	1	1	1	0.00
PelR	5	5	5	5	5	0.00
UUCR	10	11	10	9	11	0.89
UBCR	8	8	8	8	8	0.00
LBCR	7	7	7	7	7	0.00
LUCR	9	10	10	8	12	1.06
LLSc	53	50	51	48	53	1.47
LD	10	12	11	10	13	0.78
LA	22	22	22	19	24	1.23
PDSc	16	18	18	15	23	2.72
DSSc	2	2	2	2	2	0.00
ASSc	5	3	4	2	5	1.06
CScR	5	4	4	3	5	0.49
CPSc	35	31	31	29	35	1.87
GRup	11	11	11	6	12	1.41
GRlow	18	20	20	18	22	1.29
GRtot	29	30	30	28	34	1.46
PcV	11	11	11	11	11	0.00
CV	14	14	14	14	15	0.29
TV	25	25	25	25	26	0.29
LDR	5	4	4	1	7	1.46
LDS	5	6	6	5	7	0.57
LAR	2	2	2	1	3	0.70
LAS	2	2	2	2	2	0.00
LPR	2	1	1	1	2	0.49
Tup	7.1	8	8	6	11	1.46
Tlow	7.2	8	8	6	11	1.33
TRup	4	4	4	3	4	0.49
TRlow	4	3	3	2	4	0.55
OS	2	2	2	2	2	0.00
PS	21	16	16	8	23	4.52

TABLE 18. Morphometric variation in Syncomistes holsworthi sp. nov. (values are percentages of denominators in ratios, except for SL).

	Holotype	Paratypes (N = 17)
Character		Mean	Min.	Max.	S.D.
SL (mm)	146.3	111.6	24.5	215.1
BDd / SL	33.5	32.1	29.8	35.0	1.40
BDa / SL	29.4	28.4	25.8	31.8	1.74
CPL / SL	18.7	18.1	16.2	20.3	1.29
CPD / SL	12.2	12.0	10.8	13.5	0.72
HL / SL	29.7	30.1	27.5	33.4	1.75
OD / HL	15.9	21.6	15.9	29.6	3.44
IoW / HL	33.6	30.3	23.5	34.1	2.61
PoL / HL	44.9	41.4	39.3	44.9	1.85
SnL / HL	43.3	39.9	30.9	43.3	3.20
JLup / HL	30.0	28.5	25.0	31.1	1.46
JW / HL	35.0	32.8	25.0	38.8	3.58
PDFL / SL	40.1	39.3	36.2	41.7	1.22
PPecL / SL	28.0	29.1	26.4	32.7	1.93
PPelL / SL	37.5	38.1	35.8	41.1	1.56
PAL / SL	63.3	65.9	62.8	68.5	1.78
PAfL / SL	66.9	69.6	66.0	72.6	2.07
DFBL / SL	60.0	54.9	51.7	60.0	2.22
DFL / SL	63.6	60.5	56.5	65.8	2.54
DFRL / SL	14.1	13.8	9.0	15.4	1.58
DFSL / SL	13.3	12.6	11.2	14.1	0.90
AFBL / SL	16.1	15.1	13.3	16.9	1.02
AFL / SL	23.6	22.8	20.4	26.1	1.64
AFSL / SL	15.5	13.8	12.4	16.0	1.06
AFRL / SL	15.9	15.5	13.3	16.6	0.98
PecL / SL	20.5	19.6	17.7	21.2	1.01
PelL / SL	22.9	21.1	19.0	22.9	0.96
PelSL / SL	11.9	10.9	8.7	12.2	0.96
PelRL / SL	20.7	19.5	18.0	21.6	0.98
CLLup / SL	29.0	25.6	16.7	29.0	2.90
CLLmid / SL	19.1	17.6	12.7	20.8	1.73