Pseudocaranx dinjerra, Smith-Vaniz & Jelks, 2006

Smith-Vaniz, William F. & Jelks, Howard L., 2006, Australian trevallies of the genus Pseudocaranx (Teleostei: Carangidae), with description of a new species from Western Australia, Memoirs of Museum Victoria 63 (1), pp. 97-106 : 98-100

Pseudocaranx dinjerra sp. nov.

Figures 2 , 3A , 4 , 5 ; Tables 1–3

Pseudocaranx dentex (non Bloch and Schneider) in: Allen and Swainston, 1988: 74, fig. 447 (misident., in part, brief descr.) in: Hutchins, 1990: 270 (listed; Shark Bay); Hutchins, 1997: 247 (listed; Houtman Abrolhos).

Material examined. Holotype. NMV A.1962 (245), SW of Shark Bay , 25˚28'S, 112˚27'E, 25˚19'S, 112˚17'E; trawled in 131–139 m; M.F. Gomon; sta. MFG-71; 4 Mar 1981.

Paratypes. 38 specimens, 77–230 mm FL. ANSP 148695 (2, 221– 230), off Cape Farquhar, 23˚42'S, 113˚01'E, 23˚48'S, 112˚58'E; trawled in 156–160 m; M/ V TM 71 ; 13 Sep 1979 . WAM P.22338 (217), Cape Cuvier, 24˚13'S, 113˚23'E; J. Penn; 29 Jul 1972 . ANSP 148696 (20, 77–92) and USNM 385866 (15, 81–95.5), Houtman Abrolhos, Hummock I., 28˚48'S, 114˚02'E, trawled in 43 m; Nov 1980 .

Diagnosis. A species of Pseudocaranx with posterior margin of upper jaw nearly vertical; lachrymal naked and expanded part of maxilla only partially covered with scales; caudal vertebra 14; gill rakers 7–10 upper, 19–21 lower, 27–31 total; scales in curved part of lateral line 53–66.

Description (values for holotype in parentheses). Dorsal fin rays VIII-I, (25) 23–25; anal-fin rays II-I, (21) 19–21; pectoral-fin rays (19) 18–20; vertebra 10 precaudal + 14 caudal; inferior vertebral foramina on caudal vertebra 7 or 8–10; scales in curved lateral line (61) 53–66; scales in straight LL (2) 2–11; scutes in straight LL (30) 19–31; total scales in LL (63) 58–74; total scales + scutes in LL (93) 86–99; developed gill rakers (8) 7–10 upper, (20) 19–21 lower, (28) 27–31 total, a single rudimentary raker rarely present on either end of gill arch.

Chest completely scaly; bases of dorsal and anal fins with a wide scaly sheath anteriorly; lachrymal naked; dorsal 3rd to half of expanded part of maxilla with a few embedded scales; cheeks, preopercle, opercle and interopercle covered with scales. Junction of curved and straight parts of lateral line below segmented dorsal-fin rays (13) 12–13; length of curved LL (0.57) 0.62–0.65 in straight LL; 1st dorsal-fin spines weak, the 3rd spine longest and slightly longer than height of 2nd dorsal-fin lobe; last dorsal- and anal-fin rays slightly longer and more widely spaced than adjacent rays; 1st anal-fin pterygiophore with anteroventral end short and bluntly rounded; 2nd dorsal-fin lobe (3.1) 2.8–3.1 in head length; pectoral fin of holotype and larger paratypes (0.94) 0.91–0.94 in head length. Upper jaw (2.7) 2.8–2.9 in head length, ending slightly in front of anterior margin of eye (fig. 3A); adipose eyelid weakly developed; lips slightly thickened and finely papillose. Jaw teeth (difficult to see clearly without dissection) in the holotype and 2 largest paratypes: upper jaw with a single row (21 left, 22 right) 19–22 of small conical teeth and (0) 1 inner tooth near symphysis; lower jaw with an outer row (21 left, 22 right) 25–27 of small conical teeth and an irregular inner row (11 left, 8 right) 13–18 of conical teeth on posterior half of jaw. (Based on observed changes in dentition with growth in other Pseudocaranx species, it is likely that an inner row of dentary teeth is absent in individuals of P. dinjerra larger than the holotype.) Vomerine tooth patch triangularshaped, without a median posterior extension, and sparsely covered with small teeth.

Measurements of the holotype (in parentheses) and 2 paratypes, 221–230 mm, as percentages of FL: snout to D1O (39) 41–42; snout to D2O (54) 56; snout to P2O (35) 34–35; snout to A2O (57) 57; D1O to P2O (30) 30; D1O to A2O (39) 39–41; D2O to A1O (32) 33–35; D20 to A2O (32) 33–35; D2 base (35) 35–37; A2 base (31) 30–31; height dorsal-fin lobe (10) 10–11; height anal-fin lobe (10) 9–10; pelvic-fin length (15) 14–15; pectoral-fin length (33) 34; head length (31) 31–32; postorbital head length (12) 12–13; snout length (12) 12; upper jaw length (11) 11; eye diameter (7) 7–8; curved lateral-line length (24) 24–25; and straight lateral-line length (24) 24–25.

Preserved coloration. Holotype and larger paratypes uniformly pigmented, except spinous dorsal fin slightly dusky and opercle with a prominent dark pupil-sized spot at level of pupil. Juveniles with 7–9 dusky bands on body, extending ventrally from dorsum and fading out on ventral half of sides. Bands widest dorsally and equal or slightly wider than pale interspaces at mid-level of side. Dark opercular spot, intense, smaller than pupil and slightly vertically elongate. Inter-radial membranes of 1st dorsal fin dusky, densely peppered with small melanophores.

Life coloration (from an underwater photograph, probably of a subadult, from Shark Bay provided by J.B. Hutchins). Silvery blue-green dorsally, fading to silvery with iridescence below, faint mid-lateral yellow stripe from opercle to base of caudal fin; faint yellow stripe on base of dorsal fin extending slightly onto dorsum; prominent black spot on opercle at level of the pupil, approximately diameter of pupil and vertically elongate.

Distribution. Endemic to WA (fig. 4). Definitely known from Houtman Abrolhos (28˚48'S) to off Cape Farquhar (23˚42'S), and reported (Allen and Swainston, 1988) to North-West Cape (~21˚47'S), but rare north of Shark Bay. Several photographs of Pseudocaranx taken by J.B. Hutchins off Green Head, WA (30˚04'S) are tentatively identified as P. dinjerra based on the tiny size of the opercular spot. We know of no collections of P. dinjerra from well-sampled Rottnest I. ( Hutchins and Pearce, 1994), located at 32˚S, where both P. wrighti and georgianus occur; but its occurrence there might be expected.

Dispersal of temperate and subtropical species along the north-west coast of Australia is believed to be aided by countercurrents flowing inshore of the southward-flowing warm Leeuwin Current. Fluctuations of this current regimen – associated with glacial and interglacial periods may have contributed to reproductive isolation and eventual speciation of Western Australian endemic subtropical species (Hutchins, 1994; Hutchins, 2001a), presumably including the new Pseudocaranx .

Etymology. The trivial name dinjerra (west) is an Aboriginal word ( Anon, 1969), in reference to the Western Australian endemic status of the species, and should be treated as an appositional noun.

Remarks. This species is most similar to Pseudocaranx georgianus but differs in having 14 caudal vertebra, and little overlap in number of anal-fin rays ( Table 1) and total lateral-line scales ( Table 3). Sheared PCA (fig. 5) revealed good separation of the three analyzed taxa. Although 11 of the 15 specimens of P. georgianus used in the analysis were obtained from the Sydney Fish Market, according to Kailola et al., 1993 the main commercial fishery is located in New South Wales waters where this species appears to be resident and non-migratory. Pseudocaranx dinjerra has a relatively longer snout and upper jaw (PC2) and shorter straight lateral line (PC3) than P. georgianus and P. sp. “ dentex ”. However, fork length (PC1) accounted for 97.5% of the variation, while only 1.7% was associated with PC2 and PC3. Differences were subtle, yet consistent in the three groups.

Other than P. wrighti , the only other previously described Indo-Pacific Pseudocaranx with 14 caudal vertebra is P. cheilio Snyder, 1904 , described from Honolulu, Hawaii. As mentioned in the introduction, at many locations in the Indo-west Pacific (including Hawaii and Easter Island) Pseudocaranx spp. invariably have either 14 or 15 precaudal vertebrae. In contrast, Yamaoka et al., 1991 found two distinct genetic morphs (identified by electrophoretic analysis) of “ P. dentex ” in Tosa Bay, Japan, each with different vertebral counts. The two morphs had strongly bimodal dorsal ray counts and the juveniles of one morph also appeared to have more distinct narrow bands on the body, leading these authors to strongly suspect that two species were involved. Masuda et al., 1995 also found significant mtDNA differences between the same two sympatric Japanese Pseudocaranx morphs. They implied that differences in spawning and recruitment locations and associated water temperatures may have affected the number of vertebrae. Vertebral counts are intraspecifically very constant in all other carangid genera (including 130+ species), so the situation in Pseudocaranx is very interesting if these morphs are not different species. Neither of the Japanese studies considered gill raker numbers, but our limited data indicate that they also differ between these two morphs. Pseudocaranx cheilio from Hawaii and the Japanese morph with 14 caudal vertebrae have higher numbers of lower gill rakers, 27–30 versus 19–21 in P. dinjerra .

Figures

Figure 2. Pseudocaranx dinjerra, Shark Bay, WA; photograph by J. B. Hutchins.

Figure 3. Heads of Pseudocaranx species: A, P. dinjerra, ANSP 148695, 230 mm FL, Cape Farquhar, WA; B, P. georgianus, USNM 385513, 275 mm FL, Sydney Fish Market; C, P. “dentex”, CAS 16472, 404 mm FL, One Tree I.; D, P. wrighti, WAM P.14007-18, 124 mm FL, Rottnest I.

Figure 4. Australian distributions of Pseudocaranx species based on material examined.

Figure 5. Sheared principal component analysis of 22 measurements for 3 Pseudocaranx taxa. PC2 loadings were associated with snout and upper jaw lengths, while PC3 was associated with straight lateral line and anal-fin base lengths; see Material and methods section for discussion of measurements used.