Encrasicholina sigma, Hata & Motomura, 2020

Hata, Harutaka & Motomura, Hiroyuki, 2020, A new species of anchovy, Encrasicholina sigma (Teleostei, Clupeiformes, Engraulidae), from Sulawesi, Indonesia, Zootaxa 4750 (2), pp. 261-268 : 261-267

Encrasicholina sigma n. sp.

[New English name: Makassar Anchovy]

( Fig. 1 ; Tables 1–2)

Holotype. BMNH 1981.7 .29.296, 75.5 mm SL, Makassar , Sulawesi, Indonesia (purchased at Rajawali Fish Market), 9 June 1978, coll. by P. J. P. Whitehead.

Paratypes. BMNH 1981.7.29.297–312, 16 specimens, 62.9–75.5 mm SL , KAUM–I. 130150, 77.5 mm SL , KAUM–I. 130151, 67.7 mm SL , NSMT-P 134433 , 66.9 mm SL, collected with the holotype .

Diagnosis. A species of Encrasicholina with the following combination of characters: dorsal and anal fins with two unbranched rays; pseudobranchial filaments 17–24 (modally 19); branched pectoral-fin rays 12–14 (13); gill rakers 16–19 (18) in upper series on 1st gill arch, 21–23 (22) in lower series, 37–42 (41) in total; gill rakers 12–14 (13) in upper series on 2nd gill arch, 19–21 (19) in lower series, 31–35 (32) in total; gill rakers 9–11 (11) in upper series on 3rd gill arch, 9–12 (11) in lower series, 18–23 (21) in total; gill rakers 7–10 (9) in upper series on 4th gill arch, 8–10 (9) in lower series, 16–20 (19) in total; gill rakers 4–7 (6) on hind face of third gill arch; spine-like scutes on abdomen 4–6 (5); transverse scales 8 or 9 (9); exposed urohyal bony, without fleshy nobs; head and jaws relatively long, head length 25.2–27.0% (mean 26.1%) of SL, upper jaw length 18.4–20.0% (19.2%) of SL, lower jaw length 16.4–18.1% (17.3%) of SL; anal-fin base relatively short, 12.9–14.8% (13.9%) of SL; first unbranched dorsal- and anal-fin rays relatively long, length 4.4–6.5% (5.5%) of SL and 2.7–3.8% (3.4%) of SL, respectively; distance between dorsal-fin origin and upper end of pectoral-fin insertion 105.1–121.8% (115.4%) of HL.

Description. Counts and measurements, expressed as percentages of SL and HL, are given in Tables 1 and 2. Data for the holotype are presented first, followed by paratype data in parentheses (if different). Body subcylindrical, somewhat compressed laterally, elongate, deepest at dorsal-fin origin. Dorsal profile of head and body gently elevated from snout tip to dorsal-fin origin, thereafter lowering to caudal-fin base. Ventral profile of head and body slightly convex from lower-jaw tip to pelvic-fin insertion, thereafter gently rising to caudal-fin base. Abdomen rounded, covered by five (four to six) sharp, needle-like scutes anterior to insertion of pelvic fins. Postpelvic and predorsal scutes absent. Anus situated just anterior to anal-fin origin. Caudal peduncle compressed. Head compressed. Snout tip rounded; snout length less than eye diameter. Interorbital area flat, width less than eye diameter. Mouth large, inferior, ventral to body axis, extending backward beyond posterior margin of eye. Lower jaw slender, shorter than upper jaw. Posterior end of maxilla pointed, projecting beyond second supra-maxilla and posterior margin of preopercle. Single row of conical teeth on each jaw and on palatines. Small conical teeth in patches on vomer and ectopterygoid. Eye large, round, covered with adipose eyelid, positioned laterally on head dorsal to horizontal through pectoral-fin insertion, visible in dorsal view. Pupil round. Orbit elliptical. Nostrils close to each other, positioned anterior to orbit. Posterior margins of preopercle and opercle smooth. Subopercle with rounded posterior margin. Opercular membrane without serrations. Pseudobranchial filaments present, length of longest filament less than eye diameter. Open posterior fontanelles on top of head near occiput. Gill rakers long, slender, rough, visible from side of head when mouth opened. Isthmus muscle short, not reaching anteriorly to posterior border of gill membrane, preceded by exposed urohyal between gill membranes. Gill membrane not broadly joined over isthmus. Scales cycloid, thin, deciduous (except for prepelvic scutes), absent on head. Lateral line absent. Scales absent on fins, except for broad triangular sheath of scales on caudal fin. Pectoral-fin axillary scale shorter than pectoral fin, larger than pelvic-fin axillary scale. Dorsal-fin origin posterior to vertical through base of last pelvic-fin ray, slightly posterior to midbody. Dorsal and anal fins with two anteriormost rays unbranched. Posterior tip of depressed dorsal fin reaching to vertical through anal-fin origin. Anal-fin origin posterior to posteriormost point of dorsal-fin base (just below 13th or 14th dorsal-fin ray base). Posterior tip of depressed anal fin short of caudal-fin base. Uppermost pectoral-fin ray unbranched, inserted below body midline. Posterior tip of pectoral fin not reaching vertical through pelvic-fin origin. Pelvic-fin shorter than pectoral fin, insertion anterior to vertical through dorsal-fin origin, depressed posterior tip not reaching (slightly exceeding) vertical through dorsal-fin origin.

Color of preserved specimens. Body uniformly pale ivory, a dark brown longitudinal band of width less than eye diameter, from just posterior to upper opercular margin to caudal-fin base. Scales on upper body to longitudinal band with posterior brown margin. Numerous black spots on snout, suborbital area and lower-jaw tip. Melanophores scattered on rays of dorsal and caudal fins. Live and fresh coloration unknown.

Distribution. Currently known only from Makassar, southwestern Sulawesi, Indonesia.

Etymology. The specific name sigma is derived from Greek meaning “sum total” in reference to the major diagnostic feature of the species, the sum total of gill raker numbers on the first gill arch.

Remarks. The new species is assignable to the genus Encrasicholina , defined by Whitehead et al. (1988) and Wongratana et al. (1999), having a short isthmus muscle not reaching anteriorly to the posterior margin of the gill membrane, exposed urohyal, and prepelvic scutes, and the absence of postpelvic scutes. To date, eleven nominal species (nine valid) have been attributed to Encrasicholina ( Whitehead et al. 1988; Hata & Motomura 2015, 2016a, b, 2017). Encrasicholina sigma is similar to E. pseudoheteroloba ( Hardenberg 1933) , both species sharing two unbranched rays in the dorsal and anal fins, and a long upper jaw (reaching posterior margin of preopercle). However, the former has a lower number of gill rakers on each gill arch ( Table 1; Fig. 2 ), in addition to a longer head ( Fig. 3A ) and shorter anal-fin base (12.9–14.8 % SL vs. 13.8–18.7% in E. pseudoheteroloba ; Fig. 3B ).

Encrasicholina sigma is easily distinguished from Encrasicholina purpurea Fowler 1900 , Encrasicholina punctifer Fowler 1938 [senior synonym of Stolephorus buccaneeri Strasburg 1960 ( Wongratana 1983; Whitehead et al. 1988; Wongratana et al. 1999; Hata & Motomura 2016a)], Encrasicholina intermedia Hata & Motomura 2016 , and Encrasicholina gloria Hata & Motomura 2016 by the long upper jaw (see Diagnosis), the posterior end of the upper jaw not reaching the preopercular posterior margin of the other four species ( Wongratana 1983; Whitehead et al. 1988; Wongratana et al. 1999; Hata & Motomura 2016a), and an exposed bony urohyal, without fleshy nobs (vs. fleshy knob on each side of exposed urohyal; Wongratana 1983; Whitehead et al. 1988; Wongratana et al. 1999; Hata & Motomura 2016a). The new species clearly differs from Encrasicholina oligobranchus ( Wongratana 1983) in having higher gill raker counts on the 1st gill arch (16–19 + 21–23 in E. sigma vs. 13–14 + 17–18 in E. oligobranchus ) and a longer upper jaw (vs. upper jaw posterior end just reaching anterior margin of preopercle) ( Wongratana 1983; Whitehead et al. 1988; Wongratana et al. 1999). Although the long upper jaw of E. sigma is shared by Encrasicholina heteroloba ( Rüppell 1837) [senior synonym of Amentum devisi Whitley 1940 ( Hata & Motomura 2016b)], Encrasicholina macrocephala Hata & Motomura 2015 , and Encrasicholina auster Hata & Motomura 2017 , the former differs in having two unbranched rays in the dorsal and anal fins (vs. three unbranched rays in the latter three species), and long first rays in the dorsal and anal fins (4.4–6.5% and 2.7–3.8%, respectively vs. 0.4–1.8% and 0.3–1.8% in E. heteroloba , 0.6–1.3% and 0.5–1.0% in E. macrocephala , 0.9–1.5% and 0.9–1.3% in E. auster ) ( Hata & Motomura 2015, 2016b, 2017).

Comparative material examined. Encrasicholina pseudoheteroloba (186 specimens, 34.7–77.9 mm SL): listed in Hata & Motomura (2016b, c) and 24 additional specimens: BPBM 34277, 1 of 3, 68.3 mm SL, St. Vincent Bay, north side of Ile Puen, New Caledonia, 12 m depth; KAUM–I. 74153, 36.4 mm SL, Sumiyo Bay, Sumiyo, Amami-oshima island , Ryukyu Islands , Japan; KAUM–I. 80175, 55.4 mm SL, Marudu Bay , Sabah, Malaysia; USNM 327507 , 20 specimens, 36.9–61.8 mm SL, Caroline Islands; SAM 34758, 1 of 10 specimens, 60.6 mm SL, off Pebane , Mozambique (17°41′S, 38°43′E), 1.4 m depth .

Figures

FIGURE 1. Holotype of Encrasicholina sigma n. sp., BMNH 1981.7.29.296, 75.5 mm SL, Makassar, Sulawesi, Indonesia

FIGURE 2. Relationships of total gill raker counts (TGR) on (A) first gill arch (1GA), (B) second gill arch (2GA), (C) third gill arch (3GA), and (D) fourth gill arch (4GA) to standard length in Encrasicholina sigma n. sp. (closed circles) and E. pseudoheteroloba (open triangles).

FIGURE 3. Relationships of (A) head length (HL; as % of standard length; SL) and (B) anal-fin base length (as % of SL) in Encrasicholina sigma n. sp. (closed circles; HL / SL: Y = -0.0891X + 32.325, p value <0.001) and E. pseudoheteroloba (open triangles; HL / SL: Y = -0.0589X + 28.718, p value <0.000001). Solid and dotted lines indicate regression lines fo E. sigma and E. pseudoheteroloba, respectively. Non-significant regressions of anal-fin base length of the two species (p value> 0.05) are not given.