Nuchequula nuchalis, , RMNH, 1287

CHAKRABARTY, PROSANTA & SPARKS, JOHN S., 2007, Phylogeny and Taxonomic Revision of Nuchequula Whitley 1932 (Teleostei: Leiognathidae), with the Description of a New Species, American Museum Novitates 3588 (1), pp. 1-28 : 18-21

Nuchequula nuchalis

( Temminck & Schlegel, 1845) figures 5B , 6C , 9 , tables 3–4

Equula nuchalis: Temminck and Schlegel, 1845: 126 , plate 67, fig. 1

Eubleekeria (Nuchequula) nuchalis: Whitley, 1932: 111

DIAGNOSIS: Nuchequula nuchalis is distinguished from congeners by the presence of two yellow-green horizontal lines extending from the operculum to the caudal fin. One stripe straddles the lateral line, and the other extends from near the dorsal margin of the operculum to the caudal peduncle.

DESCRIPTION: Comparative features are presented in table 3; morphometric and meristic data are presented in table 4. The original description by Temminck and Schlegel (1845) provides ample distinguishing features to permit clear identification of this species. Although only a single type specimen (which remains in excellent condition), collected off Japan, was deposited, it is clear from the description by Temminck and Schlegel (1845) that additional material was examined. Temminck and Schlegel (1845) described the species as having a blackish blotch on the nuchal area, with the spiny portion of the dorsal fin tinted black.

Our examination of individuals of Nuchequula nuchalis revealed that the mouth is terminal and directed ventrally when extend- ed. The teeth are villiform and arrayed in a narrow band of three or four poorly differentiated rows. The body depth ranges between 40% and 50% of SL. The length of the second dorsal-fin spine is around 35–40% of body depth, whereas the length of the second anal-fin spine is about 20–30% of body depth. The length of the first dorsal-fin spine is about 12–15% of the second spine. The length of the first anal-fin spine is about 25–30% of the second spine. The dorsal- and anal-fin spines are robust. In lateral view, a weak concavity is present dorsal to the orbit. The caudal fin is deeply forked. The depth of the caudal peduncle is about 5–7% of SL. The lateral line is complete from the opercle to the posterior margin of the caudal peduncle and is parallel with the shape of the back. The lips are somewhat fleshy. The dorsal- and pelvicfin origins are located along the same vertical. The anal-fin origin is located on the vertical from the eighth dorsal-fin spine. There are 16 rakers on the lower limb of the first gill arch. These rakers are about one-quarter to onehalf the length of the gill lamellae. Scales are absent on the chest, head, and nape but present elsewhere on the flanks. The profile of the lower jaw in lateral view is slightly concave. Two postnasal spines are present dorsal to the orbit and posterior to the nasal pores. The supraorbital ridge is serrated.

Pigmentation pattern in life: The body is silvery, approaching white in the area posteroventral to the pectoral-fin base (see fig. 5B ). There are two narrow, yellow-green stripes on the flank. One stripe straddles the lateral line, and another is near the midline, extending from near the dorsal margin of the opercle to the caudal peduncle. There is a mustardyellow to light-yellow tint to all of the fins, particularly distally. There is more yellow on the edge of the ventral lobe of the caudal fin than there is on the dorsal lobe. There is a distinct black marking on the dorsal-fin membrane between the second and fifth spines. The second through fifth spines are silvery. The nuchal marking is black and triangular or rounded. Light yellow zigzagging lines are present on the dorsal flanks in life, but they rarely extend below the lateral line ( Temminck and Schlegel, 1845).

Pigmentation in preservative: The body is silvery, with guanine covering most of the body. A slight golden-yellow tint remains in some areas, particularly where scales are intact. The area dorsal to the midline has a lower concentration of guanine than the region ventral to the midline, and the dorsal flank region is devoid of markings. A large, triangular (sometimes rounded) dark-brown marking is present in the nuchal region. The fins are tan, with some remnant silvery coloration retained on the second through fifth spines of the dorsal fin. The dorsal fin has a distinct black blotch on the membrane of the second through fifth spines. In specimens preserved with the guanine layer intact (including the holotype), the guanine layer appears quite deep and rich, and the specimens are highly reflective. Specimens without guanine are white to a yellowish off-white color throughout the body, and more yellowish on the head. There is a concentration of melanophores dorsal to the mouth and anterior to the orbit. There are scattered melanophores ventral to the midline, except for a mitten-shaped melanophore-free region posteroventral to the pectoral-fin base.

DISTRIBUTION: Coastal waters of Japan (Shikoku Island, Tokyo, and Nagasaki) and Taiwan.

Nuchequula pan ( Wongratana, 1988) figures 6D , 10 , tables 3–4

Leiognathus pan: Wongratana 1988 .

DIAGNOSIS: Nuchequula pan is distinguished from congeners by a series of four broken longitudinal lines on the dorsal flank (versus vertical zigzagging lines, vermiculations, or an absence of dorsal flank markings).

DESCRIPTION: Comparative features are presented in table 3; morphometric and meristic data are presented in table 4. Nuchequula pan has a terminal mouth that is directed ventrally when extended. The teeth are villiform and in a narrow band. The body is elongate. (Wongratana lists one paratype as having a body depth of 50% of SL, which is an error, given that the reported range he gives for types is 34.2–42.6% of SL, and our measurement of the same specimen, CUMZ 2528.2 .9.3, found its maximum body depth to be 41%.) The length of the second dorsal-fin spine of the holotype and three paratypes we examined ranges from 47% to 54% of the body depth, whereas the length of the second analfin spine is 36–50% of body depth. The length of the first dorsal-fin spine is 14–16% of the second spine. The length of the first anal-fin spine is 20–30% of the second. The dorsal- and anal-fin spines are robust. In lateral view, a slight concavity is present above the orbit. The dorsal and ventral profiles are about equally convex. The caudal fin is deeply forked. The depth of the caudal peduncle is about 6–7% of SL. The lateral line is complete from the opercle to the posterior margin of the caudal peduncle. The lips are thin and not fleshy. The dorsal- and pelvic-fin origins are located along the same vertical. The anal-fin origin is located on the vertical from the eighth dorsal-fin spine. There are 15–17 rakers on the lower limb of the first gill arch. Scales are present on the chest. The profile of the lower jaw is slightly concave in lateral view. Two robust postnasal spines are present dorsal to the orbit and posterior to the nasal pores. The supraorbital ridge is weakly serrated. (We disagree with Wongratana’s description of this ridge as ‘‘smooth.’’) The body width ranges from about 12% to 16% of SL .

Pigmentation pattern in life: Wongratana (1988) describes fresh material as ‘‘iridescent blue-green dorsally, silvery laterally, brilliant silvery white, washed with very pale orange ventrally from pectorals to above middle of anal-fin base … [U]pper half of body with four longitudinal rows of elongate, greenish blue spots, third row on lateral line, fourth below … prominent greenish-blue blotch across nape.’’ The pigmentation pattern and coloration in life may also be diagnostic but should be verified with more recently collected material, as Wongratana described these specimens after having collected them more than a decade earlier.

Pigmentation in preservative: The material we examined has lost most of their pigmentation in preservation except nuchal and black dorsal-fin markings. This dorsal-fin marking is present on the edges of the second through fifth spines; unfortunately, the membrane is broken between these spines. According to Wongratana (1988), ‘‘Preserved specimens light brown on body and head; markings on back and sides obscure, blotch on nape diffuse. Snout and pectoral axil dusky. Inner surface of opercle dotted with dark [sic]. Breast dusky; lower sides conspicuously paler below pectoral fins, dusky posteriorly. Black blotch on spinous dorsal fin distinct.’’ The reference to the pale area below the pectoral fins is what we refer to as the mitten-shaped, pigment-free area that is diagnostic of Nuchequula .

DISTRIBUTION: Currently known only from the type series, which was collected in the Gulf of Thailand. Additional specimens were reported from the Andaman Sea in the original description .

REMARKS: The relative length of the second and third dorsal-fin spines may be an additional diagnostic character for this species. In our examination of types, the third spines are about one-half to three-quarters the length of the second spines. If this difference in length can be confirmed in additional material, it would be diagnostic for Nuchequula pan , given that all other species of Nuchequula have second and third dorsal-fin spines of about equal length.

The prominent spinous dorsal-fin markings and horizontal lines on the flanks may suggest a close relationship between this species and N. nuchalis . These two species are the only members of Nuchequula that possesses horizontal markings on the flanks; however, in N. nuchalis these lines are not broken as they are in N. pan but continuous. In addition, the horizontal lines are more pronounced and are better retained in preservative in N. pan ( Wongratana, 1988) . The maximum size recorded for the species is that of the holotype at 65.0 mm SL, making it apparently the shortest Nuchequula species. Apart from the 10 specimens included in the type series, we were unable to locate any additional specimens of N. pan in museum collections.

Figures

Fig. 5. Fresh material from Tonshi Fish Market, Taiwan. (A) Two paratypes of Nuchequula mannusella, new species. (B) Nuchequula nuchalis.

Fig. 6. Illustrations: (A) Non-type Indian specimen of Nuchequula blochii from Day (1875). (B) Non-type Australian specimen of Nuchequula decora from Jones (1985). (C) Holotype of Nuchequula nuchalis from Temminck and Schlegel (1845). (D) Holotype of Nuchequula pan from Wongratana (1988).

Fig. 9. Holotype of Nuchequula nuchalis, RMNH 1287, 96.6 mm SL.

Fig. 1. Landmarks used for PCA: (1) rostral tip of premaxilla; (2) posterior end of nuchal spine; (3) anterior insertion of dorsal fin; (4) posterior insertion of dorsal fin; (5) dorsal insertion of caudal fin; (6) midpoint of caudal border of hypural plate; (7) ventral insertion of caudal fin; (8) posterior insertion of anal fin; (9) anterior insertion of anal fin; (10) dorsal base of pelvic fin; (11) ventral end of lower jaw articulation; (12) posterior end of maxilla; (13) anterior margin through midline of eye; (14) posterior margin through midline of eye; (15) dorsal end of opercle; (16) dorsal base of pectoral fin. Base figure modified from Nelson (2006).

Fig. 10. Holotype of Nuchequula pan, CUMZ 2528, 2, 9, 1, 65.0 mm SL.