Chelidoperca occipitalis Kotthaus, 1973

Matsunuma, Mizuki, 2016, Records of Chelidoperca maculicauda and C. occipitalis (Serranidae) from the Arabian Sea, with Comments on Diagnostic Characters, Species Diversity 21, pp. 161-170 : 168-170

Chelidoperca occipitalis Kotthaus, 1973

( Figs 1B , 2B , 3C–D , 4–6 ; Tables 1–2)

Chelidoperca occipitalis Kotthaus 1973: 30 , fig. 299 (type locality: southwest of Socotra Island, Yemen, Arabian Sea, 11°33.9′N, 52°54′E to 11°38′N, 52°52′E, Meteor station 102; Wilkens and Dohse 1993: 417 (type catalog of ZMH); Manilo and Bogorodsky 2003: S104 (Arabian Sea; listed); Bineesh et al. 2014: 119, figs 4–6 (Kollam, west coast of India; redescription); Bineesh et al. 2015: 104 (Kollam and Mangaluru, west coast of India; molecular phylogenetic analysis); Psomadakis et al. 2015: 195, pl. XII, fig. 99 ( Pakistan; short description).

Chelidoperca investigatoris (not of Alcock 1890): Said Koya 2010: 15, unnumbered fig. ( Calicut, west coast of India; listed).

Examined specimens. Six specimens, 65.9–89.9 mm SL: OMAN: USNM 389094 , 5 specimens, 65.9–89.1 mm SL, Gulf of Oman (23°33′N, 58°23′E), 106 m depth, RV Anton Bruun, International Indian Ocean Expedition, cruise 4B, station 269B, 3 December 1963 . INDIA: USNM 389097 , 89.9 mm SL, off India (22°14′N, 67°42′E), 104–108 m depth, RV Anton Bruun, International Indian Ocean Expedition, cruise 4B, station 220 A, 18 November 1963 .

Diagnosis. A species of Chelidoperca distinguished from other members of the genus by the following combination of characters: pectoral-fin rays 14–16 (modally 15); pored lateral-line scales 42 or 43; scale rows between lateral line and sixth dorsal-fin base 2.5; preopercular serrae 19–33; head length 41.3–43.2% (mean 42.2%) SL; postorbital length 22.3–23.6% (mean 23.0%) SL; interorbital scales just reaching forward to point above center of orbit; scales on ventral surface of lower jaw restricted to angular, not extending anteriorly onto dentary; upper margin of caudal fin with numerous short, dark bands (reddish when fresh); dark longitudinal dashed stripe present mid-laterally on side of body.

Description. Characters given in diagnosis not repeat- ed. Morphometric and meristic values given in Tables 1–2. Dorsal-fin rays X, 10; anal-fin rays III, 6; pelvic-fin rays I, 5. Caudal fin truncate, upper lobe with elongate, pointed tip; upper lobe with 3 unbranched and 7 or 8 branched segmented rays, lower lobe with 2 or 3 unbranched and 7 branched segmented rays, 19–21 (modally 20) total segmented rays. Scale rows above lateral line 3; cheek scale rows 6.

Body slightly elongated ( Fig. 1B ); snout pointed, dorsal profile of snout in lateral view forming angle of ca. 40° to horizontal axis of head and body; caudal peduncle relatively long. Orbit large, its dorsal margin included in dorsal contour of head. Mouth large, slightly oblique; posterior margin of maxilla extending beyond vertical through center of eye but not reaching to vertical through posterior margin of orbit; maxilla slightly expanded posteriorly, lateral ridge undeveloped; lower jaw slightly protruding beyond upper jaw when mouth closed. Upper jaw with band of ca. 6 rows of small, pointed conical teeth, outermost row with 20–26 relatively large canines; cluster of 15–17 enlarged canines on each side of symphysis. Lower jaw with band of 2–4 irregular rows of small, pointed conical teeth, outermost row with 10–12 enlarged canines, innermost row with 20–25 canines (shorter than outer canines); vomer with blunt, Vshaped band of 1 or 2 rows of small, pointed conical teeth, and several large canines posteriorly; palatine with relatively long, narrow band of ca. 2 rows of small, pointed conical teeth (width of band 5.7–6.5% SL). Anterior nostril on middle of snout, with small, rounded flap arising from posterior rim; posterior nostril an elliptical opening at anterior border of orbit. Opercle with 2 flat, prominent spines, upper spine clearly longer than lower, angle between them ca. 30°; interopercular serrae 3–9; subopercular serrae 10–19; posttemporal with small bony crest bearing 1–3 spines at beginning of lateral line.

Body with ctenoid scales; lateral line slightly arched over pectoral fin before gradually descending, terminating at caudal-fin base. Uppermost row of body scales along dorsal-fin base always about half size of those in adjacent row. Small cycloid scales on caudal- and pectoral-fin bases, not extending onto fins; no scales on dorsal-, anal- and pelvicfin bases. Row of small cycloid scales on each membrane between first and fourth dorsal-fin soft rays and membrane between third anal-fin spine and first anal-fin soft ray. Head generally with ctenoid scales but scales absent on snout and maxilla; scales on preopercle, interopercle, subopercle, and opercle ctenoid; interorbital region and ventral surface of lower jaw with cycloid scales.

Interorbital canals with numerous small pores running along outer margin of interorbital region, diverging outward anteriorly, and reaching to area between anterior and posterior nostrils; interorbital canal pores in ca. 2 irregular bilateral rows (i.e., ca. 2 rows on each side; Fig. 2B ). Ventral surface of lower jaw with 4 sets of sensory pores on each side; anteriormost pore simple, situated to side of mandibular symphysis, followed by 2 pairs of adjacent minute pores on dentary and then by more posterior complex of 2 or 3 minute pores situated anteriorly on angular.

Dorsal-fin origin above pectoral-fin base, fourth spine longest, ninth spine shortest; all soft rays branched, subequal in length, ninth longest. Anal-fin origin below base of second dorsal-fin soft ray, third spine longest; all soft rays branched, fifth longest. Pectoral fin with uppermost one or two rays unbranched, remaining rays branched, ninth longest, posterior tip of fin reaching vertical through anal-fin origin. Pelvic-fin origin below pectoral-fin base; spine covered with skin; all soft rays branched, second longest, expanded distally, its tip just reaching anus when depressed.

Color of preserved specimens. Head, body, and fins uniformly pale brown; mid-lateral body with narrow dashed dark stripe extending from posterior tip of gill cover to caudal-fin base. Upper part of spinous portion of dorsal fin dusky; soft-rayed portion with 2 or 3 longitudinal rows of small dark spots; 2 or 3 laterally elongate dark blotches on anteriormost part of soft-rayed portion. Upper margin of caudal fin with ca. 5–7 indistinct short, dark bands. No other markings on fins.

Distribution. Chelidoperca occipitalis has been record- ed from many localities along the Arabian Sea coast, including the west coast of India, Pakistan, the Gulf of Oman, and off Socotra Island near the mouth of the Gulf of Aden ( Kotthaus 1973; Bineesh et al. 2014; Psomadakis et al. 2015; this study; Fig. 3 ).

Identification. The present specimens generally agree with the descriptions of C. occipitalis given by Kotthaus (1973) and Bineesh et al. (2014). Chelidoperca occipitalis is characterized by usually having 15 pectoral-fin rays (vs. usually 16 in C. hirundinacea ), 42 or 43 pored lateral-line scales (vs. 34 or 35 in C. stella ), and 2.5 scale rows between the lateral line and the sixth dorsal-fin spine base (vs. 3.5 in C. hirundinacea , C. lecromi , C. pleurospilus , and C. maculicauda ). Moreover, C. occipitalis is distinguished from C. margaritifera by having a moderate number (19–33) of preopercular serrae (vs. 27–60 in the latter) ( Fig. 6A ).

In term of morphometric proportions, C. occipitalis can be distinguished from C. hirundinacea , C. lecromi , C. margaritifera , C. pleurospilus , C. santosi , and C. stella by its relatively longer head (41.3–43.2% SL vs. 34.2–40.0% SL in the latter species) and greater postorbital length (22.3–23.6% SL vs. 17.4–20.9% SL). It is further distinguished from these species as well as C. maculicauda by its relatively shorter upper caudal-peduncle length (15.8–16.7% SL vs. 17.6– 22.5% SL) ( Williams and Carpenter 2015; Matsunuma and Motomura 2016; this study). Although Bineesh et al. (2014) stated that C. occipitalis differs from C. pleurospilus in having an interorbital width that is exceeded 10.3–14.6 times by the head length (vs. <10.95 times in the latter species), no clear difference in this character was found between examples of the two species examined in this study (2.3–2.7% SL in the former vs. 2.1–2.9% SL in the latter).

Furthermore, whereas the interorbital scales of C. occipitalis just reach a vertical through the center of the eye, but they extend anteriorly well beyond this point in C. hirundinacea , C. investigatoris , C. lecromi , and C. maculicauda ( Bineesh et al. 2014; this study; Fig. 3C ). Moreover, C. occipitalis possesses scales only on the ventral surface of the angular, but the scaled area extends anteriorly onto the dentary in C. hirundinacea , C. maculicauda , and C. stella ( Fig. 3D ).

Chelidoperca occipitalis is characterized by a dark longitudinal dashed stripe situated mid-laterally on the body; in congeners a dark stripe occurs only in C. investigatoris and C. pleurospilus ( Bineesh et al. 2014; Williams and Carpenter 2015; Matsunuma and Motomura 2016; this study). Preserved specimens of C. occipitalis are also characterized by the following combination of markings: upper margin of caudal fin with ca. 5–7 short dark bands (reddish when fresh; Bineesh et al. 2014: fig. 5), and membrane between last spine and first soft ray of dorsal fin with 2 or 3 dark blotches (red when fresh) ( Bineesh et al. 2013, 2014; Williams and Carpenter 2015; Matsunuma and Motomura 2016; this study). Chelidoperca occipitalis is further characterized by the presence of a silvery streak along the posteroventral margin of the orbit when fresh ( Bineesh et al. 2014: fig. 5; Psomadakis et al. 2015: pl. XII, fig. 99), a characteristic shared only with C. lecromi among known congeners ( Bineesh et al. 2013, 2014; Williams and Carpenter 2015; Matsunuma and Motomura 2016; this study).

Remarks. The redescription of C. occipitalis given by Bineesh et al. (2014) based on the holotype and 14 nontype specimens included several inconsistencies, with the description stating “gill rakers 3+5–8+4” and “lateral-line scales 44”, and the accompanying Table 3 listing “total number of gill rakers 19–21” and “total number of tubed lateralline scales 43 or 44”. In addition, the diagnosis of C. occipitalis stated that there are 14 circumpeduncular scales whereas the description said 13 or 14. The specimens examined here possess 18 or 19 circumpeduncular scales. In addition, although Bineesh et al. (2014) stated that C. occipitalis lacks vomerine teeth, the holotype of C. occipitalis was originally described by Kotthaus (1973) as having vomerine teeth. All species of Chelidoperca possess a vomerine teeth patch ( Bineesh et al. 2013, 2014; Williams and Carpenter 2015; Matsunuma and Motomura 2016; this study).

Several differences in morphometric range were recognized between the present specimens and Bineesh et al. (2014), including the lengths of the snout (7.4–9.4% SL in the former vs. 8.9–10.9% SL in the latter), fourth dorsal-fin spine (15.3–16.5% SL vs. 12.7–15.9% SL), and longest pelvic-fin soft ray (25.5–28.2% SL vs. 22.3–23.9% SL). However, these differences may be due to ontogenetic changes within the species, as was demonstrated above for C. maculicauda ( Fig. 5C–D ).

Although Bineesh et al. (2014) stated that C. occipitalis had also been recorded from Veraval (northwestern India), and from Pakistan, these two records were based solely on personal communications. Psomadakis et al. (2015) subsequently recorded the species from Pakistan, supported by a color photograph of a collected specimen. A record of C. investigatoris from Calicut, southwestern India, accompanied by a figure ( Said Koya 2010) is identifiable as C. occipitalis , because it clearly has several reddish bands on the upper margin of the caudal fin. The present specimens of C. occipitalis from the Gulf of Oman, representing the first records of the species from that Gulf, indicate a wide distribution of the species in the Arabian Sea.

Comparative material. The following specimens examined in this study were listed in detail in Matsunuma and Motomura (2016): Chelidoperca hirundinacea (15 specimens, 48.5–144.3mm SL), Chelidoperca lecromi (2 specimens, 111.8–125.3 mm SL), Chelidoperca margaritifera (13 specimens, 45.1–90.2 mm SL), Chelidoperca pleurospilus (13 specimens, 57.9–122.4 mm SL), and Chelidoperca santosi (1 specimen, 81.6 mm SL). Additional material included C. margaritifera (8 specimens, 65.4–87.3mm SL): UPVMI 1169 , 84.3 mm SL, UPVMI 1170 , 87.3 mm SL, UPVMI 1171 , 87.0 mm SL, UPVMI 1172 , 86.8 mm SL, UPVMI 1173 , 78.1 mm SL, UPVMI 1174 , 77.6 mm SL, UPVMI 1175 , 75.7 mm SL, UPVMI 1176 , 65.4 mm SL, off Antique, Panay Island , Philippines, 30 July 2014.

Figures

Fig. 1. Preserved specimens of (A) Chelidoperca maculicauda, USNM 306446, one of two specimens, 103.9mm SL, off Somalia, Gulf of Aden, and (B) C. occipitalis, USNM 389094, one of five specimens, 89.1mm SL, off Oman, Gulf of Oman.

Fig. 2. Semi-schematic illustrations illustrating differences in scale rows between lateral line and dorsal-fin base in (A) Chelidoperca maculicauda, USNM 306452, one of three specimens, 87.0mm SL, and (B) C. occipitalis, USNM 389097, 89.9mm SL. Shaded scales counted as 0.5. Closed and open arrowheads indicate the dorsal-fin origin and pored lateral-line scale, respectively. Bars equal 3mm.

Fig. 3. Semi-schematic illustrations of dorsal views of head (A, C) and ventral views of lower jaw (B, D) showing squamation differences in (A–B) Chelidoperca maculicauda, USNM 306446, one of two specimens, 103.9mm SL and (C–D) C. occipitalis, USNM 389094, one of five specimens, 84.5mm SL. AN and PN indicate the anterior and posterior nostrils, respectively. Bars equal 3mm.

Fig. 4. Distributional map of Chelidoperca maculicauda (squares) and C. occipitalis (circles). Open and closed symbols indicate previously reported and new records, respectively. Note: Psomadakis et al. (2015) recorded C. occipitalis from the Pakistan coast.

Fig. 5. Relationships of head length (A), postorbital length (B), snout length (C), and longest pelvic-fin soft ray length (D) (all as % of standard length) to standard length (mm) in Chelidoperca hirundinacea (diamonds), C. lecromi (crosses), C. occipitalis (circles), C. maculicauda (squares), C. margaritifera (circles with cross), C. pleurospilus (downward-pointing triangles), C. santosi (star), and C. stella (upward-pointing triangles), showing interspecific differences (A–B) and growth-related changes within the species (C–D). Open symbols indicate the type series of C. occipitalis (circles), the holotype of C. maculicauda, and a non-type specimen reported by Bineesh et al. (2014: table 2) (squares).

Fig. 6. Relationships of numbers of preopercular serrae (A) and interopercular serrae (B) to standard length (mm) in Chelidoperca hirundinacea (diamonds), C. lecromi (crosses), C. maculicauda (squares), C. margaritifera (circles with cross), C. occipitalis (circles), C. pleurospilus (downward-pointing triangles), C. santosi (stars), and C. stella (upward-pointing triangles).