Chelidoperca maculicauda Bineesh and Akhilesh, 2013

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 : 162-168

Chelidoperca maculicauda Bineesh and Akhilesh in Bineesh et al., 2013

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

Chelidoperca maculicauda: Bineesh and Akhilesh in Bineesh et al. 2013: 71, figs 1–6 (type locality: off Kollam, Kerala, India); Bineesh et al. 2015: 104 (off Kollam, Kerala, India; molecular phylogenetic analysis based on type specimens).

Examined specimens. Eight specimens, 85.3–114.2 mm SL (all from Somalia, Gulf of Aden, western Arabian Sea): USNM 306446 , 2 specimens, 103.9–114.2 mm SL, off Habo, 11°50′42″N, 50°22′12″E, 165–208 m depth, coll . G . Small , RV Beinta, cruise 19, station HAUL 27 , bottom trawl, 17 February 1987; USNM 306448 , 3 specimens, 85.3–91.3mm SL, off Bosaso, 11°17′42″N, 48°57′24″E, 179 m depth, coll . G . Small and J . Small , RV Beinta, cruise 19, station HAUL 30 , bottom trawl, 18 February 1987; USNM 306452 , 3 specimens, 85.7–89.1 mm SL, off Habo, 11°43′42″N, 50°28′48″E, 160 m depth, coll . G . Small , RV Beinta, cruise 18, station HAUL 24 , prawn trawl, 17 January 1987 .

Diagnosis. A species of Chelidoperca distinguished from other members of the genus by the following combination of characters: pectoral-fin rays 14 or 15 (modally 15); pored lateral-line scales 42–44 (modally 44); scale rows between lateral line and sixth dorsal-fin spine base 3.5; total gill rakers including all rudiments 20–22 (modally 20); preopercular serrae 28–43; interopercular serrae 2–7; head length 40.6–43.3% (mean 41.9%) SL; postorbital length 22.6–23.6% (mean 23.2%) SL; upper caudal fin lobe expand- ed posteriorly with well-rounded contour; interorbital scales extending anteriorly well beyond center of orbit; scales on ventral surface of angular extending anteriorly onto dentary; 1 or 2 dark spots on upper lobe of caudal fin; longitudinal row of dark blotches laterally on 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 rounded, slightly expanded posteriorly; upper lobe with 2 unbranched and 8 branched segmented rays, lower lobe with 2 or 3 unbranched and 7 branched segmented rays, 19 or 20 (modally 20) total segmented rays. Scale rows above lateral line 4; cheek scale rows 6.

Body slightly elongated ( Fig. 1A ); 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 vertical through posterior margin of orbit; maxilla expanded posteriorly, with low lateral ridge diverging posteriorly into two ridges in large specimens; lower jaw slightly protruding beyond upper jaw when mouth closed. Upper jaw with band of ca. 5 rows of small, pointed conical teeth, outermost row with 15–18 relatively large canines; cluster of 10–18 enlarged canines on each side of symphysis. Lower jaw with band of 1–3 rows of small, pointed conical teeth, outermost row with 9–18 enlarged canines, innermost row with 22–28 canines (shorter than outermost canines); vomer with blunt, V-shaped band of 2–3 rows of small, pointed conical teeth, and several large canines posteriorly; palatine with relatively long, broad band of 3–4 rows of small, pointed conical teeth (width of band 6.2–8.0% SL). Anterior nostril at middle of snout, with small rounded flap arising from posterior rim; posterior nostril an elliptical opening at anterior border of orbit. Opercle with 2 prominent flat spines, upper spine slightly longer than lower; angle formed by upper and lower spines ca. 40°; subopercular serrae 5–19; posttemporal with small bony crest bearing 2–6 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 dorsalfin base always about half size of those in adjacent row ( Fig. 2A ). Small cycloid scales on caudal- and pectoral-fin bases, not extending onto fins; no scales on dorsal-, anal- and pel- vic-fin bases; no scales on dorsal- and anal-fin membranes. Head generally with ctenoid scales (absent on snout and maxilla); scales on preopercle, interopercle, subopercle, and opercle also 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 vertical through posterior nostril; interorbital canal pores in 2 irregular bilateral rows (i.e., ca. 2 rows on each side; Fig. 3A ). Ventral surface of lower jaw with 4 single or double 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 slit-like posteriormost 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, eighth or 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 three rays unbranched, remaining rays branched, eighth to tenth 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 reaching anus when depressed but not reaching anal-fin origin.

Color of preserved specimens. Head, body, and fins generally pale brown, body with longitudinal mid-lateral row of about 5 indistinct dark, elongate blotches from behind opercle to caudal-fin base ( Fig. 1A ). Dorsal-fin spines dusky; membrane of spinous portion dusky basally, small dark blotch distally on membrane between last spine and first soft ray, this spot much smaller than spot on caudalfin upper lobe; tip of first soft ray with minute dark blotch. Caudal fin with 4 or 5 rows of transverse narrow dark bands and inner row of numerous small semi-translucent spots; small dark spot (sometimes with additional minute dark spot) on upper lobe. Other fins without markings. Fresh coloration described by Bineesh et al. (2013).

Distribution. The species has been recorded from off Kollam, Kerala coast, southwestern India (type locality; Bineesh et al. 2013, 2015), and off Somalia, Gulf of Aden (this study), in the Arabian Sea ( Fig. 4 ).

Identification. The present specimens are identical with C. maculicauda , having the diagnostic features of the species recognized by Bineesh et al. (2013) and additional characters recognized in this study (see below). Chelidoperca maculicauda is characterized by 15 (rarely 14) pectoral-fin rays (vs. 16 or 17 in C. hirundinacea ), 42–46 pored lateralline scales (vs. 34 or 35 in C. stella ), 3.5 scale rows between the lateral line and sixth dorsal-fin spine base (vs. 2.5 in C. investigatoris , C. margaritifera , C. occipitalis , and C. stella ) and 20–22 total gill rakers including rudiments [vs. 16 or 17 in C. lecromi , 16–19 in C. occipitalis [19–21 in Bineesh et al. (2014) as discussed in the following Remarks], 16–19 in C. pleurospilus , and 17–19 in C. stella ] ( Bineesh et al. 2014; Williams and Carpenter 2015; Matsunuma and Motomura 2016; this study). Bineesh et al. (2013) stated that C. maculicauda can be distinguished from C. pleurospilus by gill raker number [3+9 vs. 5–6+ 11–12 in the latter ( Akazaki 1972)]; however, the counts for C. maculicauda in Bineesh et al. (2013) were for developed gill rakers only, while Akazaki’s (1972) counts may have included rudiments. The total numbers of gill rakers including rudiments observed in comparative specimens of C. pleurospilus for the present study (5–6 + 11–13) agree those of Akazaki (1972), rather than with a count of developed gill rakers only (2–3+8–9), supporting this contention. Additionally, C. maculicauda was originally diagnosed as having X, 10 dorsal-fin rays and III, 6 anal-fin rays ( Bineesh et al. 2013). As all currently known species of Chelidoperca possess the same dorsal- and anal-fin ray counts ( Senou 2013; Bineesh et al. 2014; Williams and Carpenter 2015; Matsunuma and Motomura 2016; this study), these counts are useful only for the generic diagnosis.

Regarding morphometric proportions, C. maculicauda has greater postorbital 22.6–23.6% SL [23.7–24.7% SL in Bineesh et al. (2013)] and head lengths 40.6–43.3% SL [40.3–42.6% SL in Bineesh et al. (2013)], compared with congeners (17.4–20.9 and 34.2–40.0% SL, respectively), with the exception of C. investigatoris (24.9–28.5 and 41.9–48.7% SL, respectively) and C. occipitalis (22.3–24.9 and 41.3– 44.7% SL, respectively) ( Bineesh et al. 2014; Williams and Carpenter 2015; this study; Fig. 5A–B ). Although Bineesh et al. (2014) considered C. maculicauda to be distinguishable from C. pleurospilus by body depth (22.8–24.3% SL vs. 22.7–23.1% SL in the latter) and from C. occipitalis by eye diameter (10.8–11.6% SL vs. 9.1–10.6% SL in the latter), the ranges of body depth measurements clearly overlap and no clear differences in the above characters were observed between species pairs in the present study (see also Table 2). Chelidoperca maculicauda was also originally diagnosed by several other morphometrics, including the lengths of the fourth dorsal-fin spine, longest dorsal-fin soft ray, first and second anal-fin spines, and pelvic fin, but Bineesh et al. (2013) did not detail interspecific differences for these characters. Accordingly, these morphometric features are excluded from the diagnosis of C. maculicauda presented here. Furthermore, although Bineesh et al. (2013) stated in their diagnosis of the species that the head length of C. maculicauda is 3.16–3.54 times the length of the second anal-fin spine, the statement appears erroneous, since a recalculation of the measurements for the type series ( Bineesh et al. 2013: table 1) yields a head length of ca. 5.5–6.6 times the spine length.

The number of serrae on some head bones is also useful for identifying species of Chelidoperca ( Akazaki 1972; Matsunuma and Motomura 2016). Chelidoperca maculicauda is distinguished from C. margaritifera by its moderate number of preopercular serrae (28–43 in the present 85.3–114.2 mm SL specimens and 40–46 in the 153.4–160.7 mm SL type specimens reported by Bineesh et al. (2013)], compared with 45–60 serrae in 80–90 mm SL specimens of the latter species ( Fig. 6A ). Further interspecific comparisons based on specimens of> 80 mm SL revealed C. maculicauda to have fewer interopercular serrae 2–7, compared with 6 or more in most congeners (data not available for C. investigatoris and limited to two examples of C. lecromi ) ( Williams and Carpenter 2015; Matsunuma and Motomura 2016; this study; Fig. 6B ). Although Bineesh et al. (2013) stated that C. maculicauda differs from C. pleurospilus in having more preopercular serrae, the trend though apparent a clear-cut separation of the two species was not observed ( Fig. 6A ).

The extent of squamation in the interorbital region and on the ventral surface of the lower jaw is also helpful for species identification in Chelidoperca ( Akazaki 1972; Matsunuma and Motomura 2016; this study). Chelidoperca maculicauda is characterized by interorbital scales that extend anteriorly beyond the mid-orbit and reach the anterior margin of the orbit in dorsal view (vs. just reaching to a position above mid-orbit in C. margaritifera , C. occipitalis , C. pleurospilus C. santosi , and C. stella ), and by scales on the ventral surface of the angular that extend anteriorly onto the posterior part of the dentary (anterior to the posteriormost mandible pore) (vs. only the angular being scaly in C. occipitalis and C. pleurospilus ) ( Bineesh et al. 2013, 2014; Williams and Carpenter 2015; Matsunuma and Motomura 2016; this study; Fig. 3 ).

As noted by Bineesh et al. (2013), C. maculicauda possesses unique caudal fin markings: 1 or 2 dark spots (grey in fresh condition; Bineesh et al. 2013) on the upper lobe and several rows of numerous small, semi-translucent spots (bluish-white in fresh condition; Bineesh et al. 2013), while congeners lack this combination of markings ( Bineesh et al. 2014; Williams and Carpenter 2015; Matsunuma and Motomura 2016; this study). Chelidoperca maculicauda is also distinguished from its congeners in having the upper caudal fin lobe expanded posteriorly with a well-rounded contour, in contrast to a truncated fin with the upper lobe elongat- ed and pointed in other species ( Alcock 1894: pl. X, fig. 10; Bineesh et al. 2013, 2014; Williams and Carpenter 2015; Matsunuma and Motomura 2016; this study).

Remarks. Several differences in meristic and morphometric characters were found between the present specimens and the original description of C. maculicauda . Bineesh et al. (2013) stated that C. maculicauda possesses 2.5 or 3 scale rows between the lateral line and the tenth dorsal-fin spine base, compared with 3.5 rows observed during the present study ( Fig. 2A ). It is likely that Bineesh et al. (2013) overlooked or misidentified the dorsal-most row of small scales above the lateral line. Other minor differences in counts between the present specimens and those available to Bineesh et al. (2013), including the numbers of total developed gill rakers (2+ 9–10 in the former vs. 3+ 9 in the latter) and pored lateral-line scales (42–44 vs. 42), can be attributed to an inadequate sample size.

The present specimens also differ from those of Bineesh et al. (2013) in having a slightly shorter snout (7.3–8.2% SL vs. 8.6–8.8% SL in the latter) and relatively longer fin rays, including the fourth dorsal-fin spine (15.4–17.3% SL vs. 14.2–14.6% SL), first anal-fin soft ray (13.2–16.1% SL vs. 12.0–13.3% SL), longest pectoral-fin ray (26.0–28.8% SL vs. 24.5–25.5% SL), longest pelvic-fin soft ray (26.4–30.1% SL vs. 21.7–24.9), and caudal-fin (23.8–27.8% SL vs. 22.5– 24.8% SL). However, an analysis of those measurements (expressed as percentages of SL) indicated the occurrence of growth-related changes in some body proportions. In particular, the snout length tends to increase proportionally with growth ( Fig. 5C ) in C. maculicauda , whereas lengths of the dorsal-fin spines, first anal-fin soft ray, longest pelvicfin soft ray and caudal fin all decrease proportionally with growth ( Fig. 5D ).

Among congeners, similar ontogenetic trends were also recognized in this study in the examined samples of C. hirundinacea , C. margaritifera , C. occipitalis , and C. pleurospilus . No growth-related changes were recognized in pectoralfin length, either in C. maculicauda or the same congeners. Accordingly, the morphometric differences between the present specimens and those of Bineesh et al. (2013) are regarded as either size-related ontogenetic changes or individual variation. Although the present specimens also differ from those of Bineesh et al. (2013) in having a slightly narrower interorbital width (3.0–3.7% SL vs. 4.6–4.8% SL in the latter), this is likely due to different measuring techniques. Interorbital width in the present study is the “least bony width” whereas that of Bineesh et al. (2013) may represent the fleshy width.

Chelidoperca maculicauda was originally described by Bineesh et al. (2013) on the basis of three specimens collect- ed off Kollam, southwest coast of India. Since no specimenbased records of the species have been reported since, the present specimens from the Gulf of Aden represent the first records of the species from that region ( Fig. 4 ).

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).