Aetobatus flagellum (Bloch & Schneider, 1801)

White, William T. & Moore, Alec B. M., 2013, Redescription of Aetobatus flagellum (Bloch & Schneider, 1801), an endangered eagle ray (Myliobatoidea: Myliobatidae) from the Indo – West Pacific, Zootaxa 3752 (1), pp. 199-213 : 201-207

Aetobatus flagellum (Bloch & Schneider, 1801)

( Figures 1–6 , Table 1)

Raja flagellum Bloch & Schneider, 1801: 361 , pl. 73 (Coromandel Coast, India).

Aetobatis narinari— Day, 1878 (in part): 743, pl. 194, fig. 4 (misidentification, India).

Aëtobatis narinari— Day, 1889: 59–60, fig. 24; Blegvad, 1944: 55–56, fig. 23 (brief description, illustration after Day, 1878) (misidentification, Persian Gulf).

Aëtobatis flagellum— Annandale, 1909: 54–58, fig. 10a, pl. (fig. 5) (off Orissa Coast and Chilka Lake)

Aetobatis flagellum— Fowler, 1930: 507 (Hawaii; Indian Ocean)

Aetobatus narinari (in part) — Fowler, 1941: 471; Misra, 1947: 40; Dor, 1984: 20.

Syntypes. ZMB 7845, male, coast of Coramandel, India, collected by M.E. Bloch; ZMB 31560, male, Tharangambadi (formerly Tranquebar), coast of Coramandel, India, collected by M.E. Bloch.

Other material examined. (20 specimens): BMNH 89.2.1.4205-8, 5 specimens (female 243 mm DW [653 mm TL], immature male 233 mm DW [548 mm TL], female 369 mm DW [1082 mm TL], female 289 mm DW [796 mm TL], female 290 mm DW), Madras (possibly), India; CSIRO H 4426–14, subadult male 446 mm DW, Muara Angke fish landing site, Jakarta, Indonesia, 17 Oct. 1995, collected by P. Last; CSIRO H 5485–02, immature male 350 mm DW (1017 mm TL), Kuching fish market, Sarawak, Malaysia, 0 2 May 1999, collected by P. Last & M. Manjaji; CSIRO H 6134–01, subadult male 431 mm DW (1260 mm TL), Muara Angke fish landing site, Jakarta, Indonesia, 20 May 2002, collected by W. White & Dharmadi; CSIRO H 6662–03, immature male 346 mm DW (1156 mm TL), CSIRO H 6662–04, immature male 306 mm DW (956 mm TL), CSIRO H 6662–05, female 326 mm DW, CSIRO H 6662–06, immature male 305 mm DW (1027 mm TL), Muara Baru fish landing site, Jakarta, Indonesia, 19 Apr. 2004, collected by W. White & Dharmadi; CSIRO H 7252–01, female 388 mm DW (1029 mm TL), Persian (Arabian) Gulf, Sharq fish market, Kuwait City, Kuwait, 29°23′ N, 47°58′ E, probably caught off Kuwait in <40 m, 0 1 Apr. 2011, collected by A. Moore; CSIRO H 7253–01, immature male 304 mm DW (853 mm TL), Persian (Arabian) Gulf, Sharq fish market, Kuwait City, Kuwait, 29°23′ N, 47°58′ E, probably caught off Kuwait in <40 m, 0 5 Apr. 2011, collected by A. Moore; MNHN 0000–2355 (largest of 2), immature male 322 mm DW (866 mm TL), Pondicherry, Coromandel Coast, India, 11°59’ N, 79°50’ E, collected by Boulenger; MNHN A-7949, adult male 543 mm DW, MNHN A-7957, female 578 mm DW (1392 mm TL), MNHN A-7958, 3 specimens (immature male 366 mm DW, female 301 mm DW [800 mm TL], immature male 329 mm DW [826 mm TL]), Malabar Coast, Northern Kerala, India, 11°00’ N, 76°00’ E, collected by Dussumier.

Specimens examined but not retained. female 746 mm DW, Persian (Arabian) Gulf, Sharq fish market, Kuwait City, Kuwait, 29°23′ N, 47°58′ E, probably caught off Kuwait in <40 m, 13 Apr. 2011, collected by A. Moore; male 570 mm DW (tissue accession GT2373, BW-A6099), Persian (Arabian) Gulf, Sharq fish market, Kuwait City, Kuwait, 2923′ N, 47°58′ E, probably caught off Kuwait in <40 m, 19 Apr. 2008, collected by A. Moore.

Specimens not examined but with images verified. USNM 206131, Caraioor fish market, near Jaffna Fort, Sri Lanka, 17 Mar. 1970; USNM 222684, fish market at Kalupittiya, Sri Lanka, 25 Jan. 1970, collected by C.C. Koenig; USNM 222690, St John’s fish market, Colombo, Sri Lanka, 23 May 1970, collected by T. Iwamoto.

Diagnosis. A small Aetobatus (attaining about 900 mm DW) with the following combination of characters: dorsal surfaces uniformly brownish, without pale spots; tail very long (1.22–2.81 times DW); stinging spine(s) relatively long (6.2–16.2% DW); head long; rostral lobe long to very long (longest in adult males) with a narrowly pointed apex; teeth plates in a single row, those in lower jaw chevron-shaped; width of lower tooth plate about two thirds mouth width; pectoral-fin radials 89–96 (excluding propterygial radials anterior of eyes); total vertebral centra (including synarcual) 85–91; males mature by about 500 mm DW and females by about 746 mm DW.

n=20

Min. Max. Mean Disc width (mm) 233 578 353.25 Total length 178.1 336.7 274.3 Pre-dorsal length 55.7 68.5 61.5 Disc, length 55.3 70.0 62.1 Snout to pectoral-fin insertion 49.4 63.0 54.9 Disc thickness 9.5 12.8 11.2 Snout to pectoral-fin origin 13.8 20.4 17.7 Posterior orbit to pectoral-fin insertion 39.5 45.8 42.2 Snout to maximum width (horiz.) 38.2 45.7 42.8 Pectoral-fin anterior margin 48.8 52.7 50.5 Pectoral-fin posterior margin 45.1 50.4 47.6 Pectoral-fin base length 38.2 43.8 40.7 Pectoral-fin inner margin 5.8 8.1 7.1

......continued on the next page n=20 Description. Disc diamond-shaped, broad but relatively short, width about 1.33–1.81 times disc length; anterior projection 3.15–4.22 in disc length; axis of greatest width of disc well posterior to scapular region, over abdominal cavity, its horizontal distance from snout tip 1.18–1.40 times in distance from tip of snout to pectoral-fin insertion; moderately deep, greatest thickness above scapular region and posterior head, thickness 7.83–10.57 in disc width; without denticles, or thorns; with a short, bony ridge on midline above scapular region. Pectoral fins very large, winglike, narrowly triangular, weakly falcate; anterior margin concave basally, nearly straight for first two thirds, slightly to moderately convex distally; apex narrowly rounded to subangular, pectoral angle 54–61°; posterior margin moderately concave near apex, almost straight posteriorly; free rear tip broadly rounded; inner margin convex distally, becoming nearly straight basally; length of anterior margin 48.8–52.7% DW, 1.17–1.31 times its base length, inner margin 4.87–6.91 in its base; origin over anterior edge of spiracles; apex located just posteriorly to pectoral mid-base; insertion just posterior to pelvic-fin origin; free rear tip partly overlapping pelvic-fin anterior margin.

Head pronounced, deep, short and relatively narrow; projecting well anterior to pectoral-fin origins; subquadrangular in cross-section at pectoral-fin origin; cranial region of head broadly rounded in dorsoventral view; chondrocranium pronounced above eyes and spiracles; snout abruptly convex anterior of eyes, becoming deeply concave at origin of rostral lobe; slightly convex ventrally; ventral head length 26.0–33.5% DW, 1.46–2.23 times width at pectoral-fin origins, 2.96–6.36 times preorbital length (horizontal), 2.39–3.39 times interorbital width; preoral snout length 0.99–2.30 times mouth width, 1.73–2.99 times internarial width, 0.50–0.99 times distance between first gill slits; head width at pectoral-fin origin 14.8–17.8% DW, 1.58–1.93 times its height. Rostral lobe fleshy, long (very long in adult males); narrowly parabolic in dorsoventral view with a narrowly pointed apex; narrowly pointed in lateral view; its length 3.6–9.4% DW, 3.57–7.28 in head length, its width 1.38– 1.98 in head width at pectoral-fin origin.

Interorbital space moderately broad, convex but with a broad medial depression, without ridges, denticles or thorns; interorbital width 9.2–11.0% DW, 1.72–2.37 times orbit length, 0.63–0.81 times head width at mid-eye. Eyes small, subcircular, very slightly ventrolateral on head; orbit level or only slightly elevated above dorsal head profile, diameter 2.12–3.08 in spiracle length, 5.84–8.78 in head width at pectoral-fin origin. Spiracles large, suboval to elliptical, situated dorsolaterally posterior to orbit and above pectoral-fin origin, more visible dorsally than laterally; margins without any protuberances or folds; length 4.8–6.8% DW, 2.08–3.75 times width.

Nostril narrowly suboval, immediately preceded by a broad, shallow, fleshy depression bordering anterolateral margin of the nasal curtain; anterior nasal fold thin, membranous, internal; deep oronasal groove present; internarial space 1.26–2.25 in prenasal length, 1.18–2.28 times nostril length. Nasal curtain large, elongate, lobate, width 1.32–1.94 times length; lateral margin concave, smooth edged; posterior margin divided by deep medial notch, bordered by a long, curtain-like fringe, not following contour of lower jaw; posterior margin of each lobe convex with apices narrowly rounded; most of surface finely papillate, covered with minute pores centrally; apex and posterolateral margin recessible within oronasal groove.

Mouth moderate-sized, transverse, located ventrally, width 6.5–8.9% DW, 0.44–1.01 times preoral length, 1.92–2.63 in head width at pectoral-fin origin; not protrusible, anterior teeth of lower jaw visible when mouth closed; buccal region intricately papillate; skin on chin and at margin of lower jaw fleshy, strongly furrowed, papillate, indented slightly at symphysis. Teeth in a single row in each jaw, coalesced to form plates; about 6 narrow, almost straight teeth in upper jaw, tooth plate well inside palate, its length about half its width (based on CSIRO H 4426–14); about 13 narrow, chevron-shaped teeth in lower jaw, tooth plate protruding distally, its length more than twice its width, its width about two thirds mouth width (based on CSIRO H 4426–14); roof of mouth with 2 rows of oral papillae, those in outer row slightly larger than those of inner row; floor of mouth near lingual margin of lower tooth plate with lunate fringe of about 16 variably shaped (usually pointed), irregular oral papillae. Gill openings small, elongated S-shaped, forming a weakly fringed lobe laterally; length of first gill slit 0.95–1.70 times length of fifth gill slit, 2.36–4.61 in mouth width; distance between first gill slits 2.86–3.95 times internarial space, 0.45–0.64 times ventral head length; distance between fifth gill slits 1.78–2.45 times internarial distance, 0.45–0.64 times ventral head length.

Pelvic fins moderately large, slender, subquadrangular, anterior margin slightly concave to almost straight, apex moderately angular, posterior margin moderately convex, free rear tip broadly rounded, inner margin slightly convex; extending well beyond pectoral-fin free tips; pelvic-fin length 14.3–18.7% DW, 1.12–1.74 times width across fin bases, inner margin 9.0–13.3% DW. Claspers of adult male (MNHN A7949) relatively short, outer length 6.4% DW.

Dorsal fin small, strongly raked, its origin posterior to pelvic-fin insertions by about half to two-thirds its fin base; anterior margin almost straight; apex broadly rounded, posterior to insertion of fin; posterior margin convex to nearly straight; free rear tip subangular, inner margin very short, nearly straight; predorsal length 1.46–1.80 in disc width, fin length 4.7–7.8% DW, height 0.35–0.67 times its length, inner margin 2.77–10.4 in fin length.

Tail very long, slender, whip-like, its length (from cloaca origin) 1.22–2.81 times disc width; tapering gradually at base to stinging spine, and gradually becoming more whip-like beyond sting; base moderately compressed, suboval in cross section at pelvic-fin insertion, tail width at pelvic insertion 0.73–1.20 times height; almost rhomboidal in cross section near origin of stinging spine, width 0.59–1.36 times height at first spine origin; no skin folds present; a weak naked groove on dorsal surface of tail immediately posterior to base of stingingspine(s), almost fully housing spines. Stinging spines 0–2, very elongate, slender, moderately broad-based, strongly tapered, almost fully serrated laterally; distance from sting base to pectoral-fin insertion 10.4–14.8% DW; longest stinging spine 9.4–16.2% DW, 1.86–3.44 times dorsal-fin length.

Vertebral centra total (including synarcual) 85–91 (n=7); total (excluding synarcual) 80–87 (n=7); monospondylous (including synarcual) 33–42 (n=8); monospondylous (excluding synarcual) 29–38 (n=8); predorsal diplospondylous 13–29 (n=4); post-dorsal diplospondylous 27–34 (n=3). Total pectoral-fin radials (excluding propterygial radials anterior of eyes) 89–96 (n=7); propterygium (anterior of eyes) 13*–16*, propterygium (posterior of eyes) 10–14, mesopterygium 27–33, metapterygium 48–54. Pelvic-fin radials: 1 (4–6 fused elements) + 14–16 (n=7).

Colour (when fresh). Dorsal surface uniformly brownish (sometimes greenish brown), without distinct markings; eye bluish black; dark (dorsal) and pale (ventral) surfaces well demarcated (waterline) at pectoral-fin origin at junction with head; waterline extending anteriorly to mid eye and onto forehead; dark dorsal surface on rostral lobe similar, contrasted with its paler ventral surface and posteriorly with pale mid-snout; tail uniform greyish brown. Ventral surface mostly whitish; broad brownish margin along most of disc, junction between brown margin and whitish ventral colour strongly mottled, broadest on posterior margin, narrowest anteriorly; distal third of pelvic fins brownish; rostral lobe mostly whitish, anteriormost margin narrowly brownish.

Size. The male and female specimens of A. flagellum measured in this study ranged in size from 233–543 and 243–578 mm DW, respectively. Two male specimens of 431 and 446 mm DW were adolescent, and one specimen of 543 mm DW was mature. Moore et al. (2012) reported 36 individuals from the Persian Gulf with males and females ranging from 277–580 and 330–746 mm DW, respectively; males mature by ~ 500 mm DW. Birth size unknown; smallest free-swimming individual examined was 233 mm DW. Specimens of up to 900 mm DW have been recorded from northern Kuwait (J. Bishop, Kuwait Institute for Scientific Research, unpubl. data). Sujatha (2002) recorded two specimens off Visakhapatnam in northeastern India, which were 790 and 830 mm DW, but no sex was given. A single female of 746 mm DW (not retained), was mature and had functional, but empty, uteri.

Distribution. Patchily distributed in the Indo –West Pacific; known from the Western Indian Ocean, from Kuwait in the Persian Gulf to Pakistan and India; and the Eastern Indian Ocean, from India and Sri Lanka to Indonesia (Kalimantan) and Malaysia ( Sarawak). Not recorded from the east coast of South Africa (S. Dudley, KwaZulu-Natal Sharks Board, pers. comm. July 2009), Madagascar (A.J. Cooke, Blue Ventures, pers. comm.; Robinson & Sauer, 2013), Oman (Randall, 1995; Henderson & Reeve, 2011) nor the southern Persian Gulf (Moore et al., 2012; A. Moore unpubl. data). Reported presence in the Red Sea (Bonfil & Abdallah, 2004) was not based on records (R. Bonfil, pers. comm.) and requires confirmation, as it has not been reported previously from this region (Gohar & Mazhar, 1964). The Red Sea records are possibly due to its inclusion (mistakenly) as a synonym of A. narinari in species lists for the Red Sea (e.g. Fowler, 1956; Dor, 1984). Compagno & Last (1999) mentioned that records of A. flagellum from Hawaii and the Eastern Atlantic require confirmation. During this study, no specimens or accurate records of this species from these two regions were found and experts on the chondrichthyans faunas of Hawaii (J. Randall, BPBM, pers. comm. July 2009) and West Africa (B. Serét, pers. comm. March 2009) had no records. Records of this species from southern China require validation.

Figures

FIGURE 1. Aetobatus flagellum. A. original illustration from Bloch & Schneider (1801); B. dorsal view of stuffed syntype ZMB 31560.

FIGURE 2. Dorsal view of Aetobatus flagellum. A. CSIRO H 6662 – 03 (immature male 346 mm DW); B. not retained fresh specimen from Kuwait (female ~ 500 mm DW).

FIGURE 3. Ventral view of Aetobatus flagellum, CSIRO H 6134 – 01 (subadult male 431 mm DW).

FIGURE 4. Ventral view of the head of Aetobatus flagellum, CSIRO H 6134 – 01 (subadult male 431 mm DW).

FIGURE 5. Illustration of the tooth plates of Aetobatus flagellum (CSIRO H 4426 – 14, subadult male 446 mm DW). A. upper; B. lower. Drawings by Lindsay Marshall.

FIGURE 6. Dorsal view of the head of Aetobatus flagellum, MNHN A- 7949 (adult male 543 mm DW).