Torpedo formosa, Diane L. Haas & David A. Ebert, 2006

Diane L. Haas & David A. Ebert, 2006, Torpedo formosa sp. nov., a new species of electric ray (Chondrichthyes: Torpediniformes: Torpedinidae) from Taiwan., Zootaxa 1320, pp. 1-14 : 2-11

Torpedo formosa , sp. nov.

Taiwan torpedo ray

(Figures 1-3, table 1)

Torpedo nobiliana : Chen & Chung, 1971, p. 1, fig. 4; Chen & Joung, 1993, p. 78; Chiu, 1994, p. 135; Huang, 2001, p. 409.

Holotype: CAS 223471, 332 mm TL, immature male, Tahsi Fish Market, Tahsi, Taiwan, 24°53’N, 122°01’E, collected by David A. Ebert, 9 April 1988.

Paratypes: 2 specimens. CAS 223472, 243 mm TL immature male, Tahsi Fish Market, Tahsi, Taiwan, 24°53’N, 122°01’E, collected by David A. Ebert, 12 April 1988 ; CAS 223473, 241 mm TL female, Tahsi Fish Market, Tahsi, 24°53’N, 122°01’E, Taiwan, collected by David A. Ebert, 25 May 2005 .

Diagnosis. A medium sized Torpedo distinguished by the following combination of characters: disc wider than long, length 82-88% of disc width; preorbital snout length 7.7-8.7% of total length; dorsal head length 19.8-20.6% of total length; spiracles smooth and moderately long, length 3.6-3.8% of disc length; relatively wide nasoral region, internarial width 5.5-5.6% of total length; dorsal fins broadly rounded and robust; caudal fin height greater than distance from its own upper origin to first dorsal origin; trunk vertebrae 25-27; dorsal surface uniform purplish-brown in life; ventral surface cream, abruptly darker on posterior disc margin.

Description. Disc broadly rounded, anterior margin nearly straight in outline with very slight median protuberance. Disc width greater than length; disc width 63.6% TL in holotype (66.5-67.9% TL in paratypes) and disc length 56.0% (54.8-56.4%) TL. Disc widest at about one-half of its length, and thickest at anterior margin. Disc overlaps origin of pelvic fins, with prominent free posterior lobes broadly rounded. Disc fleshy, thick anteriorly, progressively thinning posteriorly. Preorbital snout length about one-seventh disc length, two times orbit diameter, and slightly greater than prenasal snout length. Eyes moderately small, protruding in specimens prior to preservation, orbit diameter about two times spiracle length. Eyes and spiracles close together, space between them about equal to distance between endolymphatic pores. Distance between orbits less than distance between spiracles. Spiracles smooth, moderately large and hemispherical, opening wider posteriorly. Pseudobranchial folds line anterior margin inside spiracles, 8-11 (12-14). Electric organs not clearly visible dorsally, but distinguishable in ventral view. Electric organs originate very close to anterior disc margin, anterior to eyes and nostrils, and terminate posteriorly, just past last gill openings. Electric organs kidney shaped, widest anteriorly between mouth and first gill slit. Length of electric organ about two times greatest width. Skin on dorsal and ventral surfaces entirely smooth.

First gill slit positioned at about one-third of disc length, last gill slit situated just anterior to two-thirds of disc length. Gill slits crescent shaped, originating approximately in line with pelvic fin origin. Distance between first gill slits greater than distance between fifth gill slits. Third gill slits largest, about equal to spiracle length. Nasal curtain subquadrangular, its width about three times its length. Nasal curtain extends posteriorly in a relatively straight line towards mouth. Posterior margin of nasal curtain with two confluent lobes, broadly rounded and angled medially, margin slightly fringed (more so on paratype CAS 223473). Outer margins of nostrils situated at level of mouth corners. Posterior contour of nostrils confluent with prominent median lobes that contact nasal curtain at corners and separate nostrils from mouth. Skin at corners of mouth loose, deeply furrowed. Mouth broadly arched with relatively large gape. Mouth width greater than internarial width. Teeth set in quincunx, flattened labial-lingually, morphologically similar in both upper and lower jaws, with well-developed single cusps.

Pelvic fins originate just anterior to insertion of disc. Pelvic fin length about one-fifth of total length and two-thirds of pelvic fin width. Anterior margins slightly concave, posterior margins more convex. Pelvics widest posteriorly, at about two-thirds of their length. Cloaca situated anterior to midlength of pelvic fins. Claspers dorsoventrally flattened, not reaching pelvic fin tips in both male holotype and paratype specimens.

Tail moderately short and stout, postdorsal tail length 24.8% (20.8-24.8%) TL as measured from second dorsal fin insertion, but tail length from cloaca is about 40% TL. Tail tapers appreciably from posterior tips of pelvic fins toward caudal fin. Tail width greater than height at pelvic tips, but more circular in cross-section at caudal fin origin. Lateral tail folds ridgelike and not very prominent. Lateral tail folds extend from level just anterior to second dorsal fin base to posterior ventral facet of caudal peduncle. Origin of lateral tail fold not as distinguishable as insertion. Lateral tail folds vary in proportional length between each side of tail on holotype and paratype specimens 13.7-14.5% (15.3-17.0%) TL.

First dorsal fin origin at level of widest pelvic fin width. Less than half of first dorsal fin base situated over pelvic fin bases, but posterior free lobe of first dorsal extends posterior to level of pelvic fin tips. First dorsal base length about two-thirds of its height. First dorsal fin broad, subtriangular with rounded corners. Anterior margin of first dorsal moderately slanted, with posterior free lobe about equal to twice the base length (less so in CAS 223473 female paratype). Posterior margin of first dorsal at or posterior to level of second dorsal fin origin. Second dorsal fin about two-thirds as large as first dorsal fin; second dorsal fin height 0.62 (0.66-0.70) in first dorsal fin height. Dorsal fins somewhat similar in shape, second dorsal fin with lower and more acute apex. Interdorsal space less than distance between second dorsal fin insertion and dorsal caudal origin. Caudal fin tall and triangular, overall height 20.4% (21.2-24.4 %) TL, and taller proportionally in male specimens than in female specimen. Upper lobe of caudal fin longer and more sloping than lower lobe. Posterior margin of caudal fin slightly concave just dorsal to mid-height. Apices of caudal fin slightly acute in male specimens to more broadly rounded in female specimen.

Tooth row counts in upper jaw 23 (20-22) and in lower jaw 27 (19-22). Radial counts for paratype (CAS 223472) 54 pectoral and 20 pelvic. Trunk vertebrae 27 (25-27), total tail vertebrae 69 (68-72), and tail terminal vertebrae 20 (20-24). Tail vertebrae to first dorsal fin origin 15 (14-19), to second dorsal origin 30 (29-34), and to upper caudal origin 49 (44-52). Spiral valve counts for paratypes 12-13.

Coloration. In fresh specimens, coloration uniform purplish brown dorsally, with darker hue around margins of disc and pelvic fins, and on caudal fin. In preservative, dorsal coloration uniform purple-gray fading to light brown, with darker hue around margins of disc and pelvic fins, and on caudal fin. Posterior margins of dorsal fins and area just surrounding orbits fading to faint light cream to white color. Ventral surface light cream, abruptly darker on posterior disc margin, pelvic fin margin, claspers, and edges of tail, progressively widening towards caudal peduncle. Lateral tail fold cream colored.

Etymology. The name formosa has two connotations. First, it is in reference to Ilha Formosa, the historical name of the type locality, Taiwan, and second, it means beautiful, referring to the purplish brown coloration of fresh specimens.

Distribution. Known from the east coast of Taiwan, from Keelung to Suao, at less than 300 m.

Size. Maximum-recorded sizes are at least 622 mm TL for an adult male and 366 mm TL for an immature female.

Comparisons. Torpedo formosa differs from T. tokionis in that the species does not have an emarginated caudal fin, has a disc that is wider than long, and has a relatively short tail. Disc width in T. formosa is 63.6-67.9% of total length, differing significantly from that of T. tokionis , in which disc width is 50.1-52.6% of total length. These proportions reflect a different disc shape between the species, with the disc shape being more ovate in T. formosa , while the disc is more circular in shape in T. tokionis (Fig. 4). In T. formosa , the distance from the posterior tip of the pelvic fin to the origin of the lower caudal fin lobe is less than three-quarters of the caudal fin height, and less than half the pelvic fin width. The tail is comparatively long in T. tokionis , where this distance is more than three-quarters of the caudal fin height, and much more than half the pelvic fin width. The number of turns in the spiral valve of T. formosa is slightly higher in the two paratypes (12-13) than in the three T. tokionis (9-10) examined. In addition, dorsal coloration of T. formosa specimens is light brown without any conspicuous markings, and disc thickness thins progressively posteriorly, while in T. tokionis , coloration is dark chocolate brown with dark hatch markings, and the disc remains thick throughout.

Comparison of T. formosa to syntypes of T. nobiliana reveal that the latter species has somewhat shorter snout, head, eye and spiracle lengths, dorsal fins that are more tongueshaped, relatively smaller caudal fins, and a higher vertebral count. Preorbital snout length was 7.7-8.7% of total length in T. formosa , and was 6.2-7.2% of total length in T. nobiliana . In T. formosa , the caudal fin height is greater than the distance from the first dorsal fin origin to caudal origin. Torpedo nobiliana by comparison has a shorter caudal fin height, whereby its height is less than the distance from the first dorsal fin origin to the caudal origin. In addition, the ventral caudal margin length was 16.9-18.6% of total length in T. formosa , longer than that found in T. nobiliana (15.0-15.7% of total length). The range in trunk vertebrae in T. formosa (25-27) was comparatively lower than was found for the syntypes of T. nobiliana (29-33).

The description of T. nobiliana by Bigelow and Schroeder (1953) was also utilized for comparison to T. formosa , due to the generally poor condition of the T. nobiliana syntypes. This comparison revealed differences in proportional mouth widths, interorbital widths, and distances between gill openings. In T. nobiliana as described by Bigelow and Schroeder (1953), mouth width is approximately 1.7 times as great as interorbital width. Mouth width is 1.6-1.7 times interorbital width in T. nobiliana syntypes, but in T. formosa , this distance is greater, at 2.0-2.4 times interorbital width. Also, in the description of T. nobiliana , the distance between the fifth gill slits is about 2.0-2.3 times as great as the mouth width. This is true of the T. nobiliana syntypes, but in T. formosa , this distance is 1.5-1.7 times as great as the mouth width. Lastly, the distance between the fifth gill slits is 82-92% of the distance between the first gill slits in T. nobiliana , but is only 76-78% in T. formosa .

The distribution of T. formosa appears to be somewhat restricted as it is currently known only from the northeast coast of Taiwan. To the best of our knowledge it has not been reported from Japanese waters, with T. tokionis being the only other Torpedo Tetronarce species known to occur in the western North Pacific. Records of T. Tetronarce species from south of Taiwan are limited. Compagno et al. (2005) mention an undescribed plain colored Torpedo from the Philippine Islands, without specifying the subspecies, while Compagno and Last (1999) mention an undescribed Torpedo species from northern Australia. A checklist of batoids (Huang, 2001) occurring in Taiwanese waters includes T. macneilli Whitley, 1932 , but without mention of any descriptive characters. Since T. macneilli is endemic to southern Australian waters (Last & Stevens, 1994) we consider this record to be dubious. Torpedo nobiliana , common in the western North Atlantic, eastern Atlantic, and Mediterranean Sea, has been reported from South Africa, but it does not extend further east than Algoa Bay (Compagno et al., 1989; Compagno, 1995). The South African species, however, may in fact be distinct from the true T. nobiliana (Carvalho et al., 2002; D.A. Ebert, unpubl. data) and from another possibly new species from the Mozambique Channel (L.J.V. Compagno, South Africa Museum, Cape Town, South Africa, pers. comm.). Therefore, given the absence of any other described species of T. Tetronarce species in the Indian Ocean it seems highly unlikely that T. nobiliana would occur in Taiwanese waters.