Parateleopus indicus ( Alcock 1891 )

Kaga, Tatsuya, Iwamoto, Tomio & Mishra, Subhrendu Sekhar, 2022, Redescription of Ateleopus indicus Alcock 1891, (Teleostei: Ateleopodiformes Ateleopodidae), and its reassignment to the genus Parateleopus, Zootaxa 5092 (2), pp. 176-190 : 183-187

Parateleopus indicus ( Alcock 1891)

[English name: Smallmouth Jellynose]

( Figs. 1A , 2A , 3A , 4B , 5A , 6 , and 9; Tables 1–2 )

Ateleopus indicus Alcock 1891: 123 (ZSI 13069, 260 mm SL, type locality: Andaman Sea, lat. 11°31′40″N., long. 92°46′40″E.); Alcock 1892: plate II (ZSI 13069, 260 mm SL, Andaman Sea, illustration); Alcock 1899: 123 (ZSI 13069, 260 mm SL, Andaman Sea; ZSI 141/1, 456–458/1, 460/1, 232.5– 343 mm SL, Arabian Sea, off Travancore coast, description); Howell Rivero 1935: 96 (specimen in BMNH, 305 mm TL, Andaman Sea; USNM 98816, 138 mm TL, Philippine Islands: between Gailolo & Kayoa Islands, “Albatross” St. D5626, description); Norman 1939: 32 (BMNH 1939.5.24.574–576, 3, 260– 370 mm TL, Maldive area; BMNH 1900.1.20.2, 270 mm TL, Arabian Sea, description); Stauche & Blache 1964: 50 (key); Talwar 1977 (ZSI 13069, Andaman Sea, type catalog); Adam et al. 1998: 9 (1939.5.24.574–576, 285– 385 mm SL, Maldive area, checklist); Manilo & Bogorodski 2003: S79 (Arabian Sea, checklist).

Holotype. ZSI 13069 (260 mm SL; Fig. 11), Andaman Sea, 188 to 220 fathoms .

Other materials examined. 12 specimens (122.3–350 mm SL): BMNH 1900.1 .20.2, 250 mm SL, Laccadive Sea, India, 224–284 fathoms; BMNH 1939.5.24.574–576, 3 specimens, 260–350 mm SL, Western Indian Ocean , Maldive area, Maldives Maldive ; SAIAB 14049, 192 mm SL, Indian Ocean, Kenya, off Mombasa, 03°49′00″S, 040°00′00″E ; SAIAB 14109, 164.5 mm SL, Indian Ocean, Kenya, off Malindi, 03°11′00″S, 040°38′00″E ; USNM 98816, 122.3 mm SL, Indonesia, Moluccas ; ZSI F141 / 1, 232.5 mm SL, Andaman Sea , 405 fathoms ; ZSI F456– 457 /1, F460/1, 3 specimens, 291–343 mm SL, Laccadive Sea , 224–284 fathoms ; ZSI F2380 /1 (dried specimen), off North Andaman Island , 235 fathoms .

Diagnosis. As for genus. In addition, 8–10 dorsal-fin rays distinguish the species from its congener.

Description. Counts and measurements of Parateleopus indicus are given in Table 2 . Data of other materials are shown in parenthesis when variation is recognized between holotype and other materials.

Body elongate, compressed; tail moderately long, length 1.6 (1.4–1.7) in SL, tapering to caudal fin, completely enveloped in soft gelatinous tissue, without scales on surface. Head large, length 5.6 (5.1–6.3) in SL, slightly compressed, covered with thick gelatinous tissue forming gelatinous snout. Anterior nostril with a short tube; posterior nostril large, without a tube, situated just in front of upper half of eye. Eye small, its diameter approximately equal to or slightly larger than pectoral-fin base. Interorbital space wide, with a deep longitudinal groove below the gelatinous skin. A flat vertically oblong crescent-shaped protrusion of sphenotic bone from behind eye to posteroinferior region of orbit. Mouth very small, subterminal, protractile, gape very narrow, width of gape slightly larger than eye diameter, posterior end of gape extending to a little anterior of anterior nostril, also an eye diameter anterior from anterior margin of eye. Maxillary buried posteriorly under thick gelatinous tissue and extending to anterior edge of orbit. Lower jaw short, length 2.8 (2.3–3.1) in HL. Posterior end of lower jaw situated vertical of pupil. Both lips thick with wrinkles and tiny papillae.

Upper jaw with five to seven rows of villiform teeth in adults (three or four rows in specimen 232 mm SL and two or three rows in specimen 122 mm SL); lower jaw toothless.

Palatine, vomer, and tongue toothless. Symphysis of lower jaws slightly convex dorsally in front. Preopercular margin not free; gill opening wide; posterior end of opercle usually acute and pointing slightly upward. Both gill membranes united ventrally and attached to isthmus by soft tissue. Gill rakers on upper part of lower limb of first gill arch a little flattened, lower ones stumpy: rakers on other gill arches all stumpy. All tips of gill rakers bluntly pointed and weakly spinulose. No pseudobranchiae. Branchiostegal rays seven. Dorsal-fin origin at same vertical or slightly behind that of pectoral-fin base. Dorsal-fin base short, less than snout length. Dorsal fin long, its length approximately equal to pectoral-fin length. Pectoral-fin base short, almost equal to eye diameter. Pectoral fin long, its length approximately equal to length from posterior margin of eye to dorsal-fin origin, the tip reaching just anterior to anus (reaching anus in two specimens, 250 and 291 mm SL). Pelvic fin jugular, relatively short, the tip slightly tapered and extending to point anywhere between base of pectoral and anterior half of pectoral fin (both tips of pelvic fin broken in holotype). Pelvic fin appearing like one short stiffened ray, but anterior two rays rudimentary, attached to front base of this short ray in specimens to about 323 mm SL; some vestigial rays in cutaneous membrane on medial side of base (posterior two rays still separated in a specimen 122 mm SL). (Anterior two rudimentary rays becoming very small and undetectable in large specimens, 343–350 mm SL). The short stiffened ray somewhat curved with many fine segments. Precise count of pelvic-fin rays difficult because of posterior several rays in cutaneous membrane and rudimentary anterior rays. Anal-fin base long, continuous with caudal fin. Anus just in front of anal-fin origin.

Color in preserved specimens. Head and body brownish, blackish, or grayish. Lips light brownish or whitish. Oral and gill cavities light brownish or whitish. Eye dark purplish. All fins blackish, brownish or grayish except whitish or light brownish of pelvic fin. Anal-fin base brownish or translucent; pterygiophores visible.

Distribution. Known from Indonesia ( Moluccas) and the Indian Ocean, including the Andaman Sea, Laccadive Sea, and Arabian Sea: Maldives, and now from off Kenya, the western Indian Ocean. Depth range from 188 to 405 fathoms (343 to 740 m).

Remarks. Howell Rivero (1935: 96) recorded the distribution of Ateleopus indicus as: “ Philippine Islands, between Gailolo & Kayoa Islands, Albatross St. no. D5626, Nov. 1909. USNM No. 98816.” However, based on our research, the eastern end of the distribution is the Moluccas, Indonesia, based on that specimen. Howell Rivero (1935) probably assumed that the Moluccas were in the Philippines because the specimen was captured during the Albatross Philippines Expedition of 1907–1910. Norman (1939) also incorrectly ascribed that specimen as from the Philippine Islands. The capture location between Gillolo and Kayoa Islands is in the Moluccas, Indonesia. There are no records, so far as we know, of captures within the Philippine Islands. On the other hand, although the westernmost capture of A. indicus was formerly the Maldives in the Arabian Sea ( Norman 1939; Adam et al. 1998; Manilo & Bogorodski 2003), specimens SAIAB 14049 and 14109 represent the first record of Parateleopus indicus from Kenya and the westernmost record of the species.

Kaga et al. (2015: Fig. 3 ) reported that the five pelvic-fin rays of postlarva A. japonicus (258 mm SL) were still separated. In a juvenile of 251 mm, the anterior two rays of the fin had become rudimentary and attached to the third ray, and the posterior two rays had become covered with cutaneous membrane. In a 122.3 mm specimen of P. indicus , however, the anterior two rays had already become rudimentary and attached to the third ray, although the posterior two rays were still separated. The metamorphosis from postlarva to juvenile in P. indicus thus appears to begin at a smaller size than in A. japonicus . A specimen of P. indicus of 322.5 mm SL has ripe ovaries ( Fig. 4B ). Alcock (1899) described them as “a pair of thin-walled sacks loosely filled with largish eggs (over 1 millim. in diameter in spirit) and opening by a common orifice behind the vent”. We have observed ripe ovaries in specimens of A. japonicus greater than about 600 mm SL. The largest specimen of P. indicus we examined is 350 mm SL. Ateleopus attains more than 800 mm SL ( Kaga et al. 2015), P. microstomus attains at least 350 mm TL ( Radcliffe 1912), based on the one known specimen. Ijimaia attains a large size of about 2 m TL ( Howell Rivero 1935). Guentherus attains more than 680 mm SL ( Barnard 1948). P. indicus may be the one of smallest species of ateleopodid.

The gelatinous snout of the holotype of P. indicus is pointed ( Figs. 1A and 9 ) but we consider that shape to be an incidental condition resulting from its preservation. Other specimens of P. indicus had a variety of shapes of the gelatinous snout ( Figs. 4B and 5A ).

Figures

FIGURE 1. Head of ateleopodids.A. Parateleopus indicus (Holotype of Ateleopus indicus), ZSI 13069, 260 mm SL; B. Ijimaia loppei, NSMT-P101176, 584 mm SL.

FIGURE 2. Ventral aspect of branchiostegal membranes and isthmus. A. Parateleopus indicus, one of ZSI 456, ZSI 457, ZSI 460, 291 mm SL; B. Ijimaia dofleini OMNH-P 46032, 354 mm SL; C. Guentherus altivela, MNHN 1988-0392, 184 mm SL.

FIGURE 3. Protrusion of sphenotic. A. Parateleopus indicus BMNH 1900.1.20.2, 250 mm SL; B. Ijimaia dofleini OMNH-P 46032, 354 mm SL.

FIGURE 4. Pelvic fin of Ateleopodiformes. A. Guentherus katoi, KPM-NI 016647 (holotype), 605 mm SL; B. Parateleopus indicus, one of ZSI F456/1, F457/1, F460/1, 322.5 mm SL; C. Ijimaia antillarum, USNM392171, 685 mm SL; D. Ateleopus japonicus, BMNH 1984.1.1.52, 430 mm SL.

FIGURE 5. Lateral view of four genera of ateleopodids. A. The genus Parateleopus, P. indicus, one of BMNH 1939.5.24.574– 576, 350 mm SL; B. The genus Ateleopus, A. japonicus, OMNH-P 10127, 395 mm SL; C. The genus Ijimaia, I. dofleini, BSKU 44320, 533 mm SL; D. The genus Guentherus, G. katoi, KPM-NI 016647 (holotype), 605 mm SL.

FIGURE 6. Pelvic girdle of Parateleopus indicus. One of ZSI F456–457, 460, 291 mm SL.

FIGURE 9. Parateleopus indicus (Alcock 1891). ZSI 13069, holotype of “Ateleopus indicus”, 260 mm SL.