Species Diversity 19: 9–14 New species of Acropoma 9 25 May 2014 DOI: 10.12782/sd.19.1.009

Acropoma profundum, a New Species of Lanternbelly (Teleostei: Perciformes: Acropomatidae) from the Solomon Islands

Makoto Okamoto Seikai National Fisheries Research Institute, 1551-8 Taira-machi, Nagasaki 851-2213, Japan E-mail: [email protected] (Received 7 January 2014; Accepted 10 March 2014)

A new species of acropomatid fish, Acropoma profundum, is described based on a single specimen, 40.1 mm in stan- dard length, from the Solomon Islands (depth 1169–1203 m). It is distinguished from congeneric species by its unique long, U-shaped luminous gland, which extends from the throat to just in front of the anal-fin origin. The new species is fur- ther distinguished from its congeners by the following combination of characters: anus situated nearer to the pelvic-fin base origin than to that of the anal fin, proximal radial of first anal-fin pterygiophore with a trough-like recess, body depth 29.1% SL, and pectoral-fin rays 15.Acropoma profundum is the deepest-living species of its genus, and the smallest in size at sexual maturity. Key Words: Taxonomy, Acropoma, luminous organ, South Pacific Ocean.

radial of the first anal-fin pterygiophore, and the anus situ- Introduction ated nearer to the pelvic-fin base origin than to that of the anal fin. However, it differs significantly from specimens of Acropomatids are a percoid family of medium size (most these two species in the length of the luminous gland. The around 20 cm, some reaching 40 cm in standard length) specimen is therefore described herein as the type of new comprising seven genera and ca. 30 species generally found species. in depths of greater than several hundred meters in the tem- perate Atlantic, Pacific, and Indian Oceans. Species have a single or two dorsal fins with 9–10 spines, a pelvic fin with Materials and Methods one spine and five soft rays, an anal fin with two or three spines, seven branchiostegal rays, and 24–25 total vertebrae. Meristic and morphometric methods follow Hubbs and The genus Acropoma Temminck and Schlegel, 1843 can Lagler (1958) and Okamoto and Ida (2002). Lower-jaw be distinguished from other genera of the family in hav- length was measured from the anteriormost point of the ing a ventral luminous organ (Matsubara 1953; Yamanoue dentary to the posteriomost point of the retroarticular. Lu- and Toda 2008). It currently includes five valid species: minous gland length was measured from the anterior tip of A. argentistigma Okamoto and Ida, 2002, A. boholensis the luminous gland to the posterior end of the gland on the Yamano­ue and Matsuura, 2002, A. hanedai Matsubara, left side. Missing lateral-line scales were estimated by count- 1953, A. japonicum Günther, 1859, and A. lecorneti Four- ing scale pockets. All measurements were made by calipers manoir, 1988. The luminous organ comprises a luminous to the nearest 0.1 mm. Counts of supraneurals and verte- gland, lens, and reflector, and the shape of the luminous brae were taken from radiographs. The formula for the con- gland is an important diagnostic character for the species figuration of the supraneural bones, anterior neural spines, (Haneda 1950; Haneda and Johnson 1962; Okamoto and Ida and anterior dorsal fin pterygiophores follows Ahlstrom et 2002). In general, the luminous gland is flat and embedded al. (1976). The condition of the luminous gland and the sex in the muscles of the ventral region, and it cannot be seen of the specimen were established by dissection of the abdo- from the outside (see Haneda 1950). men on the right side. Standard length is abbreviated as SL. While studying material of the genus from various South The institutional abbreviations of the comparative mate- Pacific localities, a single specimen from the Solomon rial examined in the present study are as follow: Australian Islands in the research collection of the Muséum National Museum, Sydney, Australia (AMS); Laboratory of Marine d’Histoire Naturelle, Paris (MNHN) was found to have char- Biology, Faculty of Science, Kochi University, Kochi, Japan acters that differ from those of previously described spe- (BSKU); School of Marine Biosciences, Kitasato University, cies. The specimen is similar to two of the above-mentioned Ofunato, Japan (FSKU); Fisheries Research Laboratory, Mie species, A. argentistigma and A. japonicum, in having a U- University, Shima, Japan (FRLM); Kagoshima University shaped luminous gland, a trough-like recess in the proximal Museum, Kagoshima, Japan (KAUM); Muséum National

© 2014 The Japanese Society of Systematic Zoology 10 M. Okamoto d’Histoire Naturelle, Paris, France (MNHN); National Mu- margin of interopercle weakly serrated. Subopercle thin, seum of Nature and Science, Tsukuba, Japan (NSMT); Sei- anteroventral margin weakly serrated, posteriorly extended kai National Fisheries Research Institute, Nagasaki, Japan to form thin flap. Lower end of gill opening extending to (SNFR); and Yokosuka City Museum, Yokosuka, Japan vertical drawn through anterior margin of eye. Anus nearer (YCM). to pelvic-fin base origin than to origin of anal fin (Fig. 3A). Scales weakly ctenoid, thin, extremely deciduous. Body and Acropoma profundum sp. nov. head covered with scales. Two separated dorsal fins, eighth [New English name: Solomon’s Lanternbelly] spine of dorsal fin lacking any connection with fin mem- (Figs 1, 2A, 3A) brane (cf. eighth isolated dorsal-fin spine of Okamoto and Ida 2002); first dorsal fin originating slightly posterior to Holotype. MNHN 2002-3878, 40.1 mm SL, female, vertical drawn through pectoral fin base, spines weak. Pec- 09°00′00″S, 159°49′10″E, Solomon Islands, western South toral and pelvic fins slender. Anal fin originating slightly Pacific, 1169–1203 m depth, 26 September 2001. anterior to vertical drawn through middle of second dorsal Diagnosis. A species of Acropoma distinguished from fin base; anal fin spines moderately developed, first spine its congeners by its long, U-shaped luminous gland, which extremely small, third spine longest; proximal radial of first extends from the throat to just in front of the anal-fin origin. pterygiophore with trough-like recess. Caudal fin forked. Description. Dorsal-fin rays VII–I–I, 10. Anal-fin rays Supraneural bones 3 (0/0/0+​2/1+​1/1/1). Luminous gland III, 7. Pectoral-fin rays 15. Pelvic-fin rays I, 5. Caudal fin: long and U-shaped, extending from throat to just in front of upper and lower procurrent caudal-fin rays 11+​10; princi- anal fin base (Fig. 2A). pal caudal-fin rays 9+8.​ Vertebrae 10+​15. Gill rakers 5 (in- Measurements of holotype, as percentage of SL: head cluding 1 rudiment)+12 on first gill arch of right side; 5 (in- length 34.8; head width 15.3; head height 22.6; body depth cluding 1 rudiment)+13 (including 1 rudiment) on first gill 29.1; body width 14.0; caudal-peduncle depth 12.7; caudal- arch of left side, total 17–18. Lateral line scales ca. 44; scales peduncle length 23.1; orbital diameter 12.5; interorbital above lateral line 3; scales below lateral line 8. width 8.3; postorbital length 13.0; upper-jaw length 16.1; Body moderately elongate, compressed, dorsum slightly lower-jaw length 19.2; snout length 9.9; pre-1st-dorsal-fin elevated, ventral profile less arched, caudal peduncle mod- length 40.8; pre-2nd-dorsal-fin length 63.6; pre-pectoral- erately deep. Head large, slightly compressed. Mouth large, fin length 37.4; pre-pelvic-fin length 39.7; pre-anus length gape oblique; posterior margin of maxilla reaching to below 50.1; pre-anal-fin length 68.6; 1st anal-fin spine length 1.6; anterior margin of pupil; lower jaw projecting when mouth 2nd anal-fin spine length 4.7; 3rd anal-fin spine length 8.3; closed. Single row of villiform teeth on vomer and palatines. pelvic-fin spine length 10.9; 1st dorsal-fin base length 16.6; Teeth on both jaws small conical; one or two rows anteri- 2nd dorsal-fin base length 16.6; anal-fin base length 12.5; lu- orly on upper jaw; single row on lower jaw. Pair of inwardly minous gland length 41.0; (length of dorsal-fin spines, pec- directed canine teeth near symphyseal region of both jaws. toral-fin length, and pelvic-fin length not measured owing Tongue toothless, rounded, and broad at tip. Snout short to broken tips). and rounded, its length subequal to interorbital width. Eye Color in alcohol (Fig. 1). Body and head light brown large, round, orbital diameter subequal to postorbital length; except for dark brown opercle; bases of anal and pelvic fins bony rim of orbit raised above upper profile of head. Two black; caudal and pectoral fins and posterior half of pelvic closely positioned nostrils, both elliptical, anterior nostril fin translucent with creamy-white tinge; minute melano- with thin dermal flap. Interorbital space slightly elevated, phores scattered on dorsal and anal fins, base of caudal fin, medially flattened. Preopercle margin smooth. Posterior and anterior half of pelvic fin; various sizes of melanophores margin of opercle with two weak spines. Posteroventral scattered on ventral surface of body; anus pale.

Fig. 1. Acropoma profundum sp. nov., holotype, MNHN 2002-3878, 40.1 mm SL, Solomon Islands. New species of Acropoma 11

Fig. 2. Schematic diagram of the luminous glands of all six known species of Acropoma. A, Acropoma profundum sp. nov.; B, A. argen- tistigma; C, A. boholensis (after Yamanoue and Matsuura 2002); D,A. hanedai; E, A. japonicum; F, A. lecorneti (after Yamanoue and Toda 2008). 12 M. Okamoto

Distribution. Currently known only from the Solomon including A. profundum, is located nearer to the pelvic-fin Islands, western South Pacific, at a depth of 1169–1203 m. origin than to that of the anal fin (Figs 2A–C, E, F). In ad- Etymology. The specific name is a Latin adjective, dition to the above-mentioned features, A. profundum also “profundus” (meaning “deep”), referring to the depth where differs from A. boholensis in the count of pectoral-fin rays this species was collected, deeper than all its congeners. (15 vs 16 in A. boholensis), and from A. lecorneti in body Comparisons. Acropoma profundum is similar to proportions (body depth 29.1% SL vs 25% SL in A. lecor- two previously described species, A. argentistigma and A. neti). japonicum, particularly in having a U-shaped luminous Remarks. Although a large number of specimens of gland, a trough-like recess in the proximal radial of the first Acropoma were examined in museums worldwide, no ad- anal-fin pterygiophore, and its anus situated nearer to the ditional specimens of the new species were found. The ho- pelvic-fin base origin than to that of the anal fin (Fig. 3A). lotype of A. profundum is a 40.1 mm SL mature female. Al- It differs from them in the length of the luminous gland, the though the holotype is small, important diagnostic charac- posterior ends of which extend almost to the anal-fin origin ters of the genus (the shape of the luminous gland, form of in A. profundum (Fig. 2A) but only just reach past the anus the proximal radial of the first anal-fin pterygiophore, and in A. argentistigma and A. japonicum (Fig. 2B, E). In addi- the position of the anus) do not change with growth, as is tion to morphological differences, the smallest size at sexual evident from examination of specimens of various sizes of maturity is about 70 mm in total length in A. japonicum (ca. congeners (A. argentistigma, 59.0–107.5 mm SL; A. hanedai, 55 mm SL; Okuda et al. 2005; Yamada et al. 2007), whereas 41.9–193.0 mm SL; A. japonicum, 24.7–143.7 mm SL). Nor the holotype of A. profundum (smaller at 40.1 mm SL) is al- is there any geographical variation or sexual dimorphism in ready a mature female with a great number of mature eggs. these features. Their expression in A. profundum thus serves Acropoma profundum can be distinguished from the well to distinguish the new species from its congeners. other known congeneric species, A. boholensis, A. hanedai, The holotype of A. profundum has mature ovaries full of and A. lecorneti, in having a U-shaped luminous gland (vs relatively large eggs at several stages of development (the an elongate luminous gland with the anterior ends not con- most fully developed eggs are ca. 0.4 mm in diameter). Ex- tiguous in A. boholensis and A. hanedai, and an O-shaped cept for A. lecorneti, the other congeneric species mature luminous gland in A. lecorneti; Figs 2C, D, F). In addition, at ca. 55–100 mm SL, and do not reach more than 200 mm the proximal radial of the first anal-fin pterygiophore ofA. SL (Okamoto and Ida 2002; Yamanoue and Matsuura 2002; profundum differs from that of these three species in having Okuda et al. 2005; Yamada et al. 2007). Acropoma lecorneti a trough-like recess (vs lacking a trough-like recess or being is the largest species in the genus, described by Fourman- hollow in A. boholensis and A. lecorneti, and being hollow in oir (1988) and Yamanoue and Toda (2008) from the holo- A. hanedai; Yamanoue and Matsuura 2002; Yamanoue and type and an additional specimen measuring 326 mm SL and Toda 2008). The location of the anus of A. hanedai, midway 221 mm SL, respectively. Although they did not describe the between the origins of the pelvic and anal fins, is unique state of the gonads of A. lecorneti, the specimens surely are within the genus (Figs 2D, 3B). The anus of all its congeners, adults. Thus, A. profundum seems to attain sexual maturity at the smallest size among the species within the genus. Acropoma profundum is the deepest-living species of the genus, the holotype having been captured at a depth of 1169–1203 m. Acropoma japonicum and A. hanedai have been collected on the continental shelf and continental slope at depths of 50 to 400 m in the Indo-Pacific by bottom trawl (Brüss and Ben-Tuvia 1983; Yamakawa 1985; Mohsin and Ambak 1996; Randall and Lim 2000; Shinohara et al. 2005; Yamada et al. 2007; Javadzadeh et al. 2012). The holotype of A. lecorneti was collected at a depth of 360 m off the west coast of New Caledonia (Fourmanoir 1988). Although the depths at which A. argentistigma and A. boholensis occur are currently unknown, the two species have been collected by trawl and landed in fish markets of Southeast Asia and India (Okamoto and Ida 2002; Yamanoue and Matsuura 2002; Yennawar et al. 2012), which suggests that they are found on the continental shelf and in nearby waters.

Key to the species of Acropoma

Fig. 3. Ventral view of the abdomens of two species of Acro- poma. A, Acropoma profundum sp. nov., holotype, MNHN 2002- 1a. Luminous gland O-shaped (off New Caledonia and 3878, 40.1 mm SL; B, A. hanedai, FRLM 32251, 61.2 mm SL, Oki­nawa, Japan; Fig. 2F)...... A. lecorneti Taiwan. Arrows point to the anus. 1b. Luminous gland U-shaped or elongated (Fig. 2A–E).... 2 New species of Acropoma 13

2a. Luminous gland U-shaped (Fig. 2A, B, E)...... 3 105, 2 specimens, 90.2–102.2 mm SL, Mimase, Kochi, Japan, 2b. Luminous gland elongated with anterior ends on isth- November 1934; YCM-P 2162, 4 specimens, 53.3–77.3 mm mus and not connected (Fig. 2C, D)...... 5 SL, locality and collection data unknown. 3a. Posterior ends of luminous gland extending far beyond anus, nearly to anal-fin origin (Solomon Islands; Fig. 2A)...... A. profundum sp. nov. Acknowledgments 3b. Posterior ends of luminous gland extending slightly be- yond anus, but distant from anal-fin origin (Fig. 2B, E) I am very grateful to J. K. Dooley (Adelphi University) ...... 4 and D. W. Greenfield (California Academy of Sciences) for 4a. Front edge of luminous gland just reaching level of ori- their critical reading of the manuscript, and M. Iida (Uni- gin of pelvic fins (Andaman Sea and Bay of Bengal; Fig. versity of the Ryukyus) for her assistance. I also thank M. 2B)...... A. argentistigma McGrouther and S. Reader (AMS), K. Sasaki and H. Endo 4b. Front edge of luminous gland located well in front of (BSKU), T. Asahida (FSKU), S. Kimura (FRLM), H. Moto- origin of pelvic fins (Indo-Pacific; Fig. 2E) mura, H. Iwatsubo, and H. Hata (KAUM), P. Pruvost and R...... A. japonicum Causse (MNHN), K. Matsuura and G. Shinohara (NSMT), 5a. Anus pale and located nearer to origin of pelvic fin K. Hoshino (SNFR), and M. Hayashi (YCM) for specimen than to anal fin origin; proximal radial of first anal-fin loans and for providing opportunities to examine speci- pterygiophore not hollow (Bohol Sea; Fig. 2C)...... A. mens. boholensis 5b. Anus black and located halfway between origins of pelvic fin and anal fin (Fig. 3B); proximal radial of first References anal-fin pterygiophore hollow (southern Japan and South China Sea; Fig. 2D)...... A. hanedai Ahlstrom, E. H., Butler, J. L. and Sumida, B. Y. 1976. Pelagic stroma- teoid fishes (Pisces, Perciformes) of the eastern Pacific: kinds, distributions, and early life histories and observations on five of these from the North-west Atlantic. Bulletin of Marine Science 26: Comparative material. Acropoma argentistigma: FSKU- 285–402. P 4106, paratype, 59.0 mm SL, fish market in Phuket Island, Brüss, R. and Ben-Tuvia, A. 1983. Tiefenwasser- und Tiefseefische aus Thailand, Andaman Sea, 15 November 1998; KAUM-I. dem Roten Meer. VIII. Über das Vorkommen von Acropoma ja- 23072–23074, 23078–23079, 5 specimens, 82.1–91.0 mm SL, ponicum Günther 1859. Senckenbergiana Maritima 15: 27–37. fish market in Mahachai, off Phuket Island, Thailand, An- Fourmanoir, P. 1988. Acropoma lecorneti, une nouvelle espèce de daman Sea, 6 September 2009; NSMT-P 58731, holotype, Nouvelle-Calédonie (Pisces, Perciformes, Acropomatidae). Cy- 107.5 mm SL, fish market in Phuket Island, Thailand, -An bium 12: 259–263. daman Sea, 15 November 1998. 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