BULLETINOFMARINESCIENCE.60(1): 152-160. 1997 TWO TYPES OF PELAGIC LARVAE OF BEMBROPS (TRACHINOIDEA: PERCOPHIDAE), WITH NOTES ON THEIR PHYLOGENETIC IMPLICATION Muneo Okiyama ABSTRACT A larva and a pelagic juvenile of Bembrops curvalura are identified and described from Japanese waters. These pelagic larvae are remarkable in developing a transparent enlarged dermal space over the head, i.e., so-called "bubblemorph," which disappears by 15.8mm SL through metamorphosis. Pigmentation is scant, but a peritoneal pigment section over the gut is distinct. Occurrence of a similar larva of Bembrops in Australian waters probably referable to another species is also recorded, although its specific identification cannot be made. In contrast, the Atlantic congener, B. anatiroslris, is known to lack bubblemorph stage (Richards, 1990), revealing at least two types of pelagic larvae in the genus. Possible significances of this peculiar larva] morph are discussed. Known larvae of the Percophidae including Bem- brops, Chrionema, Spinapsaron. Hemerocoeles, and Matsubaraea are compared and based on ]arval morphology the monophy]y of the family is questioned. The Suborder Trachinoidea contains more than 200 species of (tropical) marine fishes placed in 13 families (Nelson, 1994). Although the monophyletic integrity of the group sensu Pietsch and Zabetian (1990) is doubtful (Johnson, 1993), the hypothesis that Trichonotidae, Creediidae and Percophidae form a monophyletic assemblage has gotten general support (Pietsch and Zabetian, 1990; Johnson, 1993). More than 10 years ago, the ontogeny and systematics of the Trachinoidea (excluding Pholidichthyidae and Ammodytidae) were reviewed by Watson et al. (1984), revealing the paucilty of early life history data on these taxa. At that time, only a single larva of Hemerocoetes sp. had been described (Crossland, 1982). Subsequently, Mori (1988) described a series of early developmental stages of Spinapsaron sp. in detail. Recently, an unusual pelagic bubblemorph larva from Japanese waters was identified as Bembrops. A comparison of the morphology of this larva with that of the Atlantic congener, B. anatirostris, (Richards, 1990), led me to further investigate the current knowledge of early life history stages of the Percophidae including examination of specimens not described in the literature, The revision of Bembrops (Das and Nelson, 1996) provided reliable information on the systematic status of each species in this complex genus. In this paper, emphasis is placed on the phylogenetic significance of the larval bubblemorph of Bembrops and the generic interrelationships of the family Per- cophidae based on ontogeny. MATERIALS AND METHODS Materials for this study came from various sources. Two pelagic individuals, a larva and a juvenile of Bembrops curvalura were collected from the Sagami Bay, Centra] Japan, during the cruises of the R/V TANSEIMARU(KT88-2; 10.3 mm SL; II Dec. 1988) and the R/V HAKUHOMARU(KH89-1; 15.8 mm SL; 11 Sept. 1989). These collections were made using 3.3-m-IKPT towed obliquely from the surface to less than 100 m. These specimens are held in the Ocean Research Institute (ORI). Additional materials were borrowed from other institutions or sorted from my collections, as fol- lows: Bemhrops sp.: CSIRO uncatalogued; 10.0 mm SL; 13 Oct. 1983; ]9°15'S, 116°10'E; 2-m-IKMT, oblique tow, 0-100 m. Chrionema cf. pallidum: NMFS-Honolulu T8-1-16; 16.3 mm SL; 24-25 Jan. 1977; 14°00'S, 150000'W; 3-m-IKMT, oblique tow, 0-275 m; Identified by Dr. B. C. Mundy; to be held in the Los Angeles County Museum. Malsubaraea fusiforme: ORI uncatalogued, 8.6 mm SL (cleared and stained); 17 Sept. 1979; Fukui harbor, the Sea of Japan; Maruchi larva net, horizontal 152 OKIYAMA: TWO TYPES OF LARVAL Bt.MBROPS 153 tow, 5-m depth. Spinapsaron sp.: ORI uncatalogued, 12.2 mm SL (cleared and stained); 13 June 1969; Sado strait. the Sea of Japan; Triangle larva net, horizontal tow, 25-m depth. Larvae were measured under a stereo microscope using an ocular micrometer according to the meth- od of Okiyama (1988). Drawings were prepared with the aid of camera lucida. Larval and juvenile specimens of Bembrops curvatura were cleared and stained for osteological study following Dingerkus and Uhler (1977). RESULTS Bembrops curvatura Okada et Suzuki Figure 1 Identification.-Despite its unusual bubblemorph appearance, the 1O.3-mmlarva can readily be referred to Bembrops, in having meristic characters and the external as well as internal pigmentation patterns similar to those of the metamorphosed pelagic juvenile, which resembles the pelagic larvae of Bembrops anatirostris reported by Richards (1990), and it bears the small incipient skin flap at the posterior end of the maxilla diagnostic for Bembrops. Recently, 13 species of Bembrops were recognized as valid(Das and Nelson, 1996), three of which are recorded from the Japanese waters. Their meristic characters are shown in Table 1, together with those of the unnamed Japanese species (Okamura, 1985) which was not mentioned in Das and Nelson (1996). Both the larval and juvenile pelagic specimens described herein can be ascribed either to Bembrops curvatura or to B. caudimacula from the meristics (Table 1). However, the] 5.8-mm juvenile exhibits "the lateral line descending abruptly over pectoral fin" which is diagnostic for B. curvatura (Das and Nelson, 1996). The number of lateral line scales (about 46) and rows of scales between lateral line and origin of anal fin (3) also fall within the ranges of B. curvatura. Description.-] 0.3 MM LARVA(FIG. 1 A-C). Measurements in percentage of SL and meristic data: Head length 47.5, head width 43.7, head depth 33.0, snout ]6.5, maxillary 18.2, eye diameter ]5.0 X 12.1, preanus 63.1; D VI-14, A 14, PI 23/23, P2 6, C 7+7+7+3, Vertebrae 28. GENERALMORPHOLOGY.Body stubby, with exceptionally massive and bulbous head created by envelope of flaccid skin. Head long, but deep and wide. Head oval in dorsal view with large eyes located latero-ventrally at widest part. Anlage of brain and arrangement of oculomortor muscles clearly visible through thick but transparent envelope. Transparent gelatinous layer deep, lacking any visible structures except widely spaced strands running vertically between surface and base of skull. Strands usually branched just above skull and spread towards sur- face of skin. Ovoidal eyes (long/short axis = 1.25) located at middle of head with long axis dorsally titled to horizontal plane. Nostrils small, single, deep cups formed near tip of long snout close to maxillae. Mouth large and inferior in position due to bulged forehead. Maxillae reach posteriorly to vertical through anterior part of eye. Membranous flap absent on posterior end of maxillae. Premaxillae edentulous with complicated articulation anteriorly with maxillae, but anterior spinous pro- jection not present. Dentary teeth also lacking. No spinous elements on head. In contrast to head, trunk and tail laterally compressed. Abdomen distended ventrally within framework of bubblemorph. Tail decreases in depth toward caudal fin which again deepens near base. Full compliment of rays present in all fins, although first dorsal fin still small and separated widely from second. Dorsal- and anal-fin rays similarly long and 154 BULLETIN OF MARINE SCIENCE. VOL. 60. NO. I, 1997 Figure 1. Pelagic larva (bubblemorph) and juvenile of Bembrops curvatura, collected from Sagami Bay, central Japan. A-C, Left lateral, dorsal and ventral views of larva, 10.3 mm SL; D-F, the same of juvenile, 15.8 mm SL. Internal pigment on gut omitted in dorsal view. OKiYAMA: TWO TYPES OF LARVAL BEMBROPS 155 Table 1. Selected meritistic characters for four species of Bembrops recorded from Japanese waters (Okamura, 1985; Nakabo, 1993, Das and Nelson, 1996) Species 2nd dorsal fin Anal fin Pectoral fin Lateral 1. scales B. caudimacula 13-15 14-17 19-25 42-54 B. curvatura 14-15 15 19-25 40-49 B. filifer 14-16 16-18 22-25 60-69 B. sp.* 15 17 22-28 65-67 Pelagic specimens 14 14-15 23-24 ca. 46 • Okamura (1985). segmented. Pelvic fins in jugular position and broadly separated at base. Pelvic rays shorter than those of pectoral fin. Pectoral fins have broad base and blade with rays directed posterodorsally. Pigmentation: Aside from black eyes, pigmen- tation light, particularly on head, where small dots visible only on opercular flaps, on hind brain and halfway along ventral edge of dentaries. On the trunk, dots of various sizes on pectoral fin blade and around pelvic fin base posterior to cleithral symphysis. On caudal peduncle, pigments concentrated on dorsal and ventral mar- gins and midlaterally near caudal-fin base. Most conspicuous of these occurs along each side of ventral midline. In addition, series of internal melanophores present along most of dorsal border of vertebrae. Fin pigmentation restricted to pelvic fins, which bear dots on proximal halves of membranes between 1st to 4th rays laterally. Single large peritoneal patch of pigment covers nearly half of dorsal surface of gut excluding rectum. 15.8 MMPELAGICJUVENILE(FIG.1 D-F). Measurements in % of SL and meristic data: Head length 47.5, head width 34.2, head depth 19.0, snout 11.7, eye diameter 13.6, preanus 60.8; D VI-14, A 15, PI 24/24, P2 6, C 4+7+7+4, L.L.S. ca 46, Vertebrae 28. GENERALMORPHOLOGY.Larval bubblemorph completely transformed into ju- venile form with extremely depressed and long head. Relative size of head un- changed in length, but decreased in width due to loss of bubblemorph. Dorsal profile of forehead straight, forming pointed long snout. Eyes similarly large, produced laterally, and oval in shape with longer axis in parallel with horizontal plane. Top of skull remained transparent as in previous larva. Nostrils incom- pletely separate into two narrow openings.