Pigmentation, Squamation and the Osteological Development of Larval

BULLETIN OF MARINE SCIENCE, 56(3): 826-848, 1995 CORAL REEF PAPER

PIGMENTATION, SQUAMATlON AND THE OSTEOLOGICAL DEVELOPMENT OF LARVAL AND JUVENILE GRAY ANGELFISH, POMACANTHUS ARCUATUS (POMACANTHIDAE: PISCES)

Sharon Kelley

ABSTRACT Gray angelfish larvae (Pomacanthus arcuatus) are undescribed, In this study 109 wild caught and reared larval, and one adult p, arcuatus are cxamined for larval pigmentation, squamation, head spination, morphometry, and development of selected osteological features, The larvae do not have a tholichthys stage, but specializations include spinous projections on scales; up 1.045 preopercular spines, as well as a preopereular corner spine and a latero- sensory canal in juvenile specimens, Body depth is 17,85% of body length at 2,8 mm NL and increases to 71.4% in a 200 mm SL adult specimen, Flexion begins at 4,5 mm NL and is complete by 5,0 mm SL Vertebrae appear at 3,7 mm NL as saddle-shaped ossifications and sequence of development is from anterior to posterior, The seeond dorsal and anal fins form concurrently followed sequentially by the caudal tin, tirst dorsal fin, pelvic fin and pectoral fin,

Pomacanthus arcuatus (Linnaeus, 1758), the gray angelfish, is found in reef habitats from New England to the Caribbean and southern Brazil in depths ranging from 1 to 66 m (Fischer, 1977, Feddern, 1972). Morphology of larvae has not been described, although Moe (1976, 1977) described the rearing of specimens used in this study. The adults are well described and frequently studied. For example Peterman (1971) examined coloration and schooling habits; Feddern (1972) analyzed distribution and fishery importance; Behr (1974) studied external anatomy; and Habury et al. (1974) described new locality records in the north- eastern Gulf of Mexico, Fraser-Brunner (1933) revised the chaetodontid subfamily Pomacanthinae, and Burgess (1974) reclassified the group as the family Poma- canthidae. The purpose of this study is to describe larval and juvenile morphology, pigmentation, and the osteological development of the opercular series, vertebral column, fins, fin supports, and squamation in P. arcuatus. Special attention is given to the opercular series to determine if Pomacanthids have a "tholichthys" larval stage which is characterized in part by heavy plate-like spines on the bones of the opercular series. Pomacanthus did not have this development which is probably restricted to the Chaetodontidae (Burgess, 1974; Leis and Rennis, 1983; Leis and Truski., 1989; Leis, 1989).

MATERIALS AND METHODS

A developmental series of 113 Pomacanthus arcuatus, 2,9 mm NL to 31,6 mm SL, and a single wild-caught adult (200 mm SL) (Table I) were examined in this study, Spawning, rearing and hatching of the larvae were described by Moe (1976, 1977), For comparison of pigmentation, squamation, and predorsal formulae, the additional material were examined and listed in Table I, The larvae and juveniles of p, arcuatus were fixed in 5% formalin and then preserved in 70% ethanoL Measurements were made using a calibrated ocular micrometer, following the method of Potthoff et aL (1987), for notol;hord length (NL, before and during flcxion); standard length (SL, after flexion); body depth; snout length; eye diameter; predorsal length; preanus length. Due to growth differences of the specimens, some larger specimens were not as developed as smallcr ones, For the osteological study, specimens were cleared and stained using Potthoff's (1984) method and cxamined in 100% glycerin, JIIustrations were done with the aid of a camera lucida. All larvae were examined

826 KELLEY: POMACANTHUS ARCUATUS DEVELOPMENT 827

Table I. List of specimens of Pomacanthidae and Chaetodontidae used for comparison of pigmentation, scales and predorsal bones development

Number Size range of speci- in Illin Taxon; Genus s.pccics mens SLage (NL or SL) Sections used int Centropyge argi 2 Adult 35.0-37.5 S;PD 34* Larvae & Juvenile 2.0-10.5 P; S; PD Ho/acanthus ci/iaris I Juvenile 60.0 S; PD Ho/acalllhus bermudensis 1 Juvenile 83.8 S;PD Ho/aconthus trie%r 4 Adult 74.0-154.0 S; PD P;S;PD 25* Larvae & Juvenile 2.7-24.1 Pomacalllhus paru 2 Adult 195.0-210.0 P;S;PD 6 Juvenile 9.6-42.7 S;PD Chaetodon capistra/tls 4 Adult 93.0-98.0 S 6 Juvenile 20.0--29.5 Chaerodon ocel/a/tls 2 Adult 130.0-143.0 S Chaetodon sedentarius 4 Adult 88.0--100 S 2 Juvenile 25.9-26.4 Chaetodon striatus 9* Larvae 2.2-2.6 S Proganthodes acu/eatus I Adult 5\.9 S Unidentified genus, Pomacanthidae 2 Larvae & Juvenile 2.3-8.3 S Unidentified genus, Chaetodontidae 19 Larvae & Juvenile 3.5-9.6 S

* Laboratory-reared hlfvae. t P '"""pigmenl; S = scale: PD ;; predol'sal bones.

Table 2. Summary of sizes (NL, SL), ages (days), number of specimens (Num), and flexion stage of Pomacalllhus arcuafus. Notochord and standard lengths are in mm. pre, preflcxion larvae; fxin, specimen undergoing flexion; post, postflexion specimen; unkn, unknown.

Size Age NUlll Stage Size Age Num Stage Size Age Num SLage

2.8 ] I pre 4.2 6 2 pre 6.0 unkn I post 2.9 I 2 pre 4.2 8 I pre 6.0 24 I post 3.0 I I pre 4.3 6 2 pre 6.1 24 I post 3.0 5 I pre 4.3 7 2 pre 6.3 28 I post 3.1 5 2 pre 4.3 10 I pre 6.7 unkn 1 post 3.2 3 I pre 4.4 6 I pre 6.7 24 I post 3.2 5 1 pre 4.4 8 I pre 6.8 19 I post 3.3 3 2 pre 4.5 6 2 pre 6.8 28 I post 3.3 4 ] pre 4.5 ]0 2 fxin 6.9 19 I post 3.3 5 I pre 4.6 8 I fxin 7.1 21 I post 3.4 4 I pre 4.7 8 I fxin 7.2 28 2 post 3.4 5 5 pre 4.8 8 I fxin 7.5 15 I post 3.5 3 3 pre 4.9 unkn 1 post 7.6 21 I post 3.5 4 I pre 4.9 ]0 I fxin 7.8 21 I post 3.5 5 8 pre 4.9 II I post 7.9 24 I post 3.6 4 I pre 5.0 1\ 2 post 8.0 24 I post 3.6 5 2 pre 5.2 I] I post 8.2 19 2 post 3.7 5 I pre 5.4 unkn I post 8.4 24 I post 3.7 7 I pre 5.4 15 I post 8.5 24 I post 3.8 5 I pre 5.5 unkn I post 9.6 37 I post 3.8 7 I pre 5.5 I] 1 post 9.7 37 I post 3.9 6 ] pre 5.5 24 I post 10.2 unkn 2 post 3.9 7 I pre 5.6 unkn 2 post I\.6 unkn I post 4.0 6 I pre 5.8 28 I post 19.1 unkn I post 4.0 7 3 pre 5.9 19 I post 19.6 unkn I post 4.0 8 I pre 5.9 28 I post 3 \.6 unkn I post 200.0 unkn I post 828 BULLETIN OF MARINE SCIENCE, VOL. 56, NO.3, 1995

O.5mm

JcJ

Figure I. Pomacanthus arcuatus preflexion larva 2,9 mm NL. I-day old laboratory-reared, Top: left lateral view; center: dorsal view; bottom: ventral view. under IOOX to ISOX magnification with a binocular dissecting microscope. Specimens are held at Southeast Fisheries Science Center, National Marine Fishery Service, Miami Laboratory, uncataloged. In the following text the reared larvae and juveniles will be referred to by length; their age can be obtained from Table 2. The osteological terms in this study follow Matsui (1967), McAllister (1968), Potthoff and Kelley (1982), and Potthoff et al. (1984, 1987), terms used in squamation section follow Bond (1979) and Johnson (1984),

PIGMENTATION Head Region.- Yolk-sac larvae of Pomacanthus arcuatus (2.8 mm-3.0 mm NL) were pigmented with one to three stellate melanophores scattered across forebrain, one to eight stellate melanophores on midbrain, and one or two large melanophores on anteriormost portion of hindbrain. Scattered melanophores present on snout, and eyes have one to three melanophores on anterior and posterior exterior perimeter of both pupils (Fig. ]). In specimens 3.0 mm NL and larger, midbrain develops uniform pigmentation with superimposed darker single melanophores scattered on top. At 3.1 mm NL pigmentation extends to cover forebrain through nape, and joins trunk pigment. Nostrils develop pigment interiorly and exteriorly. Upper and lower jaw rami acquires 3-5 single melanophores on anteriormost edge of premaxilla and dentary. Eyes become fully pigmented, and angle of jaw, branchiostegal membrane, gular membrane, and isthmus develop scattering of stellate melanophore. In larger larvae 3.2 mm NL to 7.2 mm SL (Figs. 2-5) uniform pigmentation spread anteriorly and posteriorly until entire head region pigmented except for posterior half of premaxilla, middle of maxilla (just anterior to the eye), branchiostegal membrane, oromandibular area, posterior edge of opercle, preopercIe, subopercle, and interopercIe. These unpigmented areas on head later became three head balrs. One 8.4 mm SL specimen and specimens 9.6 through 31.6 mm SL has the recognizable juvenile pigment pattern of three vertical bars in head region. First bar medial on snout, extending from anterior portion of midbrain crossing premaxilla onto lower jaw (forming characteristic lower jaw pigment which separates juvenile P. arcuatus from juvenile P. paru) and contin- KELLEY: POMACANTHUS ARCUATUS DEVELOPMENT 829

O.5mm

Figure 2. Pomacanthus arcuatus preflexion larva 3.2 mm NL. 3-days old laboratory-reared. Top: left lateral view; center: dorsal view; bottom: ventral view.

ues ventrally to isthmus. Second bar proceeded ventrally from edge of maxilla to angle of jaw. Third bar just posterior to eye was first seen at 4.9 mm SL. From 5.0 to 7.9 mm SL this area immediately posterior to the eye extending dorsally from midbrain to just anterior of pelvic fin continues to lose pigment until the third bar is complete (Figs. 6, 7).

Trunk and Tail Region.-Trunk and tail region of 2.8 mm NL larva had two lateral rows of single melanophores from just posterior of eye to just posterior of pectoral fin. Melanophores uniformly cover laterally from posterior of pectoral fin to just anterior of caudal, with darker stellate melanophores scattered on top of uniform pigmentation (Fig. I). From 3.2 mm NL to 4.5 mm NL or SL uniform pigmentation spread anteriorly and posteriorly (Figs. 2, 3). By 4.5 mm SL, only caudal peduncle section was not uniformly covered by pigmentation. Darker more prominent stellate melanophores were scattered on top of uniform trunk pigmentation. In specimens 4.5 to 7.1 mm SL pigmentation spread posteriorly to caudal region, and fish appeared solid gray-black color (Figs. 4, 5). At 7.2 mm SL partial unpigmented midlateral bar was present, extending dorsally from ventral edge of anus to lateral midline. Two unpigmented vertical bars were formed on trunk of specimen 7.9 mm SL complete midbody bar, from dorsal edge of posterior spines of dorsal fin to vent, and partial second bar anterior of caudal peduncle from posterior dorsal edge of dorsal fin rays to just dorsal posterior edge of anal fin. An 8.4 mm SL specimen and specimens 9.6 through 31.6 mm SL (Figs. 6, 7) with recognizable juvenile pigment pattern of five vertical bars three on head, two on trunk. Single stellate melanophores scattered within each bar. 830 BULLETIN OF MARINE SCIENCE, VOL. 56, NO.3, 1995

Figure 3. Pomacanthus arcuatus preftexion larva 4.4 mm NL. 8-days old laboratory-reared. Top: left lateral view; center: dorsal view; bottom: ventral view.

Caudal Fin.-First occurrence of pigmentation in caudal region in 11.6 mm SL specimen, in form of vertical scattering of melanophores medially (Fig. 6), In largest juveniles examined (19.9 to 31.6 mm SL; Fig. 7) discernible vertical bar of pigment present on caudal fin.

Dorsal and Anal Fins.--At 2.8 mm NL, dorsal-fin fold pigmented along dorsal edge and one to two large stellate melanophores above 4 to 6th and 12 to 14th myomere. Anal·-fin fold pigmentation opposite dorsal-fin fold pigment along ventral edge from vent to just posterior of vent. Fin fold anterior of anus has stellate melanophores along posterior ventral edge and one large stellate melanophore on ventral edge of gut (Fig. 1). No significant changes in fin pigmentation occur until 4.3 mm NL. Between 4.3 mm NL and 4.6 mm SL dorsal and anal fin membranes develop pigment along body margins at base of fin folds. Pigment progression dorsally and ventrally dlistad from fin bases, and from anterior to posterior (Fig. 4). First dorsal fin completely pigmented by 4.9 mm SL, and second dorsal fin pigmented on ventral two thirds of rays. Membrane between first two anal fin spines is pigme:nted; and remaining rays pigmented on proximal two thirds. At 7.9 mm SL second dorsal fin pigment is lost dorsally above mid-body and caudal peduncle bars. In pigmented areas of fins distal expansion of pigment continues. In larger specimens both bars continue distally to dorsal edge of second dorsal fin and ventrally fifth bar to edge of anal fin, until becoming a slight scattering. Pigment progression on second dorsal and anal fin distal until entire fins covered except for bar areas (Figs. 6, 7). KELLEY: POMACANTIIUS ARCUATUS DEVELOPMENT 831

Figure 4. Pomacanlhus arcualUS postflexion larva 5.0 mm SL. II-days old laboratory-reared. Top: left lateral view; center: dorsal view; bottom: ventral view.

Figure 5. Pomacanlhus arcuatus postflcxion larva 7.2 mm SL. 28-days old, laboratory-reared. Left lateral view. 832 BULLETIN OF MARINE SCIENCE. VOL. 56. NO.3. 1995

Figure 6. Pomacanthus arcuatus juvenile 11.6 rnm SL. Age unknown, laboratory-reared. Left lateral view.

Pectoral and Pelvic Fins.-The pectoral fin lacks pigmentation in specimens 2.8 mm NL-31.6 mm SL except one 9.7 mm SL specimen, which has a scattering of melanophores in center. Pigmentation is first seen on proximal edge of pelvic fin at 4.5 mm NL, and continues distally, covering entire pelvic fin by 5.5 mm SL (Figs. 4-7).

SQUAMATION AND HEAD SPINATION DEVELOPMENT Larvae of P. arcuatus first develop one row of 4-5 scales along the lateral line at 3.5 mm NL. Scales begin anteriorly at approximately tenth centrum, and continue posteriorly to just anterior of caudal peduncle. Next to develop, three to four rows of scales ventral of lateral line in caudal region. These rows consecu- tively shorter ventrally in anterior-posterior direction forming triangle. In nape area, one row of 5-6 scales develops at ventral edge of dorsal fin fold, extending from just below anterior edge of dorsal fin to about 10th centrum. In mid-brain and hind-brain regions one to two scales develop. Addition of median scales anteriorly, to posterior border of opercle and posteriorly to caudal peduncle covering ventral half of caudal region. Scale development in gut region starts on ventral surface, from pectoral cleithrum symphysis to anus and continues dorsally to cover gut. Squamation continues to spread to dorsal edges of maxilla, premaxilla, in cheek area, on opercular bones, and on pectoral fin radials (Fig. 4). Mid-brain scales spread anteriorly and posteriorly to completely cover head region dorsally. Parallel scale rows spread dorsally and ventrally covering body laterally to urostyle. In specimens of 5.1 to 6.0 mm SL scales spread on to first and second dorsal and anal fin rays. In cheek area scales added in ventral direction and completely cover cheek to articular region. Scales develop posteriorly in caudal region to posterior edge of hypurals. KELLEY: POMACANTHUS ARCUATUS DEVELOPMENT 833

Figure 7. Pomacanthus arcuatus juvenile 31.6 mm SL. Age unknown, laboratory-reared. Left lateral view.

Development of scales from 6.1 to 11.6 mm SL is anterior to posterior covering entire body, except for following areas: just anterior to eye and ventrad to nostrils; posterior portions of maxilla, premaxilla, and dentary; distal end of gular membrane; pectoral, pelvic, caudal fin rays; and on distal ends of dorsal and anal fin rays. In specimens larger than 19.0 mm SL, only areas with no type of skin or membrane covering i.e., branchial rays, posterior tip of caudal, and pectoral fin rays are not completely covered by scales. Individual scales first observed at 3.5 mm NL develop as round-oval shape structures with one recurved spine in center. Two to four posteriorly recurved spines added to center between 5.3 and 8.0 mm SL forming row. By 11.6 mm SL scales acquire one posterior spine dorsal and one posterior spine ventral of central spine. Four circuli visible at 11.6 mm SL and posterior spines increase to four at center and two on distal edge. By 24.6 mm SL specimen's scales have adult characteristics. Spines extend progressively distal, and from focus to exterior edge nine circuli present, but no radii (Fig. 8). At 31.6 mm SL elongated posteriorly recurved spines in posterior field are double, 31 circuli present and radii at or just posterior to anterior edge extending inward toward center. Adult P. arcuatus spines fuse to base forming linear rows of elongated, ridge-like ctenii on distal edge. Scales regularly arranged and overlap, posterior part of anterior scale 834 BULLETIN OF MARINE SCIENCE. VOL. 56. NO.3. 1995

Ctenii-Spines

CtEmii-Spines Focus Ctenii

Figure 8. Ontogeny of scales of Pomacanthus arcuatus, lateral external view. Top left to lower right (specimen's lengths in mm NL or SL; size measurement of scale) were: A) 4.7; 0.1 mm: B) 8.0; 0.14 mm: C) 11.6; 0.15 mm: D) 24.6; 0.5 mm: E) 31.6; 0.5 mm: F) 210; 6.5 mm.

overlaps anterior portion of posterior scale. In larval and juvenile specimens this overlapping causes posterior field spines to be exposed (Fig. 8). Eight serrated spiny ridges develop on the following head bones: supraorbital ridge of frontal; eirumorbital-suborbital, (s02, s03, s04); nasal; pterotic; post-temporal; suprac1eithrum; and dentary (Fig. 4). Description of spines on bones of opercular series is provided below (see "Osteological Development"). By 31.6 mm SL all ridges disappeared except for frontal orbital ridge.

MORPHOMETRIes

Larvae of P. arcuatus between 2.8 to 3.0 mm NL are elongate, with moderately long gut and average body depth of 15.5%. By 3,1 mm NL all specimens absorbed yolk sac. Gut begins to coil at 3.4 mm NL and tightly coiled by notocord f1extion. Notochord flexion begins at 4.5 mm SL with two of my four specimens, all larvae 5.0 mm SL and larger are flexed. Body continues to become increasingly more laterally compressed, and by notochord flexion body depth doubled to 41.0%. Mouth acquires adult specialized beak-like nature after 24.6 mm SL as corrobo- rated by snout length decrease as head deepens and shortens (9.5 mm SL to 24.6 mm SL) and then increases again (Figs. 6, 7). Eye diameter increases in specimens from 2.9 (0,7%) to 3.0 mm NL (1.0%), and thereafter remains same size (0.30 mm) until flexion. After flexion eye diameter gradually increases until 24.6 mm SL, eye diameter ratio then decreases. Eyes start to become proportionately smaller and move upward beyond hyomandibular as described by Gregory (1959) (Table 3). KELLEY: POMACANTHUS ARCUATUS DEVELOPMENT 835

Table 3. Summary of morphometric data of Pomacanthus arcuatus. Measurements are proportional values relative to notochord (preflexion and flexion specimens) or standard lengths (postflexion spec·· imens). Specimens between dotted lines are undergoing notochord flexion.

Size in Body Snout Preopercle Eye Predorsal length Preanal length 2.8 17.8 03.2 00.7 50.0 2.9 14.5 03.4 00.7 14.0 51.7 3.0 15.0 03.3 01.0 13.0 53.0 3.1 21.0 07.4 07.1 01.0 29.0 62.9 3.2 15.6 06.3 06.3 00.9 18.8 53.1 3.3 18.2 07.0 07.6 00.9 22.8 53.0 3.4 17.6 08.8 05.9 00.9 29.4 52.0 3.5 17.1 07.1 08.6 00.9 28.6 52.9 3.6 20.8 09.7 08.3 00.8 38.9 55.6 4.2 16.7 09.5 09.5 00.7 38.1 52.4

------.------.-.------..------4.5 28.9 11.1 06.7 00.9 42.2 57.8 4.9 40.8 12.2 04.1 01.1 49.0 61.2 ------.-._------.------.------5.2 46.2 11.5 07.7 01.2 51.9 65.4 5.4 48.1 11.1 05.9 01.2 49.1 65.7 5.9 45.8 10.2 05.6 01.2 47.5 64.4 6.1 47.5 11.5 08.2 01.3 47.5 65.6 6.3 47.6 11.1 04.8 01.3 47.6 65.1 6.8 55.0 08.8 05.9 01.2 51.5 67.6 6.9 55.1 11.6 05.8 01.3 50.7 69.6 7.2 50.0 12.5 05.8 01.3 50.0 66.7 7.6 59.2 11.8 06.6 01.1 48.7 68.4 7.8 59.0 10.3 05.8 01.2 48.7 70.5 8.0 50.0 12.5 05.0 01.4 50.0 75.0 8.1 60.4 15.3 06.2 01.4 49.4 71.6 9.5 54.7 10.0 05.3 01.6 49.5 68.4 9.6 55.2 09.7 05.2 01.5 49.0 66.7 10.2 58.8 10.8 10.3 01.5 49.0 66.7 10.7 62.6 10.3 10.8 00.9 50.0 67.3 11.6 53.4 10.3 17.2 01.3 53.4 65.5 24.6 63.0 07.3 10.2 01.5 47.6 68.7 31.6 58.5 09.8 11.4 01.4 46.2 71.2 200.0 71.4 14.3 13.6 06.7 46.7 65.7

OSTEOLOGICAL DEVELOPMENT Opercular Series.-(Fig. 9). Preopercle first bone in the opercular series to develop (3.2 mm NL), and clearly visible in larvae and juveniles. Preopercle interior shelf develops up to 40 spines in specimens 24.6 mm SL and smaller. In specimens larger than 11.6 mm SL posteriorly directed corner spine of interior shelf begins to elongate, and all other spines become smaller as size increases. Except for few small spines and elongate corner spine, interior shelf is smooth by 31.6 mm SL. Exterior lateral preopercle ridge develops up to 45 spines in specimens 11.6 mm SL and smaller. In juveniles 19.1 mm SL and larger the exterior shelf fused to interior shelf forming latero-sensory canal. Opercle develops next at 3.6 mm NL followed by interopercle at 4.0 mm NL and subopercle at 4.5 mm NL. Opercle develops one spine on posterior edge which is retained as vestige when adult, interopercle and subopercle develop total of 1-22 spines on their posterior edges, which are lost in juveniles. Subopercle develops long dorsal process forming an acute angle that opercle fits into (Fig. 9). All four opercular bones of dermal origin. 836 BULLETIN OF MARINE SCIENCE, VOL. 56, NO.3, 1995

1 .1mm

t---i 1------1 .1mm 1mm

SOP

Figure 9. Ontogeny of the left opercular series of Pomacanthus arcuatus, lateral external view. Top left to right specimen's lengths in mm NL or SL were: 4.4, 5.2, 7.2, I1.6, 31.6: ES, exterior shelf of preopercle: lOp, interopercle: IS, interior shelf of preopercle: Op, opercle: POp, preopercle: SOp, subopercle.

Vertebral Column.-P. arcuatus has 24 vertebrae, 10 precaudal and 14 caudal. Specimens 2.8 to 3.0 mm NL have straight notochord with no development of neural or haemal spines. All specimens 4.4 mm NL and larger have full count of 24 vertebrae (Fig. 10). Ossification of notochord begins at 3.7 mm NL anteriorly with five dorsal saddle-shaped ossifications on vertebrae 1-5. These saddles of bone extend ventrally and coalesce forming individual centra. Ribs present at 6.7 mm SL with seven pairs of plural ribs on vertebrae 3-9 and 12 pairs of epipleural ribs on vertebrae 1-12. Development of plural and epipleural ribs from anterior to posterior, Adult count of seven or eight pairs of plural ribs supported by precaudal vertebrae, and 14 pairs of epipleural ribs supported by precaudal vertebrae and first four caudal vertebrae, first observed at 7.2 mm SL for epipleural ribs KELLEY: POMACANTfIUS ARCUATUS DEVELOPMENT 837

Pomacanthus arcuatus

PREDORSAL FIRST SECOND BONES DORSAL FIN DORSAL FIN

30 30 27 31 31 31 31 31 31 31 29 20 19 26 18 21 21 17 14 8 E

0 0 3 2 1 1 1 1 1 2 2 2 3 3 3 3 3 3 3 4 D

1 1 1 2 1 1 1 1 1 2 2 2 3 3 3 3 3 3 3 3 C 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 B . IS 11 I 2 13 14 15 16 17 18 19 1101111121131141151161171181191201211221231241 A 11 12 13 14 15 16 17 18 19 20 B •

1 2 2 3 3 2 3 3 4 1 C

3 2 2 3 3 2 3 3 4 2 D

34 33 17 23 17 18 11 13 10 10 E

ANAL FIN

Figure 10. Common arrangement of predorsal bones, pterygiophores, fin spines and rays in relation LOthe skull and vertebral column for 34 Pomacanthus arcuatus; Modified after Matsui (1967). A, skull and vertcbrae numbers; B, interneural and interhaemal space numbers; C, number of pterygiophores in the respective interneural or interhaemal space; D, number of fin spines or rays associated with the pterygiophore; E, frequency of occurrence in 34 specimens for the pLerygiophore number in thc respective interneural or intcrhaemal spaces; S = skull. and 8.0 mm SL for plural ribs; all specimens 11.6 mm SL and larger have adult complement. One cartilaginous neural spine develops on first vertebra at 3.1 mm NL, and all specimens 3.7 mm NL and larger have some neural arches and spines. Neural arch and spine development proceeds from anterior to posterior. Cartilag- inous haemal arches and spines first develop at 3.7 mm NL, all specimens 4.3 mm NL and larger have some development of haemal arches and spines. Addition of haemal arches and spines from anterior to posterior. First haemal arch develops on eighth vertebra. Individual neural and haemal arches and spines begin ossification at proximal base and ossification proceeds distally; concurrently, ossification of spines and arches begins distally and proceeds towards proximal base, joining base ossification and completing neural and haemal ossification (Figs. 10, 11).

Caudal Fin and Supports.-Parhypural and hypural I first appear in 4.3 mm NL specimen with 18 neural and eight haemal spines present. Hypurals 2-4 develop next in ten-day old specimen of same size. Hypural 5 present at 5.0 mm SL. Hypurals develop ventral to straight notochord as separate cartilaginous pieces, but fuse proximad during notochord flexion. Eight principle caudal fin rays (4 + 4) develop at 4.5 mm NL, three rays associated with hypural I; one with hypural 2; two with hypural 3; and two with hypural 4. Full complement of principle caudal fin-rays (9 + 8) present at 5.0 mm SL. Secondary caudal fin-rays start developing at 5.4 mm SL. All specimens 7.2 mm SL and larger have full adult complement of secondary fin-rays (3-4 + 3-4). No procurrent spur or shortened ray bases present in P. arcuatus. Caudal fin rays supported by three vertebrae; preural centrum 3 with autogenous haemal spine and nonautogenous neural spine; preural centrum 2, with autogenous haemal spine, specialized neural arch and three epurals above; urostyle fuses to paired uroneural forming neural canal, and urostyle supports parhypural with posteriorly directed parhypurapophysis and five 838 BULLETIN OF MARINE SCIENCE. VOL. 56. NO.3. 1995

2 6 8 10 12 14 16 18 20 22 24 fl 3.1mm NL I

3.4mm NL

n 3.7mm NL

4.0mm NL

2 6 8 10 12 14 16 18 20 22 24

Figure II. Schematic representation of vertebral column, dorsal and anal fin, and fin support development in Pomacanthus arcuatus. Scales represent vertebrae numbers. Cartilage, white; ossifying, stippled. autogenous hypurals. P. arcuatus develops one dorsal and three ventral radial cartilages; dorsally, radial cartilage anterior to neural spine of PU3. Ventrally radial cartilages: one anterior to haemal spine of PU3, one anterior to haemal spine of PU2, and third anteriorly distal to haemal spine of PU2. Pattern of ossification of caudal fin skeleton: uroneural (ossified first at 5.0 mm NL), parhypural, hypurals 1-5 and epurals. Ossification proceeds from proximal edges distally. Pectoral Fin and Supports.-Cartilaginous cleithrum, coraco-scapular cartilage bearing only posterior process, and cartilaginous semicircular blade surrounded by finfold in smallest cleared and stained specimen (3.1 mm NL). Sequence of KELLEY: POMACANTfJUS ARCUATUS DEVELOPMENT 839 development: one cleavage develops in center of cartilaginous semicircular blade and anterior process develops on coracoid, this anterior process elongates. Scap- ular foramen, postcleithrum I, supracleithrum, posttemporal and postcleithrum 2 then develops. Pectoral fin blade develops second cleavage at 4.4 mm NL, third cleavage not observed, but one 5.9 mm SL specimen has all four radials developed and ossifying. First four pectoral rays to appear in dorsal portion of finfold at 4.7 mm SL, rays added in a ventral direction. All specimens 7.9 mm SL and larger have adult count of 19-20 pectoral fin rays (Randall, 1968). First supratemporal- intertemporal develops at 5.9 mm SL of dermal origin. Second supratemporal- intertemporal develops at 6.0 mm SL and 8.0 mm SL specimen bears third supratemporal-intertemporal, thus making up full adult complement of 14 pectoral girdle bones. Ossification of pectoral girdle begins at 4.7 mm SL, on posterior process of coracoid, cleithrum, supracleithrum, postcleithrum I and 2, and posttemporal. Dorsal portion of scapula and anterior process of coracoid ossify next at 5.5 mm SL. Ossification proceeds dorsally and ventrally (from both ends toward middle) on coraco-scapular until just thin line of cartilage separates coraco-scapular cartilage. During development posterior process of coracoid becomes smaller and anterior process elongates.

Pelvic Fin and Supports.-Pelvic fin basipterygium appears at 4.3 mm NL ventral to posterior process of coraco-scapular, and no spine or ray initially associated with it. Pelvic spines and rays first appear at 4.5 mm NL and the adult compliment of 1,5 is present in specimens 6.3 mm SL and larger.

Spinous Dorsal Fin and Supports.-Adult P. arcuatus have single predorsal bone in each of first two interneural spaces and seven pterygiophores supporting nine to 10 (usually nine) serially associated spines in interneural spaces 3-8 (Fig. II). Initial development of spinous dorsal fin pterygiophores in interneural spaces 3- 8 at 4.3 mm NL, no predorsal bones developed. First dorsal fin spines to develop: posteriormost three spines in interneural spaces 6-8. Other specimens between 4.3 and 4.9 mm SL have comparable development of pterygiophores but lack spines. Adult complement present at 4.9 mm SL. Each pterygiophore and predorsal bone develops from single piece of cartilage, except for anteriormost ptc- rygiophore. This pterygiophore develops as two pieces of cartilage, observed at 5.2 mm SL, these pieces fuse to form single cartilaginous pterygiophore. With exception of two specimens which supports four spines (three supernumerary and one serial spine), anteriormost pterygiophore supports three spines (two supernumerary and one serial spine) and always inserts in third interneural space. Remaining spinous dorsal fin pterygiophores support single spine with distal radial located between bifurcated bases of spines. Ossification of pterygiophores commences anteriorly at 4.9 mm SL and proceeds in posterior direction. By 5.8 mm SL all first dorsal pterygiophores ossified (Figs. 10, II).

Soft Dorsal Fin and Supports.-Adult complement of second dorsal-fin elements 29-32 pterygiophores (usually 32) supporting 30-33 (usually 33) rays (Fig. II). Second dorsal fin pterygiophores begin to develop at 4.0 mm NL concurrently, opposite anal fin pterygiophores begin to develop. Five pterygiophores initially appear in interneural spaces 10-13, with no associated fin rays (Fig. II). Devel- opment of fin rays begins at 4.4 mm NL on ten anteriormost pterygiophores (Fig. 10). Complete adult complement of 29 pterygiophores first visible at 5.0 mm SL, and full complement of rays at 6.0 mm SL. Ossification begins at 5.4 mm SL, and all second dorsal fin pterygiophores ossified by 5.8 mm SL. Anteriormost second dorsal fin pterygiophore usually inserts into ninth interneural space. Pos- 840 BULLETIN OF MARINE SCIENCE, VOL. 56, NO.3, 1995

Figure 12. Holacamhus tricolor preflexion larva 2.6 mm NL. Unknown age laboratory-reared. Left lateral view. teriormost dorsal fin pterygiophore usually inserts in 20th interneural space, and has cartilaginous stay ventral to proximal radial which supports double ray. Stay originates from last pterygiophore, becoming autogenous after ossification (Figs. 10, 11). Anal Fin and Supports.--Adult P. arcuatus have 22-24 anal fin pterygiophores (usually 24) that support three spines (two supernumerary and one serial spine) in association with anteriormost pterygiophore, and 22-24 (usually 24) fin-rays in serial association with remaining pterygiophores (Fig. 10). First anal fin development in P. arcuatus at 4.0 mOl NL. Anteriormost four pterygiophores develop in interneural spaces 10-13 with no associated spines or rays. Paralleling second dorsa] fin development as described above. Posteriormost anal-fin spine and anteriormost five rays develop at 4.4 mOl NL. Sequence of development anterior to posterior. Except for anteriormost pterygiophore, each pterygiophore develops from single piece of cartilage. Anteriormost pterygiophore develops from two pieces of cartilage, visible in one 4.3 mm NL specimen, which fuses into a single cartilaginous pterygiophore. Posteriormost pterygiophore has cartilaginous stay dorsa] to proximal radial and supports double ray. Stay originates from pterygiophore cartiRage and becomes autogenous after ossification. Pteryg- iophore ossification begins at 4.9 mm SL and all pterygiophores ossify by 6.8 mOl SL. Full adult pterygiophore complement present at 5.2 mm SL. Adult complement of spines and rays first appear at 6.0 mOl SL (Fig. 11).

DISCUSSION Pomacanthus arcuatus larvae are heavily pigmented with dark uniform melanophores. Comparison of pigment patterns among larval Atlantic Pomacanthidae showed that only P. pam is easily confused with P. arcuatus. Examination of a wild-caught 9.6 mm SL specimen of P. paru reveals pigment uniformly covering the body, overlain by darker more prominent scattered stellate melanophores and resembling P. arcuatus of the same size (Table 1). The P. pam juvenile has pigment on the lower jaw and lacks the bar that characterizes P. arcuatus. Larvae of Holacanthus bermudensis and H. ciliaris were unavailable for study, but the uniform pigmentation of P. arcuatus is lacking in Holacanthus tricolor, Centro- pyge argi and Centropyge sp. (Figs. 12, 13; Table 3). Richards' (1990) illustrations of wild-caught 2.8 mOl NL, 4.1 mOl SL, and 12.5 mOl SL specimens iden- tified as Centropyge argi, as well as the larvae of Centropyge sp. illustrated by Leis and Rennis (1983), C. interruptus by Hioki and Suzuki (1987) and C. ferrugatus illustrated by Hioki et al. (1990) do not have heavy uniform pigmentation. The same is true for the genus Genicanthus. Suzuki et al. (1979) reared Geni- canthus lamarck and Hioki et al. (1982) reared Genicanthus melanospilos, and neither species of larvae resembled P. arcuatus. KELLEY: POMACANTHUS ARCUATUS DEVELOPMENT 84]

Figure 13. Cenlropyge argi preflexion larva 2.0 mm NL. Unknown age laboratory-reared. Left lateral view.

Examination of scale development of P. arcuatus (Fig. 8), and the adult scales of other atlantic angelfish (Centropyge argi, H. ciliaris, H. bermudensis, H. tricolor, P. paru), three juvenile and larval angelfish (c. argi, H. tricolor, P. paru) (Figs. 14, 15), adult atlantic butterfly fishes (Chaetodon capistratus, C. ocellatus, C. sedentarius, C. striatus, Prognathodes aculeatus), "tholichthys" stage larvae and juveniles of C. striatus, and "tholichthys" stage juveniles of unknown butterfly fish (Fig. 15) shows that one of the most obvious differences between the two families is in morphology and development of the scale and ctenii (Figs. 14, 15; Table 3). All of the pomacanthids examined have essentially the same shape and type of scale, in larvae, the ctenii form long posteriorly directed ctenii-spines which develop into ridge like ctenii as adults (Fig. 14). Roberts (1993) calls pomacanthid scales type 2 spinoid and shows two scanning electron microscope photos of P. semicirculatus. Both match the type of scales I found. Burgess's (1974) figure I showing scales of adult Centropyge sp. and Chaetodontidae also agree with scales I found for both families (Figs. ]4, ]5). Leis and Rennis (1983) illustrated a 4.4 mm SL larval Centropyge sp. with the same formation of body scale spines as illustrated in my 5.0 mm SL larvae (Fig. 4). Kojima and Okiyama (1988) described Chaetodontoplus septentrionalis and illustrated a 7.2 mm SL specimen and a single scale. This scale matches my 8.0 mm SL scale in Figure 8. Johnson (1984: table 121) shows pomacanthids as characterized by the presence of spinous scales in specimens up to 17-19 mm and classified the scales of adult Pomacanthidae as Ct' ("continuous spinous projections from the lateral surface and posterior margin of the scale") and may be a "retention of the plesiomorphic beryciform condition." Spinous larval scales similar to those found in P. arcuatus are found in larvae of Bramidae, Chaetodipterus, Chiasmodontidae, Howella, Lethrinidae, Malacanthidae and Scatophagidae (Johnson, 1984) and Xiphias gladius (Potthoff and Kelley, 1982). Scale morphology was used by Cockerell (1915, 1916) and Burgess (1974) as one of the characters separating pomacanthids and chaetodontids. All pomacanthid scales I've observed by photo or examination are identical in type and form making this an excellent diagnostic phylogenetic character. Scale development of chaetodontid larvae and juveniles differs completely from that of pomacanthids. Chaetodon have true scales with very tiny ctenii on the posterior half and circumscribing the posterior edge, with no developmental change in the adult scales (Fig. ]5). In agreement with my findings for P. arcuatus, Johnson (1984: table 121) states that larvae of the family Pomacanthidae have spination on the supraorbital, a lateral ridge with one or more small simple spines, subopercle, interopercle, posttemporal, supracleithrum, lacrimal, circumorbital, nasal, and dentallY Similar ridg- 842 BULLETIN OF MARINE SCIENCE, VOL. 56, NO.3, 1995

A a

c c

Figure 14, Ontogeny of scales of specimens of Pomacanthidae used for comparison to p, arcuatus, lateral external view. Top left to lower right (specimen; specimen's lengths in mm SL; size measurement of scale in mm) were: A) H. tricolor; 32.8; 1.6 mm: a) H. tricolor; 154.0; 6,0 mm: B) C. argi; 10.2; 1.1 mm: b) C. argi; 37.5; 2.1 mm: C) P. paru; 9,6; 0,1 mm: c) P. paru; 210; 5,5 mm: D) H. ciliaris; 60; 2.1 mm, KELLEY: POMACANTHUS ARCUATUS DEVELOPMENT 843

Figure 15. Ontogeny of scales of six specimens of Chaetodontidae and one Pomacanthidae used for comparison to P. arcuatus, lateral external view. Top left to lower right (specimen; specimen's lengths in mm SL; size measurement of scale in mm) were: A) C. capistratus; 20.0; 0.7 mm: B) C. capistratus; 98.0; 4.5 mm: C) C. sedentarius; 25.9; 0.9 mm: D) C. sedentarius; 90.0; 4.3 mm: E) P. aculaetus; 51.9; 1.9 mm: F) C. ocellatus; 145; 7.2 mm: G) H. bermudensis; 80.0; 2.1 mm. 844 BULLETIN OF MARINE SCIENCE, VOL. 56, NO.3, 1995 es in the head region are generally found in larvae with cranial ornamentation and supraorbital serration are common in many percoids (Iutjanids, malacanthids, monodactylids, Stereolepis, some carangids, acropomatids, haemulids, sciaenids and serranids) (Johnson, 1984). Morphometries for P. arcuatus are in general agreement with those provided by Leis and Rennis (1983). P. arcuatus differences are flexion at 4.5 mm and larger and that proportions are smaller for pretlexion minimum proportional lengths, and equal or below for maximum pretlexion proportional lengths. Post- tlexion proportions are equal or larger, except for body depth which is smaller for both the minimum and maximum lengths (Table 2), Posttlexion p, arcuatus larvae are similar in body shape to the laterally compressed larvae of carangid, chaetodontid, monodactylid, callanthiid, and the haemulid (Pseudopristipoma ni- gra), although each of the: above mentioned families differs in various characters (fin shape, pigmentation, spinous, opercular bones) from Pomacanthidae and P. arcuatus. The preopercIe of P. arcuatus develops a corner spine, characteristic of Po- macanthidae. A latero-sensory canal tunnel forms when the exterior shelf fuses to the interior shelf on the preopercIe in specimens 19.1-31.6 mm SL (Fig. 9). The spine at the angle of the preopercIe and subopercIe process are used by Burgess (1974) to separate the Pomacanthidae from Chaetodontidae. Gregory (1959) discussed the preopercIe spine and the latero-sensory canal tunnel in relation to the opercular series and its uses. Similar development of the latero- sensory canal on the preopercle was described for Anisotremus virginicus (Hae- mulidae) (Potthoff et aI., 1984; pers. obs.), and Lutjanus campechanus (Lutjanidae) (Potthoff et aI., 1988; pers. obs.). Gregory's (1959) illustrations of teleosts shows various species with the sub- opercIe process and similar placement of the opercular bones. This appears to be a common characteristic for perciforms, Anisotremus virginicus (Haemulidae) (Potthoff et aI., 1984; pers, obs.), Microspathodon chrysurus (Pomacentridae) (Potthoff et aI., 1987; pers. obs.), and Lutjanus campechanus (Lutjanidae) (Pott- hoff et aI., 1988; pers. obs.) larvae showed development of a similar process on the subopercle. Examination of the subopercle-opercle relationship shows that the opercle fits into the angle of the subopercle, by the development of the long process. In more primitive fish (Tarpon atlanticus) and orders with familial spe- cialization (Chaetodontidae), either the subopercle is missing or missing the process (Gregory 1959). Burgess's (1974) figure 3 of Holacanthus sp. opercular bones are similar in shape to my 31.6 mm SL P. arcuatus illustrated in Figure 7. In P. arcuatus the sequence of development and ossification of the vertebral column, neural and haemal arches and spines is anterior to posterior (Fig. 11). Potthoff et aI. (1986) discussed the development of neural and haemal arches and spines for the scombroid Xiphias gladius, the sequence of development and first appearance of fins of which P. arcuatus closely parallels. Notochord ossification starts as dorsal and ventral saddle-shape ossifications, the bone extending and coalescing to form individual centra. This type of development was observed in the scombroids for Scombrolabracidae, Gempylidae and Scombridae and differed in Istiophoridae, Xiphiidae, Trichiuridae (Potthoff and Kelley, 1982; Potthoff et aI., 1986); saddle-shape ossification also occurs in Lutjanus campechanus (Pott- hoff et aI., 1988; pers. obs,). I was unable to determine at the time of this study if saddle-shape ossification is a common element in all Atlantic Pomacanthidae or in the Chaetodontidae due to a lack of cleared and stained specimens of the needed size. Occurrence of this type of vertebral ossification has not been studied in enough taxa for the significance to be commented on. KELLEY: POMACANTHUS ARCUATUS DEVELOPMENT 845

The configuration of the caudal skeleton and presence of radial cartilages anterior to the neural spine and haemal spine of PU3 agrees with Johnson's (1975, 1983, 1984) description of primitive features of the percoid caudal skeleton. Po- macanthus arcuatus lacks a procurrent spur and a preceding shortened ray base, as do six species of Chaetodontidae examined by Johnson (1975). Feddern (1972) states that Pomacanthus arcuatus is characterized by 8 to 10 spines in first dorsal fin. Randall (1968) and Robins et al. (1986) noted that P. arcuatus has nine spines. Miller and Jorgenson's (1973) meristic table has 10 spines for P. arcuatus. Johnson (1984) showed Pomacanthidae as having nine to 15 first dorsal fin spines and one or two predorsal bones in interneural spaces one or one and two. Comparison of my findings for P. arcuatus, the spinous dorsal fin spine counts are that 23 out of 29 specimens examined have a count of nine spines, six have a count of 10, two of the six have abnormal associations of four spines associated with the first pterygiophore, and no specimens have a count of eight spines. Although no counts of eight are found in any of my specimens, the usual count of nine is in agreement with Feddern (1972) and Randall (1968), and within the range given by Johnson (1984) for the family. My counts did differ from Randall's (1968) and Miller and Jorgenson's (1973) findings, with only six specimens having a count of 10 spines. Using the predorsal bones formulae of Ahlstrom et al. (1976) and in agreement with Johnson (1984) the pattern of Po·· macanthidae is 0/0/2/1 + II and 0//2/1 + 1/. Figure 10 shows that in all specimens examined, the arrangement is one predorsal bone in the first interneural space, one in the second interneural space, and the first pterygiophore with three spines in the third space; the first two spines are supernumerary and the third serial or secondarily associated (010/2/1 + I). Examination of other juvenile and adult spec·- imens of atlantic angelfish H. tricolor, C. argi, P. paru, H. ciliaris, and H. bermudensis were in agreement with Johnson's findings. I examined three juvenile and five adult H. tricolor, two adult C. argi, one H. ciliaris, and one H. bermudensis. All specimens have only one predorsal bone in the first interneural space, none in the second, and the first pterygiophore with three spines in the third space; the first two spines supernumerary and third serial or secondarily associated (011 2/1 + I). Examination of five juvenile and two adult P. paru shows that they have the same predorsal bone arrangement (010/2/1 + I) as P. arcuatus (Fig. 16). Feddern's (1972) second dorsal fin-ray counts for P. arcuatus are 29-33 (usually 31-32) rays. Randall's (1968) count is 31 to 33 rays, and Miller and Jorgen- son (1973) have a count of 28-29 rays. Johnson (1984) gave the family counts as 15-33. Comparison of the soft dorsal fin counts shows Feddern (1972) has the same findings as mine. Randall (1968) and Johnson's (1984) counts are within the range of my findings, and Miller and Jorgenson (1973) are equal or below mine. Johnson (1984) states the family Pomacanthidae develop stays and that there are stays in 80 out of 96 percoid groups. In both the second dorsal and anal fin of P. arcuatus the last pterygiophore develops a stay and supports a double ray. My anal fin count completely disagrees with Feddern's (1972) count of three spines and 17-20 soft rays; r have no specimens with anal fin counts lower than 22 rays. Randall (1968) had counts of III, 23-25 for P. arcuatus, Miller and Jorgenson's (1973) counts were III, 22-23. Johnson (1984) shows the anal fin count for the family Pomacanthidae as Ill-IV, 14-25; all these counts are within my range for P. arcuatus. Comparison of counts and placement of fins and fin supports between the genera of Atlantic Pomacanthids are very similar, causing difficulties with identification of larvae based on counts (Figs. 10, 16). The two species of Pomacanthus can easily be separated from the other two genera by predorsal bone count and 846 BULLETIN OF MARINE SCIENCE. VOL. 56. NO.3. 1995

1) £. paL!.!' 2) ~ • .ami:

DORSAL. FIN DORSAL FIIf BONES DORSAL FIU I DO~AL FIll , J r; ~ -f-r;-; ~ 66 , 5 , 5 5 6/4 ~'~ ...... -f--. ) J J J J !:]) J I- ;1J ljJ ) J];> 2!l , , , 1 , , , , , , , , , , · , 314 t , , , , , , , , , , , , · ~--; : , , , , I' c· ~ : ~-:-: : : ~,~ : : :-A~<-: : : : : : : --- , , , , , , 10111 , I' '" 14151 '" 1619 DC' 1 2 J 4 5 6 7 8r1-;-1011 ~u 14 15161718 192 B , , , , 1011 1'1' 1'1'1'· 12n 1415 l617 HIU 20 n 22 23 24 S 1 I 2 J 4 5 (; 7 Ie 19 ]10 11 12pJ 14 15 1G 17 18 19 20 JI12.m~ U, , D 14151 HlU · - '" DC' 11 12 It 14 1~'16 J7 18 19:2 a , , , , , , , , , , C , , , , , , , , , 1 1 ~ :2 :I :I :I :2 ] 1 C , , , , , , ,. J 1 :I :I :3 2 :I ~tl', . - .. . · ] 3 ] ] J ] ] ] ) J II ANAL FIN · AN,'U, PIN J._

NI!:OORSAL fIRST SECQltD !JONES DORSAL PIN DORSAL FIll - - - , , , , , , , , , , , , , , , , , 1 , , , , , , , , , , , , , , , , , , , -;- . · ~ , , 1 1 , , , ; , , , , , , , , , , C· 1 , , 5 , , .. 101112 1114 151,> 1118 , 5 , , , HI 11 121314 '" ~_1_:.J2 ·. 1516 1116 1920 ·:.u12212J!241· · U 12 1]14 1511 1716 19200 1 , , , , , ;-\~ , c , , , , , , , , . , , , , , , · ANAL FIH ·

DORSAl. PIN DORSA:" PIN -~IDC"~ I , , , , , , , , , -I , , , , , , , , , , , , , , 1 1 , , , , , , -;-~: 1112 · -f- , , , 1 , 1 1 , 1 , , , , , , . , , , , C· , , I, 5 , , , 1011 12ll . '" 5 H l1U '" 1 , , , , , , 112 13 14151 111 BI19 1'1 1 ' · " , 1 61 "1'*'1'*'1· · 111213 " , 1118 19 20 8 - '" , , , , , , , , 1 , C , . , , , , , , , , , , , , , , , , , .· ANAL FI" · Figure 16. Common arrangement of predorsal bones, pterygiophores, fin spines and rays in relation to the skull and vertebral column for 1) P. paru, 2) C. argi, 3) H. ciliaris. 4) H. bermudensis, 5) H. tricolor; Modified after Matsui (1967). A, skull and vertebrae numbers; B, interneural and interhaemal space numbers; C, number of pterygiophores in the respective interneural or interhaemal space; D, number of fin spines or rays associated with the pterygiophore; E, frequency of occurrence in 34 specimens for the pterygiophore number in the respective interneural or interhaemal spaces.

placement, but there is very little difference in associated counts to separate P. arcuatus and P. paru (Figs. 10, 16). Tn the first dorsal fin the only difference found is in the ninth interneural space, the pterygiophore supports a spine in P. paru and a ray in P. arcuatus. The second dorsal fin is similar, only two differences are observed in counts between the two species. My series of P. paru consisted of six specimens, three have the same counts as the majority of P. arcuatus, and three have a count which differs by one. The largest difference between the two species is anal fin placement counts, which differ in the 18th, 19th, and 20th interhaemal spaces (Figs. 10, 16). The three species of Holocanthus and one species of Centropyge examined are all easily differentiated from p, arcuatus by first dorsal fin counts and placement. All three species have only one predorsal bone in the first interneural space, 0 in the second interneural space, and the first dorsal-fins end in the 12th or 13th interneural space (Fig. 16), with a count of XIV compared to P. arcuatus which ends after the eighth interneural space and has a count of IX or X and has a predorsal bone in both first and second interneural spaces (Fig. 10). Counts in the second dorsal and anal fins of KELLEY: POMACANTHUS ARCUATUS DEVELOPMENT 847

Holacanthus sp. and Centropyge argi are also different enough to be used to differentiate from P. arcuatus (Figs. 10, 16).

ACKNOWLEDGMENTS

I wish to thank M. Moe for the laboratory-reared specimens used for this study, J. Javech for the illustrations of Figures 1-7 and Figures 11, 14 and ]5. W. J. Richards for his help and suggestions, and T. Potthoff whose guidance made this possible. My thanks to the reviewers for all their time and effort.

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DATE ACCEPTED: February 15, 1994.

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