<I>Microspathodon Chrysurus</I>

BULLETIN OF MARINE SCIENCE, 40(2): 330-375,1987 CORAL REEF PAPER

DESCRIPTION OF LARVAL AND JUVENILE YELLOWTAIL DAMSELFISH, MICROSPATHODON CHRYSURUS, POMACENTRIDAE, AND THEIR OSTEOLOGICAL DEVELOPMENT

Thomas Potthoff, Sharon Kelley, Vishnu Saksena, Martin Moe and Forrest Young

ABSTRACT Eggs were collected from nests of yellowtail damselfish, Microspathodon chrysurus. on a south Florida reef and hatched in the laboratory. Hatched larvae were reared, with some killed and preserved at time intervals. A series of 109 larvae and juveniles 2.0 mm NL-19.8 mm SL (3 to 79 days old) were measured for morphometric changes and examined for pigment development. Ninety of these laboratory-reared larvae (2.1 mm NL to 19.8 mm SL) and three wild-caught juvenile and adults (54.4 to 116 mm SL) were cleared and stained to study osteological development. Larvae of M. chrysurus can be distinguished from other known damselfish larvae by their large pigmented pectoral fin and by a number of large melanophores over the hind brain and on the dorsal and ventral tail margin. Re (1980) described early larvae of Abudefduf /uridus. which are strikingly similar to the larvae of M. chrysurus. Osteological development of the vertebral column and ribs, the paired and unpaired fins and their supports, the hyoid arch, the branchial skeleton and the opercular series were studied. Cartilaginous neural arches and spines first appeared anteriorly on the notochord; addition was in a posterior direction. Cartilaginous hypurals appeared before all neural and haemal arches and spines had developed. Notochord flexion started in a 3.7 mm NL 16-day-old larva. Pleural ribs first developed as cartilage and then ossified, whereas epipleural ribs originated directly from ossification of connective tissue. Four or five anterior haemal arches of the caudal centra supported epipleural ribs. The vertebral column ossified from anterior to posterior. The coracoid bone of the pectoral girdle had one or two foramina, a feature not observed in perciforms except pomacentrids. In M. chrysurus. the second dorsal and anal fins and supports probably started development before the first dorsal fin. There were three predorsal bones, and the first dorsal pterygiophore supported two fin spines. The first anal pterygiophore supported two spines and one ray. Middle radials were absent in the dorsal and anal fin supports, but one stay was associated with the posteriormost pterygiophore of both fins. In the caudal complex only one uroneural developed, which fused with the urostyle forming a neural canal. Principal caudal rays were 8+ 7 compared to the most common perciform count of9+8. The ceratohyal bone of the hyoid arch had the primitive beryciform foramen, and the fifth ceratobranchials fused during ontogeny forming the lower pharyngeal jaw. Recently, the pomacentrids have been removed from the percoids and placed with the labroids. Our findings support this placement because of the fused fifth ceratobranchials and the reduced principal caudal ray count.

The yellowtail damselfish Microspathodon chrysurus belongs to the large perciform family Pomacentridae. Recently, Kaufman and Liem (1982) removed the Pomacentridae from the suborder Percoidei and placed it in the suborder Labro- idei. This family has 4 subfamilies, about 25 genera and about 235 species (Allen, 1975; Nelson, 1984). Most damselfish species occur on reefs of the Indo-Pacific. Microspathodon (subfamily Pomacentrinae) has two other species, the giant blue damselfish, M. dorsalis, found in the eastern Pacific, and M. frontatus from the Gulf of Guinea (Emery, 1970). In the western Atlantic, M. chrysurus is a very common species on coral reefs and occurs from Bermuda, the Bahamas, Florida and the Gulf of Mexico across the Caribbean to the coast of South America, as

330 POTTHOFF ET AL.: M/CROSPATHODON LARVAL DEVELOPMENT 331

far as Brazil (Ciardelli, 1967; Bohlke and Chaplin, 1968; Randall, 1968). Juveniles of this species are commonly known as jewelfish and are of considerable value in the aquarium trade. The behavior, reproduction and ecology of damselfishes are well known (Reese, 1964; Breder and Rosen, 1966; Emery and Thresher, 1980; Sale, 1980). Fewer studies, however, have dealt with the description of the eggs and larvae of damselfishes and these are summarized by Leis and Rennis (1983), Thresher (1984) and Richards and Leis (1984). Leis and Rennis figured and described developmental series of about four genera. At present, only one comprehensive osteological study of one pomacen trid species (Lepidozygus tapeinosoma) exists (Emery, 1980). Another study by Emery (1973), which is not comprehensive and does not include M. chrysurus, treats the functional osteology of 14 species of damselfish. Emery and Allen (1980) examined the insertion sequence of predorsal bones and anterior pterygiophores in adults of 21 damselfish genera, including Microspa- thodon. Developmental osteology has not been examined within the family. There are a limited number of papers dealing with Microspathodon. Montgom- ery (1980) reported on the impact of grazing on algal communities by M. dorsalis, the giant blue damselfish. MacDonald (1973) and Pressley (1980) studied reproduction and behavior in M. chrysurus. Ciardelli (1967) studied food habits and the anatomy of the feeding mechanism in M. chrysurus. Cummings (1968) observed yellowtail damselfish behavior and measured 100 eggs, which averaged 1.1 mm in diameter. Emery (1973) studied yellowtail damsel fish ecology on a Florida reef. Richards and Leis (1984) presented a lateral view drawing ofa 3.7 mm NL flexion stage larva of M. chrysurus, which is a specimen used in this study. Moe and Young (1981) initially reported on the successful laboratory- rearing of yellowtail damselfish, and showed photographs of eggs, larvae and juveniles. In this study we describe the development of morphometrics and pigmentation of cartilaginous and bony structures and of the paired and unpaired fins. This information will aid identification of M. chrysurus larvae and future studies of labroid and percoid relationships.

MATERIALS AND METHODS

Nests of yellowtail damselfish eggs were collected from reefs of the Coffins Patch reef complex for experimental rearing on 28 and 29 August 1978 and 17 August 1981, 4 March and 8 June 1982. The nests were located by observing the territorial behavior of the damselfish and then searching the center of the indicated area. Nests were also easily found when spawning activity was intense by examining blades of fire coral, Millepora complanata, on the reef top in areas where numerous damsel fish were observed. The nests were almost always found on the flat sides of dead blades of fire coral and rarely on the more massive encrusting portions of fire coral growth. Collected nests varied in age from newly spawned to actively hatching. The incubation period from spawn to hatch was about 3 days. An effort was made to obtain nests that were close to hatching to shorten laboratory incubation. They were collected by carefully breaking off the dead blade of fire coral at the base. The collected nests were transported back to the hatchery in a bucket. The nests were maintained in the laboratory by suspending them above a vigorous air release and allowing the rising bubbles to rush past the developing eggs. Nests were successfully maintained from several hours to several days with this technique. Hatching usually occurred at night; however, eggs close to hatching would often hatch during the day if disturbed. Hatching and rearing of larvae were under identical conditions as described for Anisotremus virginicus by Potthoffet al. (1984). At 8 to 9 weeks of age the young yellowtail damselfish were transferred to 1,361 liter grow-out tanks supplied with a constant flow of filtered seawater. One hundred and nine larvae from 2.0 mm NL to 19.8 mm SL were preserved in 5% Formalin,' 3,4,6,8,9,11, 12, 13, 16, 18,25,29,33,34,50 and 79 days after hatching; three wild-caught specimens 54.4, 114 and 116 mm SL were also used in this study. Four laboratory-reared specimens

I Mention of any product in this paper docs not imply endorsement by the National Marine Fisheries Service, NOAA. 332 BULLETIN OF MARINE SCIENCE, VOL. 40, NO.2, ]987

10.5-10.7 mm SL (50 days) were used in the morphometric section only. Fifteen of the laboratory- reared specimens (2.0-3.3 mm NL, 3 to 6 days old) were used for pigment and morphometric descriptions only; the remaining 96 specimens were used for pigment and osteological descriptions. The preserved larvae hatched in 1978 were examined by us three years later in 1981. The larvae hatched in 1982 were examined about three months after preservation. No specimens were preserved between 4.5 (18 days) and 7.3 mm SL (25 days). We found that this represented a critical gap for which developmental data were not available. The following measurements were made on M. chrysurus larvae and juveniles. Notochord length (NL): Tip of snout to tip of notochord before and during notochord flexion. Standard length (SL): Tip of snout to distal margins of hypurals after notochord flexion. Body depth: Vertical height of body measured at transverse level of pectoral-fin origin. Snout length: Tip of snout to anterior margin of eye. Eye diameter: Horizontal distance between anterior and posterior edges of fleshy orbit. Predorsal length: Distance along midline from tip of snout to origin of spinous dorsal fin. Preanus length: Distance along midline from tip of snout to anus. In clearing and staining we followed the method ofPotthoff(1984). Most drawings were made using a camera lucida. For the caudal complex we used a composite terminology following Gosline (1961 a; 1961b), Nybelin (1963) and Monod (1968). For the terminology of the branchial and hyoid arches we followed McAllister (1968), Nelson (1967; 1969) and Rosen (1973).

PIGMENTATION Figures 1-6, Table 1 Pigmentation of Formalin preserved larvae is described here. Head Region. -All M. chrysurus larvae of 2.0 mm NL (4 days) and larger had pigmented eyes and scattered pigmentation on the midbrain. At 2.1-2.8 mm NL (3-11 days) larvae developed one or two large melanophores above the hindbrain and these expanded anteriorly and posteriorly to cover the midbrain and nape. Forebrain pigment was first present in some larvae at 4.0 mm SL (18 days) and all had it at 9.2 mm SL (29 days). Upper jaw pigmentation was present in specimens 17.5 mm SL (79 days) and larger. Pigment appeared on the lower jaw and angle at 10.9 mm SL (50 days). Some specimens developed melanophores on the isthmus at 3.7 mm NL (16 days) and all had acquired some by 9.8 mm SL (33 days). Pigment developed on the pectoral symphysis at 9.8 mm SL (33 days) and on the gular membrane at 19.8 mm SL (79 days). Melanophore density greatly increased in the head region in specimens of 10.7 mm SL (50 days). Gut and Tail Region. -In our smallest specimen 2.0 mm NL (4 days) melanophores were already present dorsally and ventrally on the gut. By 10.9 mm SL (50 days) melanophores had spread laterad, densely covering the entire gut. The "tail region" is the area on the body of a fish larva directly posterior to the anus and including the caudal fin. For convenience we have subdivided the tail region by adding "caudal region," which includes the hypural complex and the caudal fin. Small larvae of2.0 mm NL (4 days) and larger had a large melanophore ventrally and dorsally at the center of the tail. These melanophores had migrated to areas just below and above the lateral midline in specimens 3.7-4.4 mm SL (16-18 days). Additionally, 5-9 smaller melanophores (not counting caudal fin melanophores) were present along the ventral tail margin on each side of the anal finfold. These melanophores became internal pigment in the 3.7 mm NL flexion larva. Melanophores first appeared along the dorsal tail margin at 4.0 mm SL (18 days) on each side of the second dorsal fin. The dorsal and ventral pigments spread ventrad and dorsad until the entire tail region was covered with melanophores at 10.9 mm SL (50 days). Caudal Region. - Preflexion larvae of 2.0-3.6 mm NL (3-16 days) had 5-7 small POTTHOFF ET AL.: M1CROSPATHODON LARVAL DEVELOPMENT 333

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Figure I. Microspathodon chrysurus preflexion larva 2.4 mm NL, I day old, laboratory-reared. Top: left lateral view; center: dorsal view; bottom: ventral view. melanophores directly below the notochord and 1-5 small melanophores in the caudal finfold below the notochord. After flexion, larvae from 3.7-4.5 mm SL (16-18 days) had 11-17 melanophores on the caudal fin rays, most being on the lower lobe. In specimens larger than 9.2 mm SL (29 days) caudal fin pigmentation disappeared but reappeared mostly at the caudal ray tips at 19.8 mm SL. Dorsal and Anal Fins. -Melanophores on the membrane of the first dorsal fin occurred first in 4.4 mm SL (18 days) M. chrysurus, and specimens larger than 9.2 mm SL (29 days) had first dorsal fin pigmentation. Pigmentation of the fin membrane in the second dorsal fin started between 9.2 mm SL (29 days) and 17.5 mm SL (79 days). All specimens 9.2 mm SL (29 days) and larger developed melanophores on the anal fin membrane. Progression of pigment development on the dorsal and anal fin membranes was from the fin base distad and usually from anterior to posterior. Pectoral and Pelvic Fins. - The pectoral finfold in the 2.0 mm NL (4 days) larvae had a row of pigment streaks near the distal edge. Pigmentation increased proximad until by 4.0 mm SL (18 days) the largest part of the pectoral fin membrane was covered with melanophores. Pelvic fin pigmentation was absent in smaller larvae. Our 9.2 mm SL (29 days) specimen had two melanophores on each pelvic-fin membrane. The entire pelvic fin was pigmented at 10.7 mm SL (50 days).

MORPHOMETRIes Table 2 Before notochord flexion (2.0-2.5 mm NL), body depth was about 20% NL but increased to more than 50% SL in larvae longer than 7.0 mm SL. Snout length among all larvae was rather constant and ranged between 7 and 13% NL or SL. Eye diameter was 9 to 12% NL or SL in larvae up to 2.5 mm NL and increased to 18% SL in longer larvae. Predorsallength in all larvae between 3.7 and 12.5 334 BULLETIN OF MARINE SCIENCE, VOL. 40, NO.2, 1987

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Figure 2. Microspathodon chrysurus late flexion larva 3.7 mm NL, 16 days old, laboratory-reared. Top: left lateral view; center: dorsal view; bottom: ventral view.

mm SL did not vary much and was 42 to 54% SL. Preanus length averaged around 33% NL in smaller larvae (2.0-2.5 mm NL); a sharp increase in the preanus length occurred as larvae grew, approaching 67% SL for larvae of 11.0 mm SL; in larvae longer than 11.0 mm SL, the preanus length was slightly reduced and averaged about 63% SL.

OSTEOLOGICAL DEVELOPMENT Vertebral Column (Figs. 7-10, Table 3).-M. chrysurus has 26 vertebrae, II are precaudal and IS are caudal. The first anal pterygiophore can be used to separate precaudal from caudal vertebrae; this pterygiophore is just anterior to the first haemal spine of the anteriormost caudal centrum. Our early specimens of M. chrysurus, 2.1-2.9 mm NL (3-12 days), had no neural or haemal spine development on the straight notochord. One or two cartilaginous neural arches were seen anteriorly behind the head above the notochord in the three 3.1 mm NL (12, 13 days) specimens. Three or four cartilaginous neural arches were present anteriorly in specimens 3.2-3.4 mm NL (6, 13 days). POTIHOFF ET AL.: MICROSPATHODON LARVAL DEVELOPMENT 335

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Figure 3. Microspalhodon chrysurus postflexion larva 4.4 mm SL, 18 days old, laboratory-reared. Top: left lateral view; center: dorsal view; bottom: ventral view.

The next larger specimen of 3.6 mm NL (16 days) had most neural and haemal arches and spines developed except the three or four posteriormost of each series. All neural and haemal arches and spines were present as cartilage in 3.7 mm NL (16 days) specimens. The direction of neural and haemal arch formation could not be determined due to lack of intermediate specimens of 3.5 mm NL (14 or 15 days) (see discussion). Ossification of the vertebral column was first evident as a thin hyaline layer around the notochord in the 3.6 mm NL (16 days) specimen. In the 3.7 mm NL (16 days) flexion specimen the first eight vertebrae were fully ossified and segregated. The 9th to the 14th centra had ossifications only near the bases of the cartilaginous neural and haemal arches. The remainder of the vertebral column had no ossifications except for the hyaline layer around the notochord. Ossification of the vertebral column proceeded in a posterior direction; all centra were fully ossified and segregated by 4.5 mm SL (18 days). Ossification of the neural and haemal arches and spines also proceeded from anterior to posterior, except the parapophyses developed and ossified in the reverse direction, starting 336 BULLETIN OF MARINE SCIENCE, vOL. 40, NO.2, 1987

Figure 4. Microspathodon chrysurus postfiexion larva 9.2 mm SL, 29 days old, laboratory-reared. Top: left lateral view; center: dorsal view; bottom: ventral view.

on the 11th centrum. Ossification of individual arches and spines started at the base of the cartilaginous arch and proceeded distad toward and along the cartilaginous spine. Usually the appearance of bony flagellum like tips on the distal ends of the cartilaginous neural and haemal spines is observed during development in perciform fishes (Potthoff, 1975; Potthoff et al., 1980; Potthoff et al., 1984). In M. chrysurus these tips were observed during early development in 18-day-old POTTHOFF ET AL.: M1CROSPATHODON LARVAL DEVELOPMENT 337

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Figure 5. Microspathodon chrysurus late postflexion larva 10.9 mm SL, 50 days old, laboratory- reared. Top: left lateral view; center: dorsal view; bottom: ventral view.

larvae only on neural spines of vertebrae 5-7. All other neural and haemal spines posterior to the 7th centrum developed bony tips late when the specimens were 50 days old and the neural and haemal spines were fully ossified. Neural prezygapophyses developed on all neural arches of the 26 centra. On the two anteriormost vertebrae, the epipleural ribs articulated with the prezygapophyses. The 'neural prezygapophyses on some of the centra were blunt and rounded and not well defined. Neural postzygapophyses developed either on centra 5, 6, 7, 8, 9 or 10 to centrum 22 or 23. On some vertebrae the neural postzygapophyses were blunt and rounded. Parapophyses were present on centra 3 to 11 and served for rib articulation. The parapophyses on centra 3 and 4 were laterally directed whereas the parapophyses on centra 5 to 11 were directed ventrally. Haemal prezygapophyses developed on centra 12 or 13 to 23. The first closed haemal arch was found 41 times on the 7th centrum and four times on the 6th centrum in specimens 3.7 to 17.5 mm SL. In our three adult specimens, 54.5-116 mm SL, the first closed haemal arch occurred once on the 9th and twice on the 8th vertebra. 338 BULLETIN OF MARINE SCIENCE, VOL. 40, NO, 2, 1987

Figure 6, Microspathodon chrysurus juvenile 19,8 mm SL, 79 days old, laboratory-reared. Left lateral view.

Epipleural and Pleural Ribs (Figs. 8, 10, Table 3).-Epipleura1 and pleural ribs started to develop in a 4.5 mm SL (18 days) specimen anteriorly on the vertebral column. Addition of rib pairs was in a posterior direction. The epip1eural ribs developed on vertebrae 1 to 15 or 16 and the pleural ribs on vertebrae 3 to 11. The maximum adult count of 15 or 16 epipleural rib pairs was attained between

Table I. Lengths and days after hatching at which melanophores developed in 71 laboratory-reared Microspathodon chrysurus (2.0 mm NL-19.8 mm SL). First: appearance of melanophores in some specimens of indicated size or age. All: melanophores present in all specimens of indicated size or age

Lengths mm NL or SL Days afier hatching

First All First All

Forebrain 4.0 9.2 18 29 Midbrain 2.0 2.0 4 4 Hindbrain 2.1 2.8 4 11 Tip and ramus upper jaw 17.5 17.5 79 79 tip and ramus lower jaw 10.9 10.9 50 50 Angle of jaw 10.9 10.9 50 50 Gular membrane 19.8 19.8 79 79 Around eye 2.5 3.7 9 16 Dorsal margin (nape to peduncle) 2.0 2.0 4 4 Ventral margin (vent to peduncle) 2.0 2.0 4 4 Gut (dorsal and ventral surface) 2.0 2.0 4 4 Isthmus 3.7 9.8 16 33 Pectoral symphysis 9.8 9.8 33 33 First dorsal fin 4.4 9.2 18 29 Second dorsal fin 9.2 17.5 29 29 Anal fin 9.2 9.2 29 29 Caudal fin-lower 2.0 2.0* 4 4* Caudal fin-upper 3.6 4.0* 16 18* Pectoral fin 2.0 2.0 4 4 Pelvic fin 9.2 9.2 29 29

• Caudal fin pigmentation disappeared in specimens larger than 9.2 mm SL (29 days). but reappeared at 19.8 mm SL (79 days). Table 2. Summary of morphometric data of laboratory-reared larvae and early juveniles of Micro- spathodon chrysurus. Notochord and standard lengths are in mm and the remaining measurements are proportional values relative to notochord (prellexion and Ilexion specimens) or standard lengths (postllexion specimens). Specimen between dotted lines is undergoing notochord Ilexion

Days after Notochord or hatching standard length Body depth Snout length Eye diameter Predorsallength Preanus length 6 2.0 0.22 0.07 0.09 0.34 6 2.2 0.21 0.09 0.12 0.34 6 2.2 0.21 0.10 0.09 0.34 6 2.3 0.20 0.07 0.11 0.33 6 2.3 0.15 0.05 0.10 0.33 6 2.4 0.21 0.06 0.12 0.33 9 2.5 0.17 0.08 0.10 0.33 9 2.5 0.21 0.08 0.11 0.33 ...... •...... --...... 16 3.7 0.38 0.13 0.15 0.54 0.62 ...... •...... 16 4.0 0.36 0.11 0.14 0.42 0.50 16 4.0 0.39 0.12 0.15 0.42 0.54 16 4.0 0.41 0.13 0.15 0.49 0.50 18 4.0 0.40 0.12 0.15 0.44 0.57 18 4.4 0.40 0.17 0.14 0.42 0.51 18 4.5 0.41 0.13 0.14 0.44 0.57 18 4.5 0.42 0.15 0.15 0.47 0.57 25 7.3 0.51 0.14 0.15 0.42 0.59 29 9.2 0.55 0.10 0.14 0.42 0.59 34 9.5 0.56 0.11 0.16 0.48 0.66 33 9.8 0.54 0.07 0.15 0.41 0.64 50 10.3 0.53 0.10 0.17 0.45 0.68 50 10.5 0.55 0.10 0.17 0.51 0.64 50 10.6 0.58 0.12 0.17 0.48 0.62 50 10.6 0.58 0.10 0.18 0.47 0.66 50 10.7 0.55 0.11 0.17 0.48 0.65 50 10.7 0.58 0.11 0.17 0.50 0.65 50 10.7 0.56 0.09 0.16 0.47 0.65 50 10.7 0.56 0.10 0.17 0.47 0.65 50 10.7 0.56 0.10 0.18 0.47 0.65 50 11.1 0.51 0.09 0.17 0.45 0.67 50 11.2 0.53 0.12 0.16 0.46 0.67 50 11.2 0.58 0.10 0.18 0.45 0.66 50 11.2 0.54 0.10 0.17 0.46 0.66 50 11.2 0.54 0.11 0.16 0.49 0.64 50 11.3 0.54 0.11 0.17 0.46 0.65 50 11.4 0.56 0.10 0.16 0.46 0.65 50 11.4 0.56 0.09 0.17 0.46 0.64 50 11.4 0.57 0.10 0.17 0.49 0.64 50 11.5 0.55 0.08 0.16 0.43 0.64 50 11.5 0.54 0.09 0.15 0.49 0.65 50 11.5 0.55 0.11 0.16 0.47 0.63 50 11.6 0.56 0.09 0.16 0.47 0.63 50 11.7 0.55 0.12 0.16 0.46 0.62 50 11.7 0.57 0.11 0.16 0.46 0.63 50 11.7 0.52 0.09 0.16 0.44 0.61 50 11.7 0.55 0.08 0.16 0.46 0.62 50 11.8 0.57 0.10 0.17 0.45 0.63 50 11.9 0.55 0.11 0.15 0.48 0.64 50 11.9 0.56 0.08 0.16 0.45 0.63 50 11.9 0.54 0.09 0.16 0.45 0.63 50 11.9 0.56 0.09 0.16 0.44 0.61 50 12.0 0.55 0.11 0.16 0.46 0.62 50 12.0 0.55 0.09 0.16 0.45 0.62 50 12.0 0.55 0.10 0.17 0.46 0.62 50 12.2 0.55 0.11 0.15 0.46 0.62 50 12.3 0.57 0.10 0.16 0.45 0.60 50 12.5 0.53 0.09 0.14 0.46 0.59 50 12.5 0.55 0.10 0.15 0.45 0.61 340 BULLETIN OF MARINE SCIENCE, VOL. 40, NO.2, 1987

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Figure 7. Semi-schematic representation of fin ray, fin support and vertebral column development in laboratory-reared Microspathodon chrysurus. Scale represents vertebra and interneural and interhaemal space numbers. Cartilage, white; ossifying, stippled.

9.2 mm SL (29 days) and 12.5 mm SL (50 days). The maximum adult count of nine pleural rib pairs was attained between 7.3 mm SL (25 days) and 9.2 mm SL (29 days). Epipleural ribs developed in the connective tissue of the myosepta directly as bone. First, a small piece of bone developed near the distal portion of the future epipleural rib. Then bone developed proximad toward the rib articulation point and a small amount was added distally near the tip of the rib. Pleural ribs developed from cartilage first and afterwards ossified. Pleural ribs articulated POTTHOFF ET AL.: MICROSPATHODON LARVAL DEVELOPMENT 341

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>----i 1mm Figure 8. Ontogeny of 5th precaudal centrum from 5 laboratory-reared and one wild-caught Mi- crospathodon chrysurus. left lateral view. Top left to bottom right specimens' lengths in mm NL or SL were: 3.6,4.5,7.3, 11.5, 17.5, 116. C, centrum; EPI, epipleural rib; NPo, neural postzygapophysis; NPr, neural prezygapophysis; Ns, neural spine; Pa, parapophysis; PI, pleural rib. Cartilage, white; ossifying, stippled. with laterally directed parapophyses at the bases of neural arches of centra 3 and 4 and with ventrally directed parapophyses on centra 5 to 11. Epipleural ribs on centra 1 and 2 articulated on the neural arches. On centra 3 to 11, epipleural ribs articulated with parapophyses just dorsal to the pleural ribs. On centra 12 to 15 or 16, epipleural ribs articulated with the haemal arches. In 27 out of 39 M. 342 BULLETIN OF MARINE SCIENCE, VOL. 40, NO.2, 1987

Figure 9. Views of two centra from an adult wild-caught 114 mm SL Microspathodon chrysurus, From left to right: left lateral view and anterior view of 7th precaudal centrum, left lateral view and anterior view of 8th precaudal centrum. Ha, first haemal arch. For other abbreviations, see Figure 8, chrysurus of 10.7-116 mm SL the last epipleural rib pair articulated with the 16th vertebra (5th caudal) and in 11 specimens the last rib pair articulated with the 15th vertebra (4th caudal). One specimen had a single rib on the left side on the 16th vertebra. Caudal Fin (Fig. 11, Table 4).-Caudal fin rays were first observed ventral to the notochord in a 3.7 mm NL (16 days) preflexion larva with a count of 2/3 principal caudal rays. The rays developed from a center caudad and rostrad between hypurals 2 and 3. The full count of 8+7 principal caudal rays was present in a 3.7 mm NL (16 days) flexion larva. Dorsal and ventral secondary caudal rays were first seen at 4.0 mm SL (16-18 days) and the full count of five upper and five lower secondary rays was attained by 7.3 mm SL (25 days). A procurrent spur (Johnson, 1975) was not present. Caudal Fin Supports (Figs. 11, 12, Tables 6, 7).- The adult caudal complex had the following bones: a preural centrum 3 with an autogenous haemal and a non- autogenous neural spine, the neural spine not supporting rays; a preural centrum 2 with an autogenous haemal spine, a specialized neural arch and three epurals above the arch; a urostyle fused with one uroneural, forming a neural canal; the urostyle supporting five autogenous hypurals and a parhypural, the latter sometimes fused distally with hypurall. In addition, six radial cartilages were associated with the hypural complex; one was directly anterior to the haemal spine of PU J, one anterior to the haemal spine of PU 2, two anterior to the parhypural, one dorsal to hypural 5 and one anterior to the neural spine of PU J. A long, slender posteriorly directed parhypurapophysis was present on the parhypural. Short hyp-

-l Figure 10. Ontogeny of the 15th centrum (4th caudal) from 5 laboratory-reared and one wild-caught Microspathodon chrysurus, left lateral view. Top left to bottom right specimens' lengths in mm NL or SL were: 3.6, 4.5,7,3,10,7,17.5,54.4. HPo, haemal postzygapophysis. For other abbreviations, see Figure 8, POTTHOFF ET AL.: MICROSPATHODON LARVAL DEVELOPMENT 343

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Figure II. Ontogeny ofhypural complex from 5 laboratory-reared and I wild-caught Microspathodon chrysurus, left lateral view. Top left to bottom right specimens' lengths in mm NL or SL were: 3.6, 4.0, 7.3, 11.2, 19.8, 116. Ep, epural; HPr, haemal prezygapophysis; Hs, haemal spine; Hy, hypural; uNa", specialized neural arch; NC, notochord; NPr, neural prezygapophysis; Ns, neural spine; PCR, principal caudal rays; Ph, parhypural; Pu, preural centrum; RC, radial cartilage; SCR, secondary caudal rays; Un, uroneural; Ur, urostyle. Cartilage, white; ossifying, stippled. POTTHOFF ET AL.: MICROSPATHODON LARVAL DEVELOPMENT 347 urapophyses were present on hypurals I and 2 on the anterior proximal surface; hypurals 3, 4 and 5 lacked hypurapophyses. The caudal fin rays of M. chrysurus were supported by some of the bones of the caudal complex with three vertebrae involved in the support. Ventrally caudal rays were supported by hypurals, the parhypural and the autogenous haemal spines of the urostyle and preural centra 2 and 3. Dorsally all caudal rays were supported by hypurals and epurals of the urostyle and preural centrum 2. The 8+7 principal caudal rays were supported by five hypurals and one parhypural. The number of principal caudal rays articulating with the individual hypural bones was remark- ably constant. The only variability occurred on hypurals 1 and 2 where it varied by one ray only. A secondary caudal ray articulated with hypural5 in all specimens. Preflexion M. chrysurus larvae of 2.1-3.2 mm NL (3-13 days) had no hypural development except a caudal finfold and a straight notochord. Preflexion larvae of 3.3 and 3.4 mm NL (13 days) had a cartilaginous parhypural and hypural 1. Preflexion larvae of 3.6 mm NL (16 days) had added hypurals 2 and 3. The 3.7 mm NL (16 days) preflexion specimen had added hypural 4, cartilaginous haemal spines of PU 2 and PU 3 and three small cartilaginous epurals dorsal to the notochord. The cartilaginous hypural 5 first appeared in a 4.0 mm SL (18 days) M. chrysurus. but the uroneural developed between 4.4 and 7.3 mm SL (18-25 days). We were unable to determine the pattern of ossification of the hypural complex because oflack of specimens between 4.4 and 7.3 mm SL (18-25 days). All bones were ossifying in the 7.3 mm SL (25 days) specimen. The only adult fusion in the hypural complex that we observed were the uroneural with the urostyle and sometimes the distal part of the parhypural with hypural 1. Pectoral Fin and Supports (Fig. 13, Tables 4, 5).-Our smallest larvae, 2.1-2.4 mm NL (3 or 4 days), already had larval pectoral fins, consisting of a semicircular cartilaginous blade surrounded by a finfold. The pectoral finfold contained finray precursors or actinotrichia. Just before and during notochord flexion at 3.7 mm NL (16 days), pectoral fin rays developed dorsally in the finfold. Initial fin ray development was evidenced by bunching (accumulation) of actinotrichia at the fin ray site. Pectoral fin rays were added in a ventral direction. The adult count of20-23 pectoral fin rays was first observed in the 7.3 mm SL (25 days) specimen. Emery (1970) observed 20-24 pectoral fin rays in adult M. chrysurus. All specimens 9.2 mm SL (29 days) and larger had the adult count. Fin ray counts between left and right pectoral fins often differed, but never by more than one fin ray. The adult pectoral girdle and suspensorium of M. chrysurus had the following bones on the left and right sides: three supratemporal-intertemporals, one posttemporal, one supracleithrum, one cleithrum, two postcleithra, one scapula, one coracoid and four proximal radials. Each pectoral fin ray had a cartilaginous distal radial between the two halves of its bifurcate base. The distal radials in our largest specimen (116 mm SL) had specks of ossifications on their surfaces. The supratemporal-intertemporal and posttemporal bones accommodated part of the laterosensory canal. The ventral most supratemporal-intertemporal bone was present in postlarvae and juveniles to 19.8 mm SL (79 days), but we were unable to locate the bone in our three adult specimens. We are uncertain whether the bone was lost during clearing and staining or dissection or if it had fused to the posttemporal during development. The bony cleithrum, the coraco-scapular cartilage and the cartilaginous fin blade were present in our smallest, 2.1-2.5 mm NL (3,4 days), specimens. The cleithrum, first long and rod-shaped, developed a large shelfposterodorsal and a smaller interior shelf posteroventral. The coraco-scapular cartilage first had long dorsal 348 BULLETIN OF MARINE SCIENCE. VOL. 40, NO.2, 1987

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Figure 12, Urosty]e, uroneural, 5 hypura]s and parhypura] from a wild-caught Microspalhodon chrysurus 1]6 mm SL. To left is an anterior view of urostyle with fused uroneural and neural canal. To right is a left lateral view of urostyle with fused uroneura] and disarticulated 5 hypural bones and 1 parhypural. N, neural canal. For other abbreviations, see Figure 11. and posterior processes and a short anterior process. The dorsal process acquired a foramen at 3.1 mm NL (13 days), then it broadened anteriorly and posteriorly and ossified into the scapula. The short anterior process of the coraco-scapular cartilage lengthened during development and ossified to the long anterior process of the coracoid. The long posterior process of the coraco-scapular cartilage short- ened during development and ossified to the posterior process of the coracoid. A ventrally located coracoid foramen was first present in the coraco-scapular cartilage at 2.4 mm NL (6 days) about halfway between the anterior and posterior processes. The relative shortening and lengthening of the two coracoid processes contributed to the posterior position of this foramen in adults compared to its central position in larvae. Our three adult M, chrysurus (54.4, 114, 116 mm SL) had two foramina on the coracoid bone. We did not witness the development of the more anteriorly located coracoid foramen. It was present in the three wild- caught adults, but absent in our laboratory-reared specimens including the largest, 19.8 mm SL (79 days), specimen. The cartilaginous blade that gave rise to the four proximal pectoral fin radials was observed in our smallest, 2.1-2.5 mm NL (3, 4 days), specimens. In some of these specimens, a narrow, oblong, lightly POTIHOFF IT AL.: MICROSPATHODON LARVAL DEVELOPMENT 351

Table 5. Development of the supporting bones and fin rays of the pelvic and pectoral fins in 50 laboratory-reared Microspathodon chrysurus 2.1 mm NL-7.3 mm SL (3-25 days old)

Lenglh and age al firsl appearance in cartilage, Length and age at first evidence of Pan mm NL or SL, days ossification, mm NL or SL, days Cleithrum <2.1, <4 Coraco-scapular cartilage <2.1, <4 Coracoid foramen 2.4,6 Scapular foramen 3.1,13 Scapula 4.0,18 Coracoid 4.0,18 Proximal radials First 3.7,16 4.5,18 Fourth 4.4, 18 >4.5 <7.3, > 18 <25 Distal radials First 3.7,16 Last 7.3,25 Supratemporal-intertemporal >4.5 <7.3, > 18 <25 Posttemporal 3.7,16 Supracleithrum 3.7,16 Postcleithra 1, 2 2.8,11 Pectoral fin rays 3.7,16 Basipterygium 3.7,16 4.0,18 Pelvic fin rays 4.0,16 stained area was present at the center of the base of the blade; in other specimens of the same size this area had already developed into a cleavage. Next another cleavage developed dorsal followed by one ventral to the middle cleavage in the same manner as described before. The cleavages elongated during development, reaching the distal margin of the blade and thereby separating the blade into the proximal radials. First to separate were the two dorsal proximal radials followed by the two ventral radials. A cartilaginous distal radial developed with each pectoral fin ray. Three supratemporal-intertemporal bones of dermal origin developed in M. chrysurus between 4.5 and 7.3 mm SL (18 and 25 days), a size range for which we did not have any specimens. These bones were tubular and accommodated part of the laterosensory canal connecting to the posttemporal and supracleithrum. We were unable to see the ventral most supratemporal.intertemporal bone in our three largest wild-caught specimens. The dermal posttemporal and supracleithrum were first observed at 3.7 rom NL (16 days). Originally these two bones were

Table 6. Distribution of caudal rays on the hypural bones in 40 laboratory-reared Microspathodon chrysurus (7.3-19.8 mm SL) larvae and juveniles and in three wild-caught adults (54.4-116.5 mm SL). One half of a principal caudal ray often articulated with hypural 2, the other half with hypural I

Number of principal caudal rays

o 1/2 4 5 1/2 6 Hypural5 43* Hypural4 43 Hypural3 43 Hypural2 28 14 Hypurall 14 28 Parhypural 43

• A secondary caudal ray aniculated with hypural 5 in all 43 specimens. 352 BULLETIN OF MARINE SCIENCE, VOL. 40, NO.2, 1987

Table 7. Acquisition of cartilage and ossification of various parts in the caudal complex oflaboratory- reared Microspathodon chrysurus

Length (mm NL or SL) of first Length (mm NL or SL) of first Part appearance in cartilage evidence of ossification PU3 centrum 4.0 Neural spine (PU3) 3.7 >4.4 <7.3 PU2 centrum 4.0 Specialized neural arch (PU2) 3.7 >4.4 <7.3 Epurals 3.7 >4.4 <7.3 Uroneural >4.4 <7.3 Hypural5 4.0 >4.4 <7.3 Hypural4 3.7 >4.4 <7.3 Hypural3 3.6 >4.4 <7.3 Hypural2 3.6 >4.4 <7.3 Hypurall 3.3,3.4 >4.4 <7.3 Parhypural 3.3,3.4 >4.4 <7.3 Urostyle 4.0 Haemal spine (PU) 3.7 >4.4 <7.3 Haemal spine (PU3) 3.7 >4.4 <7.3 Radial cartilage (dorsal) >4.0 <7.3 Radial cartilage (ventral) 4.0 narrow and elongate. By 4.5 mm SL (18 days) the posttemporal had assumed a characteristic inverted "C" shape by developing an antero-ventral process; by 7.3 mm SL (25 days) it had broadened considerably. The suprac1eithrum developed a posteriorly directed process by 4.5 mm SL (18 days) and also assumed a broad shape. The posterior process of the suprac1eithrum then became smaller during development and disappeared by 17.5 mm SL (79 days), but the broad shape of the bone was retained in the adults. The two postc1eithra were of dermal origin and were first observed at 2.8 mm NL (11 days) as thin elongated slivers. At 4.5 mm SL (18 days) the postc1eithra were still thin and elongated, but at 7.3 mm SL (25 days) postcleithrum I had developed a large bony plate dorso-posteriorly. Postcleithrum 2 remained thin and elongated. Pelvic Fin and Supports (Figs. 13-15, Tables 4, 5).-Rayless pelvic fin buds (blades) were first observed in the 3.7 mm SL (16 days) flexion stage M. chrysurus. In one ofthe 4.0 mm SL (16 days) specimens a 1,1 pelvic fin ray count was observed for the first time on the lateral edge of the pelvic fin buds. The pelvic fin rays were then added medially. The adult pelvic fin count of 1,5 for each side was attained between 4.5-7.3 mm SL (18 to 25 days). Cartilaginous basipterygia first appeared at 3.7 mm NL (16 days), together with the first appearance of the fin buds (blades). Ossification of the basipterygia was first observed in the 4.0 mm SL (18 days) larva. The cartilaginous basipterygia at first resembled two pterygiophores, i.e., cartilaginous rods with expanded bases. During ossification of the cartilaginous rods, anterior xiphoid processes developed, followed by the posterior xiphoid processes. The basipterygia each then developed four wings around the central part. First Dorsal Fin (Figs. 7, 16-18, Table 4).- First dorsal fin spines were first observed in 4.0 mm SL (16 and 18 days) specimens, which had already developed all second dorsal fin rays. In the 3.7 mm NL (16 days) flexion larva the first dorsal fin area was damaged. Although first dorsal fin pterygiophores were present in this specimen, no determination could be made as to the development of first dorsal fin spines. Development of first dorsal fin spines was caudad and rostrad POTTHOFF ET AL.: MICROSPATHODON LARVAL DEVELOPMENT 353

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Figure 13. Ontogeny of pectoral girdle from 5 laboratory-reared and I wild-caught Microspathodon chrysurus. left lateral external view. Top left to bottom right specimens' lengths in mm NL or SL were: 2.4, 3.7, 4.5, 7.3, 17.5, 116. A, anterior process of coraco-scapular cartilage; BI, cartilaginous blade; CI, cleithrum; Cor, coracoid; CorF, coracoid foramen; D, dorsal process of coraco-scapular cartilage; Fnfld, finfold; P, posterior process of coraco-scapular cartilage; Pelv, pelvic basipterygium; PstCI, postcleithrum; Pt, posttemporal; r, distal radial; R, proximal radial; Sc, scapula; ScF, scapular foramen; SCI, supracleithrum; St, supratemporal-intertemporal; ?, we were unable to locate one supratemporal-intertemporal bone in the adult. Cartilage, white; ossifying, stippled. from a central area. When fin spines first appeared they resembled rays and had frayed tips, but these tips soon became pointed. At 4.0 mm SL (16 days) the first dorsal fin was almost complete. Specimens 7.3 mm SL (25 days) and larger had 12 first dorsal fin spines except one 11.3 mm SL (50 days) specimen, which had 13 spines. First dorsal fin spines had closed bases, forming a foramen at the center of the base. 354 BULLETIN OF MARINE SCIENCE, VOL. 40, NO.2, 1987 _,~~~~~1~~~i~I~~

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Figure IS. Internal lateral view of left basi pterygium from an adult wild-caught Microspathodon chrysurus 54.4 mm SL. EVW, external ventrolateral wing; VW, ventral wing. For other abbreviations, see Figure 14.

First Dorsal Fin Supports (Figs. 7, 16-18).-No pterygiophores were seen in preflexion larvae of M. chrysurus, but all first dorsal fin pterygiophores and the three predorsals were present in cartilage in the 3.7 mm NL (16 days) flexion larva and in two ofthe 4.0 mm SL (16 and 18 days) postflexion larvae. The other 4.0 mm SL (16 days) postflexion larva had all first dorsal fin pterygiophores developed in cartilage, but only one predorsal cartilage was developed in interneural space number 3. Ossification of first dorsal fin pterygiophores was first observed at 4.5 mm SL (18 days), but at this length the predorsals were still cartilaginous. At 7.3 mm SL (25 days) the predorsal bones and first dorsal fin pterygiophores were all ossified. Each pterygiophore and predorsa1 bone originated from one piece of cartilage, including the anteriormost pterygiophore. After fin spine formation, a distal piece of cartilage separated near the base of the fin spine from the proximal cartilage. The proximal radials ossified before the distal radials and for both ossification proceeded caudad from the anteriormost radial. During ontogeny, lateral and sagittal keels developed on the proximal radials, and the distal radials developed a number of posteriorly pointing spines. These spines interlocked with the fin spines, increasing the strength and flexibility of the first dorsal fin. Each pterygiophore supported one fin spine in a serial association. The anteriormost pterygiophore had one supernumerary and one serially associated spine. The supernumerary spine lacked an autogenous distal radial. Instead, the spine was locked to the proximal radial by a ring of bone. Second Dorsal Fin (Figs. 18-20, Table 4).-Adult M. chrysurus second dorsal fin ray count is 14 or 15 rays. In the 3.7 mm NL (16 days) flexion larva, some second dorsal fin rays developed at the center of the fin primordium. Fin rays developed rostrad and caudad from this center. Fifteen second dorsal fin rays were present in a 4.0 mm SL (16 days) larva. In this larva the first dorsal fin spines had not completed development anteriorly. Thirty-six specimens 4.0-116 mm SL had the adult count of 15 and five had 14 rays. All second dorsal fin rays had bifurcated bases, which held the serially associated distal radials.

-Figure 14. Ontogeny of basi pterygia from 3 laboratory-reared and 1 wild-caught Microspathodon chrysurus. dorsal view. Top to bottom specimens' lengths in mm SL were: 54.4, 9.5, 7.3,4.5. AX, anterior xiphoid process; CP, central part; EDW, external dorso-Iateral wing; IW, internal lateral wing; PX, posterior xiphoid process. Cartilage, white; ossifying, stippled. 356 BULLETIN OF MARINE SCIENCE, VOL. 40, NO.2, 1987

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Figure 16. Ontogeny of predorsal bones and first pterygiophore and associated two fin spines and their relationship to first three interneural spaces from 5 laboratory-reared and I wild-caught Mi- crospathodon chrysurus, left lateral view. Top left to bottom right specimens' lengths in mm SL were: 4.0, 7.3, 9.2, 11.2, 17.5, 116. D, distal radial; Int, interneural space; Ns, neural spine; P, proximal radial; Pd, predorsal bone; S, fin spine. Cartilage, white; ossifying, stippled.

Second Dorsal Fin Supports (Figs. 18-20).-No second dorsal fin pterygiophores were observed in preflexion larvae of 3.7 mm NL (16 days) or less, but they were all present in cartilage in the 3.7 mm NL (16 days) flexion larva. We were unable to determine if second dorsal fin pterygiophores developed before the first dorsal fin pterygiophores, because of insufficient number of specimens. Ossification of second dorsal fin proximal radials started at 4.5 mm SL (18 days) and all were ossifying at 7.3 mm SL (25 days). The distal radials began ossification much later POTTHOFF ET AL.: MICROSPATHODON LARVAL DEVELOPMENT 357

Figure 17. Ontogeny of 5th and 6th pterygiophores (first dorsal fin) and associated fin spines and relationships to 7th interneural space from 5 laboratory-reared and I wild-caught Microspathodon chrysurus, left lateral view. Top left to bottom right specimens' lengths in mm SL were: 4.0,7.3,9.2, 11.2, 17.5, 116. For abbreviations, see Figure 16. Cartilage, white; ossifying, stippled. at 10.7 mm SL (50 days). Ossification started with the anterior distal radials and proceeded in a posterior direction. Each second dorsal fin pterygiophore originated from one piece of cartilage. A fin ray formed on top of the distal portion of the pterygiophore cartilage with the bifurcated base of the ray extending laterally over the cartilage. Later the distal portion of the cartilage was pinched off giving rise to the distal and proximal radials. The proximal radial ossified first, but the proximal tip remained cartilaginous. Later sagittal and lateral keels were added to the proximal radial. The spherical distal radial cartilage started ossification bilaterally from two dorso- posterior places; ossification proceeded latero-anteriorly and finally ventrad. The distal radials in adults are two pieces of bone having a common cartilaginous anterior tip; posteriorly the two parts of the distal radial articulate with the base of the bifurcated fin ray. The posteriormost second dorsal fin pterygiophore supported a double ray and had a stay ventrad to the proximal radial. The stay originated from the pterygiophore cartilage, and it became autogenous after ossification. M. chrysurus had no middle radials in the second dorsal fin supports. Anal Fin (Figs. 18,21, Table 4).-The adult anal fin spine and ray count was usually 11,13.Thirty-nine specimens of4.0-ll6 mm SL had 11,13;one 10.7 mm SL specimen had 11,12 and two specimens 12.0, 19.8 mm SL had 11,14 anal fin 358 BULLETIN OF MARINE SCIENCE, VOL. 40, NO.2, 1987

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Figure 18. Selected pterygiophores and associated fin spines or rays from an adult wild-caught Microspathodon chrysurus (114 mm SL). Top left to bottom right pterygiophores and views are: left lateral view of anteriormost two first dorsal fin pterygiophores, associated fin spines were removed and anterior view of their bases is shown; left lateral view of first and second anal pterygiophores, associated fin spines and rays were removed and anterior view of their bases is shown; left lateral view of 16th dorsal pterygiophore (4th pterygiophore of 2nd dorsal fin), associated fin rays were POTrHOFF ET AL.: MICROSPATHODON LARVAL DEVELOPMENT 359

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Figure 19. Ontogeny of 17th dorsal pterygiophore (5th pterygiophore of the second dorsal fin) and serially associated fin ray from 5 laboratory-reared and 1 wild-caught Microspathodon chrysurus. left lateral view. Top left to bottom right specimens' lengths in mm SL were: 4.0, 7.3, 9.8, 11.5, 17.5, 116. For abbreviations, see Figures 16 and 18. Cartilage, white; ossifying, stippled.

+- removed and anterior view of their bases is shown; left lateral view of 5th and 6th first dorsal fin pterygiophores, associated fin spines were removed and anterior view of their bases is shown; dorsal view of 5th and 6th first dorsal fin pterygiophores with associated fin spines removed. R, fin ray. For other abbreviations, see Figure 16. Cartilage, white; bone, stippled. 360 BULLETIN OF MARINE SCIENCE, VOL. 40, NO.2, 1987

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", ..•..." . "~."'s~:"~ ',~" """".. '." .. :.:,.~.

' "'''''-' '.::-': ..,.• ~ \ t------i 1 mm 5t Figure 20. Ontogeny of the posteriormost second dorsal fin pterygiophore and serially associated double fin ray from 4 laboratory-reared and one wild-caught Microspathodon chrysurus, left lateral view. Top left to bottom right specimens' lengths in mm SL were: 7.3, 9.2, 11.2, 17.5, 116. St, stay. For other abbreviations, see Figures 16 and 18. Cartilage, white; ossifYing, stippled. spines and rays. The two anal fin spines had closed bases and anal rays had bifurcated bases. Anal fin spines and rays were first observed in the 3.7 mm NL (16 days) flexion larva. Addition of anal fin rays was in a posterior direction and the adult com- plement of anal fin spines and rays was already present in some 4.0 mm SL (16 days) post flexion larvae. We believe that addition of anal spines and rays was also in an anterior direction, although we did not observe this because of lack of specimens in the flexion and immediate pre flexion stages. Anal Fin Supports (Figs. 18, 21). - All preflexion larvae had no anal pterygiophore development, but all anal pterygiophores were present in cartilage in the 3.7 mm NL (16 days) flexion larva. The posteriormost three pterygiophores of this flexion larva did not support any anal rays. In some 4.0 mm SL (16 and 18 days) specimens and in all larger specimens, all anal pterygiophores supported rays. Ossification of anal fin proximal radials started anteriorly at 4.5 mm SL (18 days) and proceeded posteriorly. All anal pterygiophores were ossifying at 9.2 mm SL (29 days). Ossification of distal anal-fin radials began anteriorly at 10.7 mm SL (50 days) and proceeded caudad. Individual anal fin pterygiophore development was similar to development of second dorsal fin pterygiophores, including the absence of middle radials. The POTTHOFF ET Al.: MICROSPATHODON LARVAL DEVELOPMENT 361

Figure 21. Ontogeny of first two anal fin pterygiophores and their associated fin spines and rays from 5 laboratory-reared and I wild-caught Microspathodon chrysurus, left lateral view. Top left to bottom right specimens' lengths in mm SL were: 4.0, 7.3, 9.2, 11.2, 17.5, 116. Hs, haemal spine. For other abbreviations, see Figures 16 and 18. Cartilage, white; ossifying, stippled. anteriormost anal pterygiophore developed similar to a first dorsal fin pterygiophore. It was much larger than the remaining pterygiophores and supported two supernumerary spines and a serially associated ray. During early development there was no evidence of two cartilages fusing to form the first anal pterygiophore. However, this does not rule out possible development from two parts of cartilage (see discussion). The two supernumerary spines of the first anal pterygiophore were attached by rings of bone similar to the one supernumerary spine of the first dorsal pterygiophore. The serial ray of the first anal pterygiophore had an autog- 362 BULLETIN OF MARINE SCIENCE, VOL. 40, NO.2, 1987

Figure 22. Common arrangement of pre dorsal bones, pterygiophores, fin spines, and rays in relation to the skull and vertebral column for 34 laboratory-reared (7.3-17.5 mm SL) and 3 wild-caught (54.4- 116 mm SL) Microspalhodon chrysurus. Modified after Matsui (1967). A, skull and vertebrae numbers; B, interneural and interhaemal space numbers; C, number of predorsal bones or pterygiophores in respective interneural or interhaemal space; D, number of fin spines or rays associated with pterygiophore; E, frequency of occurrence in 37 specimens for number of pterygiophores in respective interneural or interhaemal spaces. enous distal radial between the halves of its bifurcated base. The posteriormost anal pterygiophore resembled the last second dorsal fin pterygiophore; it supported a double ray and had a stay that developed from the proximal radial cartilage. M. chrysurus had no middle radials in the anal fin supports. Fin Spine and Ray Association with Pterygiophores, Arrangement of Predorsal Bones and Pterygiophores in the Interneural and Interhaemal Spaces (Figs. 16- 18,21,22).- There were three predorsal bones. The anteriormost dorsal pterygiophore supported two spines. The anterior spine was secondarily (supernumerary), and the second spine serially associated with the first dorsal pterygiophore. The remaining first dorsal fin spines and second dorsal fin rays had one serially associated fin element. A secondarily associated fin element was present on each proximal radial. This element was serially associated with the anteriorly preceding pterygiophore. Only the posteriormost second dorsal double fin ray did not as- sociate secondarily. Anal fin ray association with the pterygiophores was the same as described for the second dorsal fin, except the first anal pterygiophore supported two anal spines in a secondary association (supernumerary) and a ray in a serial association. The interneural and interhaemal spaces were bound by neural and haemal spines. Only the first interneural space was anteriorly bound by the skull and posteriorly by the first neural spine. The first interhaemal space was anteriorly bound by the gut and posteriorly by the first haemal spine. In Figure 22, the interhaemal spaces were numbered the same as the oppositely located interneural spaces; thus the first interhaemal space is number 12. The pterygiophore insertion pattern into the interneural and interhaemal spaces, as shown in Figure 22, was constant in 37 specimens for the first 16 interneural spaces, which includes positions of the predorsal bones and all first dorsal fin pterygiophores and only three second dorsal fin pterygiophores. The insertion pattern was variable for the last four interneural spaces under the second dorsal fin. In 37 examples, the second dorsal fin supports terminated in the 20th interneural space, and had most commonly (27 times) two pterygiophores in that space and less commonly one or POTIHOFF ET AL.: MICROSPA TllODON LARVAL DEVELOPMENT 363

three pterygiophores. The insertion pattern above the anal fin was almost constant. The first anal pterygiophore inserted in interhaemal space number 12 and was situated anterior to the first haemal spine. The anal fin supports terminated with two pterygiophores in the 19th interhaemal space in 36 out of 37 specimens. The one remaining specimen had three pterygiophores in the 19th and one in the 20th interhaemal space. Branchiostegal Rays and Hyoid Arch (Fig. 23, Table 3).-One branchiostegal ray was present in a 2.7 mm NL (9 days) preflexion larva. Additional rays were added in an anterior direction. The maximum count of six branchiostegal rays was attained in a 3.7 mm NL (16 days) flexion larva. All larger and older specimens had six rays, except one 10.9 mm SL (50 days) larva which had five rays. Bran- chiostegal rays were directly and indirectly supported by bones of the hyoid arch. In adults the epihyal supported two rays and the ceratohyal four. The anteriormost two rays were considerably smaller than the following four. The hyoid arch developed first from the following three pieces: hypohyal, epi- ceratohyal and interhyal cartilages. The epi-ceratohyal cartilage started ossification first anteriorly in the area of the future ceratohyal bone. Next ossification of the epihyal began in the posterior portion of the cerato-epihyal cartilage, followed by the ossification of the small interhyal cartilage. Last to ossify was the hypohyal cartilage, which ossified to form two bones. The ventral hypohyal formed a ball- and-socket joint with the ceratohyal. The dorsal hypohyal and the ceratohyal each developed a foramen. The ceratohyal foramen is the beryciform foramen of McAllister (1968). Branchial Skeleton (Figs. 24, 25, Table 3).- The branchial skeleton of adult M. chrysurus consists of an upper and lower portion. The lower portion consists of five arches having four ceratobranchials on each side, and a fused fifth pair of ceratobranchials in the center. There are three hypobranchials on each side with four basibranchials in the center. Two rows of gillrakers (inner and outer rows) are present on the ceratobranchials of gill arches I to 3, but only the outer row is present on the ceratobranchial of the fourth arch. The single fifth ceratobranchial had teeth over its dorsal surface. Only the hypobranchial of the first gill arch supports gill rakers from the outer row, the remaining hypobranchials have no rakers. Of the four basibranchials, three are ossified, but the fourth is cartilaginous. The upper portion of the branchial skeleton consists of only four arches having four epibranchials and four infrapharyngobranchials. Only outer row gillrakers are present on epibranchials 1 to 3; epibranchial 4 has no rakers. The infrapharyngobranchials 2 to 4 have upper pharyngeal toothplates on the ventral side. Infrapharyngobranchial I suspends the upper branchial skeleton to the skull and has no tooth plates. A process pointing anteriorly is present on epibranchial 1 and a process pointing posteriorly is present on epibranchial 3. At the anterior end of the process on epibranchial I is a cylindrical piece of cartilage (interarcual cartilage), which abutts with infrapharyngobranchial 2. The process on epibranchial 3 abutts posteriorly with epibranchial 4. The branchial arches developed from cartilage (endochondral), but the gillrakers and toothplates developed outside the cartilage (dermal). First to start ossifying were the ceratobranchials and the upper pharyngeal toothplates. Outer row rakers developed on all four arches before inner row rakers developed sequentially on gill arch 2, arch 3 and finally arch 1. Basibranchials I to 3 originated from one piece of basibranchial cartilage and ossified to three bones. Basibranchial4 came from a separate piece of cartilage and remained cartilaginous in adults. The fused 5th ceratobranchials originated from left and right pieces of cartilage. Both pieces 364 BULLETIN OF MARINE SCIENCE, VOL. 40, NO.2, 1987

D o

I .1mm ,1mm

Figure 23. Ontogeny of hyoid arch from 6 laboratory-reared and I wild-caught Microspathodon chrysurus, left lateral view, Top left to bottom right specimens' lengths in mm NL or SL were: 2.9, 3.4,4.4,7.3, 11.5, 17.5,54.4. BF, beryciform foramen; Br, branchiostegal ray; CH, ceratohyal; DHH, dorsal hypohyal; DHHF, dorsal hypohyal foramen; EH, epihyal; IH, interhyal; VHH, ventral hypohyal. Cartilage, white; ossifying, stippled.

ossified separately and then fused to one "delta" shaped bone with many teeth on its dorsal surface. We only counted the outer row rakers of the first gill arch. These were first observed on the posterior portion of the ceratobranchial bone (near the angle) in the 3.7 mm NL (16 days) flexion larva. At 4.0 mm SL (16 days) the raker in the epi-ceratobranchial angle developed. Rakers were added in an anterior direction on the ceratobranchial. At 7.3 mm SL (25 days) the first epibranchial raker was POlTHOFF ET AL.: MICROSPATHODON LARVAL DEVELOPMENT 365

Figure 24. Ontogeny of branchial skeleton of 4 laboratory-reared Microspathodon chrysurns. with dorsal view for lower left and right arches, ventral view for left upper arches and dorsal view for right upper arches. Upper arches have been cut and are not in their natural positions. Starting with top left and finishing with bottom right specimens' lengths in mm NL or SL were: 3.4, 7.3, 9.8, 19.8. B, basibranchial; BC, basibranchial cartilage of BI-3; C, ceratobranchial; Epibranchial; H, hypobranchial; I, infrapharyngobranchial; IC, interarcual cartilage; PROC-E, process on epibranchial; UP, upper pharyngeal tooth plate develops ventrad on infrapharyngobranchial. Cartilage, white; ossifying, stippled. 366 BULLETIN OF MARINE SCIENCE, VOL. 40, NO.2, 1987

1mm

Figure 25. Branchial skeleton of an adult wild-caught Microspathodon chrysurus 54.4 mm SL. At bottom of drawing right lateral view of the fused 5th ceratobranchials and 4 basibranchials is shown. For explanation of other views and abbreviations, see Figure 24. Cartilage, white; bone, stippled. seen posteriorly near the angle. Addition of epibranchial rakers was in an anterior direction. Hypobranchial rakers were first seen in all 50 day old larvae. The adult gillraker count of (9-14)+(1)+(13-14)+(3) = (27-31) was only present in wild- caught juveniles and adults 54 mm SL and larger. POTTHOFF ET AL.: MICROSPATHODON LARVAL DEVELOPMENT 367

Figure 26. Ontogeny of left opercular bones from 5 laboratory-reared and one wild-caught Micro- spathodon chrysurus. lateral external view. Top left to right specimens' lengths in mm NL or SL were: 3.7, 4.0, 9.8, 12.0, 17.5, 116. ES, exterior shelf of preopercle; lOP, interopercle; IS, interior shelf of preopercle; OP, opercle; POP, preopercle; SOP, subopercle. Hyaline blue stained areas, white; red stained bone, stippled.

Opercular series (Fig. 26). - The opercular series in M. chrysurus consists of four dermal bones: opercle, subopercle, preopercle and interopercle. These bones developed first simultaneously in the 3.7 mm NL (16 days) flexion larva and were present in all larvae larger and older. The opercular bones changed their shape somewhat during ontogeny with the preopercular changing to the largest extent. At 3.7 mm NL (16 days) the preopercular bone had a very small exterior shelf with a smooth edge and a large interior shelf with two spines on its edge. The exterior shelf retained its smooth edge throughout development and became almost as large as the interior shelf. The interior shelf developed many spines on its edge which became serrations by 17.5 mm SL (79 days). In adults the serrations had disappeared and the edge had become smooth. The opercular, subopercular and interopercular bones were flat, 368 BULLETIN OF MARINE SCIENCE, VOL. 40, NO.2, 1987 slightly convex bones which retained their distinctive shapes throughout development.

DISCUSSION The distinctive early preftexion larvae of M. chrysurus look very similar to those of Abudefduf luridus as described by Re (1980) (Fig. 1). D. A. Hensley2 believes that the similarities may indicate some unknown relationship among the two genera. Shaw (1955) and Cummings (1968) provide poor illustrations and short descriptions of A. saxatilis. Thus it is not possible to make comparisons with M. chrysurus larvae, or with the description of A. luridus by Re, except that the prominent dorsal and ventral mid-tail melanophores were lacking in Shaw's and Cumming's specimens. The early larva of A. abdomina/is illustrated by Miller et aI. (1979) has some pigmentation resemblance to M. chrysurus and A. luridus, but the caudal finfold melanophores, the large dorsal and ventral mid-tail melanophores and the pectoral finfold pigmentation of M. chrysurus and A. /uridus are absent. The head shape of A. abdominalis is deeper vertically than in M. chrysurus and A. luridus, resembling Amphiprion chrysopterus (Allen, 1972). Leis and Rennis (1983) illustrate a flexion stage larva of Abudefduf which does not resemble M. chrysurus or A. luridus. Early larvae of Chromis notatus (Fujita, 1957), C. chromis (Padoa, 1956), C. punctipinnis (Turner and Ebert, 1962) and Chromis sp. (Leis and Rennis, 1983) have the same elongate shape as early M. chrysurus and A. luridus larvae. All Chromis larvae lacked the large dorsal and ventral tail melanophores, the ventral caudal finfold melanophores and the pectoral finfold pigmentation of M. chrysurus and A. luridus. Microspathodon chrysurus larvae have distinctive pigmentation, which is not present in any other pomacentrid larva thus far described (Miller et aI., 1979; Leis and Rennis, 1983), except the A. luridus larva (Re, 1980). Foremost in distinction is the oversized pigmented pectoral fin, the large dorsal and ventral mid-tail melanophores and the 1 or 2 large melanophores over the hind brain (Figs. 1-3). Gaps in our series of laboratory-reared M. chrysurus larvae (Tables 3 and 4, Fig. 7) prevented determination of initial appearance and directional addition of cartilaginous neural and haemal arches and spines along the notochord. In An- isotremus virginicus (Haemulidae) (Potthoff et aI., 1984), Scombrolabracidae and Scombridae (Collette et aI., 1984; Potthoff et aI., 1986), the initial appearance is in four locations: at the anterior, central (dorsal, ventral) and posterior portions of the notochord. We assume that in M. chrysurus the cartilaginous neural and haemal arches and spines may also first appear in four locations along the notochord. The reason for this assumption is that the smallest larvae first developed a few anterior neural spines and then some hypurals posteriorly and that in percoids this manner of development seems to be the most basic kind. Ossification of the vertebral column from anterior to posterior and the ossification of the urostyle and preural centra 2 and 3 from posterior to anterior has been observed in the Scombridae (Kramer, 1960; Potthoff, 1975), Sparidae (Houde and Potthoff, 1976), Coryphaenidae (Potthoff, 1980), Scombrolabracidae (Potthoff et aI., 1980), Percichthyidae (Fritzsche and Johnson, 1980), Xiphiidae (Potthoff and Kelley, 1982), Centropomidae (Lau and Shafland, 1982), Haemulidae (Pott- hoff et aI., 1984) and Scombroidei (Potthoff et aI., 1986). Ossification of the vertebral column of M. chrysurus is from anterior to posterior as in the above

, Donnie A. Hensley, Deportment of Marine Sciences. University of Puerto Rico Mayaguez, Puerto Rico 00708, pers. comm. 1985. POTTHOFF ET AL.: MICROSPATHODON LARVAL DEVELOPMENT 369

mentioned families (Fig. 7). We are unable to confirm the anteriorly directed development of the urostyle and the preural centra 2 and 3 because of the gap in our series between 4.5 (18 days) and 7.3 mm SL (25 days) (Tables 3 and 4). Pleural ribs in M. chrysurus articulated with the parapophyses of the precaudal vertebrae (Fig. 8). Epipleural ribs were not only articulating on the parapophyses of the precaudal vertebrae but also on the haemal arches of the first four or five caudal vertebrae (Fig. 10). The arrangement of ribs in M. chrysurus (Table 3) is the same as that in Lepidozygus tapeinosoma (Emery, 1980), except the former has epipleural ribs on four or five caudal vertebrae, whereas the latter has them only on two. It is not unusual for Perciformes to have epipleural ribs on some of the anterior caudal centra (Springer, 1968; Johnson, 1981; Springer, 1983), but not all Perciformes develop epipleural ribs on the caudal centra (Springer and Freihofer, 1976; Potthoff et al., 1980; Potthoff and Kelley, 1982; Potthoff et al., 1984). Because epipleural ribs are absent on caudal centra in many perciforms, we consider their presence on some of the caudal centra as primitive. Emelianov (1935) described rib development in fishes from histology and found that ribs are either of cartilage or dermal (connective tissue) origin, and in some cases of both origins. In M. chrysurus the epipleural ribs originated in the connective tissue of the myosepta directly as bone, whereas pleural ribs originated from cartilage and then ossified. The same kind of rib development was found in two species of Morone (Percichthyidae) (Fritzsche and Johnson, 1980) and Anisotremus virginicus (Haemulidae) (Potthoff et al., 1984). The caudal complex development and structure of M. chrysurus (Figs. 11 and 12)is typical of basic percoids, but a number offeatures are advanced. M. chrysurus developed only the larger anterior uroneural. This uroneural fused to the urostyle during development, continuing the neural canal above the urostyle (Fig. 12). This feature constitutes an advancement; Johnson (1984, table 120) reported two uroneurals in 66 out of 96 percoid groups, one uroneural in 22 groups and 8 groups without uroneurals. Emery (1980) reported one uroneural fused to the urostyle for the pomacentrid L. tapeinosoma, but he labeled his figure 20 as if uroneural 1 and 2 had fused. The absence of a procurrent spur on the posteriormost ventral secondary caudal ray in M. chrysurus constitutes an advancement. Johnson (1975) examined seven pomacentrid genera and found the procurrent spur lacking in all of them. Another advanced feature in the caudal complex of M chrysurus was the reduction of principal caudal rays from the basic perciform 9+8 to an 8+7 count. Richards and Leis (1984) imply that pomacentrids have the typical percoid 9+ 8 principal caudal fin ray count and that the inclusion of the pomacentrids in the labroids by Kaufman and Liem (1982) may be unwarranted, according to early life history characters. Leis and Rennis (1983) reported reduced principal caudal fin ray counts of8+7 and 7+6 for 10 Indo-Pacific pomacentrid genera in the subfamilies Chrominae and Pomacentrinae. Their and our work on principal caudal fin rays in pomacentrids lends further support to Kaufman and Liem's (1982) inclusion of the Pomacentridae in the Labroidei, because all other labroid families (Cichlidae, Embiotocidae, Labridae) have reduced principal caudal ray counts. Kaufman and Liem did not include the principal caudal fin ray character in their study. In perciform fishes that have 9+8 principal caudal rays, the rays articulate with the hypural bones starting dorsally with hypural 5, and ending ventrally with the parhypural and the haemal spine of preural centrum 2 (Potthoff et al., 1980; 1984). In M. chrysurus, probably because of the reduced principal caudal ray count, the articulation sequence of the rays is different (Table 6, Fig. 11); hypural 5 supports a secondary caudal ray and the principal caudal rays are supported only by hypurals 4 to 1 and the parhypural. The haemal spine 370 BULLETIN OF MARINE SCIENCE, VOL. 40, NO.2, 1987 of preural centrum 2 supports a secondary caudal ray. The upper secondary and principal caudal rays in M. chrysurus are supported by elements of the urostyle and preural centrum 2, whereas the lower rays are supported by elements of the urostyle and preural centra 2 and 3. In most percoids the upper and lower caudal fin rays are dorsally and ventrally supported by the same number of centra. Except for the uroneural fusion (Fig. 12) and an occasional fusion of the distal part of the parhypural to hypural 1 (Fig. 11), no other fusion was observed in the hypural complex of M. chrysurus. However, fusion of the hypural bones to form upper and lower hypural plates was observed in the pomacentrid L. tapeinosoma by Emery (1980). The presence of third preural cartilages in M. chrysurus (Fig. 11) is a primitive feature, since these cartilages are found in the Beryciformes (Johnson, 1983). Johnson (1984, p. 481) found third preural cartilages in 45 out of66 percoid groups. Generally, damselfish often use their pectoral fin for propulsion. This mode of swimming is reflected in robust and expanded bones of the pectoral girdle, par- ticularly the cleithrum and post-cleithrum 1 (Fig. 13) (Emery 1970; 1980). The development of the pectoral girdle has not been studied for any Labroidei; we compare the pectoral girdle development in M. chrysurus to perciform fish that have been studied. The overall structure and development of the pectoral girdle of M. chrysurus is very similar to that of A. virginicus described by Potthoff et al. (1984), except M. chrysurus developed a posteriorly located coracoid foramen, and wild-caught specimens had an additional anteriorly located coracoid foramen (Table 5, Fig. 13). All 14 damselfish species studied by Emery (1973) had the posteriorly located coracoid foramen, but the foramen was absent in L. tapeinosoma (Emery, 1980). Starks (1930) depicted the coracoid foramen in some scorpaeniform fishes but did not comment on it. The systematic significance of the coracoid foramen is not known. We suspect the coracoid foramen may be present in the pomacentrids and most labrids and perhaps may characterize labroids. We examined 11 Lachnolaimus maximus (Labridae) larvae and two juveniles. All larvae had a small foramen ventrad in the coraco-scapular cartilage, but in both juveniles the foramen was absent and had probably been overgrown by bone. In other labrids, W. J. Richards3 observed the foramen in larvae of Bodianus sp., but found it absent in larvae of Xyrichthys spp., Halichoeres spp. and Thalassoma bijasciatum. M. F. Gomon4 found the coracoid foramen in adults of Clepticus parrai, Paracheilinus sp. and Pteragogus sp. and we observed it in a juvenile Decodon puellaris. The formation ofthe scapular foramen by invagination and subsequent closure in the dorsal process of the coraco-scapular cartilage has been described for the first time by Balart (1985) for the pleuronectiform fish Paralichthys olivaceus. This type of scapular foramen development was not observed by us in M, chrysurus, although it may be present during ontogeny. This developmental process may be so quick that it did not show up in our size series or in any developmental study of other fish larvae. The pelvic fins and supporting bones in M. chrysurus were the last of the fins and supports to start developing (Table 5, Figs. 13-15). The development of the pelvic fin rays from the lateral edge toward mesial has been reported for all perciform fish studied thus far. To our knowledge, labroid development has not

J William J. Richards. Senior Scientist. National Marine Fisheries Service. NOAA, Southeast Fisheries Center, 75 Virginia Beach Drive. Miami, FL 33149, pers. eamm. 1986. • Manin F. Gamon. Curator. Department oflchthyology, Museum of Victoria, 328 Swanston Str .• Melbourne, Victoria 3000, Australia, pers. eamm. 1986. POTTHOFF ET AL.: MICROSPATHODON LARVAL DEVELOPMENT 371

been studied. The development and structure of the basi pterygia of M. chrysurus is similar to some perciforms studied by us such as Coryphaena (Potthoff, 1980), Scombrolabrax (Potthoff et aI., 1980) and Anisotremus (Potthoff et aI., 1984), but dissimilar to others such as Istiophoridae, some Gempylidae and some Trichiuri- dae (Potthoff, pers. obs.). In some perciform groups the pelvic fins and supports may be entirely absent as in some Trichiuridae (Potthoff, pers. obs.) and Xiphias gladius (Potthoff and Kelley, 1982). We were unable to determine the sequence of development of the dorsal and anal fins and their supports due to the small number of specimens and damage (Tables 3 and 4, Fig. 7). We assume, however, that the second dorsal and anal fins and supports develop first from a center and are followed by the first dorsal fin and supports also developing from a center. Addition of fin elements for all three fins would then be anteriorly and posteriorly. The reasons for this assumption are threefold. First, the 3.7 mm NL flexion stage larva had a damaged first dorsal fin and the second dorsal fin was incomplete posteriorly as evidenced by pterygiophores without fin rays. The 4.0 mm SL larva had a complete second dorsal fin, but the first dorsal fin was incomplete anteriorly as evidenced by the anteriormost pterygiophore without fin spines. Second, Leis and Rennis (1983) reported that in most pomacentrid larvae the second dorsal and anal fins start to develop before the first dorsal fin, although in some species (A. abdominalis, Miller et aI., 1979) the first dorsal fin starts to develop first. Third, the most common perciform developmental pattern is that the second dorsal and anal fins start to develop before the first dorsal fin. Potthoff et ai. (1984) discussed families in which this type of development occurs. The structure and arrangement of the predorsal bones and the dorsal and anal fin spines and rays and their supporting pterygiophores in M. chrysurus (Figs. 7, 16 and 22) is basically that of lower perciform fishes. The three predorsal bones occupied interneural spaces 1, 2 and 3, and the first dorsal pterygiophore, which supported one supernumerary spine, shared interneural space 3 with the posterior predorsal bone. Two pterygiophores occupied interneural space 4. The formula based on Ahlstrom et ai. (1976) for M. chrysurus was 0/0/0 + 1/1 + 1. Emery and Allen (1980) observed the same formula in eight out of 21 damselfish genera. This formula has been observed by Johnson (1984, Table 120) in 10 of96 percoid groups (families, subfamilies, incertae sedis genera). In addition, 66 groups had three predorsal bones; 39 groups supported only one supernumerary spine on the first dorsal pterygiophore; and in 15 groups the first pterygiophore inserted in interneural space 3, followed by two pterygiophores in interneural space 4. The first anal fin pterygiophore of percoids most often supports three spines of which two are supernumerary and the third is serially associated (Johnson, 1984). In M. chrysurus, two supernumerary spines and one serially associated ray were supported by the first anal pterygiophore (Figs. 7, 18, 21, and 22). According to Johnson (1984) a serial ray supported by the first anal pterygiophore constitutes an advancement. In the sparid Archosargus rhomboidalis (Houde and Potthoff, 1976) and the haemulid A. virginicus (Potthoff et aI., 1984) the serially associated element supported by the first anal pterygiophore developed first as a ray and then transformed to a spine. The non-transformation of the serially associated fin ray to a fin spine during ontogeny may be an evolutionary reduction in M. chrysurus. Middle radials were entirely absent in the second dorsal and anal fins in M. chrysurus (Fig. 20). Many Perciformes have middle radials (trisegmental pterygiophores) in the posterior parts of the second dorsal and anal fins. This condition is believed to be basic to the Perciformes. Absence or reduction in number of 372 BULLETIN OF MARINE SCIENCE, VOL. 40, NO.2, 1987 middle radials constitutes an advancement, although we believe that middle radials are not lost but are fused to the proximal radials. In 54 out of 96 percoid groups, Johnson (1984, table 120) found one to many trisegmental pterygiophores. Relatively large stays were associated with the posteriormost dorsal and anal pterygiophores in M. chrysurus (Fig. 20), Johnson (1984, table 120) reported the presence of stays in 80 out of 96 percoid groups. Bridge (1886) considered the stay to be a "vestigial radial element" and Potthoff (1974) thought it to be a reduced proximal radial that had lost its other radials and fin rays. Later developmental studies (Potthoff, 1975; 1980; Potthoff et al., 1980; Potthoff and Kelley, 1982; Potthoffet al., 1984) indicated that the origin of the stay is from the proximal or middle radial cartilage. In these studies the stay was never observed separately, although it is possible without being observed for the stay to originate separately and immediately fuse to the proximal radial cartilage. Kohno observed in a number of studies for different fish species (Kohno and Taki, 1983; Kohno et al., 1983; Kohno et al., 1984) that the cartilaginous stay originated by itself but subsequently fused to the proximal or middle radial before ossification. Thus, Kohno and Taki (1983) suggest that the stay is a vestigial pterygiophore because of its separate origin and because of the double ray that is serially associated with the last pterygiophore. The distal radials of M. chrysurus separated from the proximal radial during development (Figs. 17 and 19), suggesting a common origin for the distal and proximal radials. This type of development has also been observed for Thunnus atlanticus, Coryphaena spp., Scombrolabrax heterolepis, Xiphias gladius and An- isotremus virginicus (Potthoff, 1975; Potthoff, 1980; Potthoff et al., 1980; Potthoff and Kelley, 1982; Potthoff et al., 1984). Kohno and Taki (1983) and Kohno et al. (1983; 1984) never observed a separation of the distal from the proximal radial cartilage. In fact, they suggest that the proximal and middle radials originate from one piece of cartilage, whereas the distal radial has its separate origin. The dorsal hypohyal and the ceratohyal of juvenile and adult M. chrysurus each had a foramen (Fig. 23). The foramen in the dorsal hypohyal has been observed in a number of perciform fishes, but its systematic significance has not been evaluated. The foramen in the ceratohyal, however, has been evaluated by McAllister (1968) and named the beryciform foramen. The foramen is characteristic of several primitive acanthopterygian orders (McAllister, 1968). It is found in a number of perciform families including the Pomacentridae (Emery, 1973; 1980). Perciformes with a beryciform foramen were considered primitive by McAllister (1968). McAllister examined the Labroidei (exclusive of the Poma- centridae at that time) and reported the absence of the beryciform foramen. He also examined the Pomacentridae and reported the beryciform foramen absent, although it was reported present in Emery's (1973; 1980) studies. Ciardelli (1967) examined the hyoid arches of juvenile and adult M. chrysurus. He did not mention or show a beryciform foramen on the ceratohyaI. Also, the two hypohyals are shown by Ciardelli as one bone (basihyal). We cannot offer an explanation for Ciardelli's findings since our and Emery's (1973) M. chrysurus juveniles and adults had a beryciform foramen and two hypohyals. The branchial skeleton of M. chrysurus (Figs. 24 and 25) had almost all of the components of a primitive percoid as defined by Johnson (1981), except the tooth plates of the second and third epibranchials had been lost. These epibranchial tooth plates were absent in other pomacentrid species examined by Emery (1973; 1980). The branchial skeleton ofpomacentrids also differed from that of primitive percoids in having fused fifth ceratobranchials (Ciardelli, 1967; Emery, 1973; 1980; Nelson, 1967), and is one of three derived characters used by Kaufman POTTHOFF ET AL.: MICROSPATHODON LARVAL DEVELOPMENT 373 a'nd Liem (1982) to include the Pomacentridae in the Labroidei. In M. chrysurus the fifth ceratobranchials had ontogenetically fused from two elements. Possibly, in other pomacentrids and labroids the single fifth ceratobranchial tooth plate is derived from two pieces through ontogenetic fusion. Only further developmental studies, however, would clarify this.

ACKNOWLEDGMENTS

We thank the following persons for reviewing the manuscript: M. F. Gomon, D. A. Hensley, K. F. Liem, K. C. Lindeman and W. J. Richards. J. Fraga contributed one adult specimen. P. J. Fisher typed many manuscript drafts. J. C. Javech drew Figures 1,5, and 7; the remaining figures were drawn by the second author. The first and second authors did the pigmentation and osteology, the third author did the morphometrics and the fourth and fifth authors reared the larvae.

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DATE ACCEPTED: April 8, 1986.

ADDRESSES: (T.P. and s.K.) NOAA/National Marine Fisheries Service, Southeast Fisheries Center, 75 Virginia Beach Drive, Miami. Florida 33149; (V.S.) Biology Department. Muskingum College, New Concord. Ohio 43762; (M.M. and F. Y.) Aqualife Research Corporation. % Walker's Cay Hotel and Marina. 700 S. W. 34th Street, Fort Lauderdale, Florida 33315.

&lt;I&gt;Microspathodon Chrysurus&lt;/I&gt;

<I>Microspathodon Chrysurus</I>