BULLETIN OF MARINE SCIENCE, 56(2): 495-522, 1995
DEVELOPMENT OF THE VERTEBRAL COLUMN, FINS AND FIN SUPPORTS IN THE JAPANESE ANCHOVY, ENGRAULIS JAPONICUS (CLUPEIFORMES: ENGRAULIDIDAE)
Eduardo F. Balart
ABSTRACT The ontogeny of the median and paired fins and their supports, the vertebral column, predorsal bones, and pleural ribs of Engraulis japonicus are described, A size series of 101 laboratory-reared specimens 2.3 mm NL to 37.3 mm SL from 0 to 59 days old, and an additional series of ]8] wild-caught anchovy 1.5 mm NL to ]] 0.6 mm SL were cleared and stained for both cartilage and bone. All fin supports form from cartilage in the following sequence: pectoral, caudal, dorsal, anal, and pelvic fin support. Completion of fins is in a different order. Almost all fin structures are present and partially ossified by the 5]st day after hatching (ca. 24-27 mm SL). Caudal fin supports start development in 6.] mm NL 9 day old larvae with chondrification of hypural ] below the unflexed notochord. The anterior adult epural develops from two pieces of cartilage. Caudal fin rays develop from middle ones outward. Full complement of principal cauda] rays is present in larvae >8.0 mm SL (1]-20 days after hatching). Dorsal and anal fin anlagens appear in larvae >6.2 mm SL. The enlarged first dorsa] proximal radial originates from one piece of cartilage. A supernumerary dorsal distal radial develops behind the first distal radial. Left and right coraco-scapu]a cartilages appear first fused ventromedially. Propterygium develops from the pectoral radial plate. The pelvic scute originates from three sca]e-like pieces accounting for the lateral arms and the basal plate. Ossification of centra begins from ]2.2 mm SL. Neural and haemal arches begin chondrification by 7.3 mm SL. Twelve or ]] predorsal bones start to chondrify posteriad by 15.8 mm SL in larvae 21 days old. Twenty four pairs of pleural ribs develop partially of cartilage and dermal origin. Comparisons with other clupeiform species stress the necessity of further research in this fish group.
Engraulis japonicus is an important commercial anchovy in the Japanese Ar- chipelago. This anchovy, katakuchi-iwashi in Japan, supports an adult and post- larval fishery since the 10th century (Hayashi, 1961; Whitehead et aI., 1988). Since the pioneering work of Nishikawa (1901), adequate descriptions of the eggs and larvae of this species have been published (Uchida, 1958; Mito, 1961a, 1961b; Fukuhara, 1983). Larval growth of reared anchovy has been described by Fukuhara (1983) and Tsuji and Aoyama (1984). Development of feeding habits, feeding mode, and feeding organs are discussed by Chiba (1956), Shen (1969), and Uotani (1985a, 1985b). Iwai (1983) described the naked neuromasts in Jap- anese anchovy larvae. Information on the osseous structure of the Japanese an- chovy is scarce and incomplete (ltazawa, 1954; Yasuda, 1960; Hayashi, 1961; Hotta, 1961; Takahashi, 1962; Nelson, 1970, 1973), and only Hayashi (1961), Suzuki and Tanaka (1979), Fukuhara (1983), Kohno and Taki (1983), and Balart (1985a) have contributed to the knowledge of its osteological development. Studies of the osteological development provide information about functional aspects of larval survival (Kohno et aI., 1983, 1984) and are tools for taxonomic and systematic works (Dunn, 1983, 1984). This paper deals with the development of median and paired fins and their supports, the vertebral column, and associated bones in Engraulis japonicus giv- ing details on their shape, ossification and meristics.
495 496 BULLETIN OF MARINE SCIENCE. VOL. 56. NO.2. 1995
MATERIALS AND METHODS
Two series of Engraulis japonicus were used in this study. The first series consisted of 101 labo- ratory-reared specimens ranging from 2.3 to 37.7 mm in notochord (NL) or standard length (SL) 0- 59 days after hatching (DAH). Specimens were reared at Nansei Regional Fisheries Research Labo- ratory, Hiroshima Prefecture, and preserved in 5% formalin. The second series consisted of 181 wild- caught specimens ranging from 1.5 to 110.6 mm SL. Localities, preservation, and staining methods were the same as described by Balart (l985a). Laboratory-reared specimens were cleared and stained after Potthoff's (1984) method. Observations and drawings were made with a Wild M5 stereoscopic microscope having a camera lucida attachment. Measurements of smaller specimens were made with a Nikon V20 profile projector combined with a Nikon SMZ6F digital counter. Larger specimens were measured with Kanol dial calipers. No correction factor was used for adjusting size changes due to shrinkage. Fin rays and pterygiophores were counted regardless of their degree of development. Counts on paired fins usually included both sides.
RESULTS Caudal Fin Complex (Figs. 1-3, Table l).-The caudal complex of E. japonicus follows the typical clupeoid pattern described by Hollister (1936), Gosline (1960, 1961, 1980), Greenwood (1968), Greenwood et al. (1966), and Monod (1968). Caudal rays supported by bones articulating with four posteriormost preural centra (cp 1-4) and by radial cartilages. Cpl vertebra with specialized neural process. Small ural centrum 1 fitted to hypural 3 and ural centrum 2 fused to hypural 2. Urostyle (according to Monod, 1968), an opened cylinder, surrounds part of notochord remnant. Urostyle closely associated with ural centrum 2. No- tochord remnant ends in opisthural cartilage which dorsally separates upper sec- ondary rays from upper principal caudal rays. Three pairs of uroneurals present: uroneural 1 anteriorly fused to cp1 conforming "pleurostyle," uroneural 2 later- ally located, and 8mall uroneural 3 placed at side of opisthural cartilage. Two epurals present, anterior one sometimes with foramen or Y-shaped. Of six hy- purals only hypural 1 separated from caudal axis and has lateral wing-like process. Six radials (=accessory cartilages of other authors) are present. Parhypural with distinct parhypurapophysis. Principal rays include 17 branched and two unbranched (1 + 9 + 8 + 1), supported by hypurals, parhypural, and some radials. Typically, median branched rays have elongated proximal bases. Secondary rays number from 8-11 upper and 8-10 lower. They are smaller and unsegmented anteriad but larger and seg- mented posteriad. Secondary rays supported by preural centra 2-4, epurals, and some radials (including opisthural cartilage). Caudal complex starts development in specimens 6.1 mm NL, 9 DAR. In wild- caught specimens, caudal complex development occurs at larger sizes (7.0 mm NL). First part of caudal support to appear is a small cartilage bud (h 1) ventral to unflexed notochord. Subsequent hypural buds form posteriad during notochord flexion. Parhypural appears consistently among II DAR specimens >7.0 mm NL. It soon connects to hypural I by temporary cartilage bridge proximally. Bridge disappears when hypural I detaches from cpt. Cartilaginous neural and haemal arches related to caudal complex develop anteriad. Raemal arches form earlier than neural arches. Flexure of notochord starts in specimens 6.2-6.9 mm NL (11- 20 DAR) and is complete in all larvae larger than 8.5 mm SL (14-20 DAR). Opisthural cartilage develops in specimens >9.2 mm SL, 20 DAR, at notochord end. This cartilage enlarges and changes from cone to oval shape. Uroneural 1 appears in bone in specimens 9.3 mm SL (20 DAR) when hypural 1-4 and parhypural ossify at their mid-portion. Center of ossification is at hypural 1 from which it spreads out dorsad and anteriad. Uroneural 2 appears distally on noto- BALART: DEVELOPMENTAL OSTEOLOGY OF ENGRAUUS 497 A
Cp2
B
C p1 c
Figure 1. Caudal skeleton of an adult Engraulis japonicus. Left lateral views. A, entire skeleton; B. C, after successive stages of dissection. Radial cartilages not shown. cp, preural centrum; e. epural; h. hypural; na, neural arch & spine; no, notochord; 0, opisthural cartilage; ph, parhypural; u. ural centrum; un, uroneural; ur, urostyle. Scales indicate 1 mm. 498 BULLETIN OF MARINE SCIENCE, VOL. 56, NO.2, 1995
Figure 2, Development of caudal fin supports in Engraulis japonicus. Left lateral views. A, 6.1 mm NL; B, 6.2 mm NL; C, 7,0 mm NL; D, 7.3 mm NL; E, 7.9 mm NL; F, 8.5 mm SL; G, 9.3 mm SL; H, 9.96 mm SL; 1,11.60 mm SL; J, 13.00 mm SL; K, 17.9 mm SL; L, 16.8 mm SL; M, 20.89 mm SL; N, 44.05 mm SL. a. radial cartilage; ha, haemal arch & spine. For other abbreviations, see Figure I. Stippled areas, cartilage. Open areas, ossifying. Scales indicate 0.25 mm. BALART: DEVELOPMENTAL OSTEOLOGY Of' ENGRAULIS 499
CJ) ~ 12 a:: ..... -. .... - ...OQ]!).0 ~-illIXXD o • «-oJ •• C 4 • 0 ::> • 0 0 « 0 __ -: I I I I I I \' I I I I. 5 9 13 17 21 25 30 50 70 90 STANDARD LENGTH (mm) Figure 3. Development of caudal rays in Engraulis japonicus. Above, upper rays; bottom, lower rays. Solid circles, principal rays; open circles, secondary rays. chord when hypural ossification reaches hypural 6. Preural centrum 1 and ural centrum 2 appear in bone before ural centrum 1, but at same age (20 DAH). Uroneural I anteriorly overlaps cpl, until ca. 13 mm SL when two bones fuse. Ural centrum 2 appears in bone at 11.6 mm SL and is attached to hypural 2. Large ural centrum 1 abuts hypural 3 and 4. Ural centrum 1 becomes relatively smaller losing its connection to hypural 4. At this time one epural cartilage present (e2 ?), but soon (13.0 mm SL) other two epurals develop. The anterior epurals 1 and 2 fuse together ventrally at first, while ossification is taking place on their mid-portion. Fusion results in rod-like anterior epural (e 1 + 2) sometimes having foramen, or being Y-shaped. Onset of epural fusion and ossification may continue to 25 mm SL. By 11.6 mm SL (20 DAH), small bud present at future base of specialized neural process of cpl. Only base originates from cartilage, remainder of neural process is membranous ossification. Small uroneural 3 appears by 13.0 mm SL near tip of notochord associated with opisthural cartilage. Small and trapezoidal preural centrum 2 finishes its ossification after cp 3-4. Neural and haemal spines associated with cp 1-4 start to ossify before centra, except for specialized neural process of cpl which starts to ossify after centrum. Hypural 2 acquires its rod-like shape early. Membranous ossification ventral to hypural 3 provides articular area for elongating ray base of upper median ray. Formation of radial cartilages begins by 15.0 mm SL and completed by 20.0-30.0 mm SL. First to develop were radial cartilages al and a2 close to parhypural and preceding Table I. Sequence of finray development for the various fins in the laboratory-reared Engraulis japonicus (I = first; 4, 5, 6 = last) Beginning Beginning Completed Beginning Completed Fin development segmentation segmentation branching barnching Caudal (principal rays) I I Caudal (secondary rays) 4 3 Dorsal 2 2 2 2 3 Anal 3 4 3 2 4 Pelvic 5 5 3 2 2 Pectoral 6 6 4 3 5 500 BULLETIN OF MARINE SCIENCE. VOL. 56. NO.2. 1995 haemal spine. Then cartilages associated with hypurals 5 and 6 (a3-4) and finally those supporting posteriormost ventral secondary rays located between cartilages al-2 (a 6) develop. Number of caudal rays plotted against SL in Figure 3. Caudal fin is second fin to develop rays which appear in bone before or at early notochord flexure. Small- est specimen with two rays is 6.2 mm NL (11 DAH). Full complement of principal rays present in specimens >8.0 mm SL (11-20 DAH). Development of principal rays starts medially, new rays being added posteriad and anteriad (dorsad and ventrad during mid-flexion). Segmentation evident in specimens over 7.5 mm NL (11 DAH), and begins in both dorsal and ventral rays proceeding to the middle rays. Branching of rays occurs between 15.0 and 18.0 mm SL (Fukuhara, 1983). Secondary rays appear later, by 10.0 mm SL (20 DAH). Smallest specimen with secondary rays has two, which like principal rays, develop first ventrally and then dorsally. Both dorsal and ventral secondary rays added anteriad. Ventrad second- ary ray segmentation evident by 13.7 mm SL (20 DAH) and dorsad segmentation by 15.0 mm SL (21 DAB). Half of smaller anterior secondary rays remain un- segmented to 100 mm SL. Segmentation follows formation pattern, anteriad. Number of secondary rays increases with length, exceeding number of principal rays in some specimens. Full complement of secondary rays reached by 18.2- 23.0 mm SL. Dorsal and Anal Fin Skeletons (Figs. 4-8, Table 1).-Basic arrangement of dorsal and anal fin skeletons in E. japonicus follows teleostean plan described by Lind- sey (1955). Large and plate-like anteriormost dorsal proximal radial is associated with two rays through one distal radial (drl). Between this distal radial and one serially connected to 2nd proximal radial, there is another distal radial (sdr) which seems to have definitely lost its connection to first pterygiophore and which is also articulated with one ray. Here this distal radial is called "supernumerary" because it develops after other distal radials present. Anterior end of anal fin skeleton also exhibits modification in its serial arrangement. There is one more ray than pteryg- iophores so relationships between anterior 4 or 5 elements depart from serial association described by Lindsey (1955). Dorsal fin skeleton possesses 14-16 soft rays, 14-16 distal radials, and 13-15 proximal radials. Most common dorsal formula (ray + distal radial + proximal radial) is 15 + 15 + 14. First two (rarely three) rays unbranched and anteriormost ray shorter than posterior rays. One to two very small and unsegmented raylets may be present in front of first dorsal ray, which are not included in current counts. Anal fin skeleton exhibits 17-19 soft rays, 16-18 distal radials, and 16- 18 proximal radials, with most common anal formula being 18 + 17 + 17. All but somewhat smaller anterior ray branched. One small unsegmented raylet may be present in front of first anal ray. As in dorsal fin, anal fin has stay bone located posteriorly. Anteriormost anal proximal radial has small cartilaginous projection directed forward (aap) at its ventral end. This species lacks median radials. Dorsal fin supports start to develop by 9 DAH in specimens >6.2 mm NL, with formation of mainly pro-cartilaginous dorsal anlagen. Chondrification takes place at posteriormost proximal radials. Subsequent proximal radials form anteri- ad. Posterior distal radial cartilages appears first, with new radials being formed mainly anteriad. Full complement of proximal radials present consistently at > 11.0 mm SL (20 DAH). Note at this stage rod-like shape as well as size of first proximal radial. Distal radial number reaches that of proximal radial number by 12 mm SL. Development of supernumerary distal radial somewhat variable, oc- BALART: DEVELOPMENTAL OSTEOLOGY OF ENGRAULIS 501 rl r10 C V E F ;r3 , ar , drl0 / rl pr2 B Figure 4. Dorsal fin skeleton of an adult Engraulis japonicus. A, left lateral view of the dorsal fin support; B, frontal view of first pterygiophore and associated rays; C, posterior view of first ray and serial distal radial; D, E, left lateral and posterior views of the 3rd pterygiophore and serial ray; F, posterior view of the 10th ray and serial distal radial. ap, anterior process; ar, anterior raylet; dr, distal radial; Ik, lateral keel; pr, proximal radial; r, ray; sb, stay bone; sdr, supernumerary distal radial. Scales indicate I mm. cUffing as early as 14.6 mm SL, but most commonly attained in specimens larger than 17.0 mm SL (consistently past 27 DAH). Anterior process of first proximal radial begins formation as cartilage. Completion and enlargement reached through membrane ossification. Ossification starts first in anterior proximal radials and proceeds posteriad. Same ossification pattern observed in distal radials. Specimens ca. 100 mm SL show cartilage remnants especially in articular surfaces and pos- terior distal radials. Stay bone originates from the posteriormost proximal radial as small rod-like cartilage outgrowth (sb) by 13.7 mm SL. It elongates posteriad mainly through dermal ossification remaining separated from proximal radial by 502 BULLETIN OF MARINE SCIENCE. VOL. 56. NO.2. 1995 Figure 5. Development of dorsal fin supports in Engraulis japonicus. Left lateral views. A, 6.2 mm NL; B, 6.2 mm NL; C, 7.9 mm NL; D, 9.4 mm SL; E, 11.5 mm SL; F, 13.6 mm SL; G, 17.8 mm SL; H, 20.9 mm SL; I, 24.5 mm SL. dfa, dorsal fin anlagen; pc, procartilage. For other abbreviations, see Figure 4. Stippled areas, cartilage. Open areas, ossifying. Scales indicate 0.25 mm. cartilaginous band. In adult anchovies stay observed articulated to posteriomost proximal radial. Dorsal ray development depicted in Figure 6A (bottom) and is function of fish length. Dorsal fin first fin to develop rays. Rays appear in bone in posterior area of dorsal fin anlagen. Rays first seen in 6.9 mm NL 9 DAH (6 rays), specimen and larvae larger than 6.2 mm NL, 11 DAH, have some dorsal fin rays. Subse- quent rays form anteriad. Full complement evident by 11.5 mm SL (from 20 DAH). Segmentation observed by 13.0-16.0 mm SL (Fukuhara, 1983), after full complement of rays present, starting from anteriormost and proceeding posteriad. Branching of rays begins by 20.0 mm SL, with completion lasting to 25.0 mm SL (Fukuhara, 1983). One small unsegmented raylet appears from 21 DAH whereas other unsegmented raylet develops among 40 DAH specimens (over 18.7 mm SL) or never at all. Anal fin supports start development by 9 DAH among specimens over 6.2 mm NL, in wild specimens it occurs in sizes greater than 7.8 mm NL. At this stage anal fin anlagen is located behind anus. Subsequently, chondrification takes place in central proximal radials with new elements being added anteriad and posteriad. Distal radials appear from 7.1 mm NL (11 DAH) as distinct structures near mid- region of anal fin. New distal radials chondrify anteriad and posteriad. Posterior distal radials complete chondrification earlier than anterior ones. Figure 6B (above) illustrates development of number of pterygiophores as related to fish length. Full complement of proximal radials attained by 8.0-9.5 mm SL (14-20 DAH). Adult comp:iement of distal radials occurs by 10.3-13.6 mm SL (20 DAH). After full complement of proximal radials reached, anteriormost proximal radial BALART: DEVELOPMENTAL OSTEOLOGY OF ENGRAUUS 503 16 CX)~ &mO~(ll)@)e_ ._~ ~·r·~(&of - ii @) ~~~~•• e() •• -- • - •• ~ . • • 12 ··.0•• • 0 -"1B 0 8 .:-N 4 @mo o DR A • PR o ______~ __ \I I I • 16 ...... - - -.-.- - . .. VJ .•-• .. . I- 12 •••• Z •• • W 8 ••• ~ -• W • -J 4 - W o ••• I I I ,I I I I I I I Z 20 - l.L ••• ~~@@ 16 • @) ~li • @o~,,~:i~.~ ~@&: @ ••• 0 .00 l.L 12 ••• 0 •.·00 0 0 o 8 ·-.8 B 4 ·cJ ODR a: ·PR W m 0 I I \1 I I I I ~ 20 --. • -. .. ::J • •• ...... --- ....-- .. .- .. -... Z .. -. - . • • • • •••• • •• • 16 •• • •••• --• • ••• • 12 • • •• 8 -• 4 -• ·R o j•• ..,_._ •..•.•••_ ••••••_-'-_ •••.••••_--"' "___ •.•••••_ .••••• •..•.••••••• I , I I ~ 9 13 17 21 25 ~O I 50 70 90 STANDARD LENG TH (mm) Figure 6. Development of pterygiophores and rays of dorsal fin (A) and anal fin (B) in Engraulis japonicus. DR, distal radial; PR, proximal radial; R, ray. becomes biggest but does not develop posterior process which characterizes pos- terior proximal radials. Ossification of proximal radials proceeds posteriad. Distal radial 3 first to ossify; ossification then proceeds anteriad and posteriad. Anterior projection of first anal proximal radial evident >27.4 mm SL (51 DAH) and 504 BULLETIN OF MARINE SCIENCE, YOLo 56, NO.2. 1995 Figure 7. Development of anal fin supports in Engraulis japonicus. Left lateral views. A, 6.2 mm NL; B, 6.9 mm NL; C, 7.9 mm NL; D, 10.0 mm SL; E, 13.0 mm SL; F, 19.2 mm SL; G, 24.8 mm SL; H, 37.7 mm SL. a, anus; aap, anterior process; afa, anal fin anlagen; dr, distal radial; pc, procar- tilage; pr, proximal radial; sb, stay bone; r, ray. Stippled areas, cartilage. Open areas, ossifying. Scales indicate 0.25 mm. remains cartilaginous. Stay bone originates as small rod cartilage close to poster- iormost proximal radial at about 13.0 mm SL. Later fuses to proximal radial and elongates posteriad. It ossifies remaining separated from proximal radial by car- tilaginous band. Figure 6B (bottom) shows development of number of anal rays as related to fish length. Anal fin third fin to develop rays. Rays appear in bone among 11 DAH specimens over 7.1 mm NL shortly after anlagen chondrification. As with pterygiophores, anal rays form first near mid-region. New rays added anteriad and posteriad. Number of rays soon reaches pterygiophore number, not attaining full complement until small first segmented ray forms, as early as 20 DAH (> 10.4 mm SL) but consistently present greater than 15.7 mm SL from 21 DAH. This anteriormost ray remains unsegmented longer, and easily overlooked. Seg- mentation evident by 14.0-20.0 mm SL starting from second ray posteriad. Branching attained by 20.0-28.0 mm SL (Fukuhara, 1983). Small unsegmented raylet may form anteriorly by 19.0-30.0 mm SL (36-55 DAH). As development proceeds, relative positions of dorsal fin, anal fin, and pelvic fin supports change as well as their proportional lengths. From Figure 8 (top), it is clear that dorsal fin supports undergo bigger migration during 8-30 mm SL than anal fin supports. This dorsal migration partly done by anterior enlargement of first proximal radial, thus moving anteriormost point far forward relative to vertebrae. Figure 8 (bottom) indicates that dorsal and anal fin support lengths are very close almost throughout development, relative to vertebrae. Pectoral Fin Skeleton (Figs. 9-11, Table 1).-Pectoral girdle consists of posttem- poral, supracleithrum, cleithrum, coracoid, scapula, mesocoracoid, four radials (=actinosts), and outer series of small distal radials (usually 9 in number) asso- BALART: DEVELOPMENTAL OSTEOLOGY OF ENGRAUUS 505 31 .--... ..-.- • ••• •• • • .- . • o - . o 0 o • '"'a> 11 o .0., 00 ., o· CO o 0<01 0 • ex> L- • • ..c .em-=> _ 0.:)1. • • o•• 000 ~.. 0 e 9 ()k). •• •• CO> L- 10 20 30 60 STANDARD L ENG TH Figure 8. Migration of fin supports (top) and development of fin supports length (bottom) in En- graulis japonicus. Displacement of fin support indicated by the centrum reached by the anterior end of dorsal and anal fin supports, and posterior edge of basipterygium of the pelvic fin respectively. Length of fin supports measured by the number of centra (to the nearest 0.5 centrum) underlying or overlying it. Open circle, dorsal fin support. Solid circle. pelvic fin support. Solid square, anal fin support. 506 BULLETIN OF MARINE SCIENCE, VOL. 56, NO.2, 1995 ciated with ray bases. Pectoral fin rays, 14-17 (commonly 15-16), supported by scapula and radials. Laterally, axillary scale supported by a scapula process. Post- cleithrum absent throughout development in this species. Posttemporal joined to neurocranium through two projections: well developed upper wing and filiform lower process projecting mesially. Posttemporal and su- pracleithrum somewhat modified by grooves and enclosed tubes carrying sensory line branch. Ligament runs from parapophysis of vertebra 1 to supracleithrum. Cleithra joined to one another by ventrally located symphysis. Expanded lower portion of cleithrum supports scapula and coracoid. Mesocoracoid supported by scapula and coracoid and distally attached to cleithrum, Two foramina in front of lower portion of mesocoracoid. Scapula foramen surrounded only by scapula. Proximal radials differ in size as well in shape, with longest one being innermost. First proximal radial (propterygium) enlarged and fused to first ray base. Distal pectoral radials decrease in size outward, not having one-to-one relation to rays; outer rays are the smallest ones. Pectoral fin first fin to develop_ Typically, pectoral bud appears few hours to two DAR in specimens :>2.8 mm NL, though in field specimens it is evident at smaller length such as 2.6 mm NL (probably artifact due to greater shrinkage than in laboratory-reared larvae). Chondrification, however, starts later. Both pec- toral buds appear positioned near mid-height, behind head. After yolk-sac deple- tion, petoral buds become located ventrally (ca. 3-4 DAR). Pectoral bud consists of rudimentary coraco-scapula cartilage to which radial plate later joins. Very thin dermal finfold develops surrounding free border of radial plate cartilage. By 5.2 mm NL (7 DAH), chondrification well established. Both left and right coraco- scapula cartilages fused ventromedially forming single cartilage block. Laterally triradiated coraco-scapula shifts to L-shape because of growing posterior coracoid process. Needle-like cleithrum has no connection to primary shoulder. Gradually a conspicuous notch forms at anterior margin of coraco-scapula cartilage which later (20.9 mm SL, 27 DAH), by border closing, becomes coracoid foramen. Postcoracoid foramen and scapula foramen form in different fashion, their pres- ence being noticed by 8.5 mm SL (ca. 14 DAR) and 11.3 mm SL (ca. 20DAH). Dorsally, coraco-scapula cartilage develops extension (scapula process) directed backward which will support axillary scale. Scapula and coracoid differentiate through ossification process which occurs by 24.0 mm SL (51 DAR) beginning in many centers and finally leaving only cartilage band between them. Scapula foramen retained completely on scapula. Radial plate cartilage exhibits median crevice by 20 DAR (6.2-8.4 mm NL, SL), though all three crevices already formed at 11.0 mm SL (20 DAR). Crevices elongate reaching outer margin of blade cartilage and thus separating it into four proximal radials by 36 DAB. This process of formation occurs gradually follow- ing inner-outer sequence, becoming detached first innermost proximal radial. Ra- dials differ strikingly in size and shape, second and third first to ossify and out- ermost last. Small propterygium forms from radial plate cartilage among larger 27 DAR specimens prior to formation of proximal radials. It first joins and later fuses to innermost ray and may be considered first element of distal radials. At least three or four distal radials (the inner ones) are detached fragments of radial plate, while outennost seems to be autogenous. Supracleithrum ossifies earlier than posttemporal in specimens between 11.0- 13.0 mm SL (20 DAH). Both structures look bar-shaped. At beginning, only upper process of postternporal defined, but by 20.9 mm SL (27 DAR) lower process ossifies also. Cleithrum becomes stout and develops broad lower wing as devel- opment proceeds. Supracleithrum enlarges laterally through scale-like expansions. BALART: DEVELOPMENTAL OSTEOLOGY OF t;NGRAUUS 507 A c upt/ Figure 9. Development of pectoral fin supports in Engraulis japonicus. Left lateral and ventral views. A, 5.2 mm NL; B, 6.5 mm NL; C, 11.3 mm SL; D, 17.3 mm SL; E, 20.9 mm SL; F, 24.5 mm SL; G, 27.4 mm SL. Axillary scale displaced posteriad. ap, anterior process; ax, axillary scale; c, c1eithrum; cf, coracoid foramen; cs, coraco-scapula; f, finfold; Ipt, lower process; or, distal radial; pf, postcoracoid foramen; pp, posterior process; pr, propterygium; pt, posttemporal; r, radial; rp, radial plate; s, supra- cleithrum; sf, scapula foramen; sp, scapula process; upt, upper process. Stippled areas, cartilage. Open areas, ossifying. Scales indicate 0.25 mm. 508 BULLETIN OF MARINE SCIENCE. VOL. 56. NO.2, 1995 c B or Figure 10. Development of pectoral fin supports in EngrauLis japonicus. Dorsal views. A, 23.4 mm SL; B, 26.1 mm SL; C, 27.4 mm SL. m, mesocoracoid. For other abbreviations, see Figure 9. Stippled areas, cartilage. Open areas, ossifying. Scales indicate 0.5 mm. Tiny unossified axillary scale joined to scapula process forms by 24.5 mm SL. It becomes evident by 27.4 mm SL (5] DAH) through alizarin absorption. Formation of mesocoracoid occurs after coracoid foramen formation in speci- mens over 23.0 mm SL (36 DAH). Mesocoracoid begins as rod-like outgrowth of coraco-scapula cartilage anterodorsally directed. It elongates conforming car- ti]age bar which extends up and reaches anterodorsa] cleithrum border. Ossifica- tion spreads from 24.5 mm SL among 5] DAH specimens. Number of pectoral rays shown in Figure ]] (top) as related to fish length. Pectoral fin fifth fin to develop rays which ossify in finfo]d following inner-outer (dorsoventrad) sequence. Smallest specimen bearing pectora] rays (2 left and 3 right rays) is ]7.5 mm SL, 40 DAH. Larger but younger larvae (from 27 DAH) • 16 • • •• • . -- - -.-. • • • •••• Cf'J 12 • >- ••• •- •• I ::.~.... L. i A ". c D i i i i j \ \, . .! \) J , pb \m -.- - /- . , '-"Y\'" ~ - ...~l ~"" - B E F ~ b f ~ Figure 12. Development of pelvic fin supports in Engraulis japonicus. Ventral and left lateral views. A, 12.8 mm SL; B, 13.7 mm SL; C, 15.0 mm SL; D, 17.3 mm SL; E, 20.9 mm SL; F, 24.5 mm SL. b, basipterygium; f, finfold; m, metapterygium; pb, pelvic bud; ps, pelvic scute. Stippled areas, car- tilage. Open areas, ossifying. Scales indicate 0.25 mm. arches, similar in shape at beginning. Complete count of neural and haemal arches, as well as parapophyses, attained by 18.2-19.3 mm SL (27-30 DAH), same oc- curring at >19.0 mm SL among wild specimens. Ossification of neural and hae- mal arches first begins on posterionnost elements, but shortly after new center of BALART: DEVELOPMENTAL OSTEOLOGY OF ENGRAUUS 511 5 10 15 20 25 30 35 40 I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I 1 I 1 I I 1 I II 1 1 I ~ :~~~ 111111111111111111 l~~~~ o·I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I 1 I I 5 10 15 20 25 30 35 40 Figure 13. Schematic representation of vertebral column, predorsal bones, and pleura] rib development in Engraulisjaponicus. A, 7.9 mm NL; B, 10.2 mm SL; C, ]3.0 mm SL; D, 14.1 mm SL; E, 16.8 mm SL; F, ]8.2 mm SL; G, 27.4 mm SL; H, 44.1 mm SL. Stippled areas, cartilage. Open areas, ossifying. Scale represents vertebrae number. (On]y 44 vertebrae are figured; for cauda] end, see Fig. 2.) 512 BULLETIN OF MARINE SCIENCE. VOL. 56. NO.2, 1995 n no G n--:::?"pd '1/ P C2 t(6 Figure 14. Development of the first, 2nd, and 3rd abdominal centra and associated bones in Engraulis japonicus. Left lateral views. A, 11.4 mm SL; S, 13.2 mm SL; C, 15.0 mm SL; D, 16.8 mm SL; E, 19.2 mm SL; F, 24.5 mm SL; G, 27.4 mm SL; H, 37.7 mm SL. c, centrum; ec, epicentral rib; ecr, BALART: DEVELOPMENTAL OSTEOLOGY OF ENGRAUUS 513 ossification above and below dorsal and anal fin supports appears spreading both anteriad and posteriad. Later, ossification also starts from first neural spine pro- ceeding posteriad. Ossification of individual arches and spines starts near middle area and then spreads in all directions on anterior vertebrae. On medial abdominal and most of caudal vertebrae, ossification starts little above base of arch and soon after on proximal end of spine proceeding distad. Arch bases remain cartilaginous longer in caudal arches. Ossification of centra (excluding caudal complex) ob- served from 12.2 mm SL (20 DAH) in both laboratory-reared and wild larvae. Apparently first formed centra 7-15, proceeding anteriad and posteriad. Ossifi- cation of two or three anteriomost centra appear in bone as independent center following posteriad sequence. Dorso-ventral gradient of ossification not apparent in centra formation except for last preural centra (see CAUDAL FIN COMPLEX). Complete count of centra attained by 16.8 mm SL, 27 DAH. Most of abdominal arches not yet formed when centra ossification takes place. Anteriormost centrum transitorily longer than following centra until ca. 3~0 mm SL. At beginning, all parapophyses somewhat globular cartilages except anteriormost and strikingly elongated. As development proceeds, they become more or less enlongated ac- cording to position: nearer to caudal vertebrae they are more elongated (and hae- mal arch-like). When neural postzygapophyses appear, they develop anterodorsal outgrowth that among caudal vertebrae reaches neural spine, and so conform neural foraminal bridge (nomenclature according to Potthoff and Kelley, 1982). In caudal vertebrae, one or two foramina enclosed in bridge. In abdominal ver- tebrae, pseudoforamen or none developed. Following similar pattern, haemal postzygapophyses develop foraminal bridge in posterior caudal vertebrae, but re- main quite separated from haemal spine at anterior caudal vertebrae. Predorsal bones (=supraneurals) begin to chondrify from 15.8 mm SL among 21 DAH specimens and by 15.0 mm SL in wild specimens. First predorsal car- tilage appears in front of first neural spine, new cartilages being added posteriad. Complete count attained by 18.2-23.4 mm SL (27-36 DAH) and by 25.0 mm SL in wild specimens. Ossification follows formation pattern, from anteriormost cartilage proceeding posteriad. In individual predorsal cartilages, elongate center of ossification near middle spreads both distad and proximad. Later membrane ossification develops along their anterior margin. Pleural ribs begin to chondrify from 15.8 mm SL (21 DAH) but at bigger sizes (21.6 mm SL) among wild specimens. First pleural rib supported later by par- apophysis of centrum 3. Addition of more pleural ribs in posterior direction. But soon, from centrum 13 or 14, just above basipterygia, they also start to develop posteriad. Pleural ribs elongate both proximally and distally, and reach serial parapophysis. Complete count of 24 pleural ribs attained by 20.9-23.4 mm SL (27-36 DAH) and by 25.0 mm SL among wild specimens. Ossification starts first on first pleural rib and then proceeds posteriad. In individual pleural ribs, ossifi- cation starts in middle spreading out proximad and distad. Pleural ribs never develop in centra 1 and 2. Development of epicentral, epicranial and epimeral ribs are not described in this work. f- epicranial rib; em, epimeral rib; ep, epipleural rib; n, neurocranium; na, neural arch & spine; no, notochord; npo, neural postzygapophysis; npr, neural prezygapophysis; pa, parapophysis; pc, postcra- nial accessory bone; pd, predorsal bone; pi, pleural rib. Stippled areas, cartilage. Open areas, ossifying. Scales indicate 0.25 mm. 514 BULLETIN OF MARINE SCIENCE, VOL. 56, NO.2, 1995 no A Figure 15. Development of the 26th, 27th (first caudal), and 28th vertebrae in Engraulis japonicus, Left lateral views. A, 11.3 mm SL; B, 13.2 mm SL; C, 16.8 mm SL; D, 19.2 mm SL; E, 27.4 mm SL; F,44.1 mm SL. ha, haemal arch & spine; hpo, haemal postzygapophysis; hpr, haemal prezygapoph- ysis. For other abbreviations, see Figure 14. Stippled areas, cartilage, Open areas, ossifying, Scales indicate 0.25 mm. DISCUSSION Among the Clupeiformes, formation and ossification of the caudal fin supports proceeds from the first hypural posteriad (dorsad after notochord flexure) and anteriad. Epural cartilages are the last ones to form and ossify (Ramanujam, 1929; Hollister, 1936; Gwyn, 1940; Hayashi, 1961; Monod, 1968; Houde et aI., 1974; Suzuki and Tanaka, 1979; Johnson and Loesch, 1983). Only Brevoortia smithi (Houde and Swanson, 1975) starts ossifcation from the parahypural, which should be considered a mi:nor variant of the same theme. Observations on the sequence of formation and segmentation of caudal rays are scarce in Clupeiformes. For- mation begins with the middle principal rays proceeding ventrad and dorsad, as in most teleost fishes. The pattern of segmentation follows an opposite sequence, from upper and lower principal rays toward the middle, later proceeding anteriad with the secondary rays (Houde et aI., 1974). In Clupeiformes the fusion of caudal elements is an exception rather than the rule (Ramanujam, 1929; Hollister, 1936; Gwyn, 1940; Hayashi, 1961; Houde et aI., 1974; Richards et aI., 1974; Houde and Swanson, 1975). Fusion of hypurals is absent in E. japonicus but a temporary cartilaginous bridge is found between the hypural 1 and the parhypural (and some teratological cases observed in reared specimens). The ural centrum 1 never fuses to the preural centrum 1. The uro- BALART: DEVELOPMENTAL OSTEOLOGY OF ENGRAUUS 515 c \ hpr D Figure 16. Development of the 39th, 40th, and 41st vertebrae in Engraulis japonicus. Left lateral views. A, 13.2 mm SL; B, 16.8 mm SL; C, 19.2 mm SL; D, 24.5 mm SL; E, 27.4 mm SL; F, 44.1 mm SL. For abbreviations, see Figures 14 and 15. Stippled areas, cartilage. Open areas, ossifying. Scales indicate 0.25 mm. neurals remain as distinct structures from the beginning. The same occurs in HarenguLa jaguana (Richards et aI., 1974) and ALosa sapidissima (Johnson and Loesch, 1983). However, the contrary is described for Jenkinsia, a dussumieriid (Hollister, 1936~ Cervig6n and Velazquez, 1978; Patterson and Rosen, ]977). CLupea harengus (Ramanujam, 1929), like Anchoviella choerostoma and Haren- guLa sp. (Hollister, ]936), develops an ossified third (uppermost) ural centrum which fuses to ural centra 1 and 2, and becomes a small segment connected to hypural 2 in the adult fish. The description of Regan (1910) and Monod (1968) however, shows the presence of two ural centra as in most clupeoids. Fusion thus occurs between ural centra 2 and 3 as described by Hollister (1936). The epural number ranges from 1 to 3 within the Clupeiformes. As shown for E. japonicus, the anteriormost epural represents a fusion of two. The same is true for Anchoviel- La choerostoma (=Anchoa choerstoma) (Hollister, 1936). Among clupeid fishes, Sprattus sprattus has a compound epural with a visible suture (Monod, 1968). In Sardinella anchovia the anterior epural represents a fusion of two elements (Hol- lister, 1936; Monod, 1968). However, epurals may remain unfused throughout development in other Clupeiformes. A remarkable opisthural cartilage is present in E. japonicus. This structure had been neglected in most descriptions, despite Whitehouse's (1910) assessment in Sardina pilchardus and Engraulis encrasicholus within the Clupeiformes, until Monod's work (1968). Opisthural cartilage had also been recorded only among other lower teleosts like Salmoniformes, Elopiformes, and Ostariophysi (Monod, 1968; Roberts, 1984). Whitehouse (1910) regarded the opisthural cartilage as a 516 BULLETIN OF MARINE SCIENCE. VOL. 56, NO.2, 1995 vestige of the neural or haemal arches while Monod (1968) held that it may be the vestige of a hypural element. Functionally, this cartilage resembles a caudal radial cartilage. It provides support to fin rays as well as to muscles acting in fin ray movement (Monod, 1968). It is possible to find neural arch formation either before or after centra ossifi- cation depending on the region of the vertebral column, as seen in E. japonicus and probably in Brevoortia smithi (Houde and Swanson, 1975). The pattern of formation of dorsal and anal fins and fin supports is unclear at the present within the Clupeiformes. It should be stressed that distal radials were observed to develop separated from and generally after the serial proximal radials, corroborating the observations of Kohno and Taki (1983). The information avail- able for ossification of dorsal and anal rays illustrates the necessity of further research in this fish group. E. japonicus exhibit dorsal fin ray ossification begin- ning posteriorly and proceeding anteriad like in Harengula jaguana, a clupeid fish (Houde et aI., 1974). Sreekumari (1976) and Caddell (1988), however, found dorsal elements differentiating posteriad in Anchoa spp. and Stolephorus zollin- geri. For the anal fin, Anchoa spp. and E. japonicus, show fin ossification begin- ning near the mid-region and proceeding anteriad and posteriad (Caddell, 1988; present work); in Harengula jaguana (Houde et aI., 1974) ossification seems to proceed mainly anteriad from an undetermined point of the anal fin, while Sree- kumari (1976) described anal rays ossifying first anteriorly and proceeding pos- teriad in Stolephorus zollingeri. The presence of an enlarged first dorsal proximal radial is widely recorded among teleost fishes. This observation suggests an early fusion of at least two pieces of cartilage within the Clupeiformes (Phillips, 1942; Joshi and Bal, 1953; Hayashi, 1961; Yanez-Arancibia and Ruiz, 1978). However, the observations in E. japonicus show the first proximal radial takes origin only from one element. The same fact (but involving a quite different morphology) had been shown in Pleuronectiformes (Balart, 1985b). The "supernumerary" dorsal distal radial (sdr) suggests various interpretations. This radial is that formerly for the first or second proximal radial before they fused into a single large element, and so, the radial would be not supernumerary at all. There are, however, two objections: it was not observed such fusion of anterior dorsal proximal radials; sdr would develop following the general se- quence of chondrification and not after the other distal radial. Another hypothesis more in agreement with the observed developmental osteology is sdr is not a vestige but a neoformation probably related to the need of greater mobility without restraining the stiffness of the anterior end of the dorsal fin. Fin migration, that more or less dramatic change of position of dorsal, anal and pelvic fins relative to myomeres or vertebrae as development proceeds, is a phenomenon of wide occurrence among Clupeiformes, Elopiformes, and Anguil- liformes (Moser, 1981; Castle, 1984; Leiby, 1984; McGowan and Berry, 1984). Its functional significance is unknown, though Moser (1981) suggests a possible relation to tail beat thrust during larval stage. Within the Clupeiformes, the extent of the fin migration varies with the fin as well as with the particular species (Ta- ble 2). The basic number of pectoral proximal radials appears to be four within the Clupeiformes (Starks, 1930; Phillips, 1942; Chapman, 1944a, 1944b, 1948; Cer- vig6n and Velazquez, 1978; Yanez-Arancibia and Ruiz, 1978; Yabumoto and Uyeno, 1981; Whitehead and Teugels, 1985), though a trend to reduce the number to three radials is observed in Denticipitidae (Greenwood, 1968), Coilinae (Joshi and Bal, 1953; pers. observ. in Coilia nasus) within Engraulididae, and Etrumeus BALART: DEVELOPMENTAL OSTEOLOGY OF ENGRAULIS 517 Table 2. Fin migration in some c]upeoid fishes, measured by displaced number of centra or myomeres Number of displaced centra or myomeres Dorsal Anal Pelvic NUSUTL range fin fin fin (mm) Reference Engraulididae Engraulis japonicus 9-11* 3--4 +] 8.0-100.7 SL Present work E. ringens 4 5.0-25.0 NL, SL Orellana and Ba]bontfn (1983) E. mordax 3 Moser (1981) Cupeidae Alosa sapidissima 13 10 8.0-24.0 SL Johnson and Loesch (1983) A. mediocris 11 ]--4 11.0--40.0 TL Mansueti (1962) A. pseudoharengus 6 4 12.4-32.2 SL Norden (1967) Brevoortia smilhi 12 9 6.1-22.7 NL, SL Houde and Swanson (1975) Sardina pilchardus 10 5-6 0-1 25.0--40.0 TL Lebour (1921) Opisthonema oglinum 10 4 15.5-54.0 SL Richards et al. (1974) Clupea harengus 7-8 6-7 1-2 26.5-35.0 TL Lebour (1921) C. bentincki 3--4 6.5-25.0 NL, SL Orellana and Balbo1tfn (1983) Harengula jaguana 6 2 14.0-16.4 SL Houde et al. (1974) Sardinops sagax musica 5 7.4-25.0 SL Orellana and Balboltfn (]983) Sprallus sprallus 4-5 4-5 25.0-32.0 TL Lebour (1921) Sardinella jussieu 4 4.2-22.2 NL, TL Bensam (1973) * To make this data comparable. 2-3 should be subtracted (other data take the position of the first fin ray as a reference instead of the anterior position of the Isr proximal radial). teres (pers. observ.) within Dussumieriinae. The presence of distal radials is com- mon rather than unusual (Starks, 1930; Cervig6n and Velazquez, 1978; Yafiez- Arancibia and Ruiz, 1978; Yabumoto and Uyeno, 1981; Whitehead and Teugels, 1985), and even a third series (median radial) has been reported in some species (Cervig6n and Velazquez, 1978), The coracoid develops two processes during ontogeny in E. japonicus. The posterior process seems to develop in all teleosts but retains a late importance, even if only among lower teleosts (Swinnerton, 1905; Vogel, 1909; Starks, 1930; Roberts, 1984; present work). The anterior process acquires noteworthy propor- tions mainly among higher teleosts (Houde and Potthoff, 1976; Potthoff, 1980; Potthoff and Kelley, 1982; Kohno et aI., 1983, 1984; Potthoff et aI., 1984; Paine and Balon, 1984; Balart, 1985b; Matsuoka, 1985). Goodrich (1922) was the first to notice a median fusion of both left and right coraco-scapula cartilages, a larval condition he thought to be restricted to Clupea (=Clupea, Sardina, and Sprattus) and related genera. We now know it has wider occurrence since it has been found in the neotonic Sundasalangidae and leptocephalus larva of Elops by Roberts (1984) and here for Engraulis. Goodrich saw this condition as a specialization to strengthen the support of the pectoral fins before complete development of the dermal girdle. The propterygium (uppermost distal cartilage, scapular radial, upper cartilagi- nous pectoral radial of some authors) normally associated with, if not fused to, the uppermost ray develops before proximal radial detachment in most teleost fishes (Swinnerton, 1905; Goodrich, 1922; Kohno et aI., 1983; Kohno and Taki, 1983; Balart, 1985b; Matsuoka, 1985; present work) except for Scomber japonicus (Kohno et aI., 1984). There are three views of its origin. 1) The propterygium originates from the blade cartilage in the Clupeiformes (Goodrich, ]922: figs. 5- 518 BULLETIN OF MARINE SCIENCE, VOL. 56. NO.2, 1995 6; Kohno and T.:tki, 1983; present work), in the gonorynchifonn Chanos chanos (Taki et aI., 1986), the salmonid Oncorhynchus keta (Kohno and Taki, 1983) and at least in one pleuronectiform fish (Balart, 1985b). 2) Potthoff and Kelley (1982) described the propterygium originating from the scapula cartilage in Xiphias glad- ius. 3) Matsuoka (1985) suggests an autogenous origin above the cartilage blade in Pagrus major. The postcleithra within engraulidid fish is absent (Chapman, 1944a, b; Joshi and Bal, 1953; Gosline, 1980; present work). However, in clupeids, its presence has been reported as scale-like structures in some species (Etrumeus micropus, Chapman, 1948; Sardinops caerulea. Phillips, 1942; Denticeps clupeoides, Green- wood, 1968) ancl is missing in Sierrathrissa leonensis (Whitehead and Teugels, 1985) ancl three species of lenkinsia (Cervig6n ancl Velazquez, 1978). The pattern of formation and ossification of the pectoral fin rays, from the uppermost proceeding ventrad, seems to be common within the Clupeiformes (Richards et a1., 1974; Sreekumari, 1976) and most teleost fishes. Sequentially, the pelvic fin is the latest to start formation in Clupeiformes. Completion of the number of fin rays occurs either before (Mansueti, 1962; Houde et aI., 1974; Richards et aI., 1974; Houde and Swanson, 1975; Fukuhara, 1983) or after (Takita, 1967; Norden, 1967; Sreekumari, 1976; Johnson and Loesch, 1983) pectoral fin ray completion. The pelvic scute, a peculiar c1upeoid structure, provides interesting problems. Its morphology, taxonomical importance, and distribution among Clupeiformes have been indicated by Whitehead (1962, ]963). Clupeidae, Engraulididae, and Chirocentridae have it while Denticipitidae have an articulated pelvic plate instead (Greenwood, 1968). Whitehead (1963) proposed that the pelvic scute and pelvic plate arise from modified splint bones while Greenwood (1968) suggests that the pelvic scute is derived from an abdominal scute, the pelvic scute representing an aborted first ray. In E. japonicus the pelvic scute arises not from a single but from three scale-like structures accounting for the lateral arms and the basal plate. Its composed nature may make derivations toward more specialized shapes easier. Among c1upeoids, vertebral ossification seems to follow a basic pattern starting at the caudal end, then on the abdominal centra proceeding anteriad and posteriad. The preural centra 2-4 are the last to ossify (Gwyn, 1940; Houde et aI., 1974; Richards et aI., 1974). E. japonicus, however, exhibits two minor departures: the first abdominal centra to be ossified are apparently located a little more anteriorly than in c1upeids and a new ossification center is added involving the two or three anteriormost centra. Centra ossification in the caudal complex also seems to be similar in this group, starting with ural centrum 2, then preuml centrum 1 followed by ural centrum 1,. and then the anterior preural centra. Chondrification of neural and haemal arches seems to be similar between c1u- peid and engraulid fishes. It starts from the caudal end proceeding anteriad. Short- ly after, it also begins at the first vertebrae proceeding posteriad. Abdominal arches are the last to fonn (Gwyn, 1940). Ossification of neural and haemal spines in Harengula jaguana (Houde et aI., 1974) is basically the same as for E. japonicus. Interestingly, in Opisthonema oglinum (Richards et aI., 1974), neural and haemal spines ossify from the caudal end proceeding only anteriad. Throughout development of E. japonicus, predorsal bones show no evidence of serial homologies, neither with the pterygiophores nor with the median neural spines, as had been suggested by Goodrich (1930) and later by Smith and Bailey (1961). However, Mabee's interpretation (1988) of teleost predorsal bones (a po- sitional name) as "supraneurals," while probably phylogenetically correct, is out- side the ontogenetical evidence to date. BALART: DEVELOPMENTAL OSTEOLOGY OF ENGRAUUS 519 ACKNOWLEDGMENTS I thank the following persons for reviewing the manuscript: T. Iwai, M. Matsuoka, P. J. P. Whitehead (now deceased), an anonymous reviewer, and especially T. Potthoff. O. Fukuhara supplied me with laboratory reared specimens and T. Minami collected the field-caught specimens. K. Hosoya, T. Nakabo and M. Matsuoka discussed with me aspects of osteology and development. Thanks also to E. Glazier for editorial advice on the manuscript. The author thanks the Japanese Government for financial support during his post-graduate studies at Kyoto University. LITERATURE CiTED Balart, E. E 1985a. Osteo]ogical development of the hyobranchia] apparatus in Engraulis japonicus. Bull. Japan. Soc. Sci. Fish. 51: 515-519. ---. 1985b. 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