BULLETIN OF MARINE SCIENCE. 29(3): 329-343. 1979

LEPTOCEPHALUS LARVAE OF THE FAMILY . I. OPHICHTHUS GOMESI CASTELNAU

Mark M. Leiby

ABSTRACT Two hundred fifty-five larvae of Ophichthus gomesi, comprising a developmental series from just hatched to metamorphic, are described. Osteological and morphological develop- ment is described and illustrated. A method of determining the number of adult precaudal vertebrae from the leptocephali is provided. This will allow more accuracy in - adult comparisons. Two morphologically distinct, premetamorphic stages of ophichthid lep- tocephali are named and described.

The ubiquitous eel family Ophichthidae, long a source of confusion for ichthy- ologists (Myers and Storey, 1939; Gosline, 1950), has recently received consid- erable attention. McCosker (1977) studied intergeneric relationships based on osteology. Bohlke (pers. comm.) is preparing a manuscript on ophichthids of the western North Atlantic. The leptocephalus larvae of the family are largely un- described, however. Castle (1965) tentatively assigned 18 forms of ophichthid leptocephali from Australasian waters to genus, but was unable to provide generic definitions that could be readily applied elsewhere. Blache (1977) identifies 25 species in 14 genera from the eastern Atlantic. In the western North Atlantic two such identifications, Myrophis punctatus by Eldred (1966) and Pisodonophis cruentlfer by Richardson (1974), have been made. Fahay and Obenchain (1978) offer names for 10 additional species in 6 genera. The collection of large numbers of ophichthid leptocephali by the Florida De- partment of Natural Resources, Marine Research Laboratory (MRL), and by the Marine Biomedical Institute, Galveston, Texas (MBI), make it possible to con- tinue the identification of leptocephali with their adult forms. This paper is in- tended to be the first in a series of descriptions of ophichthid leptocephali col- lected in the Gulf of Mexico.

MATERIALS Collections

The 255 specimens described in this study are mainly from the MRL Pelagic Fish Series (PF) collected between December 1967 and October 1969 and from MBI collected between February 1975 and August 1976. Figure 1 shows the geographic distribution of these specimens as well as 425 more which were identified, measured and examined for developmental stage. The PF collections were made with I-m plankton nets (605 JLm with 295 /.Lmcod end). The MBI specimens were mainly taken with 2-m plankton nets (526 /.Lmor 351 JLm mesh). One specimen was taken with a 3-m Isaacs-Kidd Midwater Trawl. Size range.-The larvae ranged from 5.9 to 102.7 mm total length; eight of these are metamorphosing larvae from 90.1 to 70.5 mm total length. Presen'ation and conditioll.-Most specimens were preserved in 5% buffered Formalin. A few were preserved in 70% ethanol which proved inferior to Formalin as it resulted in wrinkled specimens.

329 330 BULLETIN OF MARINE SCIENCE, VOL. 29, NO.3, 1979

* * **••

0: Engyodonllc Stage < 20.0mm TL .: Engyodontlc Siage ~ 20.omm TL *: Euryodontlc Stage .•• : Metamorphic Stage

Figure I. Distribution of larval Ophichthus gomesi.

METHODS Morphometries Measurements were taken to the nearest 0.1 mm using an optical micrometer in a binocular dissecting microscope, except where damage to the specimens precluded certain measurements. TOTALLENGTH(TL). Snout tip to caudal tip. This was used rather than stan- dard length because in late pre metamorphic and metamorphic specimens the cau- dais rays become embedded in the increasingly opaque tail tip and standard length becomes difficult to determine. PREANALLENGTH.Snout tip to anus. HEAD LENGTH(HL). Snout tip to pectoral base. PREDORSALLENGTH.Snout tip to first dorsal ray or pterygiophore in full-grown or metamorphic larvae; snout tip to anterior end of translucent dorsal thickening in which pterygiophores develop in early leptocephalus larvae. SNOUTLENGTH.Snout tip to anterior margin of clear membrane covering eye. EYE DIAMETER.Greatest horizontal distance between anterior and posterior edge of clear membrane covering eye. BODYDEPTH. Depth at deepest point; usually at anus in specimens 50 mm TL or longer; approximately midway between head and anus in specimens less than 50 mm TL. LEIBY: LEPTOCEPHALUS OPHICHTHUS GOMES! 331

\

lmm

--- lmm

c lmm-

Figure 2. Developmental stages of larval Ophichthus gomes;: (A) Engyodontic Stage; 20.7 mm TL, (B) Euryodontic Stage; 60.5 mm TL., and (C) Metamorphic Stage; 87.4 mm TL.

Meristics TOTAL MVOMERES.All myomeres including anterior ones not extending below midlateralline. PREANALMVOMERES.Myomeres back to and including one above anus. NEPHRIC MVOMERES.Myomeres back to and including one above posterior- most point of nephros. This count consistently reflects the number of precaudal vertebrae more ac- curately than do preanal myomere counts. Two closely related species of adult from the same geographical area may have similar total vertebral counts but may still be separated by a difference in number of precaudal or preanal vertebrae (Asano, ]962). Consequently, .it is desirable when examining leptocephali to ac-

Table I. Comparison of preanal and nephric myomeres (Leptocephali) with precaudal vertebrae (adults)

Preanal Nephric Precaudal Species Myomeres Source Myomeres Vertebrae Source

Ahlia egmolltis 68-75 Pers. obs. 68-71 69-71 Dean, 1972 Myruphis p/atyrhYllchus 53-56 Pers. obs. 51-54 52-55 Dean, ]972 Myrophis p/umbeus 57-61 Blache, 1968 55-58 56-59 Dean, 1972 Myrophis PllllctutUS 54-59 Eldred, 1966 55-57 54-59 Dean, 1972 Anguilla rostrata 68-71 Taning, 1938 44-47 43-45 Schmidt, 1909 AI/oeonger allagoides 127 Castle, ]964 68 69 Asano, 1962 Ar;osoma ba/earieum 118-123 Blache, 1977 63-71 65-67 Blache, 1977 COllger orbigllyallus 129-140 Blache, 1977 56-61 55-56 Blache, 1977 Ophiehthus games; 67-75 pers. obs. 55-61 56-63 pers. obs. Oph;chthus pari/us 57-60 pers. obs. 51-54 46-53 pers. obs. Pythoniehthys microptha/mus 90 Blache, 1977 47-55 49-51 Blache, 1977 332 BULLETIN OF MARINE SCIENCE, VOL. 29, NO.3, 1979 curately determine the number of precaudal or preanal vertebrae in adult speci- mens. In some leptocephalus larvae the nephros terminates almost at the anus. For these species either preanal or nephric myomere counts can be used to de- termine the number of precaudal vertebrae. In cases where preanal myomeres far exceed precaudal vertebrae, the number of nephric myomeres is still an accurate indicator (Table]; Blache, ]977). PREDORSALMYOMERES.Myomeres back to and including one below first dorsal ray or pterygiophore in full-grown or metamorphic larvae; to anterior end of dorsal thickening in which pterygiophores develop in early stages. POSITIONOF GUT Loops ANDSWELLINGS.Indicated by myomere numbers at anterior and posterior edges of gut loop or swelling, or chromatophore patch which lies dorsally of each gut loop.

Growth Stages Smith (1969: 385) states "there are only three stages in the pelagic life of a young eel which are qualitatively distinct": premetamorphic, metamorphosing, and glass eel. In ophichthid leptocephali I consider there to be four morphologically distinct posthatch stages:

Engyodontic (Figures 2A, 3A) Commences after hatching: characterized by a few needle-like teeth, each tooth shorter than the one anterior to it; lower jaw equal to or longer than upper; nasal capsule unformed; fin-fold not yet differentiating; hypurals not forming; ratio of head and preanal lengths to total length high as compared to other stages.

Euryodontic (Figures 2B, 3B, C) Engyodontic to : commences with shedding of needle-like teeth in anterior end of lower jaw, shedding proceeds posteriorly on lower jaw then anteriorly on upper jaw, engyodontic teeth replaced concurrently by three series of shorter, broad-based teeth in both upper and lower jaws; lower jaw becoming shorter than upper; head length as percent of total length decreasing; hypural formation and fin differentiation.

Metamorphic (Figures 2C, 3D, E) Anterior and posterior nostrils formed, becoming tubular; body becoming thicker, its length and depth decreasing; head to total length ratio increasing; axial skeleton forming.

Glass Eel Metamorphosis complete; adult pigmentation not yet acquired; specimens were unavailable.

Osteology Thirty engyodontic to metamorphic specimens were stained differentially for bone and cartilage using a modification of Wasserburg (1976). Specimens were LEIBY: LEPTOCEPHALUS OPHICHTHUS GOM£SI 333

Table 2. Comparison of larvae examined with characters of Ophichthlls (from McCosker, 1977) (+ = present, - = absent, r = reduced, v = vertical)

Character Larvae Examined Ophichthus

Basibranchial #2 + +, f, - Basibranchial #3 r, - Basibranchial #4 + +, f, - Ceratobranchial #5 + + Preoperculomandibular pore #3 +,- Preoperculomandibular pore #4 Temporal pore #2 All median fins + + Tubular anterior nostril + + Supracleithrum + + Nasals + + Interopercle + + Pectoral Fin + + Precaudal Vertebrae:;; Caudal Vertebrae + + Branchiostegal Rays Free From Epihyal Angle of Suspensorium v v

stained in alcian blue 2 to 4 h then rinsed and placed for 24 h in a solution of 1% KOH and aqueous alizarin red. The specimens were rinsed in distilled water, blotted and placed in consecutive solutions of four parts glycerol to six parts 1% KOH; seven parts glycerol to three parts 1% KOH; and 100% glycerol. Time in each solution was about 24 h but was largely subjective based on the appearance of a specimen. Two adult specimens were cleared and stained following Taylor (1967). Radio- graphs of 10 adults were made using a Torrex 120 X-ray machine and Kodak Industrial Type R film. Bone terminology follows McCosker (1977) except caudal fin terminology which follows Monod (1968). Drawings were made using a camera lucida on a Wild dissecting microscope.

LARVAL IDENTIFICATION The eel family Ophichthidae is unique in having numerous branchiostegal rays overlapping ventrally; supraorbital canals united by a transverse frontal commis- sure; the first epibranchial connected to the second infrapharyngobranchial by a cartilaginous strap. In the Ophichthinae caudal rays are usually embedded in a hard, pointed tail tip (McCosker, 1977). Castle (1965) considered multiple loops and swellings of the gut diagnostic for ophichthid leptocephali. Larvae in this study were readily identified as Ophichthines using these char- acters. Overlapping branchiostegal rays developed early in the euryodontic stage. The transverse frontal commissure of the cephalic lateralis system, the temporal canal, the cartilaginous interconnection between the first epibranchial and second infrapharyngobranchial bones of the gill arch, and the caudal rays embedded in a hardened tail tip became apparent in late euryodontic and early metamorphic specimens. Multiple loops and swellings of the gut were present but much reduced and not always apparent. Many ophichthid genera are circumglobal and others may prove to be as the family becomes better known. Consequently, I tried to find characters these leptocephali possessed by which I could place them in one of the currently ac- cepted Ophichthine genera known to occur in the eastern Pacific or eastern At- 334 BULLETIN OF MARINE SCIENCE, VOL. 29, NO.3. 1979

I i" 11 1 LEIBY: LEPTOCEPHALUS OPHICH1HUS GOMESI 335

Table 3. Meristics of larvae examined and adult Ophichrhus gomesi

Larvae Examined Adult

Character N Range N Range

Total vertebrae (Myomeres) 193 138-150 145.0 12 140-]47 143.5 Precaudal vertebrae (Nephric myomeres) 243 56-63 60.2 12 55-61 58.3 C

lantic as well as the western Atlantic. Echelus and Leptenchelys were not con- sidered because they possess a caudal fin confluent with the dorsal and anal fins. Based on characters in Table 2, it seems certain the specimens are Ophichthus. Bohlke (pers. comm.) currently recognizes nine species of Ophichthus from the western Atlantic. Of these only Ophichthus cruentifer leptocephali have been identified (Richardson, 1974 as Pisodonophis). Total and precaudal vertebral counts of O. gomesi, O. melanoporus, O. ace/- latus, O. aphis, O. parilus, O. spinicauda, and two undescribed Ophichthus spp. were obtained from X-rays of available specimens or from Bohlke. These were compared to total and nephric myomere counts of the leptocephali. Branchioste- gal rays and cephalic lateralis system were examined for all species except O. spinicauda and one O. sp. These were compared with the available metamorphic larvae. All but O. gomesi were eliminated from consideration. There are appar- ently more forms of ophichthid leptocephali in the Gulf of Mexico than described adults. Consequently it is remotely possible that these leptocephali are those of an unknown adult. However, identification of these specimens as O. gomesi is supported by comparison of adult and larval fin-ray, branchiostegal-ray and ver- tebral/myomere counts (Table 3), and by the absence of preoperculomandibular pore (pop) 3 in these larvae (Table 4). Except for O. gomesi, all known species of Ophichthus in the western North Atlantic have pop 3. Fahay and Obenchain (1978) describe a series of 150 specimens which they identify as O. gomesi. Their specimens were unavailable for study, so a direct comparison with my specimens was not possible. It is apparent from their de- scription, however, that we are describing different taxa. There are similarities between their specimens and mine: both series have 138-150 total, 60-70 pre- dorsal, and 65-75 preanal myomeres. (I am ignoring two of their specimens. One has 62 preanal myomeres; the other has 79. These are either aberrant forms or different species.) Both series have eight low loops, or swellings, of the gut. There are also critical differences: in my series the nephros terminates on gut loop seven under myomeres 56-63 (Table 3; Fig. 2); in their series the nephros terminates on loop eight, above the anus at about myomeres 65-75. As previously shown (Table 1; Blache, 1977), nephric myomeres are a valid indicator of adult precaudal vertebrae number. Ophichthus gomesi adults have 55-61 precaudal vertebrae (x = 58.3; N = 12). It seems apparent on this basis alone that their series cannot be O. gomesi. 336 BULLETIN OF MARINE SCIENCE, VOL. 29, NO.3, 1979

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LARVAL DESCRIPTION General Morphology Body relatively elongate, much compressed, clear. Total myomeres 138-150 (x = 145; N = 193); nephric myomeres 56-63 (x = 60.2; N = 246); preanal myo- meres 67-75 (x = 70.8; N = 248), except in metamorphic specimens; predorsal myomeres 60-70 (x = 65.1; N = 107). Branchiostegal rays 19-21 (x = 19.5; N = 6). Anal fin rays 159-199 (x = 183.5; N = 71). Dorsal fin rays 225-26] (x = 245.6; N = 15). Pectoral fin base at myomeres 3-5 (x = 4.]; N = 76). Generally eight much-reduced gut loops or swellings, often differentiable from preservation artifacts only by chromatophore patch beneath nephric duct at swelling; two usually distinct loops along esophagus, first at anterior end of liver under myo- meres 11-16 (most commonly 12-]4), second at posterior end of liver and gall bladder under myomeres 19-25 (most commonly 20-23); gut expands posterior to gall bladder; gut loops three to six, when present, under myomeres 27-33 (28- 3 I), 35-41 (36-40), 42-48 (44-47), 49-55 (51-54); loop seven at end of nephros under myomeres 56-63 (58-61); loop eight at terminus of gut under myomeres 67-75 (69-71). Pigmentation in Formalin: Preserved specimens inconspicuous, chromato- phores small and mostly amorphous. Location of chromatophore patches usually consistent among specimens; chromatophore number per location variable. A single, often stellate, chromatophore occasionally present on upper jaw below posterior end of nasal capsule. A variable number of sometimes stellate chro- matophores lie in body wall lateral to heart. One, often many, nondescript chro- matophores occur on each myoseptum below mid-lateral line starting above mid- point of esophagus. Eight irregular pigment patches lie along gut beneath nephric duct marking gut loops or swellings; occasionally nondescript or stellate chro- matophores occur ventrally on liver. Three to four, often faint, irregular chro- matophore patches on ventral surface of dorsal aorta near postanal myomeres 9, 25, 39, 52. One or two small chromatophore patches on ventral surface of anal fin pterygiophores. A pseudobranchial-like organ extending from anterior third of hyomandibular to posterior third of opercle lies in membrane lining inner surface of cheek.

Engyodontic (Figures 2A, 3A) Characters mentioned in the definition of the growth stages are not repeated here except where greater clarification is needed. Total length 5.9-35.4 mm. Greatest body depth 9.0-13.6% TL, midway be- tween head and anus. Preanal length 70-80% TL (x = 75.7%; N = 21). Predorsal length 61.0-65.7% TL (x = 63.4%; N = 5). Head length 6.8-14.0% TL (x = 9.6%; N = 20). Eye diameter ]6.2-24.0% HL (x = 20.6%; N = 20). Snout length 2.3- 5.2% TL (x = 3.4%; N = 21),34.6-48.3% HL (x = 37.9%; N = 21).

Euryodontic (Figures 2B, 3B, C) Characters mentioned in the definition of the growth stages are not repeated here except where greater clarification is required. Total length 22.7-102.7 mm. Greatest body depth shifts posteriorly to anus. Preanal length 50-60% TL (x = 57.8%; N = 30) midway through euryodontic 338 BULLETIN OF MARINE SCIENCE, VOL. 29, NO.3, 1979 stage; preanal myomere number remains stable. Predorsallength 47.7-56.9% TL (x = 51.6%; N = 25); predorsal myomere number remains stable. Head length 3.4-5.1% TL (x = 4.5%; N = 75) by end of euryodontic stage. Reduction in relative preanal, predorsal and head length due to differential growth in tail region. Eye diameter 16.8-21.8% HL (x = 19.2%; N = 75). Snout length 1.1-1.8% TL (x = 1.4%; N = 29), 29.2-36.5% HL (x = 32.1%; N = 30). Cephalic lateralis system starts developing.

Metamorphic (Figures 2C, 3D, E) Characters mentioned in the definition of the growth stages are not repeated here except where greater clarification is required. Total length 90.4-70.5 mm, TL decreasing during metamorphosis. Greatest body depth at anus (5.5-9.3% TL). Preanal length 48-55% TL (x = 50.8%; N = 6); reduction in relative preanal length due to progressively anterior location of anuS and anal fin; 70 preanal myomeres in earliest identifiable specimen, 62 in latest, 44-50 preanal vertebrae in adults. Predorsallength 42.7-50.9% TL (x = 45.4%; N = 5); anterior relocation does not begin until metamorphosis is well under way; 47 predorsal myomeres in most completely metamorphosed specimen available, 13-15 predorsal vertebrae in adults. Head length 5.3-6.9% TL (x = 6.1%; N = 6); increase in relative HL due to posterior relocation of pectoral fin (at myomere 3-5 for euryodontic larvae, at vertebrae 11-12 for adults), neurocranium length remaining constant or increasing, TL decreasing with onset of metamor- phosis; head length 11.6% TL for adults (N = 2). Eye diameter 14.6-16.8% HL (x = 15.3%; N = 6), relative eye diameter decreasing to 10.0-11.2% HL for adults (N = 2). Snout length 16.0-24.1% HL (x = 21.2%; N = 6); decrease in relative snout length due to slight anterior relocation of eye and posterior relo- cation of pectoral fin.

OSTEOLOGY Fins and Axial Skeleton (Figure 3) A median fin-fold persists until the euryodontic stage. Pterygiophore devel- opment first becomes apparent as increasingly opaque blocks at the base of the anal fin-fold. Development proceeds posterior to anterior. Dorsal fin pterygio- phore development, also starting at the posterior end, soon follows. The first noticeable fin rays occur simultaneously in posterior dorsal and anal fins and in the caudal fin. Anal fin rays develop quickly and the full complement is developed and countable in unstained specimens as small as 47.7 mm TL. Dorsal fin rays develop more slowly. With alcian blue stain, developing dorsal fin pterygiophores could be counted in specimens as small as 79.8 mm TL, but the fin rays were not all apparent until very near metamorphosis. The caudal fin of six (occasionally seven) rays, is continuous with the dorsal and anal fins until shortly before metamorphosis when the caudal fin fold is re- sorbed; rays start to ossify, shorten and become embedded in the hardening tail tip. The pectoral fin is a large, fleshy tab until late in the euryodontic stage when actinotrichia first appear. In early metamorphosis the full complement of pectoral lepidotrichia first becomes apparent stained lightly with alizarin. A cartilaginous pectoral fin support with two foramina and two posteriorly projecting spikes LEIBY: LEPTOCEPHALUS OPHlCH1HUS GOMESI 339

2mm

Figure 4. Lateral view of the cartilaginous pectoral fin support in the Euryodontic Stage.

develops early in the euryodontic stage (Fig. 4). It is best developed in mid- euryodontic specimens and apparently resorbed in late-euryodontic specimens. Early in metamorphosis the cleithrum and supracleithrum first appear in cartilage (alcian blue stain) and soon ossify. In no specimens were the scapula, coracoid, or actinosts yet visible. Development of the caudal skeleton starts early in the euryodontic stage (ap- prox. 35 mm TL). The first structures to appear are three hypurals which are fused at the base. Hypurals 1 and 2 are also fused posteriorly but are separated by a foramen which is reduced during growth. Shortly after hypural appearance, the parhypural and, almost simultaneously, the haemal arch of preural centrum 2 develop. In quick succession thereafter, the notochord constricts, marking the onset of centrum development, and neural arch formation begins. Preurals I and 2 are united from the beginning. The fused centra bear two neural arches and two haemal arches which unite early in development. There is only one apparent ural centrum but two distinct neural arches on the centrum indicate that two fused ural centra are ontogenetically present. Six caudal rays are weakly supported by the caudal complex. The fused neural arches of ural centra I and 2 support the two most dorsal rays. Two rays are more strongly supported by hypural 3, and two are weakly supported by fused hypurals I and 2. The first sign of vertebral development comes late in the euryodontic stage and may signal the onset of metamorphosis. Shallow constrictions of the notochord set off the reduced ural centrum and the first two preurals. Constriction into centra proceeds anteriorly, followed closely by neural arch formation, and more slowly by haemaI arch formation. Ossification of centra and median fin rays starts soon after the beginning of centrum formation and proceeds anteriorly. Pterygiophores do not ossify until late metamorphosis. Centrum formation was incomplete in the specimens examined; parapophyses and ribs were not devel- opmg. Head skeleton.-The sequence of development of the head skeleton is shown in Table 5. The only skeletal elements that appear to be present in the engyodontic larvae are the hyomandibular (possibly the quadrate) and Meckel's cartilage. During transformation to the euryodontic stage, the ceratohyal develops. There is a median cartilaginous block in the ethmoid region but it seems to be resorbed in late stages as the supraethmoid develops. In adult ophichthids, the preorbital block is considered to be a fusion of the premaxilla, vomer, and ethmoids (Asano, 1962; McCosker, 1977). Neither the vomer nor anything I could identify as its precursor was visible in any of the specimens. It apparently arises in a later metamorphic stage than any specimens available for study. There is no premaxilla evident in any of the specimens. The paired fangs terminal in the upper jaw (Figs. 2, 3) do not seem to be premaxilla precursors (Norman, 1926; Berry, 1964). They are embedded in the dorsomedial surface of the snout above the ethmoid block. They disappear as the supraethmoid 340 BULLETIN OF MARINE SCIENCE, VOL. 29, NO.3. 1919

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Figure 5. Hyoid and gill arches of an 80.3 mm euryodontic . Gill arches have been cut along the dorsal mid-line and spread laterally. Abbreviations: B" basibranchial I; C'_j' ceratobranchial 1-5; CH, ceratohyal; E" epibranchial I; GH, glossohyal; HH, hypohyal 1; 12, infrapharyngobranchial 2; IH, interhyal. develops rather than fusing to form the expanded portion of the rostrum, thought to be the premaxilla in the adult (Asano, 1962; McCosker, 1977). The supraeth- moid is clearly visible as an ossified structure in the more developed metamorphic specimens. There is no sign of ossification in the median ethmoid. The frontals appear prior to metamorphosis as two centers of ossification as predicted by McCosker (1977). The frontal suture is still clear in my most ad- vanced specimens. The expanded opercular base is preformed in cartilage (alcian blue stain), the remaining opercular apparatus appearing as weakly developed centers of ossification. The hyoid arch (Fig. 5) is cartilaginous until late metamorphosis. The urohyal and spike of the ceratohyal (McCosker, 1977) are ossifying. The rest of the hyoid arch is still cartilaginous. The basihyals, hypohyals, and epihyals are undifferen- tiated. An interhyal is present through metamorphosis. The branchial arch is cartilaginous in my specimens. Components of the first gill arch initially become distinguishable early in the euryodontic stage (35.8 mm TL). All elements except the upper and lower pharyngeal tooth plates are present in a specimen 48.6 mm TL (Fig. 5). Tooth plates are absent in my specimens and must develop late in metamorphosis or early in the juvenile stage. The lateralis system starts developing late in the eurydontic stage. The earliest specimen with the lateralis system forming is 79.8 mm TL. Table 4 shows the ossicles and pores present in eight leptocephali. More specimens are necessary before a detailed analysis of sequential development is possible. McCosker (1977) indicated that pop 3 was present in Ophichthus species he had examined. Examination of other species indicates that its presence is not a LEIBY: LEPTOCEPHALUS OPHICHTHUS GOMESI 343

generic character of Ophichthus (McCosker, pers. comm.), although it is present in all known western Atlantic Ophichthus except adult and larval O. gomesi. In two adults, the ossicle fused with the preopercle clearly has only one ventrolateral extension leading to a pore, unlike O. zophochir which has two. With this minor exception, the osteology of O. gomesi agrees with McCosker's (1977) description of the genus. ACKNOWLEDGMENTS

I am indebted to Dr. D. G. Smith (MBI) for making the large collection of ophichtid leptocephali obtained under the auspices of NSF Grant BMS 75-08675 available to me. I thank D. Hensley (MRL) for his encouragement, suggestions and helpful criticism. I thank Dr. J. E. Bohlke, Dr. J. E. Mc- Cosker. G. Smith (MRL) and L. Walker (MRL) for comments on this manuscript.

LITERATURE CITED

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DATE ACCEPTED: June 12, 1978.

ADDRESS: Florida Department of Natural Resources, Marine Research Laboratory, 100 Eighth Al'enue S.E., St. Petersburg, Florida 33701.