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Congrid Leptocephali in Australasian Waters with Descriptions of Conger wilsoni (Bl. and Schn.) and C. verreauxi Kaup.

Leptocephali of the Anagoinae

Leptocephali of the Anagoinae

Included in this group of larvae in the collection are five species, three of which are referred to Ariosoma Swainson, 1838, one provisionally to Alloconger Jordan and Hubbs, 1925, and the last which I cannot recognise as either Chiloconger or Anago (if indeed the latter is distinct from Ariosoma). There is therefore the possibility of a further genus in this subfamily, that this last species may belong to Anago, or that there is a further unknown species of Chiloconger. Leptocephali of the three genera are quite distinct in the distribution of chromatophores, but within Ariosoma with its three species described here only differences in numerical characters serve as specific characters. The same is true of other groups of leptocephali, not only of the Congridae. There are clear divisions in respect of pigment distribution enabling identification usually at the generic level and specific identification rests on numerical characters.

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Ariosoma Swainson, 1838
1838. Ariosoma Swainson, Nat. hist. class. fish. amphib. rept. 1: 220.
1839. Ophisoma Swainson, Nat. hist. class. fish. amphib. rept. 2: 334.
1856a. Congermuraena Kaup, Cat. apod. fish. p. 108.
1870. Congromuraena Günther, Cat. fish. Brit. Mus., 8: 40.
1898. Congrellus Ogilby (partim), Proc. Linn. Soc. N.S.W., 23: 2801.
1925. ?Anago Jordan and Hubbs, Mem. Carneg. Mus., 10 (2): 198.

Although there has been difficulty in establishing conclusively whether Muraena balearica De Laroche, 1809, or Muraena mystax De Laroche, 1809, was the basis for Swainson's Ariosoma, as I have already noted (1963, p. 18) the evidence is that it was A. balearica. Larvae of this species are well known from the central Atlantic and have been adequately described allowing me to recognise that closely similar larvae, differing only in the number of myomeres, occur in the present collection from the Australasian region. On the basis of the similarities, especially in the arrangement of pigment, these leptocephali are referred to Ariosoma.

The Ariosoma larvae fall readily into three clearly-defined groups with 110–119, 134–153, and 157–172 myomeres respectively. Ancona (1928, p. 17) and Gopinath (1949, p. 93), in their examinations of Red Sea and Ceylon leptocephali refer their Ariosoma larvae with about 115 myomeres to Temminck and Schlegel's Conger anago. Ancona confirmed this on the basis of a transitional specimen which had 119 myomeres. As Asano has shown (1962, p. 75) "Conger" anago has 149–159 vertebrae so that both Ancona and Gopinath were in error and their specimens clearly belong with the first group of larvae with 110–119 myomeres listed above from the present collection. Temminck and Schlegel's species, referred at present to Anago Jordan and Hubbs, 1925, is common in the waters of Japan and China, but due to its confusion with the other species discussed here, it has been assigned a much wider geographical range. Although Anago bears a striking resemblance to Ariosoma (Asano, 1962, p. 72) it possesses myorhabdoi or small bones above the epineurals and for this reason it is retained by Asano as distinct from Ariosoma. It is unknown at present whether Ariosoma possesses these structures. The single specimen referable to Ariosoma which I have in hand from Lord Howe Island is in such poor condition that I am unable to check for the presence of myorhabdoi.

Species of Ariosoma occur widely in the Atlantic from the Mediterranean to the Caribbean, in the Indian Ocean from the Red Sea to Natal and Malaya and in the Pacific from Lord Howe Island in the south to the west coast of Central America with the addition of China and Japan should Anago be proved a synonym of this genus. A number of species have been assigned, over the years, to Ariosoma but some of these will undoubtedly be placed finally in species of genera of the Congrinae, the adults of which bear at least a superficial resemblance to Ariosoma. A few of the known valid species have the following vertebral counts: A. balearica with 123–137, from the Central Atlantic and Mediterranean; A. gilberti (Ogilby, 1898) with ca. 116–121, from the Pacific coast of Central America; A. howensis (McCulloch and Waite, 1916) with ca. 153 from Lord Howe Island; A. (=?Anago) Anago with 149–159 from the coasts of Japan and China.

L. Ariosoma scheelei (Strömman, 1896), Text-fig. 1, A-I

1896. Leptocephalus scheelei Stromman (partim), Lept. Univ. Mus. Upsala, pp.21–24, p1. 1, figs. 6–7.
1913. (non) L. taenia Lesson. Weber, Siboga Exped., 57: 67.
1913. L. Indicus Weber, Siboga Exped., 57: 74.
1916. L. Indicus Weber. Weber and De Beaufort, Fish. indo-aust. archipel., 3:99, fig. 195.
1916. (non) L. taenia Lesson. Weber and De Beaufort, Fish. indo-aust. archipel., 3: 404–406, figs. 204–207.
1928. (non) Ophisoma anago (Temm. and Schleg.). Ancona, Mem. R. Com. talassogr. ital., 146: 13–14, p1. 1, fig. 1.
1928. (non) L. Ophisomatis anagoi (Temm. and Schleg.). A Ncona, Mem. R. Com. talassogr. ital., 146: 17–27, p1. 2, figs. 1–4a.
1934. ?Larva I. Deraniyagala, Ceylon J. Sci., B19 (1): 91–92, fig. 1.page 4
1936. L. Scheelei Strömman. Bertin, Bull. Inst. oceanogr. Monaco, 694: 3–5, fig. 4.
1939. ?Ariosoma nigrimanus Norman, Sci. Rep. John Murray Exped., 7 (1): 39–40, fig. 12.
1949. (non) Congrellus anago (Temm. and Schleg.). Gopinath, Rec. Ind. Mus., 47 (1): 93, p1. 10, fig. 4, tex-fig. 1c.
1956. (non) L. Ophisomatis anagoi (Temm. and Schleg.). Fowler, Fish. Red Sea Sth. Arabia. I, p. 114.
Text-fig. 1.—L. Ariosoma scheelei (strömman, 1986). Figs. A-D 105mm total length, IFO Station 7–2: Fig. A, lateral view; Fig. B, lateral view of head; Fig. C, tip of caudal region; Fig. d, distribution of pigment at level of gall bladder. Figs. E-F, 15.1mm total length, IFO Station 7–5: Fig. E, lateral view; Fig. F, teeth. Figs. G-I, 31.2mm total length, IFO Station S.3: Fig. G, lateral view; Fig. H, teeth; Fig. I, tip of caudal region.

Text-fig. 1.—L. Ariosoma scheelei (strömman, 1986). Figs. A-D 105mm total length, IFO Station 7–2: Fig. A, lateral view; Fig. B, lateral view of head; Fig. C, tip of caudal region; Fig. d, distribution of pigment at level of gall bladder. Figs. E-F, 15.1mm total length, IFO Station 7–5: Fig. E, lateral view; Fig. F, teeth. Figs. G-I, 31.2mm total length, IFO Station S.3: Fig. G, lateral view; Fig. H, teeth; Fig. I, tip of caudal region.

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Material Examined: Centre d'Océanographie de l'Institut Franç ais d'Océanie Collection (64 Specimens): 15.1mm total length, IFO Station 7–5, 22° 35′ S, 166° 16′ E, 26/7/62, MWT5 (5ft Isaacs-Kidd midwater trawl) horizontal tow, ca. 120 metres; 16.2, 123.5, St S.1, 21° 45′ S, 165° 10′ E, 6/6/62, MWT5, H, ca. 120m; 20.0, 27.2, 57.8, 71.2, 71.5, 71.8, 73.3, 77.2, 78.1, 79.8, 111.0, 115.3, 128.3, 128.4, St S.2, 20° 10′ S, 163° 27′ E, 7/6/62, MWT5, H, ca. 95m; 23.2, 25.3, 26.1, 30.0, 31.2, 71.1, 105.2, St S.3, 18° 10′ S, 162° 00′ E, 8/6/62, MWT5, H, ca. 95m; 25.6, 36.1, 37.8, 40.7, 73.7, St 7–4, 22° 35′ S, 166° 16′ E, 17/7/62, MWT5, H, ca. 35m; 30.5, MWT 3 I, 10 miles west of Bulari Pass, New Caledonia, 1/8/61, MWT3, H, ca. 40m, sample 6, 42.4, MWT3, H, ca. 17m, sample 1, 142.5, MWT3, H, ca. 83m, sample 3; 34.8, 61.5, St P57–5–1, 20° 06′ S, 168° 40′ E, 9/9/57 (0045hrs), S½mH (0.5m net, No. 2 mesh, horizontal tow), ca. 20m; 37.4, St 56–4–19, 14° 15′ S, 172° 14′ E, 21/10/56 (0001hrs), S½mH, ca. 50m; 37.6, St 56–5–3, 15° 45′ S, 166° 27′ E, 31/10/56 (2248hrs), S½mO, ca. 150m; 40.5, 51.2, 85.0, 99.0, St S.7, 10° 48′ S, 159° 00′ E, 12/6/62, MWT5, H, ca. 95m; 40.9, St MWT 2, 10 miles west of Bulari Pass, 30/11/61, MWT3, H, ca. 67m, sample 2; 41.9, St S.5, 13° 30′ S, 162° 05′ E, 10/6/62, MWT5, H, ca. 95m; 44.0, 45.8, St 7–1, 22° 35′ S, 166° 16′ E, 17/7/62, MWT5, H, ca. 70m; 45.2, St P58–3–3–6, 22° 41′ S, 166° 15′ E, 11/4/58 (0500hrs), S½mO, ca. 30m; 53.2, 62.3, St 56–3–4, 17° 52′ S, 168° 08′ E, 17/5/56 (0250hrs), S½mH, ca. 5m; 68.0, 77.5, St D10, 14° 50′ S, 157° 52.5′ E, 16/5/60 (2003hrs), S½mO, 0–300m; 75.9, St D10b, 14° 13′ S, 157° 55′ E, 17/5/60 (0214hrs), S½mO, 0–300m; 76.1, St D14, 10° 16′ S, 158° 37.5′ E, 18/5/60 (2012hrs), S½mO, 0–300m; 78.0, St D9b, 15° 21′ S, 157° 57′ E, 16/5/60 (1415hrs), S½mO, 0–300m; 91.8, St D12, 12° 39′ S, 157° 59′ E, 17/5/60 (2003hrs), S½mO, 0–300m; 96.5, 105.0, 131.2, St 7–6, 22° 35′ S, 166° 16′ E, 26/7/62, MWT5, H, ca. 50m; 105.0, St 7–2, 22° 35′ S, 166° 16′ E, 17/7/62, MWT5, H, ca. 70m; 106.9, St 7–8, 22° 35′ S, 166° 16′ E, 26/7/62, MWT5, H, ca. 20m; 112.9, ca. 120 (damaged), 121.1, St S.10, 17° 40′ S, 162° 25′ E, 22/6/62, MWT5, H, ca. 95m; 122.7, St 7–7, 22° 35′ S, 166° 16′ E, 26/7/62, MWT5, H, ca. 160m; 126.3, St LL57–5–4, 21° 33′ S, 166° 31′ E, 11/9/57, stomach of lancet fish, Alepisaurus ferox; 154.8, St S.11, 21° 31′ S, 164° 48′ E, 25/6/62, MWT5, H, ca. 95m.

Australian Museum Collection (2 Specimens): 119.2, Aust. Mus. regd. no. IB.3999, Collaroy, New South Wales, 17/9/58; 131.0, Aust. Mus. regd. no. IB.2954, Hawk's Nest Beach, New South Wales.

Western Australian Museum Collection (1 Specimen): 85.8, Accession No. P5172, 49 miles west of West End, Rottnest Island, Western Australia, 1/8/61 (0330–0430hrs), larval net, 110m.

Description: 67 specimens: total lengths 15.1mm-154.8mm, myomeres 110–119, dorsal and anal fin-rays greatest in number in the longest specimen, 102 and 106 respectively. Description made from a full-grown specimen, IFO St 7–2 (measurements in mm): total length 105.0, head 3.3, snout 1.2, eye 0.8, cleft of mouth 1.5, postorbital 1.5, pectoral 0.9, snout-vent 100.0, predorsal ca. 98.5, depth just before eye 1.7, at pectoral origin 2.7, at midpoint between pectoral and vent 12.3, at vent 4.3. Branchiostegal and pectoral rays not developed, dorsal rays 77, anal rays 67, caudal rays 3 + 3 + 1. Teeth 1 + 10 over 1 + 9 Myomeres 105 + 10 = 115. a–d = ca. 2. 1st vertical blood vessel at myomere 18, last at 58. Anterior margin of gall bladder at myomere 22.

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Body moderately elongate, much compressed except along head, its depth about eight times in total length, tapering equally in front of, and behind, the midpoint of the body. Head very short, about 30 in total length, with the throat indented so that the head is clearly differentiated from the trunk; snout conical, about 3.0 in head, its dorsal profile slightly convex; nasal organ large, close in front of eye, with the nostrils not yet developed; eye small, 4.2 in head, round; cleft of mouth oblique, extending to below middle of pupil: teeth in both jaws acute but rather broad-based; an anterior grasping tooth in each jaw followed by a single series of teeth which gradually diminish in size posteriorly. Pectoral fin short, about 2.0 in postorbital, delicate, rounded; dorsal and anal fins with poorly developed rays, dorsal originating only a little in advance of level of vent, caudal with well developed hypurals and fin-rays.

Pigmentation in preservative as follows:—below the midlateral level on each myoseptum from the third to the last an oblique line of minute, compact, oval somatic chromatophores few in number anteriorly but increasing to about 16–20 in the middle of the body, decreasing in number along the caudal region; from the fifth segment to the origin of the dorsal fin a series of relatively large somatic chromatophores, 1–2 on each segment, along the dorsal midline; from the pectoral region to the posterior margin of the gall bladder on the body wall of the ventral midline, a regular series of small, compact chromatophores, 6–8 to each segment; posterior to this series, continuing to the vent, a paired, regular row of very small, dense, splanchnic chromatophores on the dorsal aspect of the intestine, about 12–14 for each segment; scattered small spots on the basal portions of many of the dorsal and anal fin-rays; a few spots over the base of the caudal fin; chorioid pigment present.

Remarks: The group of specimens described above agrees well with Strömman's 140mm specimen of L. scheelei from the Timor Sea, redescribed by Bertin (1936, pp. 3–5, fig. 4). This specimen has 114 myomeres of which 103 are preanal, the vent is almost subterminal, the eye is small and round, the nostrils are set closely together in front of the eye, the pectoral is small, pigment is distributed in an oblique line of minute, compact spots below the midlateral line on each myoseptum, in a series along the dorsal midline and on the dorsal, anal and caudal bases, all exactly as in present specimens of comparable length. Strömman (1896, p. 22) describes the ventral pigment as follows: "On the lower side for about the first fifth of the body's length there extends a row of pigmentary spots very close together especially at the hinder end. A little beyond where this row ceases, two other rows of spots begin, one on each side of the body; they run just above the alimentary canal and reach as far as the vent. These spots are so close together that to the naked eye they appear to form two continuous dark lines." This is exactly as found in the present specimens although the two posterior rows on the dorsal aspect of the intestine (actually following the kidney ducts) are so close together that they appear as one in some specimens.

Weber's specimen of L. indicus (1913, p. 74) from the Sulu Sea, 115.0mm total length, has pigment spots on each myoseptum (as in L. Ariosoma scheelei), spots on the bases of the dorsal, anal and caudal rays and 115 segments of which 73 are preanal. There are no larval teeth but a few definitive teeth are present. These characters suggest that the specimen is a metamorphosing specimen of L. Ariosoma scheelei. The present collection contains three specimens which are at metamorphosis, 119.2mm, 126.3mm and 131.0mm total lengths, all of which have about 80 preanal myomeres and are probably at a slightly earlier stage than Weber's specimen.

The same author describes as L. taenia Lesson, 34 specimens of L. Ariosoma scheelei from the Banda Sea and neighbouring areas. These larvae, 56mm–124mm in length, have about 115 segments, the vent is essentially subterminal and the pigmentation is similar to that found in Strömman's L. scheelei although Weber makes no mention of pigment on the dorsal midline. I am satisfied, nevertheless that these leptocephali are L. Ariosoma scheelei. On the other hand, a small specimen, 19.5mm total length, which Weber also refers to L. taenia lacks the characters which are possessed by L. Ariosoma scheelei of equal size. There are 106 myomeres, there is no pigment except in the chorioid but the vent is very close to the end of the body. Although in such a small specimen errors may be made in counting the posterior segments, specimens of L. Ariosoma scheelei page 7of comparable length in the present collection show large, conspicuous pigment spots along the dorsal and ventral margins, a feature which could not easily be overlooked.

Gopinath (1949, p. 93, text-fig. 1c, p1. 10) describes and figures 216 leptocephali from the Trivandrum coast of southern India, all as Congrellus anago. These specimens were 110mm–158mm total lengths with about 115 myomeres and they have pigment as in L. Ariosoma scheelei. So far as I can determine from his account all of them have about 78 myomeres before the vent, and this seems to have been the only reason for Gopinath regarding them as distinct from L. scheelei. However, they are all relatively large leptocephali and in this respect agree with Weber's specimen. They are probably undergoing metamorphosis. The single specimen, 90mm in length, described and figured by Deraniyagala (1934, pp. 91–92, fig. 1) as Larva I from the Pearl Banks in the Gulf of Mannar, Ceylon, has 114 myomeres of which 103 are preanal. Pigmentation in this specimen is not described but in view of the posterior vent and strong general similarity to L. Ariosoma scheelei I regard Deraniyagala's larva as belonging to this species.

Ancona (1928, pp. 17–27, p1. 2, figs. 1–4a) has described 27 leptocephali, 15.5mm–139mm total lengths as L. Ariosoma anago, from the Red Sea, which I regard as L. Ariosoma scheelei. Ancona's specimens have 112–117 myomeres (compared with the 149–159 of A. anago), the pigmentation is typical of L. Ariosoma scheelei in all stages of development and the vent is essentiallv subterminal.

Ancona examined a small (195mm) juvenile of "A. anago", but the radiograph showed only 119 vertebrae. Norman (1939, p. 39, fig. 12) describes and figures Ariosoma nigrimanus as so far the only known species of the genus from the Gulf of Aden. Norman does not give a vertebral count but in view of its area of capture A. nigrimanus is a possible adult of Ancona's leptocephali and juvenile.

Leptocephalus dentatus (Garman, 1899) with myomeres 121 and L. obtusus (Garman, 1899) with myomeres 119, from the Pacific coast of central America are possibly larvae of Ariosoma gilberti (Ogilby, 1898) as I have already suggested (Castle, 1963, p. 31). The only vertebral count available for the aduit is ca. 116 from the type of Thyreoconger hemiaspidus Wade, 1946, also from Pacific central America, which Rosenblatt (1958, pp. 52–54) has shown to be a synonym of A. gilberti. This gives a range of vertebrae for the latter as ca. 116–121, close to the range shown above for L. Ariosoma scheelei. Comparison of Norman's description and figure for A. nigrimanus and Wade's for Thyreoconger hemiaspidus (1946, pp. 189–191, p1. 25, figs. 1–3) shows a remarkable similarity between the two. If A. nigrimanus is the adult of Ancona's leptocephali and juvenile, the latter provide a vertebral count which would suggest that A. gilberti may be a synonym of A. scheelei.

Growth and Metamorphosis: The 67 specimens of L. Ariosoma scheelei range in length from 15.1mm to 154.8mm of which the majority are larvae at various stages of growth short of metamorphosis but three (96.7mm, 106.0mm and 119.4mm) are undergoing metamorphosis.

Number of Preanal Myomeres.—During active growth from 15mm to about 40mm the vent moves from about myomere 60 to myomere 105 in the total of about 115. The position of the vent then remains constant during further increase in total length. At 120mm to 130mm metamorphosis begins.

Number of Dorsal and Anal Fin-rays.—These can first be counted when the larva is only 40mm in length at which time they number about 50 in the anal and 60 in the dorsal. The origin of the dorsal fin is never appreciably in advance of the level of the vent in larvae prior to metamorphosis (even in individuals of 130mm), usually only about two myomeres in front of it, so that extremely rapid movement of the dorsal origin to its final position over the pectoral, must occur during metamorphosis.

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Text-fig. 2.—Fig. A, distribution of 64 specimens of L. Ariosoma scheelei in the southwest Pacific. Fig. B, distribution of 32 specimens of L. Ariosoma anago in the southwest Pacific. IFO Station Nos. indicated.

Text-fig. 2.—Fig. A, distribution of 64 specimens of L. Ariosoma scheelei in the southwest Pacific. Fig. B, distribution of 32 specimens of L. Ariosoma anago in the southwest Pacific. IFO Station Nos. indicated.

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Teeth.—Although some specimens of L. Ariosoma scheelei (including the one described above) show little differentiation in size and grouping of teeth, most have teeth which are very similar to those of Gnathophis (see Castle, 1963, pp. 32–34). There is always an anterior grasping tooth in each jaw, which in the upper jaw is sometimes preceded by a small, needle-like tooth on the antero-dorsal surface of the snout; the grasping tooth is followed by a series of up to nine large teeth and then as many as 12 smaller teeth; there are always fewer posterior smaller teeth in the lower jaw. As in Gnathophis, as growth proceeds the bases of the larval teeth become overgrown by the fleshy snout and they appear to be relatively shorter in late leptocephali.

Pigmentation.—At 15mm the loptocephalus of Ariosoma scheelei has two minute, compact spots on each myoseptum below the midlateral line along the whole of the body except on the tip of the caudal region; dorsal pigment is restricted to about four large stellate spots along the dorsal midline; about four similar spots equally spaced along the midventral bodywall; a few compact spots on the dorsal aspect of the tip of the spinal cord. At about 30mm total length there are about 4–5 spots on. each myoseptum, about 18–20 dorsal spots, about 12 ventral spots and pigment on the tip of the caudal region. At the time when the posterior movement of the vent ceases (40mm) the dorsal spots become more compact, the caudal pigment is lost and the ventral stellate chromatophores are replaced by the small, somatic spots in a row on the ventral midline before the gall bladder and the two rows of minute, compact spots on the dorsal aspect of the intestine. Spots on the bases of the dorsal and anal rays begin to form at about 50mm total length.

Geographical Range and Location of Spawning Areas (Text-fig. 2, A)

Except for the two metamorphosing specimens of L. Ariosoma scheelei beachcast at Sydney and a single, nearly full-grown larva collected off Rottnest Island, Western Australia, all of the present material, that is, 64 specimens, came from the area included by the Solomons, New Hebrides and New Caledonia. The leptocephali are rare and the adult, if present, may be very rare in the Australian region. Small specimens of from 15mm to 35mm were collected in the area immediately surrounding New Caledonia and New Hebrides in 20–120 metres. Larger specimens are more widely distributed. It is therefore probable that spawning of Ariosoma scheelei in the southwest Pacific occurs in the waters around New Caledonia. In consideration of the size of specimens previously recorded from the Banda and Sulu Seas and neighbouring areas by previous authors it is likely that larvae move from the New Caledonia region westwards through the Malayan Archipelago as well as occasionally to Western and Eastern Australia. Ancona's studies of this species shows that it must also spawn in the Red Sea since his smallest specimen was 15.5mm total length; Gopinath's 216 larvae from southern India are all very large and it is unlikely that the species spawns in this area; these larvae are probably derived from the Red Sea.

Should A. gilberti from the Pacific central America finally prove to be a synonym of A. scheelei, the geographical range of the latter will extend across the whole of the Indo-Pacific. Briggs (1961, p. 552) lists seven species of shallow-water tropical eels which have a similar distribution, a relatively high number of trans-Pacific species for any one group of shore fishes. Generally the trans-Pacific species which Briggs lists are active pelagic fishes in which such a distribution can be explained in part by their ability to move about for some distances independent of the bottom. Others, like the eels and including Albula vulpes and Chanos chanos, have an extended pelagic larval life.

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L. Ariosoma mauritianum (Pappenheim, 1914)

1914. L. mauritianus Pappenheim, Dtsch. Südpol Exped., 7 (2): 189, p1. 10, fig. 8.
1916. ?Congermuraena howensis McCulloch and Waite, Trans. Proc. roy. Soc. S. Aust., 40: 438, p1. 40, fig. 2.
1928. L. mauritianus Pappenheim. Ancona, Mem. R. Com. talassogr. ital., 146: 36–37, p1. 2, figs. 12–12a.
1930. L. Mauritianus Pappenheim. Ancona, Ann. idrogr., 11: 270, fig. 4.

Material Examined: Centre d'Océanographie de l'Institut Français d'Océanie Collection (19 specimens): 43.7mm total length, IFO Station D15b, 9° 50′ S, 159° 20′ E, 22/5/60 (0219hrs), S½mO (0.5 metre net, No. 2 mesh, oblique tow), 0–300m; 53.6, 163.7, St S.6, 11° 51′ S, 159° 13′ E, 10/6/62, MWT5, H, ca. 95m; 56.0, St S.5, 13° 30′ S, 162° 05′ E, 10/6/62, MWT5, H, ca. 95m; 57.5, 89.8, 110.0, St P As 7 Hel 2, 23° 28′ S, 159° 23′ E, 8/5/58 (2015hrs), HeO (Heligoland larval fish net, oblique), ca. 100m; 81.2, St 7–3, 22° 35′ S, 166° 16′ E, 17/7/62, MWT5, H, ca. 35m; 93.9, St D19, 11° 19′ S, 162° 43′ E, 23/5/60 (2027hrs), S½mO, 0–300m; 98.6, St Foa 1m, 21° 21′ S, 164° 15′ E, 11/1/62, S1mO (1.0m net, No. 2 mesh, oblique), ca. 167m, sample 4; 126.6, 210.0, 269.0, 278.0, St LL 57–3–8, 22° 35′ S, 166° 08′ E, 9/7/57, stomach of lancet fish, Alepisaurus ferox; 145.1, St LL 57–6–3, 22° 50′ S, 165° 36′ E, 7/12/57, stomach of lancet fish, Alepisaurus ferox; 151.2, St Ep7b, 18° 23′ S, 159° 47′ E, 16/9/60 (0209hrs), S½mO, 0–300m; 173.0, St Foa MWT, 18° 35′ S, 159° 47′ E, 13/1/62, MWT3, H, ca. 100m, sample 4; ca. 181, St Foa MWT, 22° 20′ S, 165° 42′ E, 10/1/62, MWT3, H, ca. 100m, sample 1; 198.0, St LL 59–1–3, 22° 45′ S, 162° 44′ E, 30/1/59, stomach of lancet fish, Alepisaurus ferox.

C.S.I.R.O. Division of Fisheries and Oceanography (Cronulla) Collection (14 specimens): 11.8, 16.0, 16.8, Warreen Station 32/38, 24° 29.5′ S, 153° 26.5′ E, 20/9/38, N100, H, surface, 30 mins; 12.7, 19.4, 26.1, St 32/38, 24° 29.5′ S, 153° 26.5′ E, 20/9/38, N70, H, 25m, 30mins; 35.0, Tasman Sea, 3/4/49, N70, surface; 49.0, Warreen St 30/48, 32° 03′ S, 113° 30′ E, 24/8/48, N70, H, surface, 15mins; 60.8, St 205/39, 34° 03′ S, 151° 11.5′ E, 4/8/39, N70, O, 0–25m; 76.2, St 26/40, 32° 34′ S, 152° 55′ E, 20/4/40, N100, O, 0–200m; 86.4, St 129/39, 32° 34′ S, 152° 55′ E, 3/5/39, N100, H, 100m, 60mins; 100.6, St 206/39, 33° 56′ S, 151° 19′ E, 4/8/39, N200, H, surface; 117.4, St 37/38, 28° 37′ S, 153° 54′ E, 22/9/38, N70, H, 100m, 30mins; 230.3, St 3/49, 32° 03′ S, 114° 53.5′ E, 7/4/49, N70, H, surface, 10mins.

Australian Museum Collection (1 specimen): 102.1, Aust. Mus. regd. No. IA.3815, Dana Station 3663, haul 9, Tasman Sea, 33° 33′ S, 154° 04′ E, 23/2/29, ca. 50m.

Western Australian Museum Collection (47 specimens): 11.1, Accession No. P5229, Lancelin, 16 miles west of West End, Rottnest Island, Western Australia, 4/4/62 (0030hrs), larval net, 37 metres; 14.4, P5287, 34mls, 3/7/62 (0300– 0100hrs), In, 37m; 17.4, P5291, 44mls, 3/7/62 (0300–0330hrs), N70, surface; 19.1, P5308, 44mls, 3/7/62 (0300–0330hrs), N70, surface; 59.4, P5169, 50mls, 11/9/61 (2345–0015hrs), In, 110m; 70.5, P5537, 45mls, 10/10/62 (0150hrs), In, 37m; 87.3, P5553, 44mls, 7/11/62 (0230hrs), N70, surface; 88.5, P5554, 43mls, 7/11/62, In, 110m; 91.4, 137.3, P5556, 25mls, 13/11/62 (0100hrs), In, 37m; 92.2, P5541, 43mls, 10/10/62 (0330hrs), In, 110m; 96.3, 100.9, P5552, 45mls, 7/11/62 (0140hrs), In, 37m; 99.6, P5539, 44mls, 10/10/62 (0239hrs), In, 37m; 104.4, P5559, 40mls, 15/11/62 (0320hrs), In, 110m; 113.6, 133.5, P5555, 42mls, 7/11/62 (0440hrs), In, 37m; 118.0, P5550, 43mls, 7/11/62 (0010hrs), In, 37m; 121.2, P5551, 44mls, 7/11/62 (0100hrs), In, 37m; 121.3, P5244, 20mls, 4/4/62 (0430hrs), N70, surface; 137.1, 184.0, P5150, 43mls, 7/3/62 (0115–0145hrs), In, 37m; 138.7, P5154, 40mls, 7/3/62 (0330–0400hrs), In, 37m; 139.5, 165.6, 168.8, 176.9, 177.5, P5156, 43mls, 12/2/62 (0000–0030hrs), In, 37m; 139.8, P5178, 40mls, Feb./Mar., 1962, In, 37m; 145.0, 182.5, P5177, 42mls, 12/2/62 page 11
Text-fig. 3.—Fig. A, distribution of 34 specimens of L. Ariosoma mauritianum in the southwest Pacific. fig. B, number of myomeres in (a) L. Ariosoma anago (32 specimens), (b) L. Ariosoma (80 specimens), (C) L. Ariosoma scheelei (66 specimens).

Text-fig. 3.—Fig. A, distribution of 34 specimens of L. Ariosoma mauritianum in the southwest Pacific. fig. B, number of myomeres in (a) L. Ariosoma anago (32 specimens), (b) L. Ariosoma (80 specimens), (C) L. Ariosoma scheelei (66 specimens).

(0100–0130hrs), In, 37m; 146.9, P5176, 39mls, 12/2/62 (0315–0345hrs), In, 110m; 150.1, 163.0, 167.3, 168.6, P5155, 40mls, 13/2/62 (0230–0300hrs), In, 37m; 171.2, 178.5, 190.5, P5151, 41mls, 12/2/62 (0145–0215hrs), In, 37m; 178.3, P5296, 38mls, 7/3/62, In, 37m; 190.1, P5226, 40mls, 30/3/62 (0230hrs), In, 37m; 193.1, 204.3, P5166, 38mls, 12/2/62 (0415–0445hrs), In, 37m; 194.5, P5183, Umitaka Maru, 13° 45′ N, 115° 12′ E, 8/11/62, In; 198.0, P5247, Lancelin, 43mls, 30/3/62, In, 37m.

Description: 81 specimens: total lengths 11.1mm–278.0mm, myomeres 134–153, maximum number of dorsal fin-rays observed 120, anal 111. Description made from a half-grown specimen, Western Australian Museum Ace. No. P5553 (measurements in mm): total length 87.3, head 3.6, snout 1.5, eye 0.8, cleft of mouth 1.9, postorbital 1.5, pectoral 0.8, page 12snout-vent 82.1, predorsal 82.9, depth just before eye 1.8, at pectoral origin 2.5, at midpoint between pectoral and vent 8.4, at vent 2.0. Dorsal rays ca. 45, anal rays 40, caudal rays 5 + 4. Teeth 1 + IV + 7 over 1 + IV + 5 Myomeres 128 + 11 = 139. 1st vertical blood vessel at myomere 17, last at 75. Anterior margin of gall bladder at myomere 27.

Body conspicuously elongate, much compressed except along head, maximum depth contained about 10 times in total length, tapering equally in front of, and behind, the midpoint of body. Head very short, about 24 in total, with the throat indented; snout conical, about 2.5 in head, its dorsal profile slightly concave; nasal organ large, close in front of eye, its dorsal margin with a ventral extension midway along its length indicating approaching separation of the nares; eye small, 4.5 in head, round; cleft of mouth oblique, reaching to below middle of pupil; teeth rather broad-based, acute; anterior grasping tooth on the extreme tip of snout followed by a series of four large teeth and then by another series of seven smaller teeth; those on lower jaw similar. Pectoral fin short, about 2.0 in postorbital, delicate, rounded; dorsal and anal fin very short, restricted to posterior tip of body, dorsal origin close to level of vent, caudal with well-developed hypurals and fin-rays.

Pigmentation in preservative as follows:—below the midlateral level on each myoseptum from the seventh to the last an oblique line of minute, compact, elongate, somatic chromatophores, each arranged anteroposteriorly; these pigment spots are few in number anteriorly and are more numerous (usually about 12 in specimens of about 100mm total length but up to 20 in larvae of about 180mm) in the middle of the body length but decrease again in number until posterior to the level of the vent they number about four on each myoseptum; from about segment 20 to level of vent an unpaired series of small, diffuse, somatic chromatophores, 1–2 to each segment, on the dorsal midline; from the pectoral region to about halfway along the body length an unpaired series of small, diffuse, somatic chromatophores, about 5–6 to each segment, on the ventral midline, this series becoming less regular and fading out beyond the midpoint; posterior to the gall bladder a paired series of small, compact, splanchnic chromatophores above the intestine, about 6–9 per segment, through to the vent, although these are much less regular along the posterior part of the intestine; a few scattered chromatophores on the dorsal and anal bases; chorioid pigment present.

Remarks: The specimens described above have the larval pigmentation, round eye, short dorsal and anal fins and subterminal vent established for leptocephali of the genus Ariosoma. They agree well with Leptocephalus mauritianus Pappenheim, 1914, from Mauritius which has 140–145 myomeres (that is, in the middle of the range of 134–153 for the present material). Ariosoma howensis (McCulloch and Waite, 1916) from Lord Howe Island, of which the present author has examined one specimen, has about 154 vertebrae and is included here as a provisional synonym of L. Ariosoma Mauritianum.

Geographical Range and Location of the Spawning Areas (Text-fig. 3, A).

The present leptocephalus is now known from the Solomons, through New Caledonia and as far south as Sydney, but also occurs abundantly on the west Australian coast; a few specimens have been recorded from Mauritius and the Red Sea. Smallest specimens were taken off Sydney and Rottnest Island, Western Australia and suggest that spawning takes place in these areas. The leptocephali of this species collected in the neighbourhood of the western spawning area during 1962 fall into three well-defined groups, as indicated in text-fig. 4. The smallest larvae, below 20mm (a), were trawled in May-June and indicate a spawning in March-April; half-grown larvae, averaging 100mm (b), appeared in trawls made during October-November. Early in the year, in February-March, 1962, only large, full-grown larvae of about 150mm–200mm were collected and these are clearly larvae from the March-April spawning of the previous year, 1961. The larval life of Ariosoma mauritianum is therefore at least one year but is probably not much more than this, especially since most of the larger larvae appear to be close to metamorphosis.

The species is not so abundant as L. Ariosoma scheelei in the New Caledonia area and the smallest specimen from this region is 43.7mm in total length suggesting that spawning probably does not occur here. Ancona (1928, p. 37) records a 117mm specimen of L. Ariosoma mauritianum from the Red Sea, and together with the Mauritius examples, a third spawning area, off east Africa, is suggested.

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Text-fig. 4.—Lengths of 46 leptocephali of Ariosoma mauritianum collected off Western Australia during 1962; (a) very young larvae from the March-April spawning, (b) half-grown larvae, (c) full-grown larvae from the March-April spawning of 1961.

Text-fig. 4.—Lengths of 46 leptocephali of Ariosoma mauritianum collected off Western Australia during 1962; (a) very young larvae from the March-April spawning, (b) half-grown larvae, (c) full-grown larvae from the March-April spawning of 1961.

L. Ariosoma anago (Temminck and Schlegel, 1842)

1842. Conger anago Temminck and Schlegel, Fauna Japonica, p. 259, p1. 113, fig. 1.
For detailed synonymy see Asano, 1962, pp. 72–73.

Material Examined: Centre d'Océanographie de l'Institut Français d'Océanie Collection (32 specimens): 60.7mm total length, IFO Station D5, 18° 32′ S, 159° 50′ E, 14/5/60 (0820hrs), S½mO (0.5 metre net, No. 2 mesh, oblique tow), 0–300m; 90.5, St A 57–3–3 (8), 22° 37′ S, 166° 20′ E, 6/3/57 (1930 hrs), S½mH, ca. 10m; 117.9, St P58–3–3–4, 21° 41′ S, 166° 15′ E, 31/3/58 (2200hrs), S½mH, ca. 15m; 119.1, St D24, 16° 13.5′ S, 162° 47′ E, 25/5/60 (2329hrs), S½mO, 0–300m; 119.5, 124.3, 135.2, 140.5, 168.8, 179.2, 181.6, St S.2, 20° 10′ S, 163° 27′ E, 7/6/62, MWT5, H, ca. 95m; 129.5, 169.5, St S.l, 21° 45′ S, 165° 10′ E, 6/6/62, MWT5, H, ca. 120m; 142.2, 188.5, St S.11, 21° 31′ S, 164° 48′ E, 25/6/62, MWT5, H, ca. 95m; 145.1, 159.0, St S.3, 18° 10′ S, 162° 00′ E, 8/6/62, MWT5, H, ca. 95m; 151.0, St A57–7–2, 23° 27′ S, 162° 40′ E, 6/7/57 (1800hrs), S½mH, ca. 20m; 160.4, St D8, 17° 07′ S, 157° 47′ E, 15/5/60 (2003hrs), S½mO, 0–300m; 162.0, 190.7, 236.3, St S.10, 17° 40′ S, 162° 25′ E, 22/6/62, MWT5, H, ca. 95m; 248.1, 296.0, and two specimens in poor condition, St 57–4, south coast of Lifu (Loyalty Islands), 22/7/57, stomach of skipjack, Katswonus pelamis; 279.1, 289.5, St LL 57–3–8, 22° 35′ S, 166° 08′ E, 9/7/57 stomach of lancet fish, Alepisaurus ferox; 314.0, St G 23, 22° 07′ S, 165° 04′ E, 22/3/62, S½mO (1.0m net, No. 2 mesh, oblique tow), ca. 167m, sample 23; one specimen in poor condition St LL 61–5, 22° 54′ S, 164° 38′ E, 5/7/61, stomach of striped marlin, Makaira audax; two specimens in poor condition, St G LL 10, 20° 55′ S, 163° 18′ E, 21/3/62, stomach of lancet fish, Alepisaurus ferox.

Western Australian Museum Collection (1 specimen): 167.9, Accession No. P5241, Lancelin, 45 miles west of West End, Rottnest Island, Western Australia, 11/4/62 (0230hrs), larval net, 37m.

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Description: 33 specimens, total lengths 60.7mm–314rnm, myomeres 157–172, maximum dorsal rays 108, anal rays 91. Description made from an almost full-grown specimen, IFO Station S.11 (measurements in mm): total length 188.5, head 5.0, snout 1.8, eye 1.2, cleft of mouth 2.3, postorbital 2.3, pectoral 0.8, snout-vent 184.3, predorsal 185.0, depth just before eye 2.3, at pectoral origin 4.3, at midpoint between pectoral and vent 12.4, at vent 2.9. Dorsal rays 64, anal rays 53, caudal rays 3 + 3. Teeth 1 + IV + 6 over 1 + IV + 6 Myomeres 150 + 10 = 160. 1st vertical blood vessel at myomere 11, last at 81. Anterior margin of gall bladder at myomere 27.

Body extremely elongate but not filamentous, much compressed, except along head, maximum depth about 16 times in total, tapering equally in front of, and behind midpoint of body. Head extremely short, about 38 in total length, indented at the throat; snout conical, 2.8 in head, its dorsal profile straight; nasal organ large, close in front of eye, nares distinct; eye small, about four times in head, round; cleft of mouth oblique, extending to below middle of pupil; teeth broad-based, relatively powerful; an anterior grasping tooth on the anterior tip of snout followed by four large teeth and six much smaller teeth; those on lower jaw similar in size and distribution. Pectoral fin short, about 2.5 in postorbital or equal to horizontal diameter of eye; dorsal and anal fins very short, restricted to posterior tip of body, dorsal origin very close to level of vent, caudal with well-developed hypurals and fin-rays.

Pigmentation in preservative as follows:—below midlateral line on each myoseptum from about the tenth segment to the tail tip an oblique line of minute, compact, elongate, somatic chromatophores, each arranged anteroposteriorly; these pigment spots are few in number anteriorly but increase to about 15–20 (in full-grown specimens of 250mm) in the middle of the body length and finally decrease to about four or five on each myoseptum posterior to the level of the vent; a series of small, diffuse, somatic chromatophores on the dorsal midline from the 15th segment to the level of the vent, 1–2 per segment but more widely spaced posteriorly; a series of small, diffuse, somatic chromatophores along the ventral midline from the pectoral region to about the midpoint of the body length, about six per segment, the series fading out gradually towards the midpoint; posterior to the gall bladder a paired series of small, compact, splanchnic chromatophores along the dorsal aspect of the intestine to the vent, about 9–10 per segment but much less frequent posteriorly; a spot on the bases of most dorsal and anal rays; chorioid pigment present.

Remarks: In the 45 specimens of Ariosoma anago examined by Asano (1962, p. 73) vertebrae numbered 149–159, a range which is appreciably lower than that of the leptocephali here referred to this species (157–172). However, at the present state of knowledge of the adult species of Ariosoma in the Indo-Pacific I hesitate to separate these leptocephali from A. anago on the basis of this difference.

Only one relatively small specimen, measuring 60.7mm total length, is present in the above collection while the others are all over 90mm and reach 300mm, a very large size for congrid leptocephali. In all specimens the vent is very close to the tip of the caudal region indicating that there are no metamorphosing larvae in the collection. However, some show well-developed fin-rays and ossification of the skull, etc., indicating that they are probably full-grown.

L. ?Alloconger anagoides (Bleeker, 1864), Text-fig. 5, A-D

1864. Ophisoma anagoides Bleeker, Atlas ich. Indes. Orient. Neerl., 4: 27, p1. 149, fig. 3.
For further synonymy see Asano, 1962, p. 76.

Material Examined: Centre d'Océanographie de l'Institut Français d'Océanie Collection (2 specimens): ca. 58mm total length (damaged), IFO Station G LL 13, 23° 31′ S, 165° 53′ E, 4/4/62, stomach of lancet fish, Alepisaurus ferox; 76.3, St S.7, 10° 48′ S, 159° 00′ E, 12/6/62, MWT5, H, ca. 95m.

Description: Made from the undamaged specimen (measurements in mm): standard length 75.3, head 4.1, snout 1.6, eye 1.1, cleft of mouth 2.4, postorbital 1.8, pectoral 1.2, snout-vent 73.0, predorsal 74.9, depth just before eye 1.8, at pectoral origin 3.1, at midpoint between pectoral and vent 8.6, at vent 2.5. Pectoral rays undeveloped, only a few dorsal and anal rays present at tip of caudal region, caudal rays 5 + 3. Teeth 1 + 1 + IV + 8 over 1 + IV + 7 Myomeres 127 + 11 = 138. Last vertical blood vessel at myomere 68. Anterior margin of gall bladder at myomere 21.

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Text-fig. 5.—Figs. A-D, L. ?Alloconger anagoides bleeker, 1864), 76.3mm total length, IFO Station S.7: Fig. A, lateral view; Fig. B, lateral view of head; Fig. C, lateral view at about myomere 50 to show lateral pigment and splanchnic chromatophores on the kidney ducts; Fig. D, tip of caudal region. Figs. E-I, Leptocephalus scalaris n. sp., type, 108.8mm total length, IFO Station S.6: Fig. E, laterial view; Fig. F, lateral view of head; Fig. G, lateral View at about myomere 53 to show pigment below lateral line, and Fig. H, above lateral line; Fig. I, tip of caudal region.

Text-fig. 5.—Figs. A-D, L. ?Alloconger anagoides bleeker, 1864), 76.3mm total length, IFO Station S.7: Fig. A, lateral view; Fig. B, lateral view of head; Fig. C, lateral view at about myomere 50 to show lateral pigment and splanchnic chromatophores on the kidney ducts; Fig. D, tip of caudal region. Figs. E-I, Leptocephalus scalaris n. sp., type, 108.8mm total length, IFO Station S.6: Fig. E, laterial view; Fig. F, lateral view of head; Fig. G, lateral View at about myomere 53 to show pigment below lateral line, and Fig. H, above lateral line; Fig. I, tip of caudal region.

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Body moderately elongate, much compressed except along head, deep, the maximum depth about 8.0 in total, reducing very rapidly at the head but more gradually along the posterior third of the body. Head short, about 18 in total, distinct from trunk; snout acute, about 2.5 in head, its dorsal profile concave; nasal organ poorly developed, placed close in front of eye; eye circular, 2.0 in snout or 5.5 in head; cleft of mouth slightly oblique, extending to below middle of pupil; teeth relatively acute and distributed as follows: a minute tooth on the anterodorsal tip of snout followed by a large grasping tooth, a series of four large teeth and eight much smaller teeth, those of lower jaw similar. Pectoral fin short, less than length of snout, delicate, subcircular in shape; dorsal and anal fins very short with only their basal structures developed, the dorsal origin slightly behind level of vent.

Pigmentation in formalin as follows:—a short, oblique line of minute, compact, somatic chromatophores on each myoseptum below the lateral line, the maximum number of spots in these lines being about six in the middle of the body; a paired row of regular, essentially segmental, somatic chromatophores on the ventral surface from the level of the pectoral to the gall bladder; a paired row of compact, splanchnic chromatophores in the order of eight per segment arranged along the kidney ducts above the intestine to the vent; numerous small, somatic spots scattered over the whole of the lateral surface, more numerous below the lateral line; scattered spots on the dorsal and anal bases and over the base of the caudal fin; pigment in the chorioid.

Vertical blood vessels to the viscera numerous, beginning at the tenth myomere and occurring every three or four segments to the 68th.

Remarks: The leptocephali described here show similarities to Ariosoma leptocephali in the round eye, the posterior position of the vent, the short dorsal and anal fins and the presence of the rows of small chromatophores on the myosepta below the lateral line. The scattered lateral chromatophores, however, suggest that this leptocephalus does not belong in Ariosoma, but nevertheless, it clearly belongs in the Anagoinae-group of congrid leptocephali. Only one other genus. of this group is present in the Indo-West-Pacific and this is Alloconger Jordan and Hubbs, with its two species Alloconger anagoides (Bleeker, 1864) and A. shiranago Asano, 1958. The two subspecies of A. shiranago, A. s. shiranago Asano, 1958, and A. s. major Asano, 1958, both of which are known only from Japan, have 144–147 and 156–161 vertebrae respectively while A. anagoides, known from Indo-Malaya to Japan, has about 143. In view of the geographical distribution of the latter species I am satisfied that if the leptocephalus described-above is an Alloconger then it is probably referable to A. anagoides. The relatively large size of the two larvae (ca. 58mm and 76.3mm) suggest that the spawning area for the species may be distant from the area of capture.

Leptocephalus scalaris n.sp. (Text-fig. 5, E-I)

Material Examined: Centre d'Océanographie de l'Institut Français d'Océanie Collection (2 specimens): type, 108.8mm total length, IFO Station S.6, 1.1° 51′ S, 159° 13′ E, 11/6/62, MWT5, H, ca. 95m; paratype, 51.1, St S.5, 13° 30′ S, 162° 05′ E, 10/6/62, MWT5, H, ca. 95m.

Description: Made from the type specimen, IFO St S.6 (measurements in mm): standard length 107.7, head 5.0, snout 2.2, eye 1.2, cleft of mouth 3.1, postorbital 2.0, pectoral 0.9, snout-vent 102.5, predorsal 103.1, depth just before eye 2.4, at pectoral origin 5.4, at midpoint between pectoral and vent 15.0, at vent 3.8. Pectoral rays undeveloped, only a few dorsal and anal rays present at tip of caudal region, caudal rays 4 + 3. Teeth 1 + VI + 10 over 1 + VIII + 5 Myomeres 130 + 17 = 147 (133 + 18 = 151 in the paratype). Last vertical blood vessel at myomere 92. Anterior margin of gall bladder at myomere 20.

Body moderately elongate, much compressed except along head, deep, the depth about 6.5 in total length, reducing very rapidly at the head but more gradually along the posterior half of the body to tip of caudal region. Head short, about 21 in total, not conspicuously distinct from trunk; snout acute, 2.3 in head, its dorsal profile slightly concave; nasal organ close in front of eye, with distinct nares; eye circular, contained twice in snout or four times in head; cleft of mouth slightly oblique, extending to below middle of pupil; teeth robust, not excessively acute, the smaller ones curved forward a little at their tips, distributed as follows:—one large anterior grasping tooth followed by six large teeth and 10 much smaller ones, the pattern similar in the lower jaw. Pectoral fin short, about half the length of snout, rounded, delicate; dorsal fin originating about 20 segments in advance of level of vent, anal fin very short.

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Pigmentation in formalin as follows:—an oblique line of minute, compact, somatic elongate chromatophores on each myoseptum below the lateral line, reaching 20–24 in number at the midpoint of the body, briefly separated from a row of similar spots above the angle of each myoseptum below the lateral line (see text-fig 5, H) reaching a maximum of about 12 spots; a row of up to 12 similar spots above the angle of each myoseptum above the lateral line (text-fig. 5, G); irregularly scattered ventral, somatic chromatophores in the order of four per segment before the level of the gall bladder; a row of minute, compact, splanchnic chromatophores on each kidney duct above the intestine; a few diffuse chromatophores along the dorsal midline; scattered pigment on the bases of the terminal dorsal and anal rays and over the base of the caudal fin; halfway along the midlateral line an oval patch of numerous, minute, somatic chromatophores but this only occurs in the larger specimen and its presence may be abnormal; chorioid pigment present.

Vertical blood vessels to the viscera very numerous, beginning at the 5th myomere and occurring every two or three myomeres to the 92nd myomere. Gall bladder spherical. End of intestine with about 10mm trailing free from the body wall. (L. scalarum = ladder, in reference to the ladder-like pattern of the rows of pigment spots).

Remarks: The present species conforms well in possessing a round eye, short dorsal and anal fins, a posterior vent and rows of chromatophores on the myosepta below the lateral line with Anagoinae-type leptocephali. It has no scattered lateral chromatophores as in the larva previously referred to Alloconger anagoides and has the last vertical blood vessel at the level of myomere 92, compared with myomere 68 in L. ?Alloconger anagoides. In addition, the new species has additional lines of minute chromatophores in two places on each myoseptum. As far as I am able to determine from the literature there is no known species of Leptocephalus which has this remarkable pattern of lateral pigment. L. scalaris is therefore unique amongst congrid leptocephali. Ancona (1928, p. 32) describes L. macrenteron which has the posterior part of the intestine free from the body (as in the present species) but without the additional pigment on the myosepta. I believe this pigment to be abnormal in both species and that L. macrenteron is referable to L. Ariosoma mauritianum.