The genus Anguilla Shaw, the sole representative of the Family Anguillidae, has become, with the exhaustive researches of Danish scientists, the most intimately-known genus of eels. The two Atlantic species A. anguilla (L.) and A. rostrata (Le Sueur) were studied thoroughly by Johannes Schmidt over a long period of years, initiating a great deal of further work. His collections formed the basis of a definitive study of the systematics of the genus by Ege (1939), and Jespersen (1942) followed with a detailed account of the leptocephali of many of the Indo-Pacific species of the genus. A considerable amount is nevertheless still to be added, especially concerning the biology of the Southwest Pacific species which, because of limited material, was treated rather briefly by Jespersen.

Ege (1939) has established that there are six Anguilla species present in the Southwest Pacific. Four of these are long-finned species—that is, with the origin of the dorsal fin conspicuously in advance of the level of the anal origin. These page 4

Text-fig. 1.—L. Anguilla megastoma, 26.4mm total length, IFO St 56–4–3 Fig A— Lateral view, to show distribution of major vertical blood-vessels, intestine and myomeres at level of vent. Fig. B—Lateral view of head. Fig. C—Lateral view of caudal region.

page 5 are: A. megastoma Kaup with an average of 112 vertebrae and known from the Solomons to Pitcairn; A. marmorata Quoy & Gaimard with about 106 vertebrae and distributed widely throughout the Indo-Pacific from Africa to the Marquesas but not reaching south of New Caledonia or New Guinea in the Southwest Pacific; A. reinhardti Stcindachner with about 108 vertebrae, confined to New Caledonia and eastern Australia from Cape York to Victoria; and A. dieffenbachi Gray with about 113 vertebrae, restricted to New Zealand. The remaining two species are short-finned eels with the dorsal origin only a little in advance of the level of the anal origin. These are: A. australis Richardson with about 112 vertebrae and present in Fiji, New Caledonia, Southeast Australia and possibly Tahiti; and A. obscura Günther with about 104 vertebrae, occurring from Tahiti through Fiji, New Caledonia, North Queensland and New Guinea.

Despite this widespread occurrence of so many species of Anguilla in the South Pacific only four anguillid leptocephali have ever been recorded from this area; these were from the Dana collection (see Jespersen, 1942, pp. 13–15). By contrast, nearly 1500 specimens of Anguilla larvae were taken by the Dana in the whole of the Indo-Pacific. The South Pacific area was widely explored by this vessel during the months of October, 1928, to March, 1929, and Jespersen assumes that the scarcity of Anguilla larvae in this area may have been due to the time of year when the trawling took place. The larvae described here, 12 in number, therefore make a significant addition to knowledge of the South Pacific species of Anguilla. These larvae were collected in similar depths to those of the Dana larvae and in various months of the year, so that Jespersen's assumption is not supported by the present collection.

L. Anguilla megastoma (Text-fig. 1, A, B, C)

Material Examined. Two specimens, 23.7mm and 26.4mm total lengths; Institut Français d'Océanie Station 56–4–3; 12° 55′ S., 170° 04′ E.; 27/9/56 (2324 hours); horizontal tow in 70m; 0.5m net, No. 2 mesh.

Description. Measurements in mm: total length 26.4 (23.7), head 2.7 (2.7), snout 0.9 (0.9), eye 0.5 (0.6), upper jaw 1.0 (1.0), postorbital 1.3 (1.2), pectoral 0.9 (0.8), preanal 18.8 (17.4), predorsal 16.8 (16.2), depth just before eye 1.2 (1.0), depth at pectoral origin 2.2 (3.1), depth at midpoint between pectoral and vent 4.6 (4.2), depth at anal origin 4.4 (3.2). Branchiostegal and pectoral rays not obvious, dorsal and anal elements visible only near tip of caudal region, caudal rays 2 + 2 + 2 + 2 + 1. Teeth . Myomeres 72 + 39 = 111 (114). a–d = 7 (7). 1st vertical blood-vessel at 17th myomere, 2nd at 42nd and 3rd at 48th. Anterior margin of gall-bladder at level of 29th myomere.

Body elongate but not excessively so, much compressed, not very deep and tapering a little more gradually in front of midpoint of body. Head short, about one-ninth of total length, its lower profile indented at the throat to make the head region clearly differentiated from the trunk; snout short, equal to one-third of head length, acutely pointed with its dorsal profile conspicuously concave and anterior and posterior nares almost separated; eye moderate, oval, with its greatest diameter vertical and a little less than length of snout; gape oblique, extending to level of anterior margin of eye; teeth relatively large, very acute, eight in the upper jaw, projecting outside the six of the lower jaw and distributed as follows: a large, forwardly-projecting grasping tooth is preceded by a tiny, needle-like tooth placed almost on the dorsal surface of the snout and is followed by three large teeth which become progressively smaller; this series is followed by three noticeably smaller teeth, the most posterior of which is placed almost directly under the anterior rim of the orbit; the teeth of the lower jaw are similar in page 6 size and grouping to those of the upper with the most posterior tooth placed a little in advance of the level of the last upper tooth. Pectoral fin relatively large, equal to length of snout and elongate-oval in shape; base of fin thick and fleshy, web of fin thin, supported by delicate fin-rays which are poorly developed. Dorsal fin low, with only the radials visible at the end of the caudal region. Anal fin similar. Caudal fin conspicuously separated from the tips of the dorsal and anal fins.

Colour in preservative translucent, with black pigment confined to the chorioid of the eye.

Remarks. The two specimens described here belong unquestionably to the genus Anguilla. They agree very well with Group I (Anguillidae) of Ancona (1928, p. 102) in which the body is relatively short, high, in the form of an olive leaf, the intestine is straight and not festooned or swollen; the vent is about two-thirds of the length along the body; the dorsal fin originates a little in advance of the level of the vent; there is no pigmentation in the body except in very small specimens (5.0mm to 10.0mm). Both are long-finned larvae having seven myomeres between the dorsal and anal origins. They have a relatively high number of myomeres for Anguilla larvae, 111 and 114, suggesting that they are the young of either A. dieffenbachi (109–116 vertebrae) or A. megastoma (108–116 vertebrae). They were both collected at the same station, north-east of the New Hebrides, which is well outside the known distribution of A. dieffenbachi (a species restricted to New Zealand). Although the position of capture does not entirely rule out the possibility that they are the young of the latter species, since its breeding area is possibly as far north as New Caledonia, I am satisfied mainly for geographical reasons that the two larvae are the young of the other long-finned species with a high number of vertebrae—i.e., A. megastoma.

The two specimens of A. megastoma described above are evidently about half-grown, possessing only a few teeth (8–9) compared with the average full complement of about 18–20 in Anguilla larvae about to undergo metamorphosis. In both specimens the olfactory organ is not well developed, but in the larger the anterior and posterior nares are near to separation; the vertebral column is well chondrified; the vent is not greatly posterior; the heart is well developed, and the cranium well ossified.

L. Anguilla marmorata and L. Anguilla reinhardti

Material Examined. One specimen, 27.3mm total length; IFO St. Ep 27b(l) ; 17° 13′ S., 162° 30′ E.; 28/9/60 (0205 hrs); 2 oblique tows in 0–300m; 0.5m net, No. 2 mesh. One specimen, 27.6mm t.1.; IFO St. Ep 9b(l); 17° 40′ S., 157° 40′ E.; 17/9/60 (0206 hrs); 2 obl. tows in 0–300m. One specimen, 37.3mm t.1.; IFO St. S 6; 11° 51′ S., 159° 13′ E.; 11/6/62; 5ft midwater trawl (Isaacs-Kidd) ; ca. 95m. One specimen, 39.2mm t.1.; IFO St. P Bs 16; 12° 59′ S, 165° 42′ E; 13/11/58 (0311 hrs); 2 obl. tows in 0–300 m; 0.5m net, No. 2 mesh. One specimen, 41.4mm t.1.; IFO St. D 10; 14° 50′ S., 157° 52.5′ E.; 16/5/60 (2003 hrs) ; 2 obl. tows in 0–300m; 0.5m net, No. 2 mesh. One specimen, 43.6mm t.1.; IFO St. Ep 19b(1); 10° 24′ S, 160° 30′ E.; 24/09/60 (0204 hrs); 2 obl. tows in 0–300m; 0.5m net, No. 2 mesh.

Description. Measurements in mm: total length 39.2 (27.3–43.6), head 3.8 (3.1–4.0), snout 1.2 (1.1–1.7), eye 0.8 (0.9–1.0), upper jaw 1.9 (1.4–2.1), postorbital 1.9 (1.3–2.0), pectoral 0.9 (0.6–1.2), preanal 30.9 (21.3–33.6), predorsal 25.8 (19.6–31.1), depth just before eye 1.7 (1.5–2.1), depth at pectoral origin 3.4 (2.4–4.0), depth at midpoint between pectoral and vent 8.6 (5.0–8.8), page 7 depth at anal origin 6.8 (4.1–8.4). Branchiostegal and pectoral rays not obvious, dorsal rays before level of vent 89 (91 and 82 in the two largest specimens), total rays 256 (256 and 253), first dorsal ray at level of segment 62 (61 in the two largest specimens), anal rays 200 (183–225), caudal rays 3 + 2 + 2 + 2 (variable, usually 2 + 2 + 2 + 2). Teeth . Myomeres 73 + 34 = 107 (106–110). a–d = 9 (8–9). 1st vertical blood-vessel at 16 (15–17), 2nd at 37 (37–39), 3rd at 43 (43–44). Anterior margin of gall-bladder at level of 25th or 31st myomere.

Body elongate, but not excessively so, much compressed but relatively deep, its maximum depth contained a little more than four times in the total length, tapering equally in front of and behind midpoint of body. Head short, about one-tenth of total length, indented at the throat, pointed, with the dorsal profile slightly convex; anterior and posterior nostrils clearly separated; eye contained one and a-half times in snout, oval, with the greatest diameter vertical; cleft of mouth oblique, extending to level of middle of pupil; teeth conspicuous, very acute, 18 in upper jaw projecting outside those of lower jaw, distributed as follows: first tooth minute, needle-like, directed immediately forwards and placed on the anterodorsal surface of the snout above the second tooth, which is a much larger anteriorly-directed grasping tooth; these two are followed by a second series of large, needle-like fangs and a third of much smaller teeth to a point below the middle of the pupil; the teeth of the lower jaw are similar in grouping and size to those of the upper jaw. Branchiostegal rays not obvious. Pectoral fin large, about equal to vertical diameter of eye, rounded, base of fin fleshy but with the rays not obvious. Dorsal fin low with the rays well developed only in the larger specimens but the radials always countable. Anal fin a little higher than the dorsal. Caudal fin in the larger specimens well marked off from the dorsal and anal fins and with well developed hypurals and fin-rays.

Colour in preservative translucent with pigment restricted to the chorioid of the eye.

Remarks. These six specimens are long-finned larvae, having 8–9 myomeres between the origins of the dorsal and anal fins compared with about 5 in short-finned species. They have 106–110 myomeres. These two characters, taken together with the location of capture of the six larvae, restrict the identification to either A. reinhardti or A. marmorata. However, it is difficult to refer these larvae further to either one or other of these two species or both since the definitive adult characters are relatively insignificant and are not exhibited in the larvae. There is evidence, nevertheless, to show that these larvae represent two species. I have examined a large number of leptocephali of the Genus Gnathophis (Congridae) including a wide range of sizes for two species. In this case, the segmental level of the gall-bladder is the same in both species and does not change with growth. In the present six specimens, the two smallest larvae (27.3mm and 27.6mm) have the gall-bladder at the level of the 31st myomere, but in the other four specimens the gall-bladder is level with myomeres 24 and 25. From this I consider that there are two species in this particular group of six larvae. The two smallest larvae with a more posterior gall-bladder were collected in the northerly region of the area known for the adult A. reinhardti. The four larger were taken in the southern part of the known distribution of A. marmorata. Since the areas occupied by the adults overlap only in New Caledonia, and since two larval species are indicated, further work may confirm my proposed identifications.

Text-fig. 2.—L. Anguilla australis ?schmidti, 47.6mm total length, IFO St. 56–4–2. Fig. A—Lateral view, to show distribution of major vertical blood-vessels, intestine and myomeres at level of vent. Fig. B—Lateral view of head. Fig. C–Lateral view of caudal region.

L. Anguilla australis ?schmidti (Text-fig. 2, A, B, C)

Material Examined. One specimen, 24.6mm total length; IFO St. 56–4–2; 14° 37′ S., 170° 03′ E.; 26/9/56 (2122 hrs) ; horizontal tow in 10m; 0.5m net, No. 2 mesh. One specimen, 47.6mm t.1.; IFO St. P 60–2–1; 22° 38′ S, 168° 20′ E; 11/4/60 (1953 hrs); hor. tow in 50m; 0.5m net, No. 2 mesh.

Description. Measurements in mm: total length 47.6 (24.6), head 4.3 (2.8), snout 1.0 (1.2), eye 0.7 (0.6), upper jaw 1.6 (1.2), postorbital 2.4 (1.2), pectoral 1.1 (0.5), preanal 29.6 (19.2), predorsal 27.0 (18.2), depth just before eye 1.8 (1.2), depth at pectoral origin 3.4 (2.0), depth at midpoint between pectoral and vent 8.5 (4.2), depth at anal origin 9.4 (4.1). Branchiostegal rays 12 (−), pectoral rays 17 (−), dorsal rays before level of vent 26 (−), total rays 194 (−), 1st dorsal ray at level of myomere 58; anal rays 187 (−), caudal rays 2 + 2 + 2 + 2. Teeth none and . Myomeres 62 + 54 = 116 (112). a–d = 3 (2). Vertical blood-vessels at myomeres 17, 41, 48 (17, ? 48). Anterior margin of gall-bladder at myomere 27 in one specimen, obscured in the larger specimen.

Body not excessively elongate, much compressed except along the head but relatively deep with the maximum depth contained about five times in total length; tapering about equally in front of and behind the midpoint of the body. Head short, about one-tenth of total, slightly indented at the throat: snout about one-fourth of head, rounded, with a slightly convex dorsal profile and both nostrils well separated; eye contained 1.3 times in snout, oval, with the greatest diameter vertical; cleft of mouth oblique, extending to level of middle of pupil; teeth absent in the larger specimen, but eight small cavities remain in the lower jaw. Branchiostegal rays well developed and curving across the space in front of pectoral. Pectoral fin just less than snout and eye combined, rounded, base of fin fleshy. Dorsal fin low, with the radials visible throughout as well as most of the rays. Anal fin conspicuously higher than the dorsal. Caudal fin not greatly differentiated from the dorsal and anal.

Colour translucent with pigment restricted to the chorioid of the eye.

Remarks. These two leptocephali are short-finned, having the difference between the dorsal and anal origins equal to three myomeres. The two species of short-finned eels present in the south-west Pacific are A. australis with 108–116 vertebrae and A. obscura with 101–107 vertebrae. The two larvae have 112 and 116 myomeres and are therefore referred to A. australis. Two subspecies of A. australis have been recognised: A. australis australis Richardson in New South Wales, Victoria, Tasmania and Lord Howe Island and A. australis schmidti Phillipps from New Zealand and outlying islands, Norfolk Island, New Caledonia, Fiji, and possibly Tahiti. The larger specimen of these two larvae, almost at metamorphosis, was taken very close to New Caledonia and is probably A. australis schmidti. The smaller specimen was taken far from the area known for the adult of the Australian subspecies and is also tentatively referred to A. australis schmidti.

L. Anguilla australis ?australis

Material Examined. One specimen, 75.7mm total length; Aust. Mus. regd. no. IA.2363; McCulloch Reef, Great Barrier Reef, Queensland, between 17° S. and 19° S.; transitional larva.

Description. Measurements in mm: standard length 74.9, head 5.8, snout 1.0, eye 1.1, interorbital 1.0, upper jaw 2.3, postorbital 4.0, pectoral 1.3, preanal 41.8, predorsal 40.3, depth just before eye 2.0, depth at pectoral origin 3.2, depth at anal origin 5.2. Myomeres 52 + 60 = 112. a–d = 1.

Text-fig. 3.—Figs. A-C—L. Anguilla obscura, 49.6mm total length, IFO St. G 16. Fig A—Lateral view to show distribution of major vertical blood-vessels, intestine and myomeres at level of vent. Fig. B—Lateral view of head. Fig. C—Lateral view of caudal region. Figs. D-F—Anguilla australis australis, glass-eel, 57.9mm total length, Aust. Mus. regd. no. I.B.5289. Fig. D—Lateral view, to show distribution of deep pigment on spinal cord. Fig. E—Lateral view of head. Fig. F—Lateral view of caudal region to show deep pigment on spinal cord and scattered lateral pigment.

Body moderately elongate, compressed, tapering appreciably only at head and along posterior half of caudal region. Head short, about one-thirteenth of total length, not greatly differentiated from trunk; snout acute, one-sixth of head, projecting in front of lower jaw and turned noticeably downwards; nostrils well separated with the anterior one almost at tip of snout, the other just in advance of eye; eye round, about equal to length of snout; gape considerably oblique, extending to a point just in advance of pupil. Teeth difficult to distinguish. Pectoral a little longer than snout; dorsal low, originating only slightly in advance of level of vent; anal also low; caudal fin distinct from tips of dorsal and anal. Colour creamy brown with black pigment restricted to the chorioid of the eye.

Remarks. This specimen is a late leptocephalus which has taken on the elongate form of the elver. It has not yet become rounded in cross-section but is losing its transparency. The preanal myomeres number 52, compared with 39 in the elver. With a total of 112 myomeres and a short dorsal fin there is little doubt that the specimen belongs to A. australis and, considering its point of capture close in to the Queensland coast, to the Australian subspecies, A. australis australis. The specimen is not in the best condition and shows no distinctions from the larvae assigned to A. australis schmidti enabling certainty of subspecific identification.

Anguilla australis ?australis (Text-fig. 3, D, E, F), glass-eel.

Material Examined. Two specimens, 52.5mm and 57.9mm total lengths, Aust. Mus. regd. no. IB.5289; rock-pool, Forty Baskets Beach, Sydney; 12/6/61.

Description. Measurements in mm: total length 57.9 (52.5), head 6.0 (6.0), snout 1.4 (1.1), eye 0.6 (0.7), interorbital 0.3 (0.3), upper jaw 1.4 (1.7), postorbital 4.3 (4.1), pectoral 1.1 (1.2), preanal 20.0 (−), predorsal 19.8 (−), depth just before eye 1.0 (0.8), depth at pectoral origin 1.8 (1.8), depth at midpoint between pectoral and vent 1.5 (1.5), depth at anal origin 1.4 (1.7). Branchiostegal rays 12 (12), pectoral rays 19 (18), dorsal rays before level of vent 9 (8), total rays ca. 193 (211), anal rays ca. 186 (203), caudal rays 2 + 2 + 2 + 2 (2 + 2 + 3 + 2). Teeth . Myomeres 39 + 74 = 113 (110). a–d = 2 (2).

Body greatly elongate, cylindrical, compressed only near tip of caudal region, tapering only at snout and at tip of caudal. Head long, about one-tenth of total length, slightly swollen in front of pectoral but otherwise little differentiated from trunk; snout rounded, less than one-quarter of head length with anterior nostril far forward on tip of snout, posterior nostril a little in advance of eye; eye less than twice in snout or about seven times in postorbital, circular; gape oblique, extending to just behind forward margin of eye, lower jaw projecting for a distance equal to length of pupil. Teeth bluntly conical, short, sparse, uniserial, unlike those of the leptocephali; distributed as follows: on the maxilla five small teeth are followed by two larger ones posteriorly, while on the dentary there are ten small teeth anteriorly and two larger ones posteriorly. Pectoral fin about equal to snout, oval. Dorsal fin low, originating only a short distance in advance of the anal; anal fin also low, caudal fin well differentiated from the tips of the dorsal and anal fins.

Colour in preservative restricted to a few large melanophores on the lateral surface of the head, a continuous series of deeply-placed, expanded melanophores on the spinal cord beginning at the level of the pectoral fin through to the tip of the caudal region, a scattering of pigment laterally on the tip of the caudal region and on the caudal fin as well as a pigmented chorioid.

Remarks. The specimens described here are transitional elvers between Stage V and Stage VI of Strubberg (1913, p. 4); that is, they have surface pigment on page 12 the caudal, deep pigment on the caudal region of the spinal cord and neck, but the body is cylindrical. The two specimens, having two myomeres between the levels of dorsal and anal origins are short-finned and with a high number of myomeres, 110 and 113, can be referred to A. australis. They were collected at Sydney, New South Wales, and therefore fall well within the geographical range known for the Australian subspecies, A. australis australis.

L. Anguilla obscura (Text-fig. 3, A, B, C)

Material Examined. One specimen, 49.6mm total length; IFO St. G 16; 16° 52′ S., 166° 26′ E; 27/2/62; horizontal tow in 16m; 1m plankton net.

Description. Measurements in mm: head 4.0, snout 1.1, eye 0.9, upper jaw 1.8, postorbital 2.4, pectoral 1.0, preanal 36.1, predorsal 33.3, depth just before eye 1.4, depth at pectoral origin 3.0, depth at midpoint between pectoral and vent 8.8, depth at anal origin 7.6. Branchiostegal rays 8; pectoral rays not obvious; dorsal rays before level of vent 59, total rays 216, 1st dorsal ray at myomere 63; anal rays 204; caudal rays 2 + 2 + 2 + 2. Teeth . Myomeres 70 + 33 = 103. a–d = 5. Vertical blood-vessels at 17, 37, 43.

Body moderately elongate, much compressed, deep, with the greatest depth contained five times in total length. Head short, about one-eleventh of total length, rather depressed so that it is well differentiated from trunk; snout short, about one-fourth of head length, its dorsal profile convex; anterior and posterior nostrils well separated; eye about equal to length of snout, oval; cleft of mouth oblique, extending almost to level of posterior margin of eye; teeth conspicuous, very acute, 18 in upper jaw projecting outside those of lower jaw which number about 13, distributed as follows: first tooth of upper jaw small, needle-like, directed anteriorly and placed immediately above the second, much larger, anteriorly-directed grasping tooth; these two are followed by a series of four large teeth and a final series of 12 noticeably smaller teeth; lower teeth similar to those of upper jaw with the absence of the needle-like anterior tooth. Branchiostegal rays delicate and curving up around the operculum. Pectoral fin about 1.5 times diameter of eye, rounded, fleshy. Median fins well developed with fin rays and radials clearly visible.

Colour in preservative translucent with black pigment restricted to the chorioid of the eye.

Remarks. The specimen belongs to a short-finned species, having five myomeres between the levels of the dorsal and anal origins. The myomeres number 103, and this character fully identifies the specimen with A. obscura which has 101–107 vertebrae. The specimen is well advanced in development having very nearly a full complement of teeth, well developed fin-rays, etc., and the vent placed half way between the midpoint of the body and the tip of the caudal region.