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

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

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.