OKIYAMA: MYCTOPH I FORMES 



211 



Fig. 109. (A) Aulopus japonicus. 1 1.5 mm SL, from Okiyama (1974b); (B) Aulopus sp., 12.3 mm, from Okiyama (1974b); (C) Neoscopelus 

 sp., 7.9 mm, from southwestern Japan, Ocean Research Institute (ORI) collection; (D) Scopelengys dispar, 6.3 mm, from Okiyama (1974b); (E) 

 Chlorophlhalmus sp., 17.1 mm, from Indian Ocean, ORI collection; (F) Chlorophthalnms (?) sp., 7.5 mm, from Kuroshio waters off Japan, ORI 

 collection. 



of both larvae and adults is well known (Okiyama. 1972; Parin 

 and Belyanina, 1972; Sulak, 1977). 



Bathymicrops represents the deepest living myctophiform. 

 Two species. B. regis and B. brevianalis, are known from ex- 

 tremely limited material from 4225-5900 m (Nielsen, 1966; 

 Merrett and Marshall, 1981). Pelagic eggs are unknown. A total 

 of five larvae and juveniles (13.0-70.0 mm) are available; the 

 smallest two larvae (13.0, 14.7 mm) from Hawaiian waters are 

 unidentifiable; a 20 mm larva from the North Atlantic (=Sto- 

 miatella B in Roule and Angel, 1930: PI. 1, Fig. 7) is ascribed 

 to B. regis; the largest two juveniles (62.5, 70.0 mm) from the 

 tropical Pacific are tentatively identified as B. brevianalis. 



Despite conspicuous variation among specimens, scattered 

 melanophore patches and an extremely slender body are diag- 

 nostic for this genus. The precocious pectoral fins are greatly 

 elongated even in the smallest larva, but the raised bases of the 

 dorsal and anal fins and the prominent finfolds are peculiar to 

 the advanced stages, which also have reduced eye size and a 

 slightly shorter gut. Size at metamorphosis is unusually large, 

 attaining 70-90 mm. 



Bathypterois is the most speciose genus in this family. Three 

 subgenera (Benthosaurus, Bathypterois and Bathycygnus) and 

 18 species are currently included (Sulak, 1977). Known bathy- 

 metric ranges are 250-5,990 m. Published information of the 

 developmental stages is scant. Pelagic eggs are not known. A 

 single larva of 14. 1 mm (Okiyama, 1974b) was identified as B. 

 {Bathycygnus) longipes by Sulak (1977). As stated before, the 

 known early stages of "Aulopus filamentosus" are all referable 

 to those of Bathypterois. probably B. (Bathypterois) mediter- 

 raneus in view of their localities. Complete series of early stages 

 are confined to this species, but at least three additional larval 

 forms are now available. These known larvae share the distinct 

 forward shift of the ventral hypural elements in addition to the 

 features given in Table 58. 



Known larvae are provisionally divided into two groups on 

 the basis of the peritoneal pigment sections, those with many 

 sections and those which lack peritoneal pigment. Except for 

 two larvae, B. (B.) longipes and B. (Benthosaurus) viridensis 

 (33.1 mm) from the Atlantic (Fahay, 1983), all specimens have 



the former character state. The number of peritoneal pigment 

 sections can be a useful tool in discriminating the lai^ae, but 

 ranges of variation often overlap among species. A western Pa- 

 cific form with 12-18 pigment sections bears close resemblance 

 to B. (B.) mediterraneus larvae whereas decidedly lower myo- 

 mere counts of the former (45-48) readily separate these two. 

 B. viridensis larvae have, in addition to the complete absence 

 of the peritoneal pigment sections, several peculiar features such 

 as a slightly telescopic eye, a protruding gut, and a long anal fin 

 and short tail. Comparison with the smallest demersal specimen 

 (43 mm) of the same species (Sulak, 1977) indicates that prin- 

 cipal metamorphic changes include the absorption of the pro- 

 duced gut, lengthening of the posterior body and fin shrinkage. 

 This may represent the most pronounced metamorphosis in this 

 genus, since less remarkable transformation predominated in 

 the other species. Identification of the other larval types remains 

 to be determined. 



Notosudidae (Fig. 1 J lA-B). — Bertelsen et al. ( 1 976) extensively 

 revised this oceanic midwater family, including information on 

 early developmental stages of all species (except Scopelosaurus 

 cradockei'). Supplemental information on the early stages is 

 available in Ozawa (1978). Pelagic eggs are unknown. Maturing 

 ovarian eggs of Ahliesaurus (ca. 0.3 mm in diameter) and Lu- 

 ciosudis (0.4-0.5 mm) suggest that pelagic eggs are uncommonly 

 small for this order. 



General characteristics of these larvae are extremely similar 

 throughout the family: long, slender subcylindrical body, be- 

 coming increasingly compressed toward the tail; markedly de- 

 pressed head with wedge-like snout; posteriorly protruding lobes 

 in corpus cerebelli; narrow eye with longer horizontal axis; a 

 more or less distinct conical mass of choroid tissue on the pos- 

 terior part of slightly stalked eye; anus at about midbody (except 

 .4hliesaurus) widely separated from anal fin origin; slight in- 

 crease of gut length with growth during the early larval stages; 

 absence of the peritoneal pigment. Maxillary teeth peculiar to 

 larvae help diagnose this family but are not unique (see, Au- 

 lopidae). Possible sequence of fin formation is CA-D-P.-Pj, 



