BERTELSEN: CERATIOIDEI 



327 



olfactory organs is retarded. In males the body elongates, larval 

 teeth are lost, the denticular teeth develop, and eyes and/or 

 olfactory organs increase in relative size. 



The larvae have been referred to genera, subgenera or species- 

 groups on basis of (1) meristic characters (especially number of 

 dorsal and anal fin rays); (2) osteological characters (especially 

 number of branchiostegal rays and pectoral radials and shape 

 of head of hymandibular, pelvic bones and opercular bones); 

 and (3) pattern of subdermal pigmentation. The pattern is re- 

 tained under the pigmented skin of post-metamorphic juveniles 

 which have acquired adult characters (Bertelsen, 1951). In most 

 genera the smallest larvae observed are 2.5-3.5 mm. At these 

 stages, in which no distinguishing characters other than pig- 

 mentation may be developed, identification is based on com- 

 parison with developmental series of older larvae. 



Meristic characters.— The 2-3 mm smallest known larvae have 

 an almost straight notochord and almost undifferentiated fins. 

 The fin rays of the unpaired fins are laid down early and the 

 full number is usually present in larvae of 3-4 mm SL of the 

 numerous species where the number of dorsal rays does not 

 exceed 8. The pectoral fin rays are laid down somewhat later 

 than those of the unpaired fins, and the lowermost rays are rarely 

 discernible in specimens of less than about 5-6 mm. Caulo- 

 phrynidae and the ceratiid genus Cryptopsaras have 8 caudal 

 fin rays, all others have 9 ( 10 in some specimens of Neoceratias). 

 The 9th (lowermost) ray is rudimentary or short (less than half 

 the length of the 8th ray) in Linophrynidae, Gigantactinidae, 

 and Ceratias. 



Except in the three genera in which the number of rays in the 

 anal and/or dorsal fin exceeds 10 (Caulophryne. Neoceratias. 

 and Melanocelus, cf Table 89), the intraspecific variation of the 

 number of fin rays in these fins is small, rarely more than ± 1 . 

 Significant differences in numbers of dorsal and anal fin rays 

 have been found between species within the genera Caulo- 

 phryne. Gigantactis, and Melanocetus and between genera in 

 the families Caulophrynidae, Gigantactinidae, and Oneirodi- 

 dae. 



Pectoral fin rays number 12-23 in all ceratioids (except Cten- 

 ochirichthys with 28-30). As an intraspecific range of variation 

 of 5 to 7 fin rays has been observed, this character may aid 

 identification only in exceptional cases. 



All reported vertebral counts of Ceratioidei fall within the 

 range of 19 to 24, the highest number in Neoceratiidae, the 

 lowest in Linophrynidae. The limited number of observations 

 does not permit an evaluation of the diagnostic value of differ- 

 ences within this range. 



Morphology.— The head and body of larval Ceratioidei are sur- 

 rounded by inflated transparent skin. Due to this balloon-like 

 envelope, their shape varies from nearly spherical, with greatest 

 width and depth of body reaching 80-90% SL, to elongated or 

 pear-shaped, with body depth of 40-60% SL. 



The inflation of the skin varies with preservation, but gen- 

 erally its greatest development is found in Caulophrynidae (Fig. 

 167 A), Gigantactinidae (Fig. 168A, B), and Himantolophidae 

 (Fig. 169 A, B); less pronounced in Neoceratiidae (Fig. 167B), 

 Ceratiidae (Fig. 168C-E) and Oneirodidae (Fig. 170). No dis- 

 tinct change has been observed in the relative development of 

 the inflation during larval life. In larvae of most genera, the 

 relative length of head, measured to base of pectoral peduncle, 

 is about 50% SL. In Oneirodidae and Linophrynidae it is some- 

 what less (generally about 45%) and is shortest in Neoceratias 



(35-40%). In the late larval stages of males, the elongation of 

 the body may start before other metamorphic characters have 

 appeared. 



In larval Ceratiidae, the vertebral column is more strongly S- 

 shaped than in other families, resulting in a characteristic hump- 

 backed appearance of these larvae (Fig. 168C-E). The larvae of 

 Caulophrynidae (Fig. 167 A) and Gigantactinidae (Fig. 168A, B) 

 differ distinctly from those of other Ceratioidei in the size of 

 the pectoral fins, which have lengths of 40% to nearly 60% SL, 

 measured from base of pectoral peduncle. In the other families, 

 this length is generally 20-25% SL and does not exceed 30% 

 SL. 



Pigment.— The subdermal pigment occurring in larval Cera- 

 tioidei is usually separated into four more or less well-defined 

 main groups: (I) peritoneal; (2) opercular; (3) dorsal; and (4) 

 caudal-peduncular. 



In Neoceratias (Fig. 167B) and some linophrynids (Haplo- 

 phryne. Fig. 167D), the subgenera of Linophryne: Stephano- 

 phryne {Fig. 167F). and Rhizophryne (Fig. 167C), the subdermal 

 pigment forms dorso- and ventrolateral bands along the body. 



In all species in which one of these main groups occur, they 

 are generally laid down in the youngest larvae as a few small 

 and scattered melanophores which during larval development 

 gradually increase in size, number, and in area covered. 



Additional groups of melanophores occur in some taxa (for 

 instance on base of pectoral peduncle in Rhynchactis, Fig. I68B; 

 internally in fin rays of Pentherichthys, Fig. 1 70E; on the pos- 

 terior angle of lower jaw in Stephanophryne, Fig. I67F; and on 

 a swelling of the outer transparent skin in front of the dorsal fin 

 in some Himantolophus. Fig. I69B). 



Complete lack of pigment is found in Ceratias (Fig. 168E), 

 some Gigantactis, and the linophrynid genus Borophryne (Fig. 

 167G). Besides in these, peritoneal pigment is absent only in 

 Neoceratias. In all others, this group is laid down on the dorsal 

 side of the peritoneum of the youngest larvae and with growth, 

 gradually spreads to its lateral and posterior sides. 



Pigmentation of the opercular region varies greatly between 

 taxa. It is absent or weakly developed in most genera, dense 

 and in characteristically different patterns in genera of Onei- 

 rodidae (for instance Oneirodes, Fig. 1 70A; Dolopichthys. Fig. 

 170B; Microlophichthys. Fig. 170F; Thaumatichthys, Fig. 169F; 

 and Cryptopsaras, Fig. 168C, D). 



Besides in the completely unpigmented larvae mentioned 

 above, dorsal pigment is absent in Caulophryne, Neoceratias, 

 and all Linophrynidae. In all others it is laid down on the antero- 

 dorsal part of the body. Varying between genera in density and 

 coverage, it spreads from there and may laterally reach and 

 overlap the dorsal part of the peritoneal pigmentation and pos- 

 teriorly the bases of the dorsal and anal fins, in some becoming 

 confluent with the pigment group of the caudal peduncle. 



In occurrence, position and development in relation to larval 

 length, pigmentation on the caudal peduncle shows very distinct 

 differences between genera (cf for instance Fig. 1 70) or between 

 subgenera or species-groups (cf for instance Figs. 167E, F; 169 A, 

 B; 170C, D). 



Other larval structures. — Fe\\\c fins. — In contrast to all other 

 Ceratioidei, the larvae oi Caulophryne have pelvic fins with well- 

 developed fin rays (Fig. 167A). The longest of the 3-4 pelvic 

 fin rays increase in relative length from about 45% SL in the 

 smallest larvae (3 mm) to about 60% SL in the largest (7.5 mm). 

 In the only known free-living stage of a metamorphosed male 



