246 



ONTOGENY AND SYSTEMATICS OF FISHES-AHLSTROM SYMPOSIUM 



CAV 



Fig. 127. Larvae, juveniles and adult of Scopelarchidae. (A. B) Rosenblattichthys volucris. A = 14.5 mm SL, B = 26.0 mm SL, letters refer to 

 pigment spots; (C, D) Scopelarchoides nicholsi, C = 1.5 mm SL, D = 23.0 mm SL, letters refer to larval pigment spots; (E, F) Benthalhella denlata. 

 E = larva, 42.8 mm SL, F = transforming specimen, 53.0 mm SL, arrows indicate position of anus; (G) Scopelarchus guenlhen. juvenile, 48.5 

 mm SL, DS = dermal pigment stripes; (H) Scopelarchus analis. adult, 1 12.5 mm SL. 



large and massive, exceeding 30% of the SL in Rosenblattichthys, 

 and large but not as large in other genera. The eye is elliptically 

 narrowed, and initially small in comparison with the size of the 

 bony orbit. The interorbital is initially broad and narrows during 

 transformation. Development of the eyes is described for Ben- 

 thalhella infans in Merrett et al. (1973). The snout is pointed. 

 The mouth is large and low, with teeth appearing in very small 

 larvae. The most striking changes take place during a period of 

 transformation, which, as described below, can either be within 

 a very short interval (ca. 10 mm in Benthalhella dentata) of 

 growth (any statements implying time sequence are based solely 

 on increments of length) as in Benthalhella, or over a long (20 

 mm) to very long (50 mm) interval. 



Meristic characters.— Counts of fin rays (Table 65) do not differ 

 between larval and adult specimens. Most scopelarchid species 

 can be uniquely distinguished from all other species on the basis 

 ofmeristic characters alone (Johnson, 1974b: 14). Rosenhlattich- 

 ihys is unique in precocious ossification of the pectoral fin rays, 

 well in advance of the pelvic or median fins (except caudal). In 

 all other scopelarchids the lowermost 5 or 6 pectoral fin rays 

 are the last to be formed and the order of fin ray ossification is 

 caudal > dorsal, anal, dorsal pectoral > pelvic > ventral pec- 

 toral. As in all inioms the caudal is formed of 10 + 9 principle 

 rays. In Scopelarchoides and Rosenhlattichthys the pelvic fins 

 appear as buds on the midlateral abdominal cavity wall, well 

 above the level of the intestine. In Benthalhella and Scopelar- 



chus the pelvic fin buds appear ventrolaterally, at or beneath 

 the level of the intestine. In Benthalhella (except B. macropinna) 

 the pelvic fin insertion in larvae is distinctly in advance of the 

 dorsal fin origin. In other scopelarchid larvae the pelvic fin 

 insertion is beneath or behind the dorsal fin base (but comes to 

 be slightly in advance of dorsal fin origin in adult Rosenhlattich- 

 thys and distinctly in advance of dorsal fin origin in all adult 

 Benthalhella). The adipose fin develops within the dorsal finfold 

 which extends between the dorsal and caudal fin in small larvae. 

 In adults the adipose fin is inserted over the posterior one-third 

 of the anal fin base (except B. dentata where inserted posterior 

 to a vertical through base of last anal-fin ray). Ventral finfold 

 extending from vent to anal-fin origin in smaller larvae, and is 

 completely reabsorbed in early transformation. 



Peritoneal pigment sections. — \n all adult scopelarchids (except 

 B. elongata) the gut is enclosed by a uniform tube of brown to 

 jet-black pigment. In larvae this pigment appears in discrete 

 sections (except in Benthalhella where peritoneal pigment is 

 lacking prior to transformation) and in a conformation char- 

 acteristic for each genus or group of apparently related species. 

 All larvae larger than 20 to 22 mm possess peritoneal pigment 

 (except in Benthalhella). One section only, unpaired, forming a 

 saddle-like canopy over the gut, is present in Rosenhlattichthys, 

 Scopelarchoides signifer, and S. clima.x (larvae of S. kreffii are 

 unknown). Three sections, a single anterior section as above and 

 two paired posterior sections are found in Scopelarchoides nich- 



