KAWAGUCHI AND MOSER: STOMIATOIDEA 



181 



pairs and increasing in numbers with development to cover the 

 entire dorsum; paired ventral series develop, initially poste- 

 riorly, and increase in numbers so that all myomeres have me- 

 lanophores on the ventral surface; pigment on brain, snout, 

 lower jaw, gular-isthmus region, otic region, caudal fin, and in 

 vague rings along trailing gut. Ahstostomias larvae were iden- 

 tified initially by E. H. Ahlstrom. 



Photostomias giternei (Fig. 93B). — larvae reach about 30 mm; 

 morphology similar to A. scintillans except eyes smaller and 

 narrower and pelvic fins somewhat elongate; body pigment con- 

 sists of a series of 8 minute dorsal melanophore pairs and 8 

 slightly larger opposing pairs along the ventral surfaces of the 

 myomeres; melanophores at lower jaw symphysis, large mela- 

 nophore on each pectoral fin base, sparse melanistic rings along 

 trailing gut. 



Malacosteid C (Fig. 93C). — intact specimen (captured by Dr. 

 Richard Harbison, WHOl) has morphological and meristic 

 characters of malacosteid larvae but lacks pigment except on 

 the extensive gut. Shallow capture locality of this specimen and 

 our capture of large A. scintillans larvae in MANTA nets in- 

 dicates late-stage malacosteid larvae have a shallow distribution 

 in the water column. 



Idiacanihidae (Fig. 94j. — Brauer ( 1 906, 1 908) described the re- 

 markable larvae of Idiacanthus and named them Slylophthal- 

 mus paradoxus. Beebe ( 1 934) correctly identified the larvae and 

 described them in detail. Idiacanthus larvae are extremely slen- 

 der, reaching a length of 35-70 mm depending on the species. 

 Other characteristics are: elongate and extremely flat head; el- 

 liptical eyes on long stalks with cartilaginous supporting rods; 

 stalk length up to 27% of body length in /. antrostonms (Weihs 

 and Moser, 1981); gut slender, deflected at anal fin origin and 

 trailing; finfold small; dorsal fin begins forming in preflexion 

 larvae; dorsal fin larger than anal fin and slightly in advance of 

 it in postfiexion larvae; during transformation, rays added se- 

 quentially anteriad so that in adults the dorsal extends about -A 

 of the body length and the anal about 'A; pectoral fins well 

 developed but lost at transformation and pelvic fins develop in 

 transforming females, but not at all in males; pigment pattern 

 consists of a melanophore on the posterior margin of each hy- 

 paxial myomere, spreading into the myosepta when expanded, 

 several elongate internal blotches in the isthmus region, and a 

 series of melanophores along the trailing gut; adult males of /. 

 fasciola reach 32-42 mm SL, lack teeth and paired fins and have 

 relatively larger eyes and an enormous luminous gland. 



Relationships 



Information on larval characters of 18 of the 26 stomiatoid 

 genera recognized by Fink (this volume), representing all 6 of 

 the families recognized by Weitzman (1974), permits some pre- 

 liminary generalizations and conclusions: (1) Larvae of Sto- 

 miatidae and Chauliodontidae are similar in morphology and 

 are distinct from other stomiatoids. Pigmentation provides fur- 

 ther evidence of this; Chaidiodus larvae are unique among known 

 stomiatoids in lacking pigment after the yolk-sac stage and the 

 median series of gut melanophores of Stomias also appear to 

 be unique. (2) Larvae of Astronesthidae are diverse in mor- 

 phology and pigmentation and most of the larval specializations 

 that appear in other stomiatoid families are found among as- 

 tronesthid genera. Larval specializations of some genera (e.g., 

 ornamented trailing gut, trailing gut deflected at mid-body, rud- 

 der-like finfolds) are not found elsewhere in Stomiatoidea. Het- 

 erogeneity of larval characters in Astronesthidae supports Fink's 

 view that the group is paraphyletic. (3) In the Melanostomia- 

 tidae, larvae of Melanostomias. Photonectes. Echiostoma. 

 Oposlomias. Flagellostomias. Odontostomias and Leptostomias 

 are similar in morphology, have paired melanophore series on 

 the dorsum, and differ chiefly in head size, body depth, and in 

 the extent of myosepta pigment. Tactostoma larvae have the 

 characters of this group of genera except that the body is ex- 

 tremely slender and the pigmentation is lost in the postfiexion 

 stage. Larvae of Battiophilus difler from those of the above group 

 in a number of characters (voluminous gut with specialized 

 terminal section, melanophore series on the ventral surface of 

 the myomeres, lack of myosepta pigment). Larvae of Eustomias 

 are different from all known larvae of Melanostomiatidae in 

 having a trailing gut, flat head and snout, and a pigment pattern 

 consisting of a median series of up to 11 large melanophores 

 on the dorsum. Except for this latter feature, Eustomias larvae 

 are similar to those of Malacosteidae. (4) Idiacanthus larvae 

 have a combination of characters unique among stomiatoids. 

 The stalked eyes are autapomorphic. Larval characters provide 

 no support for Fink's hypothesis that this genus is closely related 

 to Tactostoma. 



Ocean Research Institute, University of Tokyo, 1-15-1, 

 MiNAMiDAi, Nakano-ku, Tokyo 164, Japan, and Na- 

 tional Marine Fisheries Service, Southwest Fisheries 

 Center, 8604 La Jolla Shores Drive, La Jolla, Calif- 

 ornia 92038. 



Stomii forms: Relationships 



W. L. Fink 



STOMIIFORMS are well known as a major component of 

 the midwater oceanic fauna. Past concepts of their rela- 

 tionships to other primitive euleleosts were reviewed by Fink 

 and Weitzman (1982), but in brief in this century, they have 



been considered isospondyls (Parr, 1927; Regan, 1923; Morrow, 

 1964) or, more recently, salmoniform protacanthopterygians 

 (Greenwood et al., 1966). In 1973, Rosen placed these fishes as 

 a separate order (Stomiatiformes) within the Neoteleostei, as 



