AHLSTROM ET AL.: ARGENTINOIDEI 



169 



at various lengths by different species. Schmidt (1906c) reports 

 complete transformation at about 50 mm in A. sphyraena and 

 at a much larger size in A. silus. Size at completion of trans- 

 formation in Glossanodon species is also in the 50-100 mm size 

 range (Nishimura, 1966). 



Microstomatids develop a lustrous guanine layer on the in- 

 tegument in late larvae and some species develop distinct ju- 

 venile pigmentation. In Mil rosloma juvenWcs the region of the 

 body from the dorsal fin origin posteriad is more darkly pig- 

 mented than the rest of the body, and grades to a solid black 

 pigment at the caudal fin base. Juveniles of some Nansenia 

 species develop heavy melanistic pigment at the base of the 

 caudal fin and often at the base of the adipose fin (Schmidt, 

 1918; Kawaguchi and Butler, in press). 



Bathylagids have a direct transformation and undergo a marked 

 morphological change from the slender larval form to the ju- 

 venile form, characterized by a large head and eyes and deeper 

 body. The gut becomes coiled and covered by a black peritoneal 

 sheath. The head becomes heavily pigmented but the body is 

 slower to develop the black pigment characteristic of all Bath- 

 ylagiis species (other than the B. stilbnis group) and, in species 

 such as B. euryops and B. nulleri. the large larval melanophores 

 are visible in specimens up to 30 mm and 50 mm respectively. 



In the deep-bodied opisthoproctid genera transformation to 

 the juvenile stage is marked by deepening of the body and at- 

 tainment of melanistic integument and large scales. Cohen ( 1 960) 

 described the large (up to 124 mm) transitional specimens of 

 Bathylychnops which are semi-transparent and retain the large 

 larval pigment blotches. Sexually mature specimens of Doli- 

 chopteryx are semi-transparent, have a membranous body en- 

 velope, poorly developed musculature, an exposed gut covered 

 only by peritoneum, weakly attached fins and melanistic pig- 

 ment of the type usually associated with larvae (Cohen, 1960). 



Relationships 



Our survey of argentinoid ontogenetic characters provides 

 insight into some of the systematic questions posed at the be- 

 ginning of the paper. A close relationship between argentinoids 

 and alepocephaloids is not supported since the latter hatch from 

 large eggs (estimated at 3-4 mm based on size of yolk-sac lar- 

 vae), have direct development, and share no specialized onto- 

 genetic characters with argentinoids. Four major argentinoid 

 lineages can be defined by specializations of the eggs and larvae 

 and thus four families recognized: Argentinidae, Microstoma- 

 tidae, Bathylagidae, and Opisthoproctidae. Argentina and Glos- 



sanodon have generalized larvae except that all known species 

 have distinct lateral series of melanistic blotches or bands, not 

 found elsewhere among argentinoids. The pattern of banding 

 does not separate the two genera. 



All known bathylagid eggs have multiple oil globules. A num- 

 ber of bathylagid groups are apparent from larval characters: 1) 

 niillcri, 2) slilhms-schmidti-iirotranus, 3) euryops- pad ficus-ant- 

 arcticus, 4) hericoides-longirostris, 5) wesethi-argyrogaster-ni- 

 grigenys. Of these groups, stilbius-schmidti-urotranus has the 

 most generalized morphology and pigmentation, lending no 

 support for its separation as a distinct genus. 



Opisthoproctid larvae share a number of neotenic features, 

 including a saccular stomach. Except for body shape, Dolichop- 

 teryx shares more derived larval characters with the deep-bodied 

 genera than with Bathylychnops. and the latter has a number of 

 characters unique to opisthoproctids. Division of the family 

 based on body shape is not supported by ontogenetic evidence. 



Ontogeny offers little information on species composition of 

 genera, because only a fraction of argentinoid eggs and larvae 

 are known. However, egg and larval characters clearly separate 

 Atlantic and Pacific Microstoma as distinct species. Bathylagits 

 hericoides larvae from the Atlantic and Pacific are indistinguish- 

 able. The same is true for B. longirostris from all oceans. Bath- 

 ylagus nigrigenys and B. argyrogaster larvae are indistinguish- 

 able, lending support for a single circumtropical species. 

 Bathylagus stilbiiis eggs and larvae are indistinguishable from 

 those of B. urotranus. 



We have attempted to analyze the distribution among four 

 nominal groups of argentinoids, of 14 characters, four of which 

 are taken from developmental stages and 10 from the adult 

 (Table 42). We have used teleosts in general and osmerids as 

 our outgroup following Fink and Weitzman ( 1 982). Distribution 

 of character states are presented in Table 43. 



A possible arrangement of groups based on the fewest number 

 of character reversals is presented in Figure 88. Opisthoproc- 

 tidae appears to be a well-founded family. More precise inter- 

 pretation of the inter-relationships and nomenclatural ranking 

 for argentinids, microstomatids, and bathylagids requires ad- 

 ditional data. 



(H.G.M.) Southwest Fisheries Center, P.O. Box 271, La 

 JoLLA, California 92038; (D.M.C.) Natural History 

 Museum Los Angeles County 900 E.xposition Boule- 

 vard, Los Angeles, California 90036. 



Stomiatoidea: Development 

 K. Kawaguchi and H. G. Moser 



FISHES of this group of midwater predators are characterized 

 by their dark coloration, serial photophores, large jaws, 

 fang-like teeth, and chin barbels. Traditionally they have been 

 grouped in six families allied to the lightfishes and hatchetfishes 

 (Weitzman, 1974), and together are now considered monophy- 



Ictic and given ordinal status (Rosen, 1 973; Fink and Weitzman, 

 1982). Fink (this volume) gives evidence for reducing the six 

 stomiatoid families to one. Because knowledge of stomiatoid 

 ontogeny lags far behind that of the adults, for convenience of 

 discussion we use Weitzman's (1974) grouping of the families 



