JOHNSON: SCOPELARCHIDAE 



247 



olsi. S. danae. and Scopelarchus. However in S. nicholsi and 5. 

 danae the posterior sections appear significantly "later" and 

 appear above (S. danae) or anterior (S. nicholsi) to the pelvic 

 fin bases. In Scopelarchus a.\\ 3 sections appear in near synchrony 

 and the posterior sections appear well to the rear of the pelvic 

 fin bases. In all cases the pigment section(s) expand during trans- 

 formation and for all genera except Benihalhella the completion 

 of transformation can be defined as acquisition of the adult state 

 of a complete and unbroken tube of peritoneal pigmentation. 

 In Benthalbella the first appearance of peritoneal pigment (not 

 in discrete section but uniformly in mesentary dorsal to gut from 

 between pectoral fin bases to behind pelvic fin bases) signals the 

 onset of the period of "rapid" transformation. 



Other larval pigment.— Jht larvae of Scopelarchoides and Ro- 

 senblattichthys are characterized by the presence of well-defined 

 pigment spots or areas (accessory pigment of Johnson. 1974b; 

 complementary pigment of Belyanina, 1982a) apparent in the 

 smallest (6- 1 2 mm SL) known larvae. The presence and location 

 of spots is uniquely diagnostic for each species possessing them. 

 Pigment spots are present in all larvae of Scopelarchoides and 

 Rosenblattichthys. absent in Benthalbella and Scopelarchus. In 

 Scopelarchoides the middorsal spot, if present, and the mid- 

 ventral spot are entirely behind the adipose base and anal fin 

 base respectively. In Rosenblattichthys the middorsal and mid- 

 ventral (where present) spots are entirely in advance of the bases 

 of these fins. 



Transformation pigmentation.— Johnson (1974b:20) distin- 

 guishes "dermal" vs "epidermal" pigmentation in scopelar- 

 chids. Dermal pigmentation refers to the major pigment stripes 

 present in some genera and species. These develop "early" dur- 

 ing transformation and persist in the adult. In most cases the 

 dermal pigment comes to be partially or completely overlain 

 by the epidermal pigmentation associated primarily with the 

 scale pockets. Dermal pigment is present in all 4 species of 

 Scopelarchus and in certain Scopelarchoides and Rosenblatt- 

 ichthys, it is absent in Benthalbella. The subequal pigment stripes 

 oC Scopelarchus (Fig. 127), situated above and below the lateral 

 line, are diagnostic for the genus. 



Gut morphology.— \n all scopelarchids the stomach is a heavily 

 muscularized, greatly elongate blind pouch. In small larvae the 

 stomach does not reach the pelvic fin base, but it expands pos- 

 teriad during transformation, very "rapidly" so in Benthalbella. 

 and in all adults extends to or nearly to a vertical through the 

 anus (which in all is closely-adjacent to the anal fin origin). 

 Johnson (1974b) and Wassersug and Johnson (1976) note that 

 the tremendous expansion of the stomach allows ingestion of 

 fairly large particles and hypothesize that the blind pouch ar- 

 rangement is a device for maximal recovery of food energy. 



Transformation. — Larvae of Benthalbella undergo rapid trans- 

 formation after a prolonged period of growth while retaining 

 larval form. The onset of transformation (size of smallest known 

 transforming specimen = 49.6 mm SL in B. dentata; 89. 1 mm 

 SL in B. elongata: 55. 1 mm SL in B. infans; 65. 1 mm SL in B. 

 macropinna; no transforming specimens of B. lingutdens are 

 known, but the largest known larva is 85.5 mm SL) is signalized 

 by appearance of a lens pad, appearance of peritoneal pigment, 

 and invasion of the abdominal body wall by musculature. Other 

 changes occurring during transformation include rapid elonga- 



tion of gut and stomach, "migration" of anus from just behind 

 pelvic fin base to just anterior to anal fin origin, appearance of 

 gonad, appearance of scales (especially lateral line scales), ap- 

 pearance of head and body pigmentation, reabsorption of ven- 

 tral adipose fin. great restriction of base of dorsal adipose fin, 

 ossification of vertebral column, change (from dorsally convex 

 to dorsally concave) in curvature in vertical plane of anterior 

 portion of vertebral column (Merrett et al., 1973; Johnson, 

 1974b). The result is a miniature adult at the end of a trans- 

 formation period covering as little as 1 mm of growth (Johnson, 

 1974b:68). In other scopelarchid genera these and other adult 

 characters are acquired essentially one by one over an increment 

 of growth ranging from 15 to 50 or more mm SL [in most 

 transformation occurs over an actual size (SL) range of 1 5 mm 

 to 40 or 50 mm]. Implications of changes in morphology during 

 transformation in terms of activity, buoyancy, feeding and other 

 aspects of biology are discussed for B. infans in Merrett et al. 

 (1973). 



Relationships 



The scopelarchids were poorly known until the completion 

 of Johnson's ( 1 974b) revision. Currently recognized are 1 7 species 

 grouped in 4 genera. Phylogenetic analysis involving hypothe- 

 sized derived states of 1 9 characters or character complexes 

 (Table 66) supports allocation of species among 3 of the 4 genera. 

 As will be shown, Scopelarchoides remains a problem. In the 

 listing that follows characters are given a character number (de- 

 rived state number). Documentation of character state catego- 

 rization and hypothesized polarity are given in references listed 

 in the key to Table 66. Of the 19 characters for which polarity 

 is indicated, 6 involve larval features (Table 65: 18, 19, 20, 22, 

 23, 24). Of 13 adult characters, 5 represented noval autapo- 

 morphies (Table 65: 1,4, 13, 14, 15), 3 occur in a sequence of 

 3 or more steps (Table 65: 5, 11, 16), and 5 represent reductive 

 characters (Table 65: 6, 7, 8, 9, 12). Rosenblattichthys is dis- 

 tinctive in having a greatly enlarged head in larvae 19 (19) and 

 precocious development of the pectoral fins 20 (20). A single 

 reductive character 8 (7) putati vely links the remaining 1 4 species 

 of scopelarchids. Scopelarchus is specialized in having subequal 

 dermal pigment stripes above and below the lateral line 4 (2), 

 unique support of the first epibranchial 16(17); unique confor- 

 mation of the three peritoneal pigment sections 22 (24), and in 

 three reductive characters 9 (8), 12(11), and 23 (25). Scopelar- 

 chus analis is linked with 5. michaelsarsi and 5. Stephens! by 

 one reductive character 11 (10). Scopelarchus stephensi and S. 

 michaelsarsi are linked by a reduced number of vertebrae 5 (3) 

 and by early onset and completion of metamorphosis 24 (26). 

 Benthalbella is specialized in having delayed but then extremely 

 "rapid" metamorphosis 24 (27) and in three reductive char- 

 acters 6 (5), 22 (21), and 23 (25). Linking Benthalbella dentata. 

 B. infans, B. lingutdens and B. elongata is the unique presence 

 of a hooklike process on the urohyal 15 (14) and two reductive 

 characters 9 (8) and 1 1 (9). 



In dealing with the 5 species included by Johnson (1974b) in 

 the genus Scopelarchoides the evidence available (Table 66, Fig. 

 1 28) suggests that this group is both unnatural and paraphyetic. 

 Linking 5. nicholsi, S. danae and Scopelarchus are unique se- 

 quential and fully correlated novel autapomorphies: support of 

 the first epibranchial character 16 (states 15 - 16 - 17), and 

 number and position of peritoneal pigment sections, character 

 22 (states 22 - 23 ^ 24). Further linking 5. nicholsi with S. 

 danae and Scopelarchus are relative size of the opercle and 



