FISHERY BULLETIN VOL 



noted below in the general description of the ovary 

 in the two dwarf species). 



In life Nanichthys is silvery ventrally and later- 

 ally, becoming greenish with brown specks dor- 

 sally; this is also the basic coloration of the other 

 three genera. In preserved specimens the anal fin 

 is essentially colorless, but the dorsal, pectoral, 

 and caudal fins bear microscopic spots of dark 

 pigment along the edges of the outer rays. The 

 caudal fin. in addition, is pigmented in the 

 crotches of the first branching of the rays and 

 sometimes in the second branching of both dwarf 

 species (the resulting streaking shows in Figures 

 5, 8, 9). In preserved specimens of this (and of 

 other) scomberesocid species, a dusky underlying 

 streak parallels the dorsal margin of the body 

 (evident in Figure 5). Elassichthys adocetus has 

 basically the same coloration. 



JUSTIFICATION OF 

 GENERIC SEPARATION 



In recognizing a separate genus for each of the 

 four species of Scomberesocidae we are cognizant 

 of the circumstance that we are in a period when 

 lumping is prevalent. We hold, however, that the 

 grounds for the recognition of the four genera ai"e 

 compelling, and consistent with other generic rec- 

 ognitions on similar grounds. The distinctive fea- 

 tures stand out sharply in the generic comparisons 

 (Table 1). 



The complete lack vs. strong development of the 

 gas gladder and the single vs. paired ovaries, 

 supplemented by a series of minor characters, 

 primarily the striking differences in body muscu- 

 lature (Figure 7), and bolstered by the vast differ- 

 ence in body size, seem to provide fully adequate 

 grounds for distinguishing both Elassichthys and 

 Nanichthys from either Colo! abis or Scomberesox. 



The sagittal sections of the four genera of scom- 

 beresocid fishes (Figure 7A-D). taken from close 

 behind the bases of the pelvic fins, portray these 

 striking differences. The 59 mm SL adult oi Elas- 

 sichthys and 60 mm SL adult ofNanichthys clearly 

 show the lack of the gas bladder; also, there is no 

 evidence of even a weak septum that might indi- 

 cate a paired condition of the ovaries. Even in the 

 young of Cololabis (59.4 mm SL) and of Scom- 

 beresox (59.7 mm SL) the roughly triangular ga^ 

 bladder is plainly evident just above the liver and 

 gut; these young specimens are too immature ti, 

 have recognizable gonads. 



Also evident and notable is a difference in thi 



arrangement of the myotomes; those of the young 

 Cololabis and Scomberesox (and of adults) are 

 separated by distinct septa. However, in the adults 

 of the dwarf forms the myotomes are much more 

 massive and the dividing septa are greatly re- 

 duced in number in Nanichthys (virtually non- 

 existent in Elassichthys). Perhaps this reduction 

 is a reflection of the weak-swimming, surface- 

 pelagic habits of these small fishes. 



The development of filaments of a peculiar 

 well-formed type on the egg of Cololabis strength- 

 ens the basis for the separation of that genus from 

 Scomberesox, with unfilamented eggs. The large 

 literature on Cololabis and its great commercial 

 importance are additional incentives for retaining 

 the familiar and well-established nomenclature; 

 Scomberesox now approximates qualification in 

 both categories. 



The generic separation of the two dwarf forms 

 also seems to be well justified. The feature of the 

 well-developed beak in Nanichthys vs. its lack in 

 Elassichthys (Figure 2 1 calls for generic separa- 

 tion, as it does for retaining Cololabis distinct 

 from Scomberesox. The apparent total lack of an 

 external lateral line in Elassichthys and its con- 

 siderable development in Nanichthys provides 

 sustaining evidence. Furthermore, the high prob- 

 ability that Nanichthys and Elassichthys are of 

 separate origin (Figure 3), owing their resem- 

 blances to convergent evolution, seems to us 

 clinching reason for generic separation. 



Description of Gonads 



The one ovary and the two testes o( Nanichthys 

 are essentially like those of Elassichthys (Figures 

 8, 9). Instead of being pendant from the dorsolat- 

 eral walls of the coelom, they form, as they de- 

 velop, a coherent median mass, occupying, with 

 maturity, a very large proportion of the coelom 

 from the middorsal line to the ventrally displaced 

 liver, intestine, and other visceral organs. In the 

 specimen figured for this discussion, the length of 

 the ovary composes 38^^ of the standard length of 

 the fish; the greatest depth of the ovary 20% of its 

 length; and its greatest width 60% of its greatest 

 depth. 



The development of a single functional ovary in 

 "Scomber-esox sp" |= Nanichthys simulans\ has 

 been noted by Dudnik ( 1975b), who, however, 

 mentioned that "the second lovaryl is rudimen- 

 tary and can barely be discerned" |a translation!. 

 We. however, have found not even a rudimentary 



542 



