FISHERY BULLETIN VOL 77. NO, H 



larger forms, Scomheresux and Cololabis (Figure 

 10. items 1, 41, have a much greater number and 

 complexity of pores and canals on the side and 

 particularly on the top of the head, than do adults 

 of the dwarfed forms, Nanichthys and Elan- 

 sichthys (Figure 10, items 3, 6). Also juveniles of 

 the larger forms (Figure 10, items 2, 5) show a 

 greater pore-canal development than do the adult 

 dwarfs, although they are of virtually identical 

 size. This reduction of pores and canals in the 

 dwarfs may be interpreted as an arrested state of 

 development, perhaps neotenic or paedomorphic 

 in character, as very small (20-24 mm SL) speci- 

 mens of the larger forms bear a pore-canal struc- 

 ture similar to those of the adult dwarfs (Figure 

 10, items 3, 6); or, it may be that neither numbers 

 nor complexity of pores is necessary at such small 

 sizes and (perhaps) less active habits. 



Lopez (1957i provided the first figure of the 

 pores and canals of the head of an adult (size not 

 stated) Scornheresox sauriis ( = S. s. scomhroides) 

 from near Nechochea, Argentina. Our specimen, 

 from the Peru-Chile area, bears a much greater 

 profusion ol pores and complexity of canals, par- 

 ticularly dorsally. than shown by Lopez. 



Collette (1966) illustrated interorbital canals 

 and pores of four species of belonid fishes. These 

 canals, rather simple and unbranched, which he 

 reported to be representative of the Belonidae, are 

 basically like those of Elatisichthys and Nanich- 

 thys, although those of the latter show slight 

 branching (Figure 10, item 3). Collette (his figure 

 7D) figured a complete joining of the left and right 

 canals dorsally on Behmion dihranchodon , with 

 both median and lateral pores present. He re- 

 ported this condition to be unlike that of any other 

 synentognath. Despite the profusion of pores and 

 canals atop the heads of Scomberesox and CdI- 

 olahis (Figure 10. items 1. 4), no joining of the left 

 and right canals is apparent, although some ca- 

 nals very closely approach the median line. 



Lateral Line Scales 



The lateral line scales of Scomberesox and Col- 

 olabis are basically similar, but those of the 

 dwarfed Nanichthys differ notably, both in shape 

 and in numbers and development of circuli ( Figure 

 llA-C). We have found no trace of lateral line 

 scales in Elassichthys. All scales were removed 

 from within 1 cm anterior to the pelvic fin. The 

 basic similarity in the scales of the three genera 

 involves the secondary tube on each scale that 



leads posteroventrally from the main tube and 

 opens to the external surface of the scale. The 

 primary (main) tube of each scale, in contrast, 

 overlies the lateral line canal which extends along 

 the body. 



The lateral line scale of the adult Scomberesox 

 (270 mm BL (body length); Figure llA) lacks cir- 

 culi, but they are present, though very weakly 

 developed, on fish about 200 mm BL. Development 

 of circuli appears to decrease as the fish grows; the 

 circuli on scales on a 100 mm fish are notably 

 better defined than on the 200 mm specimen. 

 These early developed circuli occur in areas rather 

 similar to those that are better developed in Col- 

 olabis. A principal feature distinguishing the 

 Scomberesox scale from that of Cololabis is a 

 well-developed baselike structure on the ventral 

 aspect of the scale (Figure IIC). As the Scom- 

 beresox scale is much more tenacious than that of 

 Cololabis, perhaps this structure serves as an an- 

 chor to the body. Another difference between the 

 scales of Scomberesox and Cololabis is a narrow 

 median band of tissue at about the center of the 

 scale (and main tube) that does not absorb the 

 weak solution of alizarin red S stain. When remov- 

 ing it, the highly tenacious scale usually breaks at 

 this band. The Scomberesox scale figured is about 

 0.9 mm thick at the main tube. 



The lateral line scale of the adult of Cololabis 

 (262 mm BL; Figure IIB), in addition to differing 

 in form from that of Scomfeeresojc, differs in having 

 at least weakly formed circuli on the anterodorsal 

 and anteroventral aspects (these circuli do not 

 show clearly, probably due to a slight canting of 

 the scale during mounting and to the extremely 

 short depth of focal field inherent in photomicros- 

 copy). The scale has a thicknessatthe main tube of 

 about 0.4 mm. The circuli are better developed on 

 smaller fish and extend farther posteriad along 

 both the ventral and dorsal aspects of the scale in 

 about the same areas as in the adult scale. Some, 

 but notall, lateral line scales of adults of Co/o/a/);.s 

 bear the nonstaining band of tissue found in 

 Scomberesox, but it is much less strongly de- 

 veloped. 



The lateral line scale of Nanichthys (106 mm 

 BL; Figure IIC, from the 121.2 mm Funchal "gi- 

 ant") differs notably from that of its two larger 

 relatives. The shape is quite different and the cir- 

 culi are much more numerous and more strongly 

 developed and extend over most of the scale, being 

 absent only on the central portion of the basal 

 (exposed) area. The thickness of the scale at the 



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