NO. 3538 CHARACID FISHES — WEITZMAN 5 



It often blends with the darkly pigmented back. Tertiary stripe, 

 the lowermost stripe often extending from the lower jaw, across the 

 lower part of the operculum, below the base of the pectoral fin to the 

 origin of the anal fin. Additional stripes occur on some species, 

 such as Poecilobrycon eques. Live specimens suddenly illuminated 

 at night may show the stripes only faintly or almost not at all. During 

 the day these same stripes are darkly pigmented. 



The second category consists of oblique bands. The anterior of 

 these lies along the sides a short distance anterior to the dorsal fin, 

 while the posterior lies along the midside a short distance posterior 

 to the dorsal fin. These oblique bands are usually absent or extremely 

 pale in living specimens during the daylight hours; however, in the 

 absence of light the oblique bands become very dark. Females of 

 Nannostomus heckjordi while spawning often will show faintly the 

 oblique bands. The oblique bands appear in some species, such as 

 N. heckjordi, to be mostly areas of the primary horizontal stripe which 

 fan to become pale under the influence of darkness. However, even 

 in this species these bands are a little more than this because some 

 of the area of the obhque band occurs above the primary horizontal 

 stripe. In such species as Poecilobrycon eques, much of the area of 

 the oblique bands is above the primary horizontal stripe. 



The oblique bands have been called "night paint" by Hoedeman 

 (1950) because they are usually present only at night. Specimens 

 of N. heckjordi preserved at night in ten percent formalin retain their 

 "night pigment" pattern. In these specimens the oblique bands are 

 quite dark and their horizontal stripes are faded and sometimes 

 indistinct. 



In specimens preserved in daylight, oblique bands are present often 

 but are usually very pale. Horizontal stripes are almost always 

 present and distinct except on faded specimens or specimens pre- 

 served at night. Care should be used in determinuig the presence 

 or absence of oblique bands from preserved specimens because if, as 

 is usually the case, the specimens were preserved during daylight 

 hours, the pigment of the melanophores of the oblique bands may 

 be so contracted that the bands do not show. 



Permanent blotches constitute the third category. These are pres- 

 ent in only one species, Nannostomus espei, and differ in position and 

 quality from aU other dark markings seen in the other species. They 

 are permanent, not disappearing in daylight or darkness, although as 

 with other pigment, they may fade slightly at night. The borders 

 of the blotches are darker than the rest of the blotch. This is not 

 true of the obhque bands. There are five such permanent blotches 

 along the midsides on N. espei, the first above the pectoral fin, the 

 second below the origin of the dorsal fin, the third midway between 



