8 



(1935:47) noted that the breeding season in Illinois 

 is late March and April. Collette (1962:144) surmised 

 that in Texas spawning occurs in mid-March. Our 

 data, which indicate a considerably later spawning time, 

 are based on darters at the northern periphery of the 

 species' range and on observations made only in 1964. 

 Apparently the spawning season is quite short, last- 

 ing only 1 or 2 days. Thus, there is little size variation 

 in the hatchlings up to 1 week old at a given site. 



HATCHING AND DEVELOPMENT 



The egg, reported by Hubbs & Cannon (1935:47) 

 as 1.0 mm in diameter, measured about 0.85 mm in 

 diameter in the Dismal Creek population. Each egg 

 was spherical, except for the place of attachment, a 

 somewhat flattened, opaque disk. 



Each egg was clear except for the yellow oil droplet. 

 Eggs deposited either the night of May 24 or the early 

 morning of the 25th showed unpigmented somites by 

 the evening of the 25th and were entirely clear, except 

 for a now-amber oil droplet. By 9 a.m. on the morn- 



ing of May 26 the large eye and pulsing heart were 

 clearly visible, and the somites had enlarged to fill most 

 of the egg. Three or four large stellate pigment cells 

 were present on the head and fore body, and the oil 

 droplet was proportionately smaller. A few hours later 

 the entire clutch of eggs was lost to mold. 



Hatching time in the laboraton,- for another set of 

 eggs was 5 days at 73° F, the temperature of the stream 

 at that time. The larvae looked like the lar\a in Fig. 6 

 and were 2.8 mm in total length. Development is thus 

 more rapid in E. gracile than in other species of darters 

 studied. Winn (1958:182) reported a hatchinsr time 

 of 5.5—8.0 days in E. nigrum and longer periods for 12 

 other species. Fahy (1954:185—186) found a hatching 

 time of 18 days for E. blennioides. Hatching time ob- 

 viously varies with the species and water temperature. 



Although hatchlings approximately 3 mm in total 

 length were first noted in the laboratory on June 4, 

 two juveniles collected in Dismal Creek on May 22 

 had already attained standard lengths of 14 and 16 mm 

 (Table 2). On June 11 only two juveniles, measuring 



Table 2. — Standard length frequencies of Dismal Creek Etheostoma gracile collected and preser\ed February 14-December 12, 1964. 



♦ Sample consisting: of two adults and two hatchlings from :i pool several miles upstream from study area, 

 t Total length of a laboratory-hatched specimen approximately 4 hours old. 



