Darter Spawning Behavior 139 



female moved about, a male followed closely and drove away approach- 

 ing males. Agonistic encounters between males usually consisted of the 

 larger male swimming at, or making a quick dash at, the smaller male. 

 Two males about the same size sometimes engaged in lateral displays 

 (with median fins held erect). Females accepted any male, and if a 

 male previously courting her was chasing away an intruding male, the 

 female sometimes spawned with a third male. 



When a female selected a spawning site, she aligned her body over 

 it and the male mounted. Both vibrated with their bodies in an S-shaped 

 figure and their genital papillae pressed against or near the rock (Fig. 

 IB). Etheostoma duryi appeared to vibrate less intensely than E. 

 simoterum; however, verification of this will require cinematographic 

 analysis. 



Etheostoma (Vaillantia) chlorosomum. — Winn (1958), para- 

 phrasing C. Hubbs, stated that in Texas E. chlorosomum lays its eggs 

 on plants or plant debris, but gave no other details. Three breeding male 

 and three ripe female E. chlorosomum, 40 to 50 mm SL, were captured 

 in East Fork Kaskaskia River, Marion County, Illinois, on 30 April 

 1981 in a sand-bottom pool at 22° C and a maximum depth of 80 cm. 

 At one end of the pool was a large accumulation of logs and other plant 

 debris. East Fork is a fairly slow stream composed mostly of long pools 

 but with some gravel-bottom riffles. 



The E. chlorosomum were transferred at 0900 hr the following day 

 to a 40 1 aquarium (23° C) at the Illinois Natural History Survey 

 (INHS). One half of the aquarium bottom was covered with sand, the 

 other half with gravel. In one corner a large stone was propped on a 

 smaller stone so that its underside was accessible for egg-clustering or 

 clumping, and its top and sides were available for egg-attachment. A 

 small log (5 cm diameter) was placed across the aquarium, over the sand 

 and gravel, for attachment of eggs. An accumulation of filamentous 

 algae, dead leaves, and twigs was provided at the end of the log over 

 sand. 



Little activity ensued until 1 145 hr when the darters were fed live 

 cladocerans. After feeding, the males became aggressive towards one 

 another and courted the females. Both aggressive and courting behavior 

 consisted mainly of lateral displays. Usually when displaying, the males 

 were swimming and quivering about 1 cm above the substrate. All such 

 activities occurred over the sand-covered half of the aquarium. 



At 1230 hr, one male succeeded in chasing the other two out of the 

 sand-covered part of the aquarium and sequentially enticed all three 

 females to spawn. Spawning continued until 1700 hr when observations 

 were discontinued. As in other egg-attaching darters, the female selected 

 the site of egg-deposition, the male closely followed her to the site and 

 mounted her, the pair vibrated, and eggs and sperm were released. 

 Often the male mounted a female while she remained horizontal on the 

 substrate and beat her with his pectoral fins until she swam into the 

 plant material. Usually 1 to 3 eggs (1 mm diameter) were laid at a time, 



