THE LIFE HISTORY OF THE SLENDERHEAD 
DARTER, PERCINA PHOXOCEPHALA, 
IN THE EMBARRAS RIVER, ILLINOIS 
THE SLENDERHEAD DARTER, Percina phoxo- 
cephala (Nelson), is the most widely distributed and 
best known of the four species assigned to the subgenus 
Swainia, which also includes P. squamata (Gilbert & 
Swain 1887), a species with a small range centered in 
eastern Tennessee; P. oxyrhyncha (Hubbs & Raney 
1939), limited to West Virginia and Virgina; and P. 
nasuta (Bailey 1941), occurring in northern Arkansas, 
eastern Oklahoma, and southern Missouri. 
Despite many references to the occurrence, relative 
abundance, and habitat preferences of P. phoxocephala, 
details of its life history are limited to observations made 
in Iowa by Karr (1963) and in IlIlinois by Thomas 
(1970). No published information is available on the 
life histories of the other species of Swainia. Because 
of the paucity of life-history data and the availability of 
a large population of P. phoxocephala in the middle 
Embarras River, a detailed study of the life history of 
this darter was commenced in August 1967 in conjunc- 
tion with a similar study of the dusky darter, P. sciera. 
References to P. sciera in the following text are based on 
the latter investigation (Page & Smith 1970). 
The slenderhead darter was described by Edward 
W. Nelson (1876:35) as Etheostoma phoxocephalum 
rom “the Illinois [River] and its tributaries.” The 
pecies (cover illustration) is a medium-sized darter, 
exually mature individuals ranging from 40 to 80 mm 
n standard length, with a slender body and an attenu- 
ited snout. Its scales are small, the lateral-line count 
anging from 60 to 80 scales. Opercles and nape are 
caled:; cheek Squamation is variable. The breast of the 
emale is naked, except for one or two enlarged, strongly 
tenoid scales. The posterior half of the male’s breast 
s scaled; the anterior half is naked. Dorsal spines num- 
er 11 or 12, soft dorsal rays 11—14. The anal fin has 
Wo spines and eight or nine soft rays. ‘The gill covers 
re moderately conjoined. 
The dorsum is light brown or straw color with darker 
town vermiculations and blotches. The venter is white. 
long each side of the body is a row of 10—16 rather 
bscure, more or less confluent, dark blotches. There 
i 
This paper is published by authority of the State of Illinois, IRS 
1. 127, Par. 58.12, and is a contribution from the Section of Faunistic 
irveys and Insect Identification of the Mlinois Natural History Survey. 
r. Page is a research assistant at the Natural History Survey; Dr. 
nith is Head of the Section of Faunistic Surveys and Insect Identi- 
— at the Survey and Professor of Zoology at the University of 
inois. 
Lawrence M. Page and Philip W. Smith 
is a small, discrete, black caudal spot and a dark stripe 
extending from the tip of the snout backward through 
the eye. Usually there is no suborbital bar. The best 
field character is the submarginal band of bright orange 
in the spinous dorsal fin. 
The male can be distinguished from the female at all 
seasons and all sizes above 25 mm standard length by a 
median row of enlarged specialized scales extending 
from the midpelvic area to the anus. During late spring 
and early summer the male has closely spaced melano- 
phores over the breast and belly and on the ventral fins: 
the female is white below and has only a few scattered 
melanophores on the anal fin. The spinous dorsal fin 
of the male is more heavily pigmented than is that of 
the female, the basal portion being quite dark. For a 
few weeks prior to spawning the female can be recognized 
by its distinctly enlarged genital papilla; the genital pa- 
pilla of the male is a small triangular flap. 
The small young of the species can be readily dis- 
tinguished from other young darters in the Mississippi 
River valley by the combination of a slender habitus, 
attenuate snout, and the characteristic dorsal spotting. 
P. phoxocephala occurs from western Pennsylvania 
to northeastern South Dakota—although it is for the 
most part absent from the Great Lakes drainage—and 
southward to northern Alabama and southern Oklahoma 
(Fig. 1). The species is not found in the lower Mississip- 
pi River valley and rarely occurs in low-gradient, low- 
land streams anywhere within its range. In Illinois it 
is widely distributed and generally common, except in 
the northeastern and extreme southern parts of the state. 
We are much indebted to Raymond T. Schaaf, Mrs. 
Dorothy M. Smith, Norman D. Penny, Hartley F. Hutch- 
ins, Robert O. Watson, Miss C. Catherine Huheey, and 
the late Robert L. Hass for aid in collecting specimens; to 
our entomologist colleagues Donald W. Webb and Drs. 
John D. Unzicker and Milton W. Sanderson for their 
help in identifying arthropod remains in darter stomachs; 
to Dr. Marvin C. Meyer of the University of Maine for 
identifying the leech parasite found on our P. phoxo- 
cephala specimens; to Harman F. Smith, Illinois State 
Water Survey, for providing data on the water chemistry 
of the Embarras River: and to our associate rae Re. 
Weldon Larimore for counsel on various matters. We 
also thank Chief Fishery Biologist A. C. Lopinot of the 
Hlinois Department of Conservation and his staff of 
COVER ILLUSTRATION: Adult female Percina phoxocephala collected in May in the Embarras River, 
umberland County, Illinois. From a drawing by Mrs. Alice Ann Prickett. 
