2Cg Ecology of the Trematode, Clinostomum marginatum, and Its Hosts in Eastern Kansas ERWIN E. KLAAS Introduction Much of the fishing in eastern Kansas is done in farm ponds and small reservoirs; occasionally, the State Biological Survey of Kansas re- ceives inquiries from fisherman about "wormy" fish, usually with refer- ence to farm ponds. The infections most often noted by anglers are metacercariae of Clinostomum marginatum (Rudolphi), a trematode (flatworm), commonly called the yellow grub. Although the parasite is harmless to man and there is little evidence that the yellow grub seriously affects the health of fishes, many fishermen discard infected fish because they are unattractive for human consumption. The life cycle of the yellow grub, as described by Hunter and Hunter (1934), is typical of trematodes for which fishes serve as inter- mediate hosts. A ciliated larva (miracidium) hatches from the egg in water, enters a snail of the genus Helisoma (first intermediate host) and, shedding its cilia, changes into a sporocyst. Rediae are produced parthen- ogenetically from germ cells within the sporocyst. Similarly, reproductive cells within the redia give rise either to larvae known as cercariae, or to daughter rediae which then produce cercariae. Cercariae leave the snail and, swimming by means of forked tails, come into contact with and penetrate fishes (second intermediate hosts). On entering the fish, cer- cariae shed their tails and secrete cysts, becoming metacercariae ("yellow grub" stage objectionable to anglers). These become adults on ingestion of the fish by the definitive host (a bird, usually a heron). Soon after reaching the stomach of the bird, the cysts surrounding the metacercariae are digested by enzymes in the stomach of the bird. The metacercariae migrate up the esophagus where the worms attach to the inner lining of the buccal cavity, upper esophagus, or trachea and become sexually mature adults in four to six hours. As the heron feeds, eggs are expelled into the water and the cycle is completed. In view of the possible significance of yellow grub infections in future fisheries management in Kansas, this investigation was undertaken to ascertain: (1) the extent of yellow grub infections in a series of farm ponds of unknown degree of infection, and (2) ecological factors asso- ciated with the occurrence and degree of infection in these ponds, and (3) Transactions of the Kansas Academy of Science, Vol. 66, No. 3, 1963. [519] 520 Transactions Kansas Academy of Science degree of infection according to nearness of ponds to a nesting colony of Great Blue Herons, Ardea herodias, the definitive host of the yellow grub. Methods and Materials STUDY OF HERONS The foraging movements of Great Blue Herons were studied in Douglas County, Kansas, from the summer of 1960 until the fall of 1961. Ponds, lakes, and streams were visited; also, the movements of herons of one nesting colony were observed for approximately 70 hours at various hours of the day in March, April, and May, 1961. The nesting colony is on an intermittent tributary of Washington Creek in Douglas County, Section 17, Township 14 South, Range 19 East. In February, 1961, 46 old nests were present, approximately 60 to 80 feet from the ground, in nine large sycamore trees. A blind was con- structed about 50 feet above the ground in one of the trees, in the hope that nesting birds could be marked with dyes by means of a spray-gun operated at the blind. However, use of the blind so disturbed the herons that all nests in the blind-tree were deserted in the second week of incu- bation. Other observations were made from a hill about one-quarter mile from the heron colony, and from the top of a large silo about one- half mile away. From these vantage-points herons could be seen leaving and approaching the colony for a radius of about one mile. Ten herons were killed and examined for adult yellow grubs. All of the flukes that were found in the herons were fixed in 10 per cent formalin or alcohol-formol-acetic fixative in the field. The flukes were later stained with Semichon's carmine or Harris's hematoxylin and mounted on slides with Canada balsam. NUMBER AND DESCRIPTION OF PONDS SAMPLED Hastings and Cross (1962) reported the number of ponds. their distribution and general physical characteristics, and the predominant kinds of fish in Douglas County, Kansas, in 1954. They found in 1316 farm ponds of which 89.5 per cent were one-half acre or less in size. The largest of the ponds that I seined was about one and one-half acres, but most ponds were between one-tenth and one-fourth acre in size, and agreed with descriptions given by Hastings and Cross. All but eight of the ponds were used by livestock for wading. The average depth was about four feet and soft bottom-mud averaged 6 to 8 inches deep. Watersheds consisted mainly of permanent pasture, but all ponds received some drainage from cultivated fields. Samples of fish and snails were obtained from ponds in two tran- sects, each about one mile wide and ten miles long; one extended north Ecology of Trematode and its Hosts in Kansas 521 from the heron colony and the other east. Ponds in these transects were selected from aerial photographs that were taken in 1954, a period of severe drought. Therefore, it is reasonably certain that the ponds investi- gated are permanent, and all are several years old. Insofar as possible, samples were obtained from at least one pond in each section of each ten- mile transect. The ponds east of the colony will be referred to as Series E; the ponds north of the colony will be referred to as Series N. The ponds were numbered according to their relative distances from the heron colony as shown in Figure 1. All of the ponds are listed below with KANSAS RIVER 100 97 0N-16 39 39 • N—I5 0 N—I4 38 38 O N—I3 • N—I2 g N—I 1 100 97 N—I0 ON-9 0 N-8 T. WAKARUSA RIVER 13 O N-7 /N-6 o0N-5 • N-4 MILES 0 1 2 o N-3 O N-2 T. o N—I 13 E-5 E-6 E-- I I E—I E_ 3 / E-7 o • • • - o 0E—I4 HERON / 0 E* 8 °0E-13 - 0 COLONY 0E-4 0 OE-10 E 150 •- E-2 —E-9 E—I2 E— IL R.I9 E R.20 E Figure 1. Localities of Ponds Seined in Relation to Location of Heron Colony. Solid Circles indicate ponds having infected fish. Ponds N-3, N-5, N-8, and N-14 did not have fish. Small dot on inset map of Kansas indicates general location of the study area. 522 Transactions Kansas Academy of Science the localities, surface areas, dates of seining, and the names of the landowners. SERIES E. E-1; Sec. 16, T. 14 S, R. 19 E; 1/4-acre; Aug. 1, 1960, Aug. 4, 1961; F. Deay. E-2; Sec. 21, T. 14 S, R. 19 E; 1/2-acre; Aug. 1, 1960, Aug. 1, 1961; E. L. Russell. E-3; Sec. 15, T. 14 S, R. 19 E; 1/4-acre; Aug. 2, 1960, Aug. 4, 1961; J. S. Beeghley. E-4; Sec. 15, T. 14 1 S, R. 19 E; /3-acre; Aug. 2, 1960, Aug. 4, 1961; D. F. Beeghly. E-5; 1 Sec. 15, T. 14 S, R. 19 E; /3-acre; Aug. 3, 1960, Aug. 1, 1961; R. L. Markeley. E-6; Sec. 14, T. 14 S, R. 19 E; 1/4-acre; Aug. 3, 1960, Aug. 17, 1961; P. R. Ulrich. E-7; Sec. 14, T. 14 S, R. 19 E; 1/4-acre; Aug. 2, 1960, Aug. 17, 1961; P. R. Ulrich. E-8; Sec. 13, T. 14 S, R. 19 E; 1/4-acre; Aug. 4, 1960, Aug. 1, 1961; R. P. Harrison. E-9; Sec. 13, T. 14 S, R. 19 E; 11/2-acres; Aug. 4, 1960, Aug. 1, 1961; R. P. Harrison. E-10; Sec. 18, T. 14 S, R. 20 E; 1/10-acre; Aug. 3, 1960; D. A. Wray. E-//; Sec. 16, T. 14 S, R. 20 E; 1/10-acre; Aug. 3, 1961; R. Hoskinson. E-12; Sec. 16, T. 14 S, R. 20 E; 1/4-acre; Aug. 3, 1960, Aug. 3, 1961; G. Hoskinson. E-13; Sec. 16, T. 14 S, R. 20 E; 1/4-acre; Aug. 3, 1960, Aug. 3, 1961; G. Hoskinson. E-14; Sec. 14, T. 14 S, R. 20 E; 1/10-acre; Aug. 5, 1960; W. E. Hoskinson. E-15; Sec. 13, T. 14 S, R. 20 E; 1/10- acre; Aug. 4, 1960, Aug. 3, 1961; E. F. Johnson. E-16; Sec. 13, T. 14 S, R. 20 E; 1/2-acre; Aug. 4, 1960, Aug. 3, 1961; R. 0. Johnson. SERIES N. N-1; Sec. 8, T. 14 S, R. 19 E; 1/10-acre; Aug. 8, 1960; D. Cleff. N-2; Sec. 5, T. 14 S, R. 19 E; 1/4-acre; Aug. 8, 1960. Aug. 18, 1961; R. Williams. N-3; Sec. 32, T. 13 S, R. 19 E; 1/4-acre; Aug. 8, 1960; H. Schellhorn. N-4; Sec. 29, T 13 S, R. 19 E; 1/2-acre; Aug. 8, 1960, Aug. 18, 1961; W. Thome. N-5; Sec. 29, T. 13 S, R. 19 E; 1/2-acre; Aug. 10, 1960; L. W. McNess. N-6; Sec. 29, T. 13 S, R.