designed to quantitatively collect invertebrates. 



Large, adult M. liigubns from Columbia River 

 fish were characterized by a green background 

 coloration, superficially suggesting that they fed 

 on algal cells ingested by the host. Chiselmouth 

 and suckers commonly feed on sessile, green- 

 colored diatoms from bottom substrates. However, 

 microscopic examination revealed that this col- 

 oration was due entirely to pigments in the adult 

 leech's musculature and not to the presence of 

 algae in their digestive tract. Myzobdella lugubris 

 fed entirely on fish blood cells and plasma. 



Feeding on fish blood is clearly required by M. 

 lugubris for growth and reproduction. Copulating 

 M. lugubris were noted on fish. But since deposi- 

 tion of a cocoon requires hard substrates, sexually 

 mature leeches must eventually detach, thus free- 

 ing fish of infestations. The breeding, growth, and 

 reproductive cycle of piscivorous leeches may ac- 

 count for the periodic infestations of fish so fre- 

 quently documented in the literature. 



In the Columbia River, the cycle in M. lugubris 

 is correlated with a seasonal change in water 

 temperatures, with peak activity occurring in late 

 summer and fall. 



In tidal estuaries on the east coast of the United 

 States, M. lugubris has a life cycle that involves 

 tw^o hosts, a fish and a crustacean. It engorges on 

 fish blood before detaching to deposit cocoons on 

 crabs (Daniels and Sawyer 1975). This indicates 

 possible involvement of a freshwater crustacean 

 in the life cycle of M. lugubris in the Columbia 

 River. The only large crustacean available is 

 Pacifasticus leniusculus, but extensive collections 

 of this crawfish in previous years by the senior 

 author disclosed no attached leeches. Therefore, 

 stones are probably used as cocoon deposition sites 

 in the Columbia River. 



Piscivorous leeches are often vectors of 

 hemoflagellates (genera Trypanoplasma and 

 Trypanosoma) found in the blood of freshwater 

 and marine fishes iKhaibulaev 1970; Becker 

 1977). Although we have occasionally detected 

 Trypanoplasma in Columbia River fish, we found 

 no hemoflagellates in the digestive tract of over 20 

 M. lugubris taken from various hosts. 



We did not examine histopathology of leech at- 

 tachment and feeding sites in the oral cavity of 

 infested Columbia River fish, although petechiae 

 were evident during the fall on some chiselmouth. 

 Inflammatory conditions and hyperplasia were 

 described previously from a massive infestation of 

 M. lugubris (misidentified as Cystobranchus vir- 



ginicus) on white catfish in Virginia (Paperna and 

 Zwerner 1974). 



Piscicola salmositica 



The salmonid leech, P. salmositica, was de- 

 scribed from specimens taken, in part, from sea- 

 run steelhead trout, Sal mo gairdneri, transferred 

 from the Columbia River to Mason Creek, Chelan 

 County, Wash. (Meyer 1946a). The leeches infest- 

 ing the fish originated either in the Columbia 

 River or from Mason Creek. Thus the salmonid 

 leech has previously been recorded from the upper 

 Columbia River system. This species is usually 

 associated with fall spawning runs of adult salmo- 

 nid fishes in coastal streams, but it occurs 

 elsewhere in the Pacific Northwest (Becker and 

 Katz 1965a). 



We collected several P. salmositica at various 

 times from chinook salmon, Oncorhynchus 

 tshawytscha , fry and once from a fingerling 

 sucker. Each infestation consisted of a solitary 

 leech attached to the dorsal surface of its host and 

 feeding on blood. All specimens were taken in 

 April and June as water temperatures (10°-14°C) 

 increased and consisted of small leeches that pre- 

 sumably had hatched from cocoons the previous 

 fall or winter. Three specimens contained develop- 

 ing trypanoplasms among their intestinal con- 

 tents, evidence of prior feeding on infected fish. 

 Therefore, P. salmositica is confirmed as a vector 

 transmitting trypanoplasms among various fish 

 in the central Columbia River. The salmonid leech 

 is the only known vector of the piscine hemoflagel- 

 lateTrypanoplasma salmositica (Katz 1951) in the 

 Pacific Northwest (Becker and Katz 1965b). 



Piscicola salmositica requires meals of fish blood 

 before detaching to deposit cocoons on bottom sub- 

 strates (Becker and Katz 1965a). Thus salmonid 

 leeches presumably occur among and infest popu- 

 lations of anadromous chinook salmon that spawn 

 each fall in the central Columbia River near our 

 fish collection sites. However, we have not de- 

 tected P. salmositica on transient adult fall 

 chinook salmon returning from the sea to spawn or 

 from downstream drifting, spawned out salmon 

 carcasses. Neither have we found salmonid 

 leeches on several adult steelhead trout and 

 spring-run chinook salmon examined during the 

 summer at the Ringold Hatchery (Washington 

 State Department of Game) above Richland. On 

 the basis of our observations, P. salmositica is not 

 an abundant leech in the central Columbia River. 



929 



