Parasites of Hardhead (Mylopharodon Conocephalus) And

PARASITES OF HARDHEAD (MYLOPHARODON CONOCEPHALUS) AND

SACRAMENTO PIKEMINNOW (PTYCHOCHEILUS GRANDIS) FROM THE NORTH

FORK FEATHER RIVER, PLUMAS AND BUTTE COUNTIES, CALIFORNIA

Dawn E. Alvarez

A Thesis

Presented to

The Faculty of Humboldt State University

In Partial Fulfillment

Of the Requirements for the Degree

Masters of Science

In Natural Resources: Fisheries

December, 2008

ABSTRACT

Parasites of hardhead (Mylopharodon conocephalus) and Sacramento pikeminnow (Ptychocheilus grandis) from the North Fork Feather River in Plumas and Butte Counties, California

Dawn E. Alvarez

Hardhead (Mylopharodon conocephalus) and Sacramento pikeminnow

(Ptychocheilus grandis) are endemic to California and are native to the

Sacramento-San Joaquin system, Russian River, and Napa River. Very little study has been done on parasites of these two species. The objective of this study was to describe the parasites of hardhead and Sacramento pikeminnow in the North Fork Feather River in Plumas and Butte Counties, between its confluence with the East Branch of the North Fork Feather and Lake Oroville.

Thirty-two hardhead and 14 Sacramento pikeminnow were examined for parasites. All Sacramento pikeminnow were infected, and all but one hardhead were infected. On average, Sacramento pikeminnow were infected with four parasites, and hardhead were infected with three parasites. I found six new host records for hardhead and four new host records for Sacramento pikeminnow. I found Trichodina/Paratrichodina species in Sacramento pikeminnow and two

Myxobolus species in hardhead and Sacramento pikeminnow. Dactylogyrus californiensis and one unidentified monogenetic trematode were found on hardhead. I found Neascus of Ornithodiplostomum ptychocheilus in both hardhead and Sacramento pikeminnow. I found Edlintonia ptychocheila and

Neoechinorhynchus rutili in hardhead. In addition, I found one parasite which

iii has been previously recorded in hardhead and Sacramento pikeminnow,

Lernaea cyprinacea. I also found three types of parasites which have been previously recorded in hardhead and Sacramento pikeminnow. “Black spot”

Neascus species and unidentified larval nematodes were found in both hardhead and Sacramento pikeminnow, and unidentified proteocephalan plerocercoids were found in Sacramento pikeminnow.

ACKNOWLEDGEMENTS

Funding for this study was provided in part by United States Forest

Service Hispanic Recruitment Initiative Student Career Experience Program,

Plumas National Forest Student Career Experience Program, and Golden West

Women Flyfishers. I would like to thank Kelly Child, Michael Condon, Dennis

“Mitch” Reasoner, Eric Wonhof, Dennis Matsunaga, Willie Ryan, and Dale Marsh for their help with field work. I wish to extend special thanks to Diane Wong for helping several weekends with field work, Terri Simon-Jackson for serving as a mentor and a guide to the process, and S.D. Alvarez who accompanied me on every trip to the field. Greg Miller is gratefully acknowledged for all his support and for his help formatting the paper. Special thanks to Richard and Mary

Alvarez and the rest of my family without whose support this paper would not have been possible. Finally I wish to thank my advisor, Dr. Gary Hendrickson, and my committee, Drs. Peggy Wilzbach and Andrew Kinziger, for all their help with my project and this paper.

TABLE OF CONTENTS

Page

ABSTRACT...... …...... iii

ACKNOWLEDGEMENTS...... v

LIST OF TABLES...... viii

LIST OF FIGURES...... ix

INTRODUCTION...... 1

STUDY AREA...... 6

MATERIALS AND METHODS...... 10

RESULTS...... 15

Trichodina/Paratrichodina species...... 18

Myxobolus species...... 20

Dactylogyrus californiensis...... 27

Unidentified monogenetic trematode...... 30

Unidentified Neascus...... 30

Neascus of Ornithodiplostomum ptychocheilus...... 33

Edlintonia ptychocheila...... 39

Proteocephalan plerocercoids...... 41

Unidentified larval nematode...... 41

Neoechinorhynchus rutili...... 44

Lernaea cyprinacea......

DISCUSSION...... 56

TABLE OF CONTENTS (CONTINUED)

LITERATURE CITED...... 65

vii

LIST OF TABLES

Table Page

1 Prevalence, mean intensity, and locations of parasites found in 32 hardhead collected from the North Fork Feather River in Butte and Plumas Counties, California, from November 2005 to November 2007...... 16

2 Prevalence, mean intensity, and locations of parasites found in 14 Sacramento pikeminnow collected from the North Fork Feather River in Butte and Plumas Counties, California, from November 2005 to November 2007...... 17

3 Proboscis and hook measurements in micrometers between Neoechinorhynchus from hardhead collected from the North Fork of the Feather River (Butte and Plumas Counties, CA) and N. rutili and N. salmonis (measurements from Arai 1989)...... 51

viii

LIST OF FIGURES

Figure Page

1 Map of study area in North Fork Feather River drainage in Plumas and Butte Counties, California...…………………...... 7

2 Trichodina/Paratrichodina species from wet mount of gills from Sacramento pikeminnow collected from the North Fork Feather River, Plumas County, California, October 2007...... 19

3 Myxobolus species 1 spore from wet mount of spleen of hardhead collected from North Fork Feather River, Plumas County, California, September 2007...... 21

4 Myxobolus species 1 mature spore in kidney histological section from hardhead collected from North Fork Feather River, Plumas County, California, September 2007. Section was stained with hemotoxylin and counterstained with eosin...... 22

5 Group of Myxobolus species 1 spores in melanomacrophage center in wet mount of spleen of hardhead collected from North Fork Feather River, Plumas County, California, October 2008...... 23

6 Myxobolus species 2 spores in wet mount of gills of Sacramento pikeminnow collected from the North Fork Feather River, Plumas County, California, October 2008...... 25

7 Plasmodium containing Myxobolus species 2 in wet mount of gills from Sacramento pikeminnow collected from North Fork Feather River, Plumas County, California, October 2008...... 26

8 Dactylogyrus californiensis from wet mount of gills from Sacramento pikeminnow collected from North Fork Feather River, Plumas County, California, September 2007...... 28

9 Opistohaptor of Dactylogyrus californiensis showing haptoral anchors and marginal hooks. Specimen was from wet mount of gills from hardhead collected from North Fork Feather River, Plumas County, September 2007...... 29

10 Unidentified monogenetic trematode from wet mount of skin scraping from hardhead collected from North Fork Feather River, Plumas County, California, October 2007. Arrow points to haptoral anchors...... 31

LIST OF FIGURES (CONTINUED)

11 Haptoral anchors of unidentified monogenetic trematode from wet mount of skin scraping from hardhead collected from North Fork Feather River, Plumas County, California, October 2007...... 32

12 Black spot Neascus on skin and fins of Sacramento pikeminnow collected from North Fork Feather River, Plumas County, California, September 2007...... 34

13 Black spot Neascus metacercaria dissected out of its cyst from skin of hardhead collected from North Fork Feather River, Butte County, California, September 2007. Metacercaria was stained with Semichon’s carmine and counterstained with fast green...... 35

14 Ornithodiplostomum ptychocheilus metacercaria from mesentery of hardhead collected from North Fork Feather River, Butte County, California, September 2007. Specimen was stained with Semichon’s carmine and counterstained with fast green...... 36

15 Ornithodiplostomum ptychocheilus metacercaria within cyst on surface of liver from Sacramento pikeminnow collected from North Fork Feather River, Plumas County, California. September 2007...... 38

16 Edlintonia ptychocheila from intestine of hardhead collected from North Fork Feather River, Plumas County, California, April 2007. Specimen was stained with Semichon’s carmine and counterstained with fast green...... 40

17 Proteocephalan plerocercoid from intestine of Sacramento pikeminnow collected from the North Fork Feather River, Plumas County, California, October 2007. Specimen was stained with Semichon’s carmine and counterstained with fast green...... 42

18 Scolex from proteocephalan plerocercoid from intestine of Sacramento pikeminnow collected from North Fork Feather River, Plumas County, California, October 2007. Specimen was stained with Semichon’s carmine and counterstained with fast green...... 43

19 Unidentified larval nematode in gall bladder of hardhead collected from North Fork Feather River, Plumas County, California, September 2007...... 45

LIST OF FIGURES (CONTINUED)

20 Unidentified larval nematode from wet mount of liver of hardhead collected from North Fork Feather River, Plumas County, California, October 2008...... 46

21 Male Neoechinorhynchus rutili from intestine of hardhead collected from North Fork Feather River, Plumas County, California, April 2007. Stained with Semichon’s carmine and counterstained with fast green... 47

22 Female Neoechinorhynchus rutili from intestine of hardhead collected from North Fork Feather River, Plumas County, California, April 2007. Stained with Semichon’s carmine and counterstained with fast green...... 48

23 Proboscis of female Neoechinorhynchus rutili from intestine of hardhead collected from North Fork Feather River, Plumas County, California, April 2007. There were three rows of hooks with six hooks per row. Specimen was stained with Semichon’s carmine and counterstained with fast green...... 49

24 Lernaea cyprinacea attached to pelvic fin of hardhead collected from North Fork Feather River, Plumas County, California, October 2007... 52

25 Lernaea cyprinacea from Figure 24 removed from pelvic fin of hardhead collected from North Fork Feather River, Plumas County, California, October 2007...... 53

26 Cephalic horns and head of Lernaea cyprinacea from Sacramento pikeminnow collected from North Fork Feather River, Plumas County, California, September 2007...... 55

INTRODUCTION

Hardhead (Mylopharodon conocephalus) and Sacramento pikeminnow

(Ptychocheilus grandis) are in the fish family Cyprinidae. Both are endemic to

California and are native to the Sacramento-San Joaquin system, Russian River, and Napa River (Reeves 1964, Moyle 2002). Hardhead are closely related to

Sacramento pikeminnow (Gold and Avise 1977, Mayden et al. 1991) and are always found in association with them (Moyle et al. 1995). Together with

Sacramento sucker (Catostomus occidentalis), they form the pikeminnow- hardhead-sucker species assemblage which occupies lower to mid-elevation streams of the Sacramento-San Joaquin River watershed and the Russian River watershed (Moyle et al. 1995).

Hardhead were at one time considered “rough” or “trash” fish by state agencies (Moyle et al. 1983, Grant and Maslin 1999). There are no angling regulations for hardhead. Anglers are able to keep any number and any size in any waters open for fishing (California Department of Fish and Game 2008).

Historic management of hardhead usually involved removal or poisoning of hardhead and other non-game species like Sacramento pikeminnow and

Sacramento sucker in the belief that these species competed with and depressed populations of desirable game fish (Moyle et al. 1983). This belief still dominates the attitude of many anglers and the general public, although state agencies have changed their management policies. Hardhead populations have declined

1 2

in some areas, most likely due to habitat loss and predation by non-native fish species. Dams have isolated many populations of hardhead, increasing the risk of localized extinctions (Moyle 2002). As a result of these declines and isolation, hardhead are currently listed as a class three species of special concern by

California Department of Fish and Game (Moyle et al. 1995). Hardhead are also a United States Forest Service sensitive species (United States Forest Service

1998). This change in attitude and management status requires resource agencies to consider hardhead in management decisions. However, huge gaps still exist in the knowledge of hardhead life history (Moyle 2002, Grant and Maslin

1999), making management decisions difficult.

Sacramento pikeminnow present a different management challenge because of their predatory nature. While hardhead remain omnivorous throughout their life and are not known to prey on other fishes (Reeves 1964),

Sacramento pikeminnow are piscivorous. Brown and Moyle (1997) found that fishes made up more than 50% of the diet of Sacramento pikeminnow that were

151-200mm long in the Eel River, California. Some fish biologists believe that predation by Sacramento pikeminnow has contributed to salmonid declines.

However, Sacramento pikeminnow are usually not a major predator of salmonids, except under certain human-caused conditions (Bettelheim 2001).

Human-caused habitat degradation or alteration, such as dams, can give an advantage to Sacramento pikeminnow over salmonids by altering river

temperature and flows (Bettelheim 2001). Sacramento pikeminnow are abundant and are not currently listed under any regulatory framework by state or federal agencies. Although more widely studied than hardhead, there are still gaps in the understanding of Sacramento pikeminnow life history (Moyle 2002). One area in which knowledge is lacking for both Sacramento pikeminnow and hardhead is study of their parasites.

Noble (1960) encouraged the use of fishes and their parasite fauna as objects for ecological study: “The use of parasites as ecological labels provide an abundance of information about the habits and habitats of their hosts.”

Parasites can provide information about their hosts’ diet, geographic area, trophic level, seasonal patterns, and habitat preferences (Lim 1970, Muul 1970, Esch

1971, Price and Clancy 1983, Hernandez and Muzzall 1998). Equally important is the understanding of the role that hosts’ biology plays in parasite life cycles

(Muul 1970). Study of both the host and the parasite is vital to understanding the total biology of each (Noble 1960).

The role that parasites play in the life histories of California non-game native fishes is poorly understood. Parasites are an increasingly important component of studying the biology of fish, especially when parasites are suspected to play a role in hindering the recovery of endangered fish species

(Robinson et al. 1998, Choudhury et al. 2004). However, it is important to understand the ecological role parasites play in the life histories of fishes before

a species becomes endangered. Even parasites living in equilibrium with their hosts can have deleterious effects on an individual’s growth, survival, or reproductive fitness (Barber et al. 2000). Consequences can extend from individuals to populations, and understanding parasites’ effect on specific species is important in making management decisions. The first step in understanding the role that parasites play in fish species’ life histories is to survey and identify the parasites (Hoffman 1999).

Very little has been done on parasites of hardhead or Sacramento pikeminnow. Haderlie (1953) examined 20 hardhead for parasites. Only three species of parasites were recorded: a Neascus species (Class Trematoda), a

Cystidicola species (Class Nematoda), and Lernaea carassii (conspecific of

Lernaea cyprinacea) (Class Crustacea). Haderlie (1953) also examined 110

Sacramento pikeminnow for parasites. Seven parasite species were recorded: a

Neascus species, Plagioporus macrouterinus (Class Trematoda),

Posthodiplostomum minimum (Class Cestoidea), Proteocephalus cobraeformis

(conspecific of Proteocephalus torulosus) (Class Cestoidea), a Cystidicola

species, an Austrobdella species (Class Hirudinea), and Lernaea carassii

(conspecific of Lernaea cyprinacea). Haderlie’s (1953) study was limited to

helminths, copepods, and leeches, and did not include protozoa. The close

genetic relationship between hardhead and Sacramento pikeminnow and their

close association in rivers make it possible that hardhead and Sacramento pikeminnow could host similar parasites.

The objective of this study was to describe the parasites of hardhead and

Sacramento pikeminnow in the North Fork of the Feather River in Plumas and

Butte Counties, between its confluence with the East Branch of the North Fork

Feather and Lake Oroville. The North Fork of the Feather River was chosen as a study site because of management interests in this basin. In addition, there has been no study of hardhead and Sacramento pikeminnow parasites from the

Feather River. None of the fish in Haderlie (1953) came from the Feather River.

Understanding which parasites inhabit hardhead and Sacramento pikeminnow will lay groundwork for further study of the parasites of these cyprinids.

STUDY AREA

The Feather River basin above Lake Oroville has a watershed area of about 40,000 square kilometers. As with most rivers in the Sacramento-San

Joaquin drainage, the Feather River has been dammed for water storage and power generation. The Feather River basin is the primary source of water for the

California State Water Project (Carle 2004). Water is taken from Lake Oroville in

Butte County and shipped to Southern California via a series of rivers and aqueducts.

The North Fork of the Feather River is a major tributary of the Feather

River, contributing on average about 50% of the total inflow to Lake Oroville

(Koczot et. al 2005). The North Fork of the Feather River is heavily regulated for power generation before reaching Lake Oroville. It forms Pacific Gas and

Electric Company’s “Stairway of Power”, a series of dams, reservoirs, penstocks, and powerhouses. The “Stairway of Power” begins at Lake Almanor in Lassen

County and ends at Lake Oroville in Butte County. This study was conducted from the confluence of the North Fork Feather River with the East Branch of the

North Fork Feather downstream to the Poe reach, including all three hydropower reservoirs (Figure 1).

Rock Creek Reservoir is the first reservoir below the confluence of the unregulated East Branch of the North Fork Feather with the North Fork Feather

River. Rock Creek Reservoir is about 25.5 hectares, with a storage capacity of

5797 cubic meters. The river reach from Rock Creek Dam to Cresta Reservoir is

Figure 1. Map of study area in North Fork Feather River drainage in Plumas and Butte Counties, California. 7

about 13 kilometers. Cresta Reservoir is about 27 hectares with a storage capacity of 5427 cubic meters. The river reach from Cresta Dam to Poe

Reservoir is nearly 11 kilometers. Poe Reservoir is about 21.5 hectares with a storage capacity of 1480 cubic meters. The river reach from Poe Dam to Lake

Oroville is about 13 kilometers.

The North Fork Feather River in the study area is a relatively high gradient river which runs through a steep-walled canyon. A highway and railroad run alongside the river for most of its length and further constrain the channel.

Granite boulders and cobble are the dominant substrates. Smaller substrates are relatively rare due to retention by hydropower dams (Li 1994).

The river primarily consists of deeper water habitats of pools and runs separated by riffles under flows currently mandated by the Federal Energy

Regulatory Commission. These flows range from 3.1 cubic meters per second

(cms) to 9.9 cms in the summer, depending on the reach and the water year type. Pacific Gas and Electric Company conducted fish and habitat surveys within the study area at approximately 6.2 cms in the Cresta and Rock Creek reaches, and at 1.4 cms in the Poe Reach (Li 1994, Salmunovich 2005). They found that in the Cresta reach, deep pools made up the highest percentage of habitat (34.4%). In the Rock Creek reach, runs made up the highest percentage of habitat (30.2%), followed closely by deep pools (27.1%). Low gradient riffles made up the smallest percentage of habitat in both reaches (7.1% and 7.3%

respectively) (Salamunovich 2005). Pools made up the highest percentage of habitat (48.5%) and low gradient riffles made up the smallest percentage of habitat (5.6%) in the Poe reach (Li 1994).

Reservoirs in the North Fork Feather River have hydrologic characteristics more like long, deep riverine pools than lakes. Reservoirs are constrained within the steep walled canyons and are long, narrow and relatively shallow. Because of the high volume of water coming in and going out due to hydropower generation, residency time of water is short. Flow is maintained throughout the reservoirs. Hydropower generation causes the reservoirs to fluctuate daily by several feet (Federal Energy Regulatory Commission 2007). The reservoirs and deep pools in the river reaches are suitable habitat for hardhead and Sacramento pikeminnow, though dams have isolated populations of both species.

MATERIALS AND METHODS

I collected 32 hardhead and 14 Sacramento pikeminnow from the North

Fork Feather River. This included collections from Rock Creek Reservoir, Rock

Creek reach, Cresta Reservoir, and Cresta reach. Attempts to collect fish from

Poe Reservoir and Poe reach failed. All fish collected were greater than 75mm fork length to ensure that fish were at least one year old (Moyle et al. 1983).

Fish were collected in November 2005, October 2006, April 2006, April 2007, and during August to November 2007.

Fish were collected by hook and line sampling using artificial lures or bait.

Fish were also collected by baited minnow traps. Minnow traps were baited with dry dog food, sardines, canned cat food, white bread, or a combination of these baits. Fish were euthanized with an overdose of Finquel® (MS-222, tricaine methanesulfonate; Argent Chemical Laboratories, Redmond, Washington). Fish remained in Finquel® solution for at least 3 minutes after all opercular movements ceased. Fish were then placed in individually numbered plastic bags, put on ice, and transported to the Humboldt State University Fish

Pathology Laboratory within 48 hours. Methods of capture and euthanasia were approved by the Humboldt State University Institutional Animal Care and Use

Committee (IACUC 06/07.F.124.A).

In the laboratory, fish were examined for parasites. A written record of each fish necropsy was maintained by recording date of collection, fish species, and collection location from my field notebook onto a 3 x 5 card. Date of

10 11

necropsy, lengths, and weight were then recorded. Standard, fork, and total lengths were recorded to the nearest millimeter. Wet weight was measured to the nearest 0.1 gram. Sex of fish, and the types, locations in fish, and numbers of all parasites found were recorded as the necropsy progressed.

Numbered plastic bags used for transport were washed out into a Petri dish, and the fluid was examined under a dissecting microscope for any external parasites which may have been dislodged during transport. The external surface and fins of the fish were visually examined for parasites. Fin clippings and smaller fish were examined with a dissecting microscope. The blunt side of a scalpel was used to scrape mucus samples from the skin and gills. Wet mounts of scrapings were examined under a compound microscope.

Blood was obtained from the caudal artery or heart. The caudal fin was severed, and blood was collected from the artery. If blood could not be collected from the caudal artery, it was collected from the heart during the subsequent internal examination. Blood smears were prepared by placing a droplet of blood on the end of a clean microscope slide and using a second microscope slide to pull the blood into a thin layer across the first slide. Slides were then air dried, fixed in absolute methanol for one minute, and allowed to air dry again. Blood smears were stained with Wright-Giemsa stain. Slides were later examined under a compound microscope at 1000x magnification for blood parasites. Each slide was systematically scanned for 10 minutes (Pritchard and Kruse 1982).

Gills were removed and gill arches were examined under a dissecting microscope. Wet mounts of gill filaments were examined under a compound microscope. If monogenetic trematodes were detected, gills were placed in a jar with 1:4000 formalin solution and shaken to dislodge the trematodes. The solution was allowed to settle, and the material and gills were preserved in 10% formalin (Pritchard and Kruse 1982).

Eyes were removed and examined. The eye socket, surface, and back of the eye were visually examined. The eye was cut open and the lens and inner surface were examined under a dissecting microscope.

An internal examination of the fish proceeded from the outermost organs inwards. All major organs including gall bladder, peritoneum, mesenteries, gastrointestinal tract, liver, spleen, swim bladder, kidney, heart, gonads, musculature, and brain were examined under a dissecting microscope. Wet mounts of the gall bladder, spleen, liver, kidney, heart, gonads, and brain were examined under a compound microscope. Samples of bile were examined under a compound microscope. Liver, spleen, and gonads were weighed to the nearest 0.01 gram. When distended enough to be found, the urinary bladder was examined under a dissecting microscope, and a wet mount was examined under a compound microscope.

Stomach and intestine were removed, slit along one side and scraped into a Petri dish. The stomach and intestinal wall were then examined under a

dissecting microscope. Stomach and intestinal contents were diluted with saline, shaken to dislodge any parasites, allowed to settle, decanted once to several times, and examined under a dissecting microscope (Pritchard and Kruse 1982).

Digenetic trematodes and cestodes were preserved by fixing with hot alcohol, formalin, and glacial acetic acid solution (AFA). All trematodes and cestodes were small enough that flattening under a coverslip during fixation was not needed. Acanthocephalans were placed in distilled water to extrude the proboscis, and then fixed in hot AFA for 24 hours. All parasites were then transferred to 70% ETOH in labeled screw top vials. Digenetic trematodes, cestodes, and acanthocephalans were stained with Semichon’s carmine, destained and dehydrated, and counterstained with fast green. Specimens were then dehydrated further, cleared in methyl salicylate, and mounted on microscope slides with Permount mounting medium (Pritchard and Kruse 1982).

Nematodes and copepods were preserved by fixing in hot glycerin alcohol

(GL-70). Parasites were cleared by allowing the alcohol to slowly evaporate.

Nematodes and copepods were mounted between two different sized coverslips in glycerin jelly. Both coverslips were then mounted to microscope slides with

Permount. Monogenetic trematodes were fixed in 10% formalin. Parasites were mounted on microscope slides in Gray and Wess Medium (polyvinyl alcohol,

70% acetone, glycerin, lactic acid, and distilled water) under a single coverslip.

The coverslip was ringed with clear nail polish (Pritchard and Kruse 1982).

Tissue samples preserved for histological sectioning were fixed for 24 hours in AFA and stored in 70% alcohol. Samples were dehydrated in TBA

(tertiary butyl alcohol) and embedded in paraffin. Tissue was sectioned using a microtome, stained with hemotoxylin, and counterstained with eosin (Pritchard and Kruse 1982).

Parasites were identified using taxonomic keys from Hoffman (1999).

Additional taxonomic keys were used as needed (Mackiewicz 1970, Hoffman

1976, Arai 1989, Amin 2002). Parasite identification was verified by Dr. Gary

Hendrickson. Parasites were photographed using a Nikon Coolpix 8800 digital camera equipped with a microscope adapter system from Martin Microscopes.

RESULTS

Thirty-two hardhead and 14 Sacramento pikeminnow were examined for parasites. All Sacramento pikeminnow examined were infected with at least one parasite. Thirty-one hardhead were infected with at least one parasite. On average, Sacramento pikeminnow were infected with four species of parasites and hardhead were infected with three species of parasites. No single fish was infected with more than six species of parasites. I found six new host records for hardhead and four new host records for Sacramento pikeminnow. The prevalence, mean intensity, and locations of parasites found are presented in

Tables 1 (hardhead) and 2 (Sacramento pikeminnow). A description of each parasite follows the tables.

15 Table 1. Prevalence, mean intensity, and locations of parasites found in 32 hardhead collected from the North Fork Feather River in Butte and Plumas Counties, California, from November 2005 to November 2007.

Hardhead (n = 32)

Mean intensity (range in number Parasite Number of fish infected (%) per fish infection) Location of parasites

PROTOZOA: Myxobolus species 1* 26 (81) ** (1 - 1000's) gills, spleen, kidney, liver

MONOGENEA: Dactylogyrus californiensis* 19 (59) ** (1 - 100's) gills Unidentified monogenetic trematode* 2 (6) 1 (1) skin

TREMATODA: Black spot metacercariae Neascus 6 (19) ** (1 - 100's) skin Ornithodiplostomum ptychocheilus* 7 (22) ** (1 - 100's) mesentery

CESTOIDEA: Edlintonia ptychocheila* 1 (3) 16 (16) intestine

NEMATODA: Unidentified larval nematode 1 (3) 1 (1) gall bladder

ACANTHOCEPHALA: Neoechinorhynchus rutili* 4 (12) 7.5 (1 - 23) intestine

COPEPODA: Lernaea cyprinacea 22 (69) 3.1 (1 - 11) skin, gills, fins

* indicates new host record ** value not calculated 16

Table 2. Prevalence, mean intensity, and locations of parasites found in 14 Sacramento pikeminnow collected from the North Fork Feather River in Butte and Plumas Counties, California, from November 2005 to November 2007.

Sacramento pikeminnow (n = 14)

Mean intensity (range in numbers Parasite Number of fish infected (%) per fish infection) Location of parasites

PROTOZOA: Myxobolus species 1* 13 (93) ** (1 - 1000's) gills, spleen, kidney, liver Myxobolus species 2* 3 (21) ** (1 - 1000's) gills Trichodina/Paratrichodina* 1 (7) ** (**) gills

MONOGENEA: Dactylogyrus californiensis 9 (64) ** (1 - 100's) gills

TREMATODA: Black spot metacercariae Neascus 11 (79) ** (1 - 100's) skin Ornithodiplostomum ptychocheilus* 4 (29) ** (1 - 100's) mesentery

CESTOIDEA: Proteocephalan plerocercoid 1 (7) 2 (2) intestine

NEMATODA: Unidentified larval nematode 4 (29) 1 (1) liver, mesentery

COPEPODA: Lernaea cyprinacea 6 (43) 2.8 (1 - 7) skin

* indicates new host record ** value not calculated 17

Trichodina/Paratrichodina species

Only one Sacramento pikeminnow was infected with an unidentified

Trichodina or Paratrichodina species. The parasite was found on the gills of the pikeminnow, but there were too few parasites for identification. The fish had less than 30 of these parasites. An exact count could not be made because several parasites were broken and only fragments of denticulate rings remained. The gills of this pikeminnow were also infected with several Dactylogyrus californiensis and myxospores of Myxobolus species 1.

The Trichodina/Paratrichodina parasite had tripartite denticles with a curved outer blade and a straight inner thorn, both similar in size and narrow and long in shape. Photographs taken of the parasites (Figure 2) were not detailed enough to determine to which genus the parasite belongs. The number of turns of the adoral cillary spiral needs to known in order to differentiate between

Trichodina and Paratrichodina (Hoffman 1999). The adoral cillary spiral was not visible in the photographs. Neither Trichodina nor Paratrichodina species have previously been reported in Sacramento pikeminnow.

The members of the family Trichodinidae are mobile protozoa, usually with a highly distinctive denticulate ring (Hoffman 1999). They are parasites of a wide range of aquatic organisms (Van As and Basson 1989). Species of this family occur primarily on the skin and gills of fishes (Hoffman 1999). Some species of

Figure 2. Trichodina/Paratrichodina species from wet mount of gills from Sacramento pikeminnow collected from the North Fork Feather River, Plumas County, California, October 2007.

Trichodina are seasonal, with densities of parasites higher in cooler weather

(Ogut and Palm 2005).

Myxobolus species

I found two Myxobolus species; one was found in the gills, spleen, liver, and kidney of both hardhead and Sacramento pikeminnow. The second

Myxobolus species was found in the gills of Sacramento pikeminnow. These are the first host records of Myxobolus in hardhead and Sacramento pikeminnow.

Myxobolus species 1 (Figure 3) was the most common parasite in this

study, occurring in 26 hardhead and 13 Sacramento pikeminnow. Myxobolus

species 1 had myxospores which were ellipsoid in shape. Measurements were taken of 10 fresh specimens from hardhead and are reported as range with means ± standard deviation in parentheses. Spores measured 13.6-17.9 µm in length (15.6 ± 1.7) and 7.8-10.2 µm in width (9.1 ± 0.8). Polar capsules were pyriform, sub-apical and frequently unequal in size with four to five turns of the polar filaments. The longer polar capsules measured 5.8-9.1 µm (7.3 ± 1.0) in length and 3.9-5.3 µm (4.8 ± 0.5) in width. The shorter polar capsules measured

4.4-6.7 µm (5.8 ± 0.9) in length and 3.4-4.8 µm (3.9 ± 0.6) in width.

Myxospores were found distributed throughout the body in gills, spleen, liver and kidney, usually in small numbers (Figures 4-5). “Groups” of mature spores in the spleen and kidney were found in many fish, often in association

Figure 3. Myxobolus species 1 spore from wet mount of spleen of hardhead collected from North Fork Feather River, Plumas County, California, November 2005.

Figure 4. Myxobolus species 1 mature spore in kidney histological section from hardhead collected from North Fork Feather River, Plumas County, California, September 2007. Section was stained with hemotoxylin and counterstained with eosin.

Figure 5. Group of Myxobolus species 1 spores in melanomacrophage center in wet mount of spleen of hardhead collected from North Fork Feather River, Plumas County, California, October 2008.

with melanomacrophage centers, but these groups did not appear to be the

plasmodium stage. These groups were more common in younger fish.

Longshaw et al. (2005) found several Myxobolus species from various cyprinid

species juveniles with a plasmodium which formed in the musculature. When the

plasmodium ruptured, mature spores were dispersed around the body via the

blood and lymphatic systems. Spores were occasionally found in the gills,

spleen, liver, and kidney, often within macrophage aggregates (Longshaw et al.

2005).

Myxobolus species 2 (Figure 6) occurred in the gills of three Sacramento

pikeminnow. Spores were ovoid to ellipsoid in shape. Measurements were taken

of 10 fresh specimens from Sacramento pikeminnow and are reported as range

with means ± standard deviation in parentheses. Spores measured 8.2-12.1 µm

(10.7 ± 1.2) in length and 7.8-9.7 µm (8.9 ± 0.7) in width. The polar capsules

were pyriform, apical, and usually equal in size with six to seven turns of the

polar filaments. The polar capsules measured 4.3-6.3 µm (5.1 ± 0.5) in length

and 2.4-3.8 µm (2.9 ± 0.5) in width.

Most of the spores were within white, cyst-like plasmodia located in the

gills which varied in size from less than a millimeter to several millimeters in

length (Figure 7). These three Sacramento pikeminnow also had Myxobolus species 1 spores in the spleen.

Figure 6. Myxobolus species 2 spores in wet mount of gills of Sacramento pikeminnow collected from the North Fork Feather River, Plumas County, California, October 2008.

Figure 7. Plasmodium containing Myxobolus species 2 in wet mount of gills from Sacramento pikeminnow collected from North Fork Feather River, Plumas County, California, October 2008.

Myxosporea is a widespread class with over 1350 species described worldwide (Longshaw et al. 2005). Over 100 species of myxozoans have been described from cyprinids alone (Longshaw et al. 2005). Many myxozoan species are considered relatively innocuous to their fish host, but some, such as

Myxobolus cerebralis, the causative agent of whirling disease, have had major impacts on salmonids in some areas of the United States (Modin 1998).

Although there have been many descriptions of myxozoans, there have been few studies on the pathological effects, distribution, or development of most myxozoans (Longshaw et al. 2005).

Dactylogyrus californiensis

Dactylogyrus californiensis (Figures 8-9) were found on the gills of 19 hardhead and nine Sacramento pikeminnow. Dactylogyrus californiensis have not been previously recorded in hardhead. The genus Dactylogyrus is characterized as having a single pair of haptoral anchors with usually 14, sometimes 16 marginal hooks (Mizelle 1962, Hoffman 1999). Dactylogyrus primarily parasitize the gills of cyprinids in freshwater (Hoffman 1999).

Dactylogyrus californiensis was first described by Mizelle (1962) from

Sacramento pikeminnow collected from Folsom Lake near Sacramento,

California. They differ from other Dactylogyrus species by having a series of three to seven folds in the cuticle about midway down the body on the left margin

(Mizelle 1962). The cirrus and accessory piece are similar to Dactylogyrus

Figure 8. Dactylogyrus californiensis from wet mount of gills from hardhead collected from North Fork Feather River, Plumas County, California, April 2006.

Figure 9. Opistohaptor of Dactylogyrus californiensis showing haptoral anchors and marginal hooks. Specimen was from wet mount of gills from hardhead collected from North Fork Feather River, Plumas County, April 2006.

banghami but lack a proximal process on the cirrus and have a dual articulation

of the accessory piece (Mizelle 1962).

Unidentified monogenetic trematode

An unidentified monogenetic trematode (Figures 10-11) was found on the

skin of two hardhead. Both specimens were destroyed when trying to transfer

them from the wet mount to preservative. The skin of each hardhead was

carefully scraped and all the fins preserved, but no additional trematodes were

found. Photographs taken of the trematodes were not detailed enough to identify

the species. The trematodes looked similar to Gyrodactylus with no visible eye spots. The haptoral anchors had two transverse bars and a ventral shield on the ventral transverse bar of the haptoral anchors. However, in Gyrodactylus, the

embryo has anchor hooks which are sometimes visible in the body of the adult.

These were not visible in either specimen. There were only 10 marginal hooks

visible in the photographs. Although Gyrodactylus has 16 marginal hooks, it is

possible that marginal hooks were lost when the specimens were scraped from

the skin of the hardhead.

Unidentified Neascus

I found black cysts similar to those described by Haderlie (1953) in six

hardhead and 11 Sacramento pikeminnow. Haderlie (1953) found cysts

“embedded in the scales, under the scales, and fairly deep in the connective

tissue of the epidermis of the hosts”. I found black spot Neascus in

Figure 10. Unidentified monogenetic trematode from wet mount of skin scraping from hardhead collected from North Fork Feather River, Plumas County, California, November 2007. Arrow points to haptoral anchors.

Figure 11. Haptoral anchors of unidentified monogenetic trematode from wet mount of skin scraping from hardhead collected from North Fork Feather River, Plumas County, California, November 2007.

fins, in scales, under scales, and in the skin in both hardhead and Sacramento

pikeminnow (Figure 12). I dissected the metacercariae out of the cysts after

preservation and staining. Metacercariae were oval in shape, divided into fore-

and hindbodies but had no other identifiable key characteristics and could not be

identified to species (Figure 13).

Neascus is a larval genus of the family Diplostomatidae (Hoffman 1999).

Haderlie (1953) described an unidentified Neascus from the skin of several

California species, including hardhead and Sacramento pikeminnow. The cysts

formed by these strigeid metacercariae were dark in color, similar to the

metacercariae of Uvuliver ambloplites. “Black spot” or “black grub” metacercariae have often been reported in the literature and are commonly identified as Neascus species, Uvuliver ambloplites, or merely “black spot” metacercariae (Hoffman 1999, Haderlie 1953, Robinson et al. 1998). In many

“black spot/black grub” metacercariae, the trematodes reach adulthood in piscivorous birds (Haderlie 1953), while fish serve as a second intermediate host.

Neascus of Ornithodiplostomum ptychocheilus

Neascus of Ornithodiplostomum ptychocheilus (Figure 14) was found in

the mesenteries of seven hardhead and four Sacramento pikeminnow. Cysts

containing metacercariae were found throughout the mesentery of infected fish.

No metacercariae were found in the brain or brain cavity of either species.

Figure 12. Black spot Neascus on skin and fins of Sacramento pikeminnow collected from North Fork Feather River, Plumas County, California, September 2007.

Figure 13. Black spot Neascus metacercaria dissected out of its cyst from skin of hardhead collected from North Fork Feather River, Butte County, California, September 2007. Metacercaria were stained with Semichon’s carmine and counterstained with fast green.

Figure 14. Ornithodiplostomum ptychocheilus metacercaria from mesentery of hardhead collected from North Fork Feather River, Butte County, California, September 2007. Specimen was stained with Semichon’s carmine and counterstained with fast green.

Occasionally, cysts were found in “pockets” on the surface of the liver or nearly within the liver (Figure 15). Hoffman (1958) found cysts in the brain tissue of fathead minnows (Pimephales promelas), but noted that most were on the surface of the brain. He assumed that some of the cysts on the surface of the brain were sunken into the brain tissue because of reabsorbtion, but he noted the cysts were still separated from the actual brain tissue by the meninges. He commented that this was most often the case under crowded conditions

(Hoffman 1958). Reabsorbtion is likely the reason metacercariae were sunken into the liver tissue in my study. Ornithodiplostomum ptychocheilus have not previously been recorded in hardhead or Sacramento pikeminnow.

Ornithodiplostomum ptychocheilus are members of the family

Diplostomatidae (Hoffman 1999). Fish (mostly cyprinids or catostomids) serve as second intermediate host of this parasite, with the first intermediate host being a

Physa snail. The parasites reach maturity in mergansers (Mergus species). The metacercariae locate primarily in two places in fish species, the brain or the mesentery (Hoffman 1958, Hendrickson 1986, Hoffman 1999). Site “selection” varies by fish hosts (Hoffman 1958). Metacercariae have been found in the brain and brain cavity of fathead minnows, in the brain and mesenteries of shiner species (Notropis species), but only in the mesenteries of catostomids and pikeminnow species (Hoffman 1958, Amin 1969, Hendrickson 1986, Hoffman

Figure 15. Ornithodiplostomum ptychocheilus metacercaria within cyst on surface of liver from Sacramento pikeminnow collected from North Fork Feather River, Plumas County, California. October 2007.

1999). Hendrickson (1979) concluded that migration by Ornithodiplostomum

ptychocheilus to the brain of fathead minnows is by “directed, non-random

movement.” Cercariae migrate to the brain of fathead minnows by a clearly

defined route via the nervous system (Hendrickson 1979). The unusual route

“chosen” by Ornithodiplostomum ptychocheilus in fathead minnows suggests that

migration patterns may be species specific (Hendrickson 1979).

Edlintonia ptychocheila

Edlintonia ptychocheila (Figure 16) were found in the intestine of one hardhead. These specimens matched the description given by Mackiewicz

(1970), except in total length. Gravid worms measured 15-29 mm long in his description, but gravid worms from the hardhead measured 3-11 mm long.

Tapeworms in the order Caryophyllidea are intestinal parasites of freshwater fishes (primarily Catostomidae and Cyprinidae) with a nearly global distribution. They lack segmentation and have a single set of reproductive organs (Oros et al. 2008). Edlintonia ptychocheila is the only species in its genera in the family Capingentidae (Mackiewicz 1970). Edlintonia ptychocheila has a cuneiform scolex without bothria or loculi, an H-shaped ovary, and pre- ovarian and post-ovarian vitellaria which are not continuous (Mackiewicz 1970).

Edlintonia ptychocheila has been found in northern pikeminnow (Ptychocheilus

Figure 16. Edlintonia ptychocheila from intestine of hardhead collected from North Fork Feather River, Plumas County, California, April 2007. Specimen was stained with Semichon’s carmine and counterstained with fast green.

oregonense) and peamouth chub (Mylocheilus caurinus). It has not previously been reported from hardhead.

Proteocephalan plerocercoids

One Sacramento pikeminnow was infected with proteocephalan plerocercoids (Figure 17). The scolex was of the proteocephaloid type with four suckers (Figure 18). No internal organs were visible. Although the plerocercoids did bear some resemblance to Haderlie’s (1953) illustration of an immature

Proteocephalus cobraeformis specimen, the plerocercoids were unidentifiable to species.

Tapeworms in the order Proeocephalidea have a scolex with four simple suckers, have segment-like proglottids, and are parasitic in fishes, amphibians, and reptiles (Hoffman 1999). Haderlie (1953) described a new species of

Proteocephalus in Sacramento pikeminnow which he named Proteocephalus cobraeformis. Recent studies have challenged whether Proteocephalus cobraeformis is a separate species or conspecific with Proteocephalus torulosus, a common parasite of cyprinids in the palearctic region (Scholz and Hanzelová

1999). Proteocephalus cobraeformis has not been reported since its original description (Scholz and Hanzelová 1999).

Unidentified larval nematode

Larval nematodes were found in one hardhead and four Sacramento pikeminnow. The nematodes in Sacramento pikeminnow were found

Figure 17. Proteocephalan plerocercoid from intestine of Sacramento pikeminnow collected from the North Fork Feather River, Plumas County, California, October 2007. Specimen was stained with Semichon’s carmine and counterstained with fast green.

Figure 18. Scolex from proteocephalan plerocercoid from intestine of Sacramento pikeminnow collected from North Fork Feather River, Plumas County, California, October 2007. Specimen was stained with Semichon’s carmine and counterstained with fast green.

in the musculature under the skin, in the mesentery, and in the liver. The nematodes had migrated from their place of origin with the path of their movement easily seen from tracks left through the tissue. One larval nematode was found in the gall bladder of a hardhead (Figure 19), but it was not clear if it migrated there from somewhere else.

Mouth parts are often necessary for positive identification of nematodes

(Hoffman 1999). The nematodes broke and the mouth parts were lost when removed from the Sacramento pikeminnow. No identification was possible because the specimens were immature and the mouth parts were missing.

Because of their immaturity, it is unlikely the specimens could have been identified even if the mouth parts and anterior regions were intact. The nematode from the hardhead was minute and was lost during preservation.

Photographs taken of wet mounts of the nematodes did not show mouth parts and anterior region in sufficient detail for identification (Figure 20). Haderlie

(1953) found a Cystidicola species in the intestines of both hardhead and

Sacramento pikeminnow, but no nematodes were found in the intestines in this study.

Neoechinorhynchus rutili

Fourteen male and 16 female Neoechinorhynchus rutili (Figures 21-23) were recovered from four hardhead. Neoechinorhynchus species have not previously been recorded in hardhead. Specimens were identified as

Figure 19. Unidentified larval nematode in gall bladder of hardhead collected from North Fork Feather River, Plumas County, California, November 2005.

Figure 20. Unidentified larval nematode from wet mount of liver of hardhead collected from North Fork Feather River, Plumas County, California, October 2007.

Figure 21. Male Neoechinorhynchus rutili from intestine of hardhead collected from North Fork Feather River, Plumas County, California, April 2007. Specimen was stained with Semichon’s carmine and counterstained with fast green.

Figure 22. Female Neoechinorhynchus rutili from intestine of hardhead collected from North Fork Feather River, Plumas County, California, April 2007. Specimen was stained with Semichon’s carmine and counterstained with fast green.

Figure 23. Proboscis of female Neoechinorhynchus rutili from intestine of hardhead collected from North Fork Feather River, Plumas County, California, April 2007. There were three rows of hooks with six hooks per row. Specimen was stained with Semichon’s carmine and counterstained with fast green.

Neoechinorhynchus rutili based on measurements of the proboscis, arrangement of proboscis hooks, lengths of proboscis hooks, and length and width of the worms. Specimens were also similar to the description of Neoechinorhynchus salmonis, a close relative of Neoechinorhynchus rutili (Ching 1984). The sexual organs of the acanthocephalans in this study were closer to the description of

Neoechinorhynchus salmonis (Ching 1984) than to Neoechinorhynchus rutili.

However, worms were more similar in length measurements and in measurements of the proboscis and proboscis hooks to Neoechinorhynchus rutili than to Neoechinorhynchus salmonis (Table 3) (Arai 1989).

Ancanthocephala are parasitic “thorny-headed” worms with a retractable proboscis with chitinoid hooks which they use to attach to the intestinal wall of their host. They have separate sexes and lack an alimentary canal (Hoffman

1999). Neoechinorhynchus is one of the largest genera of Acanthocephala

(Amin 2002).

Lernaea cyprinacea

Twenty-two hardhead and six Sacramento pikeminnow were infected with

Lernaea cyprinacea (Figure 24). Parasites were found attached to the skin, fins, and gills. There was often tissue damage evident at the attachment sites (Figure

25). Haderlie (1953) previously found Lernaea carassii (conspecific of Lernaea cyprinacea) on both hardhead and Sacramento pikeminnow.

Table 3. Proboscis and hook measurements in micrometers between Neoechinorhynchus from hardhead collected from the North Fork of the Feather River (Butte and Plumas Counties, CA) and N. rutili and N. salmonis (measurements from Arai 1989).

Male N. rutili N. salmonis Hardhead Neoechinorhynchus (mean, n=13) Proboscis 79-136 L 80-120 L 122-171 L (156) 79-120 W 90-150 W 107-131 W (120)

Hooks anterior 45-82 49-64 43-64 (51) middle 26-44 29-36 19-28 (24) posterior 19-34 20-26 14-22 (18)

Female N. rutili N. salmonis Hardhead Neoechinorhynchus (mean, n=13) Proboscis 90-252 L 90-120 L 146-180 L (169) 93-132 W 100-160 W 112-141 W (130)

Hooks anterior 52-84 56-71 55-66 (60) middle 29-46 28-40 20-31 (27) posterior 22-34 22-34 16-23 (19)

Figure 24. Lernaea cyprinacea attached to pelvic fin of hardhead collected from North Fork Feather River, Plumas County, California, October 2007.

Figure 25. Lernaea cyprinacea from Figure 24 removed from pelvic fin of hardhead collected from North Fork Feather River, Plumas County, California, October 2007.

Lernaea cyprinacea are copepods and are commonly called “anchor

parasites” or “anchor worms”. There are many species in the genus Lernaea.

Only females are parasitic and develop cephalic horns that form a holdfast which

grows into the host tissue (Figure 26). Males are not parasitic on fish. Lernaea

cyprinacea can be highly pathogenic because of tissue damage caused by their

attachment, mode of feeding, and secondary infections at the site of attachment

(Woo and Shariff 1990). Lernaea cyprinacea is such a generalist that Hoffman

(1999) stated that “it can probably infect all freshwater fishes and even frog tadpoles and salamanders”. Lernaea cyprinacea has become established

worldwide, likely due to fish importation (Hoffman 1976).

Figure 26. Cephalic horns and head of Lernaea cyprinacea from Sacramento pikeminnow collected from North Fork Feather River, Plumas County, California, September 2007.

DISCUSSION

Hardhead and Sacramento pikeminnow share a number of parasites.

This is expected given their close association in rivers and close genetic relationship. Lernaea cyprinacea, a Myxobolus species, Ornithodiplostomum ptychocheilus, a “black spot” Neascus species, and Dactylogyrus californiensis were found on both hardhead and Sacramento pikeminnow. These parasites tend to be generalists or parasites acquired through the environment rather than through fishes’ diet.

Lernaea cyprinacea is such a generalist it is likely able to infect any aquatic species that it encounters (Hoffman 1999). A free-swimming copepodid finds a suitable host and passes through five successive copepodid stages unattached on the surface of the host before the female permanently attaches to the host and becomes parasitic.

Myxobolus species infect their hosts through triactinomyxon spores which are released into the environment from oligachaete intermediate hosts (Modin

1998). Another shared parasite, Ornithodiplostomum ptychocheilus, infects hosts through free-swimming cercariae which penetrate a host externally and migrate through the body of the host to either the viscera or the brain where they encyst and develop into metacercariae (Hoffman 1999). “Black spot” Neascus species infect their hosts in a way similar to Ornithodiplostomum ptychocheilus, but encyst in the skin, scales, or fins.

56 57

The life cycle of Dactylogyrus californiensis, another shared parasite, has not been studied, but Dactylogyrus, in general, passes from host to host through the environment like many monogenetic trematodes. An adult monogenetic trematode releases an egg into the environment which hatches into a free- swimming oncomiracidium which then finds and infects a suitable host. Many monogenetic trematodes are highly host-specific. It is unknown how host-specific

Dactylogyrus californiensis is. However, Dactylogyrus californiensis has previously been recorded only from Sacramento pikeminnow. Hardhead are closely related to Sacramento pikeminnow. Thus, it is conceivable that these two fish could share parasites with one another which could not be shared with other species.

Parasites which differed between the two fish species were primarily found in the intestine and are probably diet-related. Edlintonia ptychocheila and

Neoechinorhynchus rutili were found only in hardhead. Proteocephalan plerocercoids were found only in Sacramento pikeminnow. When they are young, hardhead and Sacramento pikeminnow have a similar diet of macroinvertebrates (Moyle et al. 1995, Brown and Moyle 1997). After

Sacramento pikeminnow reach a certain size, they become primarily piscivorous and occasionally feed on other large prey such as crayfish (Brown and Moyle

1997). As adults, hardhead become omnivorous, feeding on large invertebrates, crayfish, and filamentous algae (Reeves 1964, Moyle et al. 1995).

Several Edlintonia ptychocheila, a caryophyllid tapeworm, were found in one hardhead. Caryophyllid tapeworms generally are found in omnivorous fishes such as catastomids and more rarely, cyprinids (Mackiewicz 1970). Caryophyllid tapeworms generally use oligachaetes as intermediate hosts (Hoffman 1999).

This could explain their absence in this study from adult Sacramento pikeminnow, which feed primarily on fish.

Four adult hardhead contained the acanthocephalan, Neoechinorhynchus rutili. Acanthocephalans use isopods, copepods, amphipods, or ostracods as intermediate hosts (Hoffman 1999). An infected intermediate host usually must be ingested in order for the acanthocephalan to infect its final fish host. However, fishes other than a final host can sometimes serve as paratenic hosts. It is unknown if Neoechinorhynchus rutili utilizes paratenic fish hosts. If not, diet could explain the absence of acanthocephalans in adult Sacramento pikeminnow.

Two proteocephalan plerocercoids were found in one Sacramento pikeminnow. Proteocephalan cestodes utilize copepods as a first intermediate host. Sacramento pikeminnow could be infected when young during their macroinvertebrate feeding stage. However, plerocercoids were found in adult fish, which are primarily piscivorous. Small prey fishes play an important role in transmission of some proteocephalan cestodes and serve as a paratenic host

(Scholz 1999). Proteocephalans are unable to grow or develop in these paratenic

fish hosts, but are a potential source of infection for predatory fish (Scholz 1999) such as Sacramento pikeminnow. It is also possible that Sacramento pikeminnow are unsuitable definitive hosts for these plerocercoids.

Another possibility for the absence of shared intestinal parasites besides diet is seasonality of parasite abundance. Parasite abundance often varies with the seasons (Hernandez and Muzzall 1998, Choudhury et al. 2004, Fellis and

Esch 2004, Hafizuddin and Bashirullah 2005). Seasonal variation can be due to many different factors including temperature, feeding habits of host species, availability of parasite larvae, and longevity of parasite species (Fellis and Esch

2004, Hafizuddin and Bashirullah 2005). Most of the fish collected for this study were caught in fall with only a few fish caught in spring. Fish caught in spring were all hardhead. These hardhead had high numbers of intestinal parasites; a single fish had 23 Neoechinorhynchus rutili and another individual had 16

Edlintonia ptychocheila. Fish caught in fall had very few intestinal parasites.

Fall-caught individuals with intestinal parasites usually had only one or two parasites each. It is possible that some parasites which have a higher abundance in the spring, particularly in pikeminnow, were missed in this study.

A possible explanation for the low number of intestinal parasites in

Sacramento pikeminnow is the low numbers and young age of Sacramento pikeminnow collected for this study. Sacramento pikeminnow were harder to capture than hardhead. Hardhead were easily caught using a worm-baited hook

and line, usually in shallow water. Adult Sacramento pikeminnow were caught using lures which imitated fish, but the Sacramento pikeminnow were usually in deeper water which made it more difficult to find and catch them. However, juvenile Sacramento pikeminnow were easily caught using baited minnow traps.

Most of the Sacramento pikeminnow in this study were less than 15 centimeters in fork length. Sacramento pikeminnow of this size from the North Fork Feather

River are under three years of age (Moyle et al. 1983). In general, older fish tend to have more parasites than younger fish (Fellis and Esch 2004). This could explain, in part, low numbers of intestinal parasites in Sacramento pikeminnow in this study.

I found nine species of parasites in hardhead, and nine species of parasites in Sacramento pikeminnow. I found a total of 12 parasite species in this study. The only previous study of the parasites of hardhead and Sacramento pikeminnow was done by Haderlie (1953). Haderlie (1953) found three species of parasites on hardhead and seven species of parasites on Sacramento pikeminnow. Haderlie (1953) found seven total parasites species in hardhead and Sacramento pikeminnow.

There was little overlap in parasite species found in this study with

Haderlie (1953). Haderlie (1953) found a “black spot” Neascus species on hardhead and Sacramento pikeminnow which was similar to the “black spot”

Neascus species found on both fish species in this study, though it is impossible

to know if they are the same species. Lernaea cyprinacea was found previously by Haderlie (1953) on both hardhead and Sacramento pikeminnow. Haderlie found a Proteocephalus tapeworm in Sacramento pikeminnow, which he described and named Proteocephalus cobraeformis. I also found proteocephalan tapeworms in one Sacramento pikeminnow, although I could not identify them to species because they were immature.

I found several species of parasites that Haderlie (1953) did not find in hardhead and Sacramento pikeminnow. I found Trichodina/Paratrichodina species in Sacramento pikeminnow and two Myxobolus species in hardhead and

Sacramento pikeminnow. Dactylogyrus californiensis were found in both hardhead and Sacramento pikeminnow, and one unidentified monogenetic trematode was found on hardhead. I found Neascus of Ornithodiplostomum ptychocheilus in both hardhead and Sacramento pikeminnow. I also found

Edlintonia ptychocheila and Neoechinorhynchus rutili in hardhead.

Haderlie (1953) found four parasite species in Sacramento pikeminnow and hardhead that I did not find in my study. Haderlie (1953) found

Posthodiplostomum minimum, Plagioporus macrouterinus, and an Astrobella species in Sacramento pikeminnow. Haderlie (1953) also found Cystidicola nematodes in the intestines both hardhead and Sacramento pikeminnow.

It is possible that Posthodiplostomum minimum found by Haderlie (1953) in Sacramento pikeminnow was Ornithodiplostomum ptychocheilus.

Posthodiplostomum minimum and Ornithodiplostomum ptychocheilus have similar lifecycles, share first and second intermediate hosts, and encyst as metacercariae in mesenteries and brains of their hosts (Schleppe and Goater

2004). Hoffman (1958) found that Ornithodiplostomum ptychocheilus was indistinguishable from Posthodiplostomum minimum at certain stages of metacercarial development. Haderlie (1953) found great variation in the size and body proportion in Posthodiplostomum minimum metacercariae in Sacramento pikeminnow. Some of these metacercariae match the description of

Ornithodiplostomum ptychocheilus (Haderlie 1953).

I found larval nematodes in both hardhead and Sacramento pikeminnow.

The larval nematodes were unidentifiable, and it is unlikely they were Cystidicola.

Though Haderlie (1953) found Cystidicola species in the intestine, Cystidicola is usually found in the swim bladder (Hoffman 1999). Larval nematodes in this study were found in the gall bladder, liver, and migrating through the musculature.

Numbers of parasite species recorded in other studies for the genus

Ptychocheilus widely vary (Hoffman 1999). Six parasite species have been recorded for Colorado pikeminnow (Ptychocheilus lucius), while 46 parasite species have been recorded for northern pikeminnow (Ptychocheilus oregonensis) (Hoffman 1999). Including this study, thirteen parasite species have been recorded for Sacramento pikeminnow. Eleven parasite species have

now been recorded for hardhead.

Price and Clancy (1983) found that the geographic range of a host accounts for a large proportion of the variance in number of parasites per host species. Fish species with a large geographic range tend to have the largest number of parasites (Price and Clancy 1983). Of the three Ptychocheilus species, Sacramento pikeminnow has the smallest geographic range and northern pikeminnow has the largest. Hardhead has a slighter smaller geographic range than Sacramento pikeminnow. The lower numbers of recorded parasites for Sacramento pikeminnow and hardhead compared to northern pikeminnow is probably due, in part, to the size of their respective geographic range.

Fish species with the most studied parasite fauna are often those which have large or worldwide distribution, or which have cultural or commercial value

(Noble 1960, Muul 1970). Cyprinids which have been more widely studied often have recorded parasite species numbers close to those recorded for northern pikeminnow (Hoffman 1999). Very little study has been done on hardhead or

Sacramento pikeminnow. The lower number of parasite species recorded for hardhead and Sacramento pikeminnow compared to other cyprinids can be also in part explained by the dearth of parasite studies on hardhead and Sacramento pikeminnow.

The scope of this study was intentionally broad, in order to record as many types of parasites inhabiting hardhead and Sacramento pikeminnow as possible.

Unfortunately, the broadness of the study and the necessity of studying as many fish as possible in a short amount of time made it impossible to identify to species all the parasites found. Some parasites, like Trichodina species or

Myxobolus species, must be studied and measured while alive in order to identify to species. Myxobolus species usually also require genetics work to identify to species. Though fungi were found on some fish during necropsy, fungi were not included in this study. Bacteria were also excluded, though one hardhead had a lesion which was apparently caused by Aeromonas hydrophila.

This study focused on the parasite fauna of hardhead and Sacramento pikeminnow. However, it can also serve as a starting point for future ecological studies. In California, many rivers have been dramatically altered in the last 150 years (Mount 1995). California native fishes have borne the brunt of these dramatic changes and many are on the decline (Moyle et al. 1995). Presumably, these changes have also affected parasite distribution and ecological roles.

Although the work of identifying the parasite fauna of California native fishes should continue and is vitally needed, studies of the roles these parasites play in the life histories of fishes should also be undertaken.

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