The effects of 17β-oestradiol, testosterone and tamoxifen on the development of papillomata in Catostomus commersoni

Testosterone induced papillomata in 85% (11/13) of initially non-papillomatous white suckers Catostomus commersoni and increased papillomata growth in 100% (16/16) of initially papillomatous suckers. 17β-oestradiol induced papillomata in 83% (10/12) of initially nonpapillomatous suckers and increased papillomata growth in 100% (16/16) of initially papillomatous suckers. Less than 29% (4/14) of white suckers injected with tamoxifen developed papillomata, while complete papillomata regression was observed in 71% (10/14) of initially papillomatous suckers. In control groups 59% (27/46) of suckers either retained or developed papillomata and 27% (6/24) of suckers exhibited tumour regression. Protein kinase C (PKC) activity was significantly depressed and ornithine decarboxylase (ODC) activity was significantly elevated in steroid-treated papillomata v. normal lip epidermis. ODC activity was significantly depressed in tamoxifen-injected, regressing papillomata. There were no significant differences in plasma oestrogen and testosterone levels between papillomatous and nonpapillomatous female fish from a site contaminated with persistent organic chemicals and an uncontaminated reference site. Similarly, no significant differences in testosterone and 11-ketotestosterone levels were observed between papillomatous and non-papillomatous male fish.     

The prevalence of Trypanosoma catostomi in white sucker (Catostomus commersoni) from southern Ontario.

During the summer of 1975, 285 white suckers (Catostomus commersoni) from 10 localities in southern Ontario were examined for trypanosomes. Trypanosoma catostomi Daly and DeGiusti, 1971 was found in the blood of 11.6% of the fish examined using the haematocrit centrifugation technique. Infected juvenile fish (33%) and infected adult fish (4%) were found in 6 of 10 locations.     

Ligulosis associated with mortality in largescale suckers

Investigations of a fish kill at an irrigation reservoir in the Deschutes River basin, Oregon, documented at least 153 dead largescale suckers Catostomus macrocheilus , all heavily infected with large Ligula intestinalis (Cestoda). Moribund fish nearshore were similarly infected, with no evidence of secondary disease or infection. Morbidity and mortality in all cases was probably due to severe mechanical damage to internal host organs resulting from infection with multiple, large L. intestinalis . The pathology of L. intestinalis documented in largescale sucker in this study contrasts sharply with previous accounts and may represent a new and emerging disease for largescale suckers.     

Metacercariae of Diplostomum spathaceum in the eyes of fishes from Yellowstone Lake, Wyoming

Fish were collected from Yellowstone Lake, Wyoming (USA). Metacercariae of Diplostomum spathaceum was found in the lens of 11 of 12 longnose suckers (Catostomus catostomus). The mean number of metacercariae per sucker was 59 and the average age of the fish was 11.6 yr. There was no correlation between age and intensity of parasites (r = 0.24). Of 10 cutthroat trout (Salmo clarki) examined, there were metacercariae present in six. The metacercariae were found outside of the lens tissue in the trout; they occurred in the vitreous humor and the retina. These may be a different species from those found in the suckers.     

Structural changes in gills of Lost River suckers exposed to elevated pH and ammonia concentrations

The Lost River sucker (Deltistes luxatus) is a federally listed, endangered fish that occurs primarily in Upper Klamath Lake-a hypereutrophic lake in southern Oregon, USA. A decline of the sucker population in the lake over the past few decades has been partly attributed to adverse water quality conditions, including elevated pH and ammonia concentrations that occur during summer cyanobacterial blooms. We quantitatively analyzed structural changes in gills of larval Lost River suckers after they were exposed to elevated pH and ammonia concentrations for 30 d. Exposure to pH as high as 10 caused no observed structural changes. However, lamellar thickness and O(2) diffusion distance increased significantly (P<0.05) at ammonia concentrations that did not significantly decrease survival, growth, whole-body ion concentrations, or swimming performance. Additionally, we qualitatively observed increases in the frequency of hyperplasic and hypertrophic mucous cells, tissue damage, epithelial lifting, and infiltration of white blood cells into paracellular lymphatic spaces at the highest sublethal ammonia concentration. These observed gill changes typically indicate compromised respiratory and ionoregulatory capacity, although such effects were not manifested in the assays we performed. Regardless, these structural gill changes appear to be a more sensitive indicator of exposure to elevated ammonia concentrations than are more traditional sublethal indices. Therefore, gill histopathology might be a relevant early-warning monitoring tool of the health of Lost River suckers in Upper Klamath Lake, and other species in similar eutrophic systems.     

The life cycle of Asymphylodora perccotti sp. n. (Trematoda: Lissorchiidae) in the Russian Southern Far East

Specimens of Asymphylodora perccotti sp. n. (Trematoda: Lissorchidae) were found in the esophagus of the freshwater fish Perccottus glenii (Odobantidae) taken from the Bolshaya Ussurka River Basin (Primorsky Region, Russian Southern Far East). The first intermediate host of this trematode is a gastropod, Parafossarulus manchouricus, and the secondary hosts are the same mollusk and Boreoelona ussuriensis. Specimens of the new species are similar to A. amnicolae identified by Stunkard in 1959, but the mature worms have larger suckers and shorter ceca. The cercariae of these species are distinguished by body, suckers and pharynx size. These organs in A. perccotti sp. n. are more than one-third larger than what is observed in A. amnicolae. In addition, the new species lacks the capacity for progenesis. Finally, the new species is unusual in that it resides in the fish esophagus instead of the intestine, as is common for most Asymphylodora species. Partial ribosomal DNA sequences and phylogenetic reconstruction sequence data indicate that these worms represent a new digenean species.     

Postglacial dispersal of longnose suckers, Catostomus catostomus, in the Mackenzie and Yukon Drainages

The role played by stream transfers and reversals in the postglacial dispersal of fish populations in the Yukon and Mackenzie River drainages of Canada was analysed using genetic and meristic data from longnose sucker (Catostomus catostomus Forrester) populations. The hypothesis the suckers dispersed from the Yukon River into the Mackenzie River via the Peel River was evaluated. Meristic data (gill rakers and lateral line scales) were uninformative for this analysis. Genetic affinity between the Yukon River and upper Peel River populations, and between Mackenzie and lower Peel River populations is suggested by transferrin allele frequencies. These affinities support the view that longnose suckers inhabiting the middle and upper regions of the Peel River are derived from Beringian and Mississippian ancestors, while suckers in the lower Peel are descended from Mississippian stock. Evidence for dispersal by way of the Eagle River was not found. Affinities of sucker populations in other river systems in the region are also described.     

Shape variation in a benthic stream fish across flow regimes

Evolution of fish body shapes in flowing and non-flowing waters have been examined for several species. Flowing water can select for fish body shapes that increase steady swimming efficiency, whereas non-flowing water can favor shapes that increase unsteady swimming efficiency. Benthic stream fishes often use areas near the substrate that exhibit reduced or turbulent flow, thus it is unclear which swimming forms would be favored in such environments, and how shape might change across flow regimes. To test the relationship between fish body shape and flow regime in a benthic stream fish, we used geometric morphometric techniques to characterize lateral body shape in mountain sucker (Catostomus platyrhynchus) across flow rates, using stream gradient as an indicator of stream flow. Mountain suckers from low-flow environments were more streamlined, consistent with steady swimming body shapes, whereas mountain suckers from high flows had deeper bodies, consistent with unsteady swimming body shapes. In addition, smaller individuals tended to have more robust body shapes. These patterns are opposite to those predicted for stream fishes in the mid-water column. The benthic stream environment represents a distinct selective environment for fish shape that does not appear to conform to the simple dichotomy of flowing versus non-flowing water.     

Feeding,growth, and particle-size-conversion efficiency in white sucker larvae and young common shiners

Synopsis Instantaneous feeding, assimilation, and growth rates for white sucker larvae and young common shiners and guppies (1–2 mg initial dry weight) were measured. Food consisted of natural zooplankton. Linear relationships were obtained between growth and feeding rates for instantaneous feeding rates up to 0.5 mg^-1 day^-1. Maximum gross conversion efficiencies (K₁) were 0.26, 0.31, and 0.24 for suckers, shiners, and guppies respectively. Particle-size-conversion efficiency (-log K₁ per log predator-prey size ratio) was 0.15 for suckers, 0.14 for shiners, and 0.18 for guppies. These values are lower than most available estimates of particle-size-conversion efficiency for carnivorous zooplankton and piscivorous fish, indicating that young planktivorous fish are among the most efficient predators at transferring biomass up the biomass size spectrum in aquatic ecosystems.     

Development of the escape response in teleost fishes: do ontogenetic changes enable improved performance?

Teleost fishes typically first encounter the environment as free-swimming embryos or larvae. Larvae are morphologically distinct from adults, and major anatomical structures are unformed. Thus, larvae undergo a series of dramatic morphological changes until they reach adult morphology (but are reproductively immature) and are considered juveniles. Free-swimming embryos and larvae are able to perform a C-start, an effective escape response that is used evade predators. However, escape response performance improves during early development: as young fish grow, they swim faster (length-specific maximum velocity increases) and perform the escape more rapidly (time to complete the behavior decreases). These improvements cease when fish become juveniles, although absolute swimming velocity (m s(-1)) continues to increase. We use studies of escape behavior and ontogeny in California halibut (Paralichthys californicus), rainbow trout (Oncorhynchus mykiss), and razorback suckers (Xyrauchen texanus) to test the hypothesis that specific morphological changes improve escape performance. We suggest that formation of the caudal fin improves energy transfer to the water and therefore increases thrust production and swimming velocity. In addition, changes to the axial skeleton during the larval period produce increased axial stiffness, which in turn allows the production of a more rapid and effective escape response. Because escape performance improves as adult morphology develops, fish that enter the environment in an advanced stage of development (i.e., those with direct development) should have a greater ability to evade predators than do fish that enter the environment at an early stage of development (i.e., those with indirect development).     

Survival and recruitment of seedlings and suckers of trees and shrubs of the Australian arid zone following habitat management and the outbreak of Rabbit Calicivirus Disease (RCD)

Abstract Recruitment in many shrub and tree species in arid Australia is limited by domestic and feral animal grazing. The outbreak of Rabbit Calicivirus Disease (RCD or RHD) in late 1995 at Kinchega National Park (NP) in arid western NSW, Australia, coincided with intensified warren ripping and other rabbit (Oryctolagus cuniculus) control efforts. We monitored changes in rabbit numbers in response to these factors using spotlight counts and dung‐pellet counts. Rabbit populations declined initially, and were low for the remainder of the study. To assess the impact of rabbit control on vegetation, we examined whether recruitment of seedlings or vegetative suckers was occurring at Kinchega NP, following the arrival of RCD; how long such recruits were likely to survive under current grazing pressures; and whether the magnitude of current seedling and vegetative sucker recruitment and survival is greater than available data prior to RCD and extensive warren control. We followed the survival of individual seedlings and newly emerged suckers of six shrub or tree species, most of which are considered to be at risk of local decline. Three levels of caging were used to exclude all mammalian grazers; all mammalian grazers except rabbits; and no mammalian grazers. Pooled cohorts of seedlings and suckers were analysed using failure‐time analyses. During the course of the study, suckering was observed in four species (Acacia carneorum, Alectryon oleifolius, Casuarina pauper and Santalum acuminatum), with seedlings observed in the other two species (Dodonaea viscosa and Acacia ligulata). Survival of suckers of some species was slightly greater than pre‐RCD estimates, but in general, a pattern of little or nil recruitment is likely in suckers exposed to rabbits or to all grazing mammals. Seedling survival was particularly low regardless of the level of exclusion, largely due to desiccation. Reduction of grazing impacts may only allow recruitment into populations of species reliant on seedlings under more favourable climatic circumstances than experienced in this study, while the probability of successful recruitment into populations of suckering species in western NSW continues to be low even at very low rabbit densities.     

Physiological stress response of Mountain Whitefish (<Emphasis Type="Italic">Prosopium williamsoni</Emphasis>) and White Sucker (<Emphasis Type="Italic">Catostomus commersoni)</Emphasis> sampled along a gradient of temperature and agrichemicals in the Oldman River,Alberta

Species differences in tolerance to environmental stressors can contribute to differences in species distribution and abundance along river gradients. Climate change and intensive agriculture are likely to have major effects on fish populations in temperate zones, yet understanding of the interactions between temperature and chemical stressors on fish physiology is limited. The objective of this study was to compare the stress responses of the Mountain Whitefish, (Prosopium williamsoni, a cold-water fish) and White Sucker (Catostomus commersoni, a cool-water fish), along a temperature and pesticide gradient in the Oldman River, Southern Alberta in spring and summer. Fish were seined, placed into an enclosure, and plasma cortisol, glucose, liver glycogen, and condition factor were measured. Plasma acetylcholinesterase (AChE) activity was used as an indicator of exposure to organophosphate and carbamates pesticides. Whitefish had lower plasma AChE activity and lower liver glycogen reserves compared to suckers at all sites and all sampling times but the differences in plasma cortisol were not species-specific and there were no differences in plasma glucose levels, except at one site. Plasma cortisol increased, and plasma glucose decreased along a downstream river gradient in whitefish in both spring and summer; in sucker only plasma cortisol fluctuated and only in the summer. Liver glycogen decreased along the river gradient in both species at both seasons. Our study detected important species-specific differences in AChE activities and responses of the physiological stress axis, suggesting that whitefish are more sensitive to temperature and pesticide stress than suckers.     

Regulation of protein kinase C and ornithine decarboxylase in the epidermis of juvenile white suckers (Catostomus commersoni) by 12-O-tetradecanoylphorbol-13-acetate, 17 α-ethinylestradiol and testosterone

This study was designed to investigate whether potent regulators of mammalian protein kinase C (PKC) and ornithine decarboxylase (ODC) activity also regulate epidermal PKC and ODC activity in fish. Juvenile white suckers (Catostomus commersoni) were given single or multiple subdermal injections of testosterone, 17α-ethinylestradiol or 12-O-tetradeconylphorbol-13-acetate (TPA) dissolved in sunflower oil. Sequential activation of epidermal PKC and ODC was observed in single injection protocols. Maximal PKC activity occurred at 12–48 hr post-injection, with a corresponding increase in ODC activity in the 12–48 hr immediately following this event. In the multiple injection protocols, PKC activity was almost completely depressed after 1 week of injections, during which ODC activity was stimulated 2- to 5-fold, indicating possible differential activation of these two enzymes. Multiple injections of testosterone, 17α-ethinylestradiol and TPA induced histologically distinct epidermal hyperplasia in suckers, although this did not occur in single injection treatments. The mammalian isozymes of PKC are known to be dependent on Ca²⁺ and phospholipid for optimum activity. This study demonstrated that the fish isozyme of PKC is also Ca²⁺ and phospholipid dependent. Our results indicate that PKC and ODC may be good biochemical markers for neoplasia and hyperplasia in fish.     

Historic and recent age structure and growth of endangered Lost River and shortnose suckers in Upper Klamath Lake, Oregon

Seventy-four lapilli from Lost River suckers captured in Upper Klamath Lake in 1970 during a snag fishery on spawning adults and 192 lapilli from adults sacrificed from 2001–2006 were examined to determine age and growth parameters; lapilli from 165 shortnose suckers sacrificed from Upper Klamath Lake from 2001–2006 were also examined. Relative marginal distance analyses indicated that growth marks were annuli and formed in December–January. Lost River suckers from the historic collection were aged to 57 years, while Lost River and shortnose suckers from the recent collection were aged to 40 years and 24 years, respectively. Larger and older Lost River suckers were represented in the historic collection compared to the recent collection. Uncoupling of otolith length and fish length in Lost River suckers as well as a large spread in the predicted age- at-size for shortnose suckers precluded the ability to back-calculate size-at-age. Likelihood ratio tests indicated the growth model parameters were significantly different at both the sex and collection level. Growth in body length for both species appeared determinate in that growth was rapid until maturity, and then slowed over several years until growth in length was nearly nonexistent; a 650–700 mm Lost River sucker could be between 14 and 57 years old, while a 460 mm shortnose sucker could range from 12–24 years old. In contrast, while growth in body length slowed for both species, body mass continued to increase. This growth strategy, which is also found in other western lake suckers, may allow for more energy to be utilized for reproduction and help populations persist in spite of years of limited recruitment or recruitment failure.     

Growth chronologies of white sucker, Catostomuscommersoni, and lake trout, Salvelinusnamaycush: a comparison among lakes and between trophic levels

A growth chronology index was used to determine whether changes in ecosystem structure and function in lakes could be associated with fish growth histories. Growth chronologies were compared for white suckers, Catostomus commersoni, from Little Moose (oligotrophic), Oneida (eutrophic), and Cayuga (mesotrophic) lakes (New York) from opercular bone growth increments, and for lake trout, Salvelinus namaycush, from Little Moose Lake using otolith growth. The longevity of these species allowed the development of chronologies from 17 to 33 years in length using only contemporary collections. We used these chronologies to examine whether fish growth histories could be used as an index for ecosystem-scale changes. Specifically, we examined whether zebra mussel, Dreissena polymorpha, invasion in Oneida and Cayuga lakes in the early 1990s, and treatment of sewage effluent from dwellings around Little Moose Lake beginning during the late 1980s could be detected in white sucker and lake trout growth chronologies. White sucker growth in Oneida and Cayuga Lakes did not differ before and after zebra mussel invasions. Neither white sucker nor lake trout growth chronologies from Little Moose Lake reflect changes in growth expected with reduced productivity levels associated with improved sewage treatment. Growth chronologies of these two species did not detect the ecosystem-scale changes that occurred in the study lakes.     

Effects of malachite green on leucocyte abundance in rainbow trout, Salmo gairdneri (Richardson)

Blood counts from more than 1000 young-of-the-year rainbow trout, Salmo gairdneri (Richardson), were examined to determine if static exposure to malachite green at 1·35,13·5, or 21·0 mg/1 for 25–30 min or 42·0 or 72·0 mg/1 for 5 min caused chronic leucopaenia. The major changes in fish exposed for 25–30 min came during the first 24 h. After an initial lag of 3·4 h, total leucocyte-thrombocyte counts in both treated and control fish rapidly declined. Recovery was essentially complete 1·4 days after exposure, and no leucopaenia was noted after 14 or 28 days. Thrombocytosis developed during the first 24 h in fish exposed to the higher concentrations. Lymphopaenia and neutrophilia also developed, but abated after the 4th post-treatment day. Leucocyte numbers in control and exposed groups were virtually the same by the 14th day. The total leucocyte-thrombocyte counts in fish exposed for 5 min declined after 24 h, but counts were not as depressed as those in fish exposed for 30 min.
Because leucocyte changes similar to those in exposed fish were evident in the controls in both experiments, we believe that the leucocyte changes in rainbow trout exposed to malachite green were a result of a nonspecific vertebrate stress syndrome, rather than of specific leucocytotoxic effect of this chemical.     

Nutrient Subsidies from Iteroparous Fish Migrations Can Enhance Stream Productivity

Migratory animals often transfer nutrients between ecosystems, enhancing productivity in the subsidized system. Most research on nutrient subsidies by migratory fishes has focused on Pacific salmon, whose semelparous life history is unusual among migratory fishes. To test whether iteroparous species can provide ecologically important nutrient inputs to stream ecosystems, we experimentally blocked the migration of suckers (Catostomidae) midway up an oligotrophic tributary of Lake Michigan. Comparing reaches upstream of the barrier to downstream reaches containing thousands of breeding fish, we found that suckers elevated phosphorus and nitrogen concentrations three- to five-fold. Algal accrual was doubled and caddisflies grew 12% larger in subsidized reaches relative to reference reaches. An enclosure experiment demonstrated that caddisflies with access to a fish carcass rapidly became enriched in ¹⁵N and ¹³C, and experimental carcass additions were rapidly colonized by high densities of caddisflies. However, under natural conditions below the experimental barrier, caddisflies became enriched in ¹⁵N but not ¹³C, indicating that fish-derived nutrients entered the stream food web primarily through indirect pathways rather than direct consumption of carcasses or gametes. At pupation, an average of 18% of caddisfly tissue N below the barrier was sucker-derived. In comparison to our focal stream, a reference stream with few suckers showed no seasonal or longitudinal patterns in nutrients and stable isotopes. These results demonstrate that iteroparous fish migrations can spur productivity via nutrient subsidies, despite low mortality rates. Thus, concerns about negative ecosystem-level consequences of blocking migrations of semelparous fishes are also applicable to iteroparous species when migrations are large.     

Acute lethal and sublethal effects of neem leaf extract on the neotropical freshwater fish Prochilodus lineatus

The aim of this study was to determine the toxicity of the aqueous extract of neem leaves, a product extensively used in fish-farms as alternative for the control of fish parasites and fish fry predators, for the neotropical fish Prochilodus lineatus. The 24 h LC(50) of neem leaf extract for juveniles P. lineatus was estimated as 4.8 g L(-1); the fish were then exposed for 24 h to 2.5, 5.0 and 7.5 g L(-1) or only clean water (control). Plasma glucose levels were higher in fish exposed to 2.5 g L(-1) and 5.0 g L(-1) neem extract, relative to control, indicating a typical stress response. Neem extract did not interfere with the osmoregulating capacity of the fish, as their plasma sodium, chloride, total protein and osmolarity did not change. The presence of the biopesticide interfered with the antioxidant defense system of P. lineatus, as there was a decrease in liver catalase activity at all neem concentrations and the detoxifying enzyme glutathione-S-transferase was activated in fish exposed to 5.0 g L(-1). Fish exposed to all neem extract concentrations exhibited damaged gill and kidney tissue. These results indicate that although neem extract is less toxic to P. lineatus than other synthetic insecticides used in fish-farming it does cause functional and morphological changes in this fish species.     

Secondary and tertiary stress responses to BKME exposure in the St. Maurice River fish populations

In the St-Maurice River, Canada, white suckers (Catostomus commersoni) collected at two stationslocated downstream of a bleached kraft mill effluent(BKME) outfall exhibited increased muscle lipidconcentrations relative to upstream reference fish.White suckers collected in a physicochemicallycomparable but uncontaminated river, also demonstratedan increasing trend of lipid accumulation withdistance downstream. The similar general trends inboth rivers may result from a river continuum in whichincreasing loads of nutrients with distance downstreamincrease the energy available to fish.However, the general trends differed in two respects.The gradient of lipid accumulation in the St. MauriceR. was irregular, suggesting a sharply increasednutrient input by BKME. Secondly, in the referenceGatineau river, increased lipid reserves wereaccompanied by increased growth and reproductiveeffort relative to body size. In contrast, increasedgrowth rates in the contaminated St. Maurice River wereaccompanied by a reduced reproductive effort relativeto body size. The failure to translate increasedenergy intake, as indicated by increased musclelipids, into increased reproductive effort suggestsone or more components of BKME have a toxic effect.Accelerated river enrichment contributed by thedischarge of the bleached kraft effluent combined withthe natural river continuum made it difficult toisolate the reproductive effects related to effluentexposure.     

Segregation by species and size classes of rainbow trout,Salmo gairdneri,and Sacramento sucker,Catostomus occidentalis,in three California streams

Synopsis The hypothesis that Sacramento suckers, Catostomus occidentalis, compete with rainbow trout, Salmo gairdneri, for space in streams was examined by measuring microhabitat utilization of both species in three California streams. Two streams were similar in most respects except one contained only trout and one contained trout and a large population of suckers. The third stream, formed by the union of the first two, contained trout and a small population of suckers. The species overlapped in five of the six microhabitat variables measured: maximum depth, mean water column velocity, focal point velocity, surface water velocity, and substrate type. However, the species had strong vertical segregation; there was little overlap between species in focal point depth. Mean focal point velocities were also significantly different. Suckers roamed over and generally remained in contact with the bottom while trout held position in the water column. Microhabitat utilization by trout in the stream without suckers was similar to in the stream with a higher sucker density. Differences in microhabitat utilization by trout between the third stream and the other two was attributed to the larger size of the third stream. Both sucker and trout showed a similar within-species segregation of size classes - fish under 50 mm in length sought shallow water. Size-specific trends indicated ontogenic shifts in resource utilization which reduced overlap within species. These results suggest that competition for space between trout and suckers was not a major factor regulating microhabitat utilization of trout, although the possibility that larger suckers may displace small trout needs further study.