Cyclops Vernalis Research Articles

Effect of nutritional quality of rotifers and copepods on sea bream (Sparus aurata) fry fish productivity

The present study aims to evaluate the effects of zooplankton rotifers and copepods on sea bream Sparus aurata fry fish productivity concerning their growth performance, production, and feeding utilization. Two hundred seventy fry of the sea bream (Sparus aurata) with a mean body weight of 0.11±0.01 g were collected from fish hatchery, Alexandria, Egypt and transported to the fish rearing unit in El-Max Research Station, National Institute of Oceanography and Fishers (NIOF), Alexandria, Egypt and maintained under standard laboratory conditions. Fry fish were divided into 3 experimental groups, 120 fish each. The feeding regime of experimental group was: group 1 (T1) fed natural rotifer diet with 20% commercial diet, group 2 (T2) fed natural copepod diet with 20% commercial diet, group 3 (T3) fed natural rotifer and copepod with 20% commercial diet. The feeding was provided four times a day (8.00 &10:00 am and 12.00 & 2:00pm) at a rate of 15% of the live body weight of the fish. The present results revealed that the environmental factors: temperatures (20°C, 25°C, 30°C) and salinities (20 ppt, 25 ppt, 30 ppt) significantly affect the total number and the growth performance of rotifers (Brachionus plicatilis) and copepods (Cyclops vernalis). Additionally mixing feeding (rotifers with copepods) resulted in significant increase the carbohydrates and lipids percentage in fry fish comparing to feeding with diet

Green-synthesised nanoparticles from Melia azedarach seeds and the cyclopoid crustacean Cyclops vernalis: an eco-friendly route to control the malaria vector Anopheles stephensi?

The impact of green-synthesised mosquitocidal nanoparticles on non-target aquatic predators is poorly studied. In this research, we proposed a single-step method to synthesise silver nanoparticles (Ag NP) using the seed extract of Melia azedarach. Ag NP were characterised using a variety of biophysical methods, including UV–vis spectrophotometry, scanning electron microscopy, energy-dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy. In laboratory assays on Anopheles stephensi, Ag NP showed LC50 ranging from 2.897 (I instar larvae) to 14.548 ppm (pupae). In the field, the application of Ag NP (10 × LC50) lead to complete elimination of larval populations after 72 h. The application of Ag NP in the aquatic environment did not show negative adverse effects on predatory efficiency of the mosquito natural enemy Cyclops vernalis. Overall, this study highlights the concrete possibility to employ M. azedarach-synthesised Ag NP on young instars of malaria vectors.

A New Toxicity Test Using the Freshwater Copepod Cyclops vernalis.

The cladocerans Ceriodaphnia dubia and Daphnia magna are widely used in environmental toxicity testing and the test methodologies for these species are well developed. However, copepods are a much more abundant contributor to zooplankton in many lakes, but they are not routinely used in toxicity tests. Therefore, we propose toxicity test methods for the freshwater copepod, Cyclops vernalis assessing effects on its survival and growth. A case study is presented in which the proposed test was performed with a range of concentrations of total dissolved solids (TDS) and used as part of a test battery to develop a site-specific water quality objective. C. vernalis was less sensitive to TDS compared to D. magna and C. dubia, but similarly sensitive to an alga, a diatom, a rotifer, a chironomid, and two fish species. No adverse effects were observed on survival or growth of C. vernalis at TDS concentrations up to 1500 mg/L.

Novel Praziquantel Treatment Regime for Controlling Asian Tapeworm Infections in Pond‐Reared Fish

AbstractThe Asian tapeworm Bothriocephalus achelognathii is an intestinal fish parasite that is nonnative to but widespread throughout the southwestern United States. Praziquantel is an anthelminthic drug commonly used to treat fish for Asian tapeworm; however, it does not kill tapeworm eggs, so the water in ponds used for fish rearing must be exchanged after treatment. Our objective was to determine whether a system containing both an intermediate copepod host and a definitive fish host for Asian tapeworm could be treated without exchanging the water by using a follow‐up treatment for any tapeworms that developed from eggs released before or during the first treatment. Here, we have described a new praziquantel treatment regimen to control Asian tapeworm infections in freshwater‐reared fish. To evaluate the efficacy of this regimen, we stocked 50 red shiners Cyprinella lutrensis and an intermediate copepod host, Cyclops vernalis, into each of six pond mesocosms containing artificial macrophytes, sand, and gravel to simulate natural pools and provide suitable substrate for the copepod's life history. The test fish population had been naturally infected with B. achelognathii and had an initial infection prevalence of 14% and an infection intensity of 2.14 ± 2.19 (mean ± SD) worms per fish. Three mesocosms were treated twice, each with 2.5 mg/L praziquantel; 19 d passed between treatments to allow for possible reinfection to occur. After a 2.5‐month posttreatment period to allow any remaining tapeworms to reestablish themselves, we killed and dissected all of the remaining fish. No worms were found in treated fish; however, the control group had an infection prevalence of 18 ± 6% and an infection intensity of 3.45 ± 2.1 worms per fish. Based on these results, we concluded that the praziquantel treatment regime administered was efficacious and suggest testing it on a larger scale. We caution that praziquantel has not been approved by the U.S. Food and Drug Administration for use on fish but can be used legally in some situations.

Morphology and development of Philometra cylindracea (Ward and Magath, 1916) (Nematoda: Philometridae).

A description of the male and a redescription of the female of philometra cylindracea, a parasite of yellow perch (Perca flavescens), are presented. Philometra cylindracea has a one-year development cycle starting as infective larvae in June and becoming mature, larvigerous worms at the end of next June. Cyclops vernalis was found to be a suitable intermediate host under experimental conditions;

Mortality of Fish Larvae Exposed to Varying Concentrations of Cyclopoid Copepods

AbstractCyclopoid copepods can prey on freshwater fish larvae. The magnitude of predation is related to the size and concentrations of the cyclopoid copepods and the size of the fish larva; it is also likely to be specific to certain species. We studied 5‐d‐old larvae of sunshine bass (female white bass Morone chrysops × male striped bass M. saxatilis), golden shiner Notemigonus crysoleucas, fathead minnow Pimephales promelas, and goldfish Carassius auratus in four separate experiments. Larvae were stocked at 20/L into 2 L of water containing various concentrations of the cyclopoid copepods Cyclops vernalis and Mesocyclops vericans to ascertain the effect of predation on mortality. We also compared predation rates observed in this study with rates predicted by an empirical model of crustacean predation on fish larvae from the literature. Sunshine bass alone were susceptible to predation mortality at the cyclopoid copepod concentrations used in this study. Mortality at 400 cyclopoids/L was significantly higher than mortality at 0–100 cyclopoids/ L. Mortality at 500 cyclopoids/L was significantly greater than mortality at any other treatment concentration. The observed predation rates were much lower than the predation rates predicted by the model. Stocking sunshine bass larvae at 4.11 mm total length or larger into ponds with fewer than 300 cyclopoids/L probably represents a low risk of predation. Golden shiners, fathead minnow, and goldfish larger than 5 mm total length that are stocked in ponds with fewer than 500 cyclopoids/L would also probably experience little cyclopoid copepod predation.

Zooplankton community response to reservoir aging

Changes in zooplankton diversity and density in response to reservoir aging in Pawnee Reservoir were investigated. Zooplankton samples collected from April 1992 through April 1993, were compared to a similar study conducted after initial impoundment by Helzer (1971), in 1968–1970. Since this initial study, increases in turbidity and resulting changes in biotic interactions significantly altered the zooplankton community. A significant increase in total zooplankton density and a decrease in species richness were observed between study periods. Density increased from 24.6 to 95.4 individuals L−1, while the number of taxa declined from fourteen to ten. During this time period, Cyclops vernalis became the dominant zooplankter in the reservoir. The density of this predatory copepod increased significantly, from ≤ 0.1 l−1 in 1968–1970, to 44.3 l−1 in 1992–1993, which accounted for most of the increase in total zooplankton density. Though a greater spring maximum of another dominant, Bosmina spp. was found during the 1992–1993 study period, the annual density of this cladoceran was not significantly different between study periods. Similar trends for Daphnia ambigua and D. parvula were also observed, as greater spring maxima levels were attained, however overall annual densities were not significantly different. The dominance of C. vernalis (46% of annual density) and Bosmina spp. (33%), indicate that these two zooplankters were tolerant of changes in physical conditions resulting from reservoir aging and biotic interactions that followed in the reservoir during the 22 years between study periods.

Changes in the Zooplankton of Onondaga Lake: Causes and Implications

ABSTRACT The zooplankton assemblage of ionically polluted, culturally eutrophic Onondaga Lake was monitored over the 1979–1989 interval, and compared to surveys conducted in 1968 and 1978. A major shift in the assemblage was apparent by 1987, soon after the closure (1986) of an industrial discharger of ionic (Cl; Na+ and Ca2+) waste. Species richness increased from 8 to 18 common species, and more efficient grazers, large-bodied cladocera and the calanoid copepod Diaptomus sitihides, became dominants. Until 1987, a single cyclopoid copepod, Cyclops vernalis, was the dominant component of zooplankton biomass. The most likely cause for the shift in the zooplankton assemblage of the lake is the reduction in salinity, and attendant precipitation of calcium carbonate, associated with the closure of the industry. Improved clarity in the lake, manifested largely as intervals of dramatic increases described as ‘clearing events’, observed annually since 1987, has been attributed to die shift to more efficient grazers. The increased grazing pressure, particularly from large daphnids, may also be responsible for the return of late summer nuisance blooms of filamentous cyanobacteria, not observed in the lake since the early 1970s.

Capture Probabilities of Lake Superior Zooplankton by an Obligate Planktivorous Fish—The Lake Herring

–Lake herring Coregonus artedi were videotaped while feeding separately on seven different zooplankton taxa. If a fish reacted to a prey item, I observed whether the prey item entered the buccal cavity of the fish. Copepods were captured at a lower percentage of the time (mean = 48.9%) than were cladocerans (mean = 86.7%). Limnocalanus macrurus, a large copepod, was captured less frequently (30%) than smaller copepods such as Diaptomus sicilis (42.5%), Cyclops vernalis (57.5%), and diaptomid copepodids (65%). Daphnia galeata mendotae were captured less frequently (80%) than smaller cladocerans such as juvenile daphnids (87.5%) or Bosmina longirostris (92.5%). The differences between copepods and cladocerans and sizes of each likely result from differential swimming strengths and behaviors of these various taxa. These results confirm observations from other planktivores that the evasive ability of zooplankton greatly reduces the successful completion of the planktivory process (encounter, attack, capture, ingestion). Additionally, the planktivory process should be examined in its entirety because my results are counterintuitive to those expected from classical size-selective planktivory.

Predation by Cyclops vernalis on Florida Largemouth Bass and Fountain Darter Larvae

Abstract Swim-up Florida largemouth bass (Micropterus salmoides floridanus) were held in 1 L of water with the following combinations of zooplankton: 400 mixed cladocerans, 0 Cyclops vernalis; 200 mixed cladocerans, 200 C. vernalis; and 0 cladocerans, 400 C. vernalis. After 24 h, mean survival percentages for Florida largemouth bass were 97, 27, and 7%, respectively. Larval fountain darters (Etheostoma fonticola) were tested similarly; after 24 h, 100% of the fish combined with cladocerans only were alive, but no larvae survived either treatment containing C. vernalis.

Zooplankton Grazing in a Potomac River Cyanobacteria Bloom

During summer, bloom-forming cyanobacteria, including Anacystis, Aphanizomenon, and Microcystis aeruginosa, dominate tidal-fresh waters of the upper Potomac River estuary with densities exceeding 108 cells l−1. In an attempt to determine the importance of these high cyanobacteria densities to planktonic herbivory in the system, short-term grazing experiments were conducted in July and August 1987. Using size-fractionated river phytoplankton assemblages, zooplankton grazing rates were determined for dominant or subdominant planktonic microzooplankton and mesozooplankton feeding on 14C-labeled river assemblages, 14C-labeled river assemblages enriched with unlabeled cyanobacteria, and unlabeled river assemblages enriched with 14C-labeled cyanobacteria. Grazing rates were estimated for the rotifers Polyarthra remata, Hexarthra mira, Asplanchna brightwelli, Brachionus angularis, Epiphanes sp., Trichocerca similis, and the cyclopoid copepod Cyclops vernalis. Neither rotifers nor the copepod grazed heavily on Microcystis. Rotifer grazing rates on labeled cyanobacteria ranged from 4 to 1,650 nl· [individual · h]−1 while copepod rates ranged from undetectable to 135 μl · [copepod · h]−1. Grazing rates on labeled river phytoplankton assemblages were 4–100 times higher than noted for zooplankton feeding on cyanobacteria. The addition of the colonial alga to labeled river phytoplankton assemblages resulted in mixed zooplankton responses, that is, lower and higher grazing rates than observed on river assemblages with no added cyanobacteria. Total zooplankton demand for cyanobacteria and river phytoplankton assemblages was estimated for the study period July–August 1987. Rotifer plus C. vernalis herbivory would have removed 1–5% and 49%, respectively, of the standing stock of the two autotroph pools each day. Literature-derived clearance rates for Bosmina indicate, however, that herbivory by this cladoceran could increase demand to 24% and 60%, respectively, in bloom and nonbloom assemblages. These data suggest that the majority of cyanobacterial production remains ungrazed and may be transported to the lower estuary for salinity-induced aggregation and sedimentation.

A Lakewide Comparison of Zooplankton Biomass and Its Species Composition in Lake Erie, 1983–87

From 1983 to 1987, 118 species representing 53 genera from the Calanoida, Cladocera, Cyclopoida, Rotifera, and Harpacticoida comprised the offshore zooplankton community of Lake Erie. Twenty-eight common species plus their juvenile stages accounted for 94.4% of the total biomass and 92.5% of the total abundance. The eutrophic indicators Brachionus caudatus, B. calyciflorus, B. angularis, Filinia longiseta, Trichocerca multicrinis, and Trichocerca cylindrica had abundances restricted to or significantly higher in the western basin. Between 1983 and 1987, essentially smaller species ( Daphnia galeata mendotae, Daphnia retrocurva, Eubosmina coregoni, Bosmina longirostris, and Diaphanosoma leuchtenbergianum) were dominant as in 1948 and 1970. In 1984 a large cladoceran new to Lake Erie, Daphnia pulicaria (mean = 755 individuals/m 3, maximum abundance of 3,752/m 3), became prevalent. Another cladoceran, Bythotrephes cederstroemi, was first observed in Lake Erie in 1985 and continued to be present in 1986 and 1987. Cyclops vernalis, present throughout the lake in 1967, was observed only in the western basin during 1983 to 1987 similar to the distribution in the 1930s. Rotifer composition in 1967 and the 1983-87 period was similar. Cladocera abundance during the 1983-87 period was comparable to abundances observed in the’30s and’40s. Zooplankton abundance and biomass decreased from the western basin to the eastern basin except in 1985. This decrease correlated with the decrease in phytoplankton biomass (r = 0.81).

Effects of Eubothrium salvelini (Cestoda) on the behaviour of Cyclops vernalis (Copepoda) and its susceptibility to fish predators

SUMMARYTo facilitate the completion of their life-cycle, many helminth parasites have evolved the ability to manipulate the behaviour of their intermediate host in order to make it more likely to be eaten by the parasite's definitive host. Here, we determined whether the cestode Eubothrium salvelini modifies the behaviour of its intermediate host, the copepod Cyclops vernalis, and makes it more susceptible to predation by brook trout, Salvelinus fontinalis, the parasite's final host. Following the experimental infection of copepods, the spontaneous activity of infected and control subjects was quantified weekly. In addition, we regularly quantified predation by individual brook trout fry on known numbers of infected and control copepods. At approximately the time when the cestode larvae became infective to fish (2–3 weeks following infection), the infected copepods started to swim more actively than uninfected controls. Also at that time, infected individuals became more likely to be captured by fish than uninfected ones. Copepod size and intensity of infection had no significant effect on their behaviour or their risk of being eaten by fish. Thus cestode- induced changes in copepod swimming activity can lead to infected copepods becoming highly vulnerable to fish predators, and may have resulted from selection on the parasite to increase its transmission success

Growth and Food Selection of Intensively Cultured Largemouth Bass Fry

Abstract Six genera of invertebrates were fed to largemouth bass fry (Micropterus salmoides) for 25 d after the fish hatched to document the growth rate of the fish and to determine the genera and sizes of invertebrates selected by the fish during their early development. The fry increased in mean total length from 6.5 mm on the first day of feeding to 29.8 mm on day 25 (mean daily length gain, 0.93 mm). The rotifer, Branchionus sp., was eaten day and night during the first 4 d. The copepod, Cyclops vernalis, was selected during days 1–14; selection was stronger during the day than at night. The cladocerans, Daphnia pulex and D. magna, were selected and were the most abundantly consumed organisms on days 15–25. As the fry grew, they selected progressively larger D. pulex and D. magna. The cladoceran, Moina brachiata, was eaten in proportion to its relative abundance throughout the study.

Feeding Behavior of Intensively Cultured Bluegill Fry

Abstract Feeding preferences of bluegill (Lepomis macrochirus) fry for four zooplankton genera and cladoceran egg cases collected from a municipal sewage lagoon were examined. Bluegill fry ranged in length from 8.0 to 10.5 mm total length at stocking and were reared for 30 d. Gut contents of 1,440 fry were collected during daytime and nighttime hours. Diet composition was evaluated by the linear food selection index. Bluegill fry preferred Cyclops vernalis and Moina brachiata and consistently avoided cladoceran egg cases and Potamocypris spp. The mean length of prey species selected increased curvilinearly with mean length of fry. No significant diel differences in prey species and size selection were found. The number of prey organisms consumed by bluegill fry increased linearly with mean length of fish. The fry ingested significantly fewer organisms at night than during the day.

Species Composition and Seasonal Succession of the Zooplankton Community of Eutrophic Lahontan Reservoir, Nevada

Species Composition and Seasonal Succession of the Zooplankton Community of Eutrophic Lahontan Reservoir, Nevada

Prey Selection of Walleye Fry in an Experimental System

Abstract Five genera of invertebrates were fed to walleyes (Stizostedion vitreum vitreum) for 51 days after hatching to document the genera and sizes of invertebrates selected by the fish during their early development. The cladoceran Moina brachiata was selected for; the copepod Cyclops vernalis was initially eaten in the same proportion as available, but later selected for when M. brachiata was not available; and the cladocerans Daphnia magna and D. pulex and the rotifer Asplanchna sieboldi were selected against. The rotifer Brachionus sp. was not eaten. As the walleyes grew they selected for progressively larger cladocerans but not for progressively larger C. vernalis. Significantly more organisms were eaten by walleyes collected at 1100 hours than by those collected at 2300 hours initially, but significantly fewer after 15 days of feeding.

Inviability of Interspecific Hybrids in theCoelomomyces DodgeiComplex

Studies of experimentally produced hybrids of Coelomomyces dodgei and C. punctatus demonstrate that all stages of the F1 sporophytic phase are functional but that the F1 gametophyte is inviable. Hybrid zygotes formed in reciprocal crosses of gametes of these species are infective for mosquito larvae within which they form viable sporophytes and resting sporangia. The surface structure of these sporangia, as well as the cleavage and dehiscence patterns, are similar to those of the parental species. Additionally, meiospores produced by hybrid sporangia appear normal in that they are highly motile and capable of recognizing and encysting upon the alternate copepod host, Cyclops vernalis. However, in contrast to parental species, encystment does not result in production of a functional gametophyte. These results provide substantial evidence that C. dodgei and C. punctatus, though closely related, are reproductively isolated and, therefore, are distinct and valid species. The possible use of experimental hybrids to study the systematics of other species and varieties of the genus Coelomomyces is discussed.

Inviability of Interspecific Hybrids in the Coelomomyces dodgei Complex

Studies of experimentally produced hybrids of Coelomomyces dodgei and C. punctatus demonstrate that all stages of the F1 sporophytic phase are functional but that the F1 gametophyte is inviable. Hybrid zygotes formed in reciprocal crosses of gametes of these species are infective for mosquito larvae within which they form viable sporophytes and resting sporangia. The surface structure of these sporangia, as well as the cleavage and dehiscence patterns, are similar to those of the parental species. Additionally, meiospores produced by hybrid sporangia appear normal in that they are highly motile and capable of recognizing and encysting upon the alternate copepod host, Cyclops vernalis. However, in contrast to parental species, encystment does not result in production of a functional gametophyte. These results provide substantial evidence that C. dodgei and C. punctatus, though closely related, are reproductively isolated and, therefore, are distinct and valid species. The possible use of experimental hybrids to study the systematics of other species and varieties of the genus Coelomomyces is discussed.

Prey utilization by Chaoborus punctipennis Say in a small, eutrophic reservoir

Prey selection by 2nd-, 3rd-, and 4th-instar larvae of Chaoborus punctipennis was evaluated by comparing larval crop contents to the species structure of the zooplankton community in a small, eutrophic lake. The rotifers, Brachionus caudatus and Trichocerca similis, were positively selected by and comprised most of the diet of 2nd- and 3rd-instar larvae. Rotifers comprised 67% of all prey items identified in the crops of even 4th-instar larvae. Whereas 2nd-and 3rd-instar larvae selected the two rotifers with equalfrequency, 4th-instar larvae selected Trichocerca significantly more frequently than they did Brachionus. Although copepods comprised only 8% of all prey identified in 3rd-instar crops, they comprised 33% of the crop contents of 4th-instar larvae. Both 3rd and 4th instars exhibited a positive electivity for Cyclops vernalis significantly more frequently than for Diaptomus pallidus. We conclude that the larvae of Chaoborus punctipennis can, and do, select between Trichocerca and Brachionus and between Cyclops and Diaptomus.