Artemia monica cyst production and recruitment in Mono Lake,California, USA

Annual egg production was determined for Artemia monica in Mono Lake, California, from 1983 to 1987. Annual oviparous (overwintering cyst) production was 3 and 7 million cysts m^–2 yr^–1 in 1986 and 1987, respectively, as measured by in situ sediment traps. Cyst production for the entire five year period was calculated using Artemia census data and inter-brood duration derived from mixolimnetic temperature. These estimates ranged from 2 to 5 million cysts m^–2 yr^–1. This method underestimated annual production by 30%, when compared to estimates using sediment traps. Cyst production was similar during 1983–1986 and showed a significant increase in 1987, which was due primarily to a larger reproductive population later in the year. Recruitment into the adult populations of the following spring ranged between 1.4 to 3.2%. Overall abundance of this generation reflected the patterns in annual cyst production. Compensatory effects must operate on the second generation of each year, since summer populations were similar in all years despite differences in cyst production.     

Limnological control of brine shrimp population dynamics and cyst production in the Great Salt Lake, Utah

In the Great Salt Lake of Utah, the brine shrimp Artemia franciscanaKellogg is an important food resource for birds and they produce dormant cysts that are harvested and used extensively in the aquaculture industry. We analyzed the limnological factors controlling Artemia growth and cyst production over 12 months in 1994 and 1995. Laboratory experiments showed that inter-brood intervals were highly dependent on temperature and slightly on food level. At optimal temperatures and nutritious food, juveniles reached reproductive size within 7 d in the laboratory. In winter when temperatures were less than 3 °C, Artemia were absent from the lake, phytoplankton abundance was high (13 Chl a g l^–1), and the dominant grazers were ciliated protozoans. In the spring, cysts hatched when phytoplankton was abundant (15–30 g Chl a l^–1), and the Artemia grew and produced large clutches of ovoviviparous eggs. Estimated naupliar production from these eggs was 80 l^–1 from April to May. Despite the high production of nauplii, Artemia densities declined to 8 l^–1by June and the growing shrimp population grazed down the phytoplankton resource to <1 g Chl a l^–1. With the depleted phytoplankton food resource during the summer, Artemia growth slowed, lipid indices decreased, clutch sizes declined, and females switched primarily to oviparous cyst production. During the summer, there was limited production of ovoviviparous eggs, and limited recruitment of juveniles, probably due to low food. Although oviparous reproduction began in June, more than 90% of the cysts were produced after July when female densities had declined to 1.5 l^–1, but nearly all of them were producing cysts. Estimated cyst production was 650000 m^–2, or 4.54 × 10⁶ kg dry weight for the entire lake. The reported commercial harvest took 21% of the 1994 cyst production. That harvest had little impact on the subsequent year's population, as Artemia densities were ultimately controlled by algal production in the lake.     

Evaluation of agro-industrial wastes as diets for culture of the fairy shrimpStreptocephalus proboscideus (Frauenfeld, 1873) (Crustacea:Branchiopoda:Anostraca)

Two micronized waste products were evaluated in a closed recirculation system for their suitability to replace a costly die of live algae in the culture of the Sudanese fairy shrimp,Streptocephalus proboscideus. The test population was kept at a density of 50 individuals 1^–1 (sex ratio:1/1). An agricultural waste product (YM20; mixture of pea and corn), and an industrial waste product (POME; Palm Oil Mill Effluent) were fed at two regimes: 0.1 and 0.2mg DW animal^–1 h^–1. The microalgaSelenastrum capricornutum, used as a reference diet at a density of 2.0±0.82 × 10⁵ cells ml^–1, proved adequate in preliminary screening experiments. The effect of the diets and feeding regimes on selected biological variables and water quality were followed by weekly observations and measurements. Results in terms of growth (=increase in length), cyst production, and mortality were more successful when animals were supplied high densities of YM20 than in all other treatments: mean brood size was 155±6 cysts with a maximum of 266. Length after 6 weeks about 2 cm while this ranged between1.4–1.7 cm for the other treatments. Weekly mortality rate was comparable under high food conditions. Mortality rate gradually increased from 5% in the first week to 15% in the last week. Water quality, especially nitriate concentration (measured as NO₂-N), was slightly better in the dry food fed than in the algae fed cultures. Present results are promising for large-scale culturing ofS. proboscideus in a cost-effective way by making use of agro-industrial waste products.     

Synchronization of encystment of <Emphasis Type="BoldItalic">Scrippsiella lachrymosa</Emphasis> (Dinophyta)

The encystment of Scrippsiella lachrymosa cells (strain B-10), which can be induced reliably in encystment medium, was inhibited by stirring the culture. 100 mL cultures in glass beakers were stirred at 1 rotation s⁻¹. Stirring inhibited vegetative cells from congregating (swarming) at the walls of the culture container. When stirring was stopped, a rapid induction of sexual reproduction was seen. As soon as stirring stopped (within 2 min), cells were observed swarming near the edges of the glass beaker. Four days after cessation of stirring, large percentages of the cells were mating and, after 7 days, most were zygotes. Cultures were observed after 31, 38, and, 45 days of stirring. When cultures were stirred for 45 days, cysts developed in the stirred treatments, but these cysts were attached to flocculent material that had also formed in the medium. The use of this laboratory method is advantageous for the study of the mating through cyst stages of the dinoflagellate life history. This method may also demonstrate the need for a ‘surface’ as a place for the dinoflagellate to congregate in order to successfully encyst and may help explain environmental observations of encystment at pycnoclines.     

EVIDENCE FOR ASEXUAL RESTING CYSTS IN THE LIFE CYCLE OF THE MARINE PERIDINOID DINOFLAGELLATE,SCRIPPSIELLA HANGOEI1

Scrippsiella hangoei (Schiller) Larsen is a peridinoid dinoflagellate that grows during winter and spring in the Baltic Sea. In culture this species formed round, smooth cysts when strains were mixed, indicating heterothallic sexuality and hypnozygote production. However, cysts of the same morphology were also formed in clonal strains exposed to slightly elevated temperature. To better understand the role of cysts in the life cycle of S. hangoei, cyst formation and dormancy were examined in culture experiments and the cellular DNA content of flagellate cells and cysts was compared in clonal and mixed strains using flow cytometry. S. hangoei exhibited a high rate of cyst formation in culture. Cysts produced in both clonal and mixed strain cultures were thick‐walled and underwent a dormancy period of 4 months before germinating. The S. hangoei flagellate cell population DNA distributions consisted of 1C, intermediate, and 2C DNA, indicative of respective eukaryotic cell cycle phases G1, S, and G2M. The majority (>95%) of cysts had a measured DNA content equivalent to the lower 1C DNA value, indicating a haploid nuclear phase and an asexual mode of cyst formation. A small percentage (<5%) of cysts produced in the mixed strain culture had 2C DNA, and thus could have been diploid zygotes. These findings represent the first measurements of dinoflagellate resting cyst DNA content, and provide the first quantitative evidence for dinoflagellate asexual resting cysts. Asexual resting cysts may be a more common feature of dinoflagellate life cycles than previously thought.     

Penetration,Development, and Reproduction of Heterodera schachtii on Fagopyrum esculentum,Phacelia tanacetifolia,Raphanus sativus,Sinapis alba,and Brassica oleracea

The penetration, development, and reproduction of a California population of the sugarbeet cyst nematode, Heterodera schachtii, was observed on cultivars of cabbage (Brassica oleracea), phacelia (Phacelia tanacetifolia), buckwheat (Fagopyrum esculentum), oilseed radish (Raphanus sativus), and white mustard (Sinapis alba). With the exception of the nonhost, phacelia, all were readily penetrated by second-stage juveniles of H. schachtii. After 38 days at 25 C, no cysts were observed on phacelia cv. Angelia or on the oilseed radish cv. Nemex and Pegletta. Cyst production was low (<2.5 cysts/plant) on the buckwheat cv. Tardo and Prego and most of the oilseed radish cultivars. Cyst production was intermediate (5-14 cysts/plant) on most of the white mustard cultivars, and high on cabbage (20-110 cysts/plant). In microplot studies conducted over 133 days (approx. 450 degree-days, base 8 C), the reproductive index for H. schachtii was greater than 1.0 for cultivars of phacelia, oilseed radish, and white mustard as welt as in fallow treatments, indicating the need for further research on the use of these crops under field conditions.     

Effect of growth on reproduction in the freshwater amphipod, Hyalella azteca (Saussure)

A gradient in H. azteca growth was created by reducing food ration. Tests were initiated with neonates (48 h old) and the effects of an altered food ration on survival and growth were examined after 10 and 49 days. Growth rates decreased significantly with reduced food ration (10 day growth rates ranged from 1.2 µg d^–1 in the highest feeding regime to 0.5 µg d^–1 in lowest feeding regime). Survival after 10 days was not affected by ration, ranging from 86 to 96%. A growth rate of 1.2 µg d^–1 at day 10 resulted in mean dry weight (1.0 mg), survival (62%) and reproduction (9.3 neonates/female) at day 49 similar to reported values for this species. Growth rates 0.9 µg d^–1 at day 10 corresponded to significantly reduced reproduction at day 49 (i.e., < 1 neonate per female). Time to the onset of amplexus increased with decreasing ration suggesting reduced ration may have delayed reproduction.     

Late breeding season definitive prebasic molt in males,and late breeding season brood care by females,in central California Wilson’s warblers

I made observations of a central California population of Wilson''s Warbler, Cardellina pusilla, after July 1 over 10 breeding seasons. I sighted males in definitive prebasic molt from July 4 (in 2007) to September 1 (in 1999). Most territorial males molted on their breeding territories, and individual molt lasted up to 46 days. Following prebasic molt, territorial males engaged in subdued “post‐molt singing,” which lasted about 7 days in some males, and which I first heard on August 13 (in 2004) and last heard on September 6 (in 1999). I sighted no female in definitive prebasic molt, or in fresh basic plumage, during the study. Of 13 females sighted ≥ July 21, 11 were in late breeding season uniparental brood care, and I could not rule out late brood care for the other two. Most, and possibly all, females not engaged in late season uniparental brood care apparently vacated their breeding territories before July 21. This departure was much earlier than for resident males, the last of which I sighted on September 10 (in 1999). Early‐departing females presumably underwent prebasic molt after July 21 at locations not known. Remaining late‐nesting females must have molted much later than resident males and likely later than early‐departing females, and at locations unknown. I last sighted two uniparental brood‐tending females, still in worn plumage, on August 26 and 29, respectively. Two unique findings of this study are a male/female difference in location of prebasic molt, and a likely dichotomy of prebasic molt timing between females leaving their breeding territories early and those remaining in uniparental brood care. Another finding, post‐molt singing in most and possible all territorial males, is a largely unrecognized behavior, but one previously reported in several passerine species. Post‐molt singing may reliably indicate completion of prebasic molt.     

Extraction of Cysts and Eggs of Heterodera schachtii from Soil with an Assessment of Extraction Efficiency

Techniques are described for the extraction and enumeration of cysts and contained eggs from soil samples. The average recovery of cysts from seeded soil samples of differing soil texture was 82.7 ± 2.1%. Recovery from sandy clay soil samples seeded at 1 cyst/100 g soil was 63.4 ± 5.5%; at 4.2 cysts/100 g soil recovery was 89.6 ± 1.8%. Recovery of cysts from naturally infested clay soil was 88.3 ± 2.05%. Egg extraction efficiency for seeded samples was calculated as 78%, and for naturally infested soil was estimated as 83%.     

Effects of feeding frequency and sugar concentrations on lifetime reproductive success of Meteorus pulchricornis (Hymenoptera: Braconidae)

Many species of parasitoids can increase their reproduction through feeding on supplemental sugar sources. We evaluated the longevity both with and without hosts and progeny production of a uniparental strain of Meteorus pulchricornis by varying concentration of the sugar solution and feeding frequency. A 1:1:1 sucrose–glucose–fructose-mixture was tested in a range of concentrations (0–70% (w/v)). The parasitoid lifespan did not increase with the concentration of sugar solutions, but parasitoids feeding on a 30% sugar solution attained greater longevity than parasitoids feeding on other sugar concentrations in the absence of hosts. The same effect of sugar concentration was also observed on progeny production, where when the parasitoid was fed 30% (w/v) sugar solution, its lifetime progeny production doubled in comparison to that fed water, and increased by 50% compared to those fed the other sugar solutions. In the last experiment, we studied the effect of feeding intervals on the longevity and progeny production of M. pulchricornis. Parasitoids fed with a 30% (w/v) 1:1:1 sucrose–glucose–fructose-mixture continuously lived six times longer than unfed parasitoids, three times longer than parasitoids fed only once and two times longer than parasitoids fed once every two days in the absence of hosts. Parasitoids with continuous access to the sugar solution produced considerably more progeny than those with fewer feeding frequencies. This increasing progeny production was accomplished more through an increase in daily offspring production rather than through extending reproductive lifespan.     

Dinoflagellate cyst production in one-liter containers

Methods for the production of dinoflagellate cysts in two types of 1 L containers have been developed. Using these methods, dinoflagellate cysts can be produced in amounts large enough for shellfish grazing experiments or whenever large amounts of cysts are needed. The species used were Scrippsiella lachrymosa (B-10) and toxic Alexandrium fundyense (CB501 and GTM25). Cultures of S. lachrymosa yielded 628 ± 74 cysts mL^–1 and A. fundyense cultures yielded 350 ± 98 cysts mL^–1. Findings suggest that aspects of the boundary layer between the media and the wall of the container are important for gamete mating; especially, the slope of the container wall appears to be relevant, which offers some explanation of previous observations that the shape of the container is important in the formation of dinoflagellate resting cysts. These observations may support the theory that physical interfaces in nature facilitate dinoflagellate encystment.     

Influence of light,DMSO and glycerol on the hatchability ofThamnocephalus platyurus Packard cysts

Effects of two light intensities and different concentration of dimethyl sulfoxide (DMSO) and glycerol on hydrated cyst hatching inThamnocephalus platyurus were studied. A maximum of 65±6% hatching was recorded within seven days at 2500 lux continuous light regime. Hatching was at a minimum during the first two days, peaked between the third and fourth days, decreased thereafter. Hatching success was a function of duration of light exposure. Eight percent of cysts hatched in the dark, while cysts exposed to 24h light and subsequently incubated in the dark showed 27±2% hatching. Hatchability was significantly increased (23%) in 0.0375% DMSO and 0.0125% glycerol. Concentration above 0.05% DMSO and 0.025% glycerol had no or a negative influence on hatching. Since low concentrations of DMSO were non-toxic, apolar compounds like Ca²⁺ ionophore can be dissolved in DMSO to study the role of Calcium in cyst hatching.     

The use of Artemia biomass sampling to predict cyst yields in culture ponds

The possibility of using biomass volume (= mean biomass present in the pond.week ^–1) to predict the total amount of harvestable cysts (= kg wet weight collected. week ^–1) produced in a culture pond by an Artemia franciscana population using a mixed model regression was evaluated for two different sampling methods; horizontal transects and vertical point samples. For transects, the following equation was found: `log (0.01 + cyst yields) = –2.05 + 0.025<sup>*</sup>(biomass volume)' with F <sub>(1, 4.87)</sub> = 8.83 and p = 0.032. For the point samples, the regression was also significant with F <sub>(1, 55.2)</sub> = 13.62 and p = 0.0005 for following equation: `log (0.01 + cyst yield) = –3.613 + 0.021^*(biomass volume). As pond effect and interaction terms did not significantly explain a significant portion of the variance for either of the sampling methods (Transects: pond: F _{(3, 14.3)} = 2.48; p = 0.103; pond^*biomass volume: F _{(3, 3.61)} = 4.63; p = 0.0976; Point samples: pond: F _{(3, 44.5)} = 0.00; p = 0.999; pond^*biomass volume: F _{(3, 44.2)} = 0.11; p = 0.954 ), the variable pond (repeated measurement factor) was not included in the final calculations for the regression equations. Although a combination of factors influences the equation, the high significance levels of the regression indicate biomass volume can be safely used to predict production trends. The low investment requirements of this method make it especially attractive for on farm use, where correctly determining the point of cyst decline will help farmers to allocate resources where needed.     

The significance of sexual versus asexual cyst formation in the life cycle of the noxious dinoflagellate Alexandrium peruvianum

Alexandrium peruvianum (Balech et Mendiola) is a noxious phototrophic marine dinoflagellate. During the life cycle of this species, two kinds of cysts are produced: resting cysts, which are long-lasting and double-walled, and temporary cysts, which are short-lasting and thin-walled. In addition, short-lasting, but resting-like cysts can also be formed. Although it is crucial to identify sexual events in a dinoflagellate population, sexual and asexual cysts are morphologically very similar in this species. Therefore, we studied the complete life cycle and the nature of the cyst-like stages formed after individual isolation of specimens and crossing of clonal cultures established from germination of wild resting cysts. Asexual division in A. peruvianum takes place either in the motile stage by sharing of the theca (desmoschisis), or inside a vegetative cyst (temporary cyst), from which two, or at times four or six naked daughter cells can originate. The daughter cells completely synthesize new cell walls (eleutheroschisis). Sexuality was confirmed by the presence of fusing gamete pairs and longitudinally biflagellated planozygotes after out-crossing of compatible clonal strains. However, the clonal cultures had low levels of self-compatibility, since a flow cytometry analysis showed that synchronized self-crosses produced few zygotes (<5%). After isolation of individual cells, it was proved that the fate of the planozygotes depended on the nutritional status of the isolation media. Most of the planozygotes isolated to replete medium (L1) divided, whereas in medium lacking nitrates (L-N) or phosphates (L-P) they formed temporary, thin-walled cysts. Temporary cysts formed in L1 were always uninucleated and gave rise to one cell, while those formed in L-N or L-P produced 1–6 small cells. In addition, resting cysts were formed in culture, but never after individual planozygote isolation. Resting cysts were uninucleated and needed maturation time before entering dormancy. The resting cysts were considered sexual products, since longitudinally biflagellate germlings were liberated after germination in all cases studied. Mature resting cysts (52.3 ± 3.0 μm) had a dormancy period of 1–3 months, whereas temporary asexual cysts (32.5 ± 5.4 μm) germinated in less than 7 days.     

Two new species of Eimeria Schneider, 1875 (Apicomplexa: Eimeriidae) from skinks in Florida

Eimeria egregia n. sp. parasitises the gall-bladder of Eumeces egregius onocrepis, the brown red-tailed skink, in the Ocala National Forest, Marion County, Florida. Oöcysts are oval, 27.6 × 17.4 µm (25–32 × 16–20), without micropyle, polar body or oöcyst residuum. The oöcyst length/width ratio is 1.59 (1.42–1.76). Sporocysts are ovoid, 10.3 × 8.3 µm (8.5–12 × 7–9 µm), with a length/width ratio of 1.24 (1.06–1.50,), without a Stieda body, but with a prominent sporocyst residuum. Sporozoites are 10–12 × 2.5–3 µm. The ground skink Scincella lateralis is infected by Eimeria scincellae n. sp. The oöcysts are cylindrical, 29.8 × 15.9 µm (28–33 × 14–17), with no micropyle, polar body or oöcyst residuum. The oöcyst length/width ratio is 1.89 (1.68–2.14). Sporocysts are oval, 10.9 × 8.0 µm (9.5–12 × 7–9), with a length/width ratio of 1.36 (1.18–1.64,), no Stieda body and a prominent sporocyst residuum. Sporozoites are 9–11 × 2–2.5 µm.     

Giardia cysts and Cryptosporidium oocysts detection in the intake and rapid filter system in a water purification plant

Water samples, taken from the intake and rapid filter system of a water purification plant, were analyzed using an immunofluorescence antibody method for detecting the presence of Giardia cysts and Cryptosporidium oocysts. Giardia cysts and Cryptosporidium oocysts were found in the intake water from zero to 38.7 cysts/100 l and 1.7–50.5 oocysts/100 l with averages of 9.6 cysts/100 l and 19.4 oocysts/100 l. Giardia cysts and Cryptosporidium oocysts were also detected in the samples taken from the rapid filtration unit with mean concentrations of zero to 2.3 cysts/100 l and 0–2.5 oocysts/100 l, respectively. The efficacy of the rapid filter in suspended material and (oo)cyst removal was significant. The removal late was 56–97% for suspended material and 69–100% for the (oo)cysts.     

Evidence for Production of Sexual Resting Cysts by the Toxic Dinoflagellate Karenia mikimotoi in Clonal Cultures and Marine Sediments

The toxic dinoflagellate Karenia mikimotoi has been well-known for causing large-scale and dense harmful algal blooms (HABs) in coastal waters worldwide and serious economic loss in aquaculture and fisheries and other adverse effects on marine ecosystems. Whether K. mikimotoi forms resting cysts has been a puzzling issue regarding to the mechanisms of bloom initiation and geographic expansion of this species. We provide morphological and molecular confirmation of sexually produced thin-walled resting cysts by K. mikimotoi based on observations of laboratory cultures and their direct detection in marine sediments. Light and scanning electron microscopy evidences for sexual reproduction include attraction and pairing of gametes, gamete fusion, formation of planozygote and thin-walled cyst, and the documentation of the thin-walled cyst germination processes. Evidence for cysts in marine sediments was in three aspects: positive PCR detection of cysts using species-specific primers in the DNA extracted from whole sediments; fluorescence in situ hybridization detection of cysts using FISH probes; and single-cell PCR sequencing for cysts positively labeled with FISH probes. The existence of sexually produced, thin-walled resting cysts by K. mikimotoi provides a possible mechanism accounting for the initiation of annually recurring blooms at certain regions and global expansion of the species during the past decades.     

Identification of the resting cyst of Cochlodinium polykrikoides Margalef (Dinophyceae,Gymnodiniales) in Korean coastal sediments

This study provides the first morphological features of resting cysts of Cochlodinium polykrikoides collected from Korean coastal sediments. Evidence for the existence of resting cysts of C. polykrikoides is based on the morphological and molecular phylogenetic data of the germinated cells and a resting cyst. The morphology of the resting cysts differed from that reported previously in sediments and culture experiments. The distinct feature is that the cyst body was covered by the reticulate ornaments and spines.     

Salinity tolerance of the copepod Apocyclops dengizicus (Lepeschkin, 1900), a key food chain organism in the Salton Sea,California

The copepod Apocyclops dengizicus is a key item in the food chain of the Salton Sea where the salinity is currently 45 g 1^–1. The salinity of the Salton Sea may reach 90 g 1 ^–1 within the next 20 years. This study examined the salinity tolerance of this copepod.Large copepodite and adult A. dengizicus were introduced into various salinities with and without acclimation. The 96 h LC₅₀ without acclimation was 101 g 1^–1. Mortality (at 96 h) without acclimation was low at salinities of 90 g 1 ^–1 or less.Copepod cultures were maintained, with successful reproduction of at least one new generation, at salinities of from 0.5 to 68 g 1 ^–1 for at least 120 days. Copepods maintained at higher salinities, up to 79 g 1 ^–1, remained alive up to 90 days, but a new generation was not produced. In laboratory studies of larval production and survivorship, few nauplii were released at salinities of 68 g 1 ^–1 or higher, and none survived to the copepodite stage.