Effects of current velocity on byssal-thread production in the zebra mussel (Dreissena polymorpha)

1996 ◽  
Vol 74 (1) ◽  
pp. 63-69 ◽  
Author(s):  
Michael Clarke ◽  
Robert F. McMahon
Keyword(s):  
Shell Length ◽  
Current Velocity ◽  
Zebra Mussel ◽  
Dreissena Polymorpha ◽  
Wild Population ◽  
Byssal Thread ◽  
In The Wild ◽  
The Mean ◽  
Experimental Subjects ◽  
Similarities And Differences

The effect of current velocity on byssal-thread production by adult zebra mussels (Dreissena polymorpha) was investigated. The number of threads produced by 20 individuals at currents of 0.10, 0.15, 0.20, 0.27 m/s was recorded daily over 21 consecutive days, after which individual shell length and dry tissue masses were measured and the byssal complex was removed. Increasing the current velocity from 0.10 to 0.20 m/s significantly elevated rates of byssal-thread production, but the rate was reduced at 0.27 m/s. Current-induced suppression of byssal-thread production may be due to mechanical disturbance of attached mussels, interfering with their ability to press the tip of the foot against the substratum as the thread cures. The mean thread number in a newly formed byssal complex after 21 days was 52.5, 63.8, 73.3 and 60.4 at currents of 0.10, 0.15, 0.20 and 0.27 m/s, respectively. Current velocity had no effect on thread width. The mean number of threads found in the byssal complex of individuals from the wild taken from the same population from which experimental subjects were drawn was 148.3/mussel. There was no correlation between thread number and shell length in the wild population. Results indicate that there are both similarities and differences in the response of byssal-thread production to variable current velocity in freshwater dreissenids and marine mytilids.

scholarly journals Evaluating the Sensitivities and Efficacies of Fungicides with Different Modes of Action Against Phomopsis asparagi

Plant Disease ◽  
2020 ◽  
Vol 104 (2) ◽  
pp. 448-454 ◽  
Author(s):  
Niuniu Shi ◽  
Hongchun Ruan ◽  
Lin Gan ◽  
Yuli Dai ◽  
Xiujuan Yang ◽  
...  
Keyword(s):  
Wild Population ◽  
Good Control ◽  
Field Trials ◽  
Growth Inhibition Assay ◽  
Frequency Distributions ◽  
Stem Blight ◽  
Development Of Resistance ◽  
In The Wild ◽  
The Mean ◽  
Phomopsis Asparagi

Asparagus stem blight caused by Phomopsis asparagi is a major hindrance to asparagus production worldwide. Currently, fungicides are used to manage the disease in commercial production, but resistance to common fungicides has emerged in the wild population. In the present study, 132 isolates of P. asparagi collected from different provinces in China were tested for sensitivities to pyraclostrobin, tebuconazole, and fluazinam. We also determined the efficacies of six fungicides against P. asparagi. The frequency distributions of EC50 values of the isolates tested were unimodal, but the curves for pyraclostrobin and tebuconazole had long right-hand tails. The mean EC50 values for pyraclostrobin, tebuconazole, and fluazinam were 0.0426 ± 0.0029, 0.6041 ± 0.0416, and 0.0314 ± 0.0013 μg/ml, respectively. In addition, the EC50 values for pyraclostrobin were very similar with or without salicylhydroxamic acid (SHAM), 20 μg/ml, indicating that SHAM is not needed to determine the sensitivity of P. asparagi to pyraclostrobin when using the mycelial growth inhibition assay. In greenhouse assays, Merivon (42.4% fluxapyroxad plus pyraclostrobin SC), Frown-cide (500 g/liter fluazinam SC), Cabrio (250 g/liter pyraclostrobin EC), and Nativo (75% trifloxystrobin plus tebuconazole WG) showed excellent preventive efficacy against P. asparagi. And these fungicides were more effective before inoculation than when they were applied after inoculation (P < 0.05). Therefore, these fungicides should be applied prior to infection to control stem blight. In field trials, Frown-cide, Merivon, Nativo, and Cabrio also performed good control effects, ranging from 75.2 to 86.0% in 2017 and 75.4 to 87.1% in 2018. We demonstrated that Frown-cide, Merivon, Nativo, and Cabrio had considerable potential to manage asparagus stem blight. In addition, rotations of these fungicides are essential for precluding or delaying the development of resistance and for controlling the disease.

Identification of larvae: the zebra mussel (Dreissena polymorpha), quagga mussel (Dreissena rosteriformis bugensis), and Asian clam (Corbicula fluminea)

1994 ◽  
Vol 72 (3) ◽  
pp. 406-417 ◽  
Author(s):  
S. J. Nichols ◽  
M. G. Black
Keyword(s):  
Shell Length ◽  
Zebra Mussel ◽  
Dreissena Polymorpha ◽  
Corbicula Fluminea ◽  
The United States ◽  
Zebra Mussels ◽  
Shell Size ◽  
Asian Clam ◽  
Clam Corbicula ◽  
Asian Clams

There are presently four freshwater bivalves in the United States that produce larvae or veligers commonly found in the water column: two forms of Asian clams and two species of dreissenids. Portions of the geographic range of three of these bivalves, one species of Asian clam (Corbicula fluminea), zebra mussels (Dreissena polymorpha), and quagga mussels (Dreissena rosteriformis bugensis), overlap, causing problems with larval identification. To determine which characteristics can be used to separate larval forms, adult Asian clams, quaggas, and zebra mussels were brought into the laboratory and induced to spawn, and the resulting larvae were reared. Hybrids between quaggas and zebra mussels were also produced, but not reared to maturity. Characteristics allowing for the most rapid and accurate separation of larvae were hinge length, shell length/height, shell shape, shell size, and the presence or absence of a foot and velum. These characteristics were observed in laboratory-reared larvae of known parentage and field-caught larvae of unknown parentage. In most cases, larvae of the Asian clam can be readily separated from those produced by either type of dreissenid on the basis of shell size and presence of a foot. Separating the gametes and embryos of the two types of dreissenids is not possible, but after shell formation, most of the larval stages can be distinguished. Hinge length, shell length/height, and the similarity in size of the shell valves can be used to separate straight-hinged, umbonal, pediveliger, and plantigrade larvae. Quagga × zebra mussel hybrids show characteristics of both parents and are difficult to identify.

Decline of Native Unionid Bivalves in Lake St. Clair After Infestation by the Zebra Mussel, Dreissena polymorpha

1994 ◽  
Vol 51 (10) ◽  
pp. 2227-2233 ◽  
Author(s):  
Thomas F. Nalepa
Keyword(s):  
Zebra Mussel ◽  
Dreissena Polymorpha ◽  
Extended Period ◽  
Light Weight ◽  
Short Term ◽  
Slow Increase ◽  
The Mean ◽  
The Relationship

To determine impacts of the zebra mussel, Dreissena polymorpha, on bivalves in Lake St. Clair, densities of Unionidae in 1990 and 1992 (after D. polymorpha invasion) were compared with densities in 1986 (before D. polymorpha). Declines in density occurred mainly at sites in the southeastern portion of the lake where unionids were highly infested with D. polymorpha. Unionid densities at highly infested sites declined from 2.4/m2 in 1986, to 1.8/m2 in 1990, and to 0/m2 in 1992. Unionid species with light-weight shells that brood larvae over an extended period declined more between 1986 and 1990 than heavy-shelled, short-term brooders. Unionid densities at lightly infested sites located mainly in the northwestern portion of the lake did not decline: mean densities were 1.4/m2 in 1986, 1.6/m2 in 1990, and 1.4/m2 in 1992. While the mean number of D. polymorpha per unionid was <1 at these lightly infested sites in 1990, it increased to 35 by 1992. Given this relatively slow increase in D. polymorpha per unionid in this portion of the lake, continued monitoring of populations should provide a better understanding of the relationship between the extent of infestations and unionid mortality.

A wall jet to measure the attachment strength of zebra mussels

1995 ◽  
Vol 52 (1) ◽  
pp. 126-135 ◽  
Author(s):  
Josef Daniel Ackerman ◽  
C. Ross Ethier ◽  
Jan K. Spelt ◽  
D. Grant Allen ◽  
Catherine M. Cottrell
Keyword(s):  
Zebra Mussel ◽  
Dreissena Polymorpha ◽  
Zebra Mussels ◽  
Artificial Substrates ◽  
Environmentally Benign ◽  
Wall Jet ◽  
Dreissena Bugensis ◽  
Marine Bivalves ◽  
Attachment Strength ◽  
The Mean

A wall jet is presented as a novel means of measuring the attachment strength of zebra mussels. Attachment strength was inferred from a fluid detachment parameter (DP), defined as the nominal wall shear stress at the detachment site × mussel length2. DP varied significantly on natural and artificial substrates: in tests with 288 Dreissena bugensis (≈8–10 mm long), the mean (±SE) DP was 8.9 ± 0.9 mPa∙m2 on limestone/dolomite, 5.6 ± 0.5 mPa∙m2 on polyvinylchloride, 4.3 ± 0.4 mPa∙m2 on stainless steel, 4.2 ± 0.5 mPa∙m2 on aluminum, and 2.5 ± 0.3 mPa∙m2 on polymethylmethacrylate (Plexiglas). The attachment strength of postlarval mussels (plantigrades; <1 mm) was two orders of magnitude less than adult mussels. These results were validated with conventional tensile loadings, in which 633 Dreissena bugensis and 26 Dreissena polymorpha were pulled off substrates with a calibrated force scale. The tensile loadings results were comparable with those of marine bivalves. Good correlation between pull-off force and DP was observed. Information of this nature is useful for the implementation of environmentally benign zebra mussel controls.

scholarly journals Immunolocalization of Dpfp1, a byssal protein of the zebra mussel Dreissena polymorpha

2000 ◽  
Vol 203 (20) ◽  
pp. 3065-3076 ◽  
Author(s):  
K.E. Anderson ◽  
J.H. Waite
Keyword(s):  
Zebra Mussel ◽  
Dreissena Polymorpha ◽  
Secretory Granules ◽  
Ultrastructural Localization ◽  
Immunohistochemical Localization ◽  
Western Blots ◽  
Byssal Thread ◽  
Glandular Cells ◽  
Thread Formation ◽  
Rigorous Test

The zebra mussel is one of only a few freshwater bivalves known to produce a byssus. This fibrous, proteinaceous and highly cross-linked structure allows the mussel to attach to a variety of substrata and contributes to its notoriety as a major freshwater biofouling species. We have successfully expressed a full-length version of Dreissena polymorpha foot protein 1 (Dpfp1), a putative byssal thread precursor, and have used the recombinant protein as an antigen for polyclonal antibody production. Antisera obtained from rabbits immunized with recombinant Dpfp1 recognize the protein in western blots of extracts from foot tissue and byssal threads. On the basis of this evidence, we conclude that Dpfp1 is a byssal precursor protein manufactured and stored in the foot of the mussel. Immunohistochemical localization of Dpfp1 suggests that the protein is localized in secretory granules in a large gland surrounding the ventral groove of the foot. Only a subset of these glandular cells stockpiles the protein, implying that the zebra mussel foot is a complex organ capable of several distinct secretory activities involved in byssal thread formation. The uniform distribution of Dpfp1-containing cells suggests that the protein is a significant load-bearing component of zebra mussel byssal threads, although a more rigorous test of this hypothesis awaits ultrastructural localization of the protein in mature byssal threads.

Oestradiol-17β in the blood during seasonal reactivation of the diapausing blastocyst in a wild population of tammar wallabies

1982 ◽  
Vol 95 (3) ◽  
pp. 293-300 ◽  
Author(s):  
A. P. F. Flint ◽  
Marilyn B. Renfree
Keyword(s):  
Embryonic Development ◽  
Corpus Luteum ◽  
Wild Population ◽  
Post Partum ◽  
Follicular Maturation ◽  
Peripheral Plasma ◽  
Cardiac Blood ◽  
Transient Rise ◽  
In The Wild ◽  
The Mean

Oestradiol-17β was measured by radioimmunoassay in cardiac blood from 143 pregnant and post-partum tammar wallabies shot in the wild during reactivation of the diapausing blastocyst, embryonic development, birth and post-partum oestrus. A transient rise in circulating oestradiol on 3 January coincided with or shortly preceded corpus luteum growth and blastocyst expansion; before 5 January mean corpus luteum weight was 14·3± 0·44 mg (n = 65), while thereafter it exceeded 20 mg in two-thirds of the animals. Expanded blastocysts were first noted on 5 January. A second rise in the concentration of oestradiol in plasma, which occurred in late January, preceded parturition and coincided with follicular maturation; the mean (± s.e.m.) oestradiol concentration before 17 January was 27·9 ±1·10 pmol/l (n = 110), whereas on or after this date it was 57·3 ± 4·15 pmol/l (n = 33). Thus oestradiol levels in peripheral plasma increased at parturition and post-partum oestrus, and showed a rise early in gestation which may be related to the termination of diapause.

Pumping Rates and Projected Filtering Impacts of Juvenile Zebra Mussels (Dreissena polymorpha) in Western Lake Erie

1993 ◽  
Vol 50 (5) ◽  
pp. 1017-1022 ◽  
Author(s):  
Christopher M. Bunt ◽  
Hugh J. Maclsaac ◽  
W. Gary Sprules
Keyword(s):  
Shell Length ◽  
Zebra Mussel ◽  
Dreissena Polymorpha ◽  
Lake Erie ◽  
Zebra Mussels ◽  
Pumping Rate ◽  
Frequency Distributions ◽  
Western Lake ◽  
Pumping Rates ◽  
Western Lake Erie

Small-bodied (2–11 mm), settled zebra mussels (Dreissena polymorpha Pallas) comprise up to 90% of individuals inhabiting reefs in western Lake Erie. We assessed pumping rates of these size classes of D. polymorpha by injecting an inert dye into inhalant filtering currents and monitoring exhalant flows using high-resolution videography. Pumping rates ranged between 0.20 and 4.45 mL∙ind−1∙h−1 and increased in relation to mussel shell length. Based on 1990 size–frequency distributions for reefs in western Lake Erie and our pumping rate – shell length regression, small settled D. polymorpha were theoretically capable of pumping between 39 and 96% of the water column daily. Small-bodied mussels inhabiting Sunken Chicken Reef were collectively capable of processing between 110 and 400% of the values previously reported for Daphnia. Recent changes in water quality in western Lake Erie could be primarily related to zebra mussel filtering activities, including those of small-bodied individuals.

Co-existence of zebra mussels and freshwater unionids: population dynamics of Leptodea fragilis in a coastal wetland infested with zebra mussels

1999 ◽  
Vol 77 (3) ◽  
pp. 423-432 ◽  
Author(s):  
S Jerrine Nichols ◽  
Jon Amberg
Keyword(s):  
Population Dynamics ◽  
Shell Length ◽  
Zebra Mussel ◽  
Dreissena Polymorpha ◽  
Coastal Wetland ◽  
Zebra Mussels ◽  
Western Basin ◽  
Steady Growth ◽  
Successful Recruitment ◽  
Before And After

In 1996, thousands of live Leptodea fragilis were collected from a marsh located in the western basin of Lake Erie that was infested with zebra mussels (Dreissena polymorpha). Despite the presence of zebra mussels at this site for a number of years, this L. fragilis population showed no signs of competition-induced changes in population dynamics. Biofouling was limited: fewer than 1% of the L. fragilis showed evidence of recent or past zebra mussel colonization. Successful recruitment occurred yearly, with multiple year classes collected that ranged in age from 1 to 12 years. However, age and shell length were not well correlated. Seventy-one percent of the individuals collected were 51-80 mm long, but ranged in age from 2 to 4.5 years. Three different patterns of growth or shell deposition were found. Some individuals grew rapidly, reaching 105 mm in 3.5 years, while others grew only 4.5 mm over the same time period. A few grew poorly during some years but very rapidly in others. Individuals with a shell length of 41 mm or more were sexually mature and females were more common than males. The strong recruitment and steady growth of this population showed no change between the years before and after the zebra mussel invasion, indicating that this marsh is functioning as a natural refugium from potential problems caused by zebra mussels.

Articulatory Behavior Pre and Post Full-Mouth Tooth Extraction and Alveoloplasty

1980 ◽  
Vol 23 (3) ◽  
pp. 630-645 ◽  
Author(s):  
Gerald Zimmermann ◽  
J.A. Scott Kelso ◽  
Larry Lander
Keyword(s):  
Control Subject ◽  
High Speed ◽  
Tooth Extraction ◽  
Kinematic Parameters ◽  
Experimental Conditions ◽  
Mean Values ◽  
Articulatory Movements ◽  
The Mean ◽  
Experimental Subjects ◽  
Normal Speech

High speed cinefluorography was used to track articulatory movements preceding and following full-mouth tooth extraction and alveoloplasty in two subjects. Films also were made of a control subject on two separate days. The purpose of the study was to determine the effects of dramatically altering the structural dimensions of the oral cavity on the kinematic parameters of speech. The results showed that the experimental subjects performed differently pre and postoperatively though the changes were in different directions for the two subjects. Differences in both means and variabilities of kinematic parameters were larger between days for the experimental (operated) subjects than for the control subject. The results for the Control subject also showed significant differences in the mean values of kinematic variables between days though these day-to-day differences could not account for the effects found pre- and postoperatively. The results of the kinematic analysis, particularly the finding that transition time was most stable over the experimental conditions for the operated subjects, are used to speculate about the coordination of normal speech.

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