Eix Z
Taula 5.10: Taula de resum del càlcul de forces dels eixos per pes. Font: Pròpia
The results presented in section 3.3 are the first report o f TAMs being released in fecal packets. The most likely reason fecal packets were not observed in previous studies o f TAM release by T. tubifex (Markiw, 1986; El-Matbouli et al.. 1999; Stevens et al..
2001) lies in the experimental design o f those studies. As mentioned previously, those studies examined TAM production by groups o f worms, not individual T. tubifex. In those studies. TAMs were detected and quantified by removing either all o f the water or an aliquot o f the water from the container in which the worms were kept. The fecal packets observed in the present study were on the bottom o f the tissue culture wells and did not float (Fig. 17). Therefore, it is unlikely that these researchers would have observed these packets by simply examining the contents o f the water column above the worms. The fecal packets were discovered in the present study only because each well, and the enclosed worm, were examined under a dissecting microscope on a daily basis.
In addition, the worms in the previous studies were maintained in some type o f substrate, either mud (Markiw, 1986) or sand (El-Matbouli et al., 1999 and Stevens et al. 2001).
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The fact that T. tubifex often burrow completely beneath any provided substrate would have further reduced the likelihood o f observing fecal packets. Anecdotally, it has been suggested that these fecal packets are a laboratory artifacts and that they are the result o f the increase in temperature that is experienced by the worms when they are removed from an incubator for screening. Therefore the experiments described in section 3.5 were performed. Based on the results o f these experiments, it seems highly unlikely that the release o f M. cerebralis TAMs in fecal packets is the result o f temperature shock. First.
these results have shown that both naturally and experimentally infected T. tubifex kept at constant temperature, as well as those experiencing mild temperature changes o f 7 - 14°C (such as that experienced by T. tubifex in the Rock Creek drainage in late spring and early summer), released TAMs contained in fecal packets (Figs. 17 and 18). In fact, T. tubifex subjected to extreme temperature shock o f more than 20°C rarely released TAM S in fecal packets (Table 16), similar observations were reported by El-matbouli et al. (1999).
Second, in all o f the observations o f TAM release by both experimentally and naturally infected T. tubifex (which includes over 1000 observations o f over 500 different infected worms), TAMs were virtually always released in fecal packets (i.e. either a fecal packet containing the TAMs or the remnants o f a fecal packet and waterborne TAMs were observed concurrently). On several occasions infected T. tubifex were observed and even photographed while in the process o f defecating and no TAMs were observed entering the water column but were instead completely contained within the fecal packet (Fig. 17).
Finally, in the study by El-Matbouli et al. (1999), an increase in temperature that resulted from an incubator door being left open was cited as the cause o f a massive increase in the number o f waterborne TAMs released by worms intended to be held at 5 °C. Thus, if the
anecdotal suggestion mentioned above was true (i.e. that fecal packets result from temperature shock), this temperature increase should have resulted in those TAMs being released in fecal packets. This, in turn, should have resulted in a decrease in the number o f waterborne TA M s observed, not the increase that was reported.
At no time during observations o f TAM release by T. tubifex, were TAMs observed being egested, and infected T. tubifex that died during the course o f these studies described were examined using microscopy, and even crushed between
microscope slides, but very few if any TAMs were observed. Therefore, the release of M. cerebralis TAM s via egestion or after the death o f the worm, as was previously suggested (El-Matbouli et al., 1992) is not likely. It is likely that in natural settings M.
cerebralis TAMs are released from infected T. tubifex contained within fecal packets. If this is indeed the case, it should not be surprising as countless other intestinal parasites are released from their hosts in the feces. The feces from uninfected worms, although often smaller, are quite similar in appearance to the feces o f infected worms, which contain the TAMs (Fig. 18). In fact, in an unrelated study, the feces o f T. tubifex were described as a fecal pellet (Appleby and Brinkhurst, 1971). a term not unlike fecal packet used here, which was derived prior to knowledge o f that report. The natural mechanism by which the TAM s escape from these fecal packets is still unknown. The deflated and folded appearance o f the TAMs contained in fecal packets and their expansion that occurs after the packet ruptures was described earlier. A similar description was given by El-Matbouli and Hoffmann (1998) after observing TAMs that were released from an infected T. tubifex when it was crushed between 2 microscope slides. When the TAM processes begin to expand and unfold, the influx o f water is quite rapid, suggesting the
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TAMs have a high osmotic potential. Thus, it seems possible that TAMs could begin absorbing water while still confined within the fecal packet, and that the force exerted by this osmotic expansion may cause the packet to rupture. However, fecal packets could not be induced to rupture by placing them in deionized water. Fecal packets have also been stored at 10°C for 2 weeks but did not rupture and no TAMs were released. A microscopic examination o f the packets after this time revealed that the TAMs had virtually disintegrated. This suggests that release o f the TAMs from the fecal packets is not a passive process that occurs naturally over time. The fecal packets observed during this study were often tom or punctured by the hair chaetae o f the T. tubifex before being removed from the well o f the tissue culture dish and these punctures and tears were sufficient to cause the release of a significant number o f TAMs. Therefore, it is certainly possibly that under natural conditions TAM s are released from these packets by a
mechanical process. For example, the packet may be ruptured or tom during defecation due to the relatively sharp edges of the sedim ent particles in the feces, or the fact that the feces may be dragged through the sediments during defecation due to the burrowing activity o f the worm. It is also possible that TAMs are released from fecal packets by the feeding activity o f other worms. As mentioned in the introduction, T. tubifex are often found in close association with other oligochaete species such as L. hoffmeisteri and these characteristic associations are believed to be due to mutualistic relationships in which one species feeds on the bacteria associated with the fecal pellets o f the other species and vice versa (Brinkhurst. 1971; Brinkhurst 1974; Milbrink, 1993). Thus, it is possible that other species o f oligochaetes actively seek out and feed on the feces of T. tubifex thereby helping the TAMs to escape. The mechanism by which TAMs escape from these fecal
packets and the possible influence o f these packets on the epidemiology o f whirling disease remain areas o f ongoing investigation.
4.6 General Conclusions
Overall the results from this study have shown that the severity AL
cerebralis infections in sentinel trout increased significantly at sites throughout the Rock Creek Drainage between June o f 1998 and June o f 2000. and that the range o f AL
cerebralis within this drainage may still be expanding (Fig. 18). However, the reasons for this expansion remain unclear. In addition, the effect the parasite is having on wild salmonid populations in Rock Creek remains unknown, as population surveys have not been conducted in this drainage since Al. cerebralis was discovered here in 1997.
There was not a significant increase in the prevalence o f M cerebralis infections in T. tubifex populations in this drainage over the course o f this study, but this may have been due to the relatively small number o f T. tubifex that were screened. Interestingly, the prevalence o f AL cerebralis infection in Tubifex populations observed during this study were similar to those seen in T. tubifex populations from the upper Colorado River basin, but much higher than that reported for a population o f worms from W est Virginia.
This study has also shown that T. tubifex that are resistant to infection with AL cerebralis are present in the Rock Creek drainage, and both living specimens, and DNA samples from these worms have been made available to other investigators involved in genetic studies o f T. tubifex. In addition, the extensive am ount o f information about the East Fork o f Rock Creek that was collected during this study, will serve as a comparative data set to determine the effects o f habitat restoration on the transmission o f whirling disease.
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as an extensive habitat restoration project is scheduled to begin on this tributary in the summer o f 2002.
Results from this study have also shown that T. tubifex infected with M.
cerebralis remain infected for the duration o f their natural lifespan and that they are capable o f releasing viable TAMs, in temporally separate periods, nearly 2 yr after exposure to M. cerebralis myxospores. These findings are significant in that they open the possibility o f a seasonal periodicity in TAM release. Although only limited support for a seasonal periodicity in TAM release was obtained using the chambers designed as part o f this study, these experiments helped identify problems likely to be faced by other researchers attempting to quantify M. cerebralis TAM s (e.g., the existence o f other myxozoan species that use T. tubifex as a host and have actinosporean stages that cannot be easily distinguished from M cerebralis based on morphology) and illustrates the necessity o f using molecular techniques to confirm the identity o f these parasites.
Finally, this is the first report of TAMs being released in fecal packets. A t no time during this study did we observe TAMs being egested by infected T. tubifex or TAMs being released after the death o f an infected worm, as were previously suggested as a possible mechanisms of TAM release (El-Matbouli et al.. 1992). It is likely that these fecal packets are the natural way in which TAM s are released from T. tubifex.
which should not be surprising, as numerous other species intestinal parasites are released from their hosts in the feces.
Due to the relatively recent discovery o f the two-host life cycle o f M. cerebralis.
it is not surprising that there are gaps in information pertaining to the oligochaete host.
Although it is apparent that T. tubifex is the only suitable worm host, there is solid
evidence that its ability to transmit M. cerebralis varies considerably, and depends on individual, population and epidemiological characteristics. Persistently infected T.
tubifex, seasonal release o f TAMs, and geographic, genetic and habitat differences all likely contribute to determining the severity o f whirling disease within an ecosystem.
Although much remains to be learned, if the results o f recent studies are any indication, a much clearer picture of the role o f T. tubifex in the transmission M. cerebralis will be emerging in the near future.
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Appendix A. 1. Readings of standard water quality parameters taken at sites in the Rock Creek drainage in July o f 1998.
* Instruments used to take these readings were not available at the time o f this sampling.
DO Dissolved oxygen in milligrams per liter.
% Sat. Percent saturation o f O2 in water at the temperature listed.
TDS Total dissolved solutes in milligrams per liter.
nt Readings not taken.
nd Sampling not done.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Appendix A. 1.Readings of standard water quality parameters taken at sites in the Rock Creek drainage in July of 1998. Site#Site NameDateTimeTemp. (°C)pnDO mg/L (% Sat.)*Conductivity pS/cm*TDSmg/L* 1Upper Middle Forkndndndndnt nlnt 2Lower Middle Forktillndndndnl nlnt 3Upper East Fork7/9/9810:10am10.28.07nt nlnl 4Lower East Forkndndndndnl nlill 5Ross Fork7/9/9811:10am12.77.6nt ntnt 6West Fork7/9/9810:30am11.67.51nt nlnt 7Forks Bridgendndndndnl ntnt 8Watson’s Bridgelidndndndnt ntnt 0Bohrnsen’s Bridgendndndndnt ntnt 10Gillie’s Bridgendndndndnt ntnt IIUpper Willow Creek7/9/9811:40am13.27.56nt ntnl 12Stony Creek7/9/9812:16pm10.17.97ntntnt 13Windlass Bridgendndndndnt ntnt 14Upper Puyear Ranchndndndndnt ntiu 15Middle Puyear Ranchndndndndnt ntnt 16Lower Puyear Ranchndndndndnt ntnt 17Hogback Creekndndndndnt ntnt 18Cantp Siria7/9/981:55pm13.98.23nt ntnt 19Fish & Game7/9/983:00pm14.88.44nt ntnt 20Valley of the Moon7/9/983:45pm16.48.35nt ntnt 21Above Hogback Creekndndndndnt ntnt 22Ranch Creekndndndndnt ntnt 23Middle East Forkndndndndlit ntnt 24Clark’s Propertyndndndndnl ntnt 25Mouth of Hogback Creekndndndndnt ntnt
Appendix A.2. Readings o f standard water quality parameters taken at sites in the Rock Creek drainage in June o f 1999.
DO Dissolved oxygen in milligrams per liter.
% Sat. Percent saturation o f O2 in water at the temperature listed.
TDS Total dissolved solutes in milligrams per liter, nt Readings not taken,
nd Sampling not done.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Appendix A.2. Readings of standard water quality parameters taken at sites in the Rock Creek drainage in June of 1999. Site NameDateTimeTemp. (°C)piiDO mg/L (% Sat.)Conductivity pS/cmTDSmg/L Upper Middle Forkndndndndndndnt Lower Middle Forkndndndndndndnt Upper East Fork6/22/998:20am8.08.029.13(75.4)236.0106.0 Lower East Forkndndndndndndnt Ross Forkndndndndndndnt West Fork6/22/998:00am8.57.699.58(82.0)ndnt Forks Bridgendndndndndndnt Watson’s Bridgendndndndndndnt Bohrnsen’s Bridgendndndndndndnt Gillie’s Bridgendndndndndndnl Upper Willow Creek6/21/993:30pm14.67.548.11(81.0)110.050.4 Stony Creek6/21/992:40pm8.66.710.06 (83.3)20.58.5 Windlass Bridgendndndndndndnt Upper Puyear Ranchndndndndndndnt Middle Puyear Ranchndndndndndndnl Lower Puyear Ranchndndndndndndnl 1 logback Creek6/21/9912:15pm7.57.959.96(83.3)42.821.5 Camp Siria6/21/9911:30am10.17.849.56(nd)79.538.9 Fish & Game6/21/9910:00am9.87.819.85(86.5)70.835.4 Valley of the Moon6/21/999:20am11.57.939.88(87.5)82.138.4 Above Hogback Creek6/21/9912:30pm10.07.919.09(80.7)66.432.6 Ranch Creekndndndndndndnl Middle East Forkndndndndndndnt Clark’s Propertyndndndndndndnt Mouth of Hogback Creekndndndndndndnt
Appendix A.3. Readings o f standard water quality parameters taken at sites in the Rock Creek drainage in June o f 2000.
DO Dissolved oxygen in milligrams per liter.
% Sat. Percent saturation o f O2 in water at the temperature listed.
TDS Total dissolved solutes in milligrams per liter, nd Sampling not done.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Appendix A.3. Readings of standard water quality parameters taken at sites in the Rock Creek drainage in June of 2000. Site #Site NameDateTimeTemp. (°C)pllDO mg/L (% Sat.)Conductivity pS/cmTDSmg/L 1Upper Middle Fork6/19/0011:15am7.58.5910.19(84.7)104.452.4 2Lower Middle Fork6/19/0011:45 am9.48.610.84 (94.8)110.054.9 3Upper F.ast Fork6/19/0010:40am9.58.315.3(51.0)278.0167.0 4Lower Fast Fork6/19/0012:30pm10.68.7710.71 (96.0)134.469.5 5Ross Fork6/19/0012:50pm12.38.210.25(95.6)40.220.9 6West Fork6/19/001:00pm13.28.269.17(88.7)29.514.9 7Forks Bridge6/19/0012:40pm128.479.21(86.6)62.831.3 8Watson’s Bridge6/19/001:25pm12.58.6310.10(94.6)90.845.4 0Bohrnsen’s Bridge6/19/001:40pm12.88.499.90(93.4)128.564.2 10Gillie’s Bridge6/19/002:15pm12.38.419.68(90.9)137.068.6 11Upper Willow Creek6/19/002:05pm15.18.079.27(92.3)84.142.0 12Stony Creek6/19/003:00pm9.88.410.84 (95.1)85.444.5 13Windlass Bridge6/19/003:10pm13.18.2910.28 (97.9)136.568.5 14Upper Puyear Ranch6/19/005:00pm15.58.559.77(97.5)152.676.5 15Middle Puyear Ranch6/19/004:00pm14.88.429.75 (95.2)139.070.3 16Lower Puyear Ranch6/19/004:20pm14.78.4810.23(100)137.970.5 17Hogback Creek6/19/005:15pm98.5710.22(89.0)62.132.5 18Camp Siria6/19/005:35 pm14.78.539.95(98.6)141.070.6 19Fish & Game6/19/006:50pm12.58.2310.29 (96.6)114.458.4 20Valley of the Moon6/19/007:50pm13.78.29.80(94.2)122.961.6 21Above Hogback Creeknilndndndndndnd 22Ranch Creekndndndndndndnd 23Middle East Forkndndndndndndnd 24Clark’s Propertyndndndndndndnd 25Mouth of Hogback Creekndndndndndndnil
Appendix A.4. Readings o f standard water quality parameters taken at sites in the Rock Creek drainage in June o f 2001.
DO Dissolved oxygen in milligrams per liter.
% Sat. Percent saturation o f O? in water at the temperature listed.
TDS Total dissolved solutes in milligrams per liter, nd Sampling not done.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
Appendix A.4. Readings of standard water quality parameters taken at sites in the Rock Creek drainage in June of 2001. Site#Site NameDateTimeTemp. (°C)pHDO mg/L (% Sat.)Conductivity pS/cmTDSmg/L 1Upper Middle Forknlnininlnlnlm 2Lower Middle Forkinmntntnintm 3Upper East Fork6/23/012:15pm11.27.996.12(55.1)270163.1 4Lower East Forkminmnimninl 5Ross Fork6/23/01150pm12.48.2210.17(95.1)38.920.1 6West Fork6/23/011:40pm12.98.309.06(86.5)31.515.9 7Forks Bridge6/23/011:30pm12.17.709.17(88.3)61.630.2 8Watson’s Bridge6/23/011:15pm12.87.919.80(91.9)88.843.0 9Bohrnsen's Bridge6/23/0112:20pm12.97.8610.00(94.3)124.562.2 10Gillie’s Bridge6/23/019:50am11.87.679.64 (86.3)131.565.3 11Upper Willow Creek6/23/0110:15am14.97.368.64(85.6)86.545.5 12Stony Creekntinninlntmnt 13Windlass Bridge6/22/017:30pm17.98.107.55 (79.6)134.565.3 14Upper Puyear Ranch6/22/015:30pm18.97.948.04(86.8)149.974.5 15Middle Puyear Ranch6/22/014:40pm18.58.799.00(95.6)13770.6 16Lower Puyear Ranch6/22/014:20pm18.18.889.06(96.6)135.968.5 17Hogback Creekndndndlidndndnd 18Camp Siria6/22/013:45pm18.08.838.69(92.1)139ill 19Fish & Game6/22/013:00pm15.28.859.35 (93.2)113.357.6 20Valley of the Moon6/22/011:30pm18.98.689.00(84.0)121.660.9 21Above Hogback Creeklidlidndndndndnd 22Ranch Creek6/22/012:37pm13.07.908.30(78.2)litnt 23Middle East Fork6/23/012:00pm11.57.978.50(80.2)134.369.7 24Clark’s Property6/23/0111:10am12.67.719.09(85.4)105.554.1 25Mouth of Hogback Creeknilndndndndndnd
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